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Home , Carson Lake, Lahontan Valley, Lake Lahontan

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Lake Lahontan: Geology of Southern , By R. B. MORRISON

GEOLOGICAL SURVEY PROFESSIONAL PAPER 401

A stratigrapAic study of the Cenozoic geology of

part of the hasin of Lahe Lahontan, one of thegreat - late of IWestern United States

SAG N P TJUN1I9CW 4 I

UNITED STATES GOVERNMENT PRINTING OFFICE, :1964 _21111111111111100- -0: I

:_i4}

CONMENTS '

Abtat--rt _, ___ _ _ ,_.t____ _,_,___ __ Quaterusry str itgraphy-CeotinUet 1sgo lntroducdon. ------.---- _-o--- 2 aontan Valley grousp-Contlotied Location _---_ ------. 2 Eetaa formation--Conatnued 30 Fieldwork ._------3 Shore features.------.----- Acknowledgments ...... 4 Tuts. _.______...... 31 Previous work ...... 4 IntraEetza recension...... 31 Geographic setting ...... 4 LAke sand, lot, and clay .------.------33 Major lhndforms ...... 5 Correlation with deposits of Lake LAbontan CarsonDesert and adjoining bsins ...... S described by Russell and Antlef. _-____ 33 Highlands bordering the basins. ... a Paleontology .------33 Climate.------.. 5 Alluvial gravel and oolluvium of Eets a*ge.___ 33 UNITED STATES DEPARTMENT OF THE INTERIOR Wyemasa formation .... ,,.,__. ______34 Vegetation .------.- 7 General features .------__-_-__._____ 34 STEWART L. UOALL, Secretary Economic geography .------.-.-.--- a Correlation with deposits of Tertiary stratigraphy and structure . ,,_ a described by Russell And Anteva . 34 Stratigraphy .. ------9 Eollhn sand. _------,,,___---.... 34 GEOLOGICAL SURVEY Basalt of Rainbowvlountain _-_-_-.-. _ 9 Allusini and colluvini gravel and ssnd .... 3S Dacnteof Rainbow rountsin 10 Interbedded shallow.lake and subaerial 10 Thomas B. Nolan, Director Engles House rbyolite __-_-.- _-_-_ sediments. _ ------36 Truckee formatbo. _ .__------ill Subsurface basin sediments. . 37 BuneJug formatlon . 12 Paleontology.------38 Btructurat features ...... ,._.,._ 15 Basaltic tuff of Upual Hogback.- -___ 3S Tue t.s. ,eoledgetl -ryerLtbrryI ha stologed thIs pobticatl*a 55 fol-o1 : Pre-Truckee faults ...... ------15 Churchill soil .------.--. ---- 38 Faults of post-Truckee and early Bunejug age-- ils General relation and distributiobn. ___ 38 Profile characterittks ....------Structurne features of post-BuneJug pre-Palute age._ 15 40 Baootand-range fault ...... is Schoo formation .----.--..--..._-_-__ 41 General features ...... _ General features .- ..- _-_--_--- 41 Faulting In specific areas...... 16 Members. ------a1 ConfigurA inonof the bedrock floor of the basin... 17 Lowrermember ..------il Morrison, Roger Barron, 1914- Quasternary stratigraphy...... --.*------ilnolite unit .- ._------59 Lake Lnhontan: geology of southern Carson Desert, Ne. Methods of sludy...... Dendritin member ..- __------61 vada. Washington, US. Govt. PrinLt. Off., 1963. Stratigraphik uage.. Upper member ....------62 sonils...... 19 Shure features of &ehooage ------63 ,. 5I p. I1us., mapls dhrn.. tables snd portfolio tfold. maps Definltion and general features ... 19 Shorelines of the early &ehoo lake .- .____ 63 (Iprt col.) dlsgr., tables) 29 M. tUS. GeologiecaSurey. Pro- Boil profiie...... 20 Compsrative heights of highest Eetus snd es'slDnal paper 401) Biliogrsphy: p. 117-121. Classieaton...... _ . 20 early sehoo shorelines at Russlcl Spit.... 64 DescriptIve terminology ...... 21 Lake levels during deposition of the thino- 1. Ceologr-NevadsaChurebill Co. 2. Oeolory, Stratigraphir- Great soi groups ...... 21 lite units.------65 Cenonoic. 1. Tide. l1. TlIe: Carson Desert, Nevada. (Beries) Pre.LAke lAhontan erosional fatures...... 22 Shorelines of the middle Shoo lake; "den- Pre-LAke Lahoatan Quaternary steaigeaphy ...... 23 ttile terrace ...... - . - . 65 Basalt of Ralttlesske lill ...... 231 Shorelines of the late Sehoolake . 65 Pre.lAke lahontan lacustrine sediments...... 23 Indian Lakes formation...... _. __ 6S Palute formation ...... 23 General features . 68 Buried pre-Lake LAhontan Quaternory sedi- Tongues and age units ...... es ments.tl: ...... 24 Alluvium and rolluvium above the CocoonWou .. . . ,,,,,,,,,,,,,,, 24 Lahontan beach.....------68 General featurea and relstions .--- 241 LoAvertongue ...... ------68 Profile oharacterLiees ...... 25 Middle tongue ...... 68 Age. 28 Alluvium of middle Srhoo and Indian Lhontan VaIley group. 28 Lakes age...... 69 EelIs formation. 28 Alluvium, colluuium, and rolian sand General features...... __... 28 of Isle ihoo sad Indian Itke Age._ 71 LWkegravel ...... 28 Voleanicand complex of Sod. L -ake. ... 71 For sale by the Superintendent of l)ocurnents, U.S. Government Printing Odice in WVashington. D.C. 20402 CNEt S coti~~~~~~~~~~~~~mers~~~~~~~~~~~CONTENTS Y

rass Far. Pars Fioute 1. Mlap showing locatios of report areaand aresInundated by lake Lahontn_...... Quaternary ateatigraphy-ConUnoued Geologs hintery ...... 9.i 3 - 2. Diagram of topographic and geologic positions ot prinelpal plant asociations Lahontas Valley group-Costinuad Tertisry history ------_------...- tN a FosSils of Sehooand Indian Lakes age ... Quatetnary history* ...... 97 3. Eaposures of Bunejug and Truckes formations In White Throne Mountains† † 13 4. Diagram showing age and stratlgraphln relations of the five main (named) lete Quaternary sils Itn Ue Cason Soils of Sehooand Indian Lakes age-...... Pre-Lake [shontan history . . i97 Desert area ..._._...... fllatory at lake Lahoana-...... Ineiplest unnamej Sni ot middle Indian 9g 5, Section through basin ot Paulte Wash ...... Lakes age ..- .----- 26 ------* et. Uime _...... ng ...... 6. Cocoon sil. A, At type locality: R, on sloping urfaces- Harmon School sod .. il....._.... Wyesmaha 27 time .. . .. P 7. Northern piedmont of Desert Mountains...... Turpah formation. ...----.- Churcbill Interval .. ... - ..... 100 2° _-_- 6. Gravel ot Ecta formation ...... General featurss .... ------.---- SO Sehoo timeUrns------_ . . 100 9, Compound high-lvel bar near RuFdellSpit. .. Eolbn sa nd..-- _------Post-lskt Labontan history- 30 102 . 10. Aerial photograph at western LahontasnMounta ns. Turupab timesi... 102 31 Loes _. 11, Aerial views. A, High-level spits at southwest edg of Carson Desert; D, compound low-hevel apit...... Toych Interval ...... -10...... 103 32 Alluvial nand.------12. Occurrences of the Wyemaha formation...... Dinconformity coeval with the Turupah Fallon time . -.. . 103 33 13, Type locality for CiLtrehill soil and lower-memberoaSehooformation and lower tongue of Indian Lamsesformation. formation; evidence Deposltional history In the bhaln 'ePs; 39 of romplete lake 14. Churchill soil on allIviul gravel of the Wyermahaformation ...... deuIredntln Interloi ...... 103 :W' 41 15. Eetza, Wycmraha Sehoo,and Indian Lakes formations 42 Fo&-Isi ------. - - -- Erosional and depenitlona. history In :, 16. Lithold tufa of the lower member of the Sehooformation 49 Toyrk sol. _ the highlands - 105 17. Lithoid and Corasline"tufa of the lower member of the Sehoo formation Humsn occupation -os 50 Stratigraphic relations and occurrence -' 18. Crilular tufa and thinolite Profile charactertics. . Climatic history -. 106 S5 ComparIson with previous Interpretatlon 106 19. "Heads" of dendritie tufa ...... ---...------. ------.---- 52 Fallon formation ...... -- .. 20. Dendritic tufs ahoaIng internal structure General features. Cotrelation and age of the Quoternary deposits and soils. 108 53 21. Blanket deposits of dendritie tifn at Eetna hountoin 54 Means of correlation . 108 . Lower member .- - 22. Specimenshouing lecture of tufa "branches" and speoimen*howing tufs "heads" resting on late thinolite.._ Correlation of the Cocoon, Churchill, and Toyeb 53 Upper member .------Z3. Eerly and lute lithoid tuba of the upper member of the Sehoo formation soils, group, and Fallon forma- 50 Luke and interlake units. 2J. Lithoid tule of the first and third lake units of the FYalonformation Uon, with late Quaternary soils and deporits in 57 Eolian sand .... 25. Geologic map of Spiltsouthwest of Bunejug Mountains ...... _ the , Sierra Nevada, and Mono 58 Alluvium. 26. Lake areas.. -110 ... Comparative columnar Sectionsof clay of the lower Sehoo 60 Colluvium. 27. Diagrammatic cross section shownIg occurrence of thinolite Lake sediments and ahore features. Comparion wsith previous correelstons of Lakes 61 Lahontan and Bonneville . 111 28. Hachure mop of Russell Spit and vicinity ...... 68 Foails...... 29. Geologic Evidence on absolute age...----- .-.-.-.--.-.. "I map of Russell Spit and vicinity ...... _...... 07 Sols of Fallon age.. --- 30, Sand and elay or the upper nteo'ler of the Sehooand Toyeh soll. General features. General deductions on late Quaternary correlatIon, 70 31, Diagrammatic crosssection rhowing relations of the Fallon, Turupohb Sehoo, and Wyemaha formanions. 76 iLDralsn nil . -.-- -. climatic history, and soil de elopment In the northern and adjoining mountains -113 32. Fallon formaton disconformable upon Sehooformaton .. _.___._.__...... __ s0 Soil of late FPlson age. -. --.. 33. Geologic map of tl'e type locality of two units of the Fallon formation .- ..-...... Structural feature, of Lahontan Valley and Fallon age-.. Synchrony of the fiuctuationa of Lakes Laontasn and B8 34, Geologic map showing relations of varlous units of the Falloetformation along a portion at Wildeat snrp 89 General relations BonnevIlle ...... ------_ - -- 13 Relations of the lakes to mountain glsciatlon - 113 35, L Drain soll ...... 91 Pre-Schoo faults 30, Section through southwestern part of Sagouspefault zone. Time and climate In noil formation . 113 93 Powt-Schoo faults. 37, Earthquake cracks. Wildcat fault zone ------Econumle geology- .. ... 114 95 38. Comparison of various Interpretations ot lake Lahonban history. 107 Other marginal faults. Natural gas and petroleum 114 30, Radiocarbon dtes from the Lake Lahont n areaea.... _ .. _ _ - _ _ - _ 112 Sagouspefault none . Mineral depolts- . 115 Other Inlerlor faults. Construction materials...... -- 116 Ground wr .... Diaptacement of shorelines. 117 Selected bibliography 117 TABLES Ponrible explosion craters of late Fralon age newr Stratigraphic aectiom, soll-profile seetlons, and well log. 121 Stillwater Lakes ... - - - - Fcaall-molluk localities -15...... 151. Earthqaakes In bistorlo time -...---.. Indexn-i_...... 1s5s..... rass T7Ats 1. Climdati data at Fallon, Churchill County, Nev .------I 2. Climate data at Lahontan Dam, Chltrehill County, N ...... 6 ILLUSTRATIONS 3 Major Cenorok, rock-ntratigraplic units In the southern Carson Desert area. I 9 lrs'latnas t swst nna 4. Principal differences In gravel units of the &ehooformation .. 43 5. Tuaasof the Zeta., Sehoo.and Fallon formatlons ...... 44 6. Mollusks in the Eeta,, Schoe, and Fallon formatlonsa... . _ ------74 rto rr. I Shaded relief map of the Carson Desert area. 7. Sldiierioou of the Fallon formation.------.-...---....---- _-.... St 2. Topographle map of the nouthern Canon Desert area. 8. Comlbustio (Ononttype) an-nsl of natural gas from two wells near Stillwater. Nv .... 115 3. Geosgie map of the Carton Lake quadrangie, Nevada, -I 9. Analysis of satural gas from tao wells 9 man south of Palson .... -... - 115 4, Geotogic map of thle Stllater q.uadrangle, Nevada. 10. Stratigrophie senlons In ticesouthern Carson Desert ara .... , _.__ 121 5. Geologic map of the Falln quadrangle, Ne-ada. II. Soil-pro6le Sections In ite southern CarnonDesert area 143 6. Geoloic map of the rsavern Soda lake' quadrangl, Nevada. 123Lop of nells In the nouthern Carnon Derert area. 148 7. Geogic map of ..nacleddleat strn end of Wyemaha Valley. 8. Croansclon, wretern W nmalasValley. It 9. Altitudes avidtime relstiops of horelincn in the Carnon Lake qrtadranglck I 10 Relative times of soil formation sud tIf deposition. 11. Slap of CarsontRiver ch-,l- an.dhigihut lake IeVel of F allon time. i 12, Correltion of thr late Quaternary sucerrsions of thc Lake LAhonta.n Lake Bonneville, and Sierra Nevada areas, I41I N

LAKE LAHONTAN: GEOLOGY OF SOUTHERN CARSON DESERT, NEVADA

By P. B. Ionsuoi

ASTMACT oil of late pre-lake Lahoatan age; (a) deep-lake sediments and minor amounts of Intertougulng subseralmdeposits at early This report presents a stratiraphir study ot an area of Lake Labontxn *ae; (4) subaerial sediments. Poll. sad Inter. asout 880 square miuesIn the southern part of the Carson tonguing shallow-tbke aedimentsof middle Lake Lahonisa age; Desert, near Faleios Churehill County, Nev. The exposed rocks (i5 deep-lake sediments and minor amounts of Intertoaguing and surficial sediments range In age from early Tertiary(?) suhaerial deposits of late Lake Lahobtan age; (8) lemertl . 4 to Recent. The isle Quaternary sediments snd soils were sediments sod sott of ealy post-Lake Labontan age; an (7) especially studied: they furnish a detailed history of the fue- subaerial sedhuenbssnd latertougutag shallow-lake sediments of tuatlons of Lake Labontan (a huge but Intermittent late Plela- lte post-Lake Lahontan age. Only tbe deposts of Lake Libon- toceue lake) and of younger lakes, as ell a. a history of late tan and younger ageare widely exposed. .'TI Quaternary sedimentatIon, erosion, oil development, and cli- Pre-Lake Labontan history Is fragmentary, but Lake Labon. of the northern tan sad post-Lake Lahoatan history Is fairly complete. A lake 1. matic chnnge that probably Is representative purtof the Grent Bosin. older than Lake Laboatan 14 suggested by a single exposre of The Tertiary rocks are divided into five main map unia. Ioeutrine sediment After deposition of this sediment, a long .iI The lover three are chiefly taras: the Miocene or older andeite Interval of lake recession or desiccation ensued. duriag which . i of Rainbow Mountaln and dacite of Rainbow Mountain, and all lakes remained at least 420 feet below the maximuue level A1 the Engles Douserhyolite of Mlocene to Pllocene age. The of Lake Labouatn. During early Lake Labontan time the lake I Truckee formatlon. vbleh overiles these consists of aluf.tut- resched Its maximum level of 4(380 feet, receded hbrerly to at furolus sndstone. grael, diatomite. and limestone, and eontaina least as law as 4.100 feet, then rose again to 4.340 feet In .i lower Pliocene fossls. The youngest sad most extensively middle-Lake Laboulan time the basin Intermittently was dry I exposed unit, the BuneJag formatisn. ts mainly andemltic and and held shallow lakes. During late Lake Labontan tide the basaltic lavns of Pllocene and possibly early Pleldtocena age. lake bad 3 staximums sad 2 recessaons; feat It rose to 4,370 4 Cenerally It overlies the Truckee formation with an angular frelt then dropped to at least ,900feet, then rose to 4.190feet. t unconformity, but In the south Its lower part may Inltertongue then dropped at least to 3.500feet. and then rose a MA time 4II with the Trucke" formatloa. to 13.00feet. During early post-Lake Lahontan time the bxadn All the Tertinry recks are cut by hlgh-angle normal faults. genersily was rompletety dry, and during late post-Lak Lahon. I andcotmsmonly nre more or less tilted. The degree of deforms. tan time fire ucceslve emall Iskes having maximum depths at . 11 lion Increnres with age of the rocks, showing that faulting was 15 to b6 feet oscupied parts of the basin Door. I fairly continuous. The earlier Tertliry deformations were The writers deductions on the lake history give to support otestly compreslonal, with notable strike-slip faulting, but to J. C. Jones' (1V25) Interpretation of a single lake cycle i Qunternary faulting was dominantly tensional, Few of the starting a more 200 year or soago, These deduetib_ agree. shier faults are exiosei: mostloposed faults date from two however, with most of lRusell s (1885) end Antxe (14 1948, climaxes: the fieet in late Pllocene or early Qunterenary time. 1152) conclusoms. The writer's belief that Lake Laboaltn had . -1 and the second probably also In relatively early Qusternary multiple mtaxmums during both early and late Lake Labontan tihue-long bWfore Lake Labontan time. During the interval times aupplementaboth Russel. and Asters' iaterpettons; i of relative qaieacenee between these two climaxes extensire that the lake dried completely in middle-Lake Laheotn time pediments formed at the edges of the mountains. The main tbcottrary to Asterd Interpretation but In line with Rtuellis; tnults were active repeatedly. and as moat of them bounded end tbnt the lake reached Its bighest level In early Lake Labon- .1 ountain bloeks,relief was Increased progressively to a maxi- tan time is as Anters Inferred, but contrary to Rousella II toum at the close of the second citm x Subsequent erosion conclusion. andsedimentntion hare been more rapid than faulting and have It sa seemspossible to correlate the later Qunternasy stratI- .11 progressvel nloweredthe mountains and flled the basdns graphic unils of the Carson Desert with theoe of the Lake The Carson Desert, long a major drainage sump of the north- Bonneville sod Sierra Nevada areas. largely by mesan of soil weotcrn Great tItuen, contains Quatersary sediment prohably strAtigrapby. The suecessbonsin all three grena have similar itore thnn 1.000 feet thick In plaes. It is one of the largest soil sequeneesIn terms of relative age and relative develop And deepext bnorna of northern Nevada inundated hy Lake tent of the soils. The physical record In each ares Iadlesteg Ltthontnn; its D0or lien as much as 615 feet below the highest that the soils formed during distinct widely separated Intervals. ehorellne. The area tos-ped covers the whole range of take is response to infrequent comblaltlons of climatie tfeaon that flttctuations fromnhighest Io coolisletedesiccation. The exposed induced erosional sability and a more rapid rate of chemical Qunternnry d posit,. exelcsive of rolr aftr, comprise seven main weatberlng than mormsl. The meot atrongly developed soils units wbich are, from oldest to youngedt: (11 lactrIne sedi- foroted during the matn Intervals of lake deelceatlon and de- ments of pre-Lnke Labontan age; (^2 subaerial sediment, and glabiation; weker oils formed during the shorter recession I .3I

4 LAKE LAHONTAN: GEOLOGY, CARSON DESERT, NEV. GEOGIAPDIC BETTING 6 they do not extend into the highlands. They aided chemical history of the tufa deposits, which he believed the in determining the altitudes of the shorelines of low. to be pseudomorphic after gaylussite that was deposited XAOR L.NADoPRM floor-that border , , and level lakes, but their primary ground control was too on the recession of the first lake cycle. lie thought that CARSON DESERT AND ADJOININO BAINS Stillwater Lakes. lowlands south of the Carson Sink unreliable for use as a mapping base. To obtain neces- the lake probably overflowed at its highest leveltior, Carson Desert, the intermontane basin surrounding Interrupting the three low TOlc1nic hills: Rattlesnake Hill, the Soda sary vertical control to determine shoreline altitudes, although he knew that LWal Lahontan had no outlet Carson Sink and Carson Lake, is the largest intermon are about 25 miles of lines of levels were run along the high-. in the area examined, he believed reports of an outlet tane basin in northern Nevada. This basin is elongat Lakes uplift, snd Upsal Hogback. to South- land shores of the Carson Lake quadrangle. . to the south. King grouped most of the Lake Lahontan northeastward, and is 70 miles long and Several side basins extend southeastward 8 to 30 mile the bordering sediments with his Humboldt Pliocene formation and wide (p1.1). It is the southern part of a I westward from the main basin between northeastward 16 by 6 ACXNOWLEDOMENT5S some with his Truckee Miocene beds. trending trough 125 miles long, and is separated byo. mountains: Salt ellas Basin, the largest, is (Turupah, Eight- Many scientists gave important assistance and advice The classic study of Lake Lahontan by Israel C. only a low divide from Buena Vista Valley, miles and floored mainly by playas the northerm drained by Dia- in the field. Ernst Antevs visited the area twice. Russell between 1881 and 1883 was published as U.S. basin mile, and Fourmile Flats); the basin of this trough. Most of the Carson Desert i 6 miles Arnold E. Withers, of the University of Denver, made a Geological Survey Monograph 11 (Russell, 1885). mond Field Jack Wash is 12 miles long and 3 to below an altitude of 4,000 feet. The highest large ares basin reconnaissance of the archeologic sites of the area with Russell and his assistants, Willard D. Johnson and of interior wide, with Bass Flats at its northern end; the lowlands is an old delta that borders th4 these the writer in 1949. Robert F. Heizer and two of his W. J. McGee, covered in reconnaissance the, whole Lake valley of the near LAhontan Dam, at as drained by Sam Spring Wash is also included with graduate students, Norman L. Roust and Gordon L. I.ahontan basin, more than 20,000 square miles, noting altitude of about 4,100 feet The lowest parts of thie aide basins. Grosscup, of the University of Californin, Berkeley, both geomorphic features such as beach terraces, bars, basin are: Carson Sink, a playn 20 miles in diameter in H5GLANDS BORDEINO THlE BASINS Calif., investigated several arcleologic sites. Hans anid spits, as well as the strntigraphy of the lake depos- the northern part of the basin at an altitude of about Jenny and Robert Crocker of the same university ex. its. Russell's interpretation of the lake history has 3,800 to 3,880 feet; Carson The nearly straight Stillwater Range (formerly f LAke, a large shallow lake the Carson amined the geologic relations of the soils with the writer. proved generally correct. in the southerilpart of the called the Paiuteor Pah-Ute Range) borders . Z' basin at an altitude of 3,908 of Maxwell E. Springer of the University of In the river trenches Russell observed two zones of feet; and the Stillwater Lakes, a Desert on the east. The north and central sections .t. chain of small lakes, of the made chemical and physical studies of the soils; some of lake clay and silt ("upper lacustral clay" and "lower I ponds, and swamps that extends 20 miles southwvest- this range are 4 to 10 miles wide; the highest his data are included in this report lacustral clay") separated by a zone of fan alluvium ward from Carson at an altitude of about 3,870 to 3,880 peaks above an altitude of 8,000 feet is Jobs Peak lower To nianny inhabitants of the region the writer is and lake gravel aned sand ("tuedial gravel") and cor- feet. (8,806 ft). South of Mountain Well the range is Ji several parallel ridges from greatly indebted for courtesy aid cooperation. Special rectly inferred two deep-lake periods separated by a Carson Sink is nearly level, varying less than 10 feet and wider and consists of thanks are due Miss Laurn Mills, Mr. and Mrs. Wendell long interval of probably complete desiccation. From 5 in altitude in 20 miles across its central part; it is com- which a small spur extends into the map areas. Carson 7llieat, George Forbes, aid the late J. }1.Jolhnston, of detailed mapping of shore terraces and spits in several monly heavily salt encrusted, and is completely barren Along the south and west borders of the Fallon; Harry Richards, watermnaster for the Truckee- localities, he reasoned that the highest level of the first except at the months of the Carson and Humboldt Desert are several groups of low mountains that have Carson Irrigation District; William 11. Slattery, area lake cycle was about 30 feet lower than that of the Rivers, where patches of saltgrass are watered by inter- crest altitudes of 4,500 to 6,000 feet: the Lahontan, Camel, engineer for the U.S. Bureau of Reclamation; Vincent second; evidence for a contrary interpretation is given mittent overflow. On the west, north, and east the sink Bunejug, Cocoon, White Throne, Desert, Dead P. Ginnelln, University of Nevada; and Philip A. Lay. on pages 64-65 of this report. Russell determined that lies close to the piedmnont slopes of the bordering moun- and Hot Springs Mountains. lander of Fallon, who took many of the aerial photo, that lake did not overflow at any time. 1 tains, buton the southand southwest .3 12 to 34miles of CLIMATE graphs used. Russell's study is the only one that has covered the 19 lowliands intervene. Although the local relief is small, PREVIOUS WORK whole ares of the ancient lake. Several geologists later the lowlands are ronghi in detail and have a topography The Carson Desert is one of the driest and warnest The earliest account of the geology of the Carson studied parts of the ares, notably J. C. Jones (1925, peculiar to areas of strong wind action. parts of northern Nevada, owing to its moderate alti- I Sierra Desert region is the narrative sketch by12),ErnstAntevs (Hen2ra),andG.M.Stanley (1849). The lowlands away from the river flood plain consist tude and its position in the rain shadow of the 4. with ~nman,geologist for Capt. J 11. Simpson's expedition No geologic mapping was published from any of these of irregular sanlhills, sand plains, and clay flats. The Nevada. The climate iscontinental in theextreme mana,fo eolgisCat. . 1. Snalwn' exediion later studies, but Antevs published detailed strati- t sandhills are mostly dunes; some are stabilized and warm summers, cold winters, wide diurnal temperature of 1858-59 (inSimpson, 1876). Englemann apparently phic sections of lake sediments exposed in the valleys others active. Locally they make and relatively wide fluctuations in annual rain- was the first to recognize the shore features of Lakenty F up three-fourths of range, I the terrain and rise asmuch as60 feet fall. Cloudless skies are the rule, strong winds are Lanbiontan as evidence of an ancient deep like. k above the The first systematic geologic investigation of the D. F. Hewett in 1922, and R. V.' Richards in 1946, general surface; elsewhere they are few and small, or frequent, and evaporation is high. regioni was the geologic exploration of the 40th pairallel, mande hirief recomnnissances of the oil and gas possibili- i. lacking. The strongly developed dunes commonly form Precipitteion.-Meteorologic records for Fallon and ties of the Fallon area for the U.S. Geological Survey. discontinuous long parallel ridges that trend east- Lahontan Dam are given in tables 1and 2. The mean of Clarence King, assisted by No reports of these investigations have been published, under the direction 1 northenstwnrd, and are separated by hare flats or shal- annual precipitation at Fallon during the 55-year rec- Arnold Hague and S. F. Emmons (King, 1878; "ague hent the field records and logs of oil and gas test wells 74 ord prior to 1952was 4.95 inches. Three-fourths of the in this study. 1 low deflation basins. The clay flats are scattered, but and Emmons, 1877). The area mapped for the present and crater wells have been helpful precipitation falls between December and May. As in by Hague .: they are most itmnerous and Inrgestnear the sink. study lies niostly south of the area mapped I most arid regions, annual precipitation varies widely SETTING Through this complex the Carson River has formed and Emmons. King gave Lake L.Ahoutan its none, CEOGRAPHIC from year to year, extremes of about 2 and 8 inches i its flood plain. At iualhontan Dam the flood plain after Baron LaHontan, an early adventurer and ex- The ariddesointionoftlheCarsonDe-sert reagptside is At LAhonten Dam the mean an- incised 120 feet below the geceral surface, but the river have been recorded. plorer of this region. King discussed the ancient lake tlie irrigated farming district appeals to fear people, 0,4t nual precipitation for the 44-year record prior to 1952 amidgave n map showing the maximum area and indeed repels most. Few parts of the United Stntes trenrhgrndially becomes shallow downstream. About 4.35 inches; extremes have been about I and features, 41/miles west of Fallon the trench is only a few feet was about inundated. lie postulated two deep-lake periods, sep- have so starkly forbidding an aspect of parched low- 2 9 inches. Precipitntion in the surrounding mountains arnted by an interval of major recession or complete lands and sonmber mountains, with only the scantiest deep, andthe flood plain fans out over an areaof 120-. is indoibtedly higher ltithasnot been recorded. Even desicentionr; this postulate was basedon a hypothetical verdure. I Thislower flood plain, shaped like nragged fan, merges the higher parts of the Stillwater Range contribute downstream with the almost level plninr-fornier lake little runoff, however, becauseeofthesmnldrainngearea LAXE LARONTAN: GEOLOGY, CARSON VESERI!, NEV. LAKEL4EO~~~r~l: OEOLOOT,CARSONSETTINGS DESERT, 14EV. ~~~~~GEOGRAPHIC 7 TAsLz I.-ClimaMt dots at Fairs,, (Aerkteamt NrlrEpectmc.. Station), ChorchilU Csolstr Yes'. yeas p r to 1950. The relative amont of evaporatioz The water area of Carson Sink has varied consider- 1. . : ~~~~~~tAIUtld.1Sb61ali from tkis pan was probably close to that from the lank ably in recent years. During the 18tOs and 1870's it T.Wer.*os.1. ft,,n 7.60.55.5 In. . was a permanent lake that measured about 15 by 20 ?ndsll~~lio..io00.5.. A~iOOA .1 DJAXICAGE miles and extended to about the 3,880-foot contour line, Caxl: Sink is the sump for both the Humboidt and so that Pelican Island actually was an island (Antevs, Cara Rivers,l whose combined drahaage area of 26,tO( l2SIb, p. 30). Since then, however, the sink generally tqrei miles is 57 percent of the toeal for Lake Lahon- has held water only part of the year, and for Several .ao~~~~~oy. L~~~~si 716 51. decades II 55 - . A LAO 64 To 4 SW t. The Humboldt overflows Hbmlsoldt alke only it has been generally dry except for a small ares .n ...... near the mouth of the Carson River. II . 01ft. . 21 26 61. -.5 LII '.0 2 -xaially through White Pbain pTars into the sink, High river dis- IL 47.0 1 I .&.5no 10 0 OW II but tie Carson River reaches the sink during meet of charge flooded it extensively during the winters of 1943- 44 and 1950-51, II WM0_ 0ft. 11. 2L.4 103 51 iS, 1.00 l.6i0e the *ft:, particularly since development of the New. but each time this water evaporated 770010122. 115~~~~~~m45.0.0 0 t 2 2 70 1.0to5 during the following summer. II S c~~~~~~~cO .,. 110~~~~~~~~~~~~~~~~23.6 01.1 II 11 so7 .5 lard P.xclamation Project...... 2. 00 0 l .0 .0 I01l 0 2 N4 i ...... 40.1 42 1I1.0 72 .-Il .00 .6 05 Tie Carson River enters the baeia at Lahontan Dam i I',.,. 4~~~~~~~~~~7.0a 4.2 70.7I 105 t53 4.0 1.516 ft0 a~ 1 Z. , been the major contriburor of sediment to the eVOTATroV (1701) 1025 - . part of the basin. It dr insbout 5,900 square The vegetation, which reflects I zz. the aridity, isthe north- rc7 . bt of this only 1.3)00qusar miles is above Ln- ern desert shrub asuociation, dominated by desert shrubs, 'no,50027 Clool1 ol). 3,01. 1.0.,1102 5.0.15715l~ 0111011)11570 100193h10 101050 NN~ .. d.": 17,.0NW,olU 110,..1521. b_-- Dam, nnd most of its vo- e comes from 800 herbs, and grasses. It is closely controlled *1'00."C10510106101 1.10. AoooI005100yi~lI10C0.1 7o~. 35. '.~lbo.,'o.- 6II= by soil con. 9q-- miles in the Sierra Nevaat. The Humboldt ditions and drainage. The characteristic plant associa- Z and high evaporation. The Carson River, which flows generally higher than average from 1889 until about Pd.:'. nowecontrolled bv Rre Pa-cI Reservoir,and the tions of this area have been described by Billings from the Sierra Nevada, furnishes nearly all the surface 1915, but was lower than avvrage from 1915 until 1934, i Cnrvc by Lahontan Reservoir. r- tiarson, augmented (1945), who showed the relation of the main associations 1, by war from the Truckee inflow to the Carson Desert. an extremely dry year, and hIs btnenabove average since i River. irrigates more than to topographic and geologic position (fig. 2). Heavy local downpours occur occasionally over the 1934. zresac:!Y in the Xewlands Reclimation Project. The little greasewood-shadscale association is the cli- Tie of molltain-, but they are generally many years apart in Ternperature.-The maninini temperature recorded v- ~_tnnel the Carson fronm lAhontan Dam to Car- max assemblage on the well-drained lowlands and low the low mountains wvthitli the mnp aren. Thunderstorms at Fallon during the 49-yeor period of record prior to Z Yr _ I formerly wsasmeanderrx -miles south of the mountains of tie mnp area. It consists of low spiny Y are infrequent. Snow is rare atd generally light in 1954 was 106° F, and the mitilmum, -25' F, an extreme e d it divided into several d-i-ributary channels; shrubs that cover 5 to 12 percent of the ground; these the lowlands nid low mountains and rarely liigers more range of 131° F. The averaig January temperature is Z, t,-.v ieriver has been smighilernt. deepened, snd con- shrubs are generally evenly spaced and separated by thtan I or 2 days, but the higher parts of 29.8° average Es. -ithin a single channel exsep- where artificial di- the Stillwater F; July teniperature 74.1° F; and the I bare ground. The dominant species are little grease- Range are Snow covered during most of the winter. mean annual temperature, 'dl.j° F. The mean annual I tare made. wood (tSareobanu baiteyi), shadscale (Atripter eon- AMorethan S0 yellrs of weather records in the Truckee temperature at Lahontan Darmis 53.8 IF. In July and Tze interior lo-lands are ro s-id that even ephem- fertilofla), and bud sagebrush (Arfemisiaspineacens); River drainage area, sllpplemented by tree-ring and August temperatures comitutlly reach the low nineties, e -remcoulrseisare very rare. IxLrgearesare with- Ephedera nereadenois occurs locally, and in the transi- lake-level studies (llardnlaio and Venstrom, 19tl),show but nights are cool, comnioldly below 450 F. Frosts con- o= sin of drainage, and the ren-_Ander Iave widely tional zone between the mountains and lowlands some alternate periods of above-average or below-average tinue until late spring anmlvlinmence in early fall, so rS^-. sImnl short gullies- thna A-w only after infre- hopsage (GOmysa spillosa) and white sage (A',rota precipitation frono 2 to 20 years long, some broken by that the growing season averages only about 125 days. .5. cS-- heavy rains. &mnata) are present. Perennial herbs and annuals gen- single years of opposite character. Precipitation was Winter minimums are rarely below -5° F. Long-term Vaie water from the irriglativ project feeds Carson erally are sparse or absent. temperature fluctuations anr not pronolnced and do not Lob. the Stillwater Lakes. CareyK=Sink. and the Indian Other plant associations are restricted to relatively TAaz= 2.-C0t.tc tut at Lbes!to. DOe. CAurheill correlate with the precipitation changes. Lat5:. The Stillwater lAk-e., vhih have the largest small aress of abnomnal soil or drainage conditions. 'OlotWv, Nev. r.er- area of these four. consist ef mnany interconnected IAlIlMude4,inkD 1- lind.-The average aninaul -ind velocity at the The Dolie association, typified by the small shrubs and Fallon Agricultural Experiment StAtion during 1909- -iwa and small lakes that hbtv intervening marshes perennial herbs Doles polynrdese, Atriplex- caescen. M.-I I two.IloAb. ai ' dands. They are fed frors the solith by Stillwater I-W.- 15 was 3.75 mph; the higlust monthly average (April) (shadscale), Tetrfdyitia comosa, and T. ,inbratn, and Z- I. was $7,:zc and drainage canals of zhe rew-lamtion project, d, 700I2' Rtnst5I L.0., but 5.4 mph. Sudden strong but brief windstorms locally Itymenochem fnshcolata cid Oryzops;*e hyAineso- nhtio s±Cdhev intermittently orerikia- northward into Car- are common in spring and early fall, and redistributeI ides, is limited to areas of ealian V4 SInk. Prior to 1140 the like ares was about sand. The assocint iot 11.2 ...... much dust and sand. S1)nmi siminier vhirhvlinds ("dust 12 370 is prominient where the annd is stabilized, part icilarly ,4.1 ...... - devils") lift dust several s long and 4 miles wide. br- it is being enlarged by ...... hittdred feet, where upper air in the western lowlsnds south as ...... *rS. Fish and of Carson Sink and in ...... Got I...... currentsmay carry it for long distances. - Wildlife Ser'e to develop new lake AS I...... tile sandy passes in the highlands. The associntion ------...- 51. a s mrsh1 areas for waterfowl. 'aI ...... Er-aporatiotL.-Humiditv is low, and the annual erap- re, ------7talron Lake clnnicterized by big gressewood (Saero-eoauf rrs,;-,v- "S .s1 oration rate exceeds precipitation I4 consists of ntsrs~lshd and shallow open 70...... 440 .,.7 I...... by n ratio of about M.S -- .... -r!r and is about 7 miles long r-d 3 noilet side lotus), occupies salinecinyey soil at the edges of phnsts 42 : ...... 12 to 1. Tle Average almral evra-i;t'ion from a BPI at the at .nt highest and poorly (Irained lowlands where the subsoil AlkI pan ret in the ground at the Agricultural Experiment stage; it waswet erly larger, but has nlwnys : lowered by deenliing S:'.''"er is moist but tlie surfnce crust dries in Inte sunmer. 40 ...... Stntion near Fallon frouil It08 to 191t was C.4inches. Sloglih. which is The .4 -ze suttfow hanulel 1 40 which is equivalent to n fnve-wvt er eviploration of nbout into the S 'twerlAkes. The in. rabbitbrush associntion, characterized by two kinds of 0in0h11-cs,Cll,01"It 11005A-102 l.5,0 1011;v. t5.s.-i Mt.J..): 17.. -I i;555.I.M697.. .5 inches. 4E= Lakes inchlde more than 1 * L Inkes and pomis rabbitbrush, CAryorhommusies "luAcomus var. ronsihnR4 11710,1,ok _2,Y207011.V,05 111 0,.XI."IS, ,o154iho~n 5 3501)0100505)10~'relcs00ISO I. ov.0. .S.5,05,lh50,.. I105. f.rmftl ly irrigation wame waci: deflation and imlter- and C. naoueo~sus var. *7St.. iI V l 0 -4:US % A standnril tioating pall t lohnontan Dnm showked a holoteucus, is largely limited to o Y. 4470 mean annual evilporatif.n of about 74 inches for the tfi * =e basinis. recently drained or disturbed ground. LAKE LAHONTAN: CEOLOGT, CARSON DESERT, NEV. TERTIARY BTRATIGRAPHY AND STRUCTURZ 9 Age canals that prevent waterlogging of the land and rocks are exposed, although such rocks crop out exten- EXPLANATION remove accumulated alkali, both formerly serious prob- sively in nearby ranges. Details of the stratigraphy and structure of the Tertiary rocks were studied only d. a. .84 lems. part . - I . Airipac-Sa,,eetatem j Aketai.W. lridttae The 125-day average annual growing season permits in the Carson LAke quadrangle and in the eastern . . (Shadsete-tlttle grealewood) .(Rig sagebruib) the growing of alfalfa (three cuttings) and most temr of the Desert Mountains in the Fallon quadrangle, and perate-zone staple crops, vegetables, and hardy fruits, this discussion refers only to those areas. into five main map . I . ~~Sireaoslelm Ssiep - Alkmireetfeeans The large compact area of irrigated land, full-season The Tertiary rocks are divided -. .le resewood) (Altenrolfia) water supply, and good transportation facilities favor units (table 3). One consists mainly of tuff and tuffa- I . .. , s . cash-crop farming, but most of the farmland still is ecous sediment; the others are largely flow rocks, rang- from basalt to rhyolite, and minor dikes NORTHERN SOUTHERN Emergent tule o lations, used for hay, grain, and pasture. - ing in character HILLS MOLLS (S.Itgassa) A few range cattle are grazed in the Carson Desert and pyroclastic beds The volcanic rocks range rather widely in composition in each formation, but petrologic SAN ASOIL Highest Lhontan Beach al and surrounding mountains. The range in the interior of the basin is limited to intermittently flooded lowlands details have not been studied. Correlations are litho- ), 7 SarSalet.,awrrmttesli ~ ~ ~ ~ ~ ~ ~~ which support more than the usual forage cover. In logic, and must be considered tentative. (Rig greateeod) the low mountains at least 30 acres per Cow per month B-ASALT OF RAINBOW MOUNTAIN )o t Jz~~~~~Ppakt2m ? are reqlired, and grmzing is limited mainly to winter DOME (Cettc(Cottowood) D)erlu and early spring. The higher parts of the Stillwater The oldest rocks exposed are altered basalts and tufts, LAHONTAN SEDIMENTS S AND the best range because of the more abun- R. 31 E), AND RECENT FANS Range furnish exposed only at Rainbow Mountain (T. 18 N., dant precipitation. from which they are named informally. They are per- AREPLAYA_ vasively sheared, closely faulted, and much altered. OPEN WATE TERTIARY STR1ATIGRAPHY AND STRUCTURE Tile principal rock is dark-greenish-gray to black al- STRATIOBAPHY tered basalt(?), which is gellerally wenthered along 7,0.r. 2.-Dla~m. of lh. loo Ao~tld0,r"I.&I, am-tla o lh. prloepal plans aen inaIahIk Cn.m, D,-otesl-eo chocolate brown or maroon. It is mostly Fri. 811ll0j, (1145. as. 4). The pre-Quatertiary rocks of the map area consist of joints to dark volcanic and sedimentary rocks that range in age from vesicular or amygdaloidal. Determinable feldspar- Miocene or earlier to late Pliocene. No pre-Tertiary that of the phenocrysts only-is labradorite, and the The saltgrass association, consisting dominantly of TruanportationL.-Is the days of the Emigrant Trail esert saltgrass, DisticAius stricta and locally D. spicata, the Cnrson Desert wvasnotorious as the "Forty-mile *follnd on soils that range from moderately to in. Desert" one of the most difficult stretcles of the Over- TABLE S.-Miow Cenooic rorwktratrsphicu*it, isnAt .auoAc Caros Derl ares nsely saline, except the very driest. It borders the land route. The Southerm Pacific Railroad crosses the lore permanent playns, ponds, streams, and marshes. West edge of the desert from l1lite Plains siding to fSd i EPwh aldlrlpbkitan rDaat The cottonwood association consists of cottonwood Nazen, nd hns a spur lisle from Hiizen to Fallon. U.S. Popula fremnontit) and willow, the only native trees Highways 50 and 95 intersect at Fallon, providing ex- the area, and big sagebrush (A rtemipia tridcnta a); cellent surfaced highways to Ely on the east, Tonopah - FallO feormation Peot-LaIe Lahontan take snd subaerfal sedimenta. 33 le.e pInIlts border stream courses and some lakes and on thie sotIl, and Reno and Carson City on the west. olIds where the soil is relatively nonsaline. The asso- Several hard-surfaced roads radiate from Fallon. ationl is widespread on the river flood plain and was Outside 1l1efarming area ronds are fen and poor, ex- - lahoalan Valley group Sediments ot LAkeLahoenata and assoiated aubsertal sediments. 330 le original cover on much of the farmland. Russian cept for the main highways, although the county main- S ' Y Palute formatton-...... Fan gravel and colluvtum. 40 has become naturalized, tnins some graded roads to mines And outlying ranches. live, an introduced tree that Basalt of Rattlesnake HIll Basalt flows and agglomerate. seval wlth Pitute formation or earlier. 2c0 now wvidesprend in this association. Sand, during the drier parts of the year, and sticky mud " i~~~~~~~~~~~~~~nconformity? on the clay flsts after rains, impede travel. Much of lPre-Lake ILshontan lscua- Send and gravel; one expoesure. a ECONOMIC OEOORAPHY trIne sediments tIle mAp area is accessible only by 4-wleel-drive vehicles, uneronfoanlty? Populiaton, towrm,and setltlm-nts-The population or by horse or foot. Olivine basalt flaws. some basaltIc tuft, In upper part; Andealttc to basaltic BuneJug formatton floas It taerpart, wIth some daite and m.fc to ilicl tuf. Commonly restricted to the irrigated district and a scattering Agricultur.-All crops are irrigated. About 50,000 nunomformable upon Truckee formatton, but In places possibly inter- the main higlways. Fallon, the county seat of acres of cropland (about 10 percent of the total farm- fingers with Truckee. 630 long ft-lia ileunconformlty- Ihurchill County, is (lie only town, and had A popula- land in Nevada) have beeii developed under the New- Truke formation Eiide to mahe tuff. tuffaceous sandstone and gravel, diatomite, and lime- ion of 2,700 in 1D. The villnge of Stillwater, in the lands Recanmation Project-tthe first Federal reclama. 1i; ~~~~~tone, 50ii -Local unconfomlnty- astern part of the irrigated district, was formerly the tion project-which was started in 1903. It utilizes Eagles Itouse rhyollc Rhyolltic to dacitle flaws; thick and mislsve In lower part, thin and locally rincipal settlement ant county seat, but has gradually water from both the Carson and Truckee Rivers, ap"rlitnd pumtrous In ! permoot part, whth locally grades laterally 0 III.ltoler part oa Trucker ormatan. 400 eclilled in iloportance since 1908, whetl Fallon became stored at Lahontan Reservoir 15 miles west of Fallbn. funconforwilt3 now lIs only general store and 1915 the whater I Daete of Italtibow iltoun- Mainly dactie flows. 200? Acorpornted, nnd a Since completion of this reservoir in Lain bIot eight homes. Salt lVells isa roadhouse and motel supply has belen seriously Srort only in 1931 and " -Usnrontennltyt - and generally I1 S. Hliglway b0 on the northeast side of Il ito the canals nnd reservoirs tlte proj- S Bsialt ot Itanbas ihloun- BasltIle and ptomeamdmltie ftam: some ufI; much faulted 1934. addih to LaIn eoniderably altered. Basenot exposed. 70t 'mnmh Flat; they are operated by a single family. ect lands in tl1e Carson Desert are served by deep drain- It ______~ ~ ~ ~ ~ . I 11 LAKE LAE0NTANS. GEOLOGY, CARBSONDESERT, )cEV. -i4 TERTIARY STPATOIGRarYr AND STRUCTURE DAOLe NOUSE IFrHOLITZ unit in northwestern Nevada. The accessory minerals are olivine, augite, hornblende, and Phenocrysts are sanidine, quartz, biotite, and locally major sedimentary Survey has adopted the name Truckee magnetite; even in the freshest specimens these minerals Outside the Rainbow Mountains the oldest Tertiary plagioclase. Some flows are strongly flow banded, and U.S. Geological oc- for this unit. ar largely altered to chlorite and calcite. unit exposed is a series of rhyolites. It is here named the banding commonly is contorted. Breccia zones formation White Throne Moun- The Truckee formation is locally to extensively ex- The flows tend to form prominent ledges. Intercal- from the spectacular Eagles House crags, in sR l3, cur locally. In the southeastern commonly is overlain by and posed in the Lahontan, White Throne, Desert, and Dead ated with the dark flows are light- to medium-gray T. 18 N., R 30 E, in the Lahontan Mountains, where tains, stony rhyolite i into glassy to perlitic and pumiceous Camel Mountains. The lower part consists largely of ones characterized by abundant carbonate asnygdulea. it is best exposed. These crags are designated as the grades laterally intertongue with much of it is pumiceous, relatively coarse, Also interbedded locally are thin red to maroon beds type locality of the formation. It also is exposed in rhyolite, and the upper flows locally silicic tuft; Truckee formation. and unsorted. Higher in the formation water-laid sedi- that appear to be highly altered msfic tuff and red to the White Throne and Desert Mountains, and in Eetza the lower part of the body of rhyolite(l) having an exposed ment become dominant, and in places they seem largely purple beds of volcanic breccia. Some of these rocks Mountain. A small crops out in three small areas at lacustrine. The lithology varies gretly laterally as well are probably andesites. - Two bodies of rhyolite, each about a fifth of a square thickness of 100 feet edge of Eetza Mountain near US. High- as vertically and single beds or members cannot be The apparent thickness, disregarding faulting, is mile in area, and several smaller ones, aggregating the southeast ;1 way 50. The dominant rock is pink flow-banded felsite traced far. Because of this variability as well as fault- about 1,400 feet, but the faults produced more repeti. about 350 feet in thickness, are exposed at and near containing sparse tiny phenocrysts of biotite, quartz, ing and cover, even the local stratigraphy of the Truckee tion than omission of beds, and the true thickness is Eagles House. This is a complexly block-faulted area J and feldspar. In the southernmost exposure, the felsite is imperfectly known in many areas; correlation be- probably not more than 700 feet. which is structurally higher than the country nearby. T' is overlain by several feet of flow-banded glassy rhyo- tween the separate highland areas is problematical. rocks of Rainbow Mountain have The rhyolite is faulted against the Truckee formation, :1 The volcanic litb and by about 10 feet of perlitic obsidian, both Where its base is exposed, the Truckee appears to be yielded no fosails The basalt is considerably more de. which in a few places lies in depositional contact on the I dipping gently westward. locally conformable upon and intertonguing with the formed and altered than the overlying dacite, which is rhyolite. The base of the rhyolite is not exposed. .7 thick is exposed in a nar- rhyolite. In most places a pronounced rocks, so the At Engles House two thick flows are evident; the A rhyolite( I) flowv15 feet Eagles House in turn older than Mliocene to Pliocene Mountain. Truckee from the upper flowv,nearly 100 feet thick, is pink porphyritic row fault sliver at the west edge of Rainbow angular unconformity separates the basalt is Miocene or older. of Rainbow Moun- the Buneiug and rhyolite, and the lower, about 200 feet thick, is pale-' Although faulted against the danite overlying Bunejug formation, but in east, the rhyolite apparently conformably the two units possibly may inter- DACITE OF RAINBOW MOUNTAIN greenish-gray porphyritic dacite. The conformable tain on the Cocoon Mountains dacite unit in the contact between these flows is well exposed in the west- overlies rocks that may belong to the tongue (p. 14). Mountain is a distinctive se- area too small Truckee formation The dacite of Rainbow ern part of the crags and dips 10° S. Both flows have sliver itself (the dacite is exposed in an In the Lahontan Mountains, the and purple strongly saddles, ries of light- to dark-gray, maroon, conspicuous contorted flow structures. to show on the map). It is light-lavender-red felsite underlies most of Wyemniha Valley and other to quartz latite and rhyolite. banded dacite that ranges The lower flow is porphyritic biotite-homblende containing sparse small phenocrysts of biotite, horn- although largely concealed by Quaternary sediments, blocks in southern Rainbow It is exposed in three fault dacite that contains abundant phenocrysts of labra- blende, sanidine, and quartz in a glassy groundtnss and is locally exposed in the mountains themselves. In the northwestern block, the largest, on be definitely correlated Mountain. dorite, quartz, and biotite; these minerals occur in the This lone occurrence cannot The lower beds in this area are coarse water-laid putmi- the dacite over- it may be the base the west slope of the 4,845-foot peak, groundmnss also, with hornblende, chlorite, apatite, with the Engles House rhyolite, but ceous rhyolite tuff, pebbly tuffaceous sandstone, and with a westward on lies the basalt of Rainbow Mountain and magnetite. The upper flowvis porphyritic biotite of that formation. As it appears to be conformable tuffaceous sandstone, 40 to 80 feet thick. In at least two is con- dip of about 20' to 30'. Whether this contact rnyolite that contains abundant phenocrysts of quartz, the dacite of Rainbowv Mountain, it may indicate that places near Engles House the formation appears con- is uncertain because of small faults between them. One is in a formable or not sanidine, and biotite; glass commonly forms much of only a short tinme intervened formable upon the Engles House rhyolite: the other two areas are faulted or con- areas is considered where The contacts of the groundmnss. Near faults, both flows commonly are The rhyolite in each of the above deep gully about 2,000 feet west of Eagles House suggest the same se- cealed, but fault displacements strongly bleached, k-nolinized, and silicified. Unaltered to be correlative, but there is no direct evidence for the contact is exposed for about 650 feet. The rhyolite is uncertain and locally grada- quence. The thickness of the dacite remnants tiatd out in bold forms, of which the Engles this. The overlap of conformable is highly altered snd cut by innumerable smull shears least 200 feet. that the Truckee because of faulting but is at House crags are the most striking. The sheeted struc- tional Truckee formation establishes Beds of the Truckee, also altered, appear conformable than erup- The dacite is much less altered and deformed ture and vertical jointing produce bizarre erosional sedimentation overlapped and directly followed upon it and are horizontal to gently dipping. Locally Mountain but more so than the Throne Mountains. As sandstone and the basalt of Rainbow shapes. tion of rhyolite in the White at the base are several feet. of tufftaceous overlying Eagles Mouse rhyolite. The flow banding in In several small fault blocks west and north of the Truckee formation is early Pliocene in age (p. 12) pebbly tuffaceotis sandstone containing fragments of matic in- to be late the dacite commonly curves around angular Eagles House the upper flow is overlain by as much as the Engles House rhyolite is considered Eagles House rhyolite; overlying the sandstone is about of the atti- clusions and shows contortions independent 20 feet of thin flows of light-red flow breccis, which Miocene to early Pliocene. 20 feet of soft silty tuft, mostly deep reddish gray but with tude of the flows. Local brecciss are interbedded has sparse phenocrysts in an aphanitic to glassy locally light gray or buff; next, about 10 feet of coherent to TRmUCE PODS4ATION the massive dacite, as are thin beds of light-gray groundnmtss, and shows prominent flow structure. pebbly to sandy and locally limy tuft. white tuff. In the southern and eastern parts of the White King (1878, p.412-414) gave the nameTruckeegroup The second place is about half a mile farther north The dacite has yielded no fossils. It is probably Throne Mountains, extensively exposed rhyolitic flows to a sequence of mainly tuffnceomms sediments in north. along the same gully, where a depositional contact be- older than both the Truckee formation and the Engles are considered to be correlative with the Engles House western Nevada that underlie the Inte malic laVas and tween the two forimatioIns is exposl in another fault House rhyolite. Although not in depositional contact rhyolite; nanximum exposed thickness is about 400 feet. generally overlie rhyolite. "Fossil Hill,' in the north- block. Here also both formations are highly altered, with either, escept in a single questionable occurrence These flows also crop out in several small hills near eastern Hlt Springs (Kaw-soh) Mountains, was King's and the Truckee is mostly comarse pumiceous tiff. of the Engles House rlhyolite (p. 11), the faults inter- Russell Pass, just south of tihe map area, and in the type locality. le considered these sediments Miocene, Overlying the coarse lower zone is at lenst 200 feet of vening between the rhyolite and the Truckee formation northenstern Desert Mountains. They are mostly fel- but recent studies suggest ni enrly Pliocene age. Al. thick-bedded to thinly bedded shaly snd dintomnceous demand this relation. As the Truckee formation is siticor porphyritic-felsitic, but locally they are perlitic. though variable in lithology and now known to have tuft and tuffameous samndstonme, and some calcnreous tuff- early Pliocene, the dacite of RItinbow Mountain may They rnnge in color from light to medium gray, and in been deposited in severnl separate basins, rather than in aneous snoid and limest one (tablle 10, section 33T). Over- punii- be of Miocene or earlier age. places they have appreciable reddish or purple cast a single Iirge one as Kiting suplosed, they constitute a lying these beds is coarse ptretically nonlbedded 4bs"s o-44-2 LARX LBAONTAN: GEOLOGY, CARSON DESERT, NEV. TERTIARY STRATIGRAPHY AND STRUCTURE 13 nand rhyolitic tuff of unknown thickness, followed and (or) basaltic volcanism. 0. A. Thompson (1956) zone of fine-grained white tuff, dintomaceous tuff, reported intertonguing between the Truckee formation mite, and locally pumiceous sandstone or grit, and both rhyolitic and mnfic flows in the Virginia Cik, nonly more than 50 feet thick. This zone is over-. Nev., quadrangle. in places by 8 to45 feet of greenish-gray mafic tuf,. Several of the deeper wells in the basin interior may h is here the topof the formation. -have penetrated the Truckee formation, but the avail- the valley between Rainbow Mountain and Salt able logs are too crude to permit reliable correlation. s Mountain, the Truckee formation is extensively -The poor exposures, deformation, and erosion of the sed unconformnably beneath the Bunejug formn- Truckee formation make estimation of its thickness dif- The Truckee consists mainly of pink, light-green, ficult. In the Lahontan Mountains probably more than to white tuffaceous sandstone said siltstone, and 400 feet, and in the White Throne Mountains probably v beds of oolitic ostracod-bearing limestone. at least 500 feet, are exposed. ie Truckee formation in the Lahontan Mountains Age and corseltion.-The Truckee formation is gen- milly altered by silicification #nd clay-minerl all- erilly unfossiliferous. Fossil leaves were collected ion. The coarser tuff and tuffaceous sandstone from a single locality on Rainbow Mountain, and mnails have been especially prone to silicification, as in the wvere taken from three localities in the eastern Lahon- half a mile south of Eagles House and on the tnn .oumtains in the middle and upper parts of the l-foot butte southwest of Rainbow Mountain. Lo- formation, but these collections were too poorly pre- the alterntion has produced intricate patterns of served to be determinable as to species. :olored bands known as wonderstone. A few of King (1878, p. 415) believed the Truckee to be ) deposits have been worked on a small scale for Mliocene in age at its type locality, Fossil Hill, in the mental stone. Hot Springs (Kaw-soh) Mountains 25 miles northwest the White Throne Mountains a thick series of of Fallon, but Yen (1950) and MlacDonald (1950) con- .indurated white to pale-gray and cream tuff, tuf- sidered these beds to be Pliocene, and Axelrod (1950) DSo gravel, grit,and sand overlies the Eagles House determined them to be early Pliocene. Sediments re- lite and intertongues with the upper part of it (fig. ferred to this formation are widespread in northwest- It is correlated tentatively with the Truckee ern Nevada. Fossils indicate that their age is early iation, although it does not resemble the bulk of Pliocene, but they were deposited in separate bnsins of formation in the Lahontan Mountains. The larger differing structural histories and may not correlate s are almost entirely pumiceous rhyolite, pumice, exactly from basin to basin. Further study may almow some felsitic rhyolite; a few basalt or andesite that in some areas they include beds as old as late Uio- ments generally are present, and locally make up as cene. In general, they underlie the andesites and ba- It as 25 percent of the rock (fig. S8). Sorting is salts of Pliocene (and possibly early Pleistocene) age rally poor to lacking and bedding crude to indis- that cap many of the mountains, and overlie earlier vol- , suggesting aerial or mnindflow deposition, although canics In places however, beds of the Truckee inter- l better sorted and stratified beds suggest rework- tongue with either or both the underlying and overly- by streams. The beds are tilted 30° to locally 70° ing volcanic rocks. (Gianella, 19.30, p. 73; Thotupson, commonly are closely fnulted. Poorly. exposed 1953, p. 55, 56, and oral communicatiotn, 1952). e tufR and diatotuite, which are considered the Fossil florula from the Truckee formation at several ir part of the Truckee formation, locally overlie loenlities west of the Carson Desert have been inter- ssediments on the west side of the White Throne preted as enrly Pliocene by Axelrod (1950, and in attains, and thicken westward into thIe Desert Thompson, 1956, p. 56). Calkins reported (1944, p. ntnins. 23) that K. E. Lohman studied the diatomis and R. W. be Truckee formation has not been identified in the Chaney the fossil leaves in the Trmckee formation in ejug and Cocoon Moulottnins, but the tuffaceous Long Valley, 7 miles northeast of Virginia City, and s in the lower unit of the flnnejug formation (p. agreed that ttese beds date from near the Miocene- there may correlate with it. Zone 6 in the type Pliocene boundary. Yen (1950) determined tait mol- of s.,,J-9 ~mo.--0 *0pl-i -,, -.oift 04 I., M.M, .,,d .te oga-sd ; *Io-t0 T-ka. f-i (light eo!.4) 1. ..Fw.-d(o-p~t see, to-aly m.,nOI h, ,ettso-t)~. C.-tnre White FTh-, M'.t..11 A onl of the Bunejttg formnation (table 10, section 54) lusks from near While Plains (lHuxley Station) siding, roe,,,, -.04 ..4 g9oo-4o T,,-t., t~,o~o,ypit,, o thl. r-l..t U. White ITrla Mo.to..t.~ Dam icitlarly resembles thie Truckee formation it the 27 miles nortit of Fallon, were Pliocene. at. a Un.ytat.. to Baoo ., o,.ua ttog~ tow ."0 5.5. M1,. moPIt." ontan and White Throne Mountains; moreover, ,e pyrocinstic matter is a widespread minor con- StnsUVo rORMATION tent of the Truckee in the White Throne Moun- The most extensively exposed bard-rock unit i; a s, attesting to contetuporaneotis nerariwy andesitic series of baIsalts and andesites overlying thIe Truckee 4 1AILS LASONTAi: osotoor, CARtOM D9M, llD. uRauCrUnaL nATRUi OF PGOaw-UM MGUPer"AbCTS Ao namation. 14is here NannAthea lneoJug formation, The loweir unit he. Considers" Imatserbeddd ta5 ilk sanpervuL VWZA"VI of Individual displaoeent, elthogh a few have * tm whom three tu- free ti. Bunjeg MOUt , iN Wh it if Wm as. the Bumejug and Cocon Mountain. Comoeaoi orlunreaoflet ispacmet.They hare ptemded " ninh " 2 pert" the High-sagle norma faulting dominated dt stling, _mro nl IV* V med The typ locality Is the v t fac of the 4,04- fecwem oMW agete an more widespread hosogiAt tatf, tubnccia.._ d defosmation. The older Tettiarocks more than W, whic'generally is eppaita lot mountain Ite soth-ctAl Ilnsug Mountains, total a. They conist of Tertiry rocks, indicting mad rey a gravel tha is -wMLmy fad than the younger he the dip of th faul, resuling iuk repetton us ad 14,T. 17 NlL. 0B.(table 11,osctlas 54T) som e letivey aw of pumceouS to some degree. Ite immolted several ags of Tetiery fauting. fut nrfcs le fosmation is PUOOMe d posdsibly esrljr 11.. faults ar "posed, however; ms esposed of bed~s Stie.and grove on th middle of the mposed lower uit (unit I in "W the elder mily an p pat"gsee showingtha dspeo-t minage. the lank that OWtthe hard rc unt ar of postaanejug eiwvo fint siae relbimvely ist-lylog to UT, malt 6 ln section I5T, and unitS in section OT, wes maydip li Mos faults tted no.1k and -Them pree-Paineo and bhec of Quatenuy, Man peshape moderIatly tid pp 4g, e0 is thick, that taleb 0) is the tl4-e (-S0 ft thick), most per- nrheat in the eae1 Leoea Mountin.tmts lets Plisome ag., es &Wd "in the While Throma MiNelm sefasof seves hudrd et ef loca sitn, an hutcord ; its upper par is moty Oidmts wfderso commonly with pronounced magular macon. reddish ( pial, ta, mad eaege, ad it. lwer put i Wyneha Valley, the Eaglnes Houe irma, Naishow older rocks (f mosty whilt to light. Silid* Sew am local inawr Mountain, and th pan bewee Rainbow IMentel mtiy en theTrouaba foimation ma th bisle of Rainbow vmanaisin the old and the faulting a beded wimh ; in the otherm Safteju Mountains sad the S witer Riup apparently wo SUllevated 4). pitoef the initial lowf m Uiited ad alteed rck unit. I d fault. ir deposition (p. The upper two tufaceous soues, several letd to 2Smet Ia eat palu- jug deformation; t^m_ ing du=ng teaerly pitt of Benejug identify seoifically, aN their displacm by the postnTrackes mrface en which the youngest thick mad lobly shlent, ire light red, pink, n, and dlcui to maue ire otructurally higher thin idjonn pert. Of s the depos eil - &in owing to several episodes of ractivati. relief. This fonns- grey. Localy In the Cocon Mountains a thin fourth ar - the LhUontn Mountains, end the statirepy Oa were laid hed generally low of steep halts of the N. Ir E, due aulted thin the iesbtee tw eupper two and thelow sme. The ebundance structure of the Bknjug formation suget tbha lJv generally is muchr le, closely 15-* IV. sets ned their esprsity elm- soes may represent tongues of the north, Ad N. of tt formtion never appreciably inundated tese. ruke. 11Thetuffaceous where suggeste that these sets wer dominant between Many feeder dikes sad a few Tents have been idmnti- Truckee formation, but this cannot be pred. A sae of intra-Bomejpg faulting along the moethuest- the deposition of the hesaft of Rainbow Mountain sad in indicated by at The dihes are armost bundnt along the uajor Theupperpart ofth4Bunejugformtion..te upper mesh so side of the Lahoatan Mountains Most flows ms 10 to li of the overlying decite. They form in Intricate vents, numerous feeder dihie, ssd of post-Trckee early.Bunejug fauling (p. 15). unit-is entirely oivine belt. generally lee least tbw volcanic red end pur. of intersecting and bifurcating shears heers in the lower puat of the Beejeg aents*ncircular to irregular, steep walled, have tog thick, black and dark pay to locally the balk into local minor vesicular, end have scoriaceous tape ad V.i than 200 lest apart; these have broken the Rainbow Mountains the lre limpof deatn lava (volcanic plus) or chaotic &g- ple,generally motly dip westward it formation. in of plagioclase narrow homoclina blocks that of thsa tread seiely due north to N. W X. rt of _cricousvarkolored b klt,aud ar bottom, most have emaUl phenocrysta generally US and W. Although faults dlirie Loaly the flows re separated by diso- angles of 1V to 701, NdWa exoeptionally log A straighL ly intruded by dikes. They rnu in diameter ad fiults are smell and discontinuousb same tinuoua beds a few feet thick of skltia tel md tuft mot of te In the Bunejug and Cocoo Mountain, faulting of 900 to SVW fet; the largest is in the Cocoon bhs traed for 1 atR te lls. Ale apparently of ares. Tbh baroi (or rarely of bultio gravel sand semd), which hive this age moderately tilted the lower paut of the Ieb.- rountaims at tlb south edge of the map tI the sem age, but vary subordinate, are small _bee di an enta Sae o are red, red brownb,prpamad blac. This unit rsae jug formation nt a hoteocline. The faulting we INonin IhiksetL whe trending roghly eswerst. u an *rdcomnonly is amle whetr they an lack. In h from lee then SOto about ISO fest mid in vhswidepoeitioasshowu by in lower umit. In placs a *am The dacke ot BRinbw hflla inmt lee faulted faults and the ieseing Some eighlbndrwhere the leais of the Hunojug awe extensive thal te the EAgle reasing displacement of the separates it frnt the lower uilt; sad mhered than the underlying boelt, aud scti Wm renow very thin or abhent probably were at attitudes ngula unconformity are even less dip oTheft kblack, donwrd in the the two units in grade. House rhyolite end Trucke formation inth Bousing UMes. greet to he inundated, for sample in the Eagle eloketewu tbe japms betwee 1I Many ot tthe.fults mut heb f faults trend mainly northward via Interbedding, md is cneformable. defrmedmiltered. tais, bet diverge w e the Cocoo Moontais. ouse-Wysmihi Ymlley-Riinbow Mountain are. tional, pro-Trurkee ag but bo evidence for their specific age lave in the lwe piut of the fuhethe A and tJbh* B ej oeration lies Displacements rne from a few feet to lallry sler Th wee recognised. r unit-re much mre variable in testure mad yielded no fan* heembits age ca only be infered. hundred fst. So of the faults se to he rena sad thinb thos of the upper par. They rag itre Because the Trck"e formation in early Pliowee rAiLy. Or oea-VauCXM M nann neasasog MMn unis Bannjug poseibly interfinpgrs with sad to light ry, greenish gny, emd re, pid4and the l er Truckee formation isclossly sheared and S5kUCIfLJALI EAIURtS OF PQW4WNStltiM frem overia it, the Bletjug formation is considered to be Uost of*he inb; from dometo highly eoerieeoum; sad moderstely tilted by highienle nal huls, &a perlite) to ponpyritfi with Ato Plicere, perhape nuging to early Pleistocene in its I (obsidian ad touch _mre n u s Nd upperpart. thee. fains ire penerlly Spercentphesecrysts. Theirgroeadmargnenrallyin the tiling greater them in the lDusjng formation. naaansitn-suomPAVLTIU pheintiofebgrained, butafew meaiumd irned Andeelemad haah ae widespread in wuteri is the Bunjug fotmation in II. Whn the lower unit of the Buojug fenatien ad wsry tured. Some flows eshibit a strong Irera; they oeemble unenfomity geneally relations simier to the slheut, a pronounced angular pest-e ty entorted structure tlh resembles bedding bat thoogy m have stratigrephic II the-upper wuit of thin formation from the ot of thebrec faults mapped afkof Jfrmation or edimnty unais more or Ile_ sepeorte ly does parallel Sow margins. Individual Trucks and whre the lower unit of the Bumatig in ug Lutp-aimulo age. They displaoe the Iomijog thick. coneertive with the Trachea. The lower unit of the Trucks., ea from several flst to mar the 40 lest thic, this unit is on, faulted an tlted thee the Sornmation (including th upper unit where psesat), asem"cuneedy eamanst he traced unejug may enmet with the Loutowe formetiob .1 fMorms il lows er lavm lashing of the lower yet they do ot eatead Into the overlying Pamiot the Knickebacker andeuite in the Viginia upper owe. The intra-Buneiug oethen I eremileeeve whegoodexpeauteoccr. and perhape unit may have been bmyhnoes with faultig dated Sloe aned may be largely or entirely of Quaternary age. quadrangle (Thoompean, lIp 137.48 ); th pper lower unit 6loaly asent, but is much s 40W City as pet-Trucks. pse-hlunejug where the lower unit is The poot-Bnejfg Pee-Mate faults epperedtly re- mi*h errelee inpert wiO the deformation Useae zetis exposed in the Itinjug and Couen ountain., u ofh the luneug itsing. eebsr climxe of bo1t 25 fert in the Sdelaend Eata otoeni, sad McClella Plek divine basalt in thesums qua dragl. In Ihe Lehoulas and White Throne Mountains, this fron that of poml.Tmtkee end early Bunjug eI. rewricted omnrhet lee. in the hite roe 71u e mud th mpsn infesd het thse itra in ge fr faultingW;br*ken muchofsheTrachee formation into Falms of intn-lunjug age are priatieclly itillwateriRtg Plopi to Ilsietore. * giant bheria. The hubts mm high engle and sos to she lower (andesiticend basiltic) pert of the ilvN_ mal, and geneally haveonly a few fete r few inches jug formation; te upper (divine besaft) prest gwrt QUATERNARY STRATIGRAPrsY 17 LAKE LAHONTAAN: GEOLOGY, CARSSON DMSETr, NExV. interior faults were found, beneath the southern and southeastern part of the main Ily is affected only by post-Bunejug faults, and in cially the stag of development of the mountain canyons w ment. No mappable although this area was much affected by post-Truckee basin (Carson Lake, Stillwater Slough, and Stillwater laces the two parts are separated by an angular and pediments (p. 22), shows that the last main in- two-thirds and intra-Bunejug faulting (p. 15). Lakes areas). Forexample,.an oil-test well nrconformnity. terval of basin-and-range deformation took place after end of Rainbow At Rainbow Mountain, post-Bunejug pre-Paiute of a mile northwest of the north The post-Bunejug pre-Paiute faults exposed in the deposition of the Bunejug formation but long before at about 58 feet, yet a faulting is difficult to assess because the Bunejug forma- Mountain penetrated basalt Mountains have throws generally less than 100 feet deposition of the Paiute formation; and (2) well Ytdga the northwest, in sec. 28, T. 19 tion is absent, but the faults separating the horsts 500-foot well 4% miles to commonly only a few feet) and little or no gouge, suggest deep 611 of Quaternary sediments of pre-Lake sediments, (undelain by the basalt and dacite of Rainbow Moun- N., R. Go E., penetrated only unconsolidated recciatied areas, or hydrothermally altered zones. Lahontan age on the basin aides of the buried fault Air Station is tain) from the grabens (underlain by the Truckee and a well at the Naval Auxiliary he faults are normal and steep, rarely dipping less carps. reported to have been drilled to almost 1,700 feet in tan 60°. Tiny reverse faults, seen as side shears asso- Two main episodes of faulting apparently took place, formation) probably had much of their displacement probably was accom- unconsolidated sediments. iated with larger normal faults, are rare. Displace- separated by a period of relative stability, in post-Bune- at this time. Their displacement of earlier faults in the ients are almost entirely dip slip, as shown by grooves, jug pre-Paiute time. The pediments at the edges of panied by minor adjustment QUATERNARY STRATIGRAPIY interiors of the main blocks. From the eastern edge of trise, and alinement of fault traces Strikes are very the mountains are younger thain some marginal faults OF STUDY House is a METHODS iverse, particularly from one mountain area to an- and commonly extend across these faults without dis- Sehoo Mountain to the vicinity of Engles only part of the move- the late Quaternary lakes in the ther, but the predominant strikes are N. 30' E. to N. placement: however, these pediments terminate basin. closely faulted area. Probably Early research on age. Relatively on their geomorphic 0( W.; other prominent faults strike N. 50'-60' E waerd in fal!t scarps (p. 17), indicating that large- ment is of post-Bunejug pre-Paiute Western United States centered are exposed bars, and deltas, 'lie diverse strikes may reflect the position of the Car. senle faulting occurred after the pediments were little tilting has taken place. Few faults features, such as beach terraces, spits, Lahontan Mountains, owing to the stratigrmphy. In the presentstudy, on] 1,ake quatdrangle being just south of the boundary formed. As the pediments all lie at about the same in the rest of the rather tIan ot their sediments. in the Lake Bonneville area by etween dominantly northward. and northenstward- general level, the faults that are younger than the pedi- general cover of surficial and in recent studies that extends and by Bissell (1963) the rending and dominantly northiwestward-trending menits probablv depressed the basins without selective In the small part of the Stillwater Range Hunt and others (1953) strike northward rather than geo- ainges and basins (Spurr, 1901, p. 258; Gianella and uplift of individual highland areas. Similar large- into the map area most of the faults emphasis has been on stratigraphy are down units have been mapped 'nalaghan,1f134,p. 3,18). scale faulinre both older and younger than the pedi- although a few strike west. Displacements morphology; stratigraphic occurred. licustrine and subaerial Much larger faultsuand fault zones of post-Bunejug melts, has leen noted on the northwest side of the on the west and south, and little tilting has instead of landforms, although terraces, bars, and spits wre-Paiute age border highlands that abut the basins. central Hum5boldt Range (Jenney, 1935, p. 58, 65-08) landforms were studied. Shore CONFITGOUATION Or TEE BEDROCK FLOOR OF TPE stillstands, but the morpho- These marginal faults are largely concealed by detritus, and on the east sides of the Virginia-Flowery Range show lake maximums and EASIN alone, even those of yut their existence and dominant role in outlining the aid Pine Nut Mountains (G. A. Thompson, oral corn- logic relations of these landforms do not give full informa- >resent basins and ranges are inferred from the follow. mutt icat ion. 1?50). A little information on the configuration of the bed- the younger lakes, generally of development or other de- ng criteria: (a) Bedrock structure is sharply truncated rock (pre-Qusternary) floor of the basin is available tion on either their order FAVITXG IZNSPrUleC ARtZAG the lower limits of lake long the mountain fronts; (b) the mountain fronts are from reconnaissance airborne magnetometer traverses tails of lake history, such as irominent secrps having fairly straight alinement md In the Bunejug Mountains, faults of post-Bunejug (p. 16, 22) and well logs. Several areas near the edges recessions. record, however, is difficult to study. faceted spurs in places; (c) the marginttl faults are ex- pre-Paiute are are particularly numerous. Most strike of the basin are known to be underlain by pediments The stratigraphic to trace and correlate Dosed locally, they parallel the local mountain front, between N. 1'), W. and N. 25° E., are vertical or dip cut on Tertiary rocks and buried by Paiute and younger Many of the units are difficult and their lith- raveInrge displacement and commonly wide zones of steeply westward, and cut the Bunejug formation into deposits. Abrupt magnetic discontinuities and deep- because of their rapid facies changes horizons and ilattering, and some show hydrothermal alteration; slivers a few feet to a third of a mile wide. Most of ening oi the younger sedimentary fill suggest that the ologic resemblances; good marker i unconsolidated (d) airborne magnetometer traverses show sharp mag- the fault blocks have been tilted eastward so that the pediments generally terminate basinward in buried diagnostic fossils are scarce. The and good exposures are sparse aetic discontinuities one-half to 3 miles basinward from upper flows of the Bunejug dip 5' to 3a5 E., but blocks i' fault scarps. In places the buried pediments extend deposits slump readily rarely expose Lhe mountain fronts.' These discontinuities suggest on the east side of the mountains have been tilted west- 1 basinwrard for considerable distances before they are and discontitnuous. Highland washes 5 to 20 ibrupt thickening of the sedimentary fill at probable ward. The west and east edges of the mountains are 't thus terminated-about 2 miles from the front of the more than 50 feet of section, and commonly only '9.' that their fault scarps. particularly closely sheared and in places hydro- Desert Mountains, I to 2½ miles from the Dead Camel feet; moreover, they flow so infrequently .4 The lowlands are mostly A rough measure of maximum displacement of the thermnally altered, suggesting that the mountains are Mountains, and I to 3 miles from the east front of the banks are badly slumped. deflation marginal faults is the difference in altitude between a compound horet. -t Cocoon lfoUntains. devoid of stream dissection, but the scarps of sections. The exten- the highest beds of the Blmejug formation adjoining The Cocoon Mountains have a haphazard fault pat- II The magnetometer traverses also show, however, that bains locally reveal fairly thick and drainage canals, locally a mountain front and the bedrock floor of the basin tern but northward-striking faults are dominant. in a few places the bedrock plunges rapidly to depth sive systems of irrigation of more than curve considerably, and many along buried scarps close to present mountain fronts, as deep as 15 feet, have made particularly good and adjoining this front. Tota Idispincements AMostof the larger faults I 1,500 feet, without allowance for possible warping, are radiate from volcanic centers. The faults in the interior and here pediments are almost lacking. The only cont iluousexposures. for this study are similar to those indicated along the north and west sides of the White are relatively small and comusonly less than 50 feet and examples in the map area are along the north front of The techniquesaused geologic mapping: separating the Throne, Bunejug, and l.nhontan Mountains, and 4,000 rarely more than 100 feet in throw; only along the the White Throne Mountains antd the west front of the used in general (rock-stratigrephic) units, feet or more between the Stillwiwter Lakes and the Still- northeast and east sides has much tilting occurred, and Bunejug lountains, where buried scarps are associated deposits into mappable of the units, mapping water Range. Two criteria show that most of the mar- this tilting was eastwsrd. 1,arginal faults are con- with the Wildcat fault zone. determining the superposition and vertical changes ginal dispIncement occurred in post-Bullejug pre-Paiute cealed except for a few poor exposures north of 41645 For the interiors of the basins, the magnetometer their contacts, and noting lateral as well as the altitude range and strati- time: (I) The geomorphology of the highlands, espe- peak. data suggests that the bedrock floor lies not closer than in lithology, several hundred feet below the surface, and well logs graphic range of unconformities. Because fossils are forbore i-nrts The Whi:e Throne Mountains probably are bounded pubrslb4 dat 'a ite fet abeat 251 *I suggest that it ranges in depth from several hundred meager aid relatively nondiagniostic, the deposits had to n-ns I.t-r Prad I 1t12 mIt, Opan of an trrantf pre-Paiute age, by marginal faults of post-llunejug rocks. ,..t, rsoad n.rlbtoOtb c id .,rvo, tbr Cs-.. s.,t.4 la, s1ty to more titan 1,000 feet. The floor seems to be deepest be studied as essentially nonfossiliferous 1945 by lbMu.8. Guotoeol 8-ra. and a few faults are exposed onfthe east front and pedi- LAKE LAHONTAN: GEOLOGY, CARSON DESERT, NEV. LAKELAEONTAN: GEOLOGY,CARSONSfTRATIGtuPHYDI~~~~~~~5ERT, 55KV.~QUATERN5ARY 19 Gullies, canals, and other places exposing the best sediments, uneonformities representing subaerial ero- Fallon formation, are subdivided on the basis of their which locally may overbalanea the effects of other soil- deep sections were given principal attention. The sion, soils, mud cracks, sand dikes and dikelets, root intertonguing lake and subaerial deposits. In the forming factors. stratigraphic units were then mapped across interven- casts and molds, land-plant and marsh-plant remains in Sehoo and Indian Lakes formations individual mem- Each soil maintains a eonsistent age relation to the ing areas where surficial materials are poorly exposed, plaice, and land-animal remains and coprolits. Sub- bers or tongues are single units of either lacustrine or associated deposits, akin to a rock-dtratigraphic unit, mostly by using soil texture; this was occasionally aug. aerial exposure, or at least a major drop in lake level, tsbaerial sediments; in the Fallon formation several and is defined on the basis of this relation. It is given mented by auger holes a foot to several feet deep. In also is suggested by shallow-water deposits such as lake intertonguing Incustrine and subaerial units comprise a local geographic name independent of the soil namea the more detailed mapping of the Carson Lake and gravel or alpgl tufa interbedded with deep-lake sedi- each member, and the individual units are locally differ. of agronomic soil scientists, and a type locality ia des- Stiliwater quadrangles and the special larger acale ments. It is critical to determine the vertical range of entiated as lacustrine or interlacustrine (pls. 3, 4; fig. ignated. The soils are not vapped, but are designated maps, the surficial deposits below the highest shoreline each unconformity or recessional unit; merely identify- 25). The members, tongues, nnd units generally are not in many of the atratigraphic sections in table 10, and of Lake Lahontan were differentiated only where they ing one at a single altitude commonly gives no indication mapped but are designated in many of the stratigraphic are described in detail in the soil-profile sections in consisted of reworked or transported (introduced) sedi- whether it records a break between major cycles or rep- sections in table 10. table 11. ment differing distinctively in texture, composition, or resents only a minor fluctuation. :~- Each formation, member, or unit includes several In the area mapped for this study, five soils were bedding from underlying material and were at least Unfortunately, many exposures do not show the i.. lithofacies. The lacustrine units generally consist of found to be sufficiently well developed and widespread a foot thick. In the less detailed mapping of the Fallon breaks between different lake sedimentation cycles Inke gravel, sand, silt, ciny, tufn, and locally a little to merit formal names (fig. 4). They are the following: and Soda Lake quadrangles, however, only deposits clearly; commonly the breaks appear as diastems be- volcanic ash. The subaerial units contain alluvium Cocoon sol.-the oldest sad most strongly developed more than 3 feet thick, below the highest shoreline, wvere cause many represent short intervals without much ero- and coltuvi-m, eolian sand, and locally, shallow-lake and occurs onl deposits as young as the uppermost beds generally mapped; moreover, the widespread cover of sion, subaerial sedimentation, or soil development, and, sedliments. On the quadrangle geologic maps, subdivi. of allivial gravel and colluvium of tImePniute forma- eolian sand of Turupab and Fallon age was ignored in in plices, even without much change in lake sedimenta- sion of formations generally is by lithofacies alone. tion (a-b, relict occurrence; b-b', buried occurrence, order to simplify map patterns. However, in places tion above and below. Tracing the subaerial features is fig. 4). deposits tlinner than I or 3 feet were mapped if they more difficult toward the lower parts of the basin so the SOILS Churchill soil.-strongly developed, intermediate in were deemed particularly significant. Above the high- lake minimums were at least as low as determined, but development between the Cocoon and Toyeh soils. It est shoreline, in all the quadrangles, DEFINITION AND OENERAL FEATUsES a 5-foot minimum may have been still lower. lies on deposits as young as the uppermost subaerial thickness was used in mapping the surficinl sediments Soils of several different ages are associated with the beds of the Wyemanli formation (b-c, relict occurrence; to minimize STRATIORAPMC USAGE the colluvial cover, and because these sub- late Quaternary sedinients. The term 'soil" is restricted c-c', buried occurrence, fig. 4). The soil is not evident. aerial sediments were considered less significant for The Quaternary sediments are differentiated into in this report to meal, a profile of weathering, or soil where it developed on relicts of the Cocoon soil because deciphering the Inte Quaternary history. three main rock-stratigraphic units-Paiute formation, profile, consisting of a layer of materinl that is discern- of the st ronger development of the Cocoon. Several Lnhontan hundred stratigraphic sections were mens- Valley group, and Fallon formation-by ibly weathered by chemical and physical surficial Harmon School soil-retey weakly developed and uired in order gross differences in lithology. The to record the thickness, areal extent, and Paiute formation agencies. The soils range in degree from very weak to therefore occurs only as a buried profile because in facies changes awnd consists of alluvium superposition of the strntigrnphic and colluvium older than Lake La- very strong. and each maintains the same degree of relict occurrences it is masked by the more strongly units. Information onl buried deposits was obtained hontan. The Lahontan Valley group is a succession of developsient relative to the others wherever it occurs. developed Toyeh soil. by augering,trenehing, intertonguing deep-lake, or digging pits; 150 aiger holes subaerial, and shallow-lake The more strongly developed ones have vertical zona- Toyeh 8oil.-moderstely developed compared with were put down sediments by hand to depthis ranging from 6 to 30 of Lake Lahontan and early post-Lake La- tion into soil horizons, corresponding to the zonal and the other soils. It occurs on deposits as young as the feet in Carson Sink and other nrens of poor eaposurea. hontan age. The Fallon formation contains the younger intrazonal soils of soil scientists, but the weakly de- uppermost beds of the Turupmh formation (c-d, relict All subnerial available driller's logs of wvells were collected. sediments and the shallow-lake deposits with veloped soils have only incipient indistinct zonation. occurrence; d-d', buried occurrence, fig. 4). It is not which they intertongue. Selected stratigraphlic sect ions, soil-profile sections, and Zonal soils are those whose most important characteris- evident where it developed on relicts of the Churchill well logs are given in tables 10, 11, and The 12; many others formations are differentinted by general vertical ties reflect the influence of climatic and biologic factors and Cocoon soils owving to the stronger development have been published separately (.Morrison, !1958n). and lateral differences in lithology. One formation acting on well-drained parent material for a long time, of these soils. The pattern of Lnke Lnhontan and younger stratig. may be characterized by deep-lake sediments; nnother, whereas intritzonal soils owe their distinguishing char- "L" Drain sofl.-found on deposits as young as the raphy and the history wverepieced together from many hitertonguing with it, may be entirely subaerial, wnid acteristics less to climatic, biologic, and time factors second lake init of the Fallon formation, and so weak- key localities by mnapping a large ares. They prohnbly still another, overlying the first, mny consist of inter- than to the effects of parent material or topography, ly developed that it is not distingkmismable where it could niot hIve been worked out reliably by merely tonguing subaerial and shallow-lake sediments (fig. 1, mensuring isolated strntigrnphic sections vithout map- pl. 12). The formations are rock-stratigraphic units, ping the deposits in the intervening areas. differentinted on the basis of lithologic chnracter nid Analy*is oJ lake Aidory-The primary objective of not on either inferred climate during deposition or as- the study was to decipher the lake history. The Inke sumed age differences. Their main differences are be- maximinns ansI main stillstnids were sletermitted by tween lake and subaerial sediment relations and the for- mapping the deposits of earl, significnnt, Inke cycle and mations are thus most clearly differentinted where lake observing their relations to shore fentures. The lake beds occur. Above the lake maximaims the formations minimums-much more difficult to determine-vwere are differentinted by lithology of alluvial gravel, by found by noting subaerial features developed upon or proportions of alluvium and eolian sand, and by soils, intercalated bet ween Inke meimenits, and tracing those but their boundaries commonly are less sharply defined. of a given age to their lowest altituide limit. These Two formations of the Lahontan Valley group, the subacrinl features include alluvial, colluvial, or eolion Slhoo and Indian Lakes formations, as well as the F..e.. 4.-Oi~z,.a ,haeat limetee sfd Mlatig.pi,i eaalma ( lb,. afli.. aI. isle OQseW.-w is it, orsan D-tsaf - QUATERNARY ITRATIORAPHY 21 LAKE LAHtONTA5K:GEOLOGY, CARBONS DESE~RT, NEV. each soil has only a single facies; however some of states: dry, moist, and wet. Degrees of consistence are Vesicuaxr (A) AorizonL-The uppermost or A hori- and reloped on relicts of the older soil, (d-e, relict occur- younger soils have a special local facies developed in determined: (a) when dry, by resistance to granulation zon is not t~ueusual type found in soils of more humid the LCe:C-e', buried occurrence, fig. 4). poorly drained areas. between thumb and fingers, and are described as loose, rhese five soils are the only ones with true soil pro- areas; here it consists of sandy loam, loam, or pebbly soft, slightly hard, hard, and very hard; (b) when s that have been recognized. The deposits that are sandy loam that is partly leached of clay and carbonate DRsCraIPri'vi TICRMsINoLoGY moist, by resistance to rupture between thumb and of these roils are 'and has a vesicular structure. This horizon, called ermediate in age between each Soil descriptions in this report accord with present fingers, described as loose, very friable, firm, very firm, of coeval soil development, the vesicular horizon, is lacking in the older soils. It void of any evidence practice by soil scientists in the US. Department of and extremely firm; and (c) when wet, by pressing weathering (ez- has a sharp lower boundary. ept for two horizons of incipient Agriculture, as outlined in the Soil Survey Manual between thumb and fingers, described as nonsticky, one of thinolite reces- Oxik (B) AorizonL-The middle horizon,here called mely weak soil development), (US. Dept. Agriculture, 1951). As the terminology slightly sticky, sticky, and very sticky, and as nonplas- Eet7a age. the oxide horizon, is characterized by enrichment of nage and the other of middle is unfamiliar to many geologists, the definitions are tic, slightly plastic, plastic, and very plastic. it has been buried by clay and iron oxide and generally by losw or absent car- Each soil occurs both where summarized below. Boundarace.-Boundaries between soil horizons are it has remained St the bonate. It is present in *11 the soils although in the anger deposits, and where Color.-Soil colors refer to the dry soil, using the described in terms of width as: abrupt, less than 1 inch since its formation. The former is weaker ones it is incipiently developed. The B,. or B. id surface ever Munsell soil-color system of notation and nomenclature wide; clear, I to 21Ainches wide; gradual, 2½ to 5 a buried soil, and the latter a relict soil. The subhorizon is marked by accumulation of calcium car- [led (U.S. Dept. Agriculture, .1951, p. 194-203). Many inches wide; and diffuse, more than 5 inches wide. soils of the Carson Desert bonate in the lower part of the B horizon, and is tran- ae strongly developed Nlunsell soil-color names differ-although symbols are Soil boundaries are described in terms of shape as: no secondary profile modi- sitional into C,, horizon. en generally show almost the same-from standard 'Munsell color names that are smnoth, nearly a plane; wavy or undulating, pockets and, in the case of the Calcareowe (C-.) orizon.-The lowermost true soil ntion, other than local erosion I used in this report for describing geologic deposits are wider than their depth; irregular, pockets are ter soils, development of a younger soil horizon in horizon, here called the calcareous or C<. horizon, con- deeper than their width; and broken, parts of the of calcium carbonate. It occurs other than soils. ? several inches of relict occurrences (p. 25, tains an accumulation upper Tezture-Soil texture refers to the proportions of horizon are unconnected with other parts. ). The absence of secondary modification in the in all the soils of this area. clay, silt, and sand below 2 mm in diameter. The prin- General Merins for degrees of soil detelopment.-Rela- of the soil profile is shown by the profiles Below the true soil profile are the C and D horizons in part cipal textural classes, based on the relative proportion tire degrees of soil development are expressed in this uneroded relict soils being virtually the same as of the soil scientists; these designations are not used of each, are: sand, loamy sand, sandy loam, loam, silt report as very strong, strong, modernte, weak, very ones of the same soil. The weak soils, however, in this report. The C horizon refers to unconsolidated tried loam, clay loam and cliy (U.S. Dept. Agriculture, 1951, weak, and incipient. These designations express the youngest, are preserved only in buried mantle, either residual or transported, which may be cept the very p. 205-223). sum of different characteristics of the whole profile- eurrences; persumably they were altered during sub- the parent material for the soil and the D horizon is Struecture.-Soil structure is an especially diagnostic thickness, color, structure, consistence, and pH-and quent intervals of stronger soil development wherever bedrock. property. It refers to the shape of aggregates of pri- accumulation of clay, iron oxide, and calcium carbonate ey were relict. In the Carson Desert area each soil horizon has simi- mary soil particles, called peds, which are separated in individual horizons. Differences in degree of devel- The stratigraphic record shows that each soil is of lar general characteristics wherever it occurs, although on from each other by surfaces of weakness. Their size, opment are evalauted by comparing soils developed distinct geologic age, separated from the other soils in soils of different ageit commonly differs considerably I vary widely with different ge- parent material that is similar in both lithology and r intervals of negligible soil formation. The geologic in degree of development. shape, and distinctness factors. The following terms describe the soil- permesbility, on flat or gentle well-drained slopes. ,e of a soil is determined from that of the youngest Good profiles of the older soils are restricted to loca- netic of the Carson Desert area: Columnar, One of the best indices of degree of soil development posit or erosion surface on which it is formed and tions exceptionally well protected from erosion. The structure types vertical prisms, having small horizontal in the Carson Desert area, both for buried and relict at of the oldest deposit which overlies it, in as many upper horizons are particularly liable to erosion, but arranged in compared to their vertical dimensions; ver- soils, is the thickness and density of calcium carbonate fferent environments as possible. the C.. horizon is resistant where well developed. dimensions defined and vertices angular; rounded accumulation in the C-, horizon. This horizon com- The more strongly developed soils are among the tical faces well r.t columnar but without rounded monly is a better index than the oxide horizon; the ve- ost useful stratigraphic markers in the Inte Quiter- CLL55aWICATSON caps. Prismatic, same as caps. Platy relatively thin horizontal plates. Blocky, sicular horizon is not a reliable index. kry succession. Once the geologic age of such a soil Soil scientists in the United States classify soils into blocklike; blocks or polyhedrons having plane or curv- Is been determined, relict occurrences can be used with several categories. These are, in order of decreasing onoUPH *ing surfaces Granular, hard or soft but cohesire small GREAT SOIL surance as well as buried ones; relict occurrences are soil order, great soil group, soil family, soil magnitude: aggregates, angular or rounded. Vesicular, character- f far the most common and therefore the most useful. series, and soil type. Iuuthis report soils are classified CadeiBrotOnsoils.-Calcic Brown soils are zonal soils ized by spherical or egg-shaped cavities one sixty-fourth Dils are practically time-parnilel (p. 109), and hence according to great soil group, in preference to the characterized by an A horizon, 0 to 8 inches thick, partly to more than one-fourth inch in diameter. Dimensions iey are useful for time-stratigraphic correlation and categories of soil series and soil type which humus and partly mineral, brown to brownish gray, smaller of the structure types are indicated by adjectives such Ry be used to define time-stratigraphlic units. Strati- working units of the soil scien- slightly acidic to neutral, and partly leached of clay and are the fundamental as very fine, fine, medium, coarse, and very coarse, raphic attributes of soils have been discussed by The great soil group is most useful for the surficial l sesquioxides; a B horizon of clay and sesmpuioxide ac. tist. following the specifications in the Soil Survey nManual ichmond andFrye (1957). geologist because it stresses general profile characteris- In, cumulation, 4 to 24 inches thick, that is brown, pris- (U.S. Dept. of Agriculture, 1951). Degree of develop- tics, rather than minor differences caused by differences matic to blocky, and slightly acidic to mildly alkaline; son. PrOFIL ment of these types is denoted by the terms "strong," material and local factors. The minor differ- and a C.. horizon of carbonate accumulation, 11 to A soil is characterized by zonation into soil horizons; in parent "moderate," "weak," and "structureless" (or "massive," are irrelevant to the differentiation and is pale brownish gray to nearly neaggregate of the several horizons is called the soil ences generally if coherent; 'single-grain," if incoherent). Thus, locally 10 feet thick, that !ofile. The horizons differ in color, texture, chemical use of soils as rock-stratigraphic markers. "modemnte medium columnar" means "moderately de- white, weakly blocky to massive, moderately to strongly Id mineralogic composition, structure, and other In an area having considerable range in climatctd veloped ecuninmiuof medium (20 to 50 mm across) size." alkaline, and gradational into parent materiel. TIhe two a soil of a given geologic age may pans from i roperties, and are more sharply differentiated with vegetation, Conaistence.-Soil consistence is the resistance to most strongly developed soils ih the Carson Desert area, others; such changes are con- icrensingdevelopment of the soil. one great soil group into separation or deformation of individual peds, and is the Cocoon and Churchill soils, have all the cuaracter- of a soil. The climatic The following three horizons occur in the soils of the sidered to be changes in facies described in separate terms for the standard moisture istics of Calcic Brown soils except that the A horizon arson Desert area: range within the Carson Desert area is small, however, 23 22 LAKE LAHONTAN5 GEOLOOl[Y, cARSON DESERT, NET. QUATERNARY STRATIGRAPHT LACUWRXNXX 55HrNT1S This is eviden't not merely from comparing the LAHNONTAN QUATERNARY NRMa-LAK ILAZONTAiWN in relict occurrences resembles the vesicular horizon of tan. PRE-l.AE above and below the highest shoreline, but also STRA'rlORAPY Gray Desert soils in being pale gray, lacking humus, and terrain Pre-Lake lahontan Lacustrine sediments of Quater- at the base of the earliest sedimeits of UUZ having a strong vesicular structure. This horizon prob- from the contact BAkA.LT OF RsATT5Z5S5A~i nary( f) age are exposed in a gully at the lower edge of which follows a ably is younger than the rest of the profile and not prop- Lake Lahontan (Eetza formation), the pediment between Sehoo Mountain and Rainbow only in minor details from the Basalt of probable Quaternary. age forms the small erly a part of the Cocoon or Churchill soils. topography differing Mountain, in the SE/4SEIs Sec. I2, T. 18 N, R. 31 one. Pre-Bunejug erosion surfaces are exposed volcano, Rattlesnake Hill, 1 mile northeast of Fallon. Oray Desert Seilh.-Gray Desert soils as designated present E., at an altitude of about 4,020 feet They consist of the mantle of younger Cenozoic rocks Rattlesnake Hill is a much-eroded cone 1 mile in diam- by the US. Department of Agriculture vary widely only locally where as much as 20 feet of partly consolidated lacustrine oldest erosion surface manifest eter and 200 feet high; it has several summits that sur- from the type soil of this great soil group, the Portneuf has been eroded. The sand, gravelly sand, and gravel (section 80, table 10) present topography is one of late-mature relief; a shallow crater 1,000 feet in diameter at the silt loam (Lapham, 1932), and overlap into the Calcic in the round locally showing caliche that is typical of the Cocoon than the upper part of the Bunejug for- center of the cone. The basalt is largely covered by Brown, Sierozem, and Red Desert great soil groups. it is younger soil; these disconformably underlie sediments of Lake mation and older than most of the pre-Paiute faulting, Lake Lahontan sediments and young eolian sand. It to the A restricted definition is used here: A Gray Desert Lahontan. These beds intertongue with gravel of which traces are locally preserved on the summit is mostly black to dark-gray flows that appear to have soil is generally intrazonal but in places is zonal, and it north that dips about 45 SE. and is part of a lake plateaus (fig. 3A). This surface seems to be better S low outward dips where they are best exposed, as in is characterized by: (a) an A horizon 0 to 4 inches spit or bar. The beds are unfossiliferous and their age preserved in nearby higher mountains enst, south, and the quiarries on the northwestern side of the hill. The thick, of nonhumic sandy to clayey loam, light gray to uncertain. Clearly older than Lake ILnhontan and the wvestof the area. The major erosional features of the crater is underlain by locally exposed basaltic agglom- light brown, weakly to strongly alkaline, friable, gen- Cocoon soil, they also may be older than the Paiute present highland topography postdate this surface, and erate-a brick-red to deep-purple-red chaotic mass of than is erally weakly to moderately platy but locally columnar, formation, for they are better consolidated hence are largely or entirely of Quaternary age. vesicular basalt blocks of all sizes in a finer matrix consolidated and locally vesicular at the top or throughout; locally a usual for this formation. They are less Pedimcnt#s-The earliest well-preserved extensive and some blocks of sandstone and shale. Pebbles of and con- layer of gravel, generally only one pebble thick, over- and less tuffaceous than most Truckee deposits erosion surfaces are pediments that have been cut on rhyolite, mnfic porphyry, and quartzite or chert also lies this horizon; (b) a B horizon having a slight to tain pebbles of Truckee lithology, so they are probably Tertiary rocks at the edges of mountains. The pedi- occur sparingly in the gravel of Iake Iabontan derived sliver moderate accumulation of clay and sesquioxides, 4 to 18 of post-Truckee age- The exposure is in a fault ments are mostly buried by younger deposits, but their from this area; their only possible source is from the the south. inches thick, brownish gray to light brown, slightly downfaulted, with respect to the Truckee, to upper frhines nre locally exposed in washes. Their basalt, indicating that they were carried up from below hard to hard, blocky to prismatic, neutral to mildly This exposure is the only one of shore deposits or buried extent is revealed by well logs and by mag- in the vent. alkaline, and generally gradational into the C,. horizon; shore features of a lake older than Lake Lahontan, de- netometer traverses (p. 17). They developed in post- The basalt flows prohably were extruded by quiet and (c) a C,. horizon of calcium carbonate accumula- spite the fact that the McGee and Sherwvin Glaciers in Bunejug pre-Paiute time during an interval between from the Rattlesnake ltill vent. The ag- tion (and locally some calcium sulfate accumulation), eruptions the Sierra Nevadn were greater than the Tahoo and climaxes of basin-and-range faulting (p- which was drilled up which has less segregated calcium carbonate than Calcic two major glomerate fills a later vent, Tioga ones that are correlative with Lake Lahontan 16). Within the map area only one general level of a final phase of explosive Brown soils; it is 6 to 30 inches thick, light brown to through these flows during cycles (p. llOand pl. 12). is discernible, but elsewhere in the region pale gray, weakly blocky to massive single grain, mildly pediments volcanism. tsvo or more levels have been identified (Jenney, 1935, rA-UT roRaSAwro to strongly alkaline, and gradatioral into parent Caliche, typical of the lower part of the Cocoon soil 1956, p. 69). material. p. 65-7; Thompson, (p. 25,28), is locally preserved in the uppermost partsof Gesneral /eatures.-The youngest sedimentary unit of areas of partly exposed pediments are Variants toward Soloneiak end Saloants soil.-The The largest the flmos and agglomerate in spite of several wave ero- pre-Lnke Lnhontan age has been named the Paiute Wyenimha Valley and the saddles bet wseen Sehoo loun- Gray Desert soils of the Carson Desert locally vary to- sions by Lake l[Aodntan; its presence suiggests that the formation (Morrison, 1061n) after PainteWnsh; it con- tain and Rainbowv Mountain, and between Rainbow ward Solonchak and Solonetz soils, which are saline basalt of Rattlesnake llill is older than the Cocoon soil. sists of alluvial gravel and colluvium. This formation Mountain and the Stillwater Range, Their lower alti- bor- soils formed where parent material is saline or where The earliest unit of Ianke Lahontan sediments, the is exposed in the mountains and on the piedmonts tude with respect to the bordering mountains is prob- the Blunejug formation poor drainage hs caused salt accumulation. The vesic- Eetza formation, also rests on the basalt, showing it to dering the bnsins. It overlies ably due largely to differential erosion of the soft unconformity, and is ular horizon generally is absent; instead, these soils Lake Lahontan. and older rocks with pronounced Truckee formation. be older than Valley have a white to light-gray salty crust in places, about basalt overlin by the Betza formation of the Lnhontnn in the mountains are in the Seven wells near Rnttlesnake Hill penetrated a quarter of an inch thick, underlain by half an inch Canyons-The valleys grouip witi slight ornodisconformity. Intermedinte in stage of develop- or reported basalt beneath several hundred feet of Qua- to several inches of light- to dark-gray highly aggre- early mature or, locally, the youthful age between it and tlse Eetza formation, however, is the formation, but terrace ternary sediments Somei of these scells may have pene. gated (flocculated) clay loam or clay having a strong ment. They dissec the Bunejug .t Cocoon soil, which has a very strongly developed soil alluvial gravel of the Paiute trated buried tongues of basalt of Rattlesnake Hill, but fine granular structure and loose to fluffy consistence reminants, veneered with profile, and hence is an excellent marker for differen- they were cut nearly to their II others may have penetrnted bluried hills of the Bunejug (termed "self-rising ground- where wvell developed). formation, show that tiating the pre-Lake Lalmontan deposits from the La- That they had attained The basalt generully is a good aquifer and The B horizon is darker gray or brown gray, moder- present depth by Paiute time. formation. hostan Valley group. forms before the advent of Lake quality than%other aquifers in ntely compact, and has a structure ranging from strong virtually their present yields water of better The type locality of the Paiute formation is Paiute colluvium of the miles south. columnar (Solonetz soil) to granular (Solonchak soil). Lnhontan is shown by the sibiquitous I the area. Of these 7 wells, 2, located 1/% Wash (sec. 8, T. 16 N., R. 31 E.) on the piedmont north- learing the Cocoon soil, on the valley Ilill, penetrated basalt The C_, horizon generally has only moderate calcium Psiute formation, west of the center of Rattlesnake enst of tie Cocoon Mountnins. The banks of this waish slopes above the highest shoreline, as well as!by the municipal water carbonate concentration and is only several inches IL at 455 feet; they it-e used for Fallon's expose vell the stratigrpluie relatiois of alhu vinl gravel of the contact at the base of the thick. topographic relatio,,s supply. Autothier sri-l, about 2 miles southeast, supplies of this formatioum to the Cocoon soil, flutejuig forna- Fetza forimation. Post-Paiute erosion has amounted to t Statuion: the otiler wsells are Valley group (section 56, table 10). ihe Naval Auixiliary Air 4 tiol, and Lahontan PRE-LAKX LARONTA1 EROSIONAL FEATURES generally less than 30 feet of dowvncutting of the stream 3V2 miles west, 2 miles southeast, '/a miles north- Alluvtal gravel.-The bulk of the Paiute formation and to negligible moditication of the valley 1II which, is exposed locally in tlme The highlnids Iad almoos exactly their present channels X northenst, nia, 4 nailes east-soutilieast of Rattlesnake is alluvinl-fat, gravel, shapes when they were first inundated by LAke Lahon- slopes by mass-wnsting. lfill. motitainis-vnileys nid on thle lie-unonits. Genernily the .I QUATE1RNASR STRATIGSAPHrT 25 LAKE LAHONTAX: GEOLOGY,CARSOlf DESERT, XEV. blocky to prismatic in structurs, sand of the Wyemsha formation. It is expos eedfor lar to subangular exposures are above altitudes of 4,040 feet, although on colluvium is strongly cemented by calcium carbonate, when dry, and alightly plastic \more than I mile upstream along the main waRth and slightly hard to hard the eastern Piedmont of the Cocoon Mountains, border- which is inferred to be the CA.horizon of the Cocoon when wet. Most of the larger rock fragments are pe- its tributaries, and is particularly well exposed in the ing Fourmile Flat, the Paiute is exposed as low as 3,900 soil. This colluvium commonly is mantled by I or 2 ripherallystained andsoftened but have fresh interiors; the 4,645-foot summit in the (Cocoon feet. Below the high shore of Lake Lahontan this grav- feet of younger colluvium, which is not differentiated basin south of few are soft throughout This horizon is Mountains (fig. 5). Unfortunately this localit y does relatively el is mostly buried by younger sediments; a few on the geologic map. i inches, and at most about 1 foot the full profile of the soil, for the IS hori. generally only a few washes-notably Paiute Wash-have cut through this Paiute formation seems to be of late pre- not illustrate lower several inches, transitional into Age.-The son is partly or completely eroded; only the C, . horizon thick. In the veneer. In the mountain canyons only rare tiny Lake Lithontan Quaternary age because no large uncon- 41 the C.. horizon (the B., subhorizon) the color lightens, preserved. patches of the gravel have survived later erosion; more formities or lithologic discontinuities are evident in the is well the clay content decreases, and in places small segrega- extensive deposits are preserved in a few mountain exposed formation, the Cocoon soil is conformable upon FA0r755 CNAUACTESI5TZc1 tiona of calcium carbonate are present. The oxide hori- basins, such as those in the central Bunejug and north- it, and that soil is immediately older than the earliest ad in a ton has more clay, is darker and redder, and has a In the area mapped, the Cocoon soil is expos ern Cocoon Mountains. Maximum exposed thickness deposits of Lake Lahontan (Eetza formation). t 4,000 greater maximum thickness than the oxide horizons comparatively small altitude range, from abou of the gravel is about 40 feet, along the middle part of ughout of any of the younger soils. SURXUt PIUC-LAZ LAZOSITAN QUAThRNARY to 5,300 feet. It is a Calcic Brown soil thro Paiute Wash. Much greater thicknesses, locally more sle dif- The calcareous (C,.) horizon is the most prominent the this altitude range; the soil shows no appreciat than 150 feet, are exposed along the western side of jal and and resistant part of the Cocoon soil, commonly being for many deep wells drilled in ference in development on similar parent mater Stillwater Range a few miles northeast of the map area. Logs are available only part preserved (fig. 6B). It is characterized deposits are small variation on different parent the The distribution and general shape of the alluvial the lowlands, but correlations with exposed comparatively by strong calcium carbonate (caliche) concentration in not reliable below the top few feet. Equivalents of the material. fans of this gravel commonly can be distinguished, de- i rarely coatings, veinlets, concretions, and disseminated parti- formation doubtless exist in the subsurface of the The complete undisturbed profile of this soil il spite widespread cover by younger sediments, by their Paiute s, wind, cles, and consequently it is light pinkish gray to vhite. and even older Quaternary sediments seen; most exposures have been eroded by wave transverse profiles, local exposures, and size-these fans basin interior, horizon The caliche resembles some kinds of lithoid tufa of but they cannot be identified in any of slope wash, or mass wasting. The original A are much larger than any of the younger ones. There may be present, !nerally Lake Lahontan, but generally the ecaiche is whiter and was now-here found; the B (oxide) horizon gi is no evidence of significant dissection of their surfaces the logs. 1,.(Cal- Ims a more chalky or earthy luster. Thickness and is partly or entirely eroded or reworked. The C prior to the first rise of Lake Lahontan, nor are there cocooN son, of development are influenced by the mineral careous) horizon is least eroded, largely because of its intensity significant unconformities or interbedded soil profiles in and permeability of the parent material. SENESaLYrEArxES A" RxLAT1no11 resistant heavy cementation. The calcareous horizon composition their gravel; the exposed part of the gravel is inter- mnfrom Normal thickness is 4 to 8 feet; extreme range in thick- diagnostic to distinguish the Cocmc preted as recording only a single interval of alluviation. The youngest exposed beds of alluvium and colluvium is sufficiently ness, 8 to 12 feet. The calcium carbonate concentration soil that has a very the younger less strongly developed soils. Throughout the map area the alluvial gravel is boul- of the Paiute formation bear a is is strongest in the upper part of the horizon and grad- of the upper part of the Cocoon soil der to coarse pebble gravel, poorly sorted, torrentially strongly developed profile. This soil also occurs locally The character ble 11), uilly decreases downward. At some localities, the up- directly well shown in two profiles, 5IS and 59S (tal bedded, angular to subangular, and is characteristic of on older rocks, but not on younger ones. It i of the per part commonly is crudely layered with alternating the summit plateau steep- to modersite-gradient ephemeral washes in anrid underlies the earliest unit of the Lahontan Valley group from shallow pits dug on relatively pure and less pure calcium carbonate. In the Paiute formsa- White Throne Mountains (fig. 6A). regions. The rock fragments are the rocks in the drain- (Eetza formation) and thus postdates the as Pus- purer layers the smaller rock particles are absent and were carefully selected to be as free age area-chiefly basalt and andesite. Generally the tion and predates the Lahontan Valley group. The sites hey are the carbonate is interstitial between larger fragments, soil, after its type local- sible from younger erosion and deposition; t proportion of interstitial fines its low and these are This soil is called the Cocoon st mate- forming abreccia. This layering parallels the land sur- It is a Calcic level broad ridge crests. The parel mostly silt and clay rather than sand. This gravel ity at the edge of the Cocoon Mountains. on nearly man- face that existed at the time the soil formed. The C,. than any colluvium-solifluction mantle and cree typically is less sandy than the younger alluvial gravels, Brown soil and much more strongly developed rial is horizon acts as a caprock where gullies or washes have tle-of the Paiute formation, which overlies bbsalt of especially that of the Wyemaha formation (p. 36). younger soils of the area. In degree of development ly a few cut through it into underlying less coherent material. paleosol in the Rocky the Bunejug formation. The pits were dug on Colluvium.-Thin sheets of colluvium of Paiute age it resembles the pre-Wisconsin ebottom No general differences in original profile characteris- Co- into the basalt, so they did not reach the veneer many mountain slopes above the high shore of Mountain region (Hunt and Sokoloff, 1950). The incises tics can be discerned in comparing the C.. horizons of as the soil that was called (Mor- of the calcareous horizon. Lake Lahontan. Below the high shore this colluvium coon soil is the same oon soil buried and relict occurrences of this soil with respet the pre-Lake Lahontan soil. These and other relict occurrences of the Co is rare, having been reworked by waves. In the moun. rison, 1961a) I of I to to properties that are readily observed in the field- soil is exposed only in the highlands. commonly show, at the top, a vesicular horizoi tain valleys the colluvium grades into and interfingers The Cocoon or loam thickness, color, structure, consistence, general degree with alluvial gravel of the Paiute formation. It is Above the highest shore of Lake Lahontan it is widely 40 inches of pale pinkish-gray sandy loam bedrock and on witll highly vesicular structure, which resemibles the of calciumcarbonateconcentrationandfieldph. This grouped with the alluvium on the geologic maps. exposed, commonly as relicts, both on Because Suggests that subsequent soil-forming processes have of the Paiute formation. Be- vesicular horizon of the Toyeh soil (p. *9). The colluvium is mainly solifluction mantle, creep alluvium and colluvium rizon of not been Sufficiently effective for long enougls intervala cliffs. It low the highest shore it is rarely exposed, having been this horizon commonly crosscuts the oxide he mantle, and local slide rock (talus) beneath I appreciably modify relict profiles of the C,. horizon. eroded by waves in all but the most sheltered locations the Cocoon soil and because it is not present in buried to extensively conceals the bedrock in areas back from the i eCocoon This horioin varies little with differences in parent in smoothly or buried by younger sediment; exposures of such Z occurrences, it is believed to be younger than the frontal scarps of the mountains, resulting t, material, relative to the younger soils. Variations are on the buried occurrences have been found at altitudes as low soil and not part of its original profile. rounded slopes. It is a foot to several feet thick II ved only largely due to differences in calcium content and perise. than 5 feet. The oxide horizon of the Cocoon soil is preser mountainsides, but commonly thickens to more as 4,000 k of the parent material. This horizon is very surfaces that are well Iprotected ability or even 10 feet near the base of the slopes and in saddles. locaVity.-The type locality of the Cocon soil on flnt or gently sloping rocks such as basalt, or Type erode,I or dis- strongly developed on calcic Only deposits more than 5 feet thick are mapped. This is Paiute Wash, which heads in the Cocoon Mountains. from erosion; elsewvhere it is generally of it, ind weakly developed It consists of reddish- sediment composed largely thickening evidently is due to slow downslope move- Here this soil is developed on alluvial gravel at the turbed by creep alnd soliflu.stion. i brown to brown clay lonsi and is apprecial ly more on rhyolite (compare profiles 58 and 59 with profile 46, ment, for crude stratification and shingle structure that type locality of the Paiute formation (section 56, table clayey that, the parent material, typically ston:Vgrunu- in table 11). The calcareous horizon is thickest iu marallel the land surface are common. Generally the 10), beneath gravel of the Eetza formation and eolian i i 4 A! .1 LAKE LAHONTAN: GEOLOOT, CAR8ON DESERT, NEV. QUATERNARY 8TRATJGRAP}IT 27_

