A STUDY OF THE LAKE LAHONTAN
SEDIMENTS IN THE WINITEUUCCA AREA, NEVADA
A thesis
submitted to the faculty of the
University of Nevada in partial fulfillment
of the requirements for the degree of
Master of Science
Keros Cartwright
Reno, Nevada
January 30, 1961 Director of Thesis
Approved
Chairman of graduate committee
i i TABLE OF CONTE:ITS
PAGE
ABSTRACT...... vi
INTRODUCTION...... 1
ACKNOWLEDGEMENTS...... 3
-PHYSIOGRAPHY...... if
REGIONAL GEOLOGY...... 6
METHODS OF INVESTIGATIONS .HID RESULTS...... 10
Field Procedures...... 10 11 Structure...... + 20 STRATIGRAPHY...... 20 Ea.rlv Lahontan......
Medial Gravels...... 23
Upper Lahontan 28
Post Lahontan. 3?
Paleontology.. 37
SEDIMENTARY PETROGRAPHY...... 39
LATE QUATERNARY GEOLOGIC IISTORY...... ^3
ECONOMIC GEOLOGY...... *+7
SUMMARY AND CONCLUSIONS...... 1+8
BIBLIOGRAPHY...... 1+9
APPENDIX 52 ILLUSTRATIONS
p a g e
Figure 1. Index map...... 2
2. Difference between lake and fan
sediments, southern Paradise
Valley...... 15
3. Clear Creek flood, ala in...... 17
*+. Formation of bluff on the east
side of Clear Creek flood nlair.. 19
5. Sonoma Ranch well...... 22
6. Basal gravel on Sonoma and Thomas
Creek fans...... 2b
7. Size analyses of the basal gravel
on Sonoma and Thomas Creek fans.. 26
8. Change of facies of Medial travels 27
9. Upper Lahontan. section...... 29
10. Section of the mouth of the
Little Humboldt River...... 31
11. Illustrating the change in sedi-
ments between Grass and Paradise
Vallejos...... 32
12. Western Pacific gravel pit...... 3^ \ 13. Humboldt county gravel pit...... 36
1b-. Generalized section of Grass
Valley...... • ••• 38
15. Process of deposition.•• ...... *+1
i v ILLUSTRATIONS CcontT"
PAGE
Figure 16. Process of deposition modi-
fied...... ^2
17. Possible hyoosonetric relation-
ships of the late Quaternary
sediments...... ^5
18. Levels of Lake Lahontan...... *+6
PLATES
PAGE
Plate 1. Composite Geologic Map...... Jacket
2. Rose Creek Quadrangle, Nevada. Jacket
3 . Winnemueca Quadrangle, Nevada* Jacket
h. Bliss Quadrangle, Nevada...... Jacket
5. Osaood Mountains Quandrangle,
Nevada...... Jacket
6. Paradise Valley uadrangle,
Nevada...... Jacket
v ABSTRACT
The last bed to be deposited by Lake Lahontan in the Winnemucca area was a five feet thick silty clay, which grades into a fine sand near the shore of the lake. This sand, when traced around the basin, defined the maximum extent of the last deep-lake stage.
Lake Lahontan occuoied the valleys around Winnemucca at least twice. A basal conglomerate is associated with the rise of the second deep- lake stave. Poorly preserved wave cut notches are found at M +00 feet and ^360 feet above sea level which are associated with the first and second major rise of the lake resnectively. Gravel bars are found associated with the second deen-lake stage of Lake Lahontan.
The petrogranhy of the lake and ian sediments was connared, and a possible means for distin - uishing between the two types of sediments is suggested•
v i 1
INTRODUCTION
In the spring of 1959 a program designated the Humboldt River Research project was author- ized hy the legislature of the state of Nevada
(Cha^. 97, Stats., 1959)* One phase of the pro- ject provided for geologic mapping of sediments involved in the hydrology of the basin.
The first nortion of the project covers the Humboldt River Valley and adjacent drain- age areas between the Rose Creek and Comus Creek gauging stations. See location map, figure 1.
This paper deals with the sediments of
Pleistocene Lake Lahontan. Special emphasis is given to the near-shore sediments of the lake, their extent and relationship to possible recent tectonic activity in the area.
The work was begun in June 19^9 and was carried through the 1959 and 196c field sessions.
There are four previous reports on tne geology of the basin area (Robinsor, Loeltz and Ihoonix,
19^-8, and 19*+9? Onuschak, 1960; and Wilson, 1960).
Bedrock Geology was done by Ferguson, Puller, and
Roberts (1951), and R. Willden (in preparation).
The co-ordinates system used in locating
points is illustrated in figure 5* a> V/nnem ucco r * E.I K o o c Reno I a: o .NEVADA i
' i £ \ ; o *■«» V«gos • fj O Q: />
0 c o ) •o O e (/} 3/ -i *D O w O winnemucfco Q_ Mounta in */ Urar. i-Wi/ine m ucca \ v
/
FIGURE I 3
ACKNOWLEDGEMENTS
The writer expresses his appreciation to the
following peonle who aided in the field work and made many heloful, critical suggestions in the
field and in the nrenaration of this renort:
Dr, 3. R, Larson, chairman of the geology depart-
ment of the Ma.ckay School of Mines, who directed
the Wield work and the preparation of the oaner;
Professor J. I, Gimlett who made many valuable
suggestions in the field and in the editing of
this pa^er; Mr* J. N, Swinderman of the University
of Nevada and Messersd. W. Hawley, and W, 3.
Wilson, of the University of Illinois who aided
in the collection of some of the data in the
field. If
PHYSIOGRAPHY
Tho area studied includes parts of Paradise and Grass Valleys. The former lies east of
Winnemucca, Nevada and mostly north of the
Humboldt River; the latter lies west of Winn-
emucca and mostly south of the Humboldt River.
The valleys are almost entirely bounded by
five mountain ranges. The highest range in the
area is the Santa Rosa Range (maximum altitude
975k- feet above sea level) which borders the
west side of Paradise Valley. This range extends
from. Winnemucca fountain, just north of the town
of Winnemucca, to the Nevada-Oregon boundary.
The east side of Paradise Valley is bounded by the
Hot Spring Mountains and the Osgood Mountains?
the Sonoma Range is the southern boundary of the
valley.
The Sonoma Range which bounds the east side
of Grass Valley is the second highest range in
'area (maximum altitude 9^21 feet above sea level).
The East Range bounds the west side of Grass /alley,
and Winnemucca. Mountain and the Lrum • (ills form
the northern boundary of the valley.
All the mountain ranges are block-faulted
ranges typical of the Basin and Range Province,
and are bounded by relatively s h a m fronts, except for the East Range. The ranges have a very thin soil mantle and vegetation is scarce. They are drained by small nerennial and intermittent streams. The uplands have rounded to sharp peaks and portions of the Santa Rosa and Sonoma Ranges have been modified in their higher reaches by
Pleistocene glaciation (Robinson, et al, 19^8).
Remnants of several old erosion surfaces are nresent at comnarable elevations in all the ranges (Ferguson, et al, 19^1)*
The valleys are north-south trending troughs tributary to the Humboldt River. Paradise Valley is drained by the Little Humboldt River which is dry in most of its lower reaches. Grass Valley is drained by Clear Creek, which is dry for its entire length from the mouth of Clear Creek
Canyon to the Humboldt River. Goth si-reams, however, have incised charnels showing much great- er flow of water in the past.
No estimate of the denth of fill in Paradise
Valiev has been made5 however, its deepest oortion is probably considerably north of tue Humboldt
River, the valley being rather shallow here.
Valiev fill in Grass Valley was estimated, to be
over ^600 feet thick one mile south of tie
Humboldt-Pershing county line (V/ilson, I960). 6
REGIONAL GEOLOGY
The geology of the 30 minute Winnemucca
Quadrangle has been mapped by Ferguson, Muller, and Roberts (1991) and Humboldt county by R.
Willden (in pernanation)• Internretations have been drawn largely from their reports. Since the detailed geology of the ranges border! g the area is not within the scope of this report, only a general summary is presented.
The ranges consist of a great thickness of rocks of Triassie and Paleozoic age which are intruded by late Jurassic ((Cretaceous ?))plutonic rocks and overlain by Tertiary and Quaternary sedimentary and volcanic rocks. In general, the older Paleozoic and Triassie rocks form the ranges, while the younger rocks flank the ranges and are preserved mostly in the valleys.
The pre-plutonic rocks nave been strongly deformed by two periods of folding and by a series of large thrust faults which bring together rocks of the same age but different facies.
Eroded remnants of thick flows of rnyolitic
lavas are exposed in 'Hater Canyon and south of
H a r ony Canyon, Dikes of rhyolite porihyry cut
Paleozoic sediments (some dikes follow thrust- 7
pebble dikes consisting mainly of quartzite in a
matrix of rhyoliteQjerguson, et al, 1951)^)
Tertiary sedimentary rocks are exnosed. on
the pediment bordering the north end of the
Sonoma Range. They consist principally of poorly
consolidated conglomerates and sandstones and are
overlain by the rhyolitic volcanic flows. North
of the Krum hills is the Pansy Lee Conglomerate,
a moderately consolidated conglomerate, which is
either Tertiary or Cretaceous in age)(R. Willden,
19 o8). To the northwest near the confluence of
the Humboldt River and the Little Humboldt River,
and in the Krum Hills, tuffaceous sediments of
the younger Plxocence)(?) Humboldt (?) ^formation
^(l/ilmarth, 1938; Robinson et al, 19^9)) dip about
30° southeast ((confluence of the two rivers)) and
20° to 30° south (Krum Hills): they are overlain
by less steeply dipping or flat lying basalt flows,
This evidence correlated with well data suggests
that most of the valley floors may he underlain
by Tertiary sediments. These include, fairly
thick sections of the Humboldt ()(?D formation.