: * :;

s. . , ' ' , .:~~~. . * I

v

6. .10' i Ibl-

.0: =0 a 2 oz i * ID

IetI 9

z 0 -i . D -A 00< z I li WE 4>I ! o- 0S -J D - a- E 1 U I .f .

D- .C i , e Vz ! t 1 J n .9- -9 . i I- 1 ^<.\'. o I .tR~~~i*' .0 3- 0 " E J .}

.

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MU00 6.-Coooo .H. A, WITllrptCrvd ofer" 7C of It- PrItl, IrPitrR -on-- t PIot.-. of Ihe Whit. TI,...~oa,1000 o...11poonh beg. MM021.I. UPPo. --- Ir IlorO. (000 .kW l IoI (V), byll Me l r (I 1) 0h Ir O;.bl r, 1-iJit II... CG*0 rIt0. R-.CW-r of -p-.-rr 1. Cru- Comnn Coil. rmnrl.lIto of n at.,., 0.1.1 INrl n IB( ol rr.llohIro.0 nly lonm, nd . Saw.,rI..ro-.. 1,-mb.- (Coaw. of ,10 Io -d, y hhit,.I lt.Mb .. fbo.-..ot rp.r.P1). Fartod 00 M.0ol~,a P.M. fo,,omllo- _n,. b.-Il f I n iaormlCo.fJt-r Jl, Typto. -ptbo- 00 .71.lo -rrfo. *howlog only - I IC,, roC.lo C. harlnoI; 11 h1r.. In-- OroCtod. n-.., f th,. C,, h-oI-.o 1. ool .1d 1t. Otto, d- lI nt 1o .leorrttrb of th.1 00 ¢.l' aro-t 0,MlerloI lb.,. molul l of Pilot, far~o- . fn,0, I114..i,,a fort.,'olooC Otl~l. 0oillwlt no 22 lIn.r....dl, 7. IN t".. 31 JIC

6"403 0-44-4 'I .I

LAKE LAHONTAN: GEOLOGY,CARBONc DESERT, NEV. QtATERNARY IStRATIRAP5rT 29 permeable material such as alluvial gravel, but the deep-lake to subaerial and shallow-lake sediments. tion (p. 23); the reentrant west of the 4,645-foot peak are minor constituents (fig. 8). Here also the gravel calcium carbonate is more dispersed. The horizon is Two formations, the Sehoo and Indian Lakes, are fur- at the northeast edge of Cocoon Mountain (section 55, commonly is associated with prominent rock-cut fea- thin but its caliche is especially concentrated where ther subdivided. The Lahontan Valley group overlies table 10) ; and along many of the washes at the edge of tures, such as wave-cut terraces, cliffs, caves, and small dense bedrock lies at shallow depth, as where it has the Cocoon soil and underlies the moderately de19eloped the Stillwater Range within and adjacent to the Carson stacks. The roof of in Eetza Mountain formed in colluvium over basalt Toyeh soil (p. 78); intercalated with it is the strongly Lake quadrangle. shows this type of deposit especially well: the gravel, Influence of slope on prop characteritkc.-The developed Churchill soil (p. 38-39) and two incipiently The gravel ranges in exposed thickness from less than cemented by lithoid tufa of this formation (table 5), is oxide horizon of the Cocoon soil is so poorly preserved developed soils. The group is Pleistocene in age (Mfor- I foot to rarely 90 feet; it normally is less than 20 feet. more than 20 feet thick and contains boulders as much on slopes that the effect of variations in slope on its rison and others, 1957, p. 390). The thickest exposures are in the high-shore embank- as 5 feet in diameter. The rare exposures of pebble original development is unknown. Differences in slope ments along the north front of the Desert Mountains gravel are in the distal parts of spits and bay bars, away TrIzA FORMATION up to at least 3O0cause no discernible variations in (fig. 7), in mountain reentrants where bars and spits from hardrock outcrops. original thickness or intensity of development of the SEsEXAL VZATU3S5 were prominently developed, and in a few low-lying On shores sheltered from strong waves, the gravel is C<. horizon. The Eetza formation, stratigraphically the lowest spits opened by gravel pits. In the thickest exposures finer and thinner. The waves commonly washed out Modification by erosion or disturbance is sppreciable unit in the Lahontan Valley group, consists of deep-lake the base of the gravel commonly is not exposed. the finer material of the colluvium and alluvial gravel in at least 95 percent of the relict occurrences, but the sediments that overlie the Cocoon soil and older units Lithology.-Gravel of the Eetza formation typically of the Painte formation, leaving a coarse Ing concen- cemented C,. horizon generally remains relatively un- and that underlie the subaerial and shialow-lake sedi- is boulder or cobble gravel; rarely is it pebble gravel. trate I or 2 feet thick and so little reworked that the disturbed. Creep and solifluction have commonly ments of the Wyemaha formation. It records the first Almost everywhere it is the coarsest lake gravel of the fragments are subroitnded to subaigiilar. Cut features churned new material into the oxide horizon to form deep-lake period of Lake Lahontan. The type locality Lahontan Valley group. The coarsest and best rounded are absent, and depositional features are only weakly colluvium. younger than the Cocoon soil, which thickens of the Eetza is the upper one-eighth mile of the large gravel either is close to or directly overlies outcrops of developed, except locally on lee shores adjacent to ex- downslote. Slope is critical: on slopes of more than southward-draining gulch in the western part of Edt=a hard bedrock on mountain shores that were most shores of strong wave action, where spill-over spits 10° the B horizon is severely to completely eroded or Mountain (SIVW4 sec. 21, T. 18 N., R. 30 E.) Here posed to strong wave action-particularly the north occur. reworked, and on slopes of more than 25° the C,, cobbly and bouldery lake gravel as much as 15 feet thick slopes of the Beiza, Sehoo, Bunejug, White Throne, and Getierally the roundstoues in this gravel are entirely horizon commonly is also appreciably eroded. Even on overlies the Bunejug formation and underlies the 11ye- Desert Mountains. Ozi these shores the boulders com- andesite amid basalt, the prevailing hard rocks of the flat uplands where the profile is best preserved, the maha and Sehoo formations. monly are several feet in diameter, and sand and pebbles highlands; locally they are rhyolite or silicified tuff. tipper part of the oxide horizon in places shows evidence The Eetza formation is exposed only in the highlands, of having been somewhait eroded and disturbed. where it consists of lake gravel and minor amounts of lacustrine sand. clay, and tufa. It extends as high as AGE the highest shoreline of Lake Lahontan-at an altitude The Cocoon soil is developed on the youngest beds of of about 4,380 feet along the south margin of the Carson the Paitite fornmation: for example, at the apexes of Desert-about 10 feet higher than the next younger pre-lnke Lahontn alluvial filils, where alluviation main unit of deep-lake sediments, the Sehoo formation. probablly was active till the end of Paiute time. No The upper and lower boundaries are sharp and readily soil fis been observed at lower stratigraphic levels in identifiable. the l'aiute formnt ion. The Cocoon soil (locally includ- ing the B horizon, somewhat eroded) is overlain in LAZEoRAVEL miny places by the earliest gravels of Lake LAhontan, Distribution,strmtigraphic reiations, and thictness- so it obviously is post-PFaine and prc-Ectza in age. Lake gravel is the only lithofacies of the Eetza forms- tion extensively exposed and is practically the only one GROUP LAHO rTAyVALLEY associated with correlative shore features. It ranges Overlying the Cocoon soil and older units are from the highest shoreline of Lake lithontan to as low lacustrine and subaerinl sediments that record a succes- as 3,920 feet in exposures along Wildcat scarp north of sion of five deep-lake cycles alternating with intervals the White Throne Mountains, and at least as low as of pamlial or complete Inke recession-these are the 3,890 feet altitude in the subsurface. It is extensively series of lake fluctuations that are Lake LAhontan in exposed above 4,000 feet on the mountain shores close to the sense that this name was used by Russell (1685). exposures of bedrock or Paiute formation, but generally These sediments were named (Morrison, 1961s) the it is concealed by younger sediment elsewhere. lahontan Valley group after the term commonly used This gravel rests either on bedrock or on alluvial for the southern part of the Carson Desert. Lahontan gravel or colluvium of the Paiute formation, and gen- Valley group replaces the name Lake Lahontan beds, erally is overlain by eolian sand of the Wyermaha forma- which is here abaldoned. tion or by grvel or sand of the Sehoo formateion. The stratigraphie relations can be seen especially well at the The Lnhontan Valley group is subdivided into five Frotaa .Nftm ei,4mo, of O.,,t t,.~eoo~ti-alty-p~tt, thieS blhteh~,ei e~.ke or 10,.- of rt,. t-.,,Il.. sad formations-the et za, Wyemlma, Sehoo, Indian Lakes, following places: The type locality at Eetza Mountain; I.-c -bo.o Sr M,.is fo5to. .1 Iweit, ~o droeitoiff. vii. oh.. Fo., 4dI0ty -,otb .04 -.. -op-od I. -1i Mt.-o the basis of lithologic the saddle between Fetza Mountain and Sehoo Mfoun- o.-. .1th 01let,, or as to TO si.u ,oohel.o Ist,tlkeoeod dortos tie Sbig., hoo. ,f th 5.t.,'I .04 -IiF 5..,, 0.b,.. ndil Turupah fortuations-on be~eoh.-es I.y sobh,.fr...... tI.. *i1i1b g,.dle caddly eti-.t*i f.seMri. ioalk..t,. 1Sch.veto.otteo ,et of tlh differences due to two major alternations, from mainly tain (pls. S, 8); the type locality of the Paiute forms- etod-.t oP to tbe Slgb.i,,o shsl oi M

QUATERNARY STRATIRApHT 31 LAXE LABONTAN: GEOLOGY, CARSON DESERT, NEV. front of the Desert Mountains, both shorelines include is at an altitude of about 4,380 feet along the WI., -" p. 101), wave-cut terraces 30 to 75 feet and locally 200 feet wide, most .aQcurate south edge of the Carson Desert; the on basalt and rhyolite; the terraces have cliff scarps the VABM triangula- determinations were 4,382 feet at commonly 20 to 7b feet and rarely 100 feet or more and 4,378 feet at Rus- tion station on Eetza Mountain whigh.In reentrants where the Lahontan beach is lack- feet above the lowest sell Spit (fig. 30B), about 515 ing, the 4,875-foot shoreline is the highest discernible p. 101) deduced part of Carson Sink. Russell (1885, shoreline of Lake Lahontan, and although its strong features that ftrm the geomorphic relations of shore development might suggest control of lake level by pe- this shoreline formed during the second high-level overflow, a reconnaissance of all possible places of over- The riod of the lake (Sehoo time of this report). floir around Lake Lahontan showed no evidence of it, the southern part of writer, however, believes that in thus corroborating Russell's conclusion. (p. 65), and the Carson Desert it is of early Eetza age The 4,0ti5-foot terrnce is the best marked terrace of the lake in Sehoo time that the highest level reached by Lake Lahontan, being cut commonly 50 to 100 feet is about 10 feet lower (fig. 9). wvide,and 300 feet wide on the most exposed shores, even minor shore- The Lahontan beach is a comparatively on basalt and rhyolite. Terraces at altitudes of 8,980 the boundary be- line, although important in marking to 4,010 feet are locally prominent at the edges of the sculpture (figs. 10,11). tween subserial and subaqueous Lahontan Mnounitains (especially at Grimes Point) and It commonly is not visible on shores sheltered from Flaps. 5.-.Bonid,,y prtni Weraa lb. Eel.. ossina .atl at the edges of the northern parts of the Bunejug and t .satPstisag wn on exposed shores it is marked by bench terraces *b~ ~niepeaib. .. i. basia sad"pd waves; Throne Mfountains. These terraces are at about bay bars of gravel in some White 1* X.. a few feet wide, and by small .as. a1' U-t M.doa.i.. NWi/4 -~. 20 1tn...y. d). T. the same altitude as the thinolite terrace of Russell b..t*a4.350 fnt aititad, 4abiwt 50 int W..r iba L~b... of the reentrants of the mountain slopes. II. 2 237) in the area, but their laabi~bi5-d~.Sa Eat1.. Hi-, 'hy.11i.. Th. alit. is b.-k- Lower shorelines.-Below the Lahontan beach, about (1885, py lonadnP. .015 . .I 41idriapblb., atbad at Spa lt5,. considerably antedated the 15 shorelines of Eefts age are marked by both rock-cut development probably and ...rIF s'h- Uk.. and table 5). and depositional shore features, strongly to moderately deposition of thinolite tufa (p. 65, west developed (pl. 9), and 12 minor shorelines are marked Eetza shorelines facing north, northwest, and tufas although locally it i been severely This gravel lacks distinctive by small gravel embankments without rock-cut fea- 4 across the main basin have generally or as waterworn frag- contains lithoid tufn in place tures The stronger shorelines probably formed eroded and in places obliterated by wave erosion in ments. mainly during early Eetza time, because the coarsest early Sehoo time, especially those between altitudes of thick sections of the Commonly the lolver parts of Iske gravel of the Eetza formation, which is in the 3,950 asd 4,050 feet (fig. Ili). Elsewhere, however, than the uipper parts; these coarser i gravel are coarser lower part of the section, rests directly on the wave-cut particularly on shores facing south and southeast (for commonly make up the bulk of constructional >> parts surfaces and makes up the bulk of the constructional example, in the Laliontan IMlountails), the shorelines shore terraees, spits, and bars of Eetza age and also are features. show little or no erosion (fig. IIA). Evidently strong associated with rock-cut features of the main shore- winds came from the south and southeast in Eetza time lines. In the thick gravel embankments along the Sehoo time. north front of the Desert Mountains, the Eetza forma- but not in early zones sep- tion commonly has utpper and lower gravel T1rA arated by a middle zone of sand, silt, and local gravel (section 60, table 10). 10---tlll~t-1Pb~~xlpbat stsmoallta.t w-U The Eetza formation lacks the volume and diversity of lake tufa that characterize the Sehoo formation. It 8soaX rYarUaxS Pnr. 6lana rI...d -In1 i n-lnai-dt *ia- -f tnhybt sa b.ttainb Th. b i,, 5.no.. alb tillFr ,.. ...Tb locally has small amoutits of a dense stoty testured os."ratil a. .Paloe .slyl a Gravel of the Eetza formation is associated with a ",I tell. farwa~lsonInd .,-a1o I li~ai.n+ algal tufa called lithoid tufa by Russell (1885, p. 190- Pt,. atnl mriaat abonnta.s,,naa ort drp,,ala an .bon.iia.. at Sebann series of shorelines developed during stillstands of 4 ag. .iaewaeo.. Tb. .berp *trir, aifliad, lituit .f ln id lb. tow.? 192). This tufs is described in table 5. It. closely re- h... b. bohniary h lWe.n blek nda-.. The visible shorelines are practically ,wb,, at lb. SnO.. 5 the lithoid and cellular tufas of the Lake Lahontan. I er.Y h.-, *few t 1. btol- lb, bbal.5,.,h. Th. fal. i, 1'p. sembles much of o1,- restricted to the steeper mountain slopes, as elsewhere la,-ii r. -o5htl.. trrnlb(n trt WYrn.ha .nd rn5,ba lower memberof the Sehoo formation,and in places the 1, Cbahbill toni ,-," nmb:., .(( I%,hr. toe- buried by younger sediment They, are n.itio WSw)a: did not they were 't.I lahilan .ad tow,, I-Ur. or 1.4i. 1.ltk. f-n ilase I: .nd Piddl, two titfas cannot be differentiated. Russell terraces, (I...tInl s150phs la.pbh ninrked by wave-eut and dispositional shore ions,. df .adis fonanolon recognize the two ages of lithoid tlufa on the higher locslly caves. These shorelines differ I spits, bars, and shores. of differences in dura- in degree of development beenise i The 4,3T5- and 4,350-foot shorelines are the strongest 25t17A.TZA XAXX 1rC1T'S30X tion o; the stillstands, in willdstorm intensities, in .4 of the higher group. Russell (IS88, p. 101-103) desig- Fetza foriation generally 5how exposure due to tolpography, sal in erosionll resistance Fap.sa S-tn alb. blib,.t h.,. nd Lob. e .b iata t(Ljb oat .v natted the 4,350-foot shoreline as the lithoid terrace be- Exposures of the bKhett shn,. Of lb. .0F, or discon- of the shore material. Shore features bordering the b.. ). hitbih1n af tola. .. n. lb. "i cause it lies at the uppier altitude limit of his lithoid no intertonguing subaerial sediments, soils, abnat .. , . _n. `4 by lb. abe,. dan it. tin,. 1,.- d tqs) The nimi ('arson D)esert and facing north nr west are most 1t 3E tl fat nti.a; l1.h1t. e9no. i 1 0wst IQl wnn ..inb,, of aS a I tufa; in places, however, lie niso applied the name formities indicative of significant lake recession. ftnl:OMrt-t Qtn"It 1. Ih- blxh-l 0-11..l ol Ihtt vtt3, (1885, p. 114 in western Wryemaha Valley stroligly developedl. plays aedi.-l. lithoid terrace to the 4,375-foot shoreline only exceptiotis seen nre of Lake *ho.b l n ; *bt:hilln -,a 1 tigbht (00) b. yo-Ic the The Siihollhttn bram-h-Tthe highest shoreline Ab.iil -,a thlid oI . .11. -.tnibt0n of Ru-1l Sptl of lb. SalS- I and pi. 10). W'here best developed, ats along the north and in the thick emilbankmente of lake gravel along Lahontan, called the Lahontan bench by Russell (1885, nsit . d Doaer No4n.otia.

I U

QUATERNARY STRATIORAPHY 33 32 LAKE LAJBONTANS:GEOLOGT, CARBON DESERT, N5EV.I north edge of the Desert Mountains. In westernm ye. eoRaLATO. nwTrrs Exosu 01r LA5J?LARCSTAN DErIcXED BY 55AEL.SED AMAXTE maha Valley a probable very weak soil was noted at the site of section 45a (pi. ld and table 10) intercalated Excellent exposure of clay and silt of the Eetza with gravel of the Eetza formation at an altitude of formation in the valleys of the Humboldt, Truckee, and about 4,060 feet. In a gully at the north edge of the Des- Walker Rivers have been described by Russell (1885, ert Mountains (section 60, table 10), a disconformity p. 124-145), who called these deposits lower lacustral and very weak soil were observed between upper and clays, and by Antevs (1925a). Both geologists inter- lower sand and silt zones of the Eetza at an altitude of preted these clays as having been deposited during the about 4,220 feet. This evidence suggests that lake first deep-lake period of Lake Lahontan. Russell also recession below 4,060 feet took place between two lake recognized shore terraces and gravel deposits of this maximums in Eetza time. Recession at least as lov as age on the highland shores, although he did not desig- 4,100 feet also is indicated by a thin gravelly and sandy nate them by a separate name. zone in the middle of the clay-silt lithofacies of the Russell noted that the base of these clays is not ex- .~~~~~~~~~~~~~~~~~~~~~ Eetza formation in exposures along the posed in the river valleys, but estimated their maximum below Wadsworth (Russell, 1880, pls. 24 and 25; thickness to be at least 150 feet. He described the clays Antevs, 1925a, p. 87-97). as very similar to the "upper lacustral clays" (the Sehoo In the gravel embankments along the front of the formation of this report), being evenly bedded, locally e~~~-R* Desert Mountains, a lower gravel unit in the Eetza for. thinly laminated, light- to medium-dark-gray clay and mation, apparently underlying the disconformity, can silt, in places marly and saline, and commonly well be traced continuously up to the Lahontan beach alti- jointed in exposures. The lower clays differ from the tude 4,380 feet, whereas an upper gravel and sand unit upper lacustral clays, however, in having a higher of this formation that apparently overlies the discon- proportion of silt, in being devoid of volcanic ash fornity can only be traced to about 4,340 feet. These layers, and almost devoid of fossil mollusks. Both relations suggest that the second lake maximum of Russell's and Antevs' stratigraphic sections show that Eetza age was about 40 feet lower than the first. The the lower clays locally contain interbeds of sand and relations are best illustrated along the east side of a even gravel. canyon, a quarter of a mile southwest of the site of PAZZONrotLoY I'MOR "I.0 II.-. bla.,Obn- boH- 1.lo~tb o-d -1 -tloot- t ". .-. ---, -'. section 60 (table 10). -b-1---Ut--1-9--t-- b--hlf d ]- tWt1. Idl d~l., Et .. ~tlb -.-- .. 4,.1Ib . The only fossils found in the Eet=a formation in the map area are: (a) gastropod shells, locally fairly LAKE SAND, BILT, AND CLAY abundant in lithoid tufa associated with the lake gravel; (b) ostracod shells in sand interbedded with .f b. 1b- f P. -.T. 11Z - .1,.-Jb -11 f 11 -yl.g ..- 11b, ,- v Exposures of sand, silt, and clay of the Eetza forma- tion are rare anid too small to be mapped. Sand was lake gravel at the Dodge gravel pit, on the eastern side Al~. -1T,-. r-dI. - ' tot'lI. - b.211 o- f of. "o Mo. of Ttrilpah Flat: and (c) rare, unidentifialile frAg- I,.-.~ ~ ~ ~ ~ ~ ~ 't1 -1yC..Io lhof-l. ."9 -bldd 41 f o l found: on the lee side of a high-shore bar I% miles northeast of Salt Wells on Salt Wells Mountain; inter- ments of mnammal and bird bones in lake gravel at this bedded with gravel in a spit at the Dodge gravel pit, sante locality. on the east side of Turupah Flat; and, most extensively, A collection of snails from lithoid tuft of this forma- interbedded with gravel in the thickembankments along tion in atvash-bank exposure in Churchill Vnlley, at the Desert Mountains (see table 10, section 60). the type locality of the Chlurchill soil, was determined b -b 2 b- dl t I I fa l. h -1- -- 1 P db Silt and clay were noted as a few thin interbeds in by Joseph P. E. Morrisonl, U.S. Geological Survey, as: the gravel embankments along the Desert Mountains, at enetpheOl"aedsfesi 5Iendrea two localities on the eastern edge of the Dead Camel Phtla let. gJvfil Sayr? Sl.strata OsI Mountains, and also intertongtuing with sand and gravel on lee sides of two spits of Eetza age; one on the south- Fileh of these species and genera is still living in North western piedmont of the Btunejug Mountains at an nati- America and also is found in younger depxsits in tile tude of 4,030 feet, and one near a gravel pit on the north- Carson Desert (table 6). west side of the White Throne Mountains at 3,900 to ALLUVIAL GRAVEL AND COLLUWVIM Or IXrZA AIC 4,0'20 feet; the two latter occurrences locally bear the Allvter; gnsceL-Alluvial gravel considered to be of Churchill soil and seem to be lognonail deposits. Eetza age occurs in a few places along mnountnin washes Deep offshore facies of the Eetwa formation are no- nbove the laholitan bench. It is poorly sorted pebble- where exposed. hiiried eqiuivaleiits larobiily have been to lemiler gravel, I foot to rarely 5 feet thick (hence penetratedli in wells bitt cannot be identified the avail- generally unnilpilimble), and is lesssnandy timh alluvium able logs. of the Wyeninhia forlmation but virtually identical with I

LAZE LAHONTASS:GEOLOGY, CARSONS DESERT, NtwV. .I QuATRtAPTY sTMAT7oRAnET 35 that of the Paiute and Indian Lakes formations. It can lands to altitudes much above those reached by the lakes be designated only from correlations of C,. horizons and here. lies on older units. The subariel sediments which are inferred to represent the Cocoon and Church- extend to the lowest parts of the former baa floor, ill soils (B horizons generally are eroded), as follows: where they are intercalated with the shallow-lake sedi- Where the alluvium of a wash bears two C,. horizons, ments. Obviously this formation records a time when the lower one very strongly, the upper only strongly Iake Lahontan was intermittently dry and at very low developed, the lower one is inferred to be the Cocoon levels. Itbearsthe Churchillsoil (p.88),whichoccurs soil and the alluvium bearing it, Paiute formation; the on beds as high stratigraphically as the youngest beds alluvium overlying it and bearing the strong Cfcehori. of this formation but not on younger deposits. zon is inferred to be of Eetza age if it is low in sand -The formation is widely exposed in Ihe map area. In and of Wryemaha age if sandy. Where the C. horizons contrast to the Paiute and Eetza formations, it crops are lacking no designation can be made with confidence. out extensively in the lowlands as well as in the high- In a few places along the north front of the Desert lands, although in the lowlands only the uppermost part Mountains, siluvial gravel of Eetza age intertongues is exposed. Above an altitude of 3,990 feet it consists with lake gravel of the Eetza formation. of eolian sand and small amounts of alluvial gravel and 0 Vollitrium.-Colluvium of Eetza age is widespread sand. Below 3,960 feet. it is mainly shallow-lake sand, silt, clay, and muck (lithologically distinctive from the in the highlands above the Lahontan bench and has not I been recognized below this shoreline, but it is invariably overlying Sehoo sediments), and minor amounts of too thin and discontinuous to be shown on the geologic eolian sand and alluvium. Between altitudes of 3,990 map. It consists of solifluction and creel) mantle and and 3,900 feet it is intertonguing subaerial and shallow- X overlies similar colluvium of the Paiute formation. lake sand. The contact is commonly diconformable and lies at the i CORRELATION WIT" DEPOSITS OF xtE LAMSONT" i top of the C',.horizon of the Cocoon soil: The younger DEScRasEDBY RUSSELL AM As-rEVs 4 ______colluvium formed mainly as a result of solifluction and _7- 0 . _ creep of the earlier rolluvium in the uncemented B The Wyemaha formation correlates with Russell's I-f horizon of this soil, and the B horizon colors it pale (1885, p. 125-143) "medial gravel," which is exposed in P 4 reddish brown. Some white caliche from the under- the inner valleys of the Truckee, Walker, and Hum- boldt Rivers, interbedded between the "upper lacustral lying C.. horizon of this soil is commonly incorporated. Al On slopes of less than 50 the colluvium is absent or is clay" (Sehoc formation of this report) and the "lower I ~~~~~~~~~~~~~~~' only several inches thick. The thickest deposits, locally lacustral clay"'Eetza formation of this report). The several feet thick, are on the lower parts of slopes medial gravel consists mostly of river and deltaic gravel steeper than 15°. The colluvium thickens with altitude, and sand, and local wash gravel, ranging from several but this tendency is more evident in the higher ranges, feet to 100 feet in thickness. Exposures along the such as the Stillwater Range, than in the low mountains Truckee River below WVadsworth are at altitudes as low of the map area. as about 3,950 feet Anteva (19-2a) compiled several stratigraphic sections in the valleys of the Humboldt rTmIAMA FORMATISON and Truckee Rivers that show this unit. Evidence II GENERAL FEATURES contrary to his interpretation that the main deposition The formation was named (Morrison, 1961a) for of thinolite tufa dates from this major middle Lake I Wyemnahn Valley, and its type locality is in the saddle LAhontan recession is presented on pages 51, 59, 65, 108 :1 between cbhooand Fetza Mountains at the western end and table 5. ZOLIAN SAND of the valley (El/2 sec. 21, T. 18 X., R. 30 E.). Along the washes at the north and south edges of this saddle Eolian sand of the Wyemaha formation is widely but eolian sand of this formation is exposed extensively. unevenly distributed through the highlands, varying The sand bears the Churchill soil (which commonly is with t he relation of source areas and mountains to pre- partly eroded), overlies the Eetzn formation and under- vailing-wind directions and land masses in the paths of lies the Schoo formation (pls. 7, 8; table 10, sections migration of thesnnd (p. 99,100). Principal sand drift 42-45). was through the basins and lower passes; thus the chief 7.05.. 12.-A. Obl5q...... 1 slow 01 ,0te dew by ..t.. .0.a 1 W,-.b. e..to . lb. - l~b.,s Stti.a.W R ma.. Th. lIgbt- I.1to, ., ,. -r . -wily MIb. ,..d. t.-,5 with * thl. I ---, .1 .011. ..ad 1f PW5.. to. a.0. 1tsd -etd by Woon- lf~ts . The lWyteiah formation conists of eolian sand, allu- deposits are in 1ryemnha Valley, the pass area between th, .14 .s A. o.. ., , -..a.n . .ad e w s .~b. 1o, Hl , 00.11Iy.X .i. , , a,o I , ...I Of Re . o.,. tio-.. 1'.. -04 I vial gravel and sand, and shallow-lake sand, silt, and the Stillwater and Rainbow Mountains, Simpson Pass e,. mt01 by tilo o . ta n 4 o t ~dby as ,uhiof hot nI 9,~ which a- co t. for It . .. '.. .I .,.i0 .,- to - I... S -stb e. t 01*. .4 lb. Bo.-J,.9 ao.t.. ,,W.. . 50 I.o...... Y.dl. 1. SIX.. *.$(IJ clay. Most of the formation lies conformably or with and the northern foothills of the Cocoon Mountains, only slight disconformity between the Eetza and Sehoo the southern Dead Camel Mountains, and the Carson formationsl but the eolian sand extends in the high- Desert. fime higher mountains are free from the sand, p-

STRATIORAtW 37 36 LAKE LAHONTAN: GEOLOGT, CARSON DESERT, N5EV. QIUATERNARY I places in canyons or sheltered the Cocoon Mountains, and south of Salt Wells Aloun- range from a few inches to several feet in thickness, and foot and rarely 4 to 6 feet across, occur in many except for local deposits lodged quadrangle in lake The sandnowinthehighlandshow- tain, the sand is locally cemented by siliceous sinter from well bedded to iidistinctly bedded. Stratification in the western half of the Stillwater slopes(fig.12A). near the contact between the ever, seems tobe only a small fraction of that deposited; from extinct springs and seeps (fig. 12B). generally is parallel, though locally it is inclined. In. sand of the W~yemaha large areas is tertonguing relations and similsr mineralogy of the lake Wyesaha and the Sehoo. They are fairly numerous that it has been largely stripped from and south of Carson Sink, sand and by the sandy char- Ad UZ Iam COLIUGns oaAVEL AND 5aa' and eolian sands show that the lake sand was derived west of the Carson River shown by remnants of the 1% miles has largely Alluvium of the Wyemaha formation is exposed mainly by wave reworking of eolian sand. The upper- and a few large ones have been seen as much as acter of the local Alluvium. Severe erosion Hill. Their deriva- dune morphology. This sand locally in the mountain valleys and along drainage lines most foot or several feet of lake sand beneath the clay east and northeast of Rattlesnake destroyed the former perhapsp they were ice rafted across ranges widely in thickness, and probably exceeds 100 on the piedmonts but few bodies are mappable. Some of the Sehoo fornmation is nearly everywhere yellower tion is uncertain; is interbedded with eolian sand as lenses, I and deeper hued than the underlying beds-yellow, the lake. feet in places. The base of the thicker deposits corm- alluvium VX5v"5WACZSAMW SENET monly is not exposed. foot to rarely 15 feet thick, of sand, pebbly sand, and brownish yellow, and light yellowish brown (2.5Y 7/6 Good exposures showing stratigraphic relations can very sandy gravel, but most alluvium overlies eolian to 10YR 6/5 and 6/4) and light brownish gray to A few dozen logs of auger borings, made partly in the be seen at: (a) the type locality of the Wyemaha sand or occurs without eolian sand, and is sandy gravel grsyisht brown (2.5Y 60/2 and 5/2). present investigation and partly in early groundwater formation; (b) the main gulch in the central part of (sandier than the other alluvial gravels in the high. Eolinn sand is locally interbedded with the lake sand studies (Herman Stabler, written communication, Eetza Mountain (section 40, table 10); (c) Churchill lands) 2 to 10 feet thick. Most of this alluvium is 1N. in beds I foot to several feet thick. The best exposures 1904); C. H. Lee and W. 0. Clark, written communi- Valley, especially the type locality of the Churchill soil evidently younger than the eolian sand. It generally are at the warps of deflation basins east and south of cation, 1916), and driller's logs of water and oil- (p. 38-39); and the small gulch on the eastern side of was completely eroded where exposed to strong wave Upsal Itogback, vhere the eolian sand extemids as low test wells give reliable information on the upper part this valley where the overlap of the sand upon gravel of action by the early Sehoo lake. ns 3,920 feet. Other localities are the lowlands of the of the Wyemaba formation in the subsurface of the the Ectza formation is especially well exposed; (d) the Colluvium is relatively insignificant It consists western half of the Fallon quadrangle; the west bank basin interior. The uppermost 5 to 30 feet of the for- northeastern Cocoon Mountains (fig. 5 and table 10, mostly of local thin beds, too small to map, of poorly of the Carson Riser 3 miles north of Fallon at an alti. mation is mainly lake sand like that just described ex- section 55); (e) washes at the west edge of the Still- sorted gravelly to sandy slope wash intertonguing with tidc of 3,930 to 3,935 feet (section 13, table 10); nnd cept that the uppermost bed commonly Incks the bright- water Range within the map area; and (f) the north- the eolian sand, which abuts against steep slopes. the northenst snd southiwest edges of Eightmile Flat, yellowish or yellow-brown color typical of exposures. of the map east edge of the Dead Camel Mountains. 4 at an altitude of 3,915 to 3,940 feet. This sand is thickest in the western part .1 The sand is practically constant in lithology, except ssrlzaDEsoZ SHALLOW-LAKE Ai"SsUSAZSISA SEDIMENTs Alluvium of this unit was not seen in outcrop. Sev- area, where it is an important aquifer. It thins toward -11 for changes in color and induration and local lenses of The extensive exposures of W1yemaha formation in eral boreholes in the western pnrt of the Area penetrated the lower parts of the present basin floor, and locally alluvial and colluvinl sand and gravel. The sand grains the interior lowlands, below altitudes of 3,990 feet, are 'I beds of pebbly coarse said and sandy gravel in the pinches out or grades into fine sand, silt, and silty clay. are typically eolian-fine to medium sized and frosted. mainly shallow-lake sand and a little lake silt and clay formation (log 20, table 12) within a few feet of the The contact between the lyesmaha and the Sehoo gen- are alluvium and 2 feet) however, for the Quartz greatly predominates, and some feldspar slid a interbedded locally with eolian sand, alluvium, and f. surface; sone of these beds probably erally is sharp (within I or (only near Upsal Hogback) basaltic tuffaceous sand are possibly former channels of the Carson River. finer facies of the Wyemaiha characteristically are more small percentage of mafic minerals-hornblende,pyrox- II en; bronay biotite, and others-generally are present. and silt. These sediments are exposed in deflation In the deflntion iasins bordering Upsal Hogback, the organic end darker than the clay of the Sehoo. Eolian crosslelding, caused by migratingdunes, is com- basins and plains that were eroded through the Sehoo I deeper exposed strata are tuffaceous, whereas the upper Beneath the upper sandy zone is a thick section of mon in exposed sites (fig. 12B), but only parallel, formation, mostly in the western part of the map area. 8 to 20 feet of the formation are virtually nontuffaceous alternating thin sandy And clayey units whose base is well logs. generally inclined, and indistinct bedding is present in The exposures rarely extend more than a few feet below 4 (section6 ,taldle 10). The tuffneeous bedsareldark gray not clearly defined by data from the available canyons or other sheltered sites. the contact between the Wyesmaha and the Sehoo, but to black basaltic sand and silt; they intertongue with Sand predominates in the Carson River delta area west ; I Pale-yellowish color and moderate induration-both the deepest ones, in the deflation basins bordering Vpsal nontuffneeous lighter colored sand, silt, end clay. The of Fallon, and interbeds of gravel and sand, which may I 1 the rh-er, occur locally probably the result of development of the Churchill Itoglack, extend 30 to 40 feet below it. The subaerial .4 tuffaceous beds are geuieraly scell sorted, evenly bedded, be fluvial or deltaic deposits of distinctive of the upper 10 to 20 feet of the beds are too small in outcrop to map separately; they and moderately to well indurated; they Appear water (see logs 15L tid 21L, table 12); beds containing Ap- soil-are I sand where it is not eroded. The yellowish oolor is most are most common in the western half of the area. The laid nnd are probably laciistrine. They thicken toward preciable organic material are lacking or few. The i beds in- pronounced in the uppermost part of the sand-cormn Wyemniat formation generally underlies clay of the i lUpsal Ilogihack And probably intertongue with the proportions of silt, clay, and highly organic monly very pale brown, yellow, light, yellowish brown, Sehoo formation with a sharp conformable contact that suilbaerinl tuff sid tuff brecein of the hogback (p. 38), crense toward Cnrson lAke, Stillwater Slough, Still- or browviish yellow (l0YR 7/4 to 6/6); this color de- is readily mappable wherever itis exposed over a verti- butt the zonie of gradation is poorly exposed. These water Lakes, Carson Sink, and Eightmile Flat; locally creases in intensity downward, but commonly even calrangefromabout3,870to3,990feet. ThetVyemahn relations suggest that tSle tlffneeous beds were derived beneath these lov.-lying areas the upper part of the exposures well below the soil profile are pale yellow is yellowish or brownish well-sorted sand and the Sehoo from erillitions of Wyemahn Age at Upsal }logback. Wyemahn is organic muck and clay (the transitional (about 51' 8/4). T'ne induration is caused by calcium is light-gray clay. The sand of the W1yemaha is an In mniapiphig this tuffaceous fAcies the olIter indefinite facies is illustrated by logs 141,, 191,, and 27L, and the carbonate cementation, and is most pronounced in the aquifer, and where it is exposed the Wiater table gen- bounidary was placed where at lenst half of the beds lowv.lying faciesby logs 38 and 62,table 12). The more of the Churchill soil. Slight to erally is within a few feet of the surface, which is contaiti at lenst 5 peicent basaltic grnins. The tuffs- highly organic sediments are dark gray to black and calcareous horizon ..1.1 moderate induration commonly extends 10 to 15 feet generally costed with white etflorescent salt, and is cetus facies generally extends no more than 112 miles hare a strong peaty, and in places, hydrogen sulfide below the soil profile, but nornmally the sand at greater either devoid of vegetation or lis only sahtgrnss, or fronm the hoglack, Nlit along the partly buried horst odor. Well drillers call these sediments black gumbo, depth is not indurated. The indurated part commonly rarely, pickleweed. I that protrudes southwiard from the hogback it crops black tule clay, black tule sand, black clay, black sand, ii basins for 4 miles. Part- and Stillwster Lnkes shows cnide very coarse prismatic jointing, as well as The siallow-lake sediments, everywhere dominant, Ii out intermittently deflation and the like. In the Carson Lake carbonate conrentrntions along bed- are largely sand and only local beds or partings of silt ings of lnsaltic saud have been fouind locally in expo- areas, where they are especially proniminent, they yield local White enleiuim hit severnal ding and joint planes and cylindrical calcium carbonate and clay. The beds are various light shades of selres And horeholes severnl miles froni the hogback smiall amo,,its of smtiirnl gas (p.-114, 115), petroleum by carbon tetrachloride extraction root casts. In eastern Wyemahn Valley and on the yellowish-brown and gray medium- to fine-grained (section 2, talle 10). tests for piedmonts enst of the Bunejug Mountains, northeast of sand, generally unconsolidnted, and well sorted. They Blocks of black vesicular olivine basalt, commonly 1 were negative, .1J~~~~~~~~~~~~~~~~~~~~~~~~

BoTns" -"UM s9 CAMIGIC DA83RT, XSY N SAKS SAltONTtAW: 050LW0. A aular:frag- sandy msola h t benat the meetly send, grt mad mal-aff-iaa Whate the uppor indistinctly to.we- aw-lyinsg araC clay of the bla formation commonly Mm_,,and is pooay msted and ads directly on highly organic black ea and miY clay bedded; it apparently Ua t lialmitd aehaa~ly. .. I msat Eigstailo FlaUad In phase ia tle [Uuo muck), to I towt -ace MA CutheAage Wat of Caresss Sink and in thes CAtiN. cmiln a few hOk Am-hellt . ,.1 Alks.Stihwaler Ikas area,. The top of the sauk bedsk damlem i -frovtela|tely tedscatate feet thearebtintre larger ftagmeete ate 00Ube sad *at an o-atde of about feet alg Stiwater gIoagh an a*ou ,9 feet at Eightsile hML At and tat The blocks ao ieatic to bIlnrmediate lave, ightmils Flat the Muckis highly solmf, probebly be. %olike the encllg tla; probably they m from- ltafrm the asne highly Mineralized vaderlying Tetar lave, The tag beds gnerally otf m from and MP atth el othftlh t;dewhete it dip p to 1ie radially outward, f1Pttemin away .n .alins. th eratas, but clue to the enatrs they locally hawv is 4sages in dip became of nser wela sediments, hbich at tentatively teeper dipe " well abrept lttheir faulting and local cformity. Thin ttt em to lated withtbeWhyem afotanatioiibcn tuifactusa of mady or organic beds and their inteefinger with nd grad into the baakk igh proportion the Wysnah formaetion (P. i7), bet the - of thick clay units, etend at lest 100 to 110 feel. of between the Seeoo Nd the Wy.- of gradation is poory esposeL The tat is overain by set belot contact tote of the lwer ad dmadritit me- I14Y714 ISLandlL, taIle 12), but th gravel, send, and nrh (logr The lak gravel com- ofthe formatien cannot beidentified in any of the has of the Sehoo formation. Wycomeh In manly cbmely resemble the tug in the muter pau of t~h , the mailmen thickneb of the because it Warderived eey from the tLa, interior may be considerably the conee busbeurfceof the basin but generally It is km indurated, better meted, mo regularly bedded, and in place. containe lithoid or kI corailine taft of the lower member of the Salom Three collketinne of hisbone fren the uppesocet Large vuptione at Upeal Hoghack in Wysmahe time ofl land wereexamined by D. Dunkble ofthe are mgeted by the apparent gradtion and intr .5, .8 Geoogical Survey. One collection, from a d4da- looping of the edarialtat with the Wyemes for on-arpeilwmire 1.4 miles east of the Upeal Hogck ti, and by the h dneo of batic mateal in * e, I. posiby either RhabUde r or sim... The the tuffomos faeiec of the Wyanaha near the hogback "WeM U-A. caepduo "P sanow oe Cawam 4 kmP her two collectionr, one from thde a bank of the and a decrease in thie material away frm it. The Itnliverianec19,T.91 NIL3O ,eandtheotbhr ema may be ldaer than the Wymaho-4ieir one afts sies iesWd o- ' ineIcsa" b. le. a agup in ee 8, T. 11 ealer a bede thb Fallon-Lovelock cutoff ag telatiomi to heal. sediments. ar not euposed-4ut go i Sr u.5h's Oai of opsaw at "mie Labs SOi-ds two atWw Nmeabe sawai samanse IL R9F., he identified as nixttrns of perape thet is no evidence of the Eta foirnatim or earlie so.drs~iSi We of (family Cyprini- er (family Catotomidae), carp snits en thes The Main ruptions ended before lae e' Cttidae). o amere hsabr. a.1=LIL.Itss km. mIL S. b),a posuy ai a bulhead (family Wyeeaahe time, for the upper peat of the Wyeahes are diagootic of age became I o of the collctioma is largely devoid of basaltic materIaL imee. mm we anus 544s to sear th bogbek (amuc a se h gen and familis rnge frem late Tertiary Th two thin beds of bookic mend in the lowr part of the Seob in the northera past of the Stillwater qad, rangle (P. 59) ar tentatively correlmatd with oerptie trongly developed than any younger ml4 thoug e- 'I at Soda Lake became of their large content of non- miderably kw em thea the Cocoon maL It cnt be Upel Hogbeck, 10 mike norts of Fealln, isa er*es basatic grains although they mig rord minor et- e wher it is ouperpomed me relict _ _r..... tag thba are pestly or f overlapping caom Iousaltlk bea t the dying phame of activity at the pbwSc of th Coc lbecaeil it is mAa byb5 the lue irely of Wymaha age. Interference by younger by eolin read les eb- etrager develomet and widespread covering The Churehill adi ba be au bv tlkitadO llredth g relatiom et the elder comes, but at loat i a shallow laetthat ozitedwhilolthe ail whsfuming assan" cnar . antun ranging from 3,0 to ,000 feet in the MP ans. It oemlead.rI ad piy 7 *entaaraevidenaL The two Oldedt aO g forms- he net been fond below 3,S faet, lthough it prob. the noethwet and southwet edge of the sariea; N. mile No l1teecalated with th WyWSa ably mereutended lower and wseaed b' the ttai- ryp lecalmyn-The type loclity for s eil is 1time Atrngly edneeed il trtig l SEi/41I/4 me15i, T. 18 ar moat eoded very poorly expoord and may he eoft rly Sehoo Lake. Below atit of Cherchill Valley, In the than the Wyraih fonation Probably the liee the yorna earrial beds of thic foreotien, N, IL0 IL (ectieon 34, tablo 1; peol S, tableb ; cir- NA is eler then the Sbeoo and Indian Labor 3, Otoel feet in ,he ubrfaceofltebriinterior, on eelian mangast is at the mth end; its cnter is roughly however, its stratigraphie position, *s determined by direct ad fF I&A, R), when theb ll,ideraloped formatlons. nialh i called the Churehill eil anter andAs ove a con- cular and *bout hU a mile in diun etert meem to he rprearaed by the mud of tbh Vyeymbh formt Its typa locality, Churchill Valley. The Churchill mem is tracing by borehole., alluvial smd of the Indian Lakee forms1 The coa. ar e omnpored of well-Induate bemis mew or Iee highly organic ail, clay, and mnd in the fIrmably by divine-tidk (pierit ic), in plab cn was previously referred to (Morrison, 1961., p. DIIS) tien Mnd gravel and end of the Sdo formation IL cinder tSal, highly It is much mno uppers" pert of thb Wyhenia foerma ie, lid down taining *e mmcl - 0 percent divine. The tuf ia sthe middbl Lake LaroutaneoiL .I I-2 L.AKELazoNrrA: GEOLOGY, CARsON DESERT, NEV. '.1.1 QUArERNIARY 5rrtnATIGRAPIS 41 is preserved with almost no subsequent subaerial and free of calcium carbonate, and has a pH, determined by this formation lake erosion because of prompt is fully exposed in many places in both burial and a Joeation colorimetric field tests, generally between .65 (slightly A highlands and lowlands; exceptionally sheltered from waves. IIi it is the most widely exposed acidic) and 7.6 (mildly alkaline). Determinations of of the Pleistocene formations. In the highlands it con- pH by glass electrode, ROVSlmCRN&&CSX1MICS however, range fro,4a8.3 to sists of Incustrine gravel, sand, and local lake silt, clay, 9.0. A slight concentration of silt and clay commonly and tufa; the maximum The Churchill shoreline is at an altitude of soil is a Calcic Brown soil throughout is evident in this part of the horizon: Mfechanical analy- about 4,370 feet Along the base of the the relatively narrow highland shores, altitude range in which it occurs ses of samples (freed of organic matter) from several between 4,000 and J,940 feet, the formation changes in the map area. Relict and buried occurrences show localities showed 7 to 18 percent of particles less than facies, through a narrow silty zone, to clay that under- no appreciable differences in profile chiracteristics. 0.02 mm in diameter. The sand grains show little evi- lies all the lowlands. The full profile is rnrely seen, for it generally las been dence of corrosion. The type locality is the more or less saddle between Sehoo Moon- eroded. It is well preserved only in the In the lower third or half of the horizon (the B. or tsn and Eetza Mountain, at the most protected mountain reetaranta west end of Wyemnaha and valleys below B.. subhorizon, transitional into the C,. horizon), the Valley in the EI sc 21, T. 18 N., R. 30 E. Here, the highest shoreline of the early Sehoo lake, on gravel color gradually lightens downward, structure becomes typical lithologies of highland shore occurrences of all of the Fetza formation in the narrow zone between the somewlhat weaker, and calcium carbonate concentration members esrly of the Sehoo are represented, overlying both Sehoo high shore shoreline and the Lahonten gradaaally increases. eolian sand of the Wyemaha beach, and locally formation and gravel of onl colluviumn and alluvium of Eetza The calcareous (C-.) horizon normally ranges from the Eetza formation (pls. 7, age and on the 8; sections 41-45, table 10). Wyemaha formiation in the highlands 2 to 4 feet in thickaaess. Its upper boundary is 2 1/2 to The following further above the lauhoutata illustrate tIue stratigraphic rela- beach. 6 inches wide, that is, gradunl to diffuse, and its lower tions and lithology of highland occurrences A vesicular horizon of this lIss not been positively identified boandary geaterally is diffuse aid irregular. Concen- formation: figiares 5,13A, IsA-C, in any buried occurrences and 25; and sections of this soil. Such a horizon trntion of calcium carbonate characterizes this hori: 32, 34, 40, 50, and 55 (table 10). The following is locally present on relict occurrences, illus- but it is probably son-strong in t(le upper part and decreasing down- trate lowland occurrences: figures 9, 12, 16, and 304; younger than Churchill soil because it locally crosscuts ward. The concentration generally is iraegalar: most andsections 3,7,18, and the top of the 29 (table 10). oxide horizon and closely resembles the of the calcium carboaate is concentrated in whitish The Sehoo-Wyemaha vesicular horizon of boundary is generally clearly the Toyeh soil. On relict occur- streaks and irregular or mottled disseminations, inter- marked and conformable rences n layer of Ing or only slightly disconform- gravel commonly overlies the vesic- spersed with more weakly cemented material, which able: on the highland ular hori7.n. Genernlly shores it is the base Inke gravel the gravel layer is only I peb- generally is light gray (IOYR 7/2), very pale brown and sand (Sehoo) resting on eolian ble thick and similar to that on relict occurrences sand or alluvial of the (10-R7/3), and pale brown (1O) 6R/3). Consistence aaa 4--Cbaeahaaa gravel Cocoon .att. daleaaoW as n.,ia. s,ea af Wy, b.. (Wyemahna); in the lowlands it is the sharp con- and Toyeh soils; it also is presumed to be is slightly hard to laard and structure is massive. Be- f-floo (Q.&)sa. 4nb,.,1-d by sm-na at a-.r ae,.breat Sebas formable ta.aaaaaa tqe0 sad contact between clay ciad sand (or between younger than the Churchill soil. The upper surfaces of cause of the calcium ,and of as-..ad daadraate -b-a~ at atlaS carbonate cenmentation this horizon tsW. Tb. 6"M~ at asset meabtr afth fbsaboaa. ,.aa.aa., aba. nonorgenie clay and organic Sand, silt, and clay) de- the pehbles typically are coated with desert b-a.a Ia-htr varnish, is somewlat resistant to erosion. Both colorimetric tht. ... ,bdilt twa atan, saVtas a. asada scribed on pages 36-37. The ChurcIsill soil which is somewhat better developed than that on lag MM-t~ -n~aaawd.4by tbn.-1y a1bha aMbt cCAbasts is a field tests and glass electrode pH determinations range btu.a.seu. food conspicuous gravel on the Toyeh soil. altasr .aat a,, at fitanb.. Moo..aM.,s marker where present, but it is absent (ap- from about 8.0 to 9.4 (moderately to very alkaline). VtSfoot b-.aa - Ab. -n 10. t 45 ,atttedt.T. 15 St. R. 31 A. parently eroded) in the lowlands. At The oxide (B) horizon is about 12 to 18 inches the base of the in full Dowatward, as the calcium carbonate concentration de- highland shores and on the Carson River delta the thickness in the few pIlaces where the soil is preserved creases, t(le coaasisteace changes to soft, and structure boundary with a calcareous (C,.) horizon tait is considerably thinner, is locally gradational and indistinct, as the little apparent erosion. lWlheredeveloped on eolinn to single grain. clay at the base sand and less strongly impregnated with calcium carbonate, softer of the Sehoo formation changes facies sandy colluvium, this horizon is light brown In eolian sand, this horizon is thicker and the car- upslope to (7.51-R 6/3), pale and less resistant, and somewhat darker. sann and the shallow-lake sand of the Wye- brown (1(\1-R 6/3), light yellowish bonate more irregularly dispersed than in other mate- mahn changes to eolinn sand and alluvium. brown, (1017R 6/4), and Even in locally light brownish gray rials; moreover, the sand generally is weakly indurated BEH00 FORMATION such places, however, the contact generally (10)I R 6/2); consistence is slightly hard to can be drawn hard, nnd by slight calcium carbonate cementation for about 10 GraNRaL ratea2sa within the aecuracy tolerances of the maps. structure is weak to moderate grades of coarse pris- feet below the true calcareous horizon (fig. 13B). Two major coeval units in the Lahontan Valley group The Sehoo formation corresponds to the "upper lacus- matic, coarse columnar, or conrse to very coarse sub- Cylindrical calcium carbonate conceatrations, which overlie the Churchill soil aud Wyemran formation (and tral clay' of Russell (1885), and correlative sdore anigular or angular blocky. On gravel containing mnfic were apparently precipitated abotat former roots, are older unuits, locilly, where these are missing), and are gravel and sand of his 'second rise of Like Lahontan." volcanic rocks or on grovelly collivium of Fetza age common; they range from one-fouarth to three-fourths discontinaouasly overlain by the Turutpah formation, (See p. 106 and fig. 38.) It also corresponds to the that lansbeen reworked from the B horizon of the Co- of an iach in diameter and have tiny hollow centers. Toych, soil, naudFillon foranation. One of thlese units, deposits of the "Dendritic Lake" of Anteva (1925a, coon soil it rommonly is brown (about 7.5)7R 6/a to In gravel of calcic rocks (for example, basalt and ande- which has been named (Mlorrison, 1961.) the Sehoo 1945, 195!2). IOYR? A/3) to locally reddish brown (51YR 5/3), red- site), this horizon generally is about 3 feet thick and formationa after tIla Sehoo Mouaatains, consists entirely Gravel and tafa of the Sehoo formation vary con- digl, gray (51)R 5/2), snl (lark reddish grny (5YR has more calcium carboaate than in eolian sand (fig. of Inke sediments. The otlaer mnit, wlhich has been siderably among the four members of the formnation 4/b2): ncoasisteneeis slightly Ismrdand strimcture is single 14). In Inke clay it is only 11/4 to 2 feet tlkik, and named (Morrison, 19lna) the Indian Lakes formation in detnils of litlaology and distribution, as omatlined in grain t1 anvenk grade or ciiase granular or coarse sub- the carbonate concentration is natsually strodg in the after the Indian iakes northeast of Fallon, is predomi- the following sections and in tables 4 and 5. Sand naagtalar blocky. upper aalf owing to tIhe low permeability of the clay. nantly subacrial sediaeuts tliat locally is less variable in lithology baat differs The tapper half or two-thirals of tlae horizon (the B, intertongue considerably Compared with the Cocoon soil, the Clhurchill soil vith the Selhno foranntion. among the members in distribiation. The clay unit. subharizon), complaread witl the lower part, is somewhat las no oxide (B) horizon (last is less clayey, softer, TIba Sehoo format ion records the late deep-lake period wlahielincludes silt, is tae least variable in both se- darker aiadlanrder, lIms somewhlat strolager stmrature, is weaker stmructured, lighter colored, and yellower; it has of Lnke Lahoaitan. Ualike tlae older Quaternary units, spects; its geracral characteristics are summarized below. N Amoco 'I LAKE LEHONTAN: GEOLOGY, CARSON DESERT, NEV. QUATERNARY STRATIGRAPHY 43

TAUZZ4.-Pri4pst lifferexsee ,. gravl unit of thi S"e1 foraJlion

... -br D. . -b. 'I Cbneaoiurlasle ____t______l___,T.-csssiUpbaasPapsi"bpb

Approlnsate 3,950-4.370 ft (420 4,00-4 370ft 4,0t0-4,190 ft (150 3,930-4,190 ft (260 3.950-3,990 ft (40 Jtitiude range it). (260It). !t).-t). ft). buto0 .... Most widely di. Widl distrib. Local .. . Very lota; rare be- Rare; restrieted to tributed. utd. twee altitude. of hih bhore oan 4,1 15 and clo.e to moun- 4.170 ft. tael.. Thickness - Generally thicket 0 to locally more 0 to loctlly more a to Inel 0 to sevderalfeet. of the gravels: I than 4 ft. thin 4 Ft. than 411ft. to locuily more than 20 ft. . Lithology. Cosiest;n2a0ely Mainly fine and Mainly Oineand Mainly fine and Fine pebble gravel, cobble and smbal nedium yebb mediue pebble very ine pebble commonly sandy, boulder gravel, gravel general- gralsomne cob- grvel Bose grades to pebbly ;.'I and line pebble I'clean, not legvl;e- mdiumn pbble sand. r grvd; gnerally sity. ea lly well grave; Irtedgenerally little or no nnd. and el rounded; iner and lesm el 4 but locally sandy, loenlly sandy; sorted than trans- ill particularly over generally India- gressole phaseof .e eolin sand of the tinguihable from this member, Wyemaha. regresuivelake commonly sandy. gravel of lover member. Tu5a (scc table Generally no tufa in Local asterSon Dendritic and (or) Local aterorn Tufas of thi mem- t1ow-er p art; local fregn,cnts of lithoid tufa of frafisento of ber generally ab- lithoid, corallise, lithoid. corel- this member in dendritic and sent; local frg- k and (or) cellular line, and (or) placein upr older tufas. mente of older tufa of this mem- cellular tuba. pPart; lMgf ra- tuoas. bee in place in ments of older upper part. tufar in lower part.

Clay of the Sehoo is by far the most extensively ex- In the Fallon quadrangle the clay unit reaches a maxi- posed map unit in the Lahontan Valley group, aggre- mum altitude of about 4,120 feet in highland embay- gating more than 100 square miles or about one-sixth ments and progressively thickens toward the western of the lowlands of the map ars.n It is the predominant part of the Carson River delta, the source area. deposit exposed on the flats and dry-lake beds, and in In the lowlands the clay unit is predominantly clay Carson Sink it is continuously exposed over an area but also includes local thin beds and partings of silt, more than 22 miles in diameter extending minny miles sand, limestone, tufa, and volcanic ash. It is relatively north and northeast of the mnp area. The best sections uniform in lithology, both vertically and laterally, ex- are exposed at the scarps of deflation basins and in cept on the west delta of the Carson River and locally drainage canals. near highlands. The clay beds are silty clay to clay, In the Carson 1Ake qundrangle the clay unit of the in places very plastic when wet, and locally bentonitic. Sehoo normully extends no higher topogrsphically than In the eastern half of the area the bedding is mostly the base of the highlaind shores, at an altitude of about indistinct and has faint lamination, though the upper- 3,905 feet (fig. 15C), and has an outer selvage of silt most and lowermost parts commonly are well bedded. generally less than a quarter of a mile wide. which ia Westward the bedding and lamination tend to become transitional into the soind and gravel of the highland more distinct, and near Lahontan Dam (west of the siores. In severnl of the intermountain ssddles and at map ares) the lamination is bzally varvelike. In fresh IHidden Cave, however, tongues one-half to 4 feet thick exposures the clay beds are generally very light olive IaS.la-A, 0.1me * loer *.ebe t Sebsofartate (tOn.) a l-bInsereHa. sssd at Wy..ah fta.lo.t tt-. a.d a-asI at Ert.a of silt, minor amountsof interbedded clay and sand, and gray to light yellowish olive gray (5Y l/1, 6Y 6/2, rorms~IlasIsQ -relo... tyrrerl ot s..r beltrred .s...ainW lt. J belowIbs Laho.tl. breb. 5Sslhs...t odreo sesja I .oat.tai., locally limestone exend into the highlands as high as bY 7/1, or bY 7/2), locally medium to dark tan-gray, NWV- -ns. 3 1 ssner--7di. T. 17 N, R. 30 MI. P. Orrl dP te sftXebos trrtla a. gravel.. I weEg forostlos. N.itb rdr- ot Wbhlr r-b r Mio..tala, rs - . r. maN.. t. " r.. sIliad aboWlA.70 fret. C, Ilmt-tgemble deliU tyl.1lrrlr -s 1good nbout 4,100 feet (pl. 8 and sections 39, 41, and 42, and light greenish gray to nearly white. The prevail- ,r.P-, -u. Al ba.e. ers 1 eF Er,,M-.foro.lto s IQ,,). w hblsblr r .orlsia byrerby: C oil a,.luoft VW',obo ao atlos b,.. ls,,bst table 10). These tongues are oflshore sediment laid ing greenish tint is most apparent when the clay is cbah-hiil .ol 4Qw+C) In1 rssanot Ise aoll I. ra-lY erodod.Ibe PPe, Nsl Orta r'

sos-ass o-e4-4_ 44 LAXE LAHO~NTAN GEOLOGY, CARBON DESERT, NEKV. QUATERNARIY STRAMIRAPHIT 45

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'I lAo LAIONTAIW: GEOLOOY, CARSON DESERT, NEV. QUATERNARY STRATIORAEy4 47 -,

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LAKE LAHONTAN: GEOLOGY, CARBON DESERT, NEV. QUATERNARY STRATIGRAPIXT 49

generally is compact, hard, and tough, normally 'beak- r.d"00173 ing into irregular blocks bounded by joints and bedding laminae, The full uneroded thickness of the clay unit ranges from about 5 to 20 feet in the eastern half of the low- lands; it is thickest in the Carson Lake, Stillwater Slough, and Stillwater Lakes aress-probably because these low areas acted as sumps for collection of sedi- ment. In the western lowlands the unit thickens to- ward the west delta of the Carson River to commonly 30 and locally more than 40 feet in the upstream part; ) I it is about 60 feet thick where exposed in bluffs and adng wellinsecs. 4and5,T. 18N.,R. 27E. Most exposures show only a fraction of these thicknesses I because of widespread deflation. EI In the upstream part of the west delta, west of Soda Z Lake and the Old , this unit occurs in two zones within the Sehoo formation, separated i and overlain by sandy zones, The lower zone is the -EI thicker of the two, more clavey (generally silty clay a and clay), fairly coherent, and forms prominent scarps E in deflation basins. The upper zone of the clay unit is mainly silt, relatively incoherent, and rarely forms I ZI scarps These two zones are the high-stage deposits I of the lower and dendritic members of the Schoo, re- ItI spectively (section 7, table 10). Most of the lake tufas for which Lake Lahontan is famous are in the Sehoo formation. Twelve principal varieties of tufa occur within the formation at nine distinct stratigraphic positions, They are described in table 6 (figs. 16-24) and their relations to the prin- cipal lake fluctuations are shown on plate 10. The cellular and dendritic tufas are by far the most domi- nant; they are especially thick between altitudes of about 4,115 and 4,355 feet (dendritic tufa extends only as high as the maximum of the middle Sehoo lake, about 4,190 feet). Russell's (1885) "lithoid" tufa is mostly in the lower member of the Sehoo (9lithoid tufa of the higher shores" and "cellular tufa"); minor amounts are in the Eetza formation. The distinction between lithoid and dendritic tufas is less definite than Russell implied, as all gradations exist between the two types. J. C. p Jones (1925, p. 20) found this also to be the case at Pyramid Lake. Russell thought thait all the lithoid tufa was deposited during the first deep-lake period of LAke Lshontan, and conversely, he (1885, p. 114) considered the presence of lithoid tufa on high-shore 7,o.- S -A . I S t~ . t)CI4 tat. at to.- a- , at M fti gravel emlbankments as proof that they were formed tora tioa. S4.., otth ad" of c -o,. 5h.a. a. IL53. . 21 N, IL during the first deep-lake period. This accounts in ssr~ 3.s . Is to S.. I .e . a... n .. ..ajfaC o .. f t a o ft part for his error in interpreting the relative heights otLt. c. L~it Id Wot titIS. -o 1 -~ot hIght..d b.50'. o I. ". 4, of the maximums of the lake during the early and late ., 5.o th. R1h% o toatto bo ld -. at1 7 I.t fto ..o o. W 5 .deof 54... *.1*. S 'A~ta- . 15. T. 18 54.. R. So IC. Fla I. deep-lake periods (Eetza and Selhoo times of this re- IS la-b. taot. 4, ff fl i

.1 LAKE LAISONTAN: GEOLOGY, CARSON DESERT, NEV. tQUATERNARSYssWMsTIRAPHY 51 -;<-F I port). The evidence to support this conclusion is sum- marized on page 64,65.

The Sehoo formation intertongues with the subsecial Indian Lakes formation described below. The three umaindivisions of the Sehoo are each defined as a mem- ber of the formation (pi. 12): the lower, dendritic, and upper members; these are believed to record the third, fourth, nlidfifth major deep-lake cycles, respectively, of Lake Lahontan. The three members reach altitudes of about 4,370,4,190, and 3,990 feet, the maximums of the early Sehoo, middle Sehoo, and late Sehoo lakes, respec- tively. A thin, fourth unit characterized by thinolite tufs lies between offShore sediments of the lowver and dendritic members. The members aie not differentinted on the qulndrangle geologic mnps, although they are in, the special large-scale maps (pl. 7; figs. 25, 29, 34) and in manyof thesections in table 10. The lower and dendritic members are further sepa- rated, at altitudes above 3,990 feet, by the siubaerial sedi- ments of the middle tongue of the Indian Lnkes forma- tion and the unconformity that records subaerial ero- sion which locally represents this tongue marking n Inke recession nt least this low between the early aind middle Sehoo lakes. The dendritic and upper members are similarly separated above 3,900 feet by the uppertongue of the Indian Lakes fornmat ion and by the uiconformnity and soil that locally represent this tongue, indicating recession at least this low between the middle and late Sehoo lakes. LWEW UZUSlE The lower member of the Sehoo formation consists of licustrite gravel, sand, silt, clay, tufn, and volcanic ash. It extends to an altitude of about 4,370 feet-the highest shoreline of the early Sehoo lake-about 10 feet below the Lathontan beach; this is considerably higher than the other members. It comprises about two-thirds of the imeroded volume of the whole formation. On highland shoresthismemberismninilysand and gravel, and a little tufn, silt, and clay, I to 50 feet thick; in the lowvintds it is mainly clay and some silt, sandlufa, and volcanic fshi, and I to 30 feet thick, being thickest on the Cnrson River delta. The type locality is the site of seetion 34 (table 10), in Churchill Valley at an alti- I . t ude of about 4_00 feet. C S. l oi e.- A "r t, -p ,co o ' of 0011.1-1, t t Of I 0.. , -0 0 Of Gravel of the lower member is domihant along the m:,a l shorlinets of the eirly Sehoo lake (pl. 9) std Mor., IT .-A , Lfth~td iW. oe fao ales., 5155, 5 ,to f Of to.." -.o ., ot 5, 0 fol... o. -.tl n e t - -. t.'.oo so . l. of Io... 4 _.oe 'r Sorth,.. ..F' . 5if to~W V. - . 21. T. IF N.. IL SOE.: .illod, 4.240 foo- N, H..fd ,. 0t, , Xo.t IN -O I,, A. Z~ o,,. o of 1 -.oo1 il 1o. o . N IV% -0' 14. T. iS X.. R. 24 K. typienly is thicker, onarser, tindmore wideslpnad than roo.- o oo -of0 in~poo Io 0 ot IN.I.ho 'O. o _ -o W ay M. t.5.. P.11 - t.l. C. Hi..,i .s - i of tsIo 1. i 5004 0 . 1t -n t , l M 0 o 001 1. 1 ,, ,l~t o OS llttho ld , nt. of C t. o , . the other gravels of the Sehoo (table 4). It ranges ili -- M.tita to~. of Io.... s. o.. ~ or IN, S h50. Poll -0 1.. tiol. ol - W1, C. C o,.,t1 0 - 1~.r. of , r u t b151,111, 0 Moodo, -'..uo .110 111h.01dl of. ,,! II o1r1 o l lblahlod h~.- lhicktie-s from I foot i, shelterr/l reedtranits to miiore or ' p ,, o .0,l.n1 , S ol ,- n. ., ..l g,, of S ol o 5M .1~,0 thati :t0 feet it some enmbanknieuti. s~sr fta 1110,1'. 'A1 -,o i . T. 18 N.. R. 50 E. G,.d..tto ,, 0 spit Oi lnonllt nin- o l, Io "5t, I .0 5F 1 oiua shores that. were Iost exploed to wanves, it. is taiuly LIKE LAHONTAN: GEOLOGY, CARBON DESERT, NEV. QUATERNARY STRATIONAPEY 53

A

.C ~C

. it. C. tat. lbftdk aotftIrtat- oatao A. I. . dotlao~tl- ti t at d.ak d,.tob,ltk r of N4ho fo.ttioa topmd - ..*rd*t Io, D .tabo.r tthe bo.. Fiaga. 20-Doaddtto tat. d"41tltt -..t~ of Sotao 4o~ta Mcr.. I9-A. Lorof nt-h tdt of d44n1ilt e noti: .d C, a. tttq,nb. tt.. 0. bh.o tI- -oto. ttoa;t;t rtDthn th4t rwftf-it; . attfe l-t rgot or ocb *r ptotd.o.t ...tbrat of C_ It ...to.. E, ae. S5. a.oro ( T. Id N.. R. 31 r. P. CT-P od, Ik or P to..: 0-.. nta.t.. e,1; ot ,trndtttrItot. t-ro ot.r-- ttt1u.tnd tn A. ht.nt-n t tt -.otu1rs1ttttrt .bt of boat part.;mtro Ie, or Of *m ttFh-d- .ert.tatly os-rd M.tn oa--, bt; toot .*a tat. -btd ; iltbold t.f. (.I . t lb.dtoadttlt ater ota Ibe app-r atb. .ooA p 1.tt btot. bat, ftit to-datatnd G-1-t1tt-. O plo taitt -r I ta-t .t,.o. C, II.. tttooof ... t tI$ 'It A-Jtottk tIrI a-rrml ptw-rIl ft.0, ,l.b of t.o..trtooW t-o ro- L.r-rIt -hoad" Ia abot 2 Itt,. It. diotor. Nato .pt. of 01o'rotott.tal; IalPtltd tittold taf. no Outer -rF0.- Ortop. tad.. U r

LAKE LAHONTAN: GEOLOGY, CARSON DESERT, NEV. QUATERNARY SToATIGRAPHY 55 A

I, - .; .t., . . i 4

710V.. 21 .-A, Thiok bl..hkt dopooft. of do-dlitlo W.f. N.It.l Rot. lo . l l .... fidd.. C -,. r...*. 22.-A. H.ld .d- of dooditto f to-otl If *ttt lo X, Cl-..,t M .fd-e -. of 4W. l~tk Wo. - . diff It IooIlttg h. -. t A. .1~ Wo. - J.b.2 to ft b- 21. .bol g d~t.1. W I.1. of d.... o. d f.d~gl 00t .f lb. Wo. "bb -- D..5 Lt.t &.d ittl. lo. -h.od.," - M.g1.0 1.11 4 Oth.. t.l ..d o rh lby Y. ..o 1110.1tlo ; .2 b ob..g b tU. W . ,o ro M .0 . Ofd..df ttk - 00 oftt b oo f r to- o 57 LAUZ LAKONTAN: GEOLOGY,CARSON DESERS, N V. QUATERNARY BMTRAGRAPET boulder and cobble gravel; in sheltered valleys and intermountain saddles, it is cobble and pebble gravel (fig. IA). Thegravelismostlyreworkedoldergrmvel; only a small amount came from wave erosion of bedrock as shown by the paucity of rock-cut scarps and benches of early Sehoo age (p. 6344). .11 In places transgressive and regressive phases of gravel of the lower member of the Sehoo can be dis- tinguished, especially where they are parted by sand, silt, clay, or tufa. The transgressive gravel is generally coarser and thicker than the regressive gravel (table 4). * Sand is more widespread than gravel in the lower member, primarily because of the abundant eolian sand of the Wyernash formation from which it is mainly de- rived. Sand is especially dominant in intermountain saddles and passes such as Wyemaha Valley, the saddle between Rainbow Mountain and the Stillwater Range, A and Simpson Pass. Here it normally is I to 10 feet thick, and rarely as much as 35 feet thick in valleys. It intertongues with silt and clay far out into the basin on the Carson River delta west of Fallon, but elsewhere this intertonguing is close to the foot of the hillshores I and is not present in most of the basin interior except as local partings (p. 59). ."1 and regressive phases An be distin- 1I Transgressive .. I guished locally, especially where gravel, clay, or tuft separates the two sands. Only transgressive sand oc- cure below an altitude of 3,990 feet, which is the ap- 11,I .1i proximate lower limit of the thinolite lake recession. This unit is mostly fine to medium sand, loose and uncemented, well sorted, well to indistizctly bedded, and pale yellowish gray to very pale yellow. Locally it contains a little gravel, as below gravel bars over- IJ.' lying eolian sand of the Wyenmaha formation. Some thicker deposits in valleys contain interbeds of light- tan and brownish-tan to browrn-gray silt and silty clay. b A pale-greenish-gray to white ash bed, half an inch to 20 inches thick, occurs in the lower part of the sand below an altitude of about 4,100 feet in valleys in the northeast Bunejug Mountains; it may correlate with the main ash bed near the base of the clay of this forms- tion (p. 59). Ostracodes are common, and form a coquina in some layers. Where this sand overlies eolian sand of the Wyemahha formation it commonly is difficult to draw a sharp rarely are good enough to colt. ah a.. boundary because exposures . 13.- A . hr!5 11tbI4 tat. .t app., a mS,? of stat. ta..eti... Mosiert t3,pkat tada- tr t. : bit. pi". I. Fire ed. .. .t a.,be of lake reworking. belt,, .-,f ta aibse. a . tag aa f, a .C ass... ,lb of H are.. 5th..!. 5.9 0 foat *tiheda. A.,C. B ..d ap show the lower limit of the zone tat.. 0, L at* 311h.14ltat of apt., ls tab., at tha Sthos. Clay of the Sehoo formation is largely in the lower two members and the thinolite unit, for the upper F-es. 24.-A. ULttboll t. af AM5 Ma. ..ft at Fal . .UtM 5 !i.st Speeta . A dI~ttn .ot, a e t..t R. U th~at lta fta tbtt4 l a. member is generally sand. The lower members are rep- .. It at F.atte f -aatt... Tb~ stHaI," -t - Ibi. that MOe d* by zones of slightly differing lithology but ste toe-ra lb. era1c0t.. b,t -.a t .t at th. ..a tS hWteld . lisle resented ala. t p ci.,. ,aena A -4 - ta. catl n c.. I.,h. ar.stahue at lit* the differences between members generaly are not suffi- btgb.abat ot it, tbhtrt Felia. 1.k.. w% wr. tt. T. 1? Mt.,B. 30 E.. ciently pronounced to permit exact differentiation of the .b..t 3.515ft-t titittat. __ U______

LAKE LAMONTAN: GEOLOGY, CARSON DESERT, NEV. QUATERNARY STRATIGRAPHY 59

ANYNN1intO AWVIlu31 members where the thinolite unit (which is most dis- most likely source for this and the other pumiceoua tinctive) is absent (for example see sections 23, 24, 29, ash beds (Russell, 1885, p. 141). , I and 55, table 10). In general, the lower member rep. resents about two-thirds of the original (uneroded) TN5OLXTIr5VIM IA thickness of the clay, the dendritic member about one- The thin local thinolite unit of the Sehoo formation is third,*nd thethinoliteunitlessthan one-tenth,butwide characterized by the crystalline tufa known as thinolite variations from these ratios occur locally. and differentiated only where this tufs is present. It Clay of the lower member ranges from about a to 15 P. also contains lake day and silt locally, but almost no. feet thick in the eastern part of the lowlands and is more sand and no gravel. Thinolite is described in table 5; uniform in lithology than clay of the thinolite unit and it occurs in the lowlands and lowermost highland the dentritic member. It is generally somewhat silty, shores, between altitudes of about 3,890 and 4,030 feet, but has local partings and interbeds of silt, volcanic either as coatings a fraction of an inch to rarely I foot IL~~~~~~~~~~~~~I I ash, sand, and tufa in the lower part. It is practically thick on gravel or bedrock, or disseminated through nonsaline and is noncaceareous except for local dissemi- several inches to several feet of clay or silt. Nearly all H 4 I nated calcium carbonate nodules and oulites in the upper the thinolite is in this unit, but a little occurs rarely in several feet, just below the thinolite unit, and for local the dendritic member (table 5, pl. 10). .1 laminae of ostracode-bearing clay and ostracode coquina The type locality for the thinolite unit, showing stra- in the lower few feet. A layer of tufe ("basin-interior tigraphic relations and typical lithology, is at Wild- lithoid tufa," table 5), 1 inch to I foot thick, occurs cat scarp in the SEy4 sc. 4, T 10 N., R. 29 E. (fig. locally about I to 2 feet above the base of the clay near 27). Sections 24, 29, and 85 (table 10) illustrate its the west and southwest edge of Carson Sink. relations in the lowlands. In the northern part of the Stiliwater quadrangle Clay of the thinolite unit is a layer of thinolite- A,, I the lower 4 to 9 feet of the clay has a few partings bearing clay, from an inch to about 4 feet thick. The and thin beds of sand and volcanic ash, illustrated by 3 thinuolite crystals are slender double orthorhombic 1 arng ee, ,' I section 4 (table 10). Beds e, 7, 9, 11, and 13 in this I I pyramids of calcite (pseudomorphic after aragonite), section generally persist for several miles southward occurring either singly or in small clusters. They gen- - . . I V. ... .r-. .,.... A...... , r . -...,...... from the south edge of Carson Sink (fig. 26). The two erally are sparsely disseminated through the clay, but 'I. main sand beds, 5 and 9, have considerable olivine and locally are fairly abundant. Generally they are less endesitic or basaltic fragments in addition to quartz than i/s inch long by 1/32 inch thick; locally they (bed 9 also has abundant ostracodes). The elastic are bigger, rarely as nluch as 2%h by 1/4 inch. Com- rocks probably are pyroclastic sir-fall deposits from monly small calcium carbonate nodules and oolites are II small eruptions at the Upsal lHogback or Soda Leke associated with the thinolite, but the thinolite is more !. i vents. Volcanic ash beds 11and 13 are one-eiglhtlh iich restricted vertically. The clay in this layer resembles 'II or less in thickness and seem to be local near the south that of the lower part of the dendritic member, rather II Z edge of Carson Sink. Bed 7, however, is hi to 8 inches than that of the lower member. * .. cŽ A'.- I thick and much more widespread. It is exposed locally Clay of the thinolite unit has been identified only at ths southeast edge of the clay flat south of Stillwater locally in the ares underlain by clay of the Sehoo, be- V ,1: Point Reservoir and at the north edge of Eightmile tween altitudes of about 3,890 to possibly 4,000 feet, I a Flat, near the enst boundary of the Carson Lake quad- from near the north edge of the Ltihontan Mountains rangle; it has been penetrated in boreholes in south. northeastward to Stillwater Slough and the flats east of the Stillrater Lakes; it extends several miles beyond i central and southeastern Carson Sink, and near the .... the east edge of the St illwater quadrangle. The clay atI Stillwater Lakes, Indian Lakes, Stillwater Point Res- I.,i is rarely exposed but its subsurface extent his been I.I Lake. It is pure- 111! 11 : : ervoir, Stillwater Slough, and Carson traced by auger holes. It is exposed locally at the west 'I *t. white well-sorted pumiceous ash of very fine sand to margin of the clay flat south of Stillwater Point Res- 0. .'.. fine-medium sand grade size, uncemented to locally 0 :.i erroir, on the shores of this reservoir, and in the U.S. I hard cemented. It is the most distinctive stratigraphic Fish and Wildlife Service canals north of this reser- 4 marker in the clay of the Sehoo; moreover, because it voir; usunally large thinolite crystals occur at the latter IF came from a single eruption, it represents a single time two places. 1 11 interval wherever it is found. About 6 to 7 feet of .'...... A Loose crystals and crystal clusters of thinolite, rest- clay of the Sehoo underlies the ash near the south mar- ing on eroded clay of the lower smember of the Sehoo, Ie. gin of Carson Sink, but only 0 to 2 feet near the south occur locally in antarea extending iibout 7 miles south. -Z1, edge of the main basin. Mono Craters, Calif., is the ward froni Ciurson Siik and at least 2 miles westward 69-as8 Go-64-45

f

k I QUATESNARY RTRATrOTRAPH 61 LAKE LABONTAN: GEOLOOY, CARBON DESERT, NEV. N S 3 1* I I11

EoianCw sand

WO 3.5 MILES FEET01_

I -j

21-

O SO 100 FEET Deep-take clay VERTICALSCALE IS APPR0OXIMATE Si- -7.Daramtocnseatti. b.ho,et - -oreat thi-oft. at Wildest acne, -th ef the Whk. Th...os ..oet.Iss. .... Ftaos1s .. . 7717 TINW%SaC -se 4. T. SB Nt. R. 29 K. itolId tof. of I...... hc- of I.koo fo-Hto thitty vto hsWIde ens."t Eettastr..tss 'Brown basaltic sand Qest9.Clute. of tbl-lit. a, t Itlthotdthe 1 tb bW 3o.5,00 0d 5.573 feet tIItude. Tbhioitl tJ btest 1i OtshOt toad a-d iY of I.-~c osd dodelltle .eatn of tbe Sahoo (Qs,. Qm sod1Q,,, at thi. ttl1ty. Roa..tt.. to tM.5pp. ed ..1. ft. toft _b-.de" of dt.Otle .. thee,deotOptd dotS. -I.e . of toe..1ddl. Skboo15k.. Deep-lake clay 5 and 41/2 miles eastward from Timber LJake Here the gravel resembles the regressive gravel of the lower I. White volcanic ash upperpart of the clay of the Sehoo has been deflated member'in lithology and thickness; cobble to fine peb- tL Deep-ake cl and the thinolite is a lag residue from the thinolite ble gravel, generally I to several fest, rarely 5 feet or unit. more, thick. It is more prominent in mountain re- - own basaltic and ostracod sand mICN011,111555Mm entrants and intermountain saddles such as those east ? Deep-take clay ) and west of Rainbow Mloutitnin, whem it occurs in wide. The dendritic member of tile Sehoo formation con- ly separated terraces , bars, and spits. Transgressive sists of lacustrine sediments that record the middle and regressive phases can be distinguished locally by shore of this Sehoo lake cycle and extend to the high differences in lithology (table 4) and by separating feet It is commonly lake at an altitude of about 4,100 depositsof dendritictufa in plsceorbelowv about 4,100 feet, thick, and com- I to 8 feet, rarely as much as 25 feet, by separating clay, silt, and lacuastrine limestone. uneroded volume of the Deep-take clay prises nearly a quarter of the Sand of the dendritic member is distributed similarly silt, Sehoo. In the lowlands it is mainly clay, with to that of the lower member, but on highland shores it sand, and a little lacustrine limestone locally; in the is somewhat more tvidespread, being present in many minor amounts of tufa, highlands it is sand, gravel, and areas where the lower member is largely gravel. Few by lateral changes silt, and clay, and it is characterized of the main shorelines of the middle Sehoo lake are at a few feet Den. from gravel to sand or even silt within the same levels as those of the early Sehoo lake, so bars _ . and widespread of dritic tufa is the most distinctive And spits of gravel of the lower member commonly are and hence the name several varieties present (tables), corered by sand of the dendritic member. This sand is Shoreline of the middle I of the member. The highest widespread on the delta of the Careon River west of Sehoo lake, the dendritic terrace of Russell (1885, p. Shallow-take sand Fallon, where it locally attains 20 feet in thickness; 101-102), is marked neither by distinctive deposits nor aWRyfrom this delta it rarely is more than 5 feet thick. by prominent shore features and is only locally dis- I tinguishable. The type locality of this member is the Generally this sand resembles that of the lower member I" site of section 32 (table 10), east of Rainbow Mountain, except that it lacks the yellowish cut; locally in thick where the member consists of 31h feet of gravel that deposits in valleys, however, it is pale yellosv tan to pale makes up a bar which marks the dendritic terrace. orange brown and somewhat darker than the sand of Gravel of the dendritic member is much scantier and the lower member. flo-C s. s 2 w 5 ta ttt rt o~ se se~ t ss of t1e, of to. -t - bue r of Set - f oesstit . 5% H.i . spacO -ta so th -at 11. of C. - * generally finer than that of the lower member, and the Clay of the dendritic member typically is less silty, SI05. ohootagtat e...I rI tc of .Itkati .atd .. 4 55..ttso . ash heta s d P ftat-t SS Fi o., . -t oo oo tt to et to s t s . ed associated shorelines are less prominent (pi. 9). The more limy, and more saline than that of the lower mem- 1s tabl* 15. I I I

QUATERNARY ItTSATIORAPET 63 LAKE LAHONTAN: (JEOLOUY,CAR5ON~ DESERT, N5EV. R. 29 E., contain as much as 10 feet of sand of this mem- the regression of the middle Sehoo lake, and very weak it is about 10 miles wide north to. ber. The ciay is in places bentonitic, and also charac- adjacent quadrangles; ber (fig. 36). ones from the late Sehoo lake. south. This delta, called the west delta, is graded to teristically somewhat brighter greenish gray; locally Outside the river deltas, sand of the upper member thehighestshorelineofthelateSehoolake. Itsitrface SaoR=Xtzs or TRZ EAXLY 3ZOOLAJE some beds are green and bluish green. Lamination and is fairly widespread near the base of the hillshores, be- lies a few feet above the modern flood plain and heads bedding generally are more distinct than in the lower tween altitudes of 4,000 and 3,915 feet. It is the only ehorelines-The most prominent shore- at the mouth of the inner valley of the river at an alti- Transgressive member, and in places the beds or laminae show appre- shore deposit of this member in most places, but def- age are overlain by transgressive-phase tude of about 4,020 feet, in mec 30, T. 19 N., R. 28 E. lines of Sehoo ciable color contrast. Commonly small disseminated inite bars or other shore features are rare; generally gravel of the lower member of the Sehoo, and hence date The sand on this delta is commonly 5 to 10 feet and calcium carbonate nodules and oolites continue from the sand is merely a gently sloping sheet several inches of the early Sehoo hake. They 16 feet thick; it generally thickens from the transgression the thinolite unit a few feet upward into the dendritic locally as much as to a few feet thick and a few tens of feet to locally more are only slightly less strongly developed than those of and grades coarser westward; the uppermost deposits member. Ostracods are common throughout, particu- than I mile wide. The main deposits are on the flat be- Eetza age. They attain their fullest development on and those adjacent to distributary channels of the In- larly in the upper part. Close to highland shores bear- tween Stillwater Slough and the Lahontan Mountains that front upon the main Carson Desert formation are generally the coarsest. West highland shores ing thick dendritic tufa, the clay and silt are especially dian Lakes border of the western Bunejug Mountains of Rattlesnake Hill the sand is mostly very arkosic, and along the and that face north, northeast, northwest, west, orsouth- rich in calcium carbonate and commonly contain platy and Tirupah and Eightmile Flats. west. Here the main shorelines are markedly discon- pebbly, granule to medium, and includes some fine sand nodular bodies of limestone generally less than ½hinch In the upper member of the Sehoo the change from formable upont shore fentures of Eetza age and upon and silt and local stringers of fine gravel. Most beds thick and i to 12 inches in diameter. This member has between altitudes of 3,940 dunes of the WVyemahn formation; are moderately indistinct to clear, and generally par- sand to silt to clay takes place alluvial fans and been completely eroded by deflation from large areas and 3,925 feet except on the Indian Lakes delta, where not only by large constructional ter- allel, though locally inclined. The sand grains are gen- they are marked in the basin interior. sand extends down to about 3,910 feet. On the deltas races, bars, and spits, but also by local, moderate ter- erally subangular; the pebbles, subrouinded. Fragments I the silty transitional zone commonly is I mile wide or caves cut in bedrock. On the other of gray to nearly black lithoid tufa (late lithoid tufa races, cliffs, and by interfinger- early Sehoo age are at best poorly of this member, table 5) mostly less than half an inch more, 2 to 5 feet thick, and characterized hand, shorelines of upper member of the Sehoo formation is the less and The across, commonly are abundant in the upper several ing sand, silt, and clay; elsewhere it is generally developed on shores exposed only to the southeast of the late Sehoo lake cycle. It extends up to I foot thick. deposits feet of the sand. Near the base are local partings of than half a mile wide and rarely more than east, in contrast to shorelines of Eetza age. the highest shoreline of the late Sehoo Inke at an altitude basaltic sand, which mav have come from eruptions at Below 8,920 feet this member is mostly a thin layer of Highest shorelinxe-A strongly developed shoreline of about 3,990 feet, but this shoreline is weakly marked large areas 9odn Lakes (p. 72). Eastward from Rattlesnake Hill clay, only loca!ly I foot or more thick (over at an altitude of about 4,370 feet marks the highest level and only locally distinguishable. This member gener- the sand grades rapidly finer and is interbedded with it has been completely deflated); the clay is thickest, reached by the early Seloo lake. This shoreline is only as much as 16 feet thick. I ally is 1 to 5 feet and rarely increasing amounts of silt. On the bare flat just. south- locally as much as 4 feet, in the Stillwater Slough-Car- about 10 feet below the Lahontan bench (p. 30, 64, The type locality is an exposure of sand in the scarp of a west of the Sagouspe fault zone it typically consists of son Lake and Indian Lakes areas. This clay unit com- 65). Commonly the two shorelines are difficult deflation basin next to the former Fallon-Lovelock cut- is disconformable upon clay of the dendritic superimposed, the several feet of thinly interlaminated fine sand and silt. monly to separate because they are almost off, 3.D miles north of the south edge of the Soda Lake above an altitude of 3,920 feet, and locally as and the gravels of The other delta of the upper member, called the member Lahontan bench is poorly developed, quadrangle, the site of section 8 (table 10). low as about 3,900 feet (p. 62). The two clays are the two shorelines are similar. Four criteria useful for Indian Lakes delta, is in the western part of the Indian Gravel of the upper member is restricted to small separated locally by colluNium of the upper member differentiation are: Lakes area, east of the present course of the Carson 'r' patches close to the mountains along the highest shore- of the Indian Lakes formation, the Harmon School soil, 1. Eolian sand and alluvium of the Wyemaha forma- This delta is smaller than the western one- lines of the late Sehoo lake. The gravel is thinner, finer River. andearly lithoid tufa of the oplermemberof theSehoo. tion locally separate the Eetza and Sehoo formations about 5% miles long by 41'2 miles wide-has an even textured (fine-pebble gravel to pebbly saud), and poorer Silt of the upper member generally is light to medium 2. Beaches underlain by the Sehoo formation bear only somewhat finer sediment, and is some- sorted tham older gravels of the Sehoo (table 4), but it lower gradient, II brown or brown-gray. Clay is medium- to dark-drab the Toyeh soil (p. 78), whereas those above the high- conspicuous distributary is more abundant and generally coarser than the lake what younger. It has two brown-gray, greenish gray, or olive-drab gray, some- est early Sehloo shoreline and underlain by the Eetza gravels of the Fallon formation. channelsof alluvial sand of the IndianLakes formation. what darker than clay of the dendritic and lower mem- formation bear the Churchill soil. Sand is much more widespread than either gravel or They trend toward the gap through the scarp of the bers, to locally nearly black, especially at the base; small 3. Shore features of Eetza age are slightly more eroded clay in the upper member. Although thin compared Sagouspe fault zone and probably headed at the bottom 4-' calcium carbonate nodules occur locally. Sections 22a, than those of Sehoo age below. with older shore sediments, it is considerably thicker of the trench that was cut by the Carson River through 23, 28, and 35 illustrate this unit (table 10). 4. Embankments of gravel of the Ectza formation were .y and more extensive than any of the lake sands of the the scarp, at an altitude of about 3,t27 feet. These Two principal horizons of tufa are present in the up- wavecut at the highest shore of the early Sehoo lake, Fallon. It is widely exlposed on two former deltas of distributary channels cannot actually be proved to head I i per member-one at the base of the member, and the and the resulting scarps are fresher than the Eetia the Carson River within the main hasin and also in here, as the Fallon formation covers the parts of the other in its upper part. Each is distinctive (table 8) shore features above. selvages at the edges of the lowlands This sand is channels immediately below the gap, but there is no and hence a good stratigraphic marker. ';r. Regressive Ahorelines.-Shorelines associated with re- commonly severely eroded by deflation, part icularly on suggestion that either the channels or the delta sand _3;- sHORISIFRATURctn OF fi00 AOJ0 gressive-ptase gravel of the lower member of the Sehoo, the deltas. Deflation basins 10 to 40 feet or more deep continue west of the scarp; hence this delta probably t..' that is, dating from the regression of the early Sehoo have been scooped omitin areas hetween the distributary postdates the searsp and formed while the late Sehoo lake The age relations of shore features of Sehoo age are the latter have tended to remain rels- lake, are less developed than those formed during the channels, whereas receded from an altitude of 3,927 to 3,917 fe1t Fur- best demonstrated by the stratigraphy of the Sehoo tively uneroded, prolhnbly because the coarser sediment transgression. None have rock-cut features or asso- thernmore, the stratigrnaphic relations of eMrIXlithoid IT formation associated with them. Plate 9 shows the al- resisted deflation. Below 3.950 feet, the high shoreline ciated boulder gravel. They are rare and very weak tufn and sand of the upper member to faults in the west- titudes of the main shorelines formed by the three Sehoo of the first Fallon lake (table 7), this sand commonly 3 from the for at least 150 feet vertien lly below t lie 4,205-foot shore- ern part of the fault zone (p. 9 ) show that the faulting 4, lakes. The most prominent shorelines date is thinly veneered with lake sand of the Fallon. transgression of the early Sehoo lake, less prominent line (pl. 9); this zone shows as a broad band on the followed deposition of the early lithoid tufa and pre- One of the deltason which thisanud is widesprend lies ones from the regression of this lake and the transgres- old Inke shores where the blanket of cellular tufa, if ceded deposition of Inke sand on the delta. Two small 011 mostly in the southeastern part of the Soda Lake qund- sion of the middle Sehoo lake, rather weak ones from present, is unbroken by later wave wcarping and where rangle, though small erosional remunanits extend into the grabens in this fault zone in the NWiV/4 sec. 3, T. 19 N., f.--1 .fJ .1 1S

LAKZ LARONtTAW GEOLOGY, CARSON DESERT, NEV'. QUATERNARY antAUT5IuATH 65

Smoasiru or Trzz MIDDLZZ50 LA=;DZ ne overlying lake sand and gravel of the regressive phase mined by a line of level run by G. 1 Stanley in 1948 -t an altitude of about 4,355 feet. The gravel was partly ascRez. of the lower member of the Sehoo is very local and thin. from the Nevada Highway Department benriclmark cemented by the highestdepositsof lithoid tufa of Eetza Below the highest shoreline of the middle Sehoo lake at Russell Pass. age. Soon after, when the lake had risen about 15 feet Of the four distinct shorelines (p1 9) associated vith (about 4,190 feet), the regressive shorelines of the early 2. The crest line of spit 0 is irregular; it is 2 to 3 higher, spit C was built all the way across the embay- tranagressive-phase gravel of the dendritic member of Sehoo lake commonly are obscured by the reworking feet higher in the central part than at either the distal ment by long-shore drift from both the northwest and the Sehoo, only the 4,045-foot shoreline is well marked. done by the later lake. (south) or the shoreward (northwest) end. This con- the southeast When this lake cycle reached its maxi- A weak shoreline at about 4,190 feet seems to mark the highest level reached by the middle Sehoo lake. OOMPARAIV KIMssoUsOr sIOeT KETZAA" EARLY51OO dition is anomalous, an the crest line of a monogenetic mum (the maximum for all Lake Lahontan time) at gaoalso Aa AT RUSSELL My spit normally becomes lower, not higher, offshore; it 4,378 feet, spit A was built During recession of this This shoreline is the upper limit of dendritic tufa depo- sition, and probably is the same as Russell's dendritic This writer's conclusions on the comparative heights suggests that the higher part may be a remnant of an lake, minor further deposition and modification of spit older spit. The detailed mapping bears out this aug. C and lower shore features may have occurred. The terrace (Russell, 1885, p. 101-102; Antevs, 1945, p 30). of the Eetza and early Sehoo lake maximums di ffer from It is marked neither by distinctive deposits nor by those reached by Russell (1885), and also from those gestion. The gravel of the higher central part bears soil maximum of the second Eetza lake was well below these correlated with the Churchill soil, whereas the gravel at spits- prominent morphologic features and is only locally dis- reached by Jones (1925,1933) and, in part, by Antevs tinguishable. In places, for example, the dendritic tufa (1925a, 1945,1948,1952). Only Russell has published the ends bears soil correlated with the Toyeh soil. The 2. Wyemshs and Churchill time: Subaerial erosion higher gravel also is more heavily coated with, desert of these shore features during 1yermaha time is not resembles "coralline" tufa, and the gravel resembles concrete field evidence, and only his interpretations will regressive gravel, of the lower member of the Sehoo. be considered here. Russell concluded that at the maxi- varnish than the lower. Geomorphic relations indicate evident. In Churchill time, the Churchill soil formed that both gaps were cut by subaerial, not lacustrine, on them. The high shoreline is locally clearly marked by gravel mum of the first deep-lake period (Eetza time of this bars in intermountain erosion. Erosion of the north gap was shallow, for test 3. Sehoo time: Spit C was subaerially eroded in very saddles such as those east and report), Lake Lohontan rose only to the lithoid terrace west of Rainbow Mountain and between the White level (about 4,350 to 4,370 feet in the map area), and pits show that the Sehoo formation here is commonly early Sehoo time, after the Churchill soil formed and that at the maximum of the second deep-lake period only 1 or 2 feet thick, and is over Eetza formation which before the early Sehoo lake had risen to the level of the Throne and Desert Mountains, but it is obscure on the (Sehoo time of this report), it rose to the Lahontan bears eroded Churchill soil. spit. Probably the large wash that heads back of the mountainous shores except for tiny bars of gravel of beach (about 4,380 feet). He deduced this history by Additional evidence that the spit became breached be- reentrant overflowed the spit, corrading several feet at the dendritic member in a few places. interpreting the order of formation of overlapping tween the two lake occupations is giren by the directions the northwest end, and more at the south end of the spit. About 14 moderately to strongly marked shorelines high-shore spits, bars, and terraces, particularly at an of longshore transport that can be inferred from the As the lake rose the earlier embankment was scarped are associated with the regressive-phnse gravel of this unusually instructive compound spit on the west side of composition of the two gravels. The Eetza formation at 4,3404,350 feet, and a coating of cellular tufa was member. They are conspicuous because they are the the pass between the White Throne and Desert Moun- iscobble gravel containing rhyolite, andesite, and basalt. deposited to a maximum altitude of 4,355 feet. The youngest shorelines on the highland shores and have not tains, now known as Russell Spit (Russell, 1885, p. 113- The rhyolite could have come only from outcrops to early Sehoo lake reached its maximum at 4,368 feet- been modified by later lake erosion. The terraces, bars, 114 and pl. 19; also see U.S. Geological Survey map of the northwest, and some of the andesite could have come 3 feet below the Fetza level of spit C and 10 feet below and spits of all the middle Sehoo shorelines, both the Weber Reservoir 15-minute quadrangle). only from the southeast. Yet the top (Eetza) level of the maximum lake level in Eetza time. At this level, transgressive and regressive, consist of fine to medium Russell reasoned that at Russell Spit the overlapping the spit now ends 300 feet short of the south shore, and gravel derived by longshore drift from the northwest pebble gravel; rock-cut features are absent. relations of the different lake-gravel embankments in- is separated from this shore by the 10-foot-deep gap at healed the breach at the northwest end of the spit, and snozzL5im or TEE LATE55*00 LAE dicate that the highest ones are the youngest, and par- the south end of the spit. The Sehoo formation, on partly healed the breach at tihe south end by developing ticularly, that embankment A was built over and hence the other hand, is medium gravel consisting of rhyolite a series of small stepped spits; a shore terrace was cut Shorelines of late Sehoo age are weakly developed is younger than embankment C (fig. 28). He believed and a little andesite like that in dikes just northwest of into the side of spit A. As the early Sehoo lake receded, and few-there are two high shorelines, 10 feet apart, that lithoid tufa was deposited only during the first the spit; the composition and morphology of this part it reworked earlier gravel to build most of the embank- and a regressive one. The high pair is marked locally deep-lake period, and concluded that embankment C of the spit indirate derivation solely from the north- ments seen today below spit C. This ended the lake by mall bars and terraces consisting generally of postdates the one just below it because this tufa encrusta west. history at this locality, for later lakes did not rise nearly pebbly sand and sand but of fine gravel in a few places the gravel on the lower embankment. In his summary, 8. The tufa that encrusts the gravel on the first ter- this high. - close to mountains. The highest shoreline generally is he (1885, p. 170-171) noted, however, that the geomor- race below spit C (at about 4,355 feet) is of two ages: at an altitude of 3,990±10 feet (for example, the west- LAXX LZVELS VUlRIe DEyCrToIN or Tnr TnRigoLTr Vx51 phic evidence from this and other localities was incon- The earlier-lithoid tufa of the Eetza formation-is ern Lahontan and northern Bunejug Mlountains, south- clusive, and that the "chemical evidence" afforded by exposed locally in the wave-cut scarp below the front The 4,040-foot shoreline is the lowest definite shore- eastern Banss Flat, and northern piedmont of Desert the sequence of deposition of the tufsa was more sig- edge of this terrace; locally veneering this colt surface line formed during the regression of the early Sehoo Mountains; pL 2). At the northeast edge of the nificant. and overlapping gmivel of the lower member of the lake. LAke Lahontan fell at least 50 feet below this Lahontan Mountains, east and northeast of Reed Butte, The writer's observations and deductions on the Sehoo formation is cellular tufa, also of the lower memn- level during deposition of the thinolite member (p1. 10), and in the saddle between Rainbow Mountain and the stratigraphic and geomorphic relations at Russell Spit bar of the Sehoo, that extends to about the same alti- but this minimum lake level is not marked by a shore- Stillwater Range, however, the shoreline is lower- are as follows (fig. 29) tude as the, earlier tufa. Geomorphic superposition line or shore gravel of thesame age as timethinolite unit. 3,980 to 3,975 feet-due probably to local downwarp- 1. The uppermost spits (A and B, fig. 28) are made shows that part of spit C (the part built in early Sehoo Strongly developed terraces at altitudes of 3,990-4,010 ing. On tte wrest river delta and east of the Dead up solely of gravel of the Eetza formation and hence time) postdates the cellular tufa deposition, but it does feet in the Carson Desert, which are possibly correlative Camel Mountains it has been almost completely deflated were not built during the second deep-lake period not prove that the whole of this spit was built during with thethinolite terraceat this altitude in the Pyramid- or covered by eolian sand. (Schoo time) as Russell believed. This gravel bears a separate later lake cycle, as Russell inferred.. area (Russell, 1885, p. 237; Jones, J. The delta at Indian Lakes (p. 62, 83) marks a regres- typical Churchill soil and neither the gravel nor the soil The inferred lake history at Russell Spit is as follows: C., 1925, p. 43; Antevs, 1945, p. 30), Istesmainly from sire slorelimne at an altitude of 3,917-3,927 feet. The has been reworked by later lake action. At spit A the 1. Eetza time: During the transgression of the first Eetza tirlle (p. 31)-long before time mai thlinolite sinsll size and simple et rueture of this dlelta suggest that Lahontan beach is at an altitude of 4,378 feet, as deter. Eetza lake a gravel spit. was constructed at this site at deposition in tlmeCarson Desert. it fonned during a comparatively brief stillstand. MM