Tertiary and/or yua■ternary basalt flows " re
quite extensive on the -"lanks of the mountains
bordering Paradise Valley. They dip 10° to 15°
northeast on the west side of the valley. The
same flows^Otobinson et al, 19^9, P* 26)) are 8
flat-lying or west dipping on the east side of trie valley. (JBasalt flows form louderbacks east of Winnemucca at the confluence of the Humboldt
River and Little Humboldt River (near the Kern
Ranch) and opposite Rose Creek just north of the
Hillyer Ranch/) A small basalt cap is exposed directly east of the city dump two miles south of
the town of Winnemucca. Die age of these basalts has not yet beer determined, but the relation-
shins of some to older Tertiary sediments
(Humboldt ?v\md younger Lake Lahontan sediments
leaves little doubt that the relative age of at
least some of them is nost-Humboldt and pre-
Lahontan*
The following sequence of late Tertiary and
early Quaternary geologic events has been suggest-
ed by Robinson, Loeltz, and Phoenix 09^9) and
modified by the writer: 1) Miocene volcanism in the area resulting
in the wide spread distribution of riy-
olite and other flow rocks and partly
contemeeraneous sediments, capping
earlier Tertiary and pre-Tertiary rocks.
2) Tilting of the volcanic and sedimentary
rocks by Basin and. Range faulting follow-
ed by the accumulation of the Humboldt
(?) formation (Miocene—Pliocene), which may reach thicknesses of 200 feet or
more.
3) More tilting by Basin and Range faulting
accompanied by Tertiary and/or Quaternary
basalt flows (Swinderman, J. N., personal
communication).
*0 Desiccation of Pre-Lahontan lakes and the
development of the Humboldt River system.
Deposition of alluvial fans and other
types of arid and semi-arid sediments.
*>) First advance of Lake Lahontan. 10
METHODS OF INVESTIGATION AND RESULTS
Field Procedures
The. Lahontan sediments are not exposed in the
Winnemucca area except in the bluffs bordering the
flood plain of the Humboldt River. Even here a
shovel is usually needed to clean a section for
examination and sampling.
The floor of the valleys are composed of
Laho' tan sediments. To Investigate and sarmle
these sediments the soil auger, pits, and high-
speed cower auger (used in drilling observation
wells) were used, as well as well data on file with
the State Engineer and from private wells drilled
while the field investigation was in process.
Though the second method is the best In re-
gard to accurate description of the sediments and
for obtaining samoles, the i'irst method was used
primuiUy because of its speed* With the soil
auger a hole five feet deep nay be dug in fifteen
to thirty minutes, and extensions may be added to
the auger if greater depth is desired, and samples
obtained In this manner are rarely contaminated.
Disadvantages of the soil auger are tnree fold.
1) The samnlo is a disturbed sample and may
only bo taken from the lower part of the
auuer, thus limit'ng the choice of where 11
the sample is taken,
2) Pebbles, even small ones if well lodged,
will stop the downward progress of the
hole,
3) It is difficult to bring unconsolidated
sands up the hole, this may also stop the
downward progress of the hole.
Maps, which show the extent of the Lahontan
sediments in the basin, were based on data gather-
ed by these various means, The rocks in contact with the Lahontan sediments are shown on the map and an age relative to t ie exposed Lahontan sedi- ments was assigned. However, little effort was made to show the relationships between the non-
Lahontar rocks.
Two facies of the uooer Lahontan sediments
wore manned: a clay facies and a. sand-silt facies.
The clay represents quiet water deposition, and
is generally found in what must have been the
deeper parts of the lake. The sand—silt facies,
which, i eludes a number of long snore bars, re-
presents a near—shore smallow water de 'ositio •
This change of facies usually occurs at an elevat-
ion of V 320 feet above sea level which is !+0 feet
below the 'aximum shore-line of the lake.
The contact drawn on the map between these
two facies of the Lahontan sediments is wholly
! 12
subjective. The contact is always gradatio al, and usually grades over a sore a mild or'more in width? only rarely is the change rapid, such as at the : out i of the Little Humboldt River (west
side of the river just north of the basalt flow)•
In so is areas the contact was drawn win-re clay was presort in sufficient quantity to make the
sad’no t bl.ocky when broker . This is about 10b
clay: the clay content of the doe-'-lake clays is
about 1 Hi to 2H1. The tests of ostracods are
rarely found broke- in the dee -lake clays and
are rarely found whole ir the near-shore facies;
therefore, in some areas, the condition of the
ostracod tests was another criterion of deposit-
ions 1 environment.
The contact of the near-shore facies with
those of the fr.-s often presented problems. '-There
the contact is with coarse alluvial fan material,
1]11 • ,vs g 1 s no difficulty: however, where the lake
criteria
lato Lahontan fans is the development of
a hard-pan as rpart of the soil profile,; The hardpan may be formed by the accum-
ulation of clay or CaCO^, A hardpan
was never found in the Lahontan sediments,
2) The fine fan material co: :o :ly co tains
scattered pebbles; this is very rare in
the lake sediments,
3 ) The opposite may also occur where the
lake sediments are coarser than the fan
material with which they are in contact.
The contrast is one of a pebbly silt of
the fa: in contact with sand and gravel
of the lake, Tie sand and gravel of the
lake is probably the fan material which
has been reworked by the waves and the
fines washed out,
1+) 'Then the sedime ts in contact with the
lake sediments are completely unconsol -
dated, as is the case of younger sediments,
the.difference of consolidation can be a
distinguishing factor. Although tie
writer would not consider tie sediments of
the n e a r — shore f cies oi tie lake consoli-
dated, these sediments have usually acquir-
ed some degree of cohesion because of the
presence of small amounts of GaCO^ (see
Onusciak, I960, for a discussion of the
emplacement of CaC03). Minor amounts of clay present in the silt also add to their
creator cohesion.
o) roomorphic features showed the location
of several crave! bars ?n Brass Valley
south of the lumboldt River. Vue •.travel
bars arvpeT.r as small elongated mounds,
which, when chocked, proved to be well-
sorted, cross-bedded sands and gravels
of Ir k origin.
6) The lake material is usually better sorted
than near-by fan material. This is not
observable in the field under lost
circumstances; however, laboratory dr ta
were helpful in pi cing. the contact- in
an area at the south end of Paradise
Valley, Bliss uadrangle (see figure 2).
Structure
There is no evidence Cor any post-Lahontan warping, in. the roa. Tie b sic '’or this conclus-
ion ’ 3 pi "lost entirely ly losomatic. i re elevation
take from the b- se of the highest wave cut notch
(1+360 feet above sea level obtained by the engineers
level) on Rose Creek fan in the western most part
of the area corresponds very well to the elevat-
ion at the base of another wavo cut notch (L+3o?
feet above sea level obtained in the same .a r.er. 100
bl O tr ui Q.
FIGURE 2 Diference between lake and fan sediments, southern
Paradise Valley (T36 N/R39E, S6 and 7) between Button oint and tie town of Golconda in t ie eastern 'lost rant of the area. There is no mood north-south control of this nature: however, there seons to be no warning along the wave cut notch which extends for four miles alo' p; the east flank of the Bast largo.
Til ere has been some nost-Lahontan faultin' .
A fault along the west front of the So oma Range has moved in historic tines (Jones, 1015") and left a sc a rol of, near the head of the fans far above the
shore-line. ' second fault on the southern flank
of Winnemucca fountain is evidenced by a snail
scarp in the alluvium, which crosses the head of a small post-Lahontan fan. A third fault flank-
ing the north front of the East Range has a small,
and usually indistinct, scarp in alluvium; this
fault does not seem to have much affect on the
sediments. There is evidence that tie fault whnch
borders the west front of the Bast Range extends
north to the river ( ilson, 1960;. - o evidence of
post—Labortar movement along this zone nas been
found. In Grass Valley at the southern edge of the
hose Creek 'hiadran'le there is a nrominert bluff
on the east side of Clear Creek wit i no counterpart
on the west side (see figure 3). 71113 bluff 1)ordGrs
the small flood plain of Clear Crook and its --- -- / ------/ / ------I -I --- (>J (>J ------b;l+:::----- _L // --- zZ / 10 I I / / / I ------/ / ,,..------I / I I .- I ~\ _.:u / _J _\J-- -- (JJ -- "" ·------./ ------N -- m . "--. 'Z. --· / ,,.... ------r------N \ /' ___,\ ,...... ------Ul ------con1our line '--- _....-, FIGURE 3 ------ect;Je of flood ploin Cleo r Creek flood plain - bluff IS h e I Q hf Of b I U f f - I ------—
18
tributaries which enter from the east, until the
••oint where the stream entered Lake Lahontar.
From this ooint northward the bluff follows the lake shore, decreasin'! in size, in to the roint where the distributaries of Sonoma Creek have erased the evidence". The following explanation is given:
There is a known active normal fault border-
ing the oast side of the valley with the
east side constituting the un-throw: bloc]-.
This .fault'ng would change the base level of
erosion in the range and increase the quantity
of sediments coining into the valley from the
east. The increased quantity of easily
eroded material on the east side would cause
a deem notch to form on the east side in the
soft sediments, while no such notch would
fora in the loss easily eroded material on
the west side. A slight tilting of tie
valley (east side down) similar to uv t f ound
to have occurred in Dixie Valley in tne ear.i—
quake of 19^ (Whitten, 1957), (seo figure
h) would add to this effect.. 1. Bluff berino to for. slowly whilethe 1 V e c t o rsh s o wa c t u. a l . o v e r r e n t . 1 fan builds up. r sn sra ctbufi formed.is bluff cut stream resent uil-j uo of fan becomes v ore ra;id after *"t>aultinr andbluff C3formation isaccelerated. PIii JE 4 'JhE STRATIGRAPHY
The stratigraphic sequence of Lahontan beds is different in Grass Valley and Paradise Valley*
Tie narrows between Winnemucca Mountain and the
Sonoma Range w lere the town of Winnemucca is located seperates the tx^o areas of deposition.
Russell(188?) states that "the sedimentary deposits of Lake Lahontan exhibit three definite divisions, viz:
TJnper Lacustral clays
Medial gravels
Lower lacustral clays".
Tie writer will follow this outline in the discussion of the Lahontan stratigraphy.