.I LAXKE LA}IONTAN: GEOLOGY, CAR80N DESERT, NETAV. ?1I qTUATERNARY 8SRASIORAt'Y 67 EXPLANATION

m(14 FaiHon letmedin Of. dUa, ad pro .,d< x,r 1I r Obe of Toyeh aol foeo~tho UNCONrofti.ry K9 Schoo fono~tioo

oald a tot',nbho r

Oso,.l betan d afl theL et__od z (Time of Chnn-hill -oil foeintio) UNCONttORMlry ElI 0 Eet formation Lakerowl.r IBoldwererlI a ff

(Time of Cocoon tnl formtion) Et] Niot. fonootion OD.. afluoial grROwl. Cont. roflac.,, (trop nal I faoa)*

;I UNCONrFOR*TVr

BRwjog foennsitio 1.ha-at.n4d and raif.flwo . ,a cW M Ju UNCr Nroet rv 4 I'

Thlokee fonootin 0 500 10(O FEET T .ta i .nlwe ltO, o.o dt. fa o ' abatera d -ondioaa o 500 1000 FEET topta 25 - t eb e a of Rt. - Iti Spit oa4 11etolty. P art of plate S E to ka. a-t. (£8 85) mono_grap or L k. bot.ohc a. slappe"dby WY.D. Joboao. oaeeoa a1oJot ... . .elaa ...a beloW a..o doto4,, v.bcb 1a t tbe btgbeat boroIIoof LEt Labootaa (Labootoebobh) oe Iba ,e obr eppnoxiaow.It ka npit A. 0 X4359 Aftitule. In feet obo-e t enel n r -tno~a~dbC M 5. W - g a lI ,,

Ftana 2 .-O o I~gc mp of R .aaell spit o at ntd aIty fa. . eo f a g, 26 U -,------

68 LAKE LASONTAN: GEOLOGY, CARBON DESERT, NEV. QUATERNARY MtATIGRAPIS 69

at altitudes above the highest shore of the L&II3 ASS xinirA iAE ror=uSSATION formation here principally alluvial gravel, which forms tiny allu- AUMUM OF MISDULazuoO A"S INDUSl above the upper tongue of GENERALrZCATUES late Sehoo Lake (and hence vial fans 1 foot to perhaps 6 feet thick on piedmont Alluvium of middle Sehoo and Indian Lakes age is The Indian Lakes formation (Mforrison, 1901a) con- the Indian Lakes formation). Alluvium of late Sehoo slopes, over gravel of the lower member of the Sehoo. on the Carson River delta in the Soda LIke quadrangle, sistsof alluvium, some colluvium, eolian tend, very and Indian Lakes age, mapped in all four quadiangles, The alluvial gravel is locally overlain by 1 foot to sev- where it consists of sandy gravel and sand in an old shallow lake silt and clay, and locally volcanic sand of ranges from far above the high shore of the late Sehoo eral feet of dendritic tufs and(or) gravel of the den- distributary channel that extends from ec 14, T. 19 feet below this shore, and it both intertongues the same age as the Sehoo format ion and intertonguing Lake to 80 dritic member of the Sehoo. The middle Sehoo lake N., R. 27 E, toe. 25, T. 20 N, R 27 E. The dixtribu. member of the Sehoo for. of withit. Itoverliesthel'y~emalaformtionteitonlght with and overlies the uppercomplex of early( 1), middle, eroded these fans relatively little and the pattern tery channel overlies the dendritic member of the Sehoo wit it Itverietheyemhaormtin, ithslihtmation. A volcanic-sand still is evident The chief or no disconformity, is younger than the Churchill soil, an aSehoanIndian Lapes ageis midaspr their distributary channels (hence is younger than the middle tongue of the Indian and is overlain by the Turupah formation. The Indian Andfte In Sehoo and Indian Lakes age is mapped as part occurrences and approximate lowest altitudes reached Lakes formation) and seems to have formed when the Lakes formation is sparsely distributed in both high- of the Indian Lakes formation in the Soda Lake ares by the alluvium are: (a) sees. 10 and 14, T. 18 N, R. 30 middle Sehoo lake stood at an altitude of about 4,010 4,020 feet; lands and lowlands, and is commonly only several Auvo AND55..... ARove TaI L"MO5T7A REACH E., on the north side of Sehoo Mountain, feet during its recession. inches to several feet thick, having a maximum thick- (b) SWy4 see. 28 and NVA sm 33, T. 17 N, R. 30 E, Upper tongue-The upper tongue consists of local ness of perhaps 15 feet in alluvial channels. Alluvium and lluvium of thi formation are ex- southwestern Piedmont of the Bunejug Mountains, collurium and marsh silt or very shallow lake silt and At its type locality, the western part of the Indian posed in the mountains above the Lahontan beach in 4,070 feet; (c) SW%/4 see. 33, T. 17 N., R. 30 E., 4,040 ciny intercalated between the dendritic and upper mem- Lakes area SEI4, T 20 K., R. 29 E. and SW¾Y T. 20 N tiny patches a few inches to several feet thick-hence feet; (d) see. 26 (unsur-eyed), T. 17 N., R. 30 E., east bers of the Sehoo fornintion. It can be distinguished R. 30 E., alluvial sand of this formation tlmkes up two unmappable-and cannot be differentiated as to mem- side of the Bunejug Mountains, 4,120 feet; (e) NiA sec. only where it is overlain by the upper member of the prominent distributary channels on a delta of late ber or age subdivisions within the formation. The 16 (unsurveyed), T. 10 N., R. 31 E., east side of the Sehoo, that is, below 3,900010 feet; it iseverywhere too Sehoo age alluvium is bouldery gravel that mantles local terraces Cocoon Mountains, 4,020 feet; (f) XENrW¾/4 sec. 9, thin to be mapped, but is differentiated in stratigraphic The colluvium is TONGUESAND AGE UNITS a few feet above present wash beds. T. 16 N, R. 29 E., north side of the White Throne sections. 16N., mostly block strennms on steep slopes (probably devel- Mountains, 4,015 feet; (g) N'y 4 SWI/4 sec. 3, T. The type locality is the site of section 17 (table 10), The Indian Lakes formation alw ays is subdivided on side of the White Throne Mountains, the geologic maps unlike the Sehoo formation) and in oped by washing out of lines from solifluction mantle of R. 29 E, north two-thirds of a mile north of Harmon School 4,010 feet. about the stratige phic sections It is subdivided into tongues Eetza age) and slope wash near the base of slopes and where an irrigation canal exposes a 3-foot (slope wash) of this tongue can be seen at (not in use), intercalated with members of the in sNales. Colluvium member that locally bears the where it is actually Hidden Cave, the type locality, and locally in some of bed of collurium of this Sehoo formation or the Sehoo and the Churchill soil; Harmion School soil (p. 75) and is intercalated be- lower tongue consists of alluvial sand and gravel the gravel pits in western WYyeinaha Valley (fig. 15C). in other places it is subdivided into age units as a result The tween clay of the dendritic member and silt and sand with the Sehoo formation, between the Wyemaha formation and the lower mem- Dieconformity coet'l Sith the middle tongue.-The of correlation of the upper member of the Sehoo. tongues-lower, middle, and upper-are dif- ber of the Sehoo formation; it is younger than the lower and dendritic members of the Sehoo formation Three to that at the type locality occurs ferentiated in stratigraphic sections, but only the mid Churchill soil. It is differentiated only below an alti- are separated locally between altitudes of about 4,190 Colluvium similar discontinuously for several miles west of the Sagouspe dle tongue in the Carson Lake quadrangle is used as a tude of 4,370 feet, the highest altitude reached by the and 3,990 feet by an incipient soil (p. 75) and (or) 3,925 feet altitude, and is as map unit as the others are too thin. The lower tongue, lower Sehoo. Occurrences are rare and too thin to be by a disconformity that records subaerial exposure dur- fault zone, above that of angular to sub- of early Sehoo and Indian Lakes age, is between the mapped. The type locality is the site of section 34 ing the time interval of the middle tongue of the Indian much as 8 feet thick. It consists Churchill soil and the lower member of the Sehoo for. (table 10) in Churchill Valley, where this member is Lakes formation. In most places, however, these sub- angular fragments of clay from the Sehoo formation, mation; the middle tongue, of early and middle Sehoo alluvial sand between the Churchill soil and the lower aerial features were obliterated by wave erosion of the locally mixed with sand, which is indistinctly bedded it and Indisa Lakes age, is between the lower and den- member of the Sehoo. middle Sehoo lake. The disconformity has been noted and shows little evidence of transport; in places feet at the extreme west edge of dritic members of the Sehoo; the upper tongue, of mid- as low as about 3,990 bears the Harmon School soil. Commonly the lower dle and late Sehoo and Indian Lakes age, is between MIt 5050W Wyemaha Valley (p1. 8 and sections 41 and 42, table contact of the colluvium is sharp but undulating, and by an incipient soil. the dendritic and upper members of the Sehoo. The The middle tongue consists of alluvial gravel, col- 10), where it locally is underlain the underlying lIke clay is broken and closely jointed it is indicated by gullies cut into gravel of time intervals of the middle and upper tongues are 1o- luvium, and eolian sand. It is differentiated only below In places for about I foot below the contact. the lower member and filled by gravel of the dendritic cally represented, at least in part, by very weakly de- the high shore of the middle Sehoo Lake, at an altitude Below 3,925 feet the member is rare, but it has been feet, and occurs locally down to about member of thie Sehoo formation; the lowest such occur- veloped soils and by disconformities within the Sehoo of about 4,190 rence in the Carson Lake quadrangle is at an altitude identified at 3,908 feet in a borehole along the Diagonal not only time represented by formation that record subaerial exposure. These two 3,990 feet. It. represents of about 4,020 feet in the long spit extending southward Drain in the SW i/4 sec. 17, T. 18 N., I. 30 E, where it and the coeval disconformities and soils attest the thinolite unit of the Sehoo (here called thinolite of 1i feet of carbonsceous silt and sand tongues .1' from the southwestern Bunejug Mountains (fig. 25). consists to recession of Lake Lahontan to altitudes of at least recession time), but also parts of early Sehoo Lake time A filled valley on the Carson River delta probably also between clay of the upper and dendritic members of the as low as 3,990 (middle tongue) and 3,900 (upper and middle Sehoo Lake time (pi 12). The type locality indicates thisdisconformity. The road from U.S. High- Sehoo; it also has been found at about 3,900 feet in the tongue) feet. The recession during the time repre- is the site of section 39 (table 10), in Hidden Cave, in way 50 to Northam School, on the line between seae western Indian Lakes area, where it consists of %to 2 sented by the middle tongue is here called the thinolite Eetza Mountain. The member is bed 10 in this section, '4 19 and 20, T. 19N., R.27 E.,crosses a deep channel cut feet of black carbonaceous silty clay, which is probebly recession (after the thinolite unit of the Sehoo forms- which consists of colluviuns (slope wash) 1.7 feet thick 4 into elayey sediments of the lover member of the a marsh or swamp deposit (section 5, table 10). tion); and the recession during the time of the upper between clay and silt of the lower and dendritic mem- Sehoo and filled by silt and sand probably of the den- Disceonforaitywocra wilth the vpper tongue.-A dis- tongue is called the late Sehoo recession. bers of the Sehoo formation, at an altitude of about dritic member of the Sehoo. The channel probably was confomrity within the Sehoo formation that rcords Alluvium of middle Sehoo and Indian Lakes Age, 4,095 feet. cut during the tlinolite lake recession. The fill extends subaerial erosion conmmoly occurs at the same strati- mapped only in the Fallon and quad- The middle tongue has been recognized and differen- below an altitude of 4,040 feet so Lake Lahontan fell graphic position and altitude range as the upper rangles, overlies the dendritic member of the Sehoo tiated chiefly in the Carson Lake quadrangle. It is still lower during this recession. of the Indian Lakes formation, where that A tongue - __ . - . .. M

O'i QUATERNARY STRATIORAPM 71 70 LAKE LAIIONTAN: GEOLOGY, CAR8ON DESERT, NEV. J .:'J tongue is missing. It is commonly marked by desicca- resembles sand of the upper member of the Sehoo on 11 of the lower limit of the late Sehoo recession is the 6%t miles downstream to about 3,903 feet, I mile east tion cracks and sand dikes in the underlying clay of this delta; it can be distinguished with certainty vhere I'-J lowest altitude reached by early lithoid tufa of the of the terminus of the west channel. The highest es- the Sehoo formation, and in places it is underlain (fig. it is overlain by definite lake sediment, particlarly upper member of the Sel&oo (table 5), which probably posures of both channels are only about half a mile 30A) by the Harmon School soil (p.75). early lithoid tufa of the upper member of the Sehoo. formed in less than 5 feet of water. This tufa reaches *part, and there the channels are converging toward This disconformity is widely exposed in deflation Below about 3,910 feet this disconformity has not .S`iel altitudes as low as 3,885 feet as a local lag deposit on the gap cut by the river through the Sagouspe Scarp. hasiwis on the west delta of the late Sehoo lake, east- been identified with certainty, but additional evidence eroded clay of the lower and middle members of the These channels are presumably distributaries from the ward to the Sagouspe fault zone. Here it commonly Sehoo in the eastern part of the Stiliwater quadrangle. same channel of the Carson River. The alluvium of both channels is fine-pebbly coarse and medium sand has a relief of several feet. It is readily confused with '2 Its original lowest altitude was 3,890-3,895 feet when the larger unconformity of Turupsh age (p. 75,77), be- allowance is made for subsequent erosion and deforma- and scattered fragments of early lithoid tufa of the cause eolian sand of the Tumrnpah formation commonly tion, so probably Lake Lahontan fell at least as low upper member of the Sehoo; it bears the Toyeh soil, as 3,900 feet during this recession. which demonstrates its pre-Fallon age. Colluvium considered to be of late Sehoo and Indian ALLUVWO, VDMlUSM. AND 50llAW S*AD or tAT 50o AND Lakes age occurs in Hidden Cave (bed 7, in section 39, INDIA LAXV, AOC table 10). It is a lenticular bed of coarse gravelly slope . Most of the Indian Lakes formation occurs at alti- wash as much as I foot thick, which extends only a few tudes above the high shore of the late Sehoo lake, com- feet into the cave. It overlies lake sand and gravel of monly resting on the dendritic member of the Sehoo. the dendritic member of the Sehoo and is overlain by These deposits-mainly alluvium, and minor amounts loess that is correlated with the Turupah formation. of collurium and eolian sand-are considered to be of Eolian salid of late Sehoo atid indias Lakes age late Sehoo and Indian Lakes age, and are not included locally intertotigues with the upper member of the in the upper tongue of the Indian Lakes, because, where Sehoo on the west delta of the late Sehoo lake (section they extend to or below the late Sehoo high shore, they 7, table 10). intertongue with or rest on the upper member of the VOs.CANIC-SAND COPIL=X OF BODA XAZZ Sehoo, and hence are younger than the upper tongue of the Indian Lakes formation. Soda and Little Soda Lakes occupy craters in an ellip- The alluvium of late Sehoo and Indian Lakes age tical cone, 100 feet high and l1h to 2, miles in diameter, was deposited by the Carson River and the highland of sandy pyroclastic debris; the bottom of Soda Lake washes The wash alluvium is torrentially bedded and is about 230 feet below the general surface of the desert poorly sorted, having a wide range in size grade and a outside the cone. The cone deposits, mapped as the vol- high percentage of angular nnd subangular fragments. canic-sand complex of Soda Lake, are mainly sand, silt, It ranges from gravel and boulders locilly several feet and a little gravel, derived from underlying Quater- in diameter in the moutitains, to sandy gravel and peb- nary sediments, and a small percentage of basaltic bly sand in distal pIarts of the fais. Where it can be Inpilli and bombs; no flows or dikes are present. The differentinted from alluvium of the Fallon formation, only good exposures are in the crater walls, especially it is generally more widespread and somewhat coarser. the bluffs bordering the northenst half of Soda Lake. The alluvium of the Carson River occurs in distribu- Three main stratigrnphic units, separated by angular tary channels on the two deltas of late Sehoo age (p. unconformities, were formerly exposed here (Russell, 62,63) and on terrace reninantsalong theeriverupstream 1885, p. 73-7r, pL. 17), but the 60-foot rise in lake level from the west delta. It is typical of relatively low- since development of the Newlands Irrigation Project gradient perennial-stream deposition-pebbly to fine has left exposed only the upper unit and n local selvage r-c-- *I .-A. Sad at oppa,.r ba ad sabaa 4odteo1Woato sand, fairly well sorted, nid generally evenly bedded. of the middle unit. tor- blj aaoaylia ,t, at th. laha. Tb, dioeloaf-lity Clpato nt . p, WCowa at IJ41a W Lab. t to. ta. .nd th tt S.nSo --- Even in the coarsest deposits few pebbles exceed I itch The lower unit, according to Russell, is thinly bedded, 1k oboo .011 it toenty S -aaa 4 haca:ti It. B ank of .. tita . -nI in diameter. perhaps Iacustrine, salid and silt tint contains abundant at SU- . SRaor. o. 2T. T. 15 N I . r. a.,Bi lli t- The alluvial sand on the Indiatt Lakes delta marks basaltic Ispilli; the unit is cemented, jointed, and much a. -o f Tard b .olt 1. ga-ily .. n Ca a biheb.bt. batr t isa aIddi Sob.o lota1tlwr ae.IT T. Is , R. I5M.1 two distributary chmnnels that nosy appear as conspieu. faulted. Itsformermaximumexplosedthiicknessappar- d b. typiyvkof TiSk moi.bt. ht, hish h.onf tib tt. so..l ently was between 10 alid 20 feet; an angular uncon- ltake C, 5.it ttR.0 as . btmb.. ort-t, of tb, bta. Sboo ous ridges rising several feet above the delta; their .5. taw % . 4 t a a T. IS Ni.. R. 1t 3. V. , taai coarser sediment Ias resisted subsequent deflation more formity having several feet of local erosional relief S.a t.: a. ..Ida tl t,h.." - : Uo.. t .ta. iCOat bot ot- t .- than the interchannel sediments. The west channel can separates it from the middle unit. .au b _ .. id, a-d to ta- hbo. -o . e,. t P.atto. P.ata t at t at . Ita tad T oYa" toit. T b, a- it toato d an U..i be traced for more titn 3 miles; normilly about 400 The middle unit, according to Russell, is about 50 feet Tnn .5 T nrs.u I at. ti. r .d 1. b.ti tA ,i t. mad at tIH Stat F aotto ta .. it t aalao= botto *h -a aa tb tIlbt- ei ,oad bood feet wide, it widens to 2,0(h0feet af its lower end, at thick and consists of well-bedded moderntely indurated at ib. tatp 0 tt~. o. ., .014 ta'l- t tba m..a to h abitat tha blath. an altitude of about 3,913 feet, where it intertongues basaltic Inpilli sand, interbedded with considerable Tbo lii. t Cot.. i.t .. ta -ot. t.i ., at -lbaar r .tt . do with the tippermemberof tiheSeloo. Theenst channel, marl, silt, and clay that contain the pelecypod Amu- ob.C ita . t, lb . f. an al a adt, .Iia i t . a.tiy to P . . ou te it ill hk o a . a n n t a I a a t o -t~. 1~.N VVt A ole. roughly parallel to the west, run be traced for about dOhent,and locally, a few feet belosr the top, a layer of S. T. 55iS.N_. 2*5B. QUATERNARY LAKE LAHOWNAN: GEOLOGY, CARBON DESERT, NEV. erRATwRAPErT 73 0s551s or eoo0 AND 1DW5N LAKES AUX Fossils of thinolits recession agc-Vertebrate bones Bufa; probably it is lacustrine throughout This unit is Toyeh soil where the eolian sand is absent. It is corre- having were obtained from the middle tongue of the Indian locally faulted and an angular unconformity lated with the upper member of the Sehoo. Fossils obtained from the Sehoo and Indian Lakes Lakes formation in pit NX at Hidden Cave (unit 10 several feet of local relief separates it from the upper At the periphery of the cone, relations of the volcanic formations include the following: in section g9, table 10). They were identified by anit. The only exposures of this unit still above water sand to the Sehoo formation are poorly exposed, but etod of cariySchol b agc-A horse jawbone fm Seth B. Benson, 3luseum of Vertebrate Zoology, Uni- Ire a discontinuous selvage, half a foot to 15 feet thick logs of many wells imsees. 5 to 9 and 18, T. 19 N.,R. 28 mnetapodial leg bone of a eamel wvereobtafned eet versity of California, Berkeley, and E. C. Furlong, %longthe southeast shore of Soda Lake (section 10, table E. (W. 0. Clark and C. H. Lee, written communication, gravel of the lower member of the Sehoo about 20 f Department of Vertebrate Paleontology, California It is tenta- 10); here the unit lacks both tufa and shells. 1916; Morrison, 1958a) suggest that at least the upper below the surface in a deep gravel pit, 7% miles south- Institute of Technology, as one individual earl of: aively correlated with the lower member of the Sehoo and middle units intertongue with and into the Sehoo. east of Salt Wells, sec. 26 (unsurveyed), T. 17 N, RIL 1 because the next overlying beds are correlated with the The boundary mapped is gradational; the Sehoo forma- E., operated by the Tedford Brothers of Fallon. The itaroreptaerfeesr (yielow-bvtried armaot) aendritic member of the Sehoo and the separating un- tion is sandier than normal for I mile or more beyond horse maxilla was determined by R. A. Stirton, Depart- Ieasons *P. (tmo"drat) conformity seems to represent a small time span. the boundary. On the west side of Soda Lake the tuff ment of Paleontology, University of California, Berke- Ups."ss (Jeekrabbtt) The upper unit, as much as 120 feet thick, makes up cone appears downfaulted; its boundary with the Sehoo ley, to be Equue, rp, undoubtedly a relatively recent Ietifasiea sa (detteetsuor pism? rabbis, *ad Urd set nearly all the exposed volcanic sand of Soda Lake. It is concealed by eolian sand and lies in front of a ridge form. The camel metapodial was determined by Jean contains 4 zones, but the lowermost 2 zones are exposed that extends southwestward from the tuft cone. This Hough, US. Geological Survey, to be Camsclps?. Each form is still living in the area. only locally in the bluffs on the southeast side of the lake ridge consists of relatively nonbasaltic Sehoo forma- Probably also of early Sehoo age are the bones of three Fossils of middle Sehoo age.-Fish bones in a slab (section 10, table 10). The lowermost zone rests on the tion-about 35 feet of fine sand and some interbedded extinct vertebrates from a gravel pit at Astor Pass, 4 of lacustrine limestone from the middle member of the middle unit with a marked angular unconformity, and silt, capped by 10 feet of sand containing much den- miles northwest of Pyramid Lake, identified by Mer- Selhoo in pit N6 at Hidden Cave (top of unit 9, in sec- consists of IA to 2 feet of soft lacuatrine silt overlain by dritic tufa both as heads in place and as waterwora riam (1917) asFelisatroxLeidya lion), Camelidnear tion 39, table 10), were determined by D. H. Dunkle, about 7 feet of lacustrine well-sorted fine-pebbly sand fragments. At least the upper part of the ridge sedi- Camelops, and Egu.t op., probably near E. paciflous, U.S. National Muluseum, as similnr to those described and grit composed mainly of basaltic lapilli and a few ments is correlated with the dendritic member of the or possibly E. occidentalie. The Astor Pass gravel pit above from clay of the lower member of the Sehoo. waterworn fragments of dendritic and lithoid tufa, Sehoo. The sediments cannot be correlated directly is above 4,200 feet and likely above the middle Sehoo Another collection from the same horizon was identi- which are typical of the denditric member of the Sehoo; with those exposed in the tuft cone because eolian sand lake; hence the gravel and tufa in the upper part of fied by Ira LaRivers, Department of Biology, Univer- hence, this zone is correlated with the denditric member. and slope wash conceal the transitional beds; they prob- the deposit that yielded the bones probably is in the sity of Nevada, ns containing the fish Sipheteles,prob- The second zone, as much as 10 feet thick but locally ably intergrade with the first and third zones of the lower member of the Sehoo. ably S. bicalor obesue, the Lahontan , and absent, is poorly sorted indistinctly bedded fine-pebbly upper unit in the tuffcone. Fish bones that weathered out from clay of the lower the ostracod Cyprinotu* sp., possibly C. denatus medium sand; it seems to be slope wash. The The eruptions recorded by the lower unit in the tuft member of the Sehoo I to 2 feet above the Sehoo-Wye- Sharpe. All these forms are still living and are not third zone, about 45 to 60 feet thick and probably laI cone are of uncertain, possibly early Sehoo, Wyemaha, maha contact, about 1 mile south of Carson Sink and diagnostic of age. eustrine throughout, consists of a few feet of silt at the or even Eetza, age. The middle unit may record erup- 3 miles northeast of Upsal Hogback (sec. 7, T. 21 N., Fossias of laie Schoo and Indias- Lake age.-The base, overlain by interbedded generally rather poorly tions beneath the early Sehoo Lake, but definite eri- B. 29 E.), were identified by D. H. Dunkle, U.S. Na. elope-wash gravel of late Sehoo and Indian Lakes age sorted sand, fine-pebbly sand, and some fine gravel; it is dence is lacking in the trivial exposures now available. tional Museum, as a "mixture of perhaps two suckers of the Indian Lakes formation in Hidden Cave (unit moderately to well bedded, locally ripple bedded, and A conspicuous sand zone, interbedded between clay of (family Catostomidae), carp (family Cyprinidne), and 7 in section 39, table 10) yielded many mamnmal and bird somewhat indurated. These beds contain several per- the Sehoo and locally more than 5 feet thick, that ex- possibly also bullhead (family Cottidae)." bones and a few seeds and mussel (Asnodoantaap) shells, cent to locally more than g0 percent basaltic lapilli, and tends 3 to 4 miles southeastward from the base of the Snails were collected from gravel, sand, and silt of which were probably carried to the site by Indians. less than I percent to several percent coarser fragments Soda Lake cone, seems to be in the lower member of the the lower member of the Seboo at 18 localities (table The mmnmal bones were identified by S. B. Benson (volcanic bombs and blocks) of basalt. These larger Sehoo and may represent sand blown out by eruptions 6 and p. 51-59), ranging in altitude from 4,090 to 4,S3 and staff, University of California, Berkeley, ns the fragments are mostly less than half an inch in diameter, cooval with the middle unit. feet. They were determined by Joseph P. E. Morrison, following (each species is still living in the area except although cobble- and even boulder-sized fragments (to The first three zones of the upper unit probably are U.S. Geological Survey, to be solely of one species, those starred, whicls have become extinct within the rarely throughout the 4 about 2 feet in diameter) occur of the same age as the dendritie member of the Sehoo; Parapholyrz nerdeensis Henderson, in all but one col. lastcentury): zone, as do some fragments of indurated silt and clay, the first and third probably were derived mostly from lection; the snails varied toward P. [reeadensia] - Mvsmott.e-tmouve-eared bet.I tndividual) waterworn fragments of dendritic and lithoid tufa, and, material blown out by contemporaneous small under- Meartshret.1I (loag-atladvedweasel. Itidiidnsal very rarely, pebbles of gneiss, rhyolite, and other non- water eruptions, though some parts may be merely re- ( illa F. C. Baker in three collections and toward P. basaltic rocks. As Russell pointed out, the lapilli are worked by lake waters and not directly derived from neradensts ealida DalI in two collections. One collec- Volpe* Alre ted fox. IIndividualt addi- *Cs.I# taPe. twolf. I isdiyiduai) angular, not water rounded, and the bombs have dense volcanism. The second zone probably records subaerial tion contained Valeonia cyclophorella Ancey, in tion to Parapholyz nevadensis, variety toward punMta. cftelte e. toruba squirretl I tndividuel) exteriors, scoriaceous interiors, and in places the beds nonrolcanic deposition during a temporary minor re- for several inches beneath the larger bombs are de. cession of (lie middle Sehoo lake. -i All are aquatic species. DIoetoossa(ntweed rat. 21ndividuals) pressed. This zone also is correlated with the dendritic The fourth zone of the upper unit records the young. Each of the fossil forms from the lower member of X. tpi (desrt weeodrat, 7 Indileldasl) member of the Sehoo. est eruption, which probably took place during the the Sehoo is still living in , except the x etecres tObr -iied weedrat. individuals) The fourth zone, about 40 feet thick, is similar to the transgression of the late Sehoo laike. This eruption was mammalian vertebrates, which suggest alate Pleistocene .ustots ferlrentcr (relitw-biiled srmaot. 13 Indlid- third zone except it is practically unconsolidated, gen- subaerial, for the lake lay well below the base of the tuff age. The predominance of the snail Parapholyz nerv- URte) cone. Partings of basaltic erally poorly sorted, and probably subaerially de- mnd in the lower partof the densis here, in contrast to the more general and larger Lepa lfeteenomirs ('ltacktaniedJaetrebbti.a tsdhidua1) upper member of the Sehoo formation occur locally list of mollusks from the lake deposits of Fallon age omiot'tmse7, tidsckiattersnuiedelerlIndidnUa)It,. posited. This zone is poorly exposed but underlies all within a feW miles east of Soda Lake and may represent the outer slopes of the cone. It locally is overlain by material blown out by this eruption and deposited in the suggests a difference in lake ecology-possibly colder Orbs caonstc. (niouItatin Aeep. IIndividuail eolian sand of the Turupah formation, and it beers the lake. water. -Btlo (blsO. I IndividDal) -t A-; I QUATERNARY STRATIORAPTr 75 74 74~~~~LAKE LAHONTAN: GEOLOGY,CARSON DESERT, NMv.7 deposits of Sehoo and Indian S. It. Wheeler collected a horse bone during his only wvhere buried by because relict occurrences are masked by the excavations in this cave in 1940, from a bed that N. L. Lakes age, stronger Toyeh soil. Roust (written communication, 1956) tentatively cor- younger considerably gravel of late Sehoo and relates with the slope-wash 1CITFIZN2vmrAMID SOIL or KrDDZ IWDIAMLAIXrS AGO Indian Lakes age. E. C. Furlong, Department of Ver- not named, is a barely discernible in- tebrate Paleontology, California Institute of Tech- The lower soil, profile that developed beneath the nology, identified the bones as Equue oecidentalis, which cipient weathering the lower and dendritic mem- apparently became extinct at the end of the Pleistocene. disconformity between of the Sehoo formation, which represents the same Bird bones from the slope-wash gra-vel of late Sehoo bers as the middle tongue of the Indian Lakes and Indian Lakes age in pit N6 at Hidden Cave were time interval or part of this interval. This soil is at most determined by Ilildegarde Howard, Los Angeles formation, 3 inches thick, and shows very weak prismatic County Museum (forms now extinct in the area are 2 or structure and brownish discoloration of the parent ma- starred) as follows: terial without obvious soil zonation; it is rarely pre- Hellfcel., leereecphela. tbold eagle, 1 tadividual) served. It is exposed in the saddle between Eetza (tfelcee. 2 tndl lduslst Falco uceimnus aorpcrelrlnie and Sehoo Mountain (pl. 8 and sections 41 alcon. 1Indlvidual) Mountain F. owe1rcoan-(prairie table 10) at altitudes as low as about 3,990 feet. Cicu. Aedsoeia( mwe.h hawk, I tadl-tdual and 42, (-l. I Ado up. lndlvidual) MARMONSCHOOL SOIL Bubo wvlpW.i.. (bomred orl. 1 Indirldual i I Corlynole nfW,-eoliI. (eared grebe. s indlvidual.) The upper soil of Sehoo and Indian Lakes age is *c. aurtla (hoceed gecie 3 Itrdlvidualsl School soil, after an abandoned greee. 2 lndiolduaol. called the Harmon Archaorpho-e. occideIe1i. (ne,"eer of its type locality. (glflflule, I idirdual) school two-thirds of a mile south -I Oallintla cAlnorpat the llpper member 0. ap. or Roll.. (talIlnule r ramlI tUdvlVdatn) It occurs only where buried beneath coot or erosion; it F.lce aeenrlcann or Gel6btle chloropul (Ameerlcan of the Sehoo, in places of little or no wave galltaule. I iedilidual) has not been found below an altitude of 3,920 feet. The Cull (tsl"oS Len. mrefo,.lca., I indilidual) is developed on colluvium of the upper or -gergala.. Itadtlidaal* soil generally Gull t l.1rof Lora- gla-ctcc.t Lakes formation or beneath the I lndlrldunl) tongue of the Indian Gull (.wsall, unldentlfied, formation that repre- SI Phalarevco, oa.rl.. .(doublcbreeeted eorteorst. s tndl- disconformity within the Sehoo ,]duals sents this member. Where best preserved, it consists of PClrcma.. c,-ilA orhv ac1ast nw ltc wl*ca. 1 Indlviduel) I or 2 inches of brownish clay having weak prismatic Ssadpipert?) (I Indilldual structure over a horizon of very weak calcium carbonate .1 Bract. algv-ce.-(?) (fgoose.I Ildlvidueet inches thick. Its type locality siallard?, I lidlldual) accumulation several Anus pl.t1hy.tcheot?) (table 10; see also profile 17S, 0 A. ecwa (?) (pintall duck?. I indivldual) is the site of section 17 Nycoca oftfais or Birlsioaicss .p. (setup duck?, b Iudl- table 11) in SW¼4NWY sec. 24, T. 19 N., R. 29 E. Its Vlduest) profile here is modified by the superposed C,, horizon N. rp. ( duck. 5 indlivduals) of the Toyeh soil; such a modified profile characterizes lefe (?) (wbite-wlsged croler', I tndlvidual) 1el..etia most occurrences of the soil west of the Sagouspe fault Prce *p(?) (otatgple?. I inldivdual) Cccv,.- cen, (hotlarc le raren, 2 tandlodual,) scarp. TUUUPAs roRnATIoN gra-el alsoyielded plantseeds identified by H. L This OtlUAL TZATURZS Mason, Department of Botany, University of Califor- the La- nia, Berkeley, as AmainkN sp. (yellow forget-me-not, The Turupsh formation is the youngest in sand and or "fiddleneck"). A few fresh-water mussel shells were honton Valley group. It consists of eolinn and under- found, probably Anodonta califorsicnsis. alluvium, overlying the Sehoo formation The richness of this layer in vertebrate species and lying the Toyeh soil aid Fallon formation. These sub- from far above the individuals, compared with the post-Sehoo deposits in aerial sediments range in altitude paris case, suggests a more abundant vertebrate fauna Lahontan beach to within a few feet of the lowest the discon- subsequently. The preponderance of modern of the basin floor. They, and a widespread than record a species and probably occurrence of Eques occLdentaliS formity that represents the same time inter-al, was completely sulggests a late Wisconsin age. time when Lake Lahontan generally dry. tozLs or aassoo AND INDIAN LAK38 AUX The type locality of the Turupnh formation (Mor- of eolian sand uorthwvest Two very weakly developed soils are interealated with rison, 1961a) is the exposure that extends about 1/2 mile on each side tie Selico and Iidian Lakes formnations. Both are seen of Turupah Flat I e9"-u o-54_4 -I '1. .it Uis LUIO~rAI: oneWT, osaMMe onsau, M. VUATS111141110aTUaINm1? 77 he a rad ouh from US. Highwy 19 from the of the younger lae ( 8 feet), ad by both-oli * naemharefthefle~wi few ncheasf thesurlsfa,gravel th is orrelated geologically *ad archeeslog- VI Om 3 to the 8E1A s& A, T-.Ss , IL 20 X sand and lesdimen tbWof lth ,1melo *thisalitd along the southand went lrdee ofZiglahtnila t keUy with h Sdmoo and India l&IAN dVOeS, (figal)). .. , .. , . :. . ie san discoonfecshy Overlies cloy of ta* Salloat A-&W d"t4 een s d&Ao" ally ben te Tejea si and is overWa by -U- Ito distaie end f 6 pin"- ad unatlies TM p w ;d ;oU. lyrs IIe lowladt r° -- eof u toslytion_ . Wad w t I l1cusstrine sn of11g. yaln fdoliem . show that the wiad w sand ly te __ d~~~~~~ton;alar Ut appmasetly records th masimue, iclisa generlly. U"esupon a wimleoatsi resoes s"lo thac motivity of poet-Seles time Itet -6. of asmuc as etio. is (tow 10) Sowo ypicl stratigphit se- Seh" mm yoamalrmationa ntm esenhl -4.4 of the CaronDeartl M b of '-d Wa caved lato the fshes end Wy4meks formationmd oeimisp"isay A w sos and eon of the 00ia sAd to td TooO slil abd OA the ois send ONthe .Z' lt Sebms dela ws derived fhe la him "ad ' a is c onised hi awation hea % i partly slp wah la LeUNad todsheltr, an lnpoer.. boalnfesmatbos., . z5 -~~~~sa sd s Udtg -h esoia send lgearell nemele plains ather he by lulia feates. The inbt 1 la I isatures aftewabatPrasIsomnb to 46 wke of 96 tent SsmelaouW".Jsite theaIn W Humb', poldLags media &WdI locally UcomatainsIt Oesideraws ma aoethweetera half of Wharea IDOSeSsof deflation" I".~vlok sen, 11ev, The. isllecottaitadW"teohad.y Dietrlktion, -ePlA-le sa t- dwh. ie grit, and *ee small pebhe. it is psb yalowish hernia hell a smile to several miles wide, are scoooped pgay teooi-white, mnindated except wher couated il theneiaooAWa (ruireh messtdwtht. 1 ANS-Wola en is the characteristic "an most es- common SOto 40 ftasd relyGo f a thJbaier,ef a ae lt) v deposi of the Topph formation. It ocas by the Toyrb soD, ad has obscure to distinct atratilca low the top of te S e, tion; i dpltieo Near the bae of the low of the UupeinIn , dunes d small up (tensive dunse eomplex), tlon-sltlmepavallelInclineorcrwsahdded. Locally has eroded entirely thirou this bfesiati. as much Cave Is a dioatus"M partleg of White pumictous ad utalna a minimumo *uicnoes of about 30 feet. It it contains coprolita (probmbly coyoe) and rodent ma30 feet into the Wyeema&a formation. Carmso Sink as Mlie to kinh, thic A similar Whit beas. The coasest deposeita on ash, part- mped only in the eatern quadrangles, but it is alo the west late Sebo, is a boo deeion plain; as atwestere peut is so IgW" Observed nar th bee af tme correlative de- idead I thS wesn qusdmAles, It ranges in .nd Astard to the S-lan lasoror A this strongly delisted U" the Saboo formation generally post of dtkberml teervoir ag In LAosardeechsholtr (Raer, Itituda from abo the Laheotan beach to WU fee-- the snd contains many frogmunts Of Lt u bowentirely strippe away. TM plain continuesa 191). Tise pestrags may conrlte with tim one lithoid bfa in Imost to the bottom of the basin. T1h lowet occar- of the upper member of the Sehoo, meetly about I msailesouthinetwrd from the math rest cor her t o mrograpfhic enam- esrutPelican Island nd Bettleground Point (on le than an eighth of an inch acroes. Near Salt Wrils of the ink pat eth d of Upda Hoghach. os th lat of the ail from both saxs. beds contain a cah indicates am it be outh eage of Cason sinkj, and in the eastern per to 30 percent tufa granules lat Beho del dielat" W" ieiguuicant an pabbly Voleank-aAperilag.-A parting of white probly Me from Mon Cra-%Calif, though bot .f the Indian laws aea, whrer it is mostly buried by pamiaom sand Of tm Indian LAM formationb dis nbtrilv- lJe tlwhsso" euption (witten reper, 390, alm and eian mend of the Fnllon formation (here its ash, ' to rarely as much as4Slnt thWck, cur locally charnle,lut itWai otmmonlyeOn ele In 1 yby Iowel WilUiam, (ol Dqarm t 'Univerity ,henr-foe dinaitlo was studied by m7an gr in the lower pars of the eli send. This peting is ta We Oded in 1 f dotTo of Id California, erBeelVa, higl discontinows and nnot be traced ie -than to IL F. Yiser, Anthropoog WINs). t unmarr mlr af the "- IAma delaion a. at, sea university). stew fet Many giren The ornl dam form a sti dent in paces, loclity. It is certain tbatit bowda Othe large exposnres of clay od the Silmoo Is everywhere a single sithough Od a i in type, distribution, ocientationt and horiaon, n mare tha formation, wsas Ban Flats, Trumpes Flt, and m m* Ular was IAn St SAY one locality This peta Eagihnle FhL Prahlymoe than oeelf "bi lsrion of the Turupel _m " Is exposed in pvbbly in elseaid shape to the preset dune (p. So- lag on be see at the following localities: (a) about the %orthweatsra Canson, loluike d ortheastern Fallon is). In the highlands this volen snd is e %t"e .4. mile of seiment I" ted from the lowlands of a quarter of a mile southeast of Salt Wl; () is a the map Atka. quadranagise *dlsCotinuW e rinsnt%109 t o00 fast timoelginal distribution of oolian snd Of the WY'S rod et S.8 miles waet l Wells, on the noLh de wide, tha e a r lew abe. tdo prsent good pla. nahb forsiatima, for it isabaca from many ses Mad of TuropsimFIM; (o) within a few hundred f"t Quantitatively Iseigailicant, roes d*ne a fIser channel Ose of the Cason snyoswhe femnnatoth olderd a*rep west edge of the northwest prong of tbe Balog ye7 sseuosI el River of the highlands, is bak of lo T that _ammemd half a nas out of Fallen and In th lowlands the e send" commoly *ersed Mouetalne; (d) ear WIshala siding e the raMd, l maaadeeedeastwedlorl . Thee bsompltisparty Mile wit of Fallon; nd (a) inta aild It rngs f-*M lees thi I inc to Rarely M" the he R4shesfoen , or locolly the Uso-mah, Ith ate the wt 1 a ngle ad partly ado" clMmel irr a gradient mad eof the Cason RirIbgod foot i tickn e, is mety s amd Gm sand, nd is dieconfity owing to dedaim of btsile Pln 6 miles nes- generally at shost 4i lea per Wils-eheut the same a the pete. nortl hestefmF locandymimhesadof t 3 indistinctly bedded and u i rsomeOmteAdpila fl6elow an &aOtiadoflSAWfetit is tjeor dimeat.t generally imeoverl by Soua slpe wash is isaet"ed locall. The tases the wad of tme yal formation, above the highest ll sIma uash paring locll oenrlie sand of the upjme ee awmesesoethtme Faills teuei -,bti has ee Toyahe soil, where i al has nt bes ndTh Uteaed Is the sahautfaca aboit hell a'Nmie orthast los is MCA osem en the eatrn piedimesats and war whsre it is almost 10 let lOw (ecion 1b Ii oammoemly Is harely netlosei en the western "ae; it tabe 10). probably was derived min* by delatio tram th low. Read pits In thislarvia show mmh as 18 feet land of t Canon Desrt ad trasiort enddepai- of inditinctly trtfia fivooepehhly mars send sad Sien by westerly winds It is annyingy orident am aomes smsim sand, which Is aeletivul homosenapu the wdtent piedmnt of th Stillwate, Rags, e. at far. Seat Wi o Bos ad at he1top which sea Of tW p eras, Ibs Of the det it CoMO may he yonager lke sand le PeAble are gasismic, oen arfacsd re The emell patches of lake day gramit. "We WOUSm seeks similar to those In the SW sA of the Fallon formation in poeed Ua_ of preseat had of the Caron Riser The a visa boor the highlands e mostly derived frothis looe. the '*e soil, attetng teos pee-Fallen ages Several eaas aWscotals beds of ti ls (without Uany lc "poeur f 0CsmRinir Channel sad V aWU~ 4 s a e . ~sW4 e . .Ar*W n. 5. sOf ma.. M Oets. s 6e MsAW*ses. I ru w*s~.1 t ." etnu r 55 . . the ToA soil). Tlm nain loeli deposit at Iiddes of probable Tampok ofe a0M st.rm.a 3ew. W~ IL T. eSt X.: so have bom Sound in drainage IL. m0I 6useS 0 a w..w1e. e %be smm"iesm .. w.sb s 0 m.f dm.Is ee-m Cave (Unit "s " , tah l0),is correlate with base i-Makka. "a onOe k- I ILdrs~es5. 5$e.M . -11Me ,e.6 M "WVse r 0sd em.oo.5 tonShwe 5 a too5 Iae draiage cania, at te qsetsrfeatisn of ue modSWVn~ *d soft MO~af Am. &a hbeefteet MMiS.VubW bemtads. the Tarupsi formaion heamue it ovrllens slope-was monr be- t 78 LAZE LAXtONTAN: GEOLOGY, CARSON DESERT, NEV. QUATERNARY tSTRATZGRAF1 79 tween sets. 82 and 33, T. 18 N., R. 29 E. (section 48, developed than the soils of Eetza, Sehoo, or Fallon age, marker than its true degree of develop- lag less than on relict strttigraphic table 10). Here 24 feet of pebbly coarse sand con- and is one of the most useful stratigraphic markers. pebbles of the gravel-soitewhat occurrences of the Churchill and Cocoon soils. ment would warrant. i, inch in diameter is exposed above taining pebbles to It is not evident on relicts of the Cocoon and Churchill The vesicular (A) horizon, characteristic of the top Modiflcation of the soil profle with stratigraphic water level; the altitude of the upper contact is about soils, because it is masked by the stronger development part of the profileof Gray Desert soils, is relatively well occwmsem.-The Toyeh soil has everywhere a similar 8,913 feet. of the older soils. developed inrthe Toyeh soil. It utderlies the lag gravel profile, but it naturally shows sonmewhat greater de- Type &ocality-Thetype locality of the Toyeh soil or merges with the lower part of it. It is generally 2lh velopmettt where the surface was exposed and stable for Dni0orottv0rrY cOzEAL WITx nTz ustrPA rolxATtx; is the site of soil profile section 16S and strsiigraphic long intervals before or after the Toyeh interval. Such ZEtMEROX OF COORT5XT LAKE DESICCATION to 3% inches thick, and is white, very pale brown, light section 16 (tables 11 and 10, in the bluff on the east side gray, or pale pinkish gray (1OYR 8/2, 8/3, 7/3, 7/2 to extended intervals of exposure had morm discernible The diseonformity of Turupah age is particularly of a wash about % mile east of the northeast corner of 7.5YR 8/2 and 7/2), and characteristically consists effect on this soil than similar intervals had on the widespread in the basin interior. It has been observed the S-Line Reservoir. The soil is on eoliasn sand of the mostly of silt and silty sand; even on gravelly parent Churchill and Cocoon soils, because the Toyeh soil is she as low as 8,875 feet along the southern margin of Carson Turupah formation and is buried by a few feet of material and where overlain by lag gravel it contains least strongly developed of the three. IThe difference Sink. Its deflation features and their effect on the younger eolian sand. The very top of the soil appears few pebbles. It generally is somewhat calcareous. It in development is most evident in comparing buried upper contact of the Sehoo have been discussed above. eroded here but an example of the full profile can be has an almost frothy appearance owing to many small occurrences of the soil on the Turupah formation with That the Carson Desert was at least as dry as now for seen at the site of stratigraphic section 32 (table 10) round btbbles or vesicles, which range in diameter from relict occurrences on the dendritic member of the Sehoo of deflation in 32 (table 11), which is typical long periods is shown by the amount and soil profile section less than 3A, to rarely more tItan 1/4 inch. Soil struc- or older units, because the latter had additional incre- '1- the low areas. Even where marked erosion is not evi- of relict occttrrences on the Sehoo formation above the ture is weak to moderate medium to coarse columnar ments of weak soil development during the Harmon dent, subaerial exposure is manifest by soil develop- late Sehoo lake. and comnmonly also weak medium pInty. Consistence School and L-Drain soil intervals. ment, mud cracks, clastic dikes, and plant remains. is slightly hard to hard, friable, harsh, and floury. Variation toward Sotoncake and Selset a Foil.- during Turupah PROFILE CHEAACTERVITICI Probably complete lake disiccation The oxide (B) horizon has at abrupt boutidary with Iocally in the lowlands the Toyeh soil formed on saline the minimum altitudes reached time also is indicated by The Toyeh soil differs from the Churchill and Cocoon the vesicular horizon. It generally is 4 to 5 iticlies thick silt or clay of the Sehoo formation, or where poor drain- feet for ealian sand by the Turnpab formation-3,875 soils by being consiiderably thinner, less strongly de- and is light brownish gray (101-ft 6/2), pale brown age lis caused stit and alkali accicmulation. In such and below 3,910 feet for alluvium. veloped, and by having less sharply differentiated hori- (IOYR 6/3), to locally brown (10)R 5/3) or grayish pilaces its profile varies toward n Solonchak or Solonetz zons. Its full thickness is generally about 10 to 14 brown (101'R 5/2), commonly grading somewhat soil, ratlher tIan the typical Gray Desert soil type. The FOSSILS inches in sand and gravelly sand, but it ranges from as lighter downward. Texture is approximately that of vesicular horizon generally is Jacking; instead, the A Two collections of bones from coyote( l) coprolites in mitch as 20 inches in gravel to as little as 8 inches in the parent material, lthough megascopic appearance horizon consists of a light-gray (shout 2.51' 7/2), eolian sand of the Turupah, from the east shore of clay. At its top is a vesicular (A) horizon; beneath suggests slight illuvintion of clay antd silt, which de- highly saline, surface crust about I% inch thick, and S-Line Reservoir and from I mile northwest of lHarnion this an oxide (B) horizon, and a horizon of calcium creases downward. The available mechanical analyses, an umiderlyitg layer, one-half to several incites thick, School, were examined by H. W. Stet7er, U.S. Geo- carbonate accumulation (C,.) (fig. 30, B, 0). The however, show no significant concentratiotn of clay and of light-gray to gray to grayish-brown (about 2.51' logical Survey, who identified the following genera of oxide and calcareous horizons overlap gradationallv; silt. Generally at the top is a partitg less than /l inch 7/2 to 5/2) highly flocculated (aggregeted) clay loam rodents: Reithrodontomys (harvest mouse), Citelluv clay and oxide accutmulation is greatest at the top, and thick, more clayey, more highly aggregatted, and more orclay hrvitg n strong finegraitular struxure and loose (ground squirrel), and Sylvsiagus (cottontail and allied calcium carbonate accumulation greatest below. The friable than material below. Structure is weak coarse to fluffy comssistence. The B horizon commonly is rabbits). full profile of this soil is preserved more commonly granular to weak coarse prismatic or columnar; con- darker than in the Gray Desert soil facie-light brown- TOYEB SOIL than that of the older soils. sistence, slightly hard to hard. Calcitnm carbotrtte get- ish gray, griyisih brown, to dark grayish brosvwn (about The profile varies more with variations in parent ma- 101'R or 2.5]' 6/2 to 4/2); it is moderately compact, STIATsGaAPAIo RELATIORS AND OCCURRENCE erally is tteitrly completely leached fro,,, the tipper part terial and other local et-irontitental factors than do the of the horizon, bitt increases gradually downward, and and has a stricttre ranging from strong columtnar Overlying the Turupnh formation is a soil that has a Churchill and Cocoon soils, not only in total thickness, the boundary with the C.. horizon is graduial to diffuse. (Solottetz soil) to g-anuiar (Solonchak soil). The C, moderately developed profile. It is called the Toyeh bitt also it details of the B and C.. horizons. For ex- The calcareouis (C,.) horizon is less sharply (lefined horizont generally is telescoped to less thant 9 inches soil, after Mount Toyeh, an old name for Rattlesnake ample, the B horizon is weakly developed in clean than the other horizons and also varies more in thick- thick, as usual on impermeable parent material- Hill, which is near its type locality. Typically it is a gravel, bitt well developed it silty or clayey sand and ness. It commonly ranges from 6 to 14 incites in thick- but the calcism carbonate cementation is correspond- Gray Desert soil, although in relatively saline locations gravel, ws-here fines were available for illuviation; the ness, is light gray to pale browvt, light browtnish gray, or ingly stronger than normal. it grades toward a Solonchak or Solonetz soil. The C,. horizot, obviously is best developed in calcareous pinkish gray (10)'R 7/2,6/1, 6/2, 6/3 and 7.5YR 6/2), Toyeh soil is considered to mark the top of the Pleisto- sedinient. The following general horizon descriptions and comnitonly is mottled with whitish spots aind streaks FALLON 7O3tMTIO5 cene deposits in this area (Morrison and others, 1957, p. refer ottly to locations that are relatively flat and well of calciimt carbonate. Cementation by cichium carbon- OENERAL FRCATOIRI 890; Morrison, 196ld). draited, where the soil is relatively uneroded, and ate is very weak to moderate; consequently the struc- The Toyeh is the most widely distributed soil in the where it developed on sand or gravel. ture varies from nearly single grain to wveak coarse The Fallots fonnatiots consists of stilaerial and shal- low-like sediments of Recent age directly overlying area. It is not only widespread on the lowlands-to at A lag-gravel layer about one pebble thick veneers granular to weak coarse stbntgitlar blocky, and con- least as low as 3,890 feet-but also is nearly the only this soil where gravel is present in the sinderlyitg sedi- sisteice frotti nearly loose, to soft, to hard. The calchim the Turutpah fonnation and the Toyehl soil. It was soil in the highlands below the highest shoreline of the menit, but. with a decrease in abundance of pebbles in carsonate cottcentration gemierally is so moderate that named (Morrisoti, IDla) after Fallon, near which it is early Sehoo lake, because the Churchill and Cocoon the parent material the Ing gravel becomes discontinu- the C. horizon is incotsspicaouis it fresh exposures. In extensively exposed. This formation is thinner and soils generally have been either eroded or buried by ous. The lag gravel is believed to be cogettetic with the weathered exposures, however, the horizon shows as a smaller it volmte than the 1.ltonitan Valley group, yet younger sediment. It also is widespread above this soil. In sotamelocations younger drift sand partly cov- soissewist resistant pale-grny to white hand (fig. 30D), is moss widely exposed. It is the dominant unit in the shoreline. This soil is considerably weaker than the ers the Ing gravel. D)esert varnish is sparingly devel- becarime the lime is concentrated at the surface by eflor- lowlatids and is widespread in the highlands except in Cocoon and Churchill roils, but is much more strongly oped on the outer surfaces of the ntidesitic and basaltic escence. This commonly makes the Toych soil a better the steeper parts of the mountains.

I - __ _.' ___ f - - I P_

LAKE LAIOlXTANu:- GEOLOGY,CARtBON DESERTI, NEV. QUATERNARY STRATnORAoHY 81 iis formation, though mapped as a unit, has gener- climatic changes in the region because the Carson Des- -. ments that overlie but are very similar to those of the MOLIAN SAND seen subdivided in strauigraphic sections. Its sedi- ert is the terminus for the principal and most repre- lower member. They record at least three very shal- Dirtnbutioss.-Eolian sand is one of the most widely s have been studied in special detail because of the sentative drainage basin. low lake cycles, called the third, fourth, and fifth Fal- distributed sediments of the Fallon formation. It action of its record of Recent lake fluctuations in The Fallon formation is subdivided into two memjt- lon lakes, separated and followed by virtually complete ranges from tiny sand drifts a few inches thick to Carson Desert. This record reflects the Recent bers, lower and upper (fig. 32), in stratigraphic sectiotns desiccation. This member is differentiated only below extensive dune complexes (ergs) many square miles (and locally slightly above) the highest level of the in area and locally more than 50 feet thick. Its dis- third Fallon lake-altitude about 3,9M2feet in the Car- tribution is controlled by the locations of source areas-chiefly expanses of son Lake area and about 3,915 feet in the rest of the sand of the Wyemahs and Sehoo formations-by direction and amount of wind basin transport, and by local topography which favors The type locality is the Raymond Cushman Ranch, deposition. in sees. 28, 29, and 33, T. 18 N. R. 29 E. The member This sand underlies at least one-fifth of the north- here consists of lake sand that was deposited in a small ern and western lowlands, and more than half of large delta of the Carson River at the high shore of the third parts of this area. It was not mapped in the Fallon Fallon lake. and Sods Lake quadrangles, in order to simplify map patterns, and it is even more extensive than the geo- LAKE AND INTS L&KE UNrJs logic maps of the Carson Lake and Stillwater quad- Both members commonly are further subdivided in rangles show, because large tracts are drift sheets too stratigraphic sections into lake ald interluke units on thin to be mapped. Few places in the lowlands are free from it, for almost every shrub lodges some drift the basis of their intertonguing units of subaerial and sand, but it is rare on Carson Sink and the other playa lacustrine sediments, and ihis stratigraphy is summar- flats because these bare expanses favor deflation and ized in table 7. Morrison and others (1957, p- 388- transport, not lodgement, of sand. It also is scarce in 390) have pointed out the posssible utility of these the Carson Lake and Stillwater Lakes areas because units in recording Recent climatic history and subdivi- the sand was stopped by peripheral vegetation, even sions of Recent time in the Lake Lahontan area. when the lakes were dry.

TAst 7.-Subdioroie. of the Falleaneneatiox t~t~olat ah c oe ct oo ~ eo tml het . d e,.itted - ft u eota b..ha t Altttu d fhl1hWtto A tttcdl tite..,lt de Bhdt t 1)a od _..a te dttt Bubdt"d.o "It c amorl c"_= Noerhm It 32.-patl . aeortoI di..o fe. bIt o. 5.h to.t thIe.; t. oodfo ettr retpre t. th . efr thb Tr O a.b re-atton. Top l hotsee an ta e e ss et t toesnoa I.t .ao d Oao pt, .,ooboroE tbe 7.110toe t toQfo: aest I *oIt tf - bo..- illtryrlc of tohr.. .I her at the ros. tutu .1tb ..b r-tigf at tep cad Wat ttoot .notct 5% fo.t to -.t., Hlea to yet t the deadette .04 cot.. _...3 9 ..9 .... -_ 3.906 3,88_ A.tee. Oftthe ota wse o S~t~l-t t-c Staouh ,t Xeot Rt-b. wt e. 5. T. 15 N.. . a1Il ; A.t., I..tr ceat 3.a85-3.590 feet ctttd.. Young lake cnd Interlake , 1 3,890 ...... Upper unitk., 3,910 3.iaf itudes below or only slightly above the highest Station reservation (as of 1950-not as subsequently member. 1 3, 8al g of the Fallon lakes. Botl members consist of enlarged), sees. 14, 15, 22, and 23, T. 18 N., R. 29 E. Fallen tfor, Ttrd lakte unt 3,922 3,93 ---- ow-lake sediments and intertotguing subaerial The plain on which the station is located is a com- Lowers n Second Intertake uit .... 3, 910 3, 8? L-rain soti ents. The entirely subaerial sediments at higher pound delta of the Carson River that was built into des are not subdivided. the first and second Fallon lakes. Sections 18, 22b, member. Second lake unit 3a,93O 3,. 930 .----.----- LoWIR 5X1st5:tt 23, 35,37,47, and 48 (table 10) illustrate typical lithol- Firet Interlake unit ...... ---- 3, 910 3,900 ogy and Dlower mentber is the thicker. It includes sand, stratigraphic relations of the member. First lake unit 3.948 3.948 The lower member conformably lay, gravel, and tufa of tlte first two lakes (lake overlies the Toyeh soil, except locally where the soil was eroded by wave 1 Toyeh "at 4of Fallon time, Fallon lakes I and 2, whose action of the first Fallon lake. This soil is a relatively nums acre at altitudes of about 3,948 and 3,930 conspicuous and easily traceable marker for the lower wepectively. It also includes alluvium and eolian boundary. The upper boundary lies at the top of the which were deposited partly during the lake cycles second interlake unit of the Fallon formation (table artly during intervening and succeeding intervals £ :e recession. This member is differentiated only 7). The L-Drain soil locally represents this unit, burt- this weak soil is a poor marker. the highest level of the first lake, except for the um and eolian sand that intertongue with the lake 17PPER V21,2I1U3 ents and locally can be traced higher. The upper member consists of late Recent to present- s-f I type locality is the Fallon Naval Auxiliary Air day intertonguing subaerial and shallow-lake sedi- I

QUATERNARY 8TRATIGRAPfr 83 LARE LAHONTAN: GEOLO(GY,CARSON DESERT, NEV, I Fat.. f|rmenioa-Continued ToALx 7.-Sbdw ioi.on of (A, F.iln fermotiotf-Continued TAjLa 7.-Skdivinmom .1 tlhe S antsodt.. Satn O estot.d hofn enom ltse. Unlt Danonlan -d tM 1ltr Is hmsor rsard.4 - ate 0tlbn sod ttro 1sum, Lnk.bbSOct , d ba,

Second youngest interleus Second youngest lake ree..i Sediments generally dilferentlated only whbee over. Youngest part of FaUon fot. In Carona Lake areo, fourth Widespread on river flood plainsand below high o*& trine tongue of Fallon for. on of Fallon time, to at lain by lake sediments of third lake unit; spnrse; mhtion, Ineludes peeont- nod fifth Fallon Lakes, of fourth Fallon lake; from n knife edge to abtut matlon, intermediate in lesat sa low a. 3,910 ft lena than I to rarely 6 ft thick, Chief oeeurence; dy deposits and overlie. maxlmuma (contgruent) 10 ft thick thbedkot iD alluvial cihannel, deltas age between the firrt snd In Canon Lake sea and are: (a) The delta at the type locality, where tiud lat unit. Contains 3 919 It alsopreceding, ,nd bxo 1Lke sediments generally differentIat second lake units: olian 3,81iOft In northern are.; aluvial and lake sand and silt overlie eloy of the very skallose l ke sedi- istorvenlag, And followr- only in bigh-obore onoe;hero mostly fIne eand nod sand. alluvium, and very probably desiccation was eeeoadfake unit and sen overhtln by silt el*.. and 2 mdan lg denltectlon Intervals ailt, locally medium sand snd clay, rarely fine at time., par- sand of the third lake unit; delta is =d to a mrent. (probably sedimenta,silt, ahalowlakes diinents;sp- complete torgue. In Caroon Lake C.roon Lake probably grnvel and pebbly sand; offshore prlaimately coeval with ticldrly In northern ares. 3,911-3,915 ft Shoreline, that is, close to present a rea epresenting fourth overflowed to northern nd silty .1ny, generally very clrbooaeeous. grny to i the b-Drain soil, level of Carson Lake; (b) east and south shores of fith Fallon lakel, and noo via Stillwater Slough blaek. High shoreline. only locnlly discernible, d Carnon Like to bane o Wildcat scarp, where there a nd and loenl tiny Type locality: Greenke 2or more tongues in north. during both enoaimum*. marked by smtIl deltas, rare barn, " Duck Club se. 9, T 17 is sollen sand no low an 3,912 ft, alluvium down to nrn area) and mntertongulo6 HiNtory In northern area terracc bordering dunes nd deflation basin.s ILN.R 29 E about 3,918 ft (ea lp, 684sec. 29, T. 17 N., t. nad coeval alluvium nd les rertain because of Deltas madnly hne oandand sit, occur In e. 4, 30 Et), also atone artifact. (manoe, metstea, point .r. -n 'slnd. correlatlon difficultles; T. 17 I.- 2D.; N% T. ID N. and 8% T. 20 N., r2 chips, and other.) at several open archaeological ! Type localit Lowermost of probable several very R. 30 E.; and at prrsent river mouth at south edge V sin, which rent on lake aedimenta of aomnd Inks a two small gravel bs at sZntl lake cycles; two of Carson Sink. Tiny dlsoontinuous barn of fioe unit and encrusted with tuts of the third lake unit, o bnse of Meildat satp main maybe. at ahout peblbly zsnd and fine grvel along haso of Wildcat easloaw a 2,910 ft altitude; (el vicinity of Stlllwator c~ NWh arc. 3, T. 10 N.h. 3,D90iand 3.801. Lst scarp north of White Throne and Bunejug houn. SlOugh (eolin samd as low as 3,910 It); (d) e"ster _ 29 E (fig. 33) lhich onark. manimuma in both oven talons A 2-n. to I-ft bed of lacustrine silt, prob. Stillsater quadrangle west of Stillater Lakes I highest (conroert) shore.- occurred About 1802 A. bly of vulcunic origin and coe a1 with thc (elolin sand ts low an 3,880 ft). Section 49 (table ines of buth lakes It D. See toxt for river 3,905-ft maximum, ib widespread betveen Indian 10) Illustrates thin unit. locally the unit is area, history. Lake. and northern Stillwater Lake. Alluvium represented by a diuconformity, recording weak 2 Caron Lakc ond I. in former Carson River chantels in mainly One 41. eclian erosion and small-ocale gulvling (forexample. medium ond, commonly somewoht pebbly above along Wildcat cacp); the L.Dratn oi is approxl- 3.920 fit; pebblcs rarely excred I In. diumeter above mstely coevaL 4 000 f, and half an Inch below 3,900 ft. Inter- I harnnel alluvium in mniinly silt, locally sand and Second youngest licustnr econd Fallon lake. Maui- Relatively sidespread below second lake high shore; clay. Eiolhan sand i ommon occur even in tongue of Failon forn- munnmaltitude about 3,930 lena than I to rarely 0 ft thick. atke sediments: central Carmon Sink. No discernible soil develop- tion: lake smd, alBt, clay, It; reonaloiul stilistand sand mainly In high-ubore sooe, 3,930 to 3,925 ft. muent, minor amount, of gravel at about 3,927 ft. See especially on deltan Antd in dune area. gravelly and tuh; also coeval td- text for rivor history saud and gravel only in local highbehoremen near Thind youngrst lacustrite Third Fallon labe. In Car. Lake and Alluvial sediments closely resemble thone of luvil sad; lntermedinte mountain.; silt and clay whidespred otftkore and dbstri- tam rare. tongue In Fallon forms- son Lake srr, masximm ruyouglake and Interlake unit In lithologv, in age hetneen first and boCAI1 preznt even in high-shore aonn; lion: Inke ontd. aldt, clay, w"o at sn ltitolde of bution, and thickness. Lake sediments, however. second Interlke unit.. AlluXI and One pebbly sand of torser river atnd tufb; *bot 3,922 It. hen thin g-erslly ar. very rich in calcium carbonate, andi Type locality: Flat south- channels In many remnants on river flood plain and local lake gravel tratigraphle asetilon. Are: alno coeval bl.vianand lake occrfloned to north- small gray iufo nodule. are locally common; l ma vwest of Etetan Mountain deltas. Representative and silt. ern ara. In northern lithoid tufa as much as j1sIn. thick locally encrusts *X (northwest of Tauo.I, 18, 24, 28, 29, 35, 47, and 48 (table 10). Type locality! Uppermost of area,manimutltwuabott pebble. cobbles, bouldenr and *tone Artifacts, Flat) SNANwe 29, NX Highett shoreline wonkly developed, thousgh most edVr. of Canon E altude two small bars at baseof 3.91t ft and aoproil. particularly along south and east v see. _2, N) ;4c, j, T. prominent of Fallon age; is generally at no 24); mtnssel shells (A.neats c-lif.or but between Sehoo Mtountain and Wildcat s=nrp ,,orth of maetl coeval with that Lake (fig. l h - ISN.,R.30E. Lkesand of 3,930±3 ft, As lWhite Throe Moontult In Cauon Loke arcs. ht wienme) are abundant In places In highbshore ore. k and sllt of the unit are here Stillwater Point Reservoir It descends As low i NW, se. 3, T. 10 N., R. posiblv alightly enrlirr Sections Illustrating this u,,it are Nos. 48 and 49 r; prominent. 3,20 ft. presumably because of local dlermatilon. 29 E. (fig. 33). Thbi bar or Iter (table 10). ligh shoreline only locally dlia 9 Hlgh shore aone In marked by deltas, rat. barn, And r msrko highest shore of cernible4 marked by three compound de tas of T particularly by shore terreces and aasths bod"ering .i third Fallon lake. Carono River, rare small bars, and tiny terrace deflation badnh and dunes. Main delta inin E) bordering dune snd deflation basins. Deltas are T. 19 N., R. 29 E., overlapping northeast aide of mailv fine saod, soome medium sand and silt, 11 the mat delta of the firat Ise; anothar delta Fdea approximately to high shore; deltas in three may exit in area of the weot delta of the irsntlake, aiitics: (1) we. 20, 27, and 33, T. 18 N., R. 29 T. 18 N., R. 28 E. Bars are mont promiaent along Et, see. 7 and 8, T. 17 N., R. 29 E,.and arc. 13. l A* northwest margin of Bas Flats here tey Are fine T. i7 N., Rl. 28 E.i £2) Nw3, T. 19 N., R. 30 Et.; gravel, loctily 100 ft or more wide and )J to 4 ft 13) Carnon River valley near Woif Dlvernion Dam, thick. Shore terraesf are best devloped In belt of see. 21, T. 30 N., Rt. 29 E. Tiny bar. nl fine pebbly dunes west of Sunejug and tabontan Mlountains sand ;nd fins gravel occur dlscontiuuoitsly slop5 where dunex were beveled commonly It91 ft And _ baso.. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.of Wildcat nrsrp near White Throne *nd locallyr everni hundred feetl Faint recessional BuneJug Itluotntlns, and very rarely on the deltas shoreline at a~ltiude of about 3,927 ft, marked (for esamplleiace 33, T I1N. R1.29Et). matnl by mieel . of clark groy earbontaows and ( and dl eontaintg abundant snail sbel] and tufa fragments. An: Oldest Interheustrine tongue First Fallon lake recersoion, Rare, dlff renthated only where ov.rhinilrrby eond of Fallon formationn int r- to at least as low as lake unit; less than I to rarely 4 ft thick; locally id' m diate In ai~ be~twft atIdtude ot 3 900 ft. obznt and repre entcd by disconformity. Fmllsn iorelndf eccondiak, unit-; sand tecun locally In dune belt wedt of Bunndug a eioln sand and alluvium. and Lahontan Mountains, Aidel " rp of S. ouspe t Tyr locality: Fist bet rt n tault zone, and ed ewhere In Aillwater *m gods Ai mEt, MoSuntaln Fad Stili- take qu.Arangles to at Ictat aslow ex 3,9 00 ft; i water Slnugh mainly e. mostly fine-medium sand, iomefine nd some and grit. :f- t 20. T. 18 R., R. 0 E. medium mond practically no were, mand rg Unit betr is molan mod, Alluvial sand and fine-pebbly sand, in former locally betwen lake sands Carson River chansnel, locally expowd in mantia of firnt and serond lake In northwest Carson Lake qmdrangle, as Inw as * .7: uZunits about 3,910 ft. A little Alluvial sand ad silt at .

.. low as 3,915 ft. Strstigr-phic sectios illustratlng this unit are: 22b, 25, and 48 (table 10). I'

,!

'.. r :lt - i.

LANE LAHONTANf GEOLOGY, e I CARtSONDESE~Rr, NEV. QUATEIRNARYB's-SATIGRAPUY 85 -1 Tuss~s7.-Saidivsiemse of as Falloenfermations-Continued\ : Each of the three main classes of dunes is present fine-medium sand size and the other in the coarse sand (Smith, 1948, 1953): phytogenic, psammogenic, and and grit aize. Fragments of clay from the Sehoo for- 5755 Do"We. sndsic. feeder, lake. II ' 'Y ..as at sumd. a-z, windshadow. mation are locally incorporated in amall proportions; Phytogenic dunes, formed where the desert-shrub true clay dunes (lunettes) are absent. Very rarely Lecustriznetongue in lowest First adhIghest Faille NI Fairly wIdespread below hIgh shore. Wthtcest, vegetation has controlled the trapping of sand, are by the sand consists of ostracode shels of the family Cy- part of Fallon formation, lak, i altitude locally Mrem than 3 ft, in alluvial channels, deltav, directly overlying Toyeb about 3,94f and where high-shore zone tranagresses dunes; far the most prevalent These include U-shaped, prididae, which make up driftsa few inches high in soil lake snd, sit, ef - elsewhere generallyIew than 3 ft andlocally absent; ad minor lake rvel offshore deposits thickest, commonly 2 to 4, rarely V-shaped, Y-shaped, parabolic, and most longitudinal the lee of wind-eroded ostraoode-bearing clay of the tufs, andvolc aub;also 6 it near Carson Lake, Stillwater Slough, and dunes. They form where wind directions vary through Sehoo formation (Russell, 1889, p. 289). Crossbed- coeval alluvial and II. aoutbeastern Stillwater quadrangle. In high-shore an appreciable are, and are oriented in the result- ding is characteristic ~Fenesidebeauty; of North zone, at about 3,648-3,940 ft, mainly fe n I in the lowlands, owing to dune Turupah It sees 29 33 medium sand, ailty sand, and ailt, local elay, rarely iant direction, the open end of the U facing into the development, but commonly is absent in the highlands. 34, and35, T. 18 N., iR 3d fine-pebbly sand and fine gravel; commoniy some. wind (the opposite E at altitude of about what sallne and alkaline. Below 3,930 ft mostly of barchans); they are essen- The sand is cemented locally by calcium carbonate or 3,448 ft. Lake andof the lake silt and clay, medium gry-brown to dark tially nonmigratory. Variants range from broad other salts, either deposited by efilorescence along the unit here overlies eotiln brown-gray and black. East of Sgoguepefault forms (parabolic dunes) to narrow ones that are much shores of the lakes of Fallon time, or from mineralized mnd of Turupah forms- sore, aoutb of Indian Lakes, and in Stiliater tion and clay of 8ehboo 1aM-S'tilfwater Slough ares generally Is day and elongated in the resultant wind direction (longitudinal ground water (as on the northeast slope of Simpson formation and Is overlain silty clay, very drrk gray-bro-n (about IOY/ 3/2) by cofbn sand of Fallon to black, tough, and commonly containing small dunes). This is the sole class of dunes in most of the Pass). formation, vhite gypsum segre6atlone; nerr 8tlle er Slough interior of the Carson Desert proper, where present- 'Wind erosion features.-The deflation basins and this clay commonly baa one or two volcanic-ash day winds vary partings, 31to 3 Is. thick; a fIIrly persitent basal through at least 200° of arc, from plains inherited from Turupah time were further de- one, pale gray to nearly black; and one more dit- north-northenst to south-southeasL Here they are pre- flited in Fallon time, but the distribution of Fallon lake contInuous, within 3 In. of top of unit, light gray, _ ~~~~~~~~~~~~~~~~pinkishgray, tan, to nearly white. Alluvial sand dominantly longitudinal dunes; their subparallel and eolian sediments within and about these features = ~~~~~~~~~~~~~~~~~occursIn remnanta of severalformer river rhannela ridges, oriented N. 701-85, E. (mostly N. 75-42' E.), shows that the younger deflation wias minor compared Mcoenetlewith the deltas, In the northwest quarter are dominant landscape features, .i of t brson Lake and the northeast quarter o F Uaon commonly extending with the older. Yardangs and ventifacts of Fallon age quadrangles; medium to coarsesand, commonbl unbroken for I mile, and rarely several miles. That occur locally, mostly in the western lowlands, where somewhat webbly (pebbles to about X to I I. di ameter). Blustra tratidrsmEbe sections are; these dunes have been virtually fixed in their present wind erosion of unconsolidated sediments has been espe- 18, 22b, 24, 28, 29 31, 35, and 3, (table 10). positions for several thousand years is shown by shore- cially severe. B'lgb horeline Is only locally well marked by deltas, terraces, and small ban; altitude 3,94S_3 ft; lines and shore deposits of the older Fallon lakes Strongly deflated areas commonly have local deposits no lower *horelines. Three sandy high-shoredeltas, against them, wherever they are at the altitudes of the practIcally continuous and probably approsimatel of Ing gravel, but true desert pavement is rare in the coeval: one in see. 26, 27, 34, 35, T. 18 .5.28 high levels of these lakes lowlands owing to the scarcity of gravel. Generally and as. 3 and 4. T. 17 N., R5'28 E.; another In Psammogenic dunes develop when sand surfaces sees.8, 18, and 19, T 18 N, R. 29 E. anolher in most or all of the lag gravel is tufa. This lag gravel is aeeas9 and 16, T. 18 N., I. 29 E. 8 ndy shore themselves trap more sand, and include barchans and the residue after wind removal of fine overlying sedi- terraces border dunes and deflation baains, most transverse dunes. Such dusses are migratory and char- prominent In dunes west of Bunelug and Lahontan ments, and differs from that associated wvith the stronger fountains and bordering Turupab Flat. Rare acterize the few belts of most active eolian sand trans- soils such as the Toyeh and Churchill soils; the latter amail bars of fine gravel and pebbly gravel at port and deposition, notably the 2-mile-wide belt along B-LIne Reservoir, borderls Bau Flats, and along typo originated from soil-forming processes and in- the soutln edge of Carson Sink east of the Carson River. north edge of Lahontan 11ountins. High Shore- variably overlies a vesicular soil horizon. line almost reaches lowest part of divide between Here the dune axes are oriented N. 800 E., the result- Turupab Flat and Elghtmte Flat, hut lake ap- parently dId not overflow the divide faithough a ant wind direction. littlb water may have secpe Ibrough); the divide Windshadow dunes occur locally where sand is wasblocked by dunes of Turapab ate, no overflow Alluvium of the Fallon formation is of two types, trapped by natural declivities. In the lowlands these channel crosse It, and Elghtmllo Flat lacks the very different in occurrence and lithology: alluvium of _3,948-ft shoreline. typically are the lea slopes of fault scarps, deflation the highland washes, basins, stream valleys, and hills. Steep windward- which occurs largely in the high- facing slopes locally have trapped some eolian sond lands and is mainly gravel and Sand; and alluvium of the Carson River, which is restricted to the lowlands the highlands the chief deposits are in the saddles drifts characterize areas of moderate deposition, and (for example, at Rattlesnake Hill and Wildcat scarp west of the Bunejug Mountains). and is mainly sand and silt. e sands of the Sehoo and Wyemahs formations dunes those of strong deposition. Dunes arebest devel- At the edges of the lowlands and in the highlands Alluvial gravce and sand oJf Me AfgMand wsaash- rxtensively exposed and into which the wind is oped-albeit discontinuously-in the Carson Desert _f the dune axes commonly diverge from the prevailing Alluvial gravel and sand of the Fallon formation under- elled. The higher mountains in the map are gen- proper west of the Stillwater LAkes and the farming east-northeast orientation in the interior of the Carson lies the post-Lake Lalnontan channels, flood plains, and yare free of this sand, but a few miles to the area; they also border Base Flats, Eightmile Flat, and Desert due to orographic deflection of wind currents. alluvial fans of tle highland washes. In the mountains i they are extensively inundatedl by it, as at the the west side of Turupah -1 Flat In these areas the LitAology-This eolian Sand is mostly fine and fine- and higher parts of the piedmonts these washes are dunes sand Mountains. are commonly 20 to 30 feet high and rarely as, _4 medium sand but locally, in the lowlands, contains incised 10 to ,30 feet, locally 6o feet, below the final ter- orphology.-Eolian sand of even the older parts much as 50 feet high. In the highlsnds sand driiti considerable medium and coarse sand and even some races of Lake Lahontan, and have narrow flood plains. a Fallon formation is so young that original prevail; well-developed mor- dunes occur only locally in pass grit ('A to I mile southeast of Salt Wells, Battleground The incised reaches die out dowvnward near an altitude gic features are largely preserved. Dunes and areas of mnximum sand transport, such as Simpson Point, and elsewhere along the south border of Carson of 4,100 feet, and the -ashes liave built sanil alluvial features have remained constant in type and Pass Wyemnaia Valley, and the pass between Rein. I Sink). Mechanical analyses of typical coarse occur- fans where they debouch upon the lower piedmont tation and have migrated only locally. Saed bow Mountain and the Stillwater Range. rences show two distinct maximums, one in the fine or slopes. Washes draining the Stillwater, Cocoon,Desert,

a in .1

..i- ml.

:80 LANZ LATSONTAX:GEOLOGY, CARBON DESERT, NEV. QUATERNARY IWRA-IGRAPgr 87 and Dead Camel Mountains have the largest post-lAke of Rattlesnake Hill, and is shaped like a broad ragged older ones; also the lake deposits and shore features crenulate, particularly where the lakes flooded dune Lahontan fans. -fan; itextends southeastward and eastward toward Car- are successively thinner and weaker. Even the older areas. The shores of the younger lakes generally are The alluvium of highland washes resembles that of son Lake and Stillwater Slough, and eastward epd stronger shorelines can be identified only locally by the most irregular, for they lie more in dune areas and late Sehoo-Indian Lakes age in the Indian Lakes northeastward beyond RattlesnakeHill to the Still;Aier mappable deposits or definite landforms (pIs.2, 11 and are least smoothed out by shore erosion (figs. 33,34). formation (p. 71), except that the former typically is Lakes. The other part lies along the present course of table 7). In only a few places are these older shore- Osoehore deposits.-Offshore sediments of individual somewhat finer. From geomorphic and stratigraphic the river northward to Carson Sink and is relatively lines deformed by faulting and warping. lake units are thin discontinuous beds of silt, silty clay, relations, it can be subdivided locally into lower and narrow and extremely irregular. In places in the * Deltes of the Caroren River.-The Carson River built and clay in light to dark shades of tan-gray, gry-tan, upper parts, that may be roughly correlative with the southern part, small erosional remnants of older depo- a series of deltas on the west sides of the Fallon lakes; brown, and black. Their prevailing tan or brown tint loweraikduppermembersoftheFallon. Ingeneral,the sits rise above the modern flood plain. The depth of they were generally graded to the high shores. The distinguishes them from clay of the Sehoo formation, lower part is thicker, somewhat coarser, and extends dissection below the tops of these remnants decreases deltas range in gradient from 5 feet per mile east of Fal- which generally is greenish gray. They are commonly farther from the mountains than the upper part. The downstream, from about 10 feet at an altitude of 3,970 lon to less than I foot per mile in the lowest parts of the 2 to 4 feet thick on deltas, but elsewhere range from a most recent deposits have few large boulders. Drift feet, about 4 feet at 3,950 feet, to none below 3,920 feet. basin; they do not have recognizable topset, foreset, and knife edge to rarely more than I or 2 feet in thickness. sand has locally encroached upon the earlier wash chan. The northern extension of the flood plain is 0.1 to *: bottomset beds. The highest. shorelines generally are The Carson Lake and Stillwater Lakes areas were nels, partly or entirely blocking them (for example, in 1.2 miles wide and is entrenched 12 to 15 feet below the poorly marked and the subaerial parts of the deltas perennial sumps, and in their lowrer parts the Fallon the saddle between the Stillwater Range and Rainbow surface of the west delta of the late Sehoo lake as far grade imperceptibly into the sublacustrine parts. Sub- formation is almost entirely lake sediments, several feet Mountain, in the Simpson Pass sres, and along Diamond downstream as the main Sagouspe swarp. Below this lacustrine distributary channels commonly are prom- to locally more than 10 feet thick. Field Jack Wash south of Bnss Flats). warp it widens to more than 1 mile in a reach graded inent, in some cases extending I mile or more from the Although Carson Sink is now the lowest part of the Alluvial sand and silt of the Carson River (Recent to a smail high-shore delta of the third Fallon lake at shoreline (pi. 11). Typically they are very low ridges basin, it contains almost no lake sediments of Fallon flood plain).-Alluvium of the Fallon formation depo- an altitude of about 3,915 feet. Farther downstream (whereas subaerial channels generally lie slightly below age except at the mouth of the Carson River. This 'r sited by the Carson River forms the Recent flood plain, the flood plain spreads even more widely, commonly 2 the flood plain) and have widened, blunted ends. probably is because the river rarely drained directly to This alluvium is lRrgelv silt and some interbedded clay miles or more, in areas interlaced through dunes of The deltaic sediments are the most distinctive and the sink during Fallon time; also, any lake sediments and fine sand interlaced with narrow stringers of sand Turupah and Fallon age and erosional remnants of thickest shore deposits. They are mostly lake sand that were deposited tended to be removed by deflation. and pebbly sand that represent bed deposits in former Sehoo formation. The alluviui exposed here isof late associated with some silt and clay, and contain alluvial rosarLS channels of the river. It has the intricate structure and Fallon age and is aggraded to deltas at altitudes of sand in distributary channels. They are heterogeneous heterogeneous lithology chnracteristic of such deposits. about 3,905, 3,885, and 3,875-3,880 feet; the lowest is at in lithology and structure yet monotonous in general First Fallonta ke time.-Four mollusk collections The main channel fillings near Fallon are 100 to 400 the mouth of the river on the south edge of Carson Sink. aspect, having few marker horizons. The distributary from lake sediments of the first Fallon Lake unit, feet wide, 10 to 20 feet thick, and mostly pebbly coarse channels are mainly fine-gravelly coarse-to-medium determined by Joseph P. E. Morrison, U.S. Geological to medium sand, having pebbles commonly half an inch COLLUvIVnI sand at the lake margins, grading to fine and medium Survey, contained the species listed in table 6. All these and rarely I inch in diameter. Severnl miles farther Colluvium of the Fallon formation is far too thin sand offshore; commonly their sublacustrine parts have species are aquatic and are still living in the Lake downstream the main channels have mostly medium and local to be mapped. It is mostly slope-wash mantle, natural levees of finer sand, grading outward to fine Lahontan region. sand and some coarse sand containing a few pebbles, derived by reworking of older creep mantle. Promin- 1 I. sand, silt, and local clay in interchannel areas. The "82-inch midden" layer in Hidden Cave (unit 5 mostly under 4 inch and rarely ½ inch in diameter. ent among the deposits are torrent levees along rill f Other shore deposits and features.-Away from the in section 39, table 10), probably correlative with the The pebbles are granitic and gneissic rocks from the channels on steep slopes; these levees consist of jumbles I.I deltas the shore deposits and shore features generally first Fallon lake unit, yielded plant, mammal, and bird Sierra Nevada and volcanic rocks from this and other of blocks I or 2 feet, locally 5 feet or more, thick. Lay- fossils. Most of this material probably was brought in II.' are so subdued that close study is needed to identify highlands. Low natural levees border the channels in ern of slope wash aeminterbedded with loess and midden I them. Only the highest shorelines can be identified, by Indians living in the cave. The mammal bones were places. The channel sands commonly can be traced deposits in Hidden Cave (section 39, table 10) and other t with one or two exceptions. Shore sediments are identified by S. B. Benson and staff, Museum of Verte- downstream into deltaic sediments of particular lakes of caves. mostly medium and fine sand, commonly quite silty, brate Zoology, Uni-ersity of California, Berkeley, who Fallon age. Most of the exposed interchnnnel allurium i. II locally silt and clay, and rarely (near the mountains) found the bones of one man (Ifomo sapiens) and the is in the upper member of the Fallon formation. This LAK srD11tescra AND smione rEAruars I gravelly sand and fine gravel. Carbonized plant n atter, following: alluvium is the most fertile of the basin-interior deposits General /eaturemThe lake sediments of the Fallon mostly from tales, cattails, nud other aquatic plants, and underlies most of the farmland, formation consist of sand, silt, and clay, and minor Odseoatle A ,iss ibltcktatt or male deer.I tsdtvldastl r- and contemporaneously deposite1l titfa in small nodules gacmet. jltaveater (yettw-bilted acsraot,I ndtvtdstu1 Above the apex of the west delta of the late Sehoo lake amounts of gravel, tuft, and volcanic ash. They are or thin coatings occur locally. Xrefe,, Up. (weed reat.I Indlvtdtat) in see. 30, T. 19'N., R. 28 E., the Recent flood plain of much thinner and more restricted in distribution than i Typical shore features are shore swaths (veneers of Lepas cetlfe-c,,a (black-talted Jackrablat. 2 ladirtddal.) the Carson River lies in a valley half a mile wide those of the Lahontan Valley group, and shore features reworked or newly introduced sand or sandy silt), shore Ryt U. ep. te,,ttoetall or ptglr r.bbtt. I IsdMxIdtld trenched 100 feet below the top of the middle Sehoo associated with them are much less conspicuous. The terraces against dunes or scarps of unconsolidated sedi- The plant remains from this bed, identified by H. L delta at Lnhontan Dam and 20 feet below this surface Fallon lakes vere relatively shallow (20 to 85 feet maxi- ment, and rare tiny bars and spits. The swaths range 9 miles airline below the dam. Fire miles aest of Fal- mum depth), small, and fleeting, having only feeble Mason, Annetta Carter, H. K. Sharsmith, Isabel in width from a few feet to several hundred feet, the Tavares, and Calen Smith, Department of Botany, Uni- Ion the flood plain is only 10 to 15 feet below the west wave action and longshore drift. The deposi,'and terraces from a few feet to 50 feet, and the bars from 20 versity of Californin, Berkeley, included the following late Sehoo delta, and here it starts to fan out through shore features along the highest shoreline of each lake to 100 feet, being generally only 2 or 3 feet, rarely 5 feet, in approximate order of abundance: an are of nearly 120' along a series of former channels are most conspicuous; transgressive and regressive high. The older likes built thicker shore deposits and (pl. 11). shorelines are little in evidence. Each lake was carved more conspicuous shore features than the Sesrp.. sP. I utle,predominanlt) the entrenched eec- shallower than its predecessor, so these high shores form TpPEa op. elstatll) The broadened flood plain below younger ones. Shores are smooth and unembnyed in Elce-hrlsstp o-Jeae.,sp. t(rubt tionaisin twoparts. Tle main,southiern,partliessouth a concentric series, the younger shorelines inside the some areas but commonly are very irregular, even PSr-otltes up. (ease) QUATERNARY STRATIGRAPHY 89 LAXE I.AHONTA2L: GEOLOGY, CARISONDESERT, NEVY.

I EXPLANATION

Ofou 1

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01.,. Ole,. tat. od flo-aly - ' .iit) .04 lob. r Ofsu. fake #.u.d uJ pper .,e.,Ar (rtog loake.. nd '- Ilk ,lo o ..,d (0.) *..4i.,tIl. , 0..11" Ml j,tceIokr 0,4 tAhf Loike%"it#. r..bi~ed). :oh.7o ... ""M., .Of..dof I..d foift G.1... .it ak Oft.u. take silt a..d cloayof ppt,. o.,..As. Qf... O .,. of.11-W .oodt and g-o..e umo., aill, al .04th. gyp, f- Ia. oo-.u l.. .04 i'wlk.A. .it. I Of OtA.. Qfa,.aW. .od ..d,,...l ((I.. er.. I. p.bAly **- typ e ..elber a.iedqs~oe ... d Lake.oil. -.ap deiw~lyI. -..d). .0 , 01 01. o IS. th l, .4l. ' .o o t; t.-. ll Ofe.. eoi.. ..,d of oppe. -.u.Lo,, Woally with ir.- .4 .a.d l .o ..0 os....- W u.by . 0.01. -. d~io Ai dA..A. Woddd LIk. 4 DISCONFOR~otTV dt l. ..hil. .1 , . S gp . M ~i.4 z Otto fg, 0 -] Fall,, a..it S '01... .11W~l o . .f. d dl. -..ta i. elt o...flf.7 0, I. 0 \ 7./-

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LAX WAMMAT3: "000T, CaMMa wI,U II. I., moTRUCaTUPRATMIA OF AMimUTM TAUT AD AIWAr A" 91

Orrespelf AgoomwAmfe(ie Afft~ew~e tesemheu~) in development 41utW ditent JOW ORvfeMme-- TM profi t the lDrao n soil Iwk compae ?eeismmlhe-I tWtibstsas) VW'"d as. (seUs) --. I pareL maial, drngs, alops, &adaslinlty-o.- wth ah Te sl, biu srag tanl in soil of late 55mm. 3alis0iM ("01isIs pesbea emot) jiek Le. Itlawsi)* - '4 mal are greeter then differesase du to age. Then Fallen age. A- m orsaftaiuna-Fjm gaj os s c..slati mil therefore do o especially id in subdividing and The %ppera t i tShe P~aple ')-s ; . i affiir e o poniae in tlimGray Aftemise m (emtaesei) ban~ Iske sadimetiabof th third lOUakeuntWer deter. nrliat ti pare of the foemtion Demsst fad.iensi incipiently developed vesicular hod. jelwO smined by Joseph P. E. MaYiac., UAL Geological D,,Which Is lihtgay (about17 7/) e" ha Sbusa"L Emeoteuaa '&&my, " om i'esth ssewrt in tabe e A 55*e(wls) - __ . '''_"g weak Vesiclar 1* Week grelar( ad locally faing to Oa shel, peiMy Aisdmad. W-ionai-, at we natl and an still ling in the Lake The LAeela soil is of middle Fllc age, apprem- weak ares columna stiauu. Tete tar;esfost mum,. _:. . i . L: ...... lo,ma e gio. The pelacypod Auod.* eeli/.e -* seeal with the second imerlake u0 On pv loamy ato lane- -Andy Loa t slt, ead amnsiste _Ma False wa sis-sizg ollusk ook - b particularly abudat alosg lieg shore of Fall depoelt it is meshed by the strone Toys aill gemerallylsoligyle"had Timebassefthelsordaogen. mlalimeaf th mmdtiele third unit, detemi Fallen lahein time Caron Lke ua. excet wheta eel! werdld por to ide FeLon wary I abrupt, but les sothn that dtTsh sa Joeph P. L. Meorion, US Geological Survey, n- Le Fall.. sine-Molluk ohe teed to be _ancs. 4 the. iprmany k ie a very weakly developed Grey TimibackdoaeeiseentAisthe Sol sehk faCe" medthe dalan.sd nsails liated in table L. Thes tint mostly Alngi time bigheshore aseas of time fourth 'I Deset sil, but in poorly drainedseline locations it W soi lacks true asie Nd calcrou iorlacas, o an in aquatic nd ma still living in th(l, and Utif Fallon lnk b ut in places anmdisrbutsd over grades to a very weekly developed 8olonchk soiL though vey alig oide illuviateo in th upper put Mentan legion, eacpt pomaibly Cigecia,saa et C. th lake bottom. They aue mostly concentmated in iao Thetype loclity i the s of ol profl MS (tab an ve IgA calcium carbonate daecmulation in the teg _W PIbS O i; et ¢. I ted grope of aimilar individuals. Ln order of 11), in the drainage canal kno " the '" Drain, lower p"a ae locallybeint The main evidence of hes top mies l4aye in Iliddun 0ave (auki 2 in decreasaing abundance they aau: AHeliessm aS. cell just wat of the northwest corner of th Falle Auxil. soil devlopnne" iawcolo ange. MMNois brw Ice 10 tabl 10), probably correlative with the me- I-Anarse fusifoe gastruodsol, Anodesmds oealif-ir- gryNaval Air tation (u of 1S50), When the sol I to gra ih ba (IOYR / to ") to a depth of 10 I Felioe lake unit, yielded borne of tim following da, & p ,mvlu. Nineteen jolletiona of slict %pon alluvial send in a distributry chanel in to 16 inchs, and grades through a diffuse iregelar ebraes, ahW idifid by S. B. B _e" -' ff mdlufmMtyu a lnterlkntdud- thedeItof the Bnt Fanon (ik Sl). boundary into lighter coloed perest mail Stm veraity of Califo1-a. 'IRg thee from modern dants, wen determined by twe Is weak coare griuslar to ainge grain, and * ~(ha~l~j1 ~ -~ ~ Joseph P. Y.1orison,U.& Geological Surrey, as the miet""c is gallgt hard to sof aSd Nearly Icons w S ' ' R'.".- -, o0fse es'sfeaks e"dats Maes.i"MAsemi "" 0"W ) species lited in table 6. AUll specie are aquatic, 410 OW11M te&S" A" Lom.w seumah t(blac}ulsi jacktehbit C Sa01mle) end all still live in the Lake lehonten region, except Ieadi MR" (ter, I l"vidai) Anmigr aifs and Lymma.. ofagPali& Both thee elic adoil th third ladUn tof he Fallen far aemssame tembs (letel or mam _er. I 1i1te) holauctic apaie indicate northen relations of their mati Islcharacterized by slightly mer brownish colr * s4smn'E@_ heez^,tiliim) 'a _h amT tim motlenm recod, lIbm or then the pa Material, Nd also by alig inderatlon _deseesi.as e.eaw( ' Painom.ofArni, riste inNothAime. It a and development of a very weakly granular structure Psmssssswhltdsteimesse I Iiivlilrihing from to to mootier. Indiana to to deptlefs of a totioes uSIilS mdisona " d bones, mified by H11deagarde Hloed, a r et t ee weakly differeuleied. So danlopment on the 4t gulCee outyMae ,L Amules,Cal& included:., fourh ad fith Fae lakes, rpectively, er the louing lake WAnWarlieask uit gaot disosenibe, ysmawloseS I ergsdasis m vts..mdud south margin of Canoe Sink, wr identified by N. H. STRIXT1111. PRAMUM Of LABONIN VAUNT AMl trer aftused emu) Dmj,, U& Nativead Muse , us a *almom fi , P- w u Asedwerpleme selemideta. (uswele pete, I Whidvles) PAUL"s A" De~elsa~lsd del eithlerMabef.eivaap. or aos. s., !b ea ui dr c ti ns ma n f r s -wt e r mu ml sh l s Jeons OF SAMTOA"E Siebly Anedeeos cali-u&eka; it also yielded onae" naxmnan inavunna tiesd to the preet, This late deecatlo Is" been I leard verltebas, both unidentfied, and inet elder sedimenit of the Falc formation hear lagl in the be . the hg simerend of th EA g, probably Cypier six Plnt r ihs from tbii week, though disint, eOi Ganerally th mGlean ealy 15ei140, an middle sli lakes samW dvod of er, identified by K L Matee and stag, University relIc, recording all sil developeent rom the tim the sinfcnhalig or warping awr in temP Califoia,Berkeley, Included (in aproalnte eoder sediment Was laid aown toathe preussn; burie soils ase 79 abundance): comparatively m. The faults at the periphery of the basins geneally IN the relictil4 the profil dvopent bacress" parallel the losal margn and BMan,NWk the WIldca Jamle" WeegteS) . with ag, being greate e the& fi n lake unit an nil fault acne (p. 91), ar eceepnaioumly arcuta.a The in m_l e rmedl m nts The p fU13t41in the Interior Of the carsn .tru?an gnefest? . PrlomieeS)ps emle tom* me inc e s ler d reg ular, how. Deser StIke norCth- P. sm tls'.'eas) ,enr; Itib ee ly p eop tibe betee thefes n as en wes through oerth to noteaff . Seena intrio faults lk uits, but ebsious between the scend and thied li"l grabens, which are bounded en the other aide, by ,05krv 5 - e t .ealan lak units Sol d p w thus W" cive peripheral faults. Many ef an larger f uits we in during th second interlake intervL The oil formed Vase UL-4,10555 madLd b a s .5 5 , m S le ee e mat~of fault - (p. 91), are conplcualy ernt. T Itoutso . lWeisl during this interval la called the L-Drn soil; It l the rew aa. *NW,)of amha ammof rlsenalm-ad. ST"2 to a kaw fa, raely more than 2 feat, but s"eval faul A.rew i.-w 4sh. imea-, only soil of Felice ag wel enough developed to meri seow hd udm, Seine.. mat. TM hoIfseWi mat mimam nones aexsItend12 mhles. The faul trame are regaly formal designation. xliposed, being geerally buried by younger dposits. POW- S&(vswod L am.T. aseK. IL soU. sale Samemmuafi - Peak Issaebasm ls~meei(a The soils of Fallon age onro weak that diferenom -a sam Th rg and mor reant faul here prominent mo64 . I.nor ......

LAKE LAHONTAN: GEOLOGY, CARSON DESERT, NEV. STRUCTVRAL FEATURES OF LAHONTAN VALLEY AND FALLONAGE 93 the east edge of Eightmile Flat are two large and sev- generally are much modified by I(north of the Desert Mountains), to about due west named from the Sagouspe diversion dam and anal, carps, but even these eral small northwestward-trending faults that displace ater erosion and sedimentation. The faults are shown Ithong the north edge of the White Throne Mountains, and is marked by a scaro12 to feet highwi and about md through east to north long the west side ofAhe the Sehoo and Wyemaha formations I foot to several 8 miles long, extendingN. of 40f au.to within about by scarps, dislocated shorelines, abrupt changes in alti- feet. These faults seem to mainly antedate the exten- ude of beds, and springs and seeps (including deposits 1Bunejug Mountains, to about N. 10° W. at its northeast cn miles of UpsnI Hogback sne faults are genernlts end. It is named from the Wildeat freight station of sive deflation of this flat in Turupah time, but they concealed by younger eoliansand and lake sedimentsh of spring sinter and tufa). Most of these features genmI were sites of minor surface breakage during the July 6, irally are better seen on aerial photographs than on the pioneer days, south of Carson Lake. A prominent but somf e zpoorn exposed on the cay flatoat the north scarp, named Wildcat scarp, which is mainly of the 1954, earthquake. The low ridge separating Eightmile end of tha oe foThe most detaled information, hoa- ground. and Turupah Flats is a horst defined by several small The more important faults active in Lahontan Valley Sehoo formation, marks the zone; it ranges in height emer, has come from the Sagouspe irrigation canal, I from several feet at either end to 55 feet in its central northward- and northeastward-trending faults. On mile east-northeast of Sngouspe Damn Three of the knd Fallon time are discussed below. Magnetometer the west side of Eightmile Flat are at least a dozen very ind well data suggest that many, particularly the mar- part The scarp rises abruptly from the nearly level faults are exposed in the csnal bed and two others hped Carson Lake plain, which has a drop of only 6 to 10 small faults of similar trend that displace the Sehoo. been located by boreholest, theral aor don ndropped final faults, may be associated with larger buried faults 5 Many of them are fissurelike cracks of only a few Afpost-Bunejug pre-Pariute age. feet in the h to 2 miles from the scarp to the present def feet on the northeast, the others on the southwest, shore of Carson IAke. Detailed mapping of the Fallon inches displacement, of which only the largest were defining two fmall gribens and two horsts (figr 3f showe FRE-SEHOO FAULTS and older units along the scarp (shown partly in fig. 36 mapped; several saline seeps issue from the larger ones. foTr of the failts in the seuthwestern part of tore zone)i At the south margin of Fightmile Flat is a west-north- and pi. 12) indicates that shore erosion by the Fallon Tfre main displacement seems to be of teor more in- Three pre-Sehoo faults are exposed in the Carson westwaird-trending fault zone containing two main Lake quadrangle: two in a gravel pit southwest of lakes did not initially form the scarp-it merely caused ferred faults on the northeast edge of the zone, ef- some modification and retreat of the warp secondarily faults that have been traced for 3% miles. They have BM 3949 at tie northwest prong of the Bunejug Moun- a total displacement of about 25 feet, down on the basin fecting at least 10 feet net displacement that is doaeon tains, and another on the ridge 21/4miles south of the after faulting. The stratigraphy of the Fallon forma- the northeas thealhifaultso em tobeof thep ime age; tion side; their swarps are almost completely mantled by same bench mark. The third is exposed in the gravel at Bass Flats and along the scarp northwest of they postdate t elarlykitlioidtufaoftieupperhe anemoer these flats reveals two principal episodes of post-Sehoo eolian sand. Rock Springs may issue from a buried pit shown in the southeast corner of the Fallon quad- of the Schoo formation and predate the lake sand of this faulting, during the first and second Fallon interlake fault in this zone. This fault zone intersects at a right rangle. All are vertical faults of a few feet displace- member,ehic fiawedthe fault trhbensl Evidently the intervals, respectively. The faults are nowhere ex- angle with a northward-trending zone at the west mar- ment that cut the Eetza formation but not the overlying gin of Fourmile Flat. The overall pattern of the fault. late SeCron Ietive was barely at this level, however, and Sehoo; all are downthrown on the basin sides. posed, but several are inferred from springs and seeps, from local evidence of displacement of Sehoo forma- ing shows that the entire Eightmile Flat-Fourmile Flat the Corsoec River as flowing approximateny its present There is indirect evidence of pre.Seboo faulting in area was downfaulted in post-Sehou time, Eightmile course, because the sand contains many small pebbles several places along the margins of Salt Wells Basin. tion, from exposures of this formation on both sides of the faults, and from local secondary scarps (demon- Flat was tilted slightly to the southeast, and Fourmile similar to those in tv e bed of the Carsond iver todayt On the pediment east of the Bunejug Mountains and Flat was the most depressed, particularly the salt flat Probably the rivermas temporarilymito diverted the north of the Cocoon Mountains are ninny siliceous- strably not caused by shore erosion). For example, the in its central part. graToes, filling thema ith sedimentz sinter-cemented remnants of eolian sand of the Wiye- easternmost fault near the north end of the main mass of Bunejug Mountains displaces the Sehoo about 5 feet To the southeast this fault zone passes beneath the maha formation (fig. 128), generally alined with faults SACOUSPE FAULT rONS in the bedrock of the pediment. The opal cemett was down on the west. Some of these faults lie close to the Carson River flood pT.in but it is know9 to extend at The Sagouspe fault zone is the largest of the post- deposited from water rising along the faults, but the main scarp, others a quarter of a mile or more basin- least into see. 26, T. 19 X., R. 29 E., associated with Sehoo faults in the interior of the Carson Desert. It is orifices became closed during Sehoo time and the 'ward from it. More exact differentiation of these small-scale grabens and horsts as at the Sagouspe canal, springs now are extinct. On the west margin of faults and their displacements must await better Four- EXPLANATION mile Flat, 2 miles north and immediately east of the subsurface data. southeast corner of the Carson Lake quadrangle, eolian OThR -AROINAL rAULTSr I.E sand of the W)emaha lodged against a steep scarp that probably was due to pre-Sehoo faulting. This scarp On the piedmonts north of the Desert Mountains and has been accentuated by minor post-Schnoo faulting. east of the Dead Camel ,Mountains is a series of en echelon arcuate marginal faults that is essentially a Considerable faulting took place in Wyemaha time widened continuation of the Wildcat fault Eone. These near Upsal llogback. Only the more important faults faults partly control the long ladland escarpment east are mapped, and generally the displacement of their of the Dead Camel Mountains (though this escarpment exposed parts followed the voleanism; notable is the ED~ 5-- is mainly -eI probable horst extending several miles southward from erosional, probably by deflation). Post- Upsal llogback (later buried by Sehoo formation, then Sehoo displacements range from a few inches to a few partly exhumed by deflation in Turupah time). feet, and only the faults having the most displacement are mapped. Generally the basin sides are down- ?OST-SEHOO FAULTS dropped, but locally the mountain sides are, , WILDCAT FAULT ZONs Post-Sehoo marginal faults are especially numerous in Salt Wells Basin. An cast-west fault on the pied- The Wildcat fault zone is by far the largest of the marginal faults st the south edge of the Carson Desert. mont north of Turupah Flaf, near Salt Wells, is in- ferred froun a delosit of siliceous sinter, evidently de- It exten ls about 12 miles in a great arc around the n.nr.. 34.-F-5..tn t5,-arh .- i5,th-t- en, ur Sne9uuv. mutt oa I%tssn...., a--...ua. Kwim We. Lake, chmaging about posited about the orifice of ni extinct artesian spring, b.,te slid 9ru.1- ,ItlIfl. 1,r kltl. fntsnb -.jti 1.1t fl.ult -t, Wu -unonueOoffwt a cIt tien5. T. 15 Ii.. oatR.0c~ 5 io-tE.. .iba1ine iS foci. .n..n1i1dna. a south anid canstsides of Carson islb. t*,t rot. hoa~o.ln. 325' ili strike fromi about N. 45° V. in its vest end ceentristtg sanid ,,nt gravel of tIe Selhoo fonnation. On U-~~~~~~~

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LAKE LAItONTAN: GEOLOGY, CARSON DESERT, NEV. STRUCTURAL FEATURES OF LA]RONTAN VALLEY AND FALLON AGE 95 from boreholes and local exposures of Sehoo formation At the 'south margin of Carson Sink a low Saerp tion and flat floors of lake silt of the upper member ofcenter and VII to VIII in the Carson Desert-Lovelock in a drainage canal and in erosion remnants. trending N. 50o W., from sees. 10 to 13, T. 21 N., R. the Fallon. The Sehoo formation commonly has @a area (Cloud, 1956, p. 34, 35, 38); magnitude on the Gu- 29 E., marks a probable concealed fault. Sevo;;) bore, slight outward dip. Volcanic rock ejecta are absent, tenberg-Richter scale was reported to be &.8by the Seis- OTHER INTERI0R F AuTS holes northeast of the scarp suggest that the Wyernahs- but the basins are believed to be craters resulting frot a mological Laboratory at Pasadena (Cloud, 1956, p. 38) Post-Sehoo faults seem to be especially numerous in Sehoo contact is displaced a few feet down on the a small volcanic or gaseous explosion, not only becaus a and 6% by the Berkeley station (Seismological Soc. the Stillwater lakes area. The subdued topography of northeast. Other northwest-trending faults may un- of their peculiar form and orientation (unlike the defla - America, 1054); felt area was about 130,000 square this area consists of many low ridges and basins having derlie the dune complexes at Battleground (the penin- tion basins in the area), but also because a light-colored second main shock 0 I miles (Cloud, 1956, p. 38). The 5 to 15 feet of relief, which trend mainly N. 20°-45 E., sula just east of the river mouth) and at the next pe- bed of ashy silt (presumed to be explosion debris) itioccurred at 2:08 p.m., Pst., had about the same epicen- and, subordinately, approximately transverse to this ninsula to the east, for extensive seepage zones, possibly the young lake and interlake unit of the Fallon forman - ter, and was reported as magnitude 6%/by Pasadena trend. The basins are mostly lakes, ponds, or marshes. fed by water rising along faults, border the northeast tion (table 7) thickens toward them, and attains ittiand 61/a-ct by Berkeley. The principal aftershocks This topography is believed to reflect many small horss sides of those peninsulas. greatest thickness, more than 2 feet, at the west edge olroccurred on July 8 (2 shocks: magnitudes 5, Pasadena, and grabens which are due to post-Sehoo faulting; the A low scarp on the flood plain southwest of Fallon the southwest basin. and StA,Berkeley), July 9 (magnitude 4.7, Paasadena), whole area is virtually a foundered graben. The pre. indicates another concealed fault of Fallon age, trend- July 30 (magnitude 5%, Pasadena; 43%4,Berkley), and :. EARTItQUAKES IN HISTORIC TIME dominant trend of the topography is about 600 from ing north from sec. 34 to see. 15, T. 18 N., R.28 E. The August 2 (magnitude 51/4-5/2., Pasadena; 51/4, Berke- that of deflation basins and sand dunes in the interior scarp is mantled by eolian sand of the Fallon forma- Strong earthquake shocks were felt in the southern ley). (Data from Seistmological Soc. America, 1954.) of the Carson Desert, so it could not have been carved tion, and is dowlndropped oil the east; anid considerable part of the Carson Desert in 1873, 1916, and 1932, and The July 6 earthquakes lnd aftershocks produced by wind. Auger holes locally have proved offsets seepage, probably artesian, issues along its base. minor ones in 1930 astd 1949, bitt the epicenuters of these surface breakage about 11 miles long and N. 12° E. in of strata along the low scarps, but the fault patterns are DIsPO.ACEaMIE-r OF snoREaIES-a quakes were outside the map area. These shocks opened average trend, from U.S. Highway 50, 1* miles east of man-y earthquake cracks in restricted areas of the Car- Salt Wells, thence along the east side of Raitibow- complex. The northwest side of this foundered graben The post-Sehoo faulting has caused almost no dis- on the flat north of Wildest is vaguely defined by discontinuous scarps, several feet cernible displacement of shorelines. The Inrger faults son Desert, particularly Slnuiaitain, t hence across the fhlts to the iotltb, ending at part of Carson Sink near the to about 6 feet high, of N. 310W. to N. 60'E. individual of this age are all basinwvard from the high shore of scarp and in the southern the north side of Stillwater Point Reservoir (Tocher, mouth of the Carson River (fig. 37). - 1956). The breakage occurred either in a siigle hle or trend, aimed in a zone trending N. 20'E. from near the late Sehoo Inke, except north and northeast of the had epicenters in the map as a linear zone of breaks. For about a third of the Stillwater almost to Carson Sink. Only the two most Lnholintan Momntains, along the badland escarpment Several earthquakes that total length of the fault it showed as severe cracking east of the Dead Camel M1ounianins,stnd on the Carson area occurred in July and August 1954. On July 6 two definite of the concealed faults suggested by these scarps and no apparent displacement, but along the rensainder River delta where this shoreline getetally is obscore heavy rolling shocks occurred, 11 hours apart, separated are mapped. Here exposures and boreholes show that it formed a vertical scarp 1 to 12 inches high. The or eroded by deflation. These faults also either pre- and followed by minor tremors The first shock was at clay of the Sehoo has been downthrown several feet on west side went up relative to the east side, except ih a date or do not traisect the high shorelines of Fallon 3:13 a.m. Pacific standard time, and had an epicenter the east; traverses with anl airhorne mngnetometer also fault in the northern part of Raiibow Moun- age, except north and northeast of the Laholitan (provisional) at lat 39°23' N., long 118°32' W. (Perry secondary slioxsed anagneticaenomnly ntthe northernscarp. An- Byerly, Ditector of Seismological Stationsh University tain where the west side went dowi Ito 2 ituches; move- other fault zone limits the graben on the southeast, Mountains. In the trough northeast anid east of RainbowuoMoun- of California, Berkeley, written communication, July ment was entirely dip slip. The faulting along Rnin- mainly east of the map area. Extensive surface break. tain the middle awid late Sehoo high shorelines ore 22, 1954); its intensity rating (estimated, modified bow Mountain apparently followed earlier faults in the age from the earthquake of Aug. 23, 1914, followed dosvndi-opped About 15 feet. The high shorelines of Mercalli Intensity Scale of 1931) was IX at the epi- bedrock, partly those separatitug the basalt and dacite of small concealed fault in it is mapped this zone and one the first sand possibly the second Fallot lakes also may Ratibow Mountain and the Truckee formation, and just east of Freeman Pontd. le downdropped several feet her-e, bitt these shorelines I partly within the Trackee formation. Descriptions of The Stillwiater Lnaies fault zone seems to extend are poorly marked. North of the Lnaloitan Mounttains the ground breakage, property damage, intensity dis- the Carson Luke aren, although southwvestward into the high shorelinue of the first Fallot lake appears un- tribution and strong-motion seismograph results for the young sediments in this port of the basin have con- I.21 deformed, but that of the second Fallon lake, %to 2 these quakes and those of August 23, 1954, have been cenled most evidence of fatlting. Buried faults trend. 11 miles farther basinwvard, is tilted, fromnan altitude of 1- published by Tocher (1956), Steinbrugge astd Moran northeast, are suggested by local seeps, a ing mainly about 3,930 feet north of Ectua Mountain to about 3,920 (1956), and Cloud (1956). The greatest concentra- subdied l northeast wnrd-t rending topographic liearity, il feet north of Raiilnbow Mountaini. No faults associated 4 tion of severe damage to buildings, canals, and paved several lowr sewrps within I or 2 miles of either side I, with the tilting have been identified. highways in the Carson Desert proper is in a northeast- of Stillwnter Slouigh, and small faults and numerous 4 ward-trending zone about 6 miles wide that passes large cr-iks developed by the earthquakes of July. POSSIBLE EXPLOSION CRATERS OF LATE FALLON AGE thence about half way between NEAR STILLWATER LAKES V through Stillvater, August 1954. The northsvest edge of this zone Fallon and the north edge of Carson Lnke, to the Lone semis to follow alpproximnately the 3,940-foot contotr Northwest of Stillwiater Lakes, in the Wa/hsee. 29, T. I Tree School (Tocier, 195G). This damage probably lite southeast of Fallon, passing several miles north of 21 N., R. 31 E., are two cotunected basins arranged like was due largely to heaving and lurching because of has Carson Laike. That the Carson Lake area itself the southwest and northwest quadrants of a circle, the unstable layers in the Quiaternary fill of this area: been dowifaulted or donwnarped in post-Sehoo time northeast one almost circular and 800 feet in diameter, I!- 5,a- n 31 .-ro mYt n.. aa i,t onS. n- k.S in ,oni ,rn Cc. ,- ink. nevertheless the linenr thistribiution coiilrides with the . uin _.a at ma is sllggtsIel by tile nbrupt thickeliing of post-Sehoo and the southwrest one elouigate, 2,000 feet long aid 1,000 50 5 n-Ao . a- n, io-.5 7 in ,n.y at s abna t a, --lb, at ii,. C-r-,n Sill,. T -o " -fl 1-ii, -a b. -o Tb. soutiwiarild extension of t lie St illwiit-r lI kes fault zute dovitward dlislilaeement W sediments earnrthe late anid by feet wide. Both have 10- to 25-foot rims of clny of the y 0000 I tr i ,, *n. tf ,d by n, Onm..a iS, ntihq n.k , o (p. 94) ald imight be lie to millor reait ivi3tioll of this of the clay of the Sehoo formation. i:. .1,y isis. hd.- re n an .,. -n~v ,,s. y.,. S.sIr" I ...ob Sehoo, capped by Inlke sedimeits of the FnIlon forms- I, a -' n I. sI-.i , m ,. ,Id.. an-. a3.T. 22 N.. a. as IC. zone by the qttiikes. A geologist who checked grouinxd f- -ck

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4.I. -*1 1- 97 tal LAHONMAX? OGoAnWT, cLAAes XDBZ, )31. : toer hi intb Eme*jug and Cco MutisOmeCepe- u*plited This uplift peshably started in the urbance in t. ame hetwesa end after the two main Begianing during the later past of th 140tic glnws ranecusy muckigh-engle normal faulting took place. early Pesome, Nd by late mdl Pweistec time ocks of July 6 (Norman Silberling, orsteommiuaio- probably in eary Pliocene time, the Trucee formation W depoelted its pakovsvrphy is little This faulting cated bew highlands amnba and th the Great Dem bed rise 8,N tO &A0 fbut i shut m 19) noted that msat of the grsoa-distruzbamce ral outline of the present topography be to is pneent nv ltte (Blckedar, 194, p. I tturs is th Stillwater-Lone The toe originated kneow but the wel4tek part of the Or" Basint p-6 although the local nelie was slh Some - W1; Ferguson, uerw, and Cath t, 15J, 194"). ithest sho but damp to U.S. ighway 60 ably ws th at lest two or the tLhouad feet lower be dalnd, the now, thloakW lie ay have been Ien and me ighleands were upliftedately earlyeand much jajor Mock flt acceepenied the uplit The Sof MIt the sOd t Wefls i darlop Until to the _ea (Azelrnd, erded before the Bmmijng formstion was deposied, P-ipal dieamant ea1red during t_ diseases EpicLnte da tao genereliaed to how. a probably mtil drained so tht in Place a marked angular un formit of faultng that were e nd foU b in- the epicaster of the Sit shockck U"actaly in 1380 P. F S ; V. P. 01iana, oram, Thi fautig 1s4). Te fmil oend fauna w tt thedimat separate the Trucee and Beuuejug. la tIe WMite tervals of rlative detrctl qulecas Stillwater-Lome Tem sove an that of the second is ierred to hne further de d d pift bloc"s the eat ad Ra inbw Mountain, bust this i a was semiarid temperate (AJevod, I530; Chanesy. lo3; Nolan, 1411, p. 169), hainbg changed from4the worm fstef local reliefwssevlopedL In "thinteor. f the tat previously tended to be hhlnds a to hae" of moderat Dosert medimtt stAY here proe d O- further depreused the bss t ctol the major the mine wet clmte of the early mone became Carson strong eathqele laving about Nevdl6 It mOWIf known that th awtiwusy from Tuuc ' into Paite an ter ti_ u ad dWilfeutial elevat of the main topo- 1 n August 93, 196 at 951 pm, Plift Of thl Sier1a euline occure down in sev basins, which wer In late Bunejug time, probably lfte Pl thouh graphic units seen today in the aree-thecerson Deser as the ame. magnitude " the bit sadimeats wan lid WItrated rather than ina single hue perhaps earliest Pleistocene, the emptions changed to the Side bsins, and the mountain grPs-lowe- an the Gutenberg-Richter ak) ad separate to varying degrees, itself, y6 shock (U basin as KIng (1678) thougt Mm diatribtio of flows of olivine basalt of fairly consIta compoitiee log to basins severa thousand to ioClly s t 4*,000 gi thehen m masnum-intenity rating, IX. pipe- lithofacee suggests tht the basins ware roughly con- Fumrewr the princpl vet, althouigh may festretlativattedjouningmo ains Togetherthetwo ata was 13O,000 aqsr Ailes. Surface breakage vents also we active. Faulting sees to hav esbotituted the last prugipal period of bema from tlh grnt with many of the prosnt bs, hot only like cimae mainly north of that of the July 6 quake, most of the high- largely died down, for the later lav lows an generally and-ragp ddegoruttion, At the osaeof the second thore of Stillwater Point Reservoir Into the alal somewhat brader. (Foer ezmpl4 ads Adjoining the aouthern Caron Desert wer co- conformable throughout ad rarely display iradn. clima the reief between mountains and basins Was tasoutheat of Canon Sink-about 12 miles-haring faulting. Thee fiows were somewhaist mor - E; somw fresh dialocatione ad with Trucks. sediments.) The basins probably sitioal greter then no, for in lar Qu terry tie e *esagstrend of N. 129 tensirv than the earlier on-e; although thinner, they in th* northern pert of the zone of brak- wer l y deepened by feulting during Trche time, and sedimentation oustripped the declinibin-nd- took placa cmmnly inundated murfes having 1s hundred _munain sue poogre- of the July 6 quak The breakage was as before- buidetformation em tohae been subdued and ion raW deformation, so tha the andsadimentstion dominant during that tine. The feet of local rlief, filling in the depressioms and foi- ivaly more ad more wor down ad the be _ filleul in a single crack -a pertly roughly parallel fields. Some of the higher highlands die. present Carson Desert probebly received especially ing estecuive lava with eiIL he a so" as much sal mile wide; vertical witbout ents wer nevr coved, ho or,er only Daringtht climaeeot of tle falle stletoday au grnt " 1 inches were entirely dip alip, thickdepoeits hower, for the thi cored (wamely the sotustea r White Thre ol fahults w eactid end the aide Invariably was uplifted elatites to the Some volcanic activity continued, wa ativ, fr ma Mountains and notheastern Llontan Noontaiae). now mue meaeld Beth dicibase w_" sheacterisd aids. Property damage Wu slightly hoe sV*n highly tufaceeow sediments attest to oe rabl cew in geeral w similar. tompereous rvolcanism. The large amount of puice by high-e1agle novena faultig which traded Iily from the July 6 ock, ad QUATaNUABY meron: to nort ; tihiag and folin su minor - concentration of damage ocrred in the White Throne Mountains probably came flue nrteast in the greatt wPR-La I oSA rnM eAson, o absent The prlncipel diuplacemevt atthe boun- he Stillwater-lon Tm noew, and commonly In the a narty explolve cnter. Its dominantly, siram-laid eupted in small outline of the earlier Qu te q his- darie between re i and elmb, where pla sflected by the atet hasrecr aggeote that the pumice was Only a nvg herst mountains &ang m Irainewrfired a1I- dig to the FYlao Eagle of August 235,154, ilnr ts over a rer lg intem l, giving m s toy is known be e poet-Bunejug pr-Paiu ban this sediments as aot exposed; stioe infoemationkmswcoe though thel eors ef beth ithigas an basins al- r enl_no gats believed that the picenter Of ample epportunity to insw I Mincr oe Ioee wer suekauleedin placs.- tol mieDbe lw an

LAKEsLAMsONTAN: GEOLOGT, CARBsON DEStERT1, NEV. GEOLO)IC NH8TORY 99

ly occurred both by normal stream capture and by also much thicker than any younger eolluvium, attests Hz6TORT or LLX LABOCTrAN northeast prongs of the Bunejug Mfounttins. Other, ZErzA TIME bars were built just below the Lahontan trrasion through divides by overflow of pre-Lake to stronger solifluction, creep, and slope washs than sub- .' I large spits and ahontan Quaternary lakes. The interbasin canyons sequently., Eolian deposition seems to have been negli- ,; Lakt-depotefftional hirtory.-After developmentof the beach. At Russell Spit (p. 64), for example, longshore ong the middle reaches of the principal rivers of the gible. Sedimentation conditions in the basin interujr Cocoon soil came a long interval of deep-lake condi- drift was both from the south and northwest in Eetzt ake LAhontan basin probably originated, either in this are unknown, for sediments coeval with the PaiuteaSre tions-the first part of Lake Lahontan time-during time, but northwest drift was predominant. In order ay or by superposition on early Pleistocene sediments, here deeply buried. which the Eetza formation was deposited. This forma- for drift from the south to occur here, winds must have tion and coeval shore features record two lake maxi- blown from due south to southeast; Soutlhwsterly winds tring one or more pluvial intervals that followed the The strong alluviation and colluviation suggest a 4 cond climax of faulting. Chief among these canyons climate at least as cold and wet as that during the lake mums. The earlier, at an altitude of about ,380 feet, were blocked by the Desert Mountains. Similar wind r: Emigrant Canyon of the , above maximums of Lake Lahontan. Perhaps the bulk of was the highest level ever attained by Lake Labontan. conditions apparently prevailed at intermediate lake obcoda1, Nev.; the canyon of the Truckee River be- the Paiute was doposited during a pre-Lake Lahontat This level is 515 feet above Carson Sink today, but the levels, as shown at many places in the highlands. .-een Washoe Meadows and Wadsworth; the canyon pluvial period such as that which is coeval with the lake was at least 200 feet deeper at the time of the maxi- History aboe the lake shaores.-After formation of the Carson River between Dayton and Carson VIl- Sherwin glaciation of Blackwelder (1931) in the Sierra mum because the basin floor has been raised by subse- the Cocoon soil, apparently early in Reter time the y; Wilson Canyon, of the West Fork of the Walker Nevada; if so, a predecessor of Lake Lnhontan prob- quent sedimentation. At this level, Lake Lahontan highland washes locally dissected a few feet into al- .4, about gravel of the Paiute along their middle courses. ver, between Mason and Smith Valleys; and ably also existed, but evidence for it has not been found I N.- inundated about 8,640 sqouare miles and extended luvial fill as the Inke turchill Snarrows (an abandoned channel of the in the Carson Desert. The youngest part of the Psiute, 250 miles north atid sotithl and 1S5 miles east and west, This nas followed by a fewnfeet of gravel without overflowing its basin. The second maximulm rose; the fill was graded to the higher lake shores but alker River between Mason Valley and the valley of how-e-er, probably dates from the earlier part of the Al) these can- wats only 40 feet lower. Between the two maximums nas far too scanty to produce deltas. The Carson River o Carson River, near Weeeks, Nev.). last interpluvial interval before the advent of Lake us probably formed at about the same time, because the level of the lake dropped at least 320 feet, but the built a delta, but the exposed part lies west of the mnp Lnhontan (the later part of this interval probably is ey now a re in about the same part of the mature stage recession seems to have been brief judging from the area. represnted by the Cocoon soil). I erosion. They are clearly younger than the last scanty recessional deposits. At thesame time smntl amounts of collurium nere de- to have been r time of relative msa of basin-and-r-nge deformation, yet they were Paiute time seems On the Itighlland shores mainly boulder and cobble posited on the mountain slopes, mainly by solifluction existence long before Lake Lahontan because most of structural stability; at least no faults definitely of this gravel, some pebble gravel, attd minor litltoid tttfa were and creep which reworked the oxide horizon of the sea contain Alluvium, colluviuim, and soil of pre-Lake Age are known. Basaltic eruptions, of this age or deposited, but almost no sand. The tufa was precipi- Cocoon soil. The smnall volume of alluvium and collu- hontan age and several, such as Emigrant Canyon earlier, took place at Rattlesnake Jill, yielding minor tated by mats of algie growing within a few feet below vium from the highlands attests to relatively minor d the Truckee River canyon, contain sediments of flows and ending with minor explosions that left the and sbo-se vater level. Lake-bottom sedimentation his- erosion of these Areas during Eetza time; erosion was ke Lahontan. vent choked with agglomerate. tory is unknosvn because the bottom sediments are rarely practically negligible compared with that in prm-Lake tP'rdcnice of a pre-Lake Lahontan 7ake.-A single ex- Cocoon intcrvai.-The Cocoon interval, when the Co- exposed. Lahontan Quaternary time. sure of shore sedoirent at about 4-,0O2feet (p. 23) coon soil formed, was a time of comparative balance Eetza time was the stormiest part of Lahontan time. Soil development was negligible, the only evidence of ords a pre-Lake Lahonitan Quateritary lake, prob- betoveen erosion and deposition in the highlinnds, when The shore gravels and morphologic features attest to it being an incipiettt weathering profile dating from the y of pre-Psiuite age. The mnximunm level of this chemical wveathering exceeded erosion. The relatively waves stronger than those of any later lakes st all levels, middle-Eetza recession. is not likely to have been much from highest to loavest. The smaller details of the pre- ze is not known but intense weathering, manifest especially by the clay con- WTEEAMATInZ ,lter, for the bedrock floors of pre-Paiute Quaternary tent and reddish-brown color of the oxide horizon of existing topography were severely modified by carving cliffs, accompanied by iyons along the middle courses of the Tnickee, Car- this soil, suggests that the climate was considerably of prominent shore terraces and A relatively long interval, wvhen the Carson Desert , And Hu1m-boldt Rivers were grade(l to a base level warmer than now. Precipitation also must have been construction of correspondingly large gravel terraces, was completely or nearly dry and when the Wyemaha I bars, and spits. Ott shores most exposed to waves, the recession of the least this low. The lake may have been fully as higher than now, for strong soil formation could not formation was deposited, followed boulders, commonly several feet it diameter, were dis- p as Lake Lahontan, nevertheless, beecase the Car- liave taken place under the intettse aridity that other- second Eetza lake. Early and middle Wycmnaha time lodged and transported, and terraces fiOto locally 200 of Desert was not as deeply alltvinted as nowy and its wise would have prevailed under the higher tempera. .I n-as characterized by deposition of vast quantities feet n-ide were cut in hard lava rocks. Ten main shore- in the wrprobably lay several hundred feet lower. ture. The strong calcareous horizon, however, is typi- eolinn sand, which virtually drowned some areas lines were formed, as nwellas more than a dozen mod- passes. Defla- thick zones of clay peletrated by wells in the deeper cal of soils formed in semiarid rather than subbumid basin interior and the lower mountain .L. erate to weak ones (pl. 0). The strongest waves (and itg plr-Litke anhon- tion and transport of the sand were favored by sparse in-interior fill suggest long-last climntes. Thus, the Cocoon soil probably formed under I hence the most severe windstorms) date from the first vegetal cover and severe windstorms. The volume of Qutternary lnkes, but canIot bc correlated with ex- a semiarid climate somewhat warmer and wetter than Eetza transgression As sntggested by thle fact that the far too great for it to have been derived ed deposits. now-probably the later part of the interpluvial in- 17 lower part of the lake gravel generally is the coarsest this sand is the area, prob. 'AhIte tilnc.-ln later pre-Lnke Labontnn Quater- terVnl preceditng Lake Lahontan. Evidence is lacking .k and is associated with the most strongly developed shore locally; it must have come from outside ably from extensive sandy outwash plains and deltas in y time tlle Paiute formation wasRSdeposited. Paiute ott sedimentation and lake conditions in the inner Car- ;1 features. e was characterized by marked alluvintion and col- sonl Desert, for here the zune that represents this soil is Distribution and orientation of Eetza shore deposits Carson, Lower Carson, Smith, and Mason Valleys. .ntion in the highlands, and presttmably by eon- deeply buried. and morphologic features shotw that strong winds came Sand was blown from these areas in great belts, 40 to vrnble nllley erosion in the mountains. Alluvial -4 from all directions except east, but mainly from the ,5 miles long and a dozen or so miles wide, trending built that are much larger And thicker than *ltenltra d ra-t. waitto darting Dru-tAl tahotnas Outttnua T north, northwest, And souith west; northtwest winds pre- genterally northeast nnd enst -northeanst neross mountains a were tta. tear to bh.- bh,. ttr mat..I. - the enorebtslrottle d fote- s'"tbeellflwt ones, and the lithology of their gravel and adttt at rok oucrop. tbht eararterta- tha ooatnof tbh . : I domitinted. Wlitds from the sottth mtsd sotthsvest were And basins. The greatest concentrattion of Sloesand though ephemernl, had el,. tOret t19a4. p. 4:) --tmctentd oa t.e moeb- t11te. ott1e- tduring Sethoo time. For near t(le Carson Desert is just south of the map area in Ivs that the highland wnshes ttoa nn taarlh aoralat esorted to inoath etot-r de.tort trooler ntflolt.lnO much more promitett tian ential floods at least as big as the largest in lake 00 aorth toi-e, a a Vpn.lblM .. tpton ol theflab that the aerth itstanee, nhile the lake was comptaratively low, large the north Ialf of thle Alleto Springs quadrangle. The tw.e at X.ll tht. catlt- d tn0 ha19 ..d .eolt.tly st1.d. mueh less tIan now, for Al- tonlan time. The col1luvial mantle ini the mouiittains, aad tbh *oulh .Omt bhortand *.tD. spits were bttilt nortilnard from the nortitnest and higltland wiashes flowed