Early Lahontan
Pew data are available on the Lower Lahontan
sediments in this area* They are not exposed,
and well data are the only evidence? due to this
lack, the early Lahontan sediments are not d...scus.,—
ed separately by valley. Tie shallow test drilling
of the IT. S. Geological Survey did not penetrate
the lower lacustral clays Russell mentioned. How-
ever, the drill did encounter what is believed to
bo the medial gravels. Tne only direct evidence of the lower clay
comes from the Sonoma Ranch well (T3lMI, R37'j» sec. mmmmm i— Hi 21
3, 0) in Grass Valley drilled during the I960 field
season and los 'od by J. Hawley and the writer
(figure 9). Ostracod bearing clays, encountered
between 100 and 10? feet, are believed to be the
Lower Lahontan lacustral clays. Evidence from
drillers logs on file with the State Engineer seems
to substa tlate this although most of the logs are
very ooor. Above and below this lower clay are
subaerial alluvial deoos'ts.
Along the north flank of the Sonoma Range is
a terrace at the VfOO foot level, which the writer
believes to be wave cut? however, this terrace has
no denos'ts of lake origin which can be directly
associated-with it. The writer inter ■rets this
terr-ce as older than the lower terrace at the ^360
foot level associated with the last rise of Lake
Laho tan. This upoer terrace may correspond to
•the M+on foot elevation of the highest Lahontan
shore-line in the ^/ra^id Lake area (Broecker and
Orr, 19 08). Whether the M+00 foot terrace and the lower
Lahontan clay mentioned above belong to t le sene
deeo stage of Lake Lahontan is not known. The
writer feels that they are for there is evidence
of only two major stands of Lake Laiontan in tnis
area} since the terrace does not belong with the
second, it -nay belong to the first dees stage. surface material, mostly silt
upper *.at ontan lacustriai clays, silty, block.}’ when broiten, some sand and gravel lenses, ostracods
clay, slightly sandy, scattered pebbles
clean sandy gravel, basal gravel
sandy pebbly clay gravel-sand-silt, clayey lens near top
sandy clay, lime hard pan (lower Lahontan?) lower i.ationtan eilty clay, dense and blocky, ostracods in bottom five feet sandy, silty clay, hard pan, root tubes pebbly clay, sandy and silty
clean sand and fine gravel, finer at base
sandy clay, hard pan between 14?' and 1 4 1 '
sand scale 0 >j' hard pan Lxuj__ i--- -i---- '
FIGURE 5 shaded area = Jdb
Somoma uanch well 3 A (•r>4V»57Sf Ddb>
b a
C 1VM _ c 1 ' In addition investigators i- other areas find orly two major deed stages of the lake; the first of which is the deener stare (Russell,1385; R.
'iorrison, personal co munication).
Medial travels
Resting upon the lower Lahontan clays are ali.uvial deposits, probably subaerial in origin; lying unon those denosits is a gravel unit. The maximum thickness of the gravel denosits is about
1 MO feet which occurred in a well about two miles west of the town of Minnemucca. High on Sonoma and Thomas Creek fans, exposed in nits, (figure 6), and in the Sonoma Ranch woll (figure b"1, thicknesses of loss than ton feet are encountered.
The total thickness of denosits between the upper and lower Lahontan lacustral sedime ts is
R6 feot in the Sonoma Ranch well. This is probably the time equivalent of the thick gravels and sub- aerial denosits near the river and the medial gravels of Russell(188b) in the Rye Patch and Mill
City areas. The man shows that if the water of the lake stood at a: elevation of b27 b feet above sea level the lake would have covered only the lowest
.portion of the valley from the town of Winnemucca westward; a further drop in the lake level would have removed the lake Ton the area entirely. s u t f a ce__e le vat ion___434 0* silt
0 0 0 0 0 9 o O O O O a o O & O OO&OOOOOOCJIO O O ■f o c* o o c/ o o o o a o o a o o 0 & /O& 0 O 0 (90000 O O 0 0(09 a o o a & <7 0OOOOO0OOOOOOCJO oooooooo o- O & o o ° ° pebbly silt Alluvium ■ o'. ».'.«• o ■ ° ■-•'•<> • >'■0.0. surface elevation 4320* Eo Iian Sand 2 deep lake clay O » 0 0 • o o O o a <3 0000 000 90 0 0 0 *0 0 0000 0 0 0 0 * 0 0 0 0 * 0 0 0 0 •> Lahonton 3'< 000*000* 000*0 . OOOOOo <70000000 oooooo'uctoooo* basal grove i oo&oooooo & o o * * beds 7 O y 0 O_0 O OoOgO 00 QOOoOoO pebbly silt 8 < (with gravel lens) O’ O Of /All u v i u m pebbly silt Thomas Fon (T35 N/R37E.S I3C bb) FIGURE 6 Basal Gravel on Sonoma and Thomas Creek Fons 2? Thus while the lake stood at low elevations sub- aerial beds wore demos 'tod higher ir. the basin. The -renter thickness of the gravels near the Humboldt River could bo the result of a larger quantity material made available by the "ancestral Humboldt". Size analyses were made of the basal grovels from both Sonoma and Thomas Crook fans (see figure 7'. These analyses show a well sorted gravel. I-Io analyses were made of gravels from near the river, because satisfactory samples were unob- tainable. It is believed by the writer that this basal gravel is the same as the gravel found near the river because coarser sediments were encountered directly below the Honor Lahontan in all doep observation wells, and represents the rise of the lake. Some of the gravel near the river may have boon river laid*, however, the bulk is probably lacustrine. Evidence of a lake origin for these grave1.s is the facies change from gravel to sand which occurs in the Rose Creek aroa (soe figure u;, and the blanket-1 'ke nature of the gravel. There is not enough evidence in Paradise Valley to say whether the basal gravel does or does not exist there. There is a gravel in tne Hum- boldt River Valley which may bo the basal gravel, i ii— h 'h h 'iMimm*1"H gi— w— iiiiw i " f in.....