'. 42 -I ,_1 ,j I- : a NEV. ,.I GEOLOGIC ISTORY 101 LAKE LABONSTAX GEOLOGY, CARBSONDEtSERT, .4 winds came time was brief compared with the deep-lake intervals of luvium of this age is very scanty and many of the The accelerated rate of soil development and the some- 'i4 races, spits, and bars show that the strongest north and practically Sehoo time. The lake receded at least as low as 3,990 canyons were deeply choked with eolian sand. what reddish color and moderate clay content of the II mostly from the northwest and ,j not at all from the south or southeast feet in the Carson Desert, at which level it inundated These features bespeak extreme aridity. Conditions oxide horizon suggest that the temperature was higher deposited on the highland shores 1,500 square miles and was 125 feet deep. An incipient probably fluctuated, however, for the thickness and than now. The strong total profile development and . I Much more sand was because the lake reworked soil formed during the recession interval. character of the Wyemaha where it is penetrated by strong development of the calcareous horizon of the than during Eetza time, N of eolian sand of the Wyemala. After the thinolite recession came the fourth deep- wells in the basin interior suggest considerable alluvia- soil, well-developed plant cover, and lakes in the low- the extensive mantle -1 deposited locally by algae growing near shore lake cycle of Lake LAshontan, the middle Sehoo lake, tion by the Carson River and intermittent inundation lands all attest to semiarid rather than arid climate. Tufa was water. Maximum tufa deposition was be. when the dendritic member of the Sehoo was deposited. by shallow lakes. During much of Wyesnaha time the Precipitation must have been considerably higher than in shallow 4,355-foot lake levels, particularly Only four clearly marked shorelines were formed dur- river probably rarely reached the Carson Desert; the today or otherwise the higher temperature would have tween the 4,150- and strong waves, forming in places ing the lake rise; they are devoid of rock cutting and lowest sumps were playas; and deposition of eolian resulted in extreme aridity and would have inhibited on headlands exposed to several inches to 1 foot or more have only thin local shore sediments, rarely coarser than deflation of fine sediment were dominant rather than promoted soil development a continuous blanket sand and gravel, suggesting that the lake either rose processes in the basin interior. Flow of the Carson River into the Carson Desert thick. The final 15 feet of the lake transgression, how- medium ever, was completely devoid of tufa deposition. While with few pronounced stillstands and(or) that widld- Explosive eruptions at Upsal Hogback deposited probably increased, bringing in more alluvium, for the from 4,175 to 4,330 feet, gastropods flour- storms were infrequtent and relatively mild. A particu- bas.ltic tufg and tuft breccia in the vicinity; these erup- sump areas wvereinundated by fairly permanent shallow the lake rose ished in sheltered places-especially drowned mountain larly distinctive and abundant tufa, dendritic tufa, was tions had virtually ceased by late W1yemaha time. lakes, in which highly organic silt, sand, and muck were canyons-in greater numbers than at any other interval deposited by nlgae growing nearshore in shallow water; Late Wyemaha time was characterized by increased deposited. The Churchill soil probably developed on of Lake Lahontan history. Also probably during the perhaps the algae flourished because the climate was the highlands, npparently from aug- the subaerially exposed basin-interior sediments, but it alluviation in lake transgression, a volcanic explosion at Soda Lake unusually sunny and calm for a deep-lake interval. mented local runoff that was due to increased precipi- was removed throughout the lowlands at the close of blew out mainly older basin-fill sediment and a small The Carson River added much sediment to its delta at tation during a probably short interval before the pro- Churchill time by waves of the lake transgression that percentage of basaltic lapilli and bombs. The clay de- the western edge of the Canrson Desert. cover that characterized the Churchill developed into the early Sehoo lake. tective vegetal posited on the lake bottom probably came mainly from The maximum of this lake was at about 4,190 feet, interval became established. The alluvium was gen- 621nOOTINE turbidity currents generated by the Carson River and to 200 feet above the known minimum of the thimnolite re- eraily sandy owing to reworking of the ubiquitous negligible degree from local wash inflow or hill-shore cession; lAke Lnhontan then inundated about 6,000 blanket of eolian sand. Its scantiness and lithology, Lake-depotitional Aistory.-The Sehoo and Indian erosion. The lake water was fresh, for the clay is non- square miles and was a maximum of 325 feet deep in the together with the absence of soil development, sug- Lakes formations record the second general deep-lake saline, but fish apparently were not numerous. Carson Desert. Waves were so weak and(or) the maxi- gest, however, that precipitation still was relatively low period of Lake Lihontan. The lower, dendritic, and The lake maximum, at an altitude of about 4,370 feet, mum stand so brief that the high shore is poorly and characterized by infrequent, torrential rains. The upper members of the Sehoo and their associated shore was only 10 feet below the highest Eetza maximum and marked. On its recession, the lake formed 18 faint to Carson River probably also brought more sediment to morphologic features record three deep-lake cycles inundated about 8,300 square miles. The highest level moderate shorelines, the best-marked ones being below the Carson Desert. during this period, and the intertonguing parts of the is marked by prominent terraces, bars, and spits, indi. 4,115 feet, and local pebble gravel was the coarsest shore The close of Wyemaha time is placed arbitrarily Indian Lakes avid the thinolite unit of the Sehoo record eating a pronounced and stormy stillstand. waves obviously remained weak. at the start of the Churchill interval, which is an important lake recessions after each lake maximum. sediment; Between the early and middle Seboo maximums the During Inte Sehoo recession time, when the upper essentially time-pnrallel boundary. In the high. It is possible to get a much clearer picture of the lake receded markedly but probably did not become en- formation was deposited lands this boundary is at the top of the youngest lake-depositional history of Sehoo time than for Eetza tongue of the Indian Lakes tirely dry. During the recession from the early Sehoo lake surface alluvium and eolian sand of the W1yemnaha, for here and Wyemaha time, owing to excellent exposure of the and the Hanrmon School soil formed, the maximum only a few well-marked shorelines were sedimentation seems to have practically ceased while Sehoo and Indian Lakes formations at all atratigraphic dropped at least as low as 3,900 feet; in other words, formed, mantled mainly with pebble and cobble gravel, the Churchill soil vaesforming. In the inner low- levels, even in the basin interior, their favorable stratig- Lake Lahontan became nearly or completely dry. At to infrequent strong windstorms and perhaps lands, however, deposition of sediments that are re- raphy, and well-preserved shore morphologic features. attesting this known minimum, the separate lake in the Carson few stillstands. As the lake receded below the inter ferred to the Wyemabsa continued through Churchill During its transgression, the early Sehoo lake formed Desert had a maximum depth of only 35 feet and an basin thresholds, it was split into separate lakes in vari- time; this final episode of Wyemnaha sedimentation is the most strongly marked shorelines of Sehoo time and area of about 500 square miles. ous basins. When the lake level dropped below about in the following section. deposited the coarsest and thickest gravel of the Sehoo by the discussed Basin wits separated; at about The following late Sehoo lake is recorded formation, indicating strong waves, repeated strong 4,200 feet Pyramid-Winnemucca area upper member of the Sehoo formation. A distinctive PrUccasLL rarrtvAx windstormr, and probably many halts during the lake 4,100 feet. The lake in the was separated from that in the Hot.Springs Valley and lithoid tufa was deposited locally by algae during the The Churchill interval, recorded by the Churchill rise. On the shores most exposed to waves the upper the latter was separated into two lake rise. Absence of wave reworking of the tufa and soil, was another time of reduced erosion; the eolian several feet of earlier gravel were intensely reworked, Carson Desert, and Rngtown Pass became exposed below about of transgressive shorelines shows that the weather re- stablired and deposition of alluvium large. so that only the larger boulders remained undisturbed; lakes when sand became mained calm. At its maximum, about 3,990 feet, this ly ceased in the highlands. Although the climate may shore features of Eetza and alluvial fans of Wyemaha 4,050 feet. the recession was at and near its lowest levels, lake inundated about 1,800 square miles and was 120 have been less windy, the main factor in stabilization nge were severely modified. At the main shoreline levels While of 4,040 feet, the thinolite unit was The Carson River built a sandy delta 10 probably was development of plant cover, probably sizable spits and bars were built, in places extending I below an altituede feet deep. Thinolite, the distinctive sediment of this miles wide, which was graded to the high level, yet mostly grasses. Shrubs also seem to have been present, mile and locally over 2 miles from source hill shores deposited. member, precipitated as euledral crystals of aragonite elsewhere the high shore is marked only by small local however, as evidenced by calcium carbonate concentra- across adjacent reentrants Windstorms were probably offshore water. The marked bars and bench terraces, attesting to weak waves. The tions surrounding their deeply penetrating roots below less severe than those of Eetza time, however, for the in both shallow and deep clay in this unit compared with was active, creating a prominent the calcareous horizon of the soil. Probably the plant shore gravel typically is less coarse, rock cutting is less thinness of lAke-bottom Sagouspe fault zone members, and the nb- fault ecarp in the lowlands. l)ring the lake recession cover was more dense during this interval than during in evidence, and constructional features generally are that in the lower and dendritic shorelines suggest that thinolite the Carson River floved northward across this scarp, any other part of Lahontan Valley and Recent time. smaller. The distribution and orientation of shore ter- sence of well-marked LAKE LAHtOITAN: GEOLOGY, CARB5ONDESERT, NcEV. GEOLOGIC HISTORY 103 as now, and built another delta, about a third the size mammal bones of thinolite recession age from Hidden Turupah formation; the finer fraction was partly'de- the deltas were graded to the lake maximums, and the of the western delta, in the western Indian Lakes area Cave consists entirely of living species, and the large posited as a blanket of loess in the highlands and partly sizes of the deltas were roughly proportional to the Hiatory ol .ubacrial erosion and deposition in the collection of vertebrate bones of the late Sehoo age6rom Deflation was easier during corresponding lake, suggesting that maxi- N 1 blown outside the basin. height of the Aighlands.-Throughout Sehoo-Indian Lakes time this site records a fauna similar to, but more abundant Turupah than during Fallon time because the Toyeh mum alluviation was synchronous witla the lake maxi- subaerial erosion and deposition in the highlands were than, that of today, only Eduw ocridentfai being soil had not yet formed and its stabilizing effect was mums. The base level to which the river graded its minor, and changes in subaerial processes with time extinct absent. In the highlands eolian sand of the Wyemalea flood plain has changed with the rim and fall of the were too small to provide contrasts in lithology or Human occupation of the area may date from about and lake sand of the Sehoo were extensively reworked, lakes, but it trended generally downward, correspond- widespread disconformities within the Indian Lakes the time of the middle Sehoo lake maximum (Gross but there was less wholesale eolian transport and depo- ing to the lake maximums; the flood plain was cut a formation. Earlier alluvial fills were trenched a few cup, 1956), but conclusive stratigraphie evidence has sition than in Wyemaha time. few feet below the earlier deltas a the later ones feet along the middle reaches of the mountain washes, not been obtained. The single projectile point discov- The Carson River apparently rarely reached the formed. and small alluvial fans were built on the piedmonts. ered in place in upper lacustral clay by McGee (1889; Carson Desert, and the highland washes did not flow First lake-The first Fallon lake, recorded by the The coarseness, distribution, and structure of the allu- Russell, 1885, p. 246-247) is apparently of Sehoo ae, enough to lea-e recognizable alluvium. The paucity of first lake unit of the Fallon formation, apparently had vium show that it was deposited by torrential floods of probably middle Sehoo. A small nomadic Indian pop- fossil and archeologic remains suggests that flora and merely a single stillstand at and near its maximum normally dry washes that were larger than at any sub- ulation occupied the area during late Sehoo lake time, fauna were very sparse and that the area was generally level (3,948 feet), for transgressive and regressive late Sehoo lake maximum sequent time. During the judging from the archeologic record in Hidden Cave uninhabited by man (Heizer, 1951, p. 92-95; Morrison, shorelines are not evident. At its maximum it inun- alluvial gravel was carried farther into the interior of 9 miles entirely within the (Grosscup, 1956; Morrison, 1958c) The four projectile 1 58c). These conditions all betoken aridity more dated about 1,140 square the basin than subsequently, in places as far as the and it had points found in Hidden Cave are unlike any points stark than now, which was possibly accentuated by Carson Desert and lower Humboldt Valley, Carson River lakeshore. previously reported for the and Car- temperatures higher than nowyas Antevs (1948, 1952) a maximum depth of about 85 feet. The During the thinolite recession the Carson River toward Carson Lake and its vari- son Desert areas, but resemble some from Dixie Valley, has suggested. flowed southeastward to 100 feet into the delta it had built dur- ToYER IlNTERVAL built three sandy bigh-shore deltas, trenched 60 Nev., from the lowest level of Etna Cave, Nev., and ous distributaries ing the preceding lake stage and the trench was later practically continuous and approximately coeval (table from northeastern California. Turupah time was followed by the Toyeh interval, sediment of the middle Sehoo lake. This along the high shore, lake sand was filled by during which the Toyceh soil formed. Concomitantly 7). Elsewhere delta was trenched again during the late Selhoo reces- aOST-LAK LAHONTAN HISTORY reworkitng of dunes of Turupah age. It plant cover increased, the dunes were stabilized, snd deposited by sion and during late Sehoo lake time, when the floor away from the delas, a few inches TRauPArn TIX deflation practically censed. Though this interval deeper depressions was graded to a lower delta on the high clay was deposited. The of the trench probably lasted only a few hundred years, it pro- to a few feet of dark lake interval of marked suggests that this lake was shore of this lake. Sehoo time was succeeded by an duhced the strongest soil development in all the time salinity of these sediments Mass wasting also was more active than subse- the Carson Desert was completely dry very saline. aridity when from the end of the Churchill interval to the present- Slope wash was the dominant colluvial proc- the time and the Turupah formation was a quently. much of probably 20 to 60 times longer than the Toyeh interval. Contemporaneous with the maximum of this lake, Earlier collu- Toyeh in- ess, and solifluction was subordinate. deposited. Turupah time and the following Soil formation probably was induced by relstively high separate lake seems to have existed at a lower level in the calcareous horizon of the Cocoon soil, to the altithermal age vium, above terval are together equivalent tempernture, perhaps continuing from Turupah time, Eightmile Flat. This like probably was fed by sub- was locally moved, but the net modification of valley of Antevs (1948, p. 276-179), which has been dated coupled with an increase in precipitntion that continued surface seepage through the sand underlying the divide slopes was very minor. Block streams formed locally from geologic and archeologic evidence and radiocarbon into first Fallon lake time. between Turupnh and Eightmile Flats, for there is no on mountain slopes by washing out of fines from soli- methods as starting 7,500 to 7,000 and ending 4,500 to sign of an overflow channel across this divide and local fluct ion mantel of Eetza age. 4,000 years ago (Heizer, 1951; Antevs, 1948, 1952, FALLON TIXZ runoff from the drainage area of Eightmnile Flat was Some wind erosion, particularly of eolian sand of p. 103,1955, p. 323, 328-329). Probably the Turupah inadequate to support such a lake. otsTOsa IN rut XasRIs MTnatMs the Wyemaha formation, and eolian deposition prob- occupied all but the final 500 to 1,000 years or so. b5EPORITIA*L First take rceeasfon.-Recession between the first and ably took place in the highlands during the transgres- Turupah time was characterized by eolian deposi- Genesl featurme.-The Fallon formation records at second Fallon lakes is demonstrated by ealian sand and sion of the early Sehoo lake, for this was a time of tion and erosion. Large quantities of eolian sand were least fire cycles of shallow lakes alternating with desic- alluvium of the first interlake unit as lowe as about severe wvindstorms (p. 100). The remainder of Sehoo deposited, derived from sands of the Sehoo and Wyt- cation during the last 4,000 years or so. None of thei 3,910 feet in the Carson Lake area and about 3,900 feet timelwas presumably relatively free from eolian ero- maha formations, and large deflation basins and plains desiccation intervals wrasas long, nor probably as arid, in the Stillwater Lakes area-at least comparable to sion and deposition, for wave action apparently was were created in the basin interior. Complete lake as Turupah time. The lakes ranged only from about present conditions. This was a time of considerable weak and eolian sand is rare. desiccation is evidenced by the marked deflation of 15 to 85 feet in maximum depth, each lower than its dune constmrction atd some deflection, particularly in Soil development was practically nil during most Carson Sink itself and by widespread eolian sand predecessor (table 7). The Carson River repeatedly the lowlinds. About a foot of eolian sil and slope vash of Sehoo-Indinn Lakes time; the only discernible de- of this age at altitudes below 3,890 feet. Deflation changed its lower course, swinging in an are of nearly was deposited in Hidden Cave. Small gullies were dis- velopment was the incipient soil that formed during was most severe in the western lowlands; in many 120°, and deposited a fan-siaped blanket of alluvium eeted along Wildcat Scarp. Soil development was the th-nolite recession and the very weak Harmon places the erosion went entirely through the Sehoo and deltaic sediment (pl.I 11). ost of the time the Iiarely discernible. School soil that formed during the late Sehoo recession. formation into the Wyemahs, locally removin 20 to river drained southeastward into the Carson Lake area, Second lake-During the transgression of the second A moderate vegetal cover, probably mainly grasses 40 feet, and rarely more than 60 feet, of Sediment. but occasionally it drained enstward toward the Still- Iake, the CarsonmRiver built a small delta overlapping and shrubs, probably existed throughout Sehoo time. From I to 8 feet of sediment is estimated to have been water Slough or the south end of the Stillwater Lnkes, tlie eastlermmost delta of the first Fallon lake. At its A more abundant fauna than now seems to have been removed over a large part of the lowlands-an aggre- and twice it swung briefly northward toward Carson rmaximum the lake reworked and beveled the margins at least sporadically present. Perhaps the animals- gate volume of at least half a cubic mile in the map Sink. Whetn the lakes were dry or nearly dry the river e1fsand duines built during the preceding drought atd horse, and camel-of early Sehoo age died out soon area. The sand was mostly redeposited within the lake intervals I. sandy lion, I. actually reached these areas; during the acally formed smailnl airsof gravel andnd. Iie after early Sehoo tine, for the small collection of basin as dunes and drift sheets of eolian sand of the it built deltas on the west shores of tle lnkes Most of areas above the lake eolinn sand was added to earlier I I.1 CEOLOGIC MsrYos 105 LAKE LAISOrrAN: GXOLIOOT,CARSON DESE:RrT,NEV. I.i the water to the slough Was reported by Captain Simpson to be Slight colluvial activity took place on the mountain dunes. A faint shoreline marks a minor recessional rowe high enough to overflow the threshold into Carson I 50 feet wide and S or 4 feet deep, and SoeIng northward with slopes, but it wars infinitesimal compared with that dur- stillstand at 3,927 feet. Lake. Thus there were many more small lake fluctua- In 8eptemeber\iSet6. Lient. R. Ritaie tate a strong eurrent ing Eetra and Sehoo times; the record in Hidden Cave Complete desiccation of the Carson Desert during the tions in the northern area than in the Carson Lake area, I that the waters were sletglsh. wtih sesraely a perceptible fow. of water &bout the came as suggests that the total amount of such activity was less second interlake interval is suggested by local eolian much more of the .,i In June. 1881, 1 found the volume and Carson Sink probably was dry reported Or Simpson In 2851.mnd flowing northward with a well- than during late Sehoo time alone, and that it virtually sand, recording minor eolian erosion and deposition, time than Carson Lake or the Stillwater Lakees. -I marked current In Setember. 5883.the slough was lo. and stopped during the driest intervals. Mass wasting is as low as 3,880 feet. The very weakly developed The Humboldt River also terminates in Carson Sink did not exhibit sny motion; South Carson Lake at the same rime most active at present in the highest mountains of the J was ,err shallow. much of It jremeathia the spperanrce or a L-Drain soil formed during this interval, representing and therefore the sink probably also received intermit- I i region where rainfall and snow accumulation are swamp. the main soil development during Fallon time. The tent inflow from this river. Historic records of dis- greatest Carson River continued to drain to Carson Lake and charge suggest, however, that this inflow tends to be .-1i Russell (188, p. 69) also mentioned that in 1882 Car- ERoian erosion and deposition took place intermit- son Lake had an arts of about 40 square miles and a built a large sandy delta on the north shore, which was proportionate to, but generally less than, the discharge tently and locally in the highlands on a small scale, oen- ..4.-7. about 4 feet in its central part. graded to about the present level of this lake, which is of the Carson River into the Carson Desert; hence, its depth of tbring in the lower highland passes that had received the Newlanda Reclamation almost dry. Stillwater Lakes and the Carson Sink effect is assumed to have been subordinateto inflow from Since development of extensive earlier accumulations of eolian and lake sand. which started in 1905, the channels of the Car- probably remained completely dry. the Carson River, even in the northern part of the basin. Project, son River and Stillwater Slough have been straightened iOMAS OCCUPATION Third lake.-The third lake of Fallon time was so The two highest lake maximums in the northern area and locally deepened, the river channel has been stabil- sIallow that the divide between Carson Lake and Still- were successively at about 3,905 and 3,890 feet. The Nomadic Indians occupied the arem intermittently ized in its northward course to Carson Sink, and the water Lakes, in the NWr/ , T. 18 N., R. 30 E., remained 3,905-foot maximum cannotbe correlated with the maxi- during Fallon time, living close to the lakes and streams. 4 river discharge has been controlled by construction of with exposed and the lake maximums were not accordant in mums of Carson Lake; the 3,890-foot maximum was The density of occupation seems to have fluctuated Lahontan Dam and several small diversion dams. In were highest the southern and northern lowlands. These maximums reached in 1862, but may also have been reached earlier. lake levels, being greatest when the lakes 1907 the second largest flood in historic time occurred although sparse are marked by faint shorelines and deltas, at an alti- Published records show that Carson Lake was at its and least when they were desiccated, on the Carson River, causing a temporary diversion tude of 3,922 feet in the southern (Carson Lake) area overflow level-at an altitude of 3,919 feet-in 1845 temporary occupation may have persisted along the past the south edge of Fallon and thetice inlo Stillwater and at 3,915 feet in the northern area. The shore (Kern, 1876), 1859 (Simpson, 1876), 1862, 1868, 1873, Carson River and perelinnl springs through some of the Slough. deposits in each area do not overlap: although approxi- 1881,1883, and 1885 (Russell, 1885, p. 44-45). It prob- dry intervals. Doubtless the density fluctuation was As a result of the shifts of the Carson River and lake the lake mnximums they record in ably was generally below this level during the 1840's, due to corresponding variations in the food supply. mately correlative, inundations, the flood plain grew and several small may not have been quite synchronous. The for this decade was a drought period in the region (An- The time of the first Fallon lake was one of sparse each area deltas were built on the north shore of Carson Lake, southern lake maximum was controlled by overflow tevs, 1938b). Recent minimums were in 1904,1919, and inhabitation, as recorded by the few artifacts in the so. near Stillwatter, and at theedge of Carson Sink. Bolian across the threshold to the northern area, then at about 1924-1934. Carson Sink generally was dry during the called 32-inch midden layer in Hidden Cave (Groascup, erosion and deposition continued, reshaping the sand 3,921 feet, creating a narrow flood plain along the pres- 1840's and from 1880 until 1905. It reached its highest 1956, p. 61) and by rare occupation sites along the high dunes, and to a slight degree, the deflation basins. ent Stillwater Slough which -was graded to the high modern inundation in 1862, after the largest floods of shore of this like. Probably Indians did not return to Where eolian sand was successively inundated by the shoreline in the northern area. Probably late in third historic time in the Carson and Humboldt Rivers. the area quickly after the depopulation of Turupsh shallow lakes, eolian and lake sand were intricately in- lake time the river shifted into its old northward (The Humboldt River apparently contributed consi- time. Inhabitation also was sparse during the first lake terbedded. channel-the present course-and built another small derable inflow at this time, for R waterpowered grist mill recession, and clustered mainly around the shore of the delta graded to a lake level at about 3,915 feet. was in operation at White Plains station, halfway be- IaOu6tO1ALA"r DEPeOSmONALITSTOnv Is 7a1 ninLAssI shrunken Carson Lake. The loess layer in Hidden RemainingFallontfine.-The third lake was followed tween Humboldt Lake and the mouth of the river.) During Fallon time the highland washes deposited a Cave that is correlated with the first Fallon lake reces- by marked recession, perhaps complete desiccation, then In 1863, when the first public land surveys were made little alluvium on their fans, but much less than during sion is almost barren of artifacts, The Carson Desert, the sink was inundated to a depth by two or more very shallow lake cycles. in the Carson late Sehoo lake time. The poor sorting, great range Indian inhabitation reached its all-time climax dur- mostly southeast- of about 20 feet, and Pelican Island actually was an River shifted its course several times: in grain size, and high angularity of the alluvium ing the time of the second lake, as shown by many open ward to Canrson Lake, occasionally enstvward to Still- island. The sink was completely dry when Russell 885 reflects its dominantly rapid transport and deposition sites along the high shore and by a conspicuous midden water Slough or the south end of Stillwater Lakes, (1 ,p. 88) visited it in October 1881. by flash floods after infrequent heary reins. Large layer in Hidden Cave, which contained 85 percent of and, least commonly, northvward to Carson Sink. When Russell (1885, p. 44-45) outlined the modern history differences in volume of alluvium between washes the artifacts recovered during the 1951 excavations at the river drained to Carson Lake the Inke maximums of the changes in course of the lower Carson River and show that the torrential this site (Grosacup, 1956). Inhabitation again was were controlled at an altitude of 3,919 feet by overflow the history of the lake fluctuations as follows: of similar drainage area rains were spotty, causing big floods in one canyon sparse during the second lake recession, and clustered across the threshold to the northern area, via the Previous to IMIt a-owed into the South CanRon Lake, but Lake. Later Fallon time seems slightly entrenched Stillwater Slough. The maximum there was an abhadoned channel branching from it aod teading and little or none in a neighboring one, but the mainly around Carson level was reached at least twice, long enough to develop northwarl. Duringa time af unuousnly tnthgwater it tbe priong generally small volume shows that most canyons and to have been a time of sparse to moderate occupation, IM1 the old ehannel was reoceupled sad a distinct though faint sloreline. W1hen this lake over- at the river bituralted, washes had few big floods. Tlhe episodes of alluvia- when the Indians lived mainly in open sites near the a branch Bowed to ethb lake -* - Previous to that time there Lakes were flooded as, probably cannot be precisely correlated with the lake inter- permanent lakes and watercourses. flowed, the Stillwater was a alough" Connecting North and South Careen Ltakes thre tion at times, was the Carson Sink. The northerni lakes whtch the aters Sowed aorlhward. After the forking oa the vals, but the main activity clearly vas early. Degrada- Grosscup (1958, p. 1-03) correlates the cultural ma- probably fluctuated even more than the seasonal varia- stressm the South lake was lowered so that It no tonger over. tion of the highland washes wsas imperceptible. The terial of first- to second-lake age with the Lovelock cul- tions in river discharge, because evaporation from Car- lSawed and the water in the sloumohb ame etagcant. Another historic arroyo cttting that was dominsnt in most of the ture of the Humboldt Lake area (Loud and Harrington, Seoodoccurred In the mptrin of 180? or IP. whieh caused the son Lake and the lower chnin of lakes tended to accentu- many less arid parts and Krieger, 1956) arm emptying intto orth Cransi lstke to branch and send a Western United Stales, includitig 1W29; Heizer, 1951, 1958; Heizer ate these sriations. Wthen the river drained directly stream eastward to Ihe tlongb. The lant.forneda chanel to stilt of Nevndn, has not yet affected any of the washes in the and the artifacts of Inter Fallon age with prehistoric Cnrson lake revnni,,ed entirely into thie northern area, oecupied and in kloawn as "New tahr.' Thl, dslnlhbuttos of area. and historic Northern Paiute. dry, as none of the late Fallon lakes in the northern area the waters of the Carson still continues * - - Ia June. MI). LAXE LAISONTAN: GEOLOGY,CARSON5 DEEs-zr, NEVY. GEOLOGICOOGCH-rs10 HISTORY 107

CUUAT'C fleorIT severe drought in 150 to more than 050 years (Antevs, The record of Fallon time-deposits, fossils, arche- 1948, p. 182). logy, and geomorphic features-nttests to small cli- COMPAIMRsONS WXrm PRnzvaOU a ~ernasloiea intic fluctuations, but without marked differences from RutsclaeU interprftation.-Russell's ie present climate. During the desiccation intervals (1885) cofiu. sions on LAke Lahontan se climate probably was about like now, except during are as follows: Lake Lahantan had two high-water periods, ie second lake recession it may have become slightly represented by the "lower lacustral clays" and "upper armer, as suggested by the fact that the only apprecia. lacustral clays," and an intervening period of low water and probably complete Is soil development of Fallon time took place then. desiccation, represented by "medial gravels" 'he lake intervals were probably both cooler and wetter (fig. 38). The first lake lasted longer than the second, but the rise. ian climate today. The first lake maximum marked of the second was more abrupt, and its maximum ie moisture maximum and probably the temperature waas about 30 feet higher. The maximum of I inimum for all Fallon time; however, it is doubtful the first lake is marked by the lithoid terrace 500 feet i hether annual precipitation increased more than sev- above the 1882 level of Pyramid Lake, which is 3,867 feet according to I -nl inches or temperature decreased more than A few Antevs (1945, p. 29, 30) making this maximum an alti- tgrees from present values. tude of 4,307 feet; deposition of lithoid tufa was re- The indication of the Iske record that the magnitude Z.I stricted to the recessional phase of this lake. Pyramid t the wetter cooler fluctuations that produced the lakes Lake, which is the lowest of the major sinks in the Lake eadily diminished toward the present suggests that Lahontan drainage area, may have become completely .5I eogeneral trend in climate during the 3,000 or 3,500 dry during the middle Lake Lahontan desiccation. mars since the first Fallon lake maximum has been to- I During the transgression of the second lake, there was ard increasing aridity and possibly greater warmth. a long stillstand at the level of the thinolite terrace and ich an established trend is likely to continue into the a short one at the dendritic terrace, 110 and 320 feet, ture, with of course temporary reversals. Anters respectively, above the 1882 level of Pyramid Lake (at 938b) analyzed the very recent climatic cycles of this altitudes of 3,977 and 4,187 feet) and thinolite tufs gion and predicted the climatic fluctuations for aev- was deposited as high as the thinolite terrace and den- al decades; his forecast is proving to be remarkably dritic tufa as high as the dendritic terrace. The La- I curate. hontan beach marks the maximum of the second like, Fallon time I seems to have been one of moderate 530 feet above the 1882 level of Pyramid Lake (altitude ndiness, judging from its eolian deposits and eolian 4,397 feet). Pyramid, Winnemucca, and Walker Lakes ision features-less windy than Turupah time but probably dried up completely during an interval more i nerally more windy than the later part of the Sehoo arid and warmer than now between the time of the sec- ne. The desiccation intervals apparently were gen- ond lake and the present, because these lakes do not illy windier than the lake intervals, for most of the contain as large a concentration of salts as they should inn sand seems to have been deposited during the if they were mere shrunken remnants of Lake Lahon- icecation intervals; moreover, the higher shorelines tan. This was the earliest deduction of the warm Arid the Inkes generally show little evidence of strong interval which is now recognized throughout the world re action. The modern deposits of eolian sand sug- as the thermal maximum, and which in the Gre .t Basin it that windiness recently has increased: areas of has been called the altithermal age (Antevs, 1948, ive dunes seem generally to be growing, and the more 1952). vntly deposited beds in the dunes commonly are ,rser than the earlier beds. Antets' interpretation.-Antevs (1925m) first con- cluded, from a series of stratigraphic rhe early winter of 1825 is reported to have been sections measured along the optionally cold-so cold that all buffalo in the Great valleys from the Truckee, Humboldt, and sin west of the Rockies were killed (Simpson, 1876). Walker Rivers, that Lake Lahontan had three and per- severe drought occurred in the 1840's. The period haps four high-water stages, separated by intervals of Em 1850 to 19D23was generally abnormally wet; the low water or complete desiccation. More recently, els reached by the principal lakes of the region be- (1945, p. 30-1; 1948, p. 171; 1952, p. 100-101) ho17- 'en 1850 and 1919 were the highest in 200 years or ever, he inferred only two high-water cycles (fig. 8&j, re (Antevs, 1948, p. 180). From 1824 through 1934 separated by an interval of partial Inke recession. The 'cipitation and runoff were subnormal in the north- first lake, "Lake Lahontan proper," rose the highest, to stern part of the Great linsin, and temperature was 4,397 feet at Pyramid Lake; the following recession, ose normal; these conditions produced the most the "Thinolhe Lnke," was to the level of the thinolite

t - -. -I mom -

IAIK5 LhMOMUE' GOWOano, CAhOMI10118M, N?. 00eaanow UDb Aer 0, i WtAINMANAf 851M65 AND 4Qg. 10 rneo, ailtitede Jodee; and the "Aymr gr"D deep-lake riod (Eta tim), _ot during the Co atin ip p ioed i euieaM A" of iw nCs, in ter of rltie age and relative develop iticlak m to a maciuum of 4B fe (I'M a (Sehoo tim). I -Al e-Ccmlatli by posin of aatigraphie units meaof the Wos.- Inauk ststheoilefanned durng 31; 1384 P. LJ), which was lat revised te 4,140 . C^atrar7 to both inepretatio, both of the main in of depesitional cycle is the traditional -dietiact widel separated itervalsinlaevsposae to rela- It (184 p. 101) from week in the llumkU Valley. -. damp-lake pelod multiple smaximuema mas of carelating Quateny dP-k The do. tve Infrequent o fdof iesa facrs that eAnteve (1954 p. 36) assigned a sgoeof4000 I. Ukws several low lake cycle accurred in pest siloe cycles sme veel by " rdia glacial. lacue- induced erosional stability sai a mere wood rate el arc to the "lAhontaa Ir maximum. (proably hk Lake Lalootas (Fyame) time. tria, hall ial, colule l, melee and marine depositn shemical weawithein th annrma Stranger soda de- rar ODndritio Lake" maximum), whichfacer' aL UtheidMtalewas deosie intamittmtythwegh. and eeelon, en by "devlopet.oil They snmie vloped during the saia intervals of lake desicatid nds to the early Sahoo maximuas of this sepoL no * Lake lohouta and Fall tinm, n"t just e Nedcatbos such as advane and setats of glaise and of degiation, wesker sa& duringte the Ahil suate a fairy rglar decline in ake level fabt.: : theese of the first high-waer Period, as ris NuWalls 1lkes,f eutatieshifth in se level, and reesion intvals nd at othr times soi prolle deils- ism mumV,w"t allnow remotions and cx subsidiary umail believed. chages in typo and rAt of alleviation, Pe" wasting, -pmentwas inappreciable. The soil-forming intervals xiaus. (The data on the 3cMional-lek cecilia- S. Thinolite ta is younger "ea Russll sl devel opme ad eroeloo. Them Cycleesan a wre periodically nepeated pert of whoe climatic; wr desired from studie by the wrtr (Mar- beieved, at 1et in the Caree Dertt REunmll amed te be Ind d by ger climatic cha, irn- e-ulmahinle fluctatlod itemperature tand prcipi- on, 1852a, oasiderbly reinterpreted), by Stanley anclu tha it was formed earlyem the rie of 'F teally worldwide a mynchronons Som Id gn. tatlice-that ar manifest in the Quatenary quencs US), and by Autev himself.) He gave so age of the second Lahotan Lake; Ante, during the erlly emnb gained of the amplitude and duration of of ech are. Theclimacyle, and the depetl 000 years for the maxumu corresponding to that of middle lake Lahontan recession. According to tbe depositional cycles fron the distribution, thickness, cycles and soil-forming intervals induced by them, mmiddle Seboo, *nd 10,00 year for that of the 1t the present study, it was deposited mainly near and lithologic character of the dqepsits. By mtching probably er virtually synchronous over the entire boo. Lik Rail (1388, p. 17e, 178-I7S), tats the minimum of the raion betn the early the uccONr Of them cyces in separate areas, the Siera Nevada-Great Basin-ocky Mountain region Wdeued that ake Labontan dried up fafrly coo- and middle Sehoo lake maxim, although a little eequena of depit that record them can becorrelated. becaue the whole region probably acted a a climatic *sly during ths theral ramum, Which he cale also was deposited neor the end of the middle Long-distance correlation solely by this means is on- unit during the Quaternary, as it doe now. Come- altithernal ags, between 4,00 and 7,00 yearn agO. Sehoo lk founed, hoever, by an uncertainties Commonly quently, the soila are assumed to have formed contain- a published graph of lke fluctatis, howeer, does onecannot be certain that be has correctly identified the poraneoucly, in other words to be virtually time-paral- L indicate complete de elceationof PyrsmId Ike CORRELATION AND Ace OF Tnu QUATUNAIY le, throughout this region. Became they formed DEPOtTS AND SOHL eame depositionai cycle (or poesition in this cycle) in th werecently th lakes such " Pyramid, rinneamem, sequences in dllerent area. Corelation also my be during grenely shorterintervals than the intenoil Walker, wer again inundatedL -AL S of COARICL*ZOI hampered by the complexity of the record in oe ar sediments, the mile ae considered to be more proc" ausinS _ -. . Jona (1914,191329) Corralationof theLahentun Valley prop IndFallen and its meaernes in another, and by mch noclimatio ti-ttaic markes.r n od that WLak ontax had only a mingle lak frmation with late Quatarnar deposits in oear am" Variables as diastrophism Moreover, depositlia .*The stoger soils ar easil recognizable in the me- commening oay ,0 eoso years ago, and he in the Western United State in diffiem became: de- ycles of one type ar not eourily synchronous with cemmon of eac are and ar the most reliable and that all the bech lin and shore depoet. rep- posits comonlye dim lr and geaally ctain the of aWber (cycle of glaciation with cycles of mehnl markers, oving ths salo framerh for cor- oil the maximum or recemional Mage. He o edmiit1y time-paralial marker that peit from all*rition or with eostatie ahifta in see level). Aleo, relatin. T e sediments ad weaker oihlintermdiate that any previous shorelines or shore deposita me ari to another; fosils net Only o geneirally pads (stade() of cycles of the came type may met be in ag betwekn the main sils ar comehlated by Watch- Idelargely obs d and obliterated by this lake maq but ale ac diagneeti. for the small tim spaa emaly Synchnenus froet arm to am (a gives glak ing thse units tht record depoetioital cycles, or parts He aso coneluded tht the pas of the sectionsi involved; iadiocaabo, age datenInatiosme few aod etde probably lasted loes in Montana tha in the of cycls, of similar relative ae and similar climatic t Humboldt d Walker Canyona t atRail Ner soy the Younger pet of lte Quaternary time; Rocy UMountaim of New Meico although its diposits genesis, that is, by matching Inis which roted ealy have similar ltive position in the Ortigraphic me ted IS medial graves mad lower aure clays isad other means of absolute ap determination each as lae ieWwith each othor and with units recording bth ubril (0typical alluvial fan and playc di- nts of increa in salinity in lahe without au" erly gai cycles; Ilawsike- noa WA t", ad tat y the prt designated *a upper (Joese, J. C, 1925, p. 3843, and IW; Van 1r Cmwi.*etn bp peien in "efe*$e At ca aeguaem,- correlated with glaral-roeiol unit Many ef the above scatit can be mialoied by it Is memtry to eaihiai that in using soils for tl ay i trly lastrin;in the Trackee ca- 1814, p. 123), rate of eoneutite of florine in bon, using the positio of reck-stratgraphi units in rea- however, all thebe mnemers are lacusirin. Ie irtee efdeeosien of alluvium and travertis, and rate eorrlatioe, the relative development of the individual toen to si seauen as the primary mna of orreobl- soils In compared, aot their absolute derelopmentL A of the tufa deposition was. war the clo of the if weathering, oil development, or leaching, an hope. ti_, WAusing their posieton in um of depoel. given soil may very onesderably in its abote char. lealy unreliable. Two criteria ae considered tama- tio"alecyleelIn eombination aS econdaryn-me Rich- acteriatls front one ar to ceather yet be ainril in its e eri m th writer's Iat l Ibly reliable and am the principal m of time mon (IS60, 1002) hasobservd tha~t if the suesin degree of development live to the other aet in ech er's conclea"mn the lake hiatory gave no sappoc itratigraphic correlation of vock-etrotigrapihc units of late Qaateroary deposits mad eil in various paitsof ares Regioal correlation csnot be made on the baee onee' intrpretatant of asingle and vary yobm lake sed in this report: (a) the peoition of rink Oaits i tie wetern anited State sueaeopated, the sile how ot a single oil, hecuse it Is aemry to compare m- They agru, heivir, with Most of Email's and VNIQeesious Of dePOSatlnal cyles (WIammifIsed by ee striking ee o thir tiv de d p- qoce of mile of several a in each ar In order to ev's _enelueeisa%althegli they sapplement or I s of lacatrine, glacial, allovial, Andeaian dqepoi. mait mnd their relative ge rations. Frem the cn- determlnerltlvt devlpet. Such cequeneshud them is averal dtails, a follows (4 38): ttion and erosion), and (b) the poeition of mock unite in stntcy eo their telatire deralopuent and ag relations cntn "atltest two *nd preferably te silb that an Contrarv to Ante,. interpretation, but in lin tion toa soil squenes, cenpared in terms of relativ. frwe*ares to area, itiinelriewo tt the moile at ka we moertely r streongly developed, because weakly de- with Rsemal' the lake became completely dry iiratigraphk position (age) and relative degre at soil ock-stratigraphie markers Iron ar*e to area, and the velopd eihs are u*reliable titrt po 'during the middle ALke LAhointan necessi ieeloptarm. Neither of the crite is wholly reliable stogr soils are amogthe best _arkes In mawking thte oaprson, meeore, the elects of loca (Wyemnaha time), at lSt in the (armo Det a*bene,bbut in combinateon they are believed to be th bes The later Quetenmary sratipraphie sudceaseloeof the eovirm tatl factors sust be mialmisad a far as pm- In agreem twith Antern,but t Rusell, th- Irologic meae of correlation available. FoINl Man Careon Desert, Lae Bonneville, and Sierra Xevda biole, pouticuearl dieres, in parent materAl, slop, highest lakesaxxium wasduringlinart main rAther vidne are subsidiary mnot. ares, for eple (plt II), all hav similar sil se- and drinage rgionl Wderents in diOt e the

4 LAKE LAHONTAN: GEOLOOT,CARBON DESERT, NEV. CORRELATION AND AGE OF THE QUATERNARY DEPOSITS AND SOILS III inter.Tahoe-Tioga COXPARISON WITR PREVIOUS CORRELATIONS acipal determinants I soil. The Toyeh soil is correlated Or rate of salt accumulation (Russell, 1885, of soil facies Of strongly de LXKES TLAONTAN AND BONNEVILLE p. 224-227). ped soil. They generally cannot be elininated, but with the post.Lake Bo-neville anD post-Tiogs soils., He concluded that the salinity of water in Pyramid, The foregoing ause they affect ail the soils of a given locality in The deposits intermediate in age between these main differs rather markedly from previous Winnemucca, and Walker Lakes was much less than it ,ilar relative degree, they do not alter the degrees soils are correlated as follows: The Letza formation is correlations of Lakes Lahontan and Bonneville. The should be if these lakes were the concentrated residues previous development of the soils in relation to each other. correlated with the Alpine and Bonneville formations correlations have been based on coincidence of of the former great lake. He therefore postulated a inferred lake cycles; the workers assumed that climatic ro date, soils have been used Successfully only for and the main part of the Provo formation of Hunt (in post-Lake Lahontan interval of complete desiccation, changes caused the lake fluctuations, relation of late Quaternary deposits, generally those Hunt and others, 1953) I in the Lake Bonneville ares, and that these during which the saits were precipitated and largely changes Wisconsin and younger age. This is because pre- anid with deposits of the Tahoe glaciation in the Sierra were synchronous in the two lake basins because buried beneath sediment. The present lakes formed the sconsin soils, sech as the Cocoon is thought to be, Nevada. The Wyemahli formation is correlated with whole area acted during the Pleistocene ass climatic anew after this desiccation, he believed, and their pres- unit, as it does now. These assumptions are accepted, ierally cannot be differentiated except where they the disconformity and subaerial deposits of intra-Provo ent salt content accumulated since that time. Although but the writer disngrees with each buried and in stratigraphic superposition in the age in the Lake Bonneville area and with the discon- of the previous cor- Russell had few chemical or stratigraphic data, sub- relations and interpretations of lake history na exposure. formuity of inter-Tahoe.Tioga age in the Sierra Nevada. on one or sequent studies have confirmed his inferences. The Sehoo and Indian Lakes formations are correlated more points. Previous interpretations of lake history J. C. Jones (1925) later applied this method in more RRELATION OF TIMN COCOON. oEX-CHILL, AND with the uppermost part of the Provo formation in the Lake Lahontan area are compared with the detail, and arrived at nn estimate of about 2,000 years COTEIEsotLS LYNONtTAX VALLEY GROUP, A"D (above the intra-Provo disconformity) in the Lake writer's in a followiuig section, and a similar (op. cit. p. 42, 47) or 3,000 years (op. cit, p. 4) for the FALLON FORMATION, WITl LATE QUATERNARY Bonneville area, and with deposits of the Tioga glacia- analysis for the Lake Bonneville area is in preparation. 26 total age of Lake Lahontan, and about 1,000 years ago 301Ls AND DEPOSITS IN THE LAKE BONNEVILLE, Russell (1885, p. 9) and Gilbert (1690, SIERRA NEVADA, AND MONO LAE AsEAS tion in the Sierra Nevada. The Turupah formation is p. 264, 317) for the lake maximum. Modern stratigraphic correla- correlated with a disconformity between deposits of the agreed that the two lake cycles inferred for each lake tions atd radiocarbon data indicate that these ages are Correlation v.it. the Lake Benneville area and Sierra Tioga glaciation and of the Little of Matthes were synchronous. They followred Xing (1878, p. 524) much too low, probably by a factor of 20 to 50 times. nada.-Correlation by means of soils and deposi- (1942) in the Sierra Nevada. The Fallon formation in believing that this lake history lasted the entire Jones was also in error in assuming that the lakes had nal cycles obviously requires reasonably complete probably correlates with the deposits of Utah Lake Pleistocene, and they correlated the two high-water lake never gone dry silee their inception. -atigraphic information in the separate areas to be cycles with (Bissell, 1962) in the two stages of Cordilleran glaciation in Anteri' estimatee-Antevs Ims presented (1945, rrelated. Adequate data are available for the Lake the Lake Bonneville area and with the West and of continental gliciation in the Central 1948, 1952) a detailed chronology rnneville are, from the reports of Hunt end others the deposits of the of MaItthes in the based on extensive and Eastern States that were then known. geochronologic research. His latest estimates (1952, 953), Bissell (1952, 1962), Jones and Marsell (1955), Sierra Nevada. The first Fallon lake maximurm may Merriam (1917, 1919) concluded that the first high. 1955) place the Bonneville-1nhontan Lake maximum at trdley and others (1957), and Morrison (1961b and correlate with the 4,262-foot strandline above Great water period occurred during Nebraskan time, on the perhaps to enable rather detailed correlation with the late Salt Lake, which Antevs (1952, p. 104) suggests may be 55,000 to G0,000 years ago, the Provo-Dendritic basis of the number of extinct vertibrste fossils sup- (early unternary siccession of the Carson Desert. Lesscorn- the highest stand of this lake during his medithermal Seho) lake maximum about 24,000 years ago, posedly from deposits of this period, but this inter- the middle Sehoo maximum about 18,000, the late Sehoo ete data are available for the Sierra Nevada, in papers age. pretation is questionable (Jones, J. C., 1925, p. 49-50; maximum at 10,000, and the first med ithermal (Fallon) Black-welder (1931), Putnam (1949, 1950), Matthes Correlationwith area.-Putnam (1949) Hubbs and M iller, 1948, p. 24; Schultz and others, Ike maxiim at 3,500 yearsa go. Antevs' nitithermal 1942), and in unpublished field notes by the writer, correlated the oldest high-water hemicycle of ancestral 1951, table 1). At the opposite extreme, J. C. Jones age corresponds Drmitting only generalized correlation. The deposits to Turupah and Toyeh time of this Mono Lake (which he named Lake Russell), represented (1925, 1929) concluded that Lake Lahontan was far report, nid l his medithermnl age to Fallon time. r the intervening areas have not been studied suffi- by a faint shoreline at altitudes of 7,170 to 7,180 feet, younger than the high-water periods of Lake Radioeorbon dating-By the end of 1956 n dozen ently to permit direct tracing of units from one area with the Tahoe stage,and a somewhat lower and freshet Bonneville. another. None of the mountains bordering the Car- published radiocarbon dates were available from youtg high shoreline with the Tioga stage. Thus, the older - Anteve (1945,1948,1952) believed that Lakes Lahon- deposits at four archeologic sites near lake Lohontan n Desert were glaciated during the Pleistocene, the tan and Bonneville both had only twro high-water hemi- lake cycle of Lake Russell presumably correlates with but outside the map area. Figure 39alists themnnd their arest Pleistocene glicintion being in the Sierra Ne- cycles in Wisconsin time and correlated "Lake Lahon- Eetza time of Lake Lahontan, and the younger lake relations to associated ida more than SOmiles to the west, and Lake Lahontan tan proper" with "Lake Bonneville proper" and the deposits and archeologic cultures. cycle with early and (or) middle Sehoo time. The On d not transgress any of the moraines. Tahoe stage, and the "Dendritic Lake" with oLnke the basis of these dates, the arehtcologic chronology younger part of the pumniceous tuff at Mono Craters determined by Heizer (1951, 1956), the estimates by Plate 12 shows the correlations the writer has devel- Prove and the Tingn stage (fig. 38). This overlies the Tioga recessional moraines and may in Antevs (1945,1948, 1952),and the writer's correlations, Ded between the late Quaternary deposits nnd soils of implies correlating the Sehoo formation with the whole part correlnte with the ash parting near the base of the Fniloi tisie isestimntedtola-ve Insted from about 2,000 Lese three areas, and the tw o means of correlation: Provo, and the Eetzn formation with the Bonneville Turupoh formation. formation alone. Antevs inferred only partial reces- B.C. to the prese it, the Toyeh interval from 3,000 or irst, soils of similar relative developments are corre- sions in middle Lake Lahontan and middle Lake Bonne- 2,500 B.C. to about 2,000 B.C., and Turupah time from ted, starting with the three youngest most strongly 5oidt.krth 5v a 4.sad 12595 1-t b eltsr 1s55 a r-, 3ada ville time and he correlated with each other these two 5,500 or 5,000 B.C. to abotit 3,000 or 2,500 B.C. eveloped soils; then, between each main soil, the de- Vuits? taidssi.OsaP. rmesa). UtoC. uoggeut,5 a udriS~tlsal cC ,,st,- (a1 p..tp.c tbf.oat5 I ass? h tti b tk. 1,1to7 lower lake levels, which he called the Thinolite and The bearing of the two oldest, dates, 9,249 Dsits that record depositional cycles of similar size, B.C. at ttroded by tb. V-,. fti.. b .. -Ppdby W.I 1. -(h- ICluuf Stansbury I Lakes, respectively. Leonard rock shelter and 8,950 B.C. r pnrts of .imch cycles, are correlated, as are any w-eakly v.ilp,. A auto, dlm-afo-Itt. a a-f,oat li ..mcdlocl utat-mj at Fishbone Cove, tosDd tctt.nlt bta.-a I..., (.t.l) sad apy., lutt. t lb. ro., Deevey's correlation of the two Inkes (1953, p. 297) on late LAhontan Valley chronology is uncertain, as eveloped soils. tcca1ttcaT, hd taeaio-pty ncd mi ,,s t-tsatati-tr - follows Antevs' interpretation of lake history and his i "eus I IIIes. is u-tl1t1r. I,. ,ses . .,aicdiaeofosc1tt the material directly beneath the dated samples can- The Cocoon soil is correlated with the pre-Lnke Io 011idclltdto lb liplls. .t cc tb. r-~ s~n~. 75b5. di.t correlation. Bonneville soil on the upper pre-Lnke Bonneville tfdleol. ,icatrt.o1." los .il.a-.c .t 0b. r.c.a t.S20. to u5n tbonshca at it 53ho -,ma. ds tesintmai assr assa^. am 4.poo te-S). 1.15. -n.aaelll Ii Wst , 4.350 fist. probabc to EVIDENCE ON ABSOLUTE AGE nat fro ate rotua losu 'lcistocene depceits, and with the inter.Tnihoe-SIerwin -°c i1lct? l ol. rbcar taco till. to- *l ct 4.70 f t, ttlD tlo ol Lut It ttrtso-lthe1 scather Cuso tlc. Sacsatthem," tulda soc. o. atr-- nhit.It Int. itt. ear- talI tI.. l 4,450 tnt. mam1iro It atbOui4.410 fst. meat rscsdo Age from ralo, of jolt occarnvlaiti.-Jtiissell con- aslllo roisod5,ibIa~cl. rioa ad tlt, 1.1rra- oa-Ia eec Di)in the Sierra Nevada. The Churchill soil is corre- bab. 4.55 fes mt,ad t es .00, ti scoot *44i0 ftat. It. cr- Sau -,aite-ld eb .cl... at, oMle, do *t .0ad mal otasetl to- nted with the middle Lake Bonneville soil and the d,,ls,*tton. sideretd deterninigiii the age of Lake Lhontan from the e oaluldsae~ anr sIat~la anidau 1. I ii

LAKE LAHONTAN GEOLOGY, CARSONDESERT, NEV. CORRELATION ANtD AGE Or TNT QUATESRNARDEPOSITS AND SOILS 113 not be correlated accurately. The samples may repre- tions of glaciers in the Sierra Nevada, and that fluctu- sent either the late or the middle Sehoo lake, as they ations of a given ap were similar in relative magnitude lie close to the altitude of the late Sehoo lake maximum. in both lakes and glaciers. Big lake cycles were coeval If these radiocarbon dates are correct, they correlate with big glacial cycles, small lake cycles with sman approximately with the Two Creeks interval (as used glacial cycles (where the records are reasonably coin- by Flint, 1947) of late Wisconsin time in the North- plete), and desiccation intervals with times of degla- Central States, suggesting that the immediately under- ciation. lying sediments of Lake LAhonten (either the den- The stratigraphic records in the lake basins seem to dritic or the lower member of the Sehoo formation) give a more complete account of the lake fluctuations correlate with the Cary substage in the North-Central than those in the mountains give of the glacial oscilla- States. tion. The lake record gives indirect evidence of severd small glacial oscillations not yet recognized in the gla- GENERAL DEDUCTIONS ON LATE QUATERNART COR. cial record. For instance, the two major lake cycles RELATION. CLIMATIC HISTORY. AND SOIL DEVEL- OPMENT IN THE NORTHERN GREAT BASIN AND during Eetza time suggest that the Tahoe stage of ADJOINING MOUNTAINS Blackwelder (1931) in the Sierra Nevada was not a single glaciation, but two, with an intervening short The following general deductions are drawn from glacial recession. Similarly, the 3 lake cycles and 2 re- the data on stratigraphy and climatic history of the cessions during Sehoo time probably were parallel with Carson Desert area, from the correlation of the Quathr- similar oscillations of the mountain glaciers, although nary deposits of this area with those of the Lake Bonne- at present only 2 glacial substages and 1 ville and Sierra Nevada areas, and from the inferred substage are recognized in the correlative Tioga stae lake and glacial fluctuations. of Blackwelder (1931) in the Sierra Nevada. In par- SYNCHIONY OF THE FLUCTUATIONS OF LAKES ticular, the upper member of the Indian Lakes forma- LAXONTAI AND BONNEVILLE tion and Harmon School soil record a time of practically complete lake desiccation and moderate warmth during Plate 12, which correlates the deposits soils, and the later part of Sehoo time; this interval probably was lake and glacial fluctuations of Lake Lahontan, Lake coeval with an interglacial interval in the western cot- Bonneville, and the Sierra Nevada, was constructed dillera, although it has not yet been specifically identi- by first correlating soils of similar relative develop- fied in the glacial record. ment in each area, then between these main soils, cor- The long-lasting desiccation and warmth of Wyema- relating deposits that record depositional cycles of ha-Churchill time, indicated not only by the Carses similar size. If this diagram is correct, it appears that Desert record (p. 90) but. also by that in the Lake Lakes Lahontan and Bonneville fluctuated practically Bonneville area (Bissell, 1952; Durrant, 1952, p. 49'1- in unison; oscillations of similar relative magnitude 496; Jones, D. J.,and Marsell, 1955, p. 98-99), strongly were synchronous whether they were major or minor suggests that this was a time of complete deglaciation lake cycles, or partial or complete lake recessions of the Sierra Nevada and Rocky Mountains-a true in- Differences between the two lakes in relative heights terglacial stage, not merely an interval of partial glacial of lske cycles of the same age occurred mainly because recession as Antevs (1945, 1948, 1952) postulated. Lake Bonneville overflowed during its second, third, and possibly fourth lake maximums If the fluctua- TIKZ AND CLIXATZ IN SOIL FOREXTION2 tions of both lakes were coincident, they could only Tiae.-This investigation has shown that the soils HII I have been due to closely similar climatic changes associated with the late Quaternary deposits are of ev- throughout their combined drainage areas, and the eral geologic ages, each fairly short, distinct, and sep- Ii I i record of climatic changes which is preserved in the arated by long intervals of negligible soil formation. stratigrnphic sections of the lake basins probably is Data on the absolute duration of the older soil opti- IPI representative for a large part of the Western United mums are not available, but the available stratigraphic f. iii ~ States. and chronologic data suggest that the soil optimums were probably shorter than the intervals between than RELATIONS oF TIE LAKES TO MOUNTAIN For instance, no significant soil development took place GLACIATION during the time between the Cocoon end Churchill soil From the correlations diagrammed on plate 12, optimums, yet this interval-all of the Eetza and Wye- it seems that the fluctuations of Lakes Bonneville maha time--was certainly many thousands and prob- and Lahontan were virtually synchronous with oscilla- ably several tens of thousands of years long. Likewise, -I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. A~

. 115 LAKE LARONTAN: GEOLOGY, CARBON DEBERT, NEV. ECONOMSI GEOLOGY pre-Quaternary E, have been covered and lost because of ,he only appreciable weathering profile formed during increasing the rate of soil development than higher there has been no production from 18 N., I 29 .he time between the Churchill and Toyeh optimums precipitation. This would explain why the stronger rocks. field leveling. a 909-foot test eas the very weak Harmon School soil that formed dur- soils formed during the warmer desiccation interv§s, Occurs-es of petrolewre-In 1911-12, TAWaz .J , t t Onl tOTCe) sares O.tt P.e-resw) of well (Timber Lake well) was drilled for the US. (eo- ng a brief optimum; yet according to Antevs' chro- which are correlated with interglacial stages (not with taat-41 go. f Icoiroa VteH, aese .Yes.NM.St~tio (1951, p. 40, 78) has suggested). logical Survey in sec. 30, T. 21 S, R. 30 E., about 14 sology (1955) the whole interval between Churchill and glacial stages, as Moss tAn.aPlu _dd bV R. w. Pth5d, sad I ntom- d5.bO.5. Ottdnb Desert illustrates miles northeast of Fallon, as part of the program of royeh may have been more than 20,000 years long. The The general aridity of the Carson btcna; lzbahrta~yisspte A)5,. itDb stt in the basins of the arid south- royel interval, in contrast, may have been only a few the importance of moisture in soil formation. The exploration for potash this well (Gale, 1913) mentions that sundred years long (fig. 39). During the subsequent lack of soil development during Wyemaha tand Turu- Osasutusasa, maven~ ta~ stit s west. The log of oil spots were observed in the sludge water at five hori- 1,500 years or so to the present, only the very pah times probably was due to the warm parts of these (IMA) 077) Ot. *t9 (47--C4) are of Wl'yemaha and weak I-Drain soil formed, within its optimum of per- intervals being extremely arid, thus severely inhibiting CuS,.,dto~~~~da.-... sliA is titmsBt S .75 tattnul zons. These horizons probably (or) pre-Lake Lahontan Quaternary age. This is the haps several hundred years. chemical weathering processes. Apparently a certain I db..,,it..---.. . 5 ti (t.it' t LiS& 55.5 only substantiated occurrence of petroleum in the area. Many soil scientists consider that the total age of a moderate amount of moisture is needed for active soil tSthydstbSydit. i ass s"te ttisotei3 taa9 SL"o to 1923 there was much excitement over toil (time elapsed since it started to form) is a true forinatiots to take place, but given this critical amount, From 1910 may be less of an accelerant the oil possibilities near Fallon. Several oil companies measure of time as a pedogettic factor. The inferences further increase in moisture _~~~~~ _ dusts, pamubn,,,s. ,O. 24(a) S 0 I and over a dozen test wells were drilled given above do not support this view. A simple dem- of soil fornoation than increase in temperature. The ttlsatsa,.tttb~Rl-S~se-

SELECIED 21: BLIO GRAPW 121 GEOLOGY, CARSON DESERT, NgEV. LMX LAnGNTAN4: Winkle, Walton. 1914, Quality of the surface waters of 1121 - 1889,Quateruary history of Mono Valley. Calfornia; Van Orego: U.S. Geol. Surrey Water.uppty Paper 363, 137 p. ID58,Late Quaternary gttigrapby of the southerm U.S Gol. Surrey 8thAnn. Rept. p.26-14. Knopf, Adolpbi.1 l24.Geology end oredeposits of the Rochester - Vasdenborg.W. 0. 1940.Reconoalsoance of mining dIstricts In Desert (Falton)arealab.], Is ProblemsOf the - l15b. Present and extinct lake, of Nevada: Natl. Geot dlstrct.Nevads .UGeot Starvey Bull.702. 7G278p. Carson tU.S.Bur. Mines lst. Citr. 703. Basisn- BypOsium:Nevada UDI.pL 4-7. Soc.Mon. 1 n. 4. p. 101-130 Alx (s National Geograhlt Churchill County, Ne.: W. C.sad, : 1o.. L. L. 31, S trstlg54Ph7.nd sed Lake LAhootan Erumbe. NevaM, Society, 218 The physiography of the United States: Neo 8193. Lexion of geologic nma"of the United ,-I. Geology of Bidden Care,near FUoS. Wilmartb,. U. mentton: S*aFrancisco, W. M. FreesmanAnd Co, 427 U.S. Geol. Survey BalL 816 Great BaIDlArcheoL Cost. 5th, Nevada Univ., Abstracta York, American Book Co. P.101-13t. gtate, (isciadig Alaska): fapham. H.M Ii.,m , Genesis and morphology of Utedesert Es th oredeposIts otthe Caron Am. Soil Survey A soc. rePt. of12tb ATy teeUI g, -In (ml )ne Schrader, F.C. 1047. Geology and lteLI sad2. soils: Lahostaftslatotigraphty end hIstrLiD h opern-S rept. mtnllscnn fauna from the type section Bull. IS.v.14-2. -1 9615. Lake I Slakquadrangle. Nevada: U.S. Geol.Surrey Yen,Tengehian, 1950, A Caraon Desert (Fall.O) srea. Nevada, in Short Of the Truacee formation:Am. Jour. S8i, v. 248,9 180-10. LaConte JoSeph. 18S9.On the origIn of Dormalfault and of southern, Schulte, C. B.. Loenlnghoecer, 0. C. and Frankforter. V. D., papers in the geologic and hydrologic sciences:U.S. 001. the structure of the Baginregion: Am. Jour. et, S er., 1951.A grapbhi risum4of the Plelalocene ofNebrAska (with Paper424-D. p.D lil-D114. r.3a p.251-26L Survey Prof. notes on the fossil mammalias remasins): Univ. STRATIGRAPHIC SECTIONS. SOIL-PROFILE SECTIONS. New evidence on thehistory of Lake Booneville Lee, W. T and; others, 1915. The Overland Route, with A sIde - 1961hb State Mun. Bull.. V.. no.-641 P. AND WELL LOGS an ara south of Salt Lake City. Utah: U.S. Geol trip to Tellowstone Park, pt. B of Guidebook of the western from Selsmologicat Society of America, 1954, SeIsmoloial notes. FAl- ProLPaper 424-D. p.D125-D127. isthe osstktsa Carses United Staten: U.S. Geol. Su rre Bull. 612, 244 p. Surrey lon.Nevada. July8. 1954:Selsmol. Soc.America Bull. T. 44. T lstz 10-S1,stilrpAic modios I9dlc,Correlation of the deposits of Lakes Lahontan Desert area Loud. L, L_and Harrisgton,M. R, 1929,: Call. - V. 6210-21. Bo unevillemad the giacial sequences of the Sierra forla Unsv.Pub., Am.n Arcbeology and Etlnology., . and ltoceneHtoholdt formation In north- Nevada and Wasatch SMoustsiOs. California, Nevada. and Sharp, R. P., 1032.The 23:1. eastern Nevada: Jour. Geology. .47, no. 2. p. 133-10D. Utah: U.S. Geol.Su reY Prof. Paper 424-D, p.D122-D124. byt reniitg rtopoffrge Loudlrback. 0. D, lD04. BndRange structure of the Hum. S. j5, r. i N., R OEB Erposed A suggested Plelstocene-Reret (Holoene)boun- Simpson, J.If.. 1870. Exploratlons arms the Great Bna nof the bXtdreglonl Ceol.Soc. Aoerica Bull., v. 1S, p. 280-348. - lOd1d, deJftdion Souis; allifude ,8804*fel. Geot. Utah: Washington. EngIneerIng Dept. U.S. Call, dary for the Great tasla regIon, Nevsdn-Utab U.S. Territory of - 11I2t. Btasi Range structure In the Great Basnd: OnnP~. labs and -nian -.. . 2+ 2+* Prof. Paper 242-D, p. D0115-111. Army. Dept. Geol- Sri. Bull., . 14, no. 10, P. Survey fowls Univ. Jatmes, Rtlrhm~od, 0. M4.,sod Hoot, D. B..1VA, Geologic nettIng for the Fallota-StIl Waler 3294375. Morrison, Rt. S.. 6iltulr, Stemmons. C. n..19I7, in behalf of the Iecent: Am. Jour. S cI.,v. 22S, earthqtsunk of 1954: Selsmol. Soc. America Bull..v. 40. no. Ni cDDolmod,J. n, I50,A note on the sge of the Truckee for- Shoo=iscotoryit formation: "eros_1n s'u~rto~e. mstiot: Am. Jour. Si..,v. 248. P. 581-W5.. P. 1SZ--m.3. 1, p. 4-9. Lower member: in the Eden Valleyl WYOt : York Acad. Si. Trans., J., I5. Pleistoene history of 710s*. J. II.. 1901. Early man Smith. U. T. U..1946 Sand dunes: New 1. Clay, olive-green-gra-y. LaUs- Marrell. R. E.. sad Jones. D. Penonyirsoia Univ. Mu05.M~on.. 1It p. to,rer .ordsn Volley.,Utah, to UtahbGrl. So. Guidebooki10. Philadeiphia, nec. tv. 8,no. . p.1l7-1299. ,------,,---- 6. 862 It. C.. anodRI.-t~ts. it. 3.. 1911. Geology trine - Tertiary aod Quaternary geology of the roo4ters Bonsevllle Molter. S. W...Fergsuso. -1153. Ctauolfrotion of sond dunes laebs.] s Capot.Itey. 2. Sand, fine, rust-brown, locally of the Mount Tobluquodrangle, Nevada: U.S. Geol. Surrey bhslo p. 111-120. R. ed.. Deserts actuels et arlens: Ikternat. Geol. Coug. Indurated. Locustrine. Geto. Quad. Mlap GQ-, ogicadclatsfic Uouof oll *truc 1Dth.Algiers 153. Comptes rendur.secr .Pt. 7. p 10. oltveg-re sray, ostra- Matthes, F. E.. 1IM EvIdences of recurrent glacIatIon In the oL 3. Clay, v. 61, pV N uforoe:C. C. 1041. or2,nho codes dismeminsted and in 34 SIerra Nevada of Californit: Science, new ner., Spurr. J. E., lD01.OrigIn and structure of the Basin ranges: tore oIl91Set.. W.1.51.3.u in-thick lenses of fne sand; 950-331.55D-551 Geologic history of the TooctaltO Valley: US G Nolan. T. B., 1943. The Basin and Range province In Utah, GeoL Soc. America Bull, v. 12. P.217-270. Paper loally. A- Yosemite V lee U.S. Gentl Nevda, and Calforade: U.S. Geol. Surer Prof. of Nevada south of the 40th sIbghtly laminated D1930,Geologc bstory ofthUe -190L. Descriptive geology 2+ 10. 2 1I7-D. p.141-190. parallel and adjacent portions of California: U.S. Geol. cuxtrine-__------Surrey Prot.Paper 100. 4. Ash, volssnic. white, altaized. C.. IfD, Plelolene man In Fishbone Cave, Persming 208. -1 D42.Glaciers, in Ntelnner. 0. E.,ed., Physics of the earth, Orr. P. Survey Bull. 10. 3+ Nevada: Nevada State Mus.Dept. Arheology Bull. Lacustrine ------pt. D.Hydrology: New York. McGranw-ill Book Co., pt County, Stanley. G.GM., 10949.Elevastons of some Lake Lbontan sbore- a. Clay, iostir to 3- 11 11. 3* 2.201 1945. 149-219. lines labhs.: Geol. Soc. America Bull. v. 60,P. f. Sand, fine, rust-browrn, abun- W. (L. 19213 Potash sit*. summary for 1212: U.S. Geol. McGee, V ,J.1I£, An obsidian Implement from Plelatcene Pbalen. 8telubrugge. E. V.. and Moran, D. F.. 19V6. Damagecaused by dantostraode. 1aeustrine_ .16 11. 5+ Surrey Mineral Resources U.S., 1912, pt 2. P. 990-8e deposits In Nevada: Amn. Anthropologlat, v. 2, P. 301-12. the earthquskea of July 0, and August 22. 1954: Selsmo. 7. Cla., similar to 3; %in. white W. C.. 1I4., Quatetnary geoglg of the Juno Lake Din Ash parting sbout Sleisrer. 0. E, 1D222.Slap of the Plelstoene lobes of the Basin Putnam. Soc. America Bull.. v.4G. no.1. 15-33. i.3ftvolcmnb below top. Lacustrine.. trict, California: Geol. Soc. America ButL. T. 6 p. 1281- &5.5+ I& 0+ and Itange province asd Its signifcance: Geol. Soc. America Strabore, A. T..and VYu Duyne, Cornellus, 12912.ol Survey of Base not exposed. Bull.. v. 33. p. 541-52. A. the Fallon area, Nevada: U.S. Dept. Agriculture. Field Motto Lake. _ 1950, Moraine and shoreline reintlonship at of Bur. Soils. 100, p. 1417-1516. Merriam. J. C, 1217. An occurrence of mammnlion reatins Operations Geol. Soc. America Butlt. .61. no. 2. p. 115-122. In a Plelotoemr take deposit at Astor Pra, near Pyramid California: Thayer. T .P., 1937. Petrology of later Tertlary and Qusternary Bult, v. 6tOfedt Sousi e W' cer.see. 21, T. I N.. R. t9 E. Agrrr Lake, Nevada: Calfornsia UnIr. Dept GeoL Sri. rocks of the north-ceotrat Casede Slosntalns In Oregon, Remit. Richard. 1Jim, rrerecm.tl55a algae and stromatolilPS Nevada: Geol. Sec. et SosIAWNd of Caeosn Sisak 8. tie.21. Ev8, esce of mammsli~n pateontotug) relating ~, la*bs. to Iesumente de toe TrabaJor Preseniados: InternUt. with notes on similar rocks In western Aole at south edge of plays emiemr/ Geol. Cong.. 20th. Mexico aCiy 045. P. 124. p. ottitde 3.888A 4Jject. 1d10 &,5 - 919, Evidence of mammal.n puleontotogy rebting to America Bull.. v. 48, 1048-165. Geol. the age of Lake Lnhontan: CalIfornIa UnIv. Dep4. Thompson. 0. A., 1952. Rasin and Range atructure south of ltRchmond.G. H, 120. Interotadnal roinl as p sGhle1 srll5c v. G, p ScL.Bullt v. 10 o. 25. Reno. Nevada labke]: Geol. Soc. America Bull., Fallon formation: n Ini Wisconsin chrotsoloy abe.): Geol. S12. Upper member: Mlilter.RtIt,. 140. Correlstion between tsh distribution and rgraphtrkoric Altric Boltu.. v.61. no.122Pt.p 1427.l te. Clay, ally, saline, light-gray. Dis- I'letetoente hydrography In eastern California and south. _ 195G, Geology of the Virginia City qundrangle, Nevada: -1102. Quaternary strati8rCphy of the La F51Mountaiss tontinwouolag gravel on urface: western Nevada. with a map of the Inelstocete water: U.S. Geol. 8urrey ButL 1042-C, P. 45-75. U.S. Geol. Surrey Prof. Paper A1C4.1m50P. fragments of tan lthoid tufa (hasln- Jour. Geology, 54.p. 43-5L Utah: I Toeber. Don. 1056. Movement on the Rainbw Mountain fault: strotleaphy of Lake Lahonton andO Richmond, 0. SI.. aod Frye J. C.. 19'7, Status Of soils In 'astrti interior lithoid tufm of lower mem- morrivo. Rt.B.. was21 Selimol. Soc. America Bull.. V. 40. no. 1.P, 10-14. hr of Schoo formation). Lacus- omenclature INote 19 fur Am. Com. on StrAtG I deposits in the Caruon Desert are graphIc Bull.. v. of Agriculture. 1941. Climate snd man: U.S. 0.8+O associated Quatersary Soc. America Bull. . M.~s Nomoencltaure]: Am. Aaone, Petroleum Geolog Isis U.S. Department trine ,-.. ,___.... 5+ sear Fallon. Nevada lake.) : Geol. Dept. Agriculture Yearbonk. l3l. 41.on. 4,. .718-799 II Agri- Disconformity. Do.12. Pt..ZP, - 1951.Soli surrey manunl Jrevised ed.): U.S. Dept. Wyemaho formation: T. W.. mud FrederIcks. 3. C. 11 148. Groundwat4P Is - IDS2b. Late Quatersary ctimatIc history of the north. Iobins. i culture. Agriculture Handbha. 18, S3 P. Ssnd, medium, rell-morted, deep-ruty- Valley. Nevada: Nevada Water Reourc Bult 2 Basin lobe.: Geol. Soc. America Bull, v, s. Loveloek I111-Ot Townsoip topographic maps yellow In upper part, downtard more rna Great 11 0 iauued by, the Office,of the State Esgiseer. U.S. ReelamationService. Do. 12. Pt. 2. P,. 7. of the Truckee.Caron Project: U.S. Reelasatim Service mugCr-holit logs, soil. RtuaOwl.1. C.. 188. A geological retennsais"An In southerna -litto , Stratittvaphic sections. Hydro. Br. iformerly under 1'.. Grri. Survey, now U.8. and momcalcium re ay.orebonnte-mrted Fome-hat llmonlU-, in Geot. Survey 4th Ann. Rept.. p. 43.-484 Profie neeties, and driller logo of weltls dirlled for water Oregon: U.S. upper few inches. Larustrine - 2.+ 3. 0* SA osnl aurrQuateM nary Bur. Reclsmation), i ar . - 19 .Geolgical hie tory of lAke oil, sad vst arel sua In the southrern C o, Itn rert Nevada: U.S. Geol. Surrey lion. 11. n-a 11attoa Nevad. ; U.S. Ceol. Survey pent9.ilerePt take of northweitern I . . -. .. . . 1. I I 'JIMMEMP,

LA" LAHONTAN: GEOLOGY, CARBON DESERT, NEV. STRATIGORAPEC SECSIONS, SOIL-PROFtLE SEMTIONS, ANDBWELL lOGS 123

TAtLz 10-Sairsatipdhic secliots-Contlnued XTaaLz J10.-Str geapibpicasntisContlnoed TAsLe 10.-SMeaiprsphie sdiscts-Coatinued TAaaz lS--Strairmphicis atssD-Coanuaed abs forsatlon-Continued nkt NE% sec.33, T. *1.M., R. 10 S. Stertirophic section*epote Unoonfortotty representing ubaeril erositon ftsksoa ape,s SW34SR)4sac. SI, T. So it, f. 55 B. Sfrolaphic soteft sand,medium, some coarse osadand grIlt, en souWAids of sfslisin asout534 ub of lYssWn'vg fiehoo formation: (a) (er r"psd is scarp of deep deflatio basin,sad ofor auc Ufa at somewhat silty and clayey; many dark Laks. Top dofsecion, saisthe 3,555+5 feeL upper member: banr e arp. Top f setti, afitWlar rabasw3,DSOfs#t. basaltic or sndesitle granules; dark Fallon formation andlor) Turupab formation: itSi si) Sand, very fine,ta; some Iron oxide brown-gray. Lacut trl n e-. -. 5 :-6+ 1. Sand,fine to medium, dark-gray, much nodle. Lacustrie -.- .-.- 0-1+ &4* Fallun formastlon: rhsaassrts s) Dsjd(lass) Ike above but less silty and elaycy, and coarse sand sod aronules,brown- clay, brown; gradational loner Sand, fine, coarse snd, sod granule better sorted ...... - _ 6 &.0+ gray and black lImestone fragments. boundary. Lasostrinet ak &&------4+ sand, a few pebble to 4 1.. In di. ,nd, fine, and silty fioe, dark-gray. La- losa2------.0 2 Indian Lakesformation: mneter,rarely %in, even at eAt cuatri e ------&5* Disconformity. Upper toague: Of duns; eronabeddEd. n. &ehooformation: lay and silty clay, dark-gray to nearly D.6'c Clay, eiity, very blaek, highly ear- lower member: Disvonformlty. black. Lacustlne banaeeous; marsh or swamp -.- - - 1. 0 7 6+ 2. Clay, medium- to dwrk-olIve-gray; snd, medium, some oanse,very elayey fluviolacuatrine or lacuatrine de- Turupsh formation, bearing Toysh soil blocky; ostrsaodes; some len- posit . -.-- t_------9+4 (elsy decrease.downward, sand becomes titular partings of ostaecode- (eroded): very gray. 1.0 Disconformity. cdIner); durk Lcusstrine ail rich fiseesand as much ss 34In. Sand, like above, eolian, bearing C. S&hooformation: fte not reAched. thick. Lacustrine .- &.- 0 7 horiron (eroded) of Toyeb oil; 0-2 3. Sand,fine, tan; Iseustrine - 05 7. 05 Dendritic member: in. loeally eroded) white layer at 4. Cloy, -me As 2-I-- , 1 7.15 Clay, sandy, about 5 percent sand top that may be partly volcanic sub S. Sand, luminated yellowIsh-hrown, in top 3 ft, grades lea sandy but hbamuch roil calcium carbonte. doswnwrd; olie green, has tur- a-s.a . gray, and black, poorly sorted, BRsl I in. of unit loally coat well-tIdurtted, laminse ' iS5n, quoise blotchs. Lucuutcine---- 1.5+ &4+ rt ined_.. 0.8-1. 0 9+ probubly bassith Lacuetcine 25 7. 4 Clay, bluish-green having rusty i,Nll3i sc. S0, T. 21, N., R. SOB. Strstgrophir cefairn 6. Clsy, nameso 2, blocky ti lsoi- blotches;ostruecodes Lacustrine. 1 5+ P 9+ Dmofurormdty. nated; some brown and block I in restbunk of C-reo Rico, (ntificiol cot to traighten Clay, sandy, olive-green having Seboo formation: Top of section, oilicadc 8,85f+65fos. staining on fraetres. Locus- teal-hlue blotches; 15 to 20 per- trine- . 1 9 9. 3 cent mnd; lacustrlne .1+ 11.4 Upper memtober: 7. Ash, volcanIc, ait-alred, white to Base not enposed. Clay, silty, and sand, very San, lormatlwn: pale-gray. Lurustrine . 25 P 55 clean, puke-tan-gray to newly S. Clay, sane nso2 . 1.0 1Q35 aer member: (/d) (1,) white; mottled with white soil 9. Sand,fine, tan, brown and orange- Clay, olive-grmen-gray; ostracods. calcium carbonate (lower part brown, laminated; ostrarodes, 5rta.. 5 Lacuslrine 2-2.5 253 of C.. borflon of Toyeh oil). abundant. Lacustrice 15 10.7 Lanustrine _------I 0t 05-0. 2 9S Sand, brown to gray, lamiouted, 1o. any, some as 2-. , 7 It. 4 N-N S.e. 14, T. e0 N., R. f E. feCnaeeaectisa t posedin lminare M. to 34In. Locuotrieo- .3 z 8* 11. Ash, volcanic, white - Line Irarpat scr, edge of largsrdrlfotin plain, 1X mites soth af Uprol Sand, mostly fone; 1-3 In. poorly Clay, olive-green-gray; celcorodes, 12. Clay, salmes 2. - 1.4 12-S NDIlcac. Top af section, altitude 8,967+± fret. sorted, coarae,medium, and fine some pebbles to 5YIa. dinnmeter; 13. Ash, volcanic, white Line sand locally at top and ban. Parallel bedded. Probably Is brown ntrining along froeturra; 14. Clay, same as 2 ...... , 0 l6 8 priomntic joint og. lscotrine. 2-3 5 Itr Wyrmaha formation: Ftallon and Turupah formation: lteo tIha orntrin .- _-.-. 7...... 7f 9.57+ Ash, volcanle, si-sired, white. L- 1. Sand, fine, rutt-brown (beoenot nx- Sand,fine-medlum, meldium, and coarse; Dlaconformity:undulatingermtion some granule and sts-all pebbles lo- eustrine ...... 6 &7+1 posed). tacastrne - -,, 1. 0 17.8 sturace. eally; loose to locally smi-indurated; Sand, medium, yellow-brown, Clay, olive-seren-gery; ontratodes. somewhst croshedded. Eolian Lucustrine. _-,-.-_ STIT. ee. 15, T. to N., R. 10 B. Cesleraf aetiss is bask of 10+C 10+ slightly cemented; seems,to 1.0 6t 7f Dioconformity. Sand, medium, brown; ostraode. cnannelcociniag Likes sad PoposseLote; top, alticate about bear IncIpient soil (top Is non- iScho formation: ealcareous, lower part seemsto Ia.u.trlne . . . 0. V.06fet. I 18 9+ have some soil calcium earbon- Cly, olive-green-g,.y, somewhat Fallon f-rmation: ('tee. led) Lower member: Sa,,d, coarse,medium, and fine (highly Qay and silt, light- to mediumtgray, ate concentration). Parallel Inminated, slightly mottled, brown bedded. Larcatrine ...... -... I-t 5 10+ along faeturea; a few lenticulur qu-ttooe), looa.e (uncemented). seml-Indurated well-bedded. ortraeode coquinaspartings, two Eolon and . -0.1+ &e 1 Lnceustrine 17+ 811t,sandy, and sand, silty, dark- while solcanale-ah psrtingo 7 und Disconformity. WyemAha formation; chocolate-brawn, much soil cal- ciumearbonate; parallelbedded. 17 In. from top. Lacuatrine. 3 Turupth formation, bearing Toyeb soil Sand, medium and fine, yellow to 6 13 2+ Lacustrine -. 0.4+ la.4+ early level, regular contoct. (eroded): medIum-gray, wella-orted, well-bed- Sand, very fine, fine, sandmedium and ded, poorly coasolidoled. LJustrine. 24 + Discottformity. . formatin; coarls pebbly Sand, intebedded; Sand, fine, silt, ome cloy, thinly Inter- 7:+ t, medium, well-sorted, light- to slightly micareous; pebbls rarely to edium-gray, mottled runty yellow; bedded. Lacuetrive 2av4 Indian Lakesformation (oTlate Sebeo and 34 In. diameter; Iron and manganese Sand, coarte, medium, and fine, inter- Indian Lakes age): ,prrr It. box several daok-brown stsins Is coars beds; strongly eross- trntode-rleh partings.ielow, lorgIly bedded; dark-gray, highly andesitle Sand, fine-medium, light-gray; eolisa. bedded. Eolica. Top several Inches nr bassltle; genersily well Indurated, acts pgains; wide variety of rork- poorly sorted, wIth modenrat soil Top I ft ha some coase and; mid- penIn nosqolarte faction, altoils to well-bedded Laemstite. Plroabsly dle 0.3 to I ft is sightly cemented sclclum earbonate concentrslion rorretiVe with late ruptiona at ose In present bed of CocoonItivr. (ended C.. horizon of Toyeh soil); with calcium carbonate, oaerlie 10+* 39 t 'Cu.tle ...... 2+ 15 2. remainder s moderately ell sorted lipoal lioghbek. very Inning-.. erosion surfese; lower not enposed. and Iret of calium carbona-- 2- 3 2- 4 Bar sot esposed 0.5 to 1.2 ft 0unsemented- 3+ 1 4+

-I i E __

LAKE LAHONTAN: 61COLOOT,CAH8ON DEBERI', NE~V. STtATIORtAP"mC SFtMONS, SOIL-?I tOFILE SEcrsONS, AND WELL LOGS 125 Touts l0.-&,stiraphisceedloss-Continved TAmLg IO.-Bernffgrsphic sectiesne-Continued TAXLX 10-Smlrspeophic soctioesr-Costioued T Ata L0.-Strsiiasaphsisectios-Ccontinued _IIN. T _-45saasd Saseirso5_--dasdss 22kk- . 5 formatIon: kftkas, Pe-a ]aSs - t~iol) Beboa formatlon-Conulnuod (/l ) Sebon formation-Continued Volcanic mud complexof Soda Lake-Con. T s Do, Jpper member: Lower member-Continued Upper member: Contact peony exposed. Sand, fioe, wndl-oorted,parallel- Clay, silty, sem-indurated, me. "4 Sand, medium, some loue-medium, Part of middle Sebooad IndlanSLakes age: bedded. Lacustrine _- __ .4* 13 S dium-gray; weUlbedded; oatra- and- coarse, granule-bearing ecdes. Lacustrlne; Frades to 2. Sand, Course, and granule sand, Silt, and s nd, very one; top In. ) ecasme; rare fragments of early with several percent of basaltic brows-pay to medium-gray clayey slt and silty cay near 1ithold tufa of upper member of base ___------_.----_ 7.5*- 32.0* lapilhi; some very small baalt silt having wry fne sand part. Sebo. LacustriSne. Mostly pebbles; well-orted, nearly un. lnog; middle 7 In. is light-griy Sharp, even, conformable contact poorly con olidated; bedding Indurated, moderately to well 8*+ very fine sad; bottom t In. Is Wysmha formation: lenticular, locally croubedded.- 2* bedded; probably acustritne --- a. 5 41 Silt and a little very fine sand, Band, medium and fine-medlum, some Fairly basp, Dearly level contact. laminated dark brown pray, interbedded fine sand; moderate Sand, fine-medium and fine, S. Lapihand and granule sad; com- dark gray. some medium gray yellowish brows (IOYR 8/4) topale. thinly bedded; upper hel monSly more than 20 percent and light grey. Lacustrine-- 1. 5 16 3* pray (particularly yellowlsh in upper ripple-crosnlamlnated, strongly basaltic IIpill and with some part). Probably al lacuntrine. so in top 2 in.; lower half sl- basaltic pebbles, mostly less than Disronformlty, undulating ero- moit paralel bedded; ripple sion surface. Baes not reached .__._-_ 7 42:k iSn. diameter, but rarely to marks approxlmately symmet- several inches diameter (bombs) Sand, flOe,and fone-medium, well. rcal. A few nemnil nodules of sorted, of in some beds; lower part mostly some portings baSal- medium-brown lithold tuae In tlc(?) sand, posnibly from Sods welisorted, low to silt and rels- 5.00.5 5 top half; some fragments of Lake eruptions; lowest I ft his tinvy unindurated; upper part is white early ithold tuts of this moderately sorted, somewhat to some coare sand; local %4.Io member in lower half, especially somewhat ermented light-gray Type iesli fo sleruppeersnestkeref Sehsof f.rmion. Esposetw very silty, somewhat Indurated, in oorrne pit at north ersep of dlfflioss basin. shoal 100/ d seol at base. Lacustrine ----- il 9 6 84 forms small Cliffslocally. Con- very fine snd (ash?) parting Sharp, somewhat undulating contart; at base _- - 4* 19.3* of Fllon-L lelrk csutoffroad, in SEB NIVy, sec. St, T. 10 N., R. tains rre watetworn fragments 99 B.; tep of senior, altiiude bonul3,995°5 feel. disconformity; in places cuts bed- of dendritic and lithoid tura. ronformity. ding in underlying lake clay. Lacustrine . _.__. 37 8& 6 155As- Z("a Lower member: Dendritle member(?), possibly bearing Falios formation: 1VW55 tbd Clay, mostly silty, .ery light olive Sharp conformable contact. Harmon School soil (eroded): Sand, Bune,medium, snd coarse, pale- gray; lower 2 t Is pole-gray sit. Saod, coarse and medium, frag- yellow-gray, poorly sorted, loally Well parallel bedded. Laces- 4. Silt and sandy silt, ifght-my, very ments of pale-gry platy tith- crorsbedded. Eollan. (Northward trine. PrSsmatic jointing, poorly sorted;ay beds contain old tuft 0.1 In. thick; medium- thickens to mom than 10 it and Io which becomes closer In top several percent of bsaltic lapDlI brown, slightly indurated and underlain by several feet of Collar few inche; sand dikelete in (sand-, granule-, and small- cemented wetscalcium Carbon- mand of the Turupab formation, some joints. Top several pebble-ssed); somewhat Indu- ate; possibly bean eroded weak which bears the Toyeh soii) ._-._ Inches appear slightly weath- rated; lseustrine ..- _-___, 2.2 8527 soil. Larusrune . .3* 19864 ered (clay is discolored and Deodritic membnrr Disconformity. fragmented); possibly lower Sharp contact, porsible mInor diconform- Sand, very flne, and fine, welt- Sehoo formation: : part of Harmon Sohool cal.. 5-7 12 S* tty. Upper member (bearing Toyeh soil, sorted, uniodureted, mieaeous, * I lherp,kvel, conformable contact. 5. Sand, IpMli; very fine pebbly me- pale.gay; ie and fiourtike. slightly eroded): Wyemnah formation: dium sand, very poorly sorted, Sand, coarse and medium, con- Lacustrine ...... 5e 2|1I* Sasd, medium, light-brornish-yellow, grayish-yellow-brown, slightly In- taining much granule sand and well-sorted, incoherent. Well parei- durated, IndistInctly bedded; Sift, light-tao-gray, weLl-sorted. some pebbles (mostly less than LacuatrioD...... 3 2044 let bedded. Lscnutrne - 2 1428* Y. In., some to X in., and rarely probably coDlurbum (lope wash Base not exposed. or talus). (At neXt embaynsent lkt. clayey, sed clay, silty, Inter- about I In. diameter); rather of bluff to the sast, this unit Is bedded, light to medium-gray. poorly sorted, Indistinctly bed- Lacustrisne .. .3* 2017l SWO6SW1 .se. 8, T. 19 A1., R. f8 e. Blaff ass snilAest nide somewhat more Indurated, yel. ded. Lacustrine. Granules of Sads Lake, frons creat olfride to ake hoe; sisad. of rid#e lower and locally shows alight Silt, pale-gray. and interbedded and pebbles mostly late lithold very fOne sandy silt to clayey eal sboat 4,085 feet. calcium carbonate Concentration iufa of upper member of Sehoo, at top.) ...... 3 82.7 Silt.------2.6 23.S* medium to dark gray or dark Volcanic nsadcomplex of Soda Lake; tjsl tea Sand, very fte, well-sorted, pale- brown 6ray; ram fragments of Part of late Sehoo and Indian Lakes age, Gradational Contact. .2 2& BSk white early U1tholdtufa of this bearing Toyeh soil: pay - S. lapill; mostly coarse, fioe. member and of volcanic and I. Sand, Inpilli; poorly sorted uncon- Sand, Dendritle memberff): Pebbly, and granule sand, some Silt sod very nte sandy silt, granitic rock. Top 2-4 In. Is solidoted silty sand containing slightly rcherent, light-gray, onxide(B) boriron of Toydl soil several percent of basaltic lapili medium sand, especially in upper (pH 6.8 by colorimetric field and a few larger basaltic bombs, 2 ft; generally well sorted; practi- Laclutsie .------IL Ok 26.54 cally all basaltic UpOI; pebbles Lower member: test): next 9-10 in. Is C,. hori- very rsrely s Muths , I ft in son of this soil (partly eements diameter; generally indistinctly motly lees than 34In., rarely to Slit. clayey, somewhat mlareoas; I In.; slightly Indurated; Con- oitracoded; ome selenite; me- the sand; pH 8.0-8.5). 2*1 4*k bedded; poorly exposed; prob- ably subacrIl. Top I t some. tatus oscxslosl waterrorn frag- dium-pry: thinly laminated, Contact gradational to sharp, some. ments of dendritic and lithoid ormiroherebt, hSsile. Lacus- what undulating; local disconform- what Indurated by caleareous horison (rroded) of the Toyeh utsf. LACUStrine...... 5b 94.2 trint------IO.* 27.5* Ity. soi- J38 38 Sharp conformable contact.

f U- - -- -

126 iKE LABONTAN-f GEOLOGY, CARSON DESERT, 21EV. STRATIORAPC SE13IONS, SOIL-PROMILE SECTIONS, AND WELL LOGS 127 Tast 10--Steafivraphie wtioae-Coutinued .TAipa 10.-Stmufsgaphic ..ctiorn-Contioued TANt" IO.-Stafig-aphic asctian.-Continued TAscz lO.-Sfratfesphie et-im-C ostinteed - as tic t.d-.siad St-sica I5-Cs.inAd r1' Volcanic tand compleof idsodLake-Cons. T sck) Dt)ha Wyemahtformation-Costinued shkkoe- 7Doeth Disconformity. ekn... Doati fre) ItresII Wyermhat fornsatlon-Oostiued aatues Depth Part of middle ieboo and Indian Lakes Disconformity. Sehoo formation: IIndl (/ceti a6e-Continued - : 4. Rond, medlum. wellorted, light- IS. Sand, medium, clean, medium.yel- 7. Sit, nedi ayhhbrw, well- gray; botitottlly parallel bedded; Upper men ber: low-brown; h in. fne sand, morted,unindurated;thfin rspidly 2- to 3-in. *st layer at bae. Len- 3. Gramuleand and coaose sand, light-gay, At base. Ltacn- westward and Is only 3fit thikc tilar and locally absent. Lacus- plakinb-gray, very well wort- a 14.9* lt10 to West. Lacustrine- 1.3 95,.5 trinet------0-1 7. 5 ed rkonle; tome small peb- 10. Sand, coarse-emedum, veryses.I we Angular disconformrty. Disconformity. bie to rarely 34In. diameter, esoted, pale-gray., tAcusain 3 1. 2+ Part of early School?) and Indian Lkes 8. Sand, medlum, some Oineand ooarse, typical Carson tsser assun- i7. Sand, fne, 4 to I tn. at top; re- age; well.orted, light-ray, strongly blage; also many thin platy maloder coase medium sand S. Sand, ltp~ll;moderately indurated, erosabedded (beds dip northward). fragment. of dark-p-rplish- And medium sand; light yellow- moderately rcll bedded, parallel Probably colion1 ,_ I a 6± red tuts. Top 3-4 In. some- brown. Lacuatrine. Ba"e not bedded; dips 20-30' northwet- I what cemented by calcium expoed.______1 S+ 17.7* S. Sand, medium, lightS".ay, welleorted; ward;strogly jointed. Contai.s fiat parallel bedded. Probably carbonate and slightly dark- several percent of bhaltic lapilli i colan . .. 1 ± 10. 1 er; lower part is uncemented. 1 in poorly eorted sfty medium to 7. Sand, medium, welleorted, strongly Ltcustrine (deltsic) - 2. 2 7. 2* conre r;nd, and commonly tome crousbedded (beds dip northward). 4. Sand, fine, and silty, light grit, emall-pebblelted lhpDII, npe locaflty of upper tongue of ndiian Eon -1. browvnsh-yellow. Lacus- Lakce joessation ond rnd rare cobble-aixtd basalt 5± 11. 6± . MnDmon&hsool eil: S milr norlh ofold Hor n Schoof,S1%1N 117 trine _ ,- - 3 bombs. Lncutrin. B- not 8. Sand, medium, wellsorted; fiat pur- 7. 4± sv, 24, T. 19 N., Rt.*9 S. Erposid in baste of a beunoh i-riu- erpowd; thirkens to several fet, alkl bedded. Eollan or knustrine. Disconformity representing upper ias .n..f about 160 fret cout of county road bridge areas. main tongue locally as munh t 15It; esp.oed (Bore not exposed) 3+ 11 .6i of Indian Lakes formation. irrigationralt rep of errtionol attitudr of shout 1,9:1* 4 fret. sbove wator within 400 It to Basti is Sharp undulting contact; recorde ub- &e ntfo oil profite 17 S (tibnk 1*) l lAtisfeafity. west .. . I 96. 5 serial erosion. Sehoo formation: NBI4S)3el, ec. St. T. 19 N., R. Z9 B. Stoutigaphuk ectioe Lower member: nposed Upper member (bearing toyrh soi): I/mci-s, /e by frech and pi4 untoasou nk ccarp or eda side of 5, Clay, silty, and nonsilty, I(ttl) ~l)" Ne3,NE)j see. 17, T. 19 N., R. t9 e. SftetigrspAic *edion me. Silt and fine sand, thinly Inr- sa.InaIWfley, half a il. east of S-Lime Reermoir; top of section, : I dlum-gray, faint greenish ropoesd in rireobnak of -edveal ol Cue.on Rime,ood plain. altitude 3,965 bedded. Lacustrine. Upper 3.5 feel. cst; tough, sfitfude 6.946* feet. . moderately in. in. light gray, having vesicular sottex, eec Drp,t durated, faintly Turopoh foemmtion, Fallon formation: -Uet I (1/ces laminated; structure (mislculr boArlon of bearing Toyth con: set) .o primat jointing; 1. Srnd, mediumight-gy. Ttwoport, 1. Band, medium and coarse, pale-tan- tome Toyeh so); remainder Is light oetracods. undulaling diconforsuity beta-er: gray, loose and uncemented; 16 Laouatrlne---- 2-2 5 9.6* brown, having weekly columnar upper part, 0.5-3 ft think, is ladle- percent dark-gray fragmenta of Sharp even cotant. to granular struature; slighUy to tate Uthold tuot tinotly bedded; loer part, 0.5-3 ft of upper member Wyemoas, formation: moderatey calcareows (B and thick, is emobedded, contain. some of Sehoo, Including thin tabular upper part of C,. hoerlom of coarse sand *nd grit, *nd many tufts ones%4 to Y, In. wide; Indistinctly 6. Sand, medium, wei-orted, uDce- Toyeh so.oD) -- 1I 1I fragment.. Eulian. Brosn Toyeh stratified. EOln-D 3 3 mented, brlght-orange-yellow; Irregular contact. oDi;top several Inohes (oxide hor- Sharp contact; diconformity. ripple-bedded. Lacustrine...- 1. 3 109* Lthbold tuft, white to pale gray son) are almost unidurated; un- Turuph tormatilon (hernlg Toyeh soil): 7. Sand, very coarse, c ean, pale-gray. (early lithold tuts of thin mem- derlying material has moderate to 2. Sand, medium and monse, some- LAcustrine . 1 - I11.1 ber), nearly sontinuour layer of weak calcium carbonate coneentra- wbht silty, poorly sorted, Indis- . Sand, fine medium, irregular to smmilary mases, lin (calearcous horlmon)to 14-1i tinctly bedded; some tuft frag- clean, pale- commonly I to 2 ft In diameter yellow-brown-gray. in. deplh . . .*. ment. EWlan. Top 1.3 ft bear. LAru- and 0.2 to 0.8 ft think . .- trlne -. _ . .3 .5b 1. 5 Pronounced disconformity, slightly undulat- Toyeh soll, which locally i. some- 11 4* Disconformhty; fairly sharp contact ing. crosscut. bedding in underlying unit. what eroded; vesicular boriron t 9. Silt or silty clay, medium-browrn. Indian Lakes formation: Sehoo formation: locally absent; oxide borton Is gray6. Ltaustrise-, -,, ,5 11. 4 Upper member (bearing Harmon Sbseol l oser member: In. 2-5 thbick,grayish-brown, ron- 10. Sand, fine-medium, clean, pale- si): 2. Sft. clayey, pale-gray. Several taminng a little uenutiloncsated bruwn-gray; irregular parting Colluvlum, composed of fragment. ostraoode-rtoh sand partings in clayey slDt, little or no calcium of sit at base. LAcustrine-_ 1 of underlying clsy. Top 0-2 in. upper Part; SID.aboe baxe iS carbonate; moderate woae col- II.o* II. Send, fine-medium, clean, ple- light brown (onide horson of persbtent W-n.partieg of slty umnar structure, bhad conaist- Harmon School to); remainder Iscustle llmeutone; brown-gray. LaUotrie, -.. 3 abundant enoe;.gradu-i boundary; remain- 11. 9* in light olive gray; has very weak worm-bering tubules below the Ing 8-11 in. are caleareous hori- 12. Silt and clayey silt. medium.-yel. calcium carbonate conrentration limestone psrting. Lacustin.e 1.4± 4 4t son; pinkbsh-gray, moderately low-brown-gray. IAceotrine. 3 In upper 0.7 ft (C_ bhoriso of Flat, eonformable contact. ealcareous, moderately cemented, 12 2* IS. Send, medium and same toi).------...------.. 3* 4. 5 Wyemahs formstion: hard - One-medium, consistence, containing Disonformity. 3. Sand, fine, sDty, many white powdery calcium car- chean, pale-brann-gray. tans- mostly; some sit Sehoo formation: partings and thin beds of coarse- bonate concentratlons; slightly t-lne - ... ------2 11 4* Dendritis member: medium and. Strongly ripple- columnar to granular structure; 14. Silt, clayey slt, silly clay and fne Clay, marked and myer lorally broken s gradual lower boundary. State- send In aiter..te layers; I In. silty, and cayey silt, llght-otive gray; strong columnar if by wa action In h1low uler. rba below soil In light bhowoitb clay at bae; medium-yellow. Jointing; point. closer spaced in top I k t. Abunduntworsmlulboeu.aruistriee. 2.2* S 5* gray, very wt kly Indurated... 1. 5-2 2 5,0* I brown-gray. Lacuscrine - 7 14. 1* Lacustrine. Bae not exposed--- 1.S *b5-M3 0-64-10 _7 _--_ I -' - O

LAEE LAHtONrAX: GEOLOGY, CARBSONDESERT, N1EV. STRATJORAPBiC SECTIONS, 01L-?itOFILE SECTIONS, AND WELL LOGS 129 Tol.. IO.S4rsatiqphjc rsotgi -Continuedt TAsac10.-Sirafigraphic s-ctions-Conutfaed TAbLa 10.-Stratigraphie oectinns-Contlaued TASLU10.-StratilrapWfc ssti o ntlnued Sata 15 f Sanit. tza.-Csathad ByVSEy .e. s6, T. 19 N., R. Fallon forsnstIon--attnust d Toidis Deah$ R. x9 Strtifraphic ssctio Falloo formAtlowDnContuinude Beshooformation: I ti eed is bank of drai..Rg ceanl, rad in 6ttfot Guaer Aole, Probably first lake unit: - - ! in 4 Lower membet-ontinued Upper member: of ecod Fdolo fake. Topo s(ion,oltitudo S,9!1 )'rt. 4. Sgt, elayey, llve-drxnb. Lcuso dt 4. Clay, ao-gray, witbout e lclum , Clay, emottled-blackto olIve-i. Dn formation: trioe .... ------4-1 earbonatenodules. Lacustrine. .- 63 5. Sand, ine, silty In top 0.1 ft, clea" trine ...... _-----...... 1.2 4.2 Second lake unit (bearing 'L" Drain u.... 415001 8 Clay, silty, black mottled with tan. Dendritie memaber: below: tan and tan-gray. Lcus- -3 soi): lecustrine ...... 65 7. Clay, olive, wfthrusty spots. 1. Sand,coarse and medlum. some- trine ...... 1.0 II Disconformity representing subaerial eaposure. 6. Sand, fine, clean, interbedded with lcustr-ine-______-.-. 8 LO what pebbly, esperiolly In Sehooformation: L Clay, slightly sit and silty fine sand. LtOus- sity, olve-gray; bauSone-half toot (pebblesto Upper member: trSne..... -1...... very limy, with ostracodes, %in. diameter); well sorted, L 2 6S3 7. Silty clay and elay silt, dack- a 6. Clay, grayhuh-olive-green mottled oolites, and smAl white calcium except top O.5 t, which Is carbonate (tut.) nodules (small brown. Lacustrine - -..5- 8 with black (carbonaeeous mat- . silty; about top 1.2 ft slightly ter-probably S. Sand, silty, fine, dark-tAn-gray. from vegetation irrefular rounded form remem- indurated by L-Drain eoil. during Lacustrine _-- ,6 7.8 lake desiacation), Locus- hung clusters of oollt"), with thin Upper part Iseustrine, lower iaminae of limy sand (rich in 9. Clay, silty, dark-tan-gray, some trin e------.2 part distributary (deltoic) al- 7. Clay, silty, dark-yellow-brown, ea- oolles and ostraeodes); silty-osady cly. Lacuatrine. 1.3 a 8 in lower luvium ...... ------4 1+ 4. 1d line. Lacustrine .---- .6 234ft somesmall selesite egrega- Sharp contact, disconformity. Disbonformity. I Schooformetion: 8. Clay, ilDty, dark.yellow-bmro to tion. Lacustrine ...... O 10.0 First lake unit: dark olive-ten, mottled with Thinollte unit: Upper or dendritic member: rusty-brown opOas; selenit, crys- 9. Clay. ss In 8, but with minute cryr- 2. Silt, welltsorted, light-brontish- 10. Clay, dark-alive-tan mottled with gray: someeand-filed dealecs tals and white a-line segrega- te softhinolite ...... - a 0...... O 12 0 black. LAcustrine- .8 9. 6 tons (probably mostly gypsum). Lower member: tion craeck, rusty spots, and II. Clay, silty, olive mottled with L.cutrine -. . 2.3 10. Clay, somewhat slity, drab olive- spots of weak calcium car- dark gray. Lacustrine - .9 10.a bonate eoncentration Locus- Dendritte member: brown-gray (mor silty and Dendrltic(?) member: 9. Clay, silty, grading downward to brown, less green than unit 8); trine . 1.5 5 6t 12. Cny, olive. Lacustrine - Z 6 13 1 clay; olive; 1.3 to 1.8 ft below minute mica flakes. 00lltes 3. Sand, medium, grtding to fine- Dendrltkc member and possibly lower medium In loner part, wcll- top, unit oont-als whitish part- and smSl tuta nodules common member: ings or segregations, some with in top I ft, none below. Below sorted, light-yellow-brown- 13. Clay, like 12, but with tufa gray. Lecurtrinc - - 1.9 7. 5t nodules, oolites, abundant osttacodes. Lacu,- top 2 ft the clay commonly eon- and especially tains somevery rupab formtion: trine. 40 12 7 fine sand and [a abundant ostracode., in top 2 10. Clay, silty, mostly olive, some very constant In lithology. 4. Sand, coase, and ft. Lacuatrine-- - o medium, with IL 0 brown spots. Lacustrine .. 1.3 14.0 lcutrline ...... I41. 23 4 granules and very emall pebbles Probably lower member: 11. Clay, Ilmy (elfervescen strongly 11. Ash, white, volcanie (pumiceous), (typical CorsonRiver asernblge); 14. Clay, silty, olive to olive-tas, tan, with iCi); tsfa nodules. Locus- cemented, very bard. lAcus- and olive-tan-gray; indisinttily bedded. Alluvium mottled trine ------6*k 24d* with rust-brown spots. lAcus- .7 1It7 Corson River channel sand) .. 7 14.5 12. Clay, olive. loustrine.. L5 152 111st1a. 34 Basenot reached. irlne------_ .8 20. 8 Thinolite member: Besa not reached. 13. Clay, olive; contains minute thino- SEY4SWH sc 9,wA. IJN., R.JOB. A.wher oleflat northAo Iettab m z lite crystals. LACustrine .2 o64 ScAooMosntain. Top of ocction, attitude 8,926 dc'frA. lower member: Fadonforr4atlon: tionthi D4ett) N igShin5 sec. r'. I VWYSt.YllS onc. 36, T. 19 N., R. So E. ASpenhaoe in Stilt 56, N., R. So B. Auser okein fl 14. Clay, olive. laustri .. . betwen srhAo A aourinand .6+ 17.0 First lake unit: tcr Souph flood plain, tesidnStitlt-ter Resereir diftrfion Stillwater Stosag. Top of section, Basenot reached. el. Top of tJ-elion,ollioude ,916 tSleet. altitude $,919:8 feet. 1. Sand, fine-medIum, more or less 2Tkk,,e,s V05,0 t-t.. is sity and clayye (especially Ion formaion: (tsreti D;ott Fallon formation: f1 rAI U i lower member: sE8Y.lnt'see, *tr., l8N.,R. S0. Ager olein flat sortfof near bottom); somewhat ce- Upper member: mented 1. Sand, clayey, fine, hard-cemented, Sroos 1lmooanin; top o mectimo,lititsde 8,922:c Sfte. with calcium earbon- 1. Silt, sandy, dark-gray; ailuvlum-- I* 1I ate. lAcustrine ------20 2. 0 dark-gray to nearly black, saline. Folion formation: Dhaconformlty. Im' uses Dfaeonformhty. (Irades to fine-sandy clay at base. Secondlake unit: Lower member (probably econd lake Scho fonnatlou: Mainly lacustrine . L 5 1.5 I. Sand, ftne-medium, ten, clean unit): 2. Clay, loeally with silt and a little Medritie member: 2. Clay, silty, dark-gray mottled with Locustrinet , 6tS 0. 6 very fine sand; dark-brown-gray 2. Sand, fine-medium, silty to clayey, 2. Clay, somewhatsilty, with tufa tan: highly saline, gypeifemro. to nodules, colltes, nearly black;iegresa- saline dark-brown-gray. Laoustrine .6 1 2 and ostri- -hit, pumieeoru 34-to l-In. asb tons, especially in lower part. Firat Iake unit: codes; olive-gray. Lseus- parting sbout 4 in. shove base. LAcutrine__. - 2' 5 4 0 3. Clay, silty, dark-brown to black. triSe .------3. Oe 50 Lacustrine .... . 2 2 3 2 !. C3sy, same so 2, wiith abundant Thinollte unit: calcium carbonste nodules and Lacustrine -8...... 1. 7 3. Csy, Ponslbly first interlake unit: 4. Clay, slty, tan, with black streak., ss In 2, with thinolitt tufa crystals, generally < 1/32 3. Silt, claycy, sandy, poorly sorted, alt segregations. Nodules are end some sandy clay. lAcu- in. thick and 1/32 to% In. long, most prtol-bly alluvium -_-_-__ 7 2 9 mostly S to H in., rarely i4 in. trine8------diameter, . 2 5 Disconlormoly? Irreguler forms- - 1 5 0 5 Cly, abundant 2 ft below top of silty, dark-brownishbgray. unit, decrersing upward snd Lacustrine a -___ ---- . i 0__------downward from this level. Disconformity. Lacustrine _ .- - - 3 5 St6i " o* . HI

LAEJ LAHOZNTAN: GEOLOGY, CARSON DESERT, NEV. STRATItRAPMlC SEChiONS, SOIL-PROFiLE SECrioNS, AND WELL LOGS 131 Tasa lO-iSfrstgraphictcstioe-Continued Tots 10.-ratigraphic ediosa-Contiluedd . tldasm t241-C d TAs9L 10.-StraligrayPhi*r fciom-Continued T"sta io.-Slritgraphic crdionr- ConUtnued Tkeas.a Depth Satn ll - ta.sA o formation-tontinued U.s) Ula) 0 Smilesoulk af 34 te car. birobnis,er. 9 and 10, . 1 N. Lower member: 8.0 &OEAuger kAdeis fhia dot a/ish can^ at*,,syP-Art * i: 5ESB ac. is, r. Is N., R. iO B. Strligraphie aactiam a- Bebooformation: (l es t ) u- co o l 4. Clay, silty, becomongmore silty nea f Aeond Fellerstake. Tap ofsetis, aituda s,927k fas poceda headef miitr her-anmye- is ollierd aerh edge(base) Upper member: donward, olive-gray. 2%4ft Fsllon formation: S.").. tIcat af pedisstd b es S&hooMJeutrin and Rainebowe.fasis. 38 Llthnid tula, white to pale-gray, below top of utit is about I-In -.7. Second lake unit: Top sf cedtie, altitude 4,020k ID/eet. diseontinuous layer of Irregular layer of git and Small pebble mass (early lithold tufa of this to In, diameter. Starting at 1 Sand, fine-medlum, dark-gray to FaUns formation and Labontan Valley group, (lccl Ufa) member) ------0-3 4.7k 4 ft below black, silty, carbontaeous; many undifferentiated: a top of unit area few 1. Lake gravel and sand and eolian snnd, partings of fine sandy silty clam and snail Shells. Lacus- Disonformlty. clay, sod Is lower 1 ft these 0 2 i. 2 undifferentiated -0-10 10k Deadeltie member (bhering lower pat of 2. Sand, fine-medium, yellow-brown. Pre-Lake Lahontan Quaternary lanuotrine de- are oommon. Lacustrine _ 13 21. 5k Toyeh col, eroded): 5. Ash, white, pumireous, hard- LacustrLne _------_-_. - .5 poelto (bearing Cocoon sail, much-eroded): -3 2. Sandston, coarse,and grittone, 4. Cy, silty, olive-greenl, some cemented. Laecstrine _ 21. Sk Diarcoformlty. pebbly, First lake UnIt: well-cemented, hard, with thick par- pale-greenlsh-gray interbeds of setian 15 3. Silt and clay,dark-gray to blank allel beddiag. Fractures filled with ailt and silty clay, posalbly (with local rusty spots along -sllehelike calcium rorboiate reset- altered volcanl ash;same lentl- nile rate of SWPCroe.. 4, T. Is n., R. toB. Bank of bling that In lower part of C.. horison cular limestone partings, gen- tage canai snd 2-fool auger former root), rarbonseeoun. hole at botnesof ca.al. Tap of of Cocoon saol. Probably licustrlne 4k 14k erally less than In thick sand m, alti/ude S,947 fea' Larustrine --- 3e 4.3 4. Sand, fine, clayey and silty, with Pee-Lake Labontan Quaternary loeustrine de- several Inches acroas; very - Afekat. DIept posits: line; samesoll-llme conceatrs ,n formation: /1 et) (f Ct\ aomeInterbed of So. candy rUt, Firt atcerlskeunit (bearing L-Draln medlum-dark-tao-gray Lacus- 3. Sand, pebbly mnd, and gravel, mostly tion (eroded C.. borlnon of Toyeb sall). Lacuntrlse Soil): trine -___ --- 2. &4 rather poorly sorted, partly oonsoli- 5 5 2i Sand, fins and very fine, clean, Dhcodonmlty. dated, indistinet, parallel bedding. Dendritlo and lower membeen: Probably lacustrlne lightbeown-tan. Eclisa. Top Sboo formation: 5 19kt 5. Clay, silty, and silty sandy. I It in weakly Idurated by 4. Sandotone, white, tufaceous, hard - 19k Upper several fot has some Dendritle member: 5. Sand, pebbly, and sand, clean, croet- very weak soil prole (_Drain thin laminae of fine wand,abun- soi) . L5k 1. 5 5 Cay,ome whatsilty, greenioh-grsy, bedded, partly eonaslidated. Prob- La.cutr.e -_ 1. 0 7.4 dant oolites. trcaeodes. some First lake unit: ably iscustrine -5k 24k nonplaty tufa nodules. Some Sand, fine, dark-tan, clean. Thinlite member: Bare not eposed. segresstona of gypoum and (or) LAcurtrine.. 1[5k 3k SoClay, as In 5, with sbundant emall N orX.-.t W arse nbt nbro shor o t s tslotsua PdtornMuPt a a other salines. Lacustrlne 7.3 12. 5 Silt, sandy, dark-olive-gray. kW. At to mtCh, hesfieythr dip baot r N. ad - daptad by tbh thinolite crystals in upper 0.9 naf hut,.,dosn tborao cn to nr thbsidc T west tes cor, sob*sa o td Lacutri.ne . 0. 3-0k 5± I .5 ft and a few In lower part. Lower member: ad the b ornua ea. epidle W po lp a td edii aest dipolinra ut anformity. S. Sand, pebbly, sad gravel, msndy. Laotri-ne-__ ------1.6 9 0 £'8 c . s dmoe pa t oaut ab rmspit, Tbb Vists t ae a p bbie o formation: at oboelua sd dhuft n aunar to . eit Ltto uPper pu a u,,to ek e Upper I It Is Interbedded clean Upper memberf?): tower member: te art hsno Io prdiimest to So math, flu cape , apPr-as btob is a Dt medium sand and floe-medium Clay, finecandy, gay-brown. 7. Clay, silty, green-gray (with rust- alien th.a a boaded bf ttoo nt rLo a id .ie - t fau a r an wad with pebblee to 53 inch .pw sadI ne cad,i( . N. Lacustrine 3+ &Sk brows spots); upper pert some- diameter, bowerpart Is sandy not reached. what mlcaeous. Lacuetrlne... 10. 0 19. 0 gravel with some pebbles moa Ne.das 25 & Sand, medium, clayey to elean, NWYNHi5 ea. 7 (s r.Teeped, 18 N., R. 81 E. Strdi- than I Inch diameter, some rust-brows. Lauatrine 2 ia 2 graphic e*dion, frees ecrral dug pit in high-sre easdbcr offir gastropod shell frsgments. ilawead of SF nor. ccc.11, r. 18 N.,R. 19 . Slratigraphie 9. Clay, Silty and flne-sandy, green- Faton lake and r -fool car hole, in flat natrel of Rainbow Hole cobble so erpoced in hank of dreioag canal, and -fast cager Aole bottomed on or gray; lower half nonteins Sbun- Mloalai. aTopof ecdion,cllilad, 8,948kfist. boulder. LAcustrine . 13 14.8t soal bid, in dcia of first and secondFallen lake. TOp of daett calcium carbonate nodules mi, allilude aboualSpO3 foc Fallon formatIon: aeectle'SI and andeolt-baaalt pebbles to r . 2 ralernerrk,.DMA, mnformation: In. diameter. LAcutrie- ,3 19. 5 liest beS unit: UPel 41/u) 1. Sand, pebbly, mostly medium Slrmfig-rphic caren rA f(pe lecatifir of deld-iic steaser af Second lake unit: 101 Clay, sandy, green-gray, with silty sand, fairly clean, samesmall SAo formetiose. 83 cr. 17 (maausreied), T. I N.,M R. Sl E., Sand, fne and medium, poorly to clay, vhridlan-green., at b e. pebbles; ear roeadom tac aidcof Rainebat Aunrtais, and sorrel hsdrrd moderately rorted, light-ta-grey. Lacutri-ne-3_- -- 5 20 0 gray platy tufs like that of 3 and that of the local feet cealof 4,160-Joft bech mark. Esporsd by a-ra Irenchec, Luet.ic. . i 3 Wyemaha formation: frots tp of high-toh bar of middle ScAo take, dean bakn oJf First lake unit: Tertiry volcanic roks: mostly I1. Sand, fe. clean, grayhh-olive-tan. pumice, some Eagles House gall, and by pit dag isto bedof gully (fig. 14), Tap oa aestion Sand, Silty. Lansotrine. 5 2 Lacsturlne -5 201 5 rhyolite and Bunejug forma- altilade 4,1786 5 cd. Cay, brows-gray. Loratet-e 9 4 12. Silt, green, with rusty apotes.Lae- tion. Lacuat e--e . atiformity. 2k 2.0k Dendritle member (bearing Toyth soil:) (fot) Ut o formntion: rn __------3--- -- a 20t g 2. Sand, medium, with rare pebbles, Sand, fine-gravelly, and and, well- 13. Sit, clayey silt and silty clay, dark- tan, grading downward to fine- sorted; top 14 Ins shos complete Upper member: grayiah-virldin-green; organin smell medium sand, mostly lecan, Clay, sandyand silty. Lacutrine.. profla of Toyeh soi (see soil profle 5 14 (Similar to decaying vegetation). -- rusty to golden-brown, and Dendritlo and (or) lower membens: 328). Lexuatrine; highshore-bar Lacurte 2----2 23, 0 then to elayey fine-medlum deposit oa middle Sehoolake- 3.5 3.5 Clay. eenhh-gre tough LcArU- 14. Clay, silty, dark-greeniah-gray, dark- sand, orvc-tan, near bse. trine. 3 5 17. 5 gray, to nearly black; strong organia Lower part contains somefrg- Lower member: not reached. smell. Lacutri... 1. 5+ 24. 5 ments of tuaf, like that of 3. Sand, medium, well-sorted, uncomael- Highly saline, much gypoum. dated. Lacut.rin - 3. 5 7 Lacurtrine . 2.5Bk 4.5k* Lower member (transgressive part): Disconformity . Gravel, cobble. Lacuatrine -. & 7. S M I -

132 LXlE LAHONMAN: GEOLOGY, CARBON DESERT, NEV, BTRAT7GRAPH1C 6ECTIONS, BOIL-2 1iOm0LE BECTIONII, AND WELL l.OGB 133 1 TAaLE lO.--81aiestrpapc secgjissw-Contlnued TAMLZO.-Stlasigeephit eection.--.Continued Arn ToaU 10-St-Sruitirthfo atroi4-Ctontinned Tints 1-0 Slsfigepthao secttoa--Continved 33--f-.Ceed 5.nli- gSsslo St tbew 3S-C-.Os-._ soif): raIt,;es\ Depth iyemaha formation (bearing Churchill SfitgernpAic sstios et tw tfocafty fee CtrcAitt oat (ae,&is Wyemaha formallow-Continuod Ifeetg It NE car. ea . 0. 2. 15 N., R. S9 B. Tap of seites, tlIiload Gravel, tandy, Ane, somewhat clayey and - .es) 12, sonIprofile 345) end nedofor l menter of &A. feossttia here (rA soil profile 34S). Upper few 3,540 feet. Carso Risee food pta. Stlritiraphie .ectott tr- mottled red-brown and gray In upper I end tmotr tangui of Irdteen Lakes formantion. Reel bask of Aek feet of sand partly indurated by soil de- d in drainageeaid t nk, *nd 6&5.s *umoo sir ft (oside horiron of Churchill soil), pale- soothfof *salbasAiti it velopment, lower put of sand is uncon- et wasl sideal Chsuchill Velsy, 75JI TOkkne. Depth Yellow brown In next I ft, and containing middlte of velle, SEy.SWY se 1is, T. 18 N., R. o -P. Tap of solidated. Mostly parallel bedded, dip- Fllon formation: Firt lake unit: Osh Unt) some white oi-limt ooncretlonw nd 4-AIL ping several degree. southward; locally feitn, agitwo 4J,10S 1, Send, ostnee, rnedium, and coatings; balance is yellow-gray, with croesbedded. Bas of sand not exposed Seboo formatIon: ' . frlctn... teth fine, moderately well to some soil lime (C.. horizon of Churchill here, but about SOft to north It overlie. poorly sorted, light-tan-gray soil). Alluvialgravel ...... S8 11.3 Lower member (bearing Toych soil): boulder gravel of Etta formation ... 1i 40 tnaz formation: Sand, medium and fine, Ulmy,very pale to locally daRrk-gray; mostly la-tt_m Gravel, fine, well-orted, with a little sol- yellowish pary; vme assatl pebbles; rather ietIncuiar parallel- lime (lower pat of C.. horiron of Church. abundant small snail shell. (Para- bedded, bot some small- tscC.17, r. N., Stre-tieepicetton repo0sd NE4 18 R.3SOR, sale crosobedding noer base. ill soil). Lacustrine . .1.. 5 12. 8 pholts n"eadenis); at base a few in hank of drtinage ctaal and 5-footl oegr. hea in Jht star former grew Lai.turine --. 5...... --. 2.323 Gravel, medium, well-sorted, with a little heads of corallime tufa (which mowrseof Sli~uotr Slang),. Fop of ecdir, slitilude ,954 *3feelt. lB 3 upward In sand from bases attached Shrp contact, undulating; minor lake tuts cementation. Locustrins--- 3. 5 Thfrnkss D ep satnot exposed. to cobbles or pebbles in the gravel Fallon formation: ( , (is disconformity. bed below). Lacustrine. Top 8 in. Second lake unit: 2. sand. fine, and very fine, grad. is weakly cemented by calcium car- 1. Sand, fine-medium, light-tan-groy, ing downward to silt; sme Partial otraligeophic seclion in lower part of Truckerf-oemeon bonate (C.. horizon of Toyeh soil, unremented, clean, parallel- irregular tufa nodule. and .gulch on north aide of hill aboul mile sooth of Eaglk IItoue, in eroded). About 250 ft south, sand bedded. LAcustri--e . 2 2 gypoum( segregation; iron ,NSw IV% er. 15, r. 18 N., R. 30 E.; lop of sertion -tor. ebout contains hebad of dendritic tufa of First lake unit: stains; at base, I In. of 4,4S0 .760 feet due east of SW or. see. IS, ot ofluldr olf sboui dendritic nember of Sehoo, but the 2. Cloy, silty and sandy, brown, many medium "nd, very dark -1. (Depth ceftun betl. ,ndfcatescumetlatire thicks.e,.) high shore of the middle Sehoo lake snail shell.. Lacustrine .- . .9 29 gray. lcustrine ------4* 2. 7 rokeox,, Depth is not clearly marked ...... 4 4 3. Sand, fine, gray, some snsil-shell S. Sand and silt, interbedded, ruckee formation: rf 5t)1 ire )I 1. Tufl, silicified, variegated red, pray, buff, Lower member (transgressive phase): fragments; weak calcium carbon- parallel bedded. At top, Lacustrine... 0.5-1 ft of silty coarse to and white (wonderstone"); wel. Gravel, cobble and pebble with sandy ate cementation. .: 3.4 bedded; poorly exposed, form, top of matrix; Uimy; thin lime coa-. 4. Band, fnoe-medium, brown. Lmcu- fine sand, poorly sorted, medium-gray; then about hi, ...... 10* 10 logs on roundstones, and uppermost trio.. ------.8 4.2 2. Sandstone, oolitic, tuffaceous. generally cobbles and pebbles have this dis- Turupah formation (bearing Toych seil): 2 In. tan-grpay sit then 3-4 more sandy than 3, pink-gray to gray. continuous coatings of curalline tufa. .5. 5. Sand, fine, collan, somewhat ce. in. one-medlum sand, clean, pink, hard, well-to massively bedded, Roundstones are all basalt of Bune- mented with calelum carbonate, looee; then about 4 In. blue- some beds ripple-marked; together jug formation. Unit thickens to 6 repecially In lower I ft (Cm gray to Ught-tan gray silt, with oolitb below formn cliffs 20 to 30 ft 30 it to the north and there con- horbron of Toyeh soil) .. _ 2 B.2 snd silty clay. Some Iron ft high ... ------2*± 35 talnr some small boulders8 2 B. Band, fine and fine-medium, rela- statis, abundant gypsum 3. Limtstone, ooltic, with some lIter- Sand, medium, white to light-gray tively uncemented. Eolbon --- .9 7.1 segregations, slight salty taste. L4cuStrine------1-1.B 4&2* bedded tuffaceous calcareous sand- (IOYR 811 to 10 'YR 711); very clean Disconformity, stone, gray-pink to gray, hard,well- alimot no pebbles or silt; very in- Sehoo formation: Sharp contact, possible minor dis- to massively bedded .. . 5* 40 coherent, except somewhat ce- Upper member: conformity. 4. Saxdstone, tuffacrous, pink, light-pray mented with calcium carbonate In 7. Clay. brown, many snails, Lacus- 4. silt (very fine sandy to slightly claysy); top 0.3-0.5 ft dark to tan-gray and greeniob-ztn-gray; top I to IS ft. Probably Iacus- trine ...... 5a 7. 6 gray to nearly black, due to upper S ftnolitle and generally cal- tris------10 lit Disconformity. eareous, wellIndurated; lower 12 ft Indian Lake. formation: Dendritie member: carbonacous matter, and soft, though generally somewhat Lower tongue: B. Clay, greenIsh-gray; top several sandy; remainder tan gray and better sorted; some better Indurated than 7 . ... 30* 70 Sand, medium, with some pebble. and fket darker and somewhat car- 5, Interbedded mdterial like C and 7.... 2* 72 cobbles; light-tan-gray; slightly In- bonearous. Lacustrine ...... B. 3 13.9 Interbeda of fine sand In 6. Cloy, some soft siltatonet grayish-light durated; probably alluvial . 2. lB. a Thinolite unit(i): lower part. A few gypsum red, semi-Indurated, thinly bedded.. 5* 77 Sand, medium, with some pebble. and 9. Cly, lean, rust-colored, and with .3 IL2 segregatlons, iron staIns. - t-1.5 5. 5* 7. Seodstone, tuffsceous, soft, semi-indu- cobble., especially at base; bright- light-gray Ilmy segregations. Lacustrine rated; medium-grained sand with silty yellow-ton; moderately coherent; Lacntntine....._._ .... - .3 142 Sharp contact, porrlble diaconformity. matrix; probably large percentage of some weak calcium carbonate con- 10. Clay, iean, greenIsh-gray, with Turupab formstion: sllice tuff; mostly pale red, repecially centratIonp. Alluvial. Thickens to small crystals and crystal ag. S. Sand, coarse snd medium, local upper part, with bright-green grains; 5 It, 30It to the south ...... 1.5 20 gregates of thinomlte and small lkne. of danapebbly coarse well bedded. Some silty and clayey Sharp contact, dips about 10 B.; slight discon- rounded tufs nodule.; some De- to medium snud, clean, un- beds. eapecially in lower port, where lormlty. tracode coquiu. partings, eorne cemented (lose); pebbles many beds am gray and greenih rarly to % in. diameter 3 Wyemoaha formation (bearing Churchill soil): monly showing rusty stalning. (typical Carson River as- Bray------...... S± 112 Sand, medium, with a few pebble., sob- l.acustrine ...... _ light- .S 14.7 semblage). Top3 to. locally S. Limestone. deme, fine-prained, bkos, and angular sock fragments In Lower member: tan-mroy ...... 2 112. 2 well cemented. Alluvium uppermost I ft. Grains mostly frosted. II. Clay, olive-green-gray I.acus- (Carson River chanel 9. Clay, buff-yellow ...... 3* 11.2 soil, Eolian. Top 4 ft bears Churehill trios _.__------__- sand)------3-4 94 ase not expooed-f sult cuts oni section at bare. which is exceptionsaily well preserved 4F- 1.7 Bsie not resci ed. Sharp contact, diseonformIty. STRATIGRAPHIC SECTIONS, SOIL-PROMthE SECTIONB, AND WELL LOGS 135 LAKE LAIONTAN: GEOLOGY CARBON DESERt, NEV. 134 T~a"t 1O.-Sta8irrigapkio secitoan.-Contioned Taax an81lisa39.c, eeli~nin

TAMMt10-~8tralk-nPhiO SCo1floA-VsnttUDed TasE 10.-8Irolipraphic secftown-oantinnad snnnitaaa--Candsl._ sa-aasa both So-." 41--c-au-a Sebooforcetion.Continued U6tdn ti T) Sehno lncsrmtion; - nk- ed ° Lower member-Contused Sehon fornatlon: (r) Fallon formation-Ctanued Deadritie member (regressive broken by deep, unit equivalent- aourtae Upper member: First Interbike phase): gaping cranks, probably 8. Clay. gray-brown, fatty, eomn. Continued S. Gravel, very One pebble. disileation eratks, and Iron stains, ome ear- Lacnstrins. Well sorted pac; Part4s at top Bpe" by grasIly bonaceous matter (black artifacta, of Loveock (little Interstitial and or thies are idled aondfrembedsll. Abird VWaina. Lacuitrbve . . 0. 7-1. a 10± ph-se ______0. 7* 0 2 L7± silt),uncernerted. Thick- bone tound ti one df hta 7. Sand, fine, clear, gray-brown. 4. Silt and Sna send, well- ac to about %ift at east cracks ------1.3 9. 7* acust ridn... . 7.... 10.7+ - bedded, bedding thin and wa of pit, and here I medium, clean, gray- underladn by 0.8 ft of lIke lwermember(ttnameret 0vepPS t S. Sand, parallel. Probably eollan .2* 1. 9* 13. lake gravel, pebble and eob- - -- 2 0 brown. Lacustrine 12 74 First lake unit equivalent: esad. Brrenof rtfachts Roundbtones locally ...... 2.5 ble. 9. Send...... 15 2+ One or Dendritio membert mainly of red Vl Base nMtexpoeed. 5. "32-inch midden. 9. At top, half Afoot of massive derived, 8.bsr It more midden layers, Inter- eaS breedsand black eilt and fine lacuatrine limestone. stratified with white; smooth upper sur- andesite ikmiar to that in of Eel e rntvenin, 81134 and with Hidden Cave and Floor of Hidden Cor, on norlt ide sand (colian?) face, dips about 15- E.. wallx of ar. £1, T. 16 N., R. 50 B. Strniigrwptic -1elior eo sPsd in Ied rocky silt (slope asah) than S' exposed in lopes above fattening to less * -rsl of pit Nf6 dug in 1951 by Califrni. Ueir-rniry aned U.S. layers. Continuoun mid- at east wall of pit. Well- the cave. Uacemented-. 14+ 10.7 1966). Top of at Cr-l. Surert srchtornlrir drid puny (CroGrryp, den 0.2*0.15 ft thick bedded, strata About I In. Bane nat exposed. .edion, enlitude4,103fei. top; several disrontinuoun thick, thinning eastward; local midden partingo PallOr formastion: IZz many fish bons. In low- I> 4f.-) beloer Midden consists er everai inrhec thinly SHSiY aee. 81, T. 18 N., R. 50 E. straiignrplicIreion Upper member eqi-valent; guano, plant of of rotted bat bedded brown lake clay Aspoard in blff of head of main pie isaE sdrsAbnlsie, esl 1. Silt, come very One and fine and matter (tuli, cane, alternates with partings of Hidden Carc Top of senio, alf lad 4,rr4 foel is roao nflatk rod; light-gray, olien; io lte est cattail); bha Dur-erous Icustrin lime- Lnkrnsta hoc haul atr s. diaidr baseem bedrock ridges Angular of the Lovelock white soft, sparne pebble-nse artifacts stone; this part becomes and ral. fragments of red banalt 1. 1* .0* Phase of Hiser (1951)--- ineresingfy clayey est- and We, probably roof -0* Ifrt n Turupah formation: ward. BPrren of alti- .9 0 6* Sehoo formation: fragment.; well-bedded, Lower member (regressive phse, 6. Silt and fine and, pale-gray, factso- -...... beds thin and parallel; bearing Toyah soil): evenly *nd horizontally Indian Lakes formation: towmnbat oherent, tend. 1. Gravel, coarse, fairly eckn frag- bedded (loase), with local Middle tongue; to form soft blocky 10. Gravel, coare, very poorly mostiy pebbles anud cob- thicknes some- lenticular lyere of grav- ments; sorted, contining Angulac bhImfsu.nelugforstiten; vhat variable, due to dep- elly silt (elope wash); also some of cellular toub; snr- Utter Increane In propor- blocks and boulders sA otltion over irregular much A Isin. but mortly someahvewatrerwormeoat face sloping slightly to- tion toward cove portal; Ings of lithold tofu (re- 14.in. diocontinuous mid- less than S in. diameter, ward Interior or rve; top with some interstitial sand worked from unit 3). LA- aurface originally s.au Al- den parting In middle. and al~t; slightiy cemented eustrine. Top I to 11 ft most level - 0...... a7 0.7 Unit thickens to mars bens Toyeb oil .. 3* 1 3*k tban 3 ft In east wall of with caicium carbonate. Second lake unit equivalent: pit and there contains a Slope wash. Barren or Lowermember(tranarisvepbase): 2. 'Top midden; rat and bat , Artifacts. Yilded aiblock 2. Cellular tufa in place (irreg- white pumiteous ash part- 3.5*t guano. with abundant ofcellular lutf (of the ler- ular layer). Laensludmre_ .5 Ing, Y.to i In. thick, vev- many cobblea Tlpthtla (cattail) leoves, er member of the Sehoo). 3. Gravel, coarse, eral Inches above base. to 10 in. diameter; satrix some clam shells. a few point. ob. Thins rapidly eastward to Two obeidian of fairly well sorted medi- feathers, And Lovelock part of 0-0.1 ft thick at etat wall S. 3* talned from upper 1.7 um gravel; coated And (cultural) Phase, rfO Iner 4. 7*4 - ...... - unit------1.7* of pit remenitd with lithold tuta. (1951) artitfat. and orcu- Behooforrmsaton: pation debdr. Over 85 Indian Lakes formation late Sehoo cor- Lower member (regreanive pbhse): espeiallUy In upper par. of Artifact. re- relative:: Luaastrine. Unit thins Percent 11. Lakesand, pebbIly eacnun- .I tovered Irom the cave In 7. Gravel, coare to fine, poorly cemented; no artifacts.. ti 4*t rapidly southesatward 1. 5* 5* 951 c.me from thisbed_ 0. 3:3OIS 1.0 sorted, much Interdtitisi Lower member (high-level phase): from eent of bar with a few First Interiake unit equivalent: send and silt, many blocks 12. Lake clay, ailt and ailty fine 4. Gravel, medium, cobrles. (Base el Mnit 3. Silt snd fine sand, poorly and boulders, anme 1.5 ft sand. Top third bafaitily 2. S* 7. 5* sorted, with many angular in diameter. Slope wash. laminated broawn clay; poorly expored.) 58* rock fragment.; probably Thickns to more than I ft middle third Is brown ilt; J. Gravel, Corme with some slope wasb, Locl guano In east Wall Of pit. Local lower third, brown silty small boulders to I It. except partng,0.l toO.5in. thbik, discontinuoas rotted guano fine sand. Cay sslightly Nio tufa coatings akout 7 in. below top. partings. sany beam of 6ypelferous. Nearly snI- very thin discontiuouse tather constant sandy small taUnmato and birds. form in thickness over pit white ones that may be floor, but dip seversl de- silt (milan?) layer about Four projectile point. as- secondary. Lacstrine.. 3* 10.6 t 0.2 ft thick I. middle of signed to the Hiddrn Cave groes westward. Upper unit, with dark-brown (cultural) Phone by Gross, staining and local midden cup (1950)-. . 9* LAKE LAONTAN: GEOLOGY, CAlBON DESERT, NEV. BTRATIORAPEaC SECTIONS, SOIL-PROFILE SECTIONS, AND WELL LOGS 137 TAKnt I0.~_89rl#s~jrelI?5fl sctos-40niinned TANIJ 104f ref t1rcifr c Ofetio-Continued TAUS 10-B stroi bphicectono-Continued TAsNe l0.-_SirsjFlgpltO #,ctfoes-Continued 551dm 43-caal.ese aeclion. The context between the Wyemahs formation ond h Ieas Dsela gravel Ofthe formatIon ISwall exposed In SeOVe small Thtees els) Cl} Uea5) Behoo formatUon-Contlnued 7yoAs Dpt ~etXa -Orrtl ttrr 8eboo formatUonContinued within a quarter ofa mile to the ukthwest. Seboo forrsation-Cantlnued Lower member-Contluoed tributary gulches Dendrite and lower membens-Con. Lower member-Cortinued I, 3.0* mation, Indicating derivatIon . Onravel,medium, with some eob- part, Limestoepartingat base from shore drift from northeast bir (poody enposed)l laea- 0 B. Stretfiesplsc ction ep"d in Lacustrine ------1.5 A. S& SBl e. L1, T. 1I X., R. Derivation of upper gravel (and di-ne_ _ _ ------3* l134* benk of ,el galfV at so.ikwe side of sddls st wed end of Wy,- Sand, very fne, and fine, with some bouldems q' . .. - ies "wondertonem" pebbles) is 7. Gravel, boulder, many ,nake Vsery (pie. 7 and 5). Top of ectioii aiilsds ebovt 8,996 very fne sandy silt In middle; ostra- more than I t dIameter. .7 9, 2* unknown, Lower gravel is lower fae, leArersfe/diadu pit. * odes. Latsutrine - member; upper grvel probably Lacuddrne ___-- ____--_ 3* 1634* Sand, pebbly, medium, lacuo- if,).. Ustd1 is dendritin member - _ 0 11.it * S. Granule-eand and fine gravel 3eho formation: trine -______------10 11 24 well-cemented by Utboid Dendritdc member: Gravel, medium, and medium sand. LDwer member: Pebbly medium and, Lacurtrino- , 5 12.3* tuft lacustrine - 51 17* Gravel, very fine, well-orted; top sev- Lacustrine - _____------.7 11. 9 9. Gravel, coarse and medium, In- enr Inches densely cemented by Disoniormlty. Disconformity. Wyemsah formation (bearing Churchill solI, teedded. Cosrne layes con- Uthold tufs, weathers to slbs. La. Wyemaha formation (bearing Churchill sl, i. cobbles and small boul- custrine -_- -3. 0* 3. 0* eroded): eroded): Sand, fine-medium and medium, pale- den to about . ft diameter. Disconformity, representing subaerial ex- Sand, fine-medlum nand medium, pale- Some lithoid tufa coatings on posure. yellow-gray, somewhat ermebedded. yellow-gray, nomen bat croesbedded. Eollan Semi-indurated, especially In roundstones, but evidently Thinolite unit(T) (bearing Incipient un- Eollan. Partly Indurated, with Ir- reworked, not deposited In named soil): upper several feet, because of calcium regularly disseminated white soil-lime carbonate cementation by C.. horizon piae. Lactstrine - _S 22 Clay, silty, grading to silt, clayey sit concentrastons, commonly along bed- (eroded) of Churchill soil - 17 29. 3A. 10. Gravel, medium, sandy, espe- and fine sand In lower part. Cal- (eroded C.. horizon of ding and joints B.u .n.d enord. cialy In loner part. La- cium carbonate nodules and platy Churchill soil) . …-..------25 14 44 cuatflne - 3 25± partings locally at top and near Dane not exposed. Disconformity. base, drusy-crysteUlne tuta nodules akoUns 43 ,SE34se.zSI, r. ISN. Rt SOB. Strstigrsaplicwcgnorpanedin Wyemaba formation (bearing Churchill soil, at bee (no defnite thinolite seen, onokof large guty aStsouthusi side of soddle at vsd end of IVIWyseea scstion rpoSed 1 . eroded): however). Lacustrine. Top sev- SEh sec. II, T. 1I N., R. 30 S. Stmtigrspahic (p. 7 and S). In lype area for Ilt'eoaha and Setoe of large gully at southmst side of addlb of weat end of Valtey 11, Sand, fine-mediurn and medium, eral Inches are eathered and show is hank area for WUYesmahaand srreninj. Top dpof ction, altitude abse 4,046 feel. mostly pale-yedlowsh gray. Incipient soil development--day Is Wy-cessa Valley (ph.7 and 8). In tlpe Eoagsn Top 10 in. (locally checked, stained rusty red-brown, Sehoojormaions op eJofetion, altiiude aboui 4,046 fed Sehoo formetlon feest). r 1sl) Ist4..s DspO eroded) is B horizon of Chur. and bha some white soll-Ume conen- Sehob formation: (1J50 (1 Dendritic member: "heads" is place, to chill soil, light yellowish brown tratlon -_------_--___--_ 2. 0 5.0* Dendritc member (bearing Toyeh oil): Dendritis tuta (IOYR 6/4) sandy loam, weak Lower member: 1-ft. diameter. Lacustrine -. 54 6.8* Gravel and pebbly sand. Top 2 ft Silt, sandy, and fne sand, limestone prismatic, hard, noncalcareoum; Gravel, fine, well-sorted, uncemented, and granule Is very fine gravel partIngs. Latuetrine -_ . L 0 1.5S* next 12 In. la B., horizon, most pebbles under I In., maximum send with some pebbles over 134 Dendritlo and lower membem: lIght-yellowsbh-brown (10YR size 13 In. lAcustrine -_-__- 1. 3 ti3* middle part, coarse send and In.; Laeustri-e--______-_-_ 1.8 10* 6f4), massive, slightly bhrd, Sand, medium, with some coe sand grit with some small pebbles, well Sand, with weak irregular calcium and granules, * few small pebbles; lower 2it Lower member: sorted and uncemented; Gra-el, very sandy, cobble. LA- cmrbonate concentration; next uncemented. Lacustrine- 1.2 7.8 sandy medium gravel grading is eustrine--_--_----__----____ L 0 4. 0* 20* In. Is C,. horison, very Gravel, cobble. Lacustrine - _ 6 S&0* to clean medium gravel at bane. pale brown (about 1OYR 7/4) Base not reached. Mdany waterworn fragments of Disconformtty. Wyemaha formation (beaing Churchill soi, to white, mmlve, hard to stous42 dendritio tuts throughout. La- locally slightly hard, with Top I ft beam Toyth eroded): is eustrine, strong to locally moderate cal- SBEf se. YI, T. IS N., R. SO B. Strortigrplik section erposed Sand, medium and fine-medium. Eo- benl of large gully ei souaivx side of saddle af vsx end of Wye- Ilan. Top several feat are semI-In- dum carbonate concentratdhn; Discontormity. Valley (pt.. 7 end 6). I Itlpe ares of Wyemaisa and Se&l durated by lower pert of C,, horlson next 18 In. is lower part of Cm maes Dendritkc member: 7 altildel taost OI4,Sted. of Churchill soi (which is partly borison, very pale brown to fommations Top section, Silt and sandy sIlt, a litt clayey locally white, manolve, slightly eroded) .------.-- .0* Ivt 0* Sehoo formation: silt, very grmy, with platy Ume- hard to locally hard, wIth ir- 7 *.) 7 k stone partings. LImestone part- Eetza formation: Dendritin member (bearing Toysh sol): well-sorted. lAcus- regular strong, moderate, to lng I to 2 In. thick at bane cements Gravel, medium, weak calcium carbonate con- Gravel, Medium gravel In top I ft tri-e _------c 10 S is top of underlying gravel. La- eentration; the underlying and bottom I ft, remainder Gravel, boulder. Laoustrlne - _ 1 0* 1II. * sorted, castrines _ _ 1. 3 9 S* send, below the soil, is un- granule sand, very well Paiute formaion (bearing Cocoon oil, with some small pebbles. Many Dendritic and lower member: cosanlideed, sIngle-graIn, and eroded): waterworm fragments of dendritin Gravel, medium, grading to cobble looe she stronger calcium Gravel, boulder, poorly sorted, bearing Top I It beam gravel at bse. Many "wonder- carbonate concentration occurs tufa. Lacustlne. somewhat eroded Cocoon soil. In top . _.._ atone" pebbles In upper part, few In whitish streakb, irregular Toych soil 71 . 7+ seveal inches the Interstlitil fines are Diconformity. In lower. Lacustrine. The lower bodies, and some cylindrical reddish brown, somewhat clayey. and member (bearing Incipient un- (cobble) gravel, traced northeast bodies 3 to I In. diameter Lower nearly free of colclum carbonate-the named soil, eroded): (along lake bar), is separated from (apparently precipitated Bn subhorison of this oi; beneath Is Silt, clayey, and aIlt, very limy. the upper gravel by a I-to-I ft around former roots) 40+ 65* sand layer; also the lower gravel dense caliche-the top of the C,. Top appears weathered (Incipient horison - .----- 1.S IJ 0* units vary considerably In thickness within short soil development, somewhat cnamrens and roundstones are al- Nona-Several Bn not exposed. distances; the thicknessos cited are vera In the Une of eroded). Mainly silt in lower mort entirely from Buncug for- I-