— — 11111 ii— imiii— 11— — iiiwn sentcWKSEnaBoaHH 28 but the relationship, cannot be roved. Upper Labortan Dcen-Lcko Sediments In brass Valley the a con-lake facies is well developed, and corresponds well to the d oscriotio: s of Russell (138?) in the Rye Patch and Lull City areas and R, Morrison (in orenarat- Lorh i the Carson desert. These sediments are noil exposed alon- the banks of the flood plain of the Uumboldt River, In addition numerous test wells drilled by the IT, S. Geological Survey during 19 r9 and 1960 no iotr: ted these strata • Individual beds are persistant and can be -traced for the entire distance from Winnemucca to the western edge of the vanned area, Tie re is a slow f cins change in this distance with tee sediments becoming fi or to the southwest. At tie narrows, at the town of Winnemucca, the doo - lake clay has been removed by the Humboldt River. •The maximum thickness of ex osed sediments in Crass Valley is 9? feet (see figure 9) four test wells near this exposure show 99 to 60 feet of unner Lahontan sediments, Therefore, Wi ere is a complete section of upper Lahontan exposed here. East of Winnemucca the dee--lake cloys are not ’"resent in the banks along tie ilood of the "Iumboldt liver. Light te dark fra y clay, slightly siltyp blocky, thick bedded, Qatracoda______Fine sand and s i l t , cross bed- ded„ jpolecypeds In te rbedded sand and s ilt y clay Fine sand, cress bedded, con- torted beds Interbedded sand and s ilt y clay Blocky clay, slightly silty, mostly thick bedded, Ostraceds Cress bedded fin e te medium id water Lme"with s i l t strin gers S ilt y clay Medium grained sand FIGURE 9 Upper lahontan exposed in a bluff ef the Humboldt River fle e d p la in P 'in P S»A <1 QG 30 The Paradise Valley section is quite different from that in Grass Valley. Clay beds are low in the section at the mouth of the Little Humboldt River (see figure 10). Here the sediments are finer toward the base. Small areas exist where clay is the upper-most bed; however, most of the valley is floored by sand and silt. A series of sections is shown to illustrate the changes discussed above (see figure 11). Mechanical analyses were made of ten differ- ent clay samples. These showed rather poor to moderate sorting w:'th the modal diameter in the fine silt (8 to 16 microns) and very fine silt (If to 8 microns) size range. Hone of the samnles have more than 25m in the clay size range (minus', h microns - Grim, 1953). The Grass Valley samnles arc finer than the Paradise Valley samples. X-ray diffraction oatterns were run on the clays. All have similar oatbems a’:d are in the Montmorill- onite group. Near-Shore Sedlments The deep-lake sediments grade shoreward into fine sa ds and silts. Tie fine sands and silts are the equivalent of the upper clay be^s of the deep—lake facies. In some loc- alities the sediments grade into coarse sands and gravel. There are numerous long-shore bars In the ll ill Si i l l 11 n i i . w i H i m j m . m i i j u p p h i U Um u . . . u u w I 0 I j m i l . becomes becomes finer at the base st st Lohontan eolian sand lacustrial, lacustrial, ostracods rare (within (within first 8") to silty cloy, center center silt with lime lenses Silty Silty clay, ostracods rare Fresh water Fresh lime Clayey Clayey silt at top grading rapidly Fresh Fresh water lime top and bottom, Fine Fine lacustrial bedded, poorly sand, FIGURE Po Humboldt Humboldt River (T37N/R38E, S27 Acc), Section at the mouth of the Little covered €>’L ‘ IT -3 cd'io 3 Gras* Valley narrows Paradise Valley ( 3 6/38, 2 0 Cc a) (37/38,27 Acc) (36/37, 26 Dd a) (36/38, 20 Acd) 2 miles vertical horizontal Scale FIGURE II Illustrating the change in sediments between Grass and Paradise Valleys. 33 Mechanical analyses were made of a number of sauries taken from various localities. They are generally moderately well sorted; the modal class most commonly is in the very fine sand size range (.062 to ,125 millimeters). Most of the other samples have their modal class one size range larger or smaller. Some of the sediments are bimodal in character. A number of long-shore, bars were studied. The bars are most numerous along the base of Winnomucca Mountain, where they have been exposed by quarrying. Some of the bars are associated with the earlier part of the upper Labor.tar cycle, and are nrobably part of the basal gravel. Two of the ’our exposed gravel bars are covered with f ve to thirteen feet of very fine sand of the normal ner-shore facies; the other two exposed gravel bars are overlain by post—Lahontan sediments. Size analyses of the gravel bars show so e variation. Three of the bars have bimodal charac- teristics, while two have a single mode in the b to 8 millimeter size range. Sidit feet is the total maximum thickness found in a single exposure of the gravel bars, but twenty-five feet of very fine sand of the normal near—shore facies was encountered in one drill hole. Tie W e s te r n Pacific gravel pit (figure 12) H llU H 'i north focing north south focing south 4329 post La honta n 0 pebbly silt c) 4324 ,■ £/&<>* & o c f& o 0 a Lahontan bar gravel 3 0 0 0 0 0 00 oO 0 0 0 0 O O O' o o £0 O a & ge 0OO 00 10 0 o o o 0 a OO0 000O 00 0 0 00 a 0 0 a 0o o» a o 0000000000a 0O0OO o 0 O 0 O 0 0 0 0 0 :y o a o FIGURE 12 Western pacific R R gravel pit (T 36 N/R 37 E, S 25 Bca) i s illustrative of the gravel pits. Post-labortan Sediments Ten feet is the maximum exposed thickness of post-Lahontan sediments which occurs in a gravel nit on the southeast base of Winnemucca Mountain (see figure 13). Tho thickness of sediments of the post-Lahontan fan on the south flank of Wirn- ernucca Mountain is unknown. One unit of interest is a white siliceous ash wh'c’n lies directly on the Labortan sediments in several localities (see figure 13)• The ash is found in channels in the lake sediments and clearly indicates a hiatus of unknown length at this disconformity. A similar ash is found at a death of 10 to 15 feet in the flood plain of the Humboldt River (J. Hawley, personal communication). Gumboot Lake, formed when sand dunes dammed tho Little Humboldt River, was drained to make farm land. Gumboot Lake sediments were mapped on geo ’.orphic evidence: wave cut notches were formed by the lake dur'rsg its short period of existence. Ro significant difference can be seen from size analysis or H-ray diffraction natterns between the Gumboot Lake sediments and the deep-lake clays. It is possible that the samples analysed were of Lahontan origin (death of samples one foot'1, and Gurnhoot Lake sediments nor-existant. Figure 1*+ presents a generalized cross sect- ion (north-south) of the late Quaternary sediments In the basin. Paleontology The naleontologic work that has been done in the Wlnnemucca area has been limited to Ostraceda of the un^er Lahontan sediments. Ostraceds were noted in the lower Lahontan clay, but no identifi- cation of t'sse specimens has been made. Large frosh water clams and associated small gastropods are found in the sand lenses of gravel bars. Candona oarncaudata Swain (19^7) ar^ Candona sn. fro~ the upper sand were identified by the writer. Cytherissa lacustris was identified from the upper most clay by J. Ilawley (personal communication), who also re^ortsd the Cvpris as abundent and Candona as present. Jones and Mar sell 0905"/ c ons id or Cytherlsa lacustris as c tiara c-.erist.ic of the Provo formation (Provo II formation of R. Horrison, I960) of Lake Bonneville. However, J. ?eth reports this snecies in the upper nart of the Bonneville formation (personal communication). <- > o u t h North 440 42 00 40 0 0 FIGURE 14 Generolized cross section of Gross Vollev l i i i i i mBm ■ . 3 9 SI3 DI1 EE3TT.\HY 'h, P i O Tl..’hrY # More than one hundred size analyses were made of samples taken from scattered noints through out the manned area. Some of these analyses were referred to in the discussion of the Lahontan stratigraphy. All except the very fine sediments were f-rst sieved, through a series of screens which divided the sediments Into fractions which comply with the l/entworth scale (Krumbern and Pettijohn, 193$). Size analysis of the very fine sediments as well as the fine portion from a large number of coarser samples were made using the Bouyouces hydrometer method. A number of samples were then treated with hydrochloric acid and the Insoluble residue (31.V* to 96.3g) sized by the above methods. The results of these tests were plotted as cumulative curves, the sorting index, calculated, the first percentile, and the various quartiles were determined* Microscopic examination of grain-mounts of a series of samples taken along the front of the 3 ast Range showed a variation of mineral content directly related to the source area, of each sample. By the use of laboratory data a distinction can be made between lake and fan sed^me^'ts. fhe use of sorting index alone was not sufficientr *fO to malco this distinct'on as sone lake sediments were poorer sorted than some of the far sediments, Tho first percent) le of the samples was plotted a veinst the median diameter as described by Passaga (1957)• Although clear patternsr are discernible for the two different modes of deposition (see figure 1 , there is a considerable area of am- biguity vhe 'O the two patterns overlap. The writer modified Passaga's graph by plott- ing the first percentile against the median dia- meter of the modal class of the sample (see figure 16'), Tils resulted in two adjacent, hut not over- lapping patterns. The close proximity of the two patterns leaves so-ie possible ambiguity however, there is a definite trend which seems to be signif- icant Lake C»fir*t percentile (micron •) Fan material material & ' r c s o deposition ofProcess asq, 1957) Passaqa, I U E 15FIGURE =ein diameter M=median (after (micron*) 0001 L-J.TE '§ iTBRNaRY GEOLOGIC IISTO R Y Tiie nre-Lahontan geologic history has already been discussed in the section on regional geology* The following sequence of events is suggested for the late Quaternary: 1 * Deposition of alluvial fan and other types of arid and semi-arid sediments following the desiccation of ore-Lahontan lakes, 2. A change in climate followed by the first rise of Lake Lahontan and the deposition of the early Lahontan sediments* Tie lake reached its maximum elevation of MfOO feet during this period. 3 * Desiccation and withdrawal of the lake to the lower basins; denosit'on of alluvial sediments in the Winnenucea area, h. The lake rose again to the ^27" foot level and probably fluctuated about this elevat- ion. Deposition of the bulk of the medial gravels with accompanying alluvial denosits at higher elevations. 7. Pinal rise of Lake Laho tan to the ^360 foot level and deposition of upper Lahontan sediments. 6. Tie final retreat of the lake followed by the formation of the general outline of the present fumboldt River system. Levels of the lake below foot would not have reached this area because of the elevation* Thus tie lake nay fluctuate in the lower basins while subaerial beds are contirously being deposited In the hnnomucca area. These events are sunner- ized in figure. 17. Lake Laho' tan is believed by most writers to bo a bsconsir lake as is Lake Bonneville ( hint, et al, 1933)• Much dating of Lahontan has been done recently by radiocarbon and r^te of salt accur.ulation teclmioubs, There is fairly good agreement that the final desiccation of the lake occurred between 10,000 and 11,r^0 years ago (drdecker and Orr, 1933; Broecker and Walton, 1979? Broecker, Ewing, and 'feeze- , 1.9*30', The first riso of the lake is more obscure and must have occurred later tha1 73? '°0 years ago (Broecker and .’alter., 1939; J. Peth, 107°, strongly disagrees with this dating): Wisconsin time started 9',000 + o 70,700 years ago (Frye and hi liman, I960'1. Figure 18 summarizes Broecker and Orr's (1978) chronology* 4400 Or 5000- 10,0 00- c m•> 15,000- w« Q. o 20,00 0 - *>o >■ 2 5,00 0' gravel 30,000 ? 35,0001 Lahontarr FIGURE 18 Levels of L o k e Lobonton (modified from Broecker ond Orr, 1958, stratigraphy by the writer) h7 iiC! 01101:1 C OROLORY The basal (medial) gravel is ar excellent aquifer near the Humboldt River. Providing this un't is thick enough, it would also be an excell- ent a q u 'for further from the river where it lies below the water table. Where this gravel lies m o n the fans it would make a good bed through which ground water recharge may occur. Streams cutting into the gravel or Into a gravel bar connected to the basal gravel would loose consider- able water to the ground-water reservoir. towever, the.deposits are generally low on the fans because of the high elevation of the are' , and surface water reaches them only in time of flood of heavy spring runoff. The Upper Labor; ta1' and Lower Lahoritan are very poor aquifers. The sand stringers in the fine sediments could not contain much water because they are so thin. The s'lty clays of the lake may act as a confining layer. i+ 8 StJl-2i.-i.RY ITD C O NCL USI O NS The unper lacustral silts and clays of Lake Lahontan 'Tads into coarser sediments (usually fine sard) near the shore of the lake. This sand, when traced around the basin, defined 'tie maximum extent of the last deep-lake stage of Lake Lahontan. Lake Lahontan occupied the valleys around Winnemucca at least twice as is shown by sediments of two deep-lake stages separated by subaerial alluvial deposits. A basal gravel is associated with the rise of the second deer-lake stage. Shore features associated with the frst deep-lake stage are non-existant with the nossible exception of a wave cut notch of M+00 feet in elevation on the north flank of the Sonoma Range, Shore features of the second dee -lake stage consist mainly of gravel bars, most of which are covered by finr'r near shore sands; wave cut notches at the h -3 6 0 foot level are ver’r poorly ^reserved throughout the a r e a . The petrograohic study of tho lake and fen sediments consisted mainly of mechanical analyses of the sediments. The first percentile size was plotted against both the median diameter and the median diameter of the modal class. The patterns which resulted offer a possible means of distin - uishing between the two types of sediments. tt-9 BIBLIOGRAPHY BROECKER, 17. S., and ORR, P.O., (1993), Radiocarbon Chronology of Lake Laborta" and Lake Bonne- ville: Bull. G.3.A., vol. 69, np. 1009-1032. _____ , and !.ALTON, . ., (1999), Re-evaluation of the Salt Chronology of several Great Basin Lakes: Bull. G.3.A., vol 70, pp. 601-618. , E'TING, H . , and HE.EZEN, B.C.,(i960), Evidence for an abrupt change in ci Lnrte close to 11,000 years ago: Am. Jr. Sci«, vol 298, PP. L