LorS 139 k STBATIORApHIC SECTIONS, sOIjLPROFILE SECTIONS, AND WELL EYV. 138 LAME LAONTAN: GEOLOGY, CARBON DEBERT, Tastz IO10- istlligrsithic eeoitoa-oati 10.8tt nfeaijrphfooctf nn.CoatnnSd itinued TADrM Sact. 41 jeoianfa-C tlnaodc Tasta 10-8gsttgraphio ocrtt, -0 Tanya 10t-Siraiig phia ftetbw. illae 400 Jt sntA of Sgc. ceW. tes so. d8and to, T. 1i N., R. 411iaS crtiin epoad in Sehooformationb: I/ct) iJz) uo e. CosrmaRisrr jtnad ptain. Siraitirephic Lower member: canal 6onnl,anld 4-foSnt osge Atf. rop of aeclian, et/itsd .SE.NE34 sec. it, r. is N., R. M0E. Generalized nieati- Wyemtah form attn-Continued drainam 6Containunue Gravl.tac ne; mostly team of smdal- s~~~~~snJSLoPPet-s,16- - graphic seclion oopeed ina bank of fares gulch s's ned, AideOf 3,819 Joelt of and prlttiy nta Iocoa d+ boulder and cobble grave]; soma Snathno neay saddle bedwr,. Pdain asat and SecAmAMalnain (ueat end than ,i ta. diameter), faora- wereprecipitated about fornttu' pebble-gravel beds, generally fairly :Faiton formation: VW) tj) WyessahoValley,). In fitps areafo, Wym,ealsa And Sahi (Joel)lia t Calcium carbonate eonceatrntrsil, - well sorted, with little intertitiall Sccond lake unit: lion.. Top af sadian, alfil ode4,090*k 101f.4. cresa, irregularly downwnrr; h'tt sand. Upper part very llmy. Sand, fOns,lght-tn-Fray, clea, thnly0 aieknean DOeph dip northward Asmueb Selon formation: I (/inlt (asatn beds commonly are poorly lroiorlAd"d About 35 ft to west thicienso to 7 t bedded; beds Coberent. Bottom 1-3 Ia. member (beailng Toyebt So); and upper 3 ft is e"oented by An20'. DendrltIe Dam not exposed. grading to clean 1. At surface, %to I In. small pebbles lithoid tuos snd topmost round- lean medium snnd, . 45, Alluvia and lacut- and grit iag gravel). Under- stoies bear coatings of coralline coare sand. t.4 1. 4 neath is 3%.tn. andy ailt, slightly tufa. Lcutine - ,,,, 4 9.5 trine (deltaic) -,- . It, T. 18 A.R.JV, 80 .ttriagaphie .. lion caleareoui, with momegranules SWY.NWY4 Sand, mostly medlum, well-Aorted, Disconfolrmlty. in aathattmallt of 196* Von-l pd n a tah sideof sodd and pebbles, having prominent exposed of smal-pebble mod; First lake unit: *lfoanri. ,r aset red of Wve-noto some lensen vesicular structure (vesicular beltares Shoa and Neira limy;well-indurlaed. Lcustrine. 10.5 Clay, choeolatebrown to light-brown land;f,-) l ch 0 horiaon of Toyeb soil). Baiaoe Valley. Tap of aclion (farrne (darkest and Ironstalned at top); rotrr. Dear Sharp contact; small disconformilty. dovwward. La- Is granules and 0ne gravel with fead Shosrrsrfgae f-16.e gradesmore fatty formation (bearing Churchill soil, 4. 9 6 3 some water-rounded fragments ((rt (I dt Wycesaha tustrine ...--...... Sebooformation: h formation: ot deadritic tutn; upper 4 in. Ib eroded): Flrst take unit or Turupt Dendritic member (bearing Toycl -tI): part (poorly grad- slightly oxidized and leached of Sand, silty, gravclly, In upper Sand, medium, clean, blue-gray, Sand, fine, with some small llll51 t rare cobbles, gray. calCium carbonate snd grades mreted,with comepebbles, log downoard to orange-tan pale-tan-gray; very lizy; rl-z1'I boulder); grades downward to 2.0 a.3 into B- to It-i. horizon showing and smal Alluvial or iacuatrine - dendritic tutf in "heads" e,,a1ttl3l"'y sandy coars gravel In lower part. Cot- moderate soil-lire accumulation alaOtlt Turuaph tormatton: more than I ft diameteri 1 (slope wash). Sears a strong Allu- (B and C.. horizons of Toyeh grew up--I 1rtt" luviam Sand, medium, somepebbly coarse. I-ft high, which soi (Churchill soil); B horiron is mositly 44 12,3 soil). Lcustrine ------1. 3-2 1. 5* gravel bed below. Upper tett4rnl vir. ------eroded-top 3 to 4 In. i6 .. hortron, Deadrizlt Andlower members: exposed. inches (B horison d Toi' vh1 151,il) with some calcium car- Base not medium sad Se, and silt, i. I grayishhbrtwn 2. Sand, darker and browner than 1tl's In, remainder al unit $.U..b 46 highly eIl.o.eous, wIth many bonate oncentrat beneath. Lacwrrhie '' is C.. horrion, with strong concentration cemented by calcium partinga much ENzi edge ec. 3cS T. 1i N., R. 99 E. Cerna LQakapiin. carbonate snd several partings Dendritic member: 1 of calcium carbonate, C.uo.lg with ar'il Itol mottling; C.. horiron extenda *eliOK expor d in drainagecanl bank, and S-fao 34to I in. thick) of Gravel, cobble, white Sleaiigrnphci (generally I-It diameter, nid -it' underlying grvel . 1.5 12 ncioftfid 5,9*1 feet. nearly pure limestone. Abun. boulders to .bout 2 ft into augferhal. Ti pof pebbles and sand in marcia: 1011-1 T%*"z 1nea ostradod snd srail-ahell Small dicco ,ormity. q..l) dast *11bazlt of th,, PIlJ"ig Fallon forral,"1o" (1U4) Top %ft. contains atones are 1 fragments. formation; heavily coated wll' r" Eetas formation: Third lake unit: Water-rounded fragmenta Sand, medium and coarse, poorly to many carbonate in top %4 i I it Crs el, cosnAe-smsl1 boulders and cobbles of dendritia tufa. Lacuutine 2-4 4.S: clue Lacustrine. I. S 1. 5 (Just beloawdeadritr tufiWImt),t In matrixsof pebble gtasl, with a local moderately well-sorted. Disconformity. next 34to I ft Is almosl f,., t1' Nl- lens of smali-pebble gravel; roundatonrs DisconformitY. Lower member; carbonate; sent I it te loavy 11 basalt of the Bu..jug formation; Second lake unit: cobbly, with and; clues dark gray, carbon- 3. Cravel, coars "I'll olol many of them are more or less rotten"; Slit, clayey, very roundbtones of ba- Ohthold tut.) moating., -i - t 3-I S 2+ well-rounded with corollli`,Illt thoee In upper 2 ft are strongly to mod- acots. LAcustrine dips about IO- (lake boulder mnsted slt; locally (reworked from a bar of Ptil"l of erately calcium carbonate lithold luts) First Interloke unit; br). LAcustrene. In next 2 ft have only weakcost- Sand, medium, etean, light-tan-gsy; tower member 30 ft I,' b ) 2 3 coated, 4. Sand, medium to Sae-medium, A probablc very weak soi lies very lenticulr (low moundlike de- Lacastrne -2 'I; Ingn. CIeD, with a few small pebblen; to 3 I., mug------3 fine-pebble, to r a" Ft t 3X ft below top ot unit-2 poriu). Eolian Aeenly bedded; some o.irrcodo. Gravel, weak oside horizon, disconformIty. sand; well-sorted; relatlfy ""'- gcatie of very Sharp contact, Lacutril ...... 1-3 8* by sweeral inches with ery Fint lake unit: lmy, slightly induralcr.d I ot"a t underlaln i63* Disconformity. wesk soil-'lme concentrution (noted C. Clay, dark-drab-gry. LScuAtrine. 1-1. 6 ...... ---- Wyemaha formation (hearing Churahbll aoil, Wast...... I 61 i rntirely Sand, fine, dark-gray, carbonaccous. - 7 DadianLak. formation: hobslon). Lowermot eroded): calcium crbonate, unconsoli- well- itngue: free of Turupah formation; 5. Sand, fine-medlum to medium, Middle dated, with matrix of blabk bansltic coarse pebbly, pebbles to 34In. diam- evenly Sand, fine, somewahatailty endsltv- Sand, orted, pale-yellow-gray; medium rnnd. Crudely stratlted; beds eter (typical Carson Iiver soemblage). (not crosabedded); bedding dly; with veriabte tnfl"l t 2 5- I19.65 bedded eclhh oated dip everal degreesactard; pparently Alluvium (Carson River channel sand) downrlope pebbles(mostly small), t about flat, or dips 1 '-2- it;.strlne--- 5 S i lI yY. sre part of a spit or bar. BIse no exposed. (NW). No tons.. sand is almost iocally. small boulders; entirely quarts grains, well-ronted. with some calchumcarolsntfl r. Bnse cot epopred. 1i Eolibn. Upper several test *re partiy 'esota"; poorly aorled; lottlt'ly induraled by soil-llme cementation, bedded; vAribe in tIeh,,t "'s is 1rzrd with irregularly disperaed whitis ca- discontinuous, but can t clum narbonatesegregations, espe- wround three sidesof this Fg I I i ; cialy along bedding plane, oit piches out 20 it to waes"t.I t a crackh, and on diperred cylIndrIcal very weak soi dcsrll " il '.Jlu- 1 6 bedI" Y. to Y. in. di.meter; Itater uppermost scel Inch,". have bollow centers (gmetrally leon vium (slopeosbh) .- WELL 1008 141 STRtATIORIAPITC RECT103(S,GOUI-PSI IFILM BECTIONS, ASD DESERT, NEV. T~ANLZI0.-81*41firesliti eSUUO"sa-CoOftIUtd LAf E LAHONTAN: 0901 wY, CARSON tsri1.* arte--c-t- -e 140 1 it TA. l0-&dSfreirapfeAW sectiont-Contlnsed TAUXS1O.-61rstfigrphic, SiCefOns- -Conltifie it 10LS lrwtetina 45 r7_ As TA L - seetion55-.CFtA~ Sunajug foematlo~ontl5Oed ,thi of ci ..espe sfapraphire section of ihaiut frjrA %slr a L1e untit.Conttnued easrrefafed ne,ol. II wad rhty- seetionexposed Bebanoformation-Conutiued -enk (.tkor4 r Mila tonn) sf Bsaekg Modebualm eontalning fragnataef 18 N., R. N e.. &trativrapt'e wes tide Nvcor. Aee.54, T. UVO (Depi column irdiatese.sproittole pumie, in Cvoo 4tke ploain. Top of ceclson, Upper member-Continued rs, T. 17 N., R. SO .. ouio glas, white i beankof drainager eanal the un- and eensdderebls balio pebbles, especially cmfn laictae.)e atfildo 3,918 feet. In a 2. to 5-In. andeslte er basalt, lnthudlng deraides, 2.3* r A. of medium gravel- 0 2-4 3 BuneJug formation: 1ocsiy Fallon formation: layer fll). i A,*I/el rsd to black senrbs. lake and Interlake unit: Sharp nontaut. Upper unit: psagltio Young 1. Olivine b aelt, black, vesicular 10 ft oiireesen Sand, fine, with small calcium catibo- Dendridimember: tuff at ba. At 4,590 ptak I. _ 1. 5 to fairly dense; almost no in- ate nodules. LACSestt ...... 6. Gravel, very fine, and gran. this unit is aboem y thick 1.0 2. 5 terbedded tuft. Westbars t Sand. silty, Oin, saint. Lacutrine.. le nsad, coatese down- and ineltdes, at op, 25 ft brownIsh-black to purple. Sand, very fint, nieaetous. A.uval ward; fairly clean, slightly pink quantslatitob o rhyo- 4. 7 brownish-black along Jointst 75-130 100 (Carson River channel sand) . 1.5 cemented by dthold tuta; iit, strongly fow-banded; small clay pellets; 10-25 percent dendrltic- local unconformity. light- to dark-gray $and. fne, with uni:t 20 it Alloviat .5 4. fragments; remainder Lower 50 ft white pumice- neary black, mleacous. tuts red baoltle(?) perullt; are basalt, andenite, silici. 2. In north, either ous tuft and tuffaceous grit, Disecnformity. or highly vesicu- unit: tugt, and rbyolite. *ufi-breccia and gravel, with several feet Third lake fied basalt filo grading down- ustrin t...... , .0 .S LAcunttine ……------1-1. 5 2.5* lar of yellow toui containing Clay, black. black to red. In contact. ward from some mWAefragmenta near SecondIntcrlbke unit: Sharp to 15 It red scoria Lacustrine or (transgressive phase); south, 10 ...... - a 16-94.4 300 Sand, medium, clean. Lower member I to 3 It white base... . . I + 6 5 cobble to mtedium, at top, over adui l------7. Gravel, 20 ft buit- S. Basis flows, undifferentiated. overlaln by persistent I- to ash, over 15 to Black to dark-gray and dark- male tuff ...... 15-35 .125 2-In. lsyer of cellular and colored greensbh.gray basalt and (or) In place. Lacus- 3. Andesite, basaltic, olive-dark- commonly of gesnnfpit lithoid tufa e pbe- andesite flows, SlVT) eec.'t, T. 18 N., R. So E. XoefAe6elank _--- -_ 0. 5-4 7 gray, a few plaginCo altered------100* 400 Sell . op of trine - ground. somewbat greael bhr at bele oJ sounlope, nea, very fine, clean, nocryatsin apbanitic in S Gravel, silky Base not exponed. sec*ion,allilude 3,990*5fd. heavily cemented by lith- ma with a peculiar O. 4*L luster. Thin platy structure, 7M.- in old tufa. Larustrine ..... 2-2.5 Sehoo iormation: contorted, not Ssiiraphic oecios P. Sand, silty, fne-medium, commonly ssejag fersonli do itps ( e oosWlsy. upper membtr (bearing Tloyrhsoil, 0. 2-0.3 6.7* parallel to fino. Apparently Rwaqtg lMtaons. tiny, saline. Lacustrine.. 0-50 165 cned O" wit fae. of 4,880.foot assanloa, eroded): Interbedded thins southward ...... Ave. S (T, T. 1. Sand, fine medium, silty and 10. Sand, cose, NEh(NE)4 *c. 8S .ud NW)'oNWt somewhat 4, Baaltorgndesiteblack,platy; V. (Doept catams isdicate eataatire thickne...) gravelly: pale-tan-gray. with medium, purplish cast. 17 N., R. SO Lacuntrine ..... O 40. 5 7.1'* has alight Lacustrine. Lag gravel of pebbly. with minor small 11. Gravel, very poorly sorted Porphyritic, Bunejug formationn: pebbles and small cobbles of plagioclase, eet inMC pebbles, some cob- phenocryots Upper unit: Olivinenow., owes maca,._ 9 at surface. Very limy (sand, pyroxene, basaltic born- bles, and a few boulders to Oilvinc batraam nOD, vesu (eroded calcareous horizon blende, and olivine. Prob- ular to fairly dense; almost nO soUl).... . l 2-0. 5 0. $* more than I-ft diameter). 0-356* 185 of Toyeh &1* ably absent In north-.. . interbedded tuff. Weathers an 1, but lenssandy; Lacustrine ...... brown- 2. Same (bearIng Churebill 5. In north, mainly red, purple- browninh black to purple mostly poorly rsortedcoar. WYemsha formation basaltle(7) 123 125 red, and black ish black -..------__-.-__ medlum gravel, with mod. soll, eroded): meetly red alluvial, ua follows: scoria; In south, Loca uneonfortity. erate sollime concentra- 12. Gravel, red ecorlaceous at top, about 2 ft sandy basalt and Lower unit; tIon. Lacustrine... --.- Si L.0* (a) purple to black 20 145 gravel (meetly coarse, basalt, some I. Red batie tuf-bre...... 3. Sand, pebbly coars-inesdlum, ine (I. middle part) and medium, and fine *and and boalt 2. Bassitle andesit., oilve-dark- moderately well sorted; red to black aeorna with 0 Spas paigiolAsse phe. Thick- granueswitiveryinegravel, gray, very limy (soil-line. s ft pink tuf at be. ground- some pebbles to 4 In. dIam- to nocrystaIn aphanitte ens to 1X ft 200 ft to west. Thickens regularly from This 1.6O* eter); moat pebbles Angular msawIth ilky luster. LecustrineO-0. - 5-0. 7 to south- 3-73 220 commonly to aubangular; considerable north platy tructure, Upper member: bsealt, black, vesicular contorted, not paralle with oil-lime concentration (erod- 6. Olivine 35 ISO 4. Sand, pebbly eoarse-medlum, and soorle. Abrent in north, very limy, ed C. borlson of Church- pcorly sorted, gradually thickens south- 3. Basalt or andeslte, dark-gray. (nearly III soll); large percentage pale tan-gray surface ward. to 60 ft St extreme alight purplish east. Thickens to west. of pebbles Are platy, white). or less eouthwest edge of moun- BparIe plgiolasc pheno- ...... 2- S 2.0*R checked and more 0-30* 245 30 210 Locustrine next S ft tain- .-...... eontact, discondormity. "rotten"; (b) Sharp pebbles snd 7. 8lcn light-colored tuftaceout red, mafe, wlth platy llthoid, cowting cobble gravel; 4. Tufi-berfeis; 5. Tufl, aubangular; cone. In north. 15 to 35 ft sore red to purple bigily cementing oedlum cobbles mostly ,..* 120 330 and (a), thick, with About o ft light- vesicular flows - ...-- . (some pebbles to (e) lower 2 It similar to gravel sand; mostly bulf to pink tuft and tufflee S. Andeile or basalt, dark-green- diameter); pale but has less 3-4-1n, 4.54 12.6o out gravel at top, remainder lahbgrsy, plty, resembling white, locally grit and very fine gravel.- Go 390 grty, nearly gray to nearly white tuitace reddish tinge, prob- Ectsa formation: unit 3------with to aomgravel ad waterlaid grit, liltold Ilo of 13. Gravel, boulder (boulders ably early diameter). mctnber. On south more than 2-ft upper ...... 1.5*e side of gravel pit. dimin- Laciutrine ilbes to thin coatings on Bue not exposed. -I---

142 LAKE LA3EONTANt: OEOLO(IT, CARSON DESERT, NEV. STRATIGRAPHIC SECTIONS,BOIL-PROFILE SECTIONS, AND WELL LOGS 143 TAALZ10.- -iltmiligaks #001fous-.cnotftlned Tasr I0.--Stmtiffraphilc ectioss-Cooflnued TANAelO.-Sr1*llg,-,phlc SM110",c-Continue TAste I0..-Slrstigrapkic tections-Contisned ssas- 11T-Cselac tr_t6 o ue 5.-tlss, 77-CcsUassd SolWell SoRdaicl Csrol... (il. oAt, 7.7 mil.asrin dotiow s,t Bunelug forNatlson-Continued Eets foroatioUo-Conotnued Twk'"' Dre A . -1 Apped Bunejug fcrmaton-Gontlnued Probably hbgfit-ae offshore depodit ofd 1 - Lo rer unit--Continued froem Safi Wells, NE)INIV~( am. * (usUwer)T. ) .a Small angular unconformlty. 6. Tuffaceous so0. Top 15 ft U.'n dsos (lad) o"n, oa Eetrla rke: I .TOP4of ecti-nafilulde 4,00±20idfc. 3. Asdeslte and(or) basalt 8ilt, teak prlamk ti:truture and brick-red to purpish tuff; dark-pay------759 195 middle part, white to light- Sehoo formation: 15± 210 PDle rebrown color suggest in 4. Tuff, bright-red to pink.- -- L- ray perlitio and pumiceous Lower member (bearing Toyeb o): ciplent soil development. Nlw dpa (1.4o S. Andenlte and(or) basalt flows, cuatrine ____,,----,,,,,,,,- ,SgeJ0,5± tuff, well-bedded ast wwater- Gravel, medlum pebble, with some dark-p.ay _ 20* 230 laid, with somO bhaltie or Saznd, very fine, iigbt-tan. 1au cobbles and a few small bouldes 6. Tuff, pale-pink to light-gray; atrnde very ___-_- _ght. _--t aS d andeaitle fragmentb; lower (rarely more than I ft diameter); 3-fl~~~~~~~.SIi poorly exposed. 10± 240 Probable disconformity (recording part, ight-buff and light. bearm Toyeh soil. Lacustri... , 7. Andesite and(or) basalt flow, subaerial exposure?). grayish-bufftuff _- 50 440 Contact generally sharp, locally grlda- dark-gray ...... 75± 315 Silt, elayey, silt, and osomesilty cori- tional. Lower member and Wyemnha 7. Baalt, black to red, red clay, tan-brown, witl chocolate- formatIon undivided: S. Tuff. Upper 10 feet reddinh, pink, aceous be alt, and red ae.ria brown staIning along irregular only In unconnolidated, poor- orange or tan; remainder white (exposed northern Sand, medium, prismatit partings, and carbons- patt of west face of moun- ly expoped. Upper part Ib s0nd of or light gray and containing much pumice and light-colored Melte. neon.stt~r ks (root remains7). tsin) 50 4904 lower member of Sehoo, dbecon- Lnstrieas-, coot,,,, ai, 2 33± formable upon local lower part of Locally a few feet of dnrk-tan tufl Base not exposed. 50* 353 Clay, silty, gpyish browr, with e"lion sand of Wyemah- . 4-8 10± at bae . ------...... Sharp contact. 9. Andc ite and(or) basat flo, some whitegypsunm streaks. La- , 6 33. 5 ietss formation: dark-gray to black,------50g 413 cuatrine -,,,,,,,,,, Si nd, medium, fine, and very fine, SE)i c d (aacaeee d), T. 1e N., R. 31 E. NortAest edge Gravel, pebble to boulder, boulders gen- Bare not exposed. interbedded, wel sorted yin, to rft n U of Cocoon Ifnicwrins. Siregosphic sooion ezposed in hunk of eraily leasthan l% ft; subrounded Iustrib ,edd, w l- s . L,-- 1 5 3 S subangular, Indistinctly bedded; round- deep o y(to rost of adjoinini ridge). Top of socion, nliode (?): stones all of Bunejug formation. SM)N1'13 soc. 13, T 16 N., R. M E. FSenkt of #oUly akrossgA Alluvium 4,SO0*20fee. Gravel, fine, Angutar, practically all Lseustrine ------2-4 13±I Sigh graet lelinta men el nort5 froun of Decerl loontano Top thyolite. Anluvial gravel? ------2 37± Sehoo formation: Trkh.as, Drots 4,toO0±t0 frril. Itses) U10,5 iocaldlronformity. of sccIior, slilade Dbsnodormity; probably repre cnts sub. Lower member: (bearing Cocoon soil): Trkk.,. D PIA Paiute formation Sehoo formtion: zte) 1;f sDeri exposture. b ravel, fine grades do-nward to Gravel, poorly sorted, coarse; boulders Sand, medium, yeluw, pebbly in top maximum diameter), cobbles, Lower member: granule snd; sparse snai and os- (3 ft Gravel, rhyolte peb- S meiSome ,hite lowy *pote, probn pebbles, sand, and sit in varying pro- fine, entirely trarode shbell; 2 In. medium gravel .I bles; thickens northward. L- fblySoD lime (pwitbmy inipientpoil In portions; roundstones mostly nub- at top with local cellular tufa eustrine. , ---,------. 2-10 6± profie)ys llli (pcuosrineb . . - t s 37i 6l place. Lacutlrine -,,,,,,,,-, 3gr 3g angular to angular, al of Bunejug for- provel,One, angutr-, mo. rbyol7te 3 matlon; Indistinctly stratfied; dip. Gravel, fine and medium, entirely medium, some granules; snail alcustrine , angular, mostly ch,, -,, 38 Sand, About to 2' balnward. In places rhyolite pebbles, cemented by fi 1 Bas sot exposed. andestracodeahelbs Lacustrine-- 3 top severai Inches have red-brovn, lithoid tufa with 0 to S ft of cellu- 2g 8± Sand, on. and fine-medIum well- clayey matrix, relatlvely free of calcIum lar tufa at top. Laeustrine NoTm-The banks of a main wash Y. mIe to the southwest ex- ostracode shell. onide horlson of Disconformity. sorted; snal and carbonate (eroded pose 20 to 85 oeotof &etza formation between Altitudes of - ,,,,,,,,,,,,,,,,- 4 10± remainder of thickness b. Lacust-rne Cceoon soil); Ectts formation: 4,380 to about 4,200 feet. Unconformawbly underlying cemented (C.. horinon of thb soil), with regreasve shore deposit of Sand, fine, bright-brown yellow. Probably At an dense cairhe In upper 4 to 8 ft, de- gravel and tuts of lower member of Schon formation Locuatrine ,,.,,,,,,,,,,,- 6 16± second Eetsa lake: altitude of about 4,300 feet (top of section) are the follow- creaing below. Base not here eu- i Gravel, cobble, with much Intersti- Sand, medium, grading downward to posed, but unit thickens in exposure send; ing sediments of the Eetza, from top to bottom: 20 feet tida fine gravel and coarse 5 cobble gravel, IS feet sandy fine- to medium-gravel, a 25- coarse, well-eorted. Lacutrn - 1 17± locally 30 ft and in plarces rhyo. upstream to percent of roundutonm are foot uone of alternating sand (coarse to fine), silt, and some for. and ande- Gravel, medium. Ltcust irne -,, 1. 3g l& 6gc rests dineonformably on Bunejug llte, remainder basalt clean medium gravel (the lower part is mostly sand and ms.1on ------10± 23± site; many are subangular LA- bouldere to 2-ft fine gravelly and). The last sone tranogrenes Sto 25 feet Gravel, boulder; eustrine ,,,.. ,,,...... , 13g 21 g diameter. Lacustrine------±--- ii 24. ± 'I of coarse boulder gravel that is the baafl deposit of the Probably offshore deposIt of aecond gravel can be traced continuously up to Wyrmaha fomation: Eetn. The basal GeNeralstratipophic s-di.. of Bnrt ja formnliont in central Etzs lake: the highest shoreline (Lahontan beach), which it underlies. Sand, medium and Sne,pae-yellow. Upper fine cone (top to bottom): 3.5 Coceo Mluefanirt ator- otAh edgeof CarsomLake uadrongle,see. nh gray. Eolin -,-,,,,,,,,-,10 34. SJ 8 It 1 (uaurrefefd); r. 16 N., R. !O E. ond r, i8 (unsumrtd), ft alit, light-gray-y llow; 0.5 TAste 11-dSeif-pes~ib setions it Ik ohecolthe Catrsn Deset Gravel, boulder, and cobbly pebbl. T. 1i N., R. Sl S. (DepthAcolum indict,. oppeozi.ute caem silty clay, tn; I.S ft very fine Atrta Lacustrlne. Bee not here ex- ) sand, lean, lan; 1.0 ft silt, tan; Irdce tAickfes Ilanpl.oril me e a- e. - sse sl. wkn ambau 0l satMa lPhk tk-s expoed, but unit orerliae Bunejug 0 5fh very fine sand, tan. LtAcua -ad.ii har Is tb,. IfIsad Ill formation about 200 ft down- Bunejug formation: ""W"' trine, , - - 7.0 25± SOS ream, 5 39 54. I Upper unit: 7jsUl rjos tiei Probably transgreasive shore deposit of sail ernai-.etlb 1. Olivine baiAat,dark-gray to blabk, srcond Ectna lake: Type localilty of Toych soil Loation: NE01SE) sec. 22, T. Drr-l. so vesicular; commonly six or more Gravel, boulder, with Interetitial 19 N., R. 29 E. Topo#rsphic posirio: near top of bluff on east flownwe ,,,,,,,,...... 75-100 100 fine gravel;very angular; enirely side of wash. Slope: 10 percent. Ermion alight. eposars: Type locetiig of PD;Iat forwr mst~anzd Cuee scsi. tOrneralierd 5 feet. Parnt, t Local angular unconformity. rhyolite. Ltcustrine or alluval.,, 2 30±e vertical channel dug In bank. Altitade: 3,950* )tostiycphir oertfi, fJo eul AsrAnodjrd feet s osg hon ks of P n iul Lower unit: Discomtormity. ,siernal: eolian send of Turupab formation. Orclying maierioi: Warh, ao.t 0.9 milt sbore tee shosdseed .pgom rood from 2. Tuff, mostly light-rpay ------15-25 120 695-5I 50 t64-11

II i I STRATI0G1APHIC SEMTONtS, BOIL-PFtOPILE SEMrONS, ANtI WELL LODGS 145 LAXE LAHONTAX; GEOLOGY, CARSON DESERT, WR3Y. I-I TAsca llB&Oi-preftle seccions-000tinoedl TA*tE Il.-So6p'totte seetfons-Continted II.-SgoiI proftle seotios,-Contimse TASZ TrALE 11-Soiton pretle serfContlnute JWII .eom. mello $15...c e54sed 8. o lb mltlO n l55 -. a scattered oh*d UIIil t o ts. eolian sand of Fallon formstlon. Vegetnioen: - -t Relict Toyeh soil on dendritie member of Seboo formation. seal. (Afripfcr colowfai/ofW). LoCatiOn52about 300 feet teat Of road on east side ot Rainbow 16-96 sO C. Very pale brown (IOYR 6,3 to 712) 15-22 7 C Light-brownlsh-grry (iOYR i2i) sand; b (tlt mos) 14_W,) Mountain and several hundred feet south of 4,16040ot bench medium "acd, atlcegly to somewhat uilan s.ructurc, nearly single-grain; emticl- _-- ...... Light-gray (about IOYR7j2) coarse mark, in 8X wec.17, T. 18 N., t. 31 E Tepetriaphic peOcWWO eaierreous,wrtit white calcium1 ear sand; *trtectfe, single grain; coseftt- cxor, nearly loose. top of lake bar (highest shorruine of the Uiddle theboolake)- onata streaks. 'OODMUo,* and tcre, loOse. (Eltan sand of Fotion 22-40 1 C Light-brownsbh-gry (IOYR t/2) sand; Slope: I percent. Briomo very slight. Rposure: dug pit. Irregular cnneetatitons; otrcf.s, formation, overlying the Toyph oil.) dructure, dingleigraln; censisteece, Altilde: about 4.175 feet. Parent material: sand of dendeitie strueturelesu. massive to single- loose. Abrupt wavy boundary; minor dbeon- umemberof Seboo formation. Orerbi'pf material: none. Vcs0 ,ca- rain;consirstce, very hard to loows. formity. I At ths ltamly tti se3r) Imbsesob b" . -. bat erded. thel tihithe's tolion:grearewood and shadotale, about 6 feet apart; mine Art- CourentratUon of calcium carbonsto 0-3 3 A I Llgbt-gray (10YR7/2)sandyloamn;sfrse O.M tr I1 IoItoe t "55I* .i s st;" rnoeobou.Ih. A t mIsel)brteloo stemts spisnesccu. decrease somewhat Irregularly from turc, weak vesicular; sonsistetcc, hard. istsher .Oh cIrobabhr b ,t pos-Te s see 7W. ae ,l -,st tt by Ite top to bottom; upper 2 to 3S4ft Abrupt, smooth boundary. s54masemco- k - 5s4,e bawb, a fn ..sk othi snl. -ss~s Pssss vcecm. M-~32B. J* ) ti=te &Z has numerous to common carbonate Finegraveland toao"trtd. 3-7 4 R I Grayish-brown (10IR 5(2) sandy loam; -075-0 O75 Lag stresds and coeretlons, and il rosa- sfrurfu , moderate to strong coarse gravel sive and focally almost cemented A.seliots el physical aned chmimeu properties Abrupt, smooth boundary. columnar; h~rd.banideore and brd to very hard; remainder of Clear, smooth boundary. tlfma o bod naulyssby M, E. 5010ftw. tn leesotiyof Csi ho,. tklk.et 0-3 a A Pinkith gray (7.5YRZ7/2) very thicknesa has some to few calcium fine gravelly sandy loam; 7-11 4 Cra Light-brownihi-gray (10tYR 5t) sandy cnes carbonate eonrentrations, is mrss(ve , I str-cesw., strong vesicular, loam; calrareoou, many irregular white IP01.,I sisgle-grain and slightly hard to COfoin. eIk roamreplaty; conssitence to calcium carbonate segregationm; #true- =I (S"mS <2 M. OOE-1Fe to~ t looe, except for a YIn. to l-in. I-re, weak coan.e columnar to weak i hbrd, brittle, harsh, floury. white ealcium carbonate cemented Abrupt, smooth boundary. coarse ubhangutarblocky and weak in depth. reddish brown tSYR 613) layer at 53-54 coarse and very coarse granular; con- A21. 1...... W4 I a. II 3-7 4 D Light gravelly stundy loam; stlrc- Diffuse boundary. Otsisscc, hard. II O I 1.52 . I 0.1 004 1 0 lure, weak roarne columnar to 712) loamy CC_ 1^.}2 *10...... 96-116 20 C Light-gray medium sand (IOYR II-is 4 Crs Light-brownish-gray (IOYR 6/2) C .... .1.- lb. ss.u 10 1 .m I LI I with spare white calcium carbonate to @m l .07 moderate conse subangular sand; siructura, weak roarse columna c .. - -1 _ 1.47 nt r blocky; cons;stenec, hard, streaks and concretions; structsre, granular; coniistlece, softL weak roaws slightly harsh. Some soft siugle-grain; cossittence, loose. I7 calcium earbonate egrega- "a rolb ossb Chceft *ad phyoscof pMoertmft Type loaitY of Harmon School soil. Locetion: %mile north of old Harmon schoolhouse; exposed In banks of branch irriga- tion in lower prt. sol 51rsttrtr~io iro~i Y~ c ' hM ri.E eecrCO tion canal about I50feet east of county road bridge acroesmain Irrigation canal, SWYoNW3%e. 24, T. 19 N., E. 29 . TopTogorpic Clear, smooth boundary. ltae,,seds po0;tion: plain. Slope: none. Erooions none. Bxposure: vertical ehannel dug into canal bank. Altiloe: about 3.932 feet. 7-14 7 Cm Light red-brown (SYR 6/3) grv- from clay of Sehou formation. Owlrtcrinf caterial: ely utnd; strutewrc, weak POrcel ,sal:a coliuvium ot-upper tongue of Indian Lakes formation, derived s co,( noesr upper member of Sehoo formation, In which coarse columnar; eonoirtnce, Dopti tlO." l) ie~ dcea mlse- cemmP e nsl P;01.001 C Nt eabnose Harmon School soilir buried beneath about it inches of silt, fine sand, and banal tuts of d sssllC -CZ s ,e Po ) t w ol the stronger Toyeh soil hta developed. The Cca horirun of the Toyeh boil extends down into and somewbat modifies the Harmon soft to slightly hard. Slight School soil. Precita7tifos 5 Inches per year. Narl corer: Sucroa&sw rermrsisuhs, same shadncale (4riplttc conferifolin). calcium carbonate aeoumulas- Pasd and precet wor none. ton. 4-15 0.4. - - . 1.8t- _6 . . ~~~~~~~~~~~~.-.l itl...... 0.0 . .. Clear wavy boundary. ...5 asJ- ..- to Afo 3.7 14-35 21 C Pinkish gry (SYR tl/2) gravelly 2442 .. . 3.40 S7.5~~3.1 ~ ~ 0...... 0-3.5 3.5 A __------_ Light-gray lay loam; srdurct, vesicular, grad- Toyeh soil (vesicular horizon). sand; frucsro, aine-grain; ~~5. . 4 .5 . ~~~~1 00 as5 *.l : GM . log to granular In lower part; cansistence, -4UdGlvooe. - .141.31 a t IL# . .1 seslliceecsO lowU 1.0~~~~~~~~~~~~~. harsh to ttoury. wis. . Z...... 0 Abrupt boundary. Type locality of Churd ill soil (sampled and described by 3.S-8 4.5 B. _,--__ light-brown loam; structure, weakly columnar Toysh soil on silt and tine sand of MA.E. Springer and R. B. Moerrson). Location: eat bank of formation. to granular;-osisfenc, hard (dry), brittle, upper member of Sehon wash gully on west side of Churchill Valley, BEMWS oft. la, ft or k _ , Vetoecos 5nt f nio <2t Gradual boundary. T. 1 1N., It 30 F. 7pogeaptic positiol: steep bank of small 8-11 3 BrC. .. Light-brown loam; 0-roru , weakly columnar; Toyeh soll on silt and artly lithold mountein wasb. Eurore: vertical ehannel dug Into bank. tl)~~_." ~~~~~~2'"_ __ .&L_ a_ IAwons- I e 2 5m *enak 1 5 1ne. -bn 3 1 4 ea0 5 e O m

LAiE LARONTAN: GEOLOGY, CARSON DESERT, NZV. -.I 4 STRATIGitBAEC SECTIONS, SOflFPROMfLE SECTIONS, AND WELL LOGS 147 TAux se.1Rolpesiedeion-Contlnned TABLElI.-Solt-profilc .etiOas- Conrtnuued Turnv l,-O, -sfi sectiouss-Conltinued ifi, but sage (Arie- ia vlrieuuIS), and rarely other shrub b.0 Siw ir .0.5 1S-caiAs w 5.0 Vr.4I -a- 459-C..ilasd 5.0 ,A.1 -eB.. specles, together with spArse KeaasU(mostly BoeAms. Oweyitnsg materias: 1 inches of eollan sand of upper member of 05-Cn55s.5d lecle ) :1.: and forbe. Moat of bare pert of surface covered by desert Fallon formatjon. ttI= led... -. - O djsrtse .'_.Ai pavement oi slabby blocks and pebbles of basalt, only one stone Abrupt, smooth boundsry,.ob. thick; generally oriented pralle with tbe surf ace. Top surfaces (_r) 4Samm b eWpH - Abrupt, smooth boundary; probably minor ably minor disconformlty. of atones re mostly shiny dark - I A Light-gray (10YX 712) sandy loam; dieconformIty. brown, dark reddish brown, to S-S 6 (1hes) Reddisb-browen (5SYR 5/3) stony nearly black duo to desert varnIsh, wbereas under surfaces shtrsofre, wesk vesicular; ct~tisew, 2-4 re day loam, eonttris some soft 4 H Reddish-brown (5YR 5/ clay loam; dull browniab sIghaiy hard. ;iesofam, gray or gray. calcium carbonate In streaks moderate coarse granulai; 1-3 2 A Ligbt-gray(10YR7/2)Bandy loam;frlts- ceai ,e and bleh; sfasre, ha rd Contains more roos (tlbnd -I Salae D.-ije .. tur, very weak vesicular mad weak eOre medium than layers above and below. - t gramular; cteiafence, slightly bard. graInula; crstence, friable. Clear Irregular boundary. Top 2+ .... Doser pavement o dark-brown-var- Abrupt, smooth boundary. Clear, wavy boundasy. ibshed, Baggy blocsui and pebbles of S-14 6 Cca8 Llght-reddisalbrown eg a3 .e Llght-reddiuh-brown (5YRS6/) sandy basalt, 31 4 B Brown (10YR 8/3) loamy sand; truic- (5YR 6/3) covering 90 percent of surface. stony loam; contains much soft loam; frufdre, week granular; Crniu- - Nto,, very weak crre granular; sac., slightly bard. A few roots; 0-I S I26A Ptnkihb-gray (7M5YR 7t2) very mne calcium earbonote; W-rtrfore, many sandy loam; atrature, vesicular (ou- ,, eonistla, slIghtly bard. calcium carbonate concretions below 7 7-13 o Bra Oraylsa-brown (tOYR 512) medium to coarse granular; merous spherical or tubular voids %to sand; ahruc cunsiafoac., triable. In. depth. ts,, very weak coarse 3 mm In disneter), moderate coarse granular; Diffuse boundary. Gradual boundary. oAritwteure, very slOt; loCUly slighily columnar and weak medium platy; 14-20 a CCA, Pink (S YR 7/3) ntony loxm, a-ilh 9-15 6 Cma Pink (5YR 7/3) to wbite gravelly sandy cous.itncse, slightly hard, harsh, floury. rairreous. loam; much calcium carbonate Ir- contains many flat calcium cr- Cracked vertically to form polygonal Cler, wavy boundary. bWate concretions; lerocsure,masuive; 13-20 7 C Pale-brown (10Yg G/3) coarse and are, mPssirO;uonslrne, partly blocks 2Y,-4 In. dianeter. cemented cunuiotenee, cemented, very hard. medium by calcium carbonate, Abrupt smooth boundary. sand; single-grdn, loose. non. very hard. Grdual boundary. ralrareous (parent material) Gradul boundary. 15+-F Cr White calcium carbonate cementing 1 5-7 4. 5 B, Itticftlbrown (5YR 514) clay loam; Chreicro Adupbysicrl proptrties frac- staturfrt, moderate medium granular 20-36 1 Cms, Light-reddish-brown (SYR 6/4) tured dark-gray bssalt. IAnaebuO,b sr..II ., isotr--mia. nrasirv to nuciform (upper )S gravelly loom, with leu calcium In. Is fine- Nor-le-d hm-X-1 o0d Oto 2 r1.h. p~bdr h.J br,.d Ilete,.b. Ibo granular);eonsiteiesr, slightly hard. Com as .oD p.PDr .04d a m1a Do Priderly a pr allisI mt. . son Apntirs- Peusal rNt Co. ftr carbonate accumulation than Clear. irregular boundary. Ossuor ti 05~eI r Csam pn (.rhsTr CJN lps(wb above; aleriure, strocturelsas, 7-10 massive; cousiklcre, 3 Sca Light-reddibh broos (SYR 614) clsy alternate Chemirci ssd p'.eisal prupertira loarm;ntrlure, bard-cemented *ad loose layers. moderate medium 5 .- raisB n1.0 .a i_. 0.4 NOorE-In places granular to nuciform; coRsiatenoc, calcium carbonate fillbcracks of the shattered slightly bard. Bome calcIum ntcarbon- a .- c-is l i e as s a s . e as . bedrock to depths of 8-10 feet. C- I asss"l, s I u.2 ate concretions. A"iyae oqfphysise and dtnmical prrperdirs Clear, wavy boundary. Isa.01izsbad .useITOr Nt.R. a8rrer. a.itr w as caimlbei mowusass sc ot o,sio s

149 STRIATIORAMEC SEMlON3S, SOIL-PROMlE fiECrIOllS, AND WELL LOGS6 CR01.00 T, CARSON DESERT, NEV. 148 LARE LAHoONTAN: Tawt IR-409' of 10elto-ContlttOd TsI12_-LogO 01 ,ell,-ConitlnUed Well WaSab-Cnels.a4 TAwax 1L-8011-proftlc &ectione-Coutlimed Wallfire teL---C..Isse orealnuncertaln-Contlauied V41451"' Iee sa 1944. Wo to oor* off lower in 19045;ewCity of Feallon; driller,. MA Chas~inaPi at P. Bhuep, Fallon, Nmm. Drilled 88 758 Chenses and physical propertifir-Contlnued -I Wiserfrort pea gravel of 98-100 faI Clay,' gray.1------a~suro of vowe for Fallon.. - port of Wul; meine Clay, green-::------28 790 -- --- on Fatwd-Iea dbulballea Fallo fnematlo: (Ad)... W clay, gray ------Wyeon andWenha formation: onwJV Clay, green-gnra ...... - ... 26 886 Surface soil ------Clay-4~~~~~~2 28 Clay, gray, and streaks of saud------76 962 ins salafrs 644 Sanld, line ------7 12 clay. gray-...... 94 1, 020 Satna and gravel, water-b ri-g--- - 4 16 Sand with streaks of clay, aqluffer ...... 34 49 Mly, gray, and sandy grit------24 1,060 5,015.1555~~~~~I '4&. Wyeenabaifformation: 10 70 176 1,288 2 Band. blavk ------Clay, gray ------a-liIt itS If1 0wOiI, 5045l Clay, sandy ------4 S8 9 Sand, fine ------2 .5 33 ' Clay ------Sand, fine, and aou cla y.------13 clay, aquifeOr------3 62 1,310 84 Sandt with streaks of mly, gray------Clay, hacd, blu ------I Mly, sandy, pray------17 1,327 2 37 Clay ------. 9------8o m W5m 14Lmmm * and, fine and soft clay ------gravel-, good aquifer--2------Clay, gray------3 1,330 "Tule" sand, fine, (with dark-oolored or Clay-...... 3 103 Cly, sandy, gray ------32 1,862 32 89 ganic matter), vrey bad odor ------Gravel -2------103 gray------27 1,389 bad-amelling clay, Sand, coarse, and gravel; Clay ------107 Sandstone------1 1,390 79 . 1 {ch949.4 5 1? M 10 144 I water-.. .. 10 Sand, black, with sulfur w"ter ------110 gray------27 1,417 4 83 Clay, .'Tule" #and, very far - gray------9 1. 428 (swamp) Clay, soft, gaud, coarse, and gravel; 'tule" Clay, hard, gray, 'and dind------2 1,429 water-...... 8 91 SWISEY4 ArM4,.18 N. I. 8 .;oladeshoal 3,980* fedt. 12 3,440 Metl Clay, soft, gray------Clay. brown -1------92 Driller'o log of aniur well owener,Beef A. P/Iun; driller, 1,444 100 1949- kk- D Clay, gray------SfAnd,fine------8 Meyer. Well ompterled August 18. Clay, gray, some sand streaks ------28 1,472 9 109 Sand, fine, and gravel, water-bearing --- Fallon formation: Urn1 (ot Clay, grimy, green------From 1. 472 Clay, brown -- 1------110 Topsoil------10 10 13 123 -;gallon fort. stion: Sand, ADOe------Wycernha formatior4(?): ...... 5 1 Soil and silt.------a 3 Clay. brown------2 125 Clay, orange-8...... ------11 14 ------2 127 8 Sand.------Clay, brown, sandy Wyemaha formation: ..... 0 4 3E)4NIV)oae.1 .17 R.9.Ptin1Lea~f~~I., Sehoo formatloti: "Tule" (organic) clay, black, sort - ---- 23 150 Sand, fine ------14 28 Is 283 Clay------"Tule" (organic) clay, brown. soft, sandy-. *Clay, black (swamp deposit) ------80 -Wyenasha formation: Sand, coarse, and gravel ------2 187 Sand, black, fine ------88 Sand, hard water.------a 33 Clay bard, black ------170 3g~o~cooCe (asoOl now a Mlle SyeliOl il Co. and Clay, blue.------41 Unit unknown: Sand, gray------" ByndcoleOilands. .-).ReprtedIdo deph ether 5,151 or Sand, blue water-bearfng foul-inmeflolg. 41 52 Clay, fine-sandy, and mud ------139 308 Sand, coause------2 67 3.30 jel(R~kade,194);redryrigsee 5,38fsed; churn- Clay, gray, tough.------3 87 Clay, soft, brown ------5 31 Clay, black -8------78 ------6 93 17 320 Sand, cecan, brown--- Sand, fine, clay and mud------*Sand, ray------3 80 Well I.. ISL Clay, lIght, sandy ------2 332 Sand, fine, blue, water-hewring------3 83 ,Fallon formatlon: (tr 2 334 7 08 20 NWI"NW)( see. £4, T. 19 N., R. 97 E. Terrdee of Careen Clay. bard, brown ------Sand, fine, gray, water-bearingI Surface-20 2 338 gray, wae-beaing--...1...109i 5 4 .Rieer,alsritadoe4,012A,3feel. Diller'a legof wellenKen Oqden clay, gray ------Sand, fine, BebeO gormation' Clay, soft, and mud------56 392 *Clay, green, sandy------2 1to Mly, stIcky, yellow -2------ranch. Drilled in 1044. 114 gand -8------3 455 tSand, fine, gray, wetor-bearti-g4 Wyerniab formoation:so 7 Use) Vie Clay, blue----1---12---8 Sand and gravel--8------78--- 3ndian Lakes formatIon: formation: Sand, black and white, water bearing ... 22 147 Clay, blue -15------i 90 3 458 is 161 Sand, water-bearing In lower 4 ft.---- Buffatt, hard, black ...... Sand, black, fine, wLAOte-bteaing-...... i Gravel------28 118 Selboo,formation, dendritie and lower menebers: Lava, porous-...... 2 460 Sand, gray, coarse sod fine, water-bearing.. 10 171 Gumbo, black, g1a1Showin~g------15 130 - - - - 14 32 1s 475 Clay------Lava, porous, slIghtly birder...... We." W~ UL Gumbo. black------64 194 middle tonguef(?): ---- 40 815 Indian Lakes formsatlon, Lava, porous.------Need Aurihiarg Air CorrelatIon uncertain: ------8 37 ---- 6 821 SWV( seec.f3, T. IS N, Rf. J9 E. U.S. 2 198 Sand.------Lava, very h ard-...... well for Shailef) ------Stwion. Altitudt. shoul 3,925 feet. Driller's leg of test 250 Seboo formation, lower member: v.11we 2d, i eri 1 944. Gumbo and sand -8------4 - - - 5 42 wnerate ; U.o . D pt. ~ N ry. Well eomnpilte d F eb ru Clay------NW). seec.36, T. 19N., R. t? B., O R.&sd3995145 feed. 1904 I 38 Wyersaba formation: tlealborehol, No. 46 in Nerman St4bter(wriltc eoennsair- Fallon formatlon: MApe sled Sand, hard ------8.2 12 54 wooter . . . . if It Sand.------lien, 1904) repot, walr bepd11 faed belo .sulfac in 1904. Sand-...... Shale, soft, gra-1 ------0 348 4 a8 Cay.------f Seboo, forznatlon: Sand, fine------20 368 Wyemnalb formation: . 1011- 0 47 Gravel. sandy------7 63 Clay, gray-88...... S teamse-1------3 381 course------2 2 Sand, Pea gravel, sandy...... 6 70 Sand, II Wyeinaha formaktlon: Swim, bard, sandy------16 397 12 82 Sand ------I1 I 101 148 Sand, black.------Clay, black-...... Sand, bard ------34 431 4 88 Bu~tosm-... ------I 4 Clay ...... I Correlation uncertain. Sand, fine…------10 441 7 93 "~Alkal bardpan -...... --...... 1:4. 5 Sand and g srael------Clay, gray -- 78------218 Sand bu ------4 445 I 94 Sand ------.- -2IS'? I soft, black ------3 270 Clay ...... 10 Clay, Crevice------1 446 Sand and gravel ....------6 Itoo Sand, Commr------3 clay, gray------7 342 fine ------45 . . . .I ------2 12 II Sand, Sand sod clay, lsterbedded------5 108 Gravel ...... Clay, gray, and fine sand..- ...... 14 288 Sand, hard -1------0 463 Well 1s 21L ...... S 2.. 408 W.11 heK1aL Clay, black-... Shale, rotten (lmelling?), black; turns Clay, greentlabegray-...... 142 550 * ra on e. -.------10 473 Rt. f8 5.; C aree Rirerjoo' plai SE)4SW)( arc. 30, T. 19 N.. Rf. 99 S. Careen Riser flend SE)4NEY4 Wrc33, T. 19 N., ...... s 0 A ,, on -[- .. - - waler well; driller, Ge0org Clay, gray-geen-... p lai , allilad e 0 6 0sf 5,9 0 f ee . Di le'de f a e el r l allifsde 3.05t±8 feet. Driller', tog of iI LAKE LAXHONTAN:GEOLOGY, CARIBONDESERT, REV. Tasta 11-L017e Of boelie-.Contun.us STRATIOGtAPrEC SEC17IONS, SOIL-FR OFiLE SECTIOSO~,AND WEL.L LOGS 151 TasLe it-Loge Of se0l1s-4nnthlnne W12 kawSIL-alltasod V.11 lee SL--Caata.d Time 12-Loge of weeita-Contlnued TAut 12,-Zega of eeelle-Contlnued 1 5 .4 Corelstlnn901Uncertala-Conitineted ' bkk bse Correltion uneren-otlud h-ln DOM~ Westl.W sIL,-cnttased Sand, A--C. corelaithionanoertale--Contilntted nlrkac, (lege N3M8R3.ee. IS, 7. 17 N., 16. 58 B. Former hod of Caren Sand, s-wrybr;et~ se n hc V- L~obe;atiilde, 8,950 feel. Drtl*lortiqof weoe sol ellW avtaer, Shale-....------0 *1,114 Shahe, herd, gas, showing------1 1.781 bard "1blshe --- 488- Sand, h ------r------11,1i27 GeorgieDallen; drifler, GeorpteNerea. Sand, fine---2' 00 Shale, sandy - 7 1,3 Sand, ebaly; remvice,lost nlrculatten -- 13 1, 794 Sbsle, sendy ay------12 1 Shale------4 1,798 Felioneformtin:lotnfes Seed, coerse --- .....----- 21 1, 155 4 Send, herd, somteaba ------17 528 Shale, herd, sandy -1------1,709 Toyan------8 8 Sbsle, gray ------2- Sad herd-...... ------1,158 Shale, lost circulatton------4 I, g03 Sand------2 10 -Shale, seedy ------42 1,200 Shale, soft, blue -5------Sehon formation: Shale, sandty, gas showing at 344 ft... 14 532 *Send,hbrd-.. 3 1.836 Sawe, pray; cretic ...... g & Shale, herd-1 1,204 Shale, sticky, gooey------24 1.880 Cly, yellow ------40 50 Seed, fioe------5 1.883 Wysemahe Shahe, t"nd stnake ...... tO 863 Shale, herd, sandy, slow drilling4 1,208 formatIon: Shale, sandy ...... & 570 Shale, grey------14 1.879 Sludge, black -20------s so Shale, herd ------2 1,219 Sand, berd------Shale, herdC...... 1 583 Sheleeandsatreoakeof hardg,;;i----- 9 1,219 2 1, 881 Clay, blue -6------88 ' Shale, gray------Sludge, black -23------Clay, tnugh, blue ...... 8 591 Shale, sandy ------3 1,122 35 1, 916 too Sand, haed -&------1,921 Clay, blue ------Sand - - - - - .. . . . - - 6- 597 Shale, candy, grey------28 1 1,258 Shale ------17 1,938 Sludge, black ------Shale, bu ------21 018 Shale------16 1,266 9 125 clay, tongh, blue ...... Bond aned habat-2------2 1.970 Clay, blue ------3 128 5 623 Litneetone shale, herd ------3 1,261. a Sand, hed-...... Shale, herd------4 1,974 Ssnd------2 130 14 7 Shnle, sandy ------9.9 1.276 Sand and eshale------21 1,995 Clay, yellow-..---- Clay, tough, blue ------6 643 Linesetone shale, hard -...... I 1, 277 ------4 134 Shele ------35 2,030 Sludge, black ------Clay ---- hr------no0 Shale, blue, wIth limestone streaks . .. 3 137 11 1,288 Saed, hard------5 Clay, blue ------... Sand . ...cr ...bad ...... 2 632 Sand------2 1.260 2, 035 31 158 shale ------Sludge, black ..------3 Shale, very herd- ...... 0. 7 632. 7 Llmeetone shale ------_-2 1,202 25 2,060 171 Seed, bard ------5 Clay, blue -1------3 184 clay and 'hale-15. a so Shale, blue------.. 10 1,308 2.066 Send and shale-...... Shale--_------20 2, 080 Sludge, black ------3 187 3 671 Shale, blue, end Itiny shale bedn-9-_.. 4 1,382 Shale, snedy-...... Shale, brown------14 2,090 Clay, blue-...... 8 193 ...... 13 684 Shale, blue ------4 1, 368 Shale, pay-...... 7 691 Sand, hard-8------2. 096 Sludge, black ..------0 Sand, erd - - 2 1.168 Shale, sandy-...... Sand end ehale------24 2, 120 Clay, yellow ------9 209 .. 12 703 Rock------1 1,369 Send, roam ------3 i Sand, running ------14 2,134 Sludge, black ------8 214 "~Quatnz------5 1,374 I Shale, sad-----...... 6 712 Shale ------19 2,153 Correlation Conglomerate (11,very herd------3 1.37? uncertain: Slhale, blus,-g_ ...... 721 Sand, bard------7 2. 160 Clay, blue ------Ceeglumerete (1), extra herd------4 1.381 6 220 Sand, conen, water at 725 Shale-...... 32 2, 102 Seed------ft -3---- 726 Conglomerate (?), extremely 2 222 herd .... 1 1, 382 Send, bard, and shale------20 2,212 Clay, blue------Send, herd-...... 3 "Limne," blue, wlth thin shale streaks; 18 240 Shale, hard-...... Quicksand ------16 2.228 Clay, yellow------_------3 very herd; gee ehowleg -- 3-----9 1, 441 10 230 Sand and chln ------30 2,258 Clay, blue Shahe, gray, end need ------9 748 Shale, sot, blue-...... 5 1,448 ------71 321 Sand, hardt-...... Lime, blue------2 2,260 Sand, water------5 Shnle, har------4 1, 430 49 270 Shale with sand atreaha------Shale, sticky, blue------12 2,272 Clay, blue -- 5 763 Shale, blue-...... 7 1,437 5------1 421 Shale-...... 9 772 Sand and shale------22 2,294 Limmestene,white ------Shale, hard------3 1,480 2 42 Shale, dtIcky, blue------44 2,328 Clay, blue Shale, sandy-.... ------6 778 Shale, blue-...... 1,402 ------17 440 shae------12 780 Sand-...... 7 1.470 Sand, hard.-1---~------3 2,341 Sand -I------441 Seed-...... Lime, white------6. 2,3471. Clay,blue ------. 9 Shale, herd-...... 4 1,474 7 448 Shale, herd-1 798 Seed, hard ------3. & 2,351 Shale end eanid, strong gee ehoeleg~ ---- a 1,482 Shale, soft-...... 6 egI Shale, sticky------43 2,304 -natt IN honby sh4Lsal batweasept-bh. 102 and Od"ef 11551. Shale-...... 4 1, 486 la.- Iee dat-nae,.ars - Mel Send. enoare, hard-...... 10 £14 Clay---- stiky------15 2,409 5.e5Ask laWteshe. ataf - petted Shale and $ned-...... is 1,104 Shale, noneandy------... 10 2,419 sod (-15sfeang~ nf S I 0,U11 et1sad- leeS 110,11111l; 70 Ibet Ihar Shale,0candy-...... 2 Shahe, gray-...... 14 1.919 asdetoe won 'on sa rs shear Is rec.nr4 n sWou01 rIt,end Shale------Shahe, sticky------12 2,431 b.elen jtIk,..ey Medandasia, withdenies ran jre WI "a day. 7 82 Rock--5 1,I I. S aa Shale, hard-...... 1 930 Shahe and send------73 2, 504 Shale and "ot1l"end------1.95 1.920 Sand ------Ban------, hrd ------7 .837 Shale-...... 28 1,5148 40 2, 544 Clay, sticky-...... 13 830 Shale, sticky------60 2,604 Send, hard-...... _ 4 1, 512 Sand, fine ------1 2, 620 Sand, fine-...... 10 86 Seed and shale ------13 1, i6S FOSSI1L-MOLLUSK LOCALITIES Shale, tough, pray -...... 42 90 Shale, herd ------16 2, 636 Seed, herd, and ahee------2 1,9987 Shale-...... Shale, tough, gray, with, sand atreaht.._ 20 922 Shale -- .. 4S 2, 684 Symbols in parentlleen, following the locality numn- 3, 1, 618 Sand, herd-...... ---- 14 2. 695 Shale, tough, pray -...... 030 bers, are fieldI-locality designations. Mollusk species, Sand, fine-...... 12 942 Shale, very hard------,2 Send, fine, sea showing - 11...... i 2,709 Sand and shale --- 36s 1,682 Send, herd, end clay-...... 17 959 Shale------26 2, 735 determined by J. E. P. Aforrison, U.S. Geological Sur- Sand, See; and shiale -...... 20 979 Rock ------1,687 i-ny, are listed1 in tableT. Shale 11 _11,678 Note-fl Y. tUe~.M erste VA.6Ossleati nue. cane she net tar Wf.Y Shale with, sand strahe -...... 25 1,004. vhs. It a" 2ees iht dee. IlP-reoIVd XE -lee Sw-Y al-nA) j`lne P-I. Shale, snedy-...... I19 1,013 Seed and shale------12 ;.cjt 69 juimp wafr bert clod takes b ele snetso-..550,bbbe ep Sun mtelde lbs (N2-1O.)I,lt1hold tefe, of Recue formarion. coealnl.ng ,sein and vs andr Sand, hard ------5 i 695 lislhtnPn- la sum0 ,ettino -- Wlandseretb snuall shells, Fleet fragment In eelishe sand of Wytrmaha Sha e rd-...... _ 34 1,057 ya.aris. teubabir d,,ia-d f-m fleet d"iaded cae 1.10le, an so ne-le Sand bu ...... & 1,002 Shale ------25 1,220 5 formtion. at boundady between onlde end c-elcreeees hoel- Seed ------11 1,731 few w b-eI ..lnlr~a as sael, Ce"Ltan eeeuod rWlnl sheik, Shale-...... 12 1, 074 wIS h,InItM -ee. u1dee,d InW vahemryd. sd hinece- SreI-n- w-~ onna of Churchill soll. East bsnk of west gull1y in Seed, hard --...... I.....,03 Saned,herd------2 1,7133 ,nbc.nd tla t, National Mason. bat the nety -lan-1ds'-rontIe -s eatn- Cherebl~l Valley 1,0500feel crest of Sebwn 2.Ioulntails SWV, Seed and shale; crevIce, lost cIrculatIon. 21 1,794 ,,dc eenIdad Inbhe d ft-~nc fhat cat, Totee ,eun. a. W. Plea-. eec. 15. T. 157N.,It. 50 E.; altitude 4,160±-20~feet. Shale------17 1, 097 w&dillS. tint. jwacy ecneseec. Inon soetld lthsl - It., Shah --...... 26 1,790 1-0 F-7. j(3_0-160 1l-1ll. Osetropede in grenule-eend,1 beneath In, Ch-hn ci-iConi Fe-l. betw ce lani. last ,nd Oetnb.nt"teWe thel celIlular tie ne1l .se.,dd XwOlee ant,n nr ipeen. Ics-s d~pj..ed ft),ee 50 tuia-cmrnled rehrit graeel. Lower esaheeb of 153 PGSSIL-11OtLtL7 (JRLCALr=8E CARSON DESERtT, 30EV. 152 LABE LAHONTAb.: 0110104IT, 7-32. (203I-93,11-1). Snails from take sand of Yount lake from sand Of third slake fOrmaitlOu; from surface of perlite sand overyn PF40. (23-12, R1-1). GastrOPOd and finteiak unit of Fattoo formation, probably transgressive phase. Southeast P-21. (NIJI-g9.11-2). Gastropods froml SW91 act. 12,T.190N, R1.2911E, embaymenktOf Carson LAke. sIll- Sebsoo . - unit of Patton formatlon. small inland iu nortetro 4,275feet. I yellow marly slit, at same site as F-IL. Lower mewber of,, edgeof white Throne MountARD4,altitude about attitude&3.908 eet. ik tude3.8feet. NS4A~ee,18,T.17N..B.2Dr_ Sbooseformalion, probably regressive phae ' lk SEc. c1,TT.1520.1R. 29 M - ~ :1. IF-41 (XI-M7. 51-). Gastropods from Send of third 7-83 (1-2-o ). M0.1se shelto from surfacs lake silt, 7._2. (202-8. 2107 ). Gastropods in silt anddesu vr P-S. (203-110,11-12). Gastropods from 25-foot, bed of alit. * unit of Patton Iomstioa. 511145111sec. II, T. 101N., young lake aod interlake unit Of Patton formatin., Near lower Wliag cellular tufa. I to 214feet below srae aest 20W142011 below 8 feet of cobblegravel. Transgressive phase. - . 31t.2911.;altitude"l.l~feet. southegso~f Cogn Lake, altitude 3,00feet. * sF-IS. Probably itregeaves phase, oe. ebro Sand member of Bebsoo forsmstioo. Northern White Throne T-42 (N20274, 1-2). Gastropoda -an pelecylpodalooo ae_ V T.7.120.. 11291E.I formation, Carsoo Mlountains. altitude 4.23Dfeet, MANE2011sec. P. T'. 18 Y.. *Sebloo * of third lake unit of Palion,formation. East side P-Kd (21-198 It-I). Clwamsd snail shells from lake send Gastropods from gravel of lower momw~ SIL T. 18 11. R.2011 Pr-IS. (207-106. P-I). Lake, altitude 3.920 feet. 1N0 411VNEne and sgutof young lake and toterlke unit of Patton forma- of Sehoo formuation. East front, Cocoon idonutalas" P40. (205-41 11-5). Gastropods from lower pail 'of 20 fool bee tion. 1 mite nortbwws of Billie"s Channel, west of still. mile sooth-southwest from northeast corner of Alton *deposit of meanysilt. Lower member of Sebsoformation. 0.65 P'-4& (N12-12 3It-2). Clam,1and soasishell% from One"pebble waler, Lakes; altitude. 3,87 feet. BE1342WIA owec. T,.21 feet. Of Patton3 probably tmaoogieeslrephase. Northwestern White Throne Springs; tuadcangle; altitude about 423 gravel (beach-terrace deposit) Of third lake unit Gastropods. In sand S in 6 feet below ~ side Canson 1,ake. altitude Sj20 feet. inks altitude 4.190feet. SE142W)4 sWI. 2'. 2E.F18 F-24. (N&-5,% It-Tb). forranton. East t P-Z& (203I-86 -1). 0,avotda soadpelecypods froml Mfountains, section 55. Lower member of Seboo R.112011. top of stratigiraphic 5E345SW'AneC. 29, T.17 N, . 0E. sand of young lake and intertake unit Of Patton formation, probably regressive phase. Northeast aide, In take sand of young (tUC-L). GOsiropods Io fioe pebble gravel, 0 feet below formation, P-45. (111-2W81111-1). Gast-repeds 14 mIles southwes~tof Later Btunch; attitude. 3.88 feet. 71-10. altitude 4,320feet; 0.2 mile northwest Patton formatioO, 1% miles sooth. boast guano layer. tower member of Sebso formoatioo. Cocoon Mfountains; lake and Sattsrtak mutt of SWIA see.23. T. 2120.,11.2911. summit, altitude 1,895 feet. teonord roek shelter arebseologle site, 11 miles due south fromo4.604-foot east of Canasbacsk Gun Club. Gaoteopodsfrom mundof upper mem- .PStlE. of letter from Lovelock. N~ev_0n nortbwest piedmool of West Hum- F-26. (N02-124.r-4). SW %SW % seet. 84T. 2D N2 mindInterlake unit of Failon formatiou, 2 m~leswest side, BaneFlats, alti- sandof young take and N0.,R. boldt itnoge. altitude about 4,175feet. ber of Sebooformation, Northeast F-4d. (N01-100.11-1). Snails In take Ilooch. altitude 8,880 feeL 201119111see 22. T. 21 sec. 4 (muorveyed), T. 18 N.,, Patton formation 14mile south of Carson tXS-91k11-3). Castropods to yellow msrlY silt, traus- tude 3,900 feet. N204 isteclake unit of F-1l. N0W%/sec. 17. T. 21 0., 11.51 IL. young greosire phase,lower member of Seboo formatIon. South- 11.8011. Sink, altitude 3.880feet. F-5T. 1GS2-3. Du.5,). Gastropods from lakte sand of from lobeasondof dal lake o~it linastrafrm surface lake sandof Young 2 miles smouth eastern White Throne Mountains, altitude 4,320 feet. F-29. (N30I-4.It-x5. Snails r-41. (N01-200,11-0). iske god interlake unit of Folos formation. ccc.24, T, 19 20.,Rt 29 E.; unit of Fallolt formation, I mile south se. 24, T. SE% see,28,A T. 1ISX. .112011. of Fallon formatios. SE114W'/ lake and interloke of Carson Sink, altitude 3,991feet, SWSWIA 3,9129feet. of Carson Sink, altitude 1,81 feet. 20W%%E11me. 20. F-22. (.V3-KS11-4). S0a1l0 in sandy gravel, 20 feet stratI- altitude 212 1.. .80 11.yuglaea T.21 20X..Rt. 3 E,. lake sand Of yuglk n graphically below cellular tufo-cemented cobble gravel. F-SW. (203-123,11-it). GostropodsfeomlocuotrinssandyslIt., P-fit. (N3-48.B-2). Clam from of first lake unit of Fallon Gastropodafrom lake sandof young South edge of Cerson Transgreooive pbase.lower member of Sehooformation. 3 to 714 feet beneath surface, r-48. ((18-11, 11-12) intetake unit of Fallon formation. exposure 2 miles soutbesot of Follont formattsa, 14mile south 11, T. 21 20. It White Throne Mountains, altitude 4290 feet. formation, Drsinsoe~caoal lake and toterlake unit of Sink, altitude 8,81 feet. N0W14SWs ace. Ndorthernt SEI4XEIA sec. 4, T. I8 N0., Reanch, altitude 3,880 feet. SWUSE111ofe, 24, 20WIAame20. T. 18N0., R. 2911. Fallon. altitude 3,94.5foet; of Later Snails from lake sAnd of young inks (NZ-dO,21011). Gastropods to seud, Interatitial In and It. 291E. T.21 N., IL 22E P-SO. (NI201-0 B-7). FLIS, shells from toke sand Snell and Clgamshells from incus. of Potion formatIon. I m1lesouth of Car- boulder grovel. 3.2 to 5.2 feet below surface. F-SI. (XI3-120. R1-1). Suall and Clam 7-49. (201I-2091, 1-5) and Intertake unit oceelylog formatIon, 'A mite west of of young lake and lotertake culit of 2011120E1see. 20 .7.21 1., phase,lower member of Sebso formation. of Lest lake unit of Fallon Irine sandy clay asmSink, attitude 3.81.0feet. Trsnssrnaave 8 miles herth of Patlos; altitude 3,94 forat-ion;, exposed ia canal bank. 1 foot below Dog pit, southside of bill west of SehooMountain, altitude Cation Ritver and Patton N, R.,2911M miles southeast of Caursobsek Gun Club, altI. R-O.3Co R at) Sail from surface of marshy meadow, 4.20 feet. XWMZ%'W1see. 22,T. 1SN~, t. SOIL, feet; 2013451114see, SI T. 20 surface, 1% Larootrise clayey se.1.T 020N.1131 IL 14 mile from north end, near iloD). Gostropods to cellular tufa at same P-It. (201-24811,11-1). Gastropods from tude 3.890feet. BEIA2W1 floor of Churchill Narrows. F-14. (202-84. Probably (sasoctfted with nodules Of muInbto above F-I3. Trouogrroolve phase,lower silt and silty sand, 4% to O feet below aurfsce. 7-80. (202-95 R11-1. Snalt$ ,Wrsbulks. Nev. t1Present-dIayforoms) site: about f feet Borehole inks sad lnteriAke unit frommuinbto leboo formation. first or second lake cunt of Fallon formation. titboid tuft) in lake sand of Young F-El. (0-51234). Present-day snails memberof Little Cottonwood take, to Pttoun. NE1%8E'A ne'. feet strati. ou crest of low ridge, northwest side of Stiliwater Lakes, of Patton formation, 1 mite east Of of drolusge canal. 1% miles tset F-Il, (*242-7, R1-I). Gastropods. in sand 6 31 r1. 20WTA.we, 2Z . 2.21). It. 31 E1. altitude 1,88 feet. 81114811%me. 10, T. 20 20, R1. - sf soso graphically belowand 01 sme site as F-I, Transgressivee altitude 8.880 feet; 32.ZT. 19N.. It. 29 11. Snails end clams in disirlbsisry~chsu- P-SI. (202-91.11-1). nasil and clom shells from inks sand P-C. (R.,g R~eu). presot~dzy mounsselicaa ofroRtlshoreo phase. lower member of Seboo,formtilon, P-SS (0-92. 11-2). t and inks sand (at anrfsc) of secondlake unit of young lake and Interlake unit of Fatlon fsematloa. 2 Rtegulating fleservoir. iA milesestoBtlafle f 202-1,1-Ib). Gauetopod is S-footgrasuleasodbed, net sand R-L~ine 11 F-Id. 8 miles northeast of Failon. altitude * miles south of six Cottonwood Lote, altitude 8,95 feet. lull. NlVA5Oc,22T.101N..R20 by 8 feet of pebblegrovel at top of bay bar, same of Fallou formatIon, overslai SW cor, we 2, T. 19 N.. P1.2 NW14NW34 see,217.T.202,.1. I 0EF- site on F-IS. Rlegreooive phase,lower member of Sebao S,920 to SOlofeet; and clams from fine gravel Saddle between Seboo ilouslain and Eaglce P44. (20-1128, R-3-b). Snails formaotion. unit of Falbonformation. Wild. Moose,altitude 4,21 feet. N011(aet. 21. T. 1811.,It. go S. (bar deposit), secondlake cat wcarp seast of Carson Lake. sltitude 8,127 feet. P-I?. (02-91O,C-2). Gastropods. In pebbly saud of lowe SE14SWIA mec.29.T. 17 N-It. 30E. memberof Srhoo formotion (probably regreanire phase). P.55. (22-11:5, It-xl). Gastropods and peletypoda from saud Same aliens locality F-I. except about 20 feet stratigrapbls- of second lake unit of Fatton formation. West aide Turo- *allyhigherallitude 4,210feet. Flat.-ItIttude 3.920feet; 20E142W1 Per, 12,T. 18N., Glastropods In pebbly send. ltegreaale pab, P-IS, (N7-40, 11-2). B1.3so11 phase of tower member of Seboo formation. overlying eel. F-SS. (N12-174.R1-1). Snails In send of secondlake unit of gravel of this member. Our-quarter tutor tufa-cemented Fallon formation. 1 mile soutb of U.S. Highway 50ost Grimes summit, ounringMlountains 1 mile southeast from 4.298-foot altitude 3.927 feet; 20E13/2E3 see. 31, T. I8 N.. 4,200±t20 Point. see,22 (Unaerleyedl. T. I7 N0..R0. SD Z1. alttitude It.5011. feet. 7437. (N02-137.P-i). Snails aindclama, from send of second fine graTel. Its, P-IS. (N2.-81.R1-x4). Gastropods Iro sandy lake unit of Fallou formation. 400 feet up 1,Drato Canal greoIre phase of lower nmemberof Seboo formation, from junction with Diagonal Drain; altitude 1,122bfeet. Bleach trerseaeembankmeset on west side of SebsooMona. 20E13420111seclI7.T,182,,l.30E. Isis. altitude 43222feet. N0WO2W(4 sec. 15. T. I8 N0, 748. (23-44,. B-I). Snails from sand of third inks unull altitude R1.301E. of Fallon formstlon, I mile west of Wolf Dam, F-20. (N02-118,194). Gastropods In sand, flegreastee phase L"i5feet. NE011V1Aft145c,20.T.2OL,R.29& third inks unit of tower memberof Sehooformotlsa. Tiny spit at north- F-SO. (00-12. 11-4). Smails from sand of 12. 7. 1920.. IL. 29 11_at- east edgeof let-ta.Souutin), altltde 4.090fee. SEIASE14 of Nation formation. 5E1%6ee. feet. amc 21,T. 1820 .11.0 E. titude 3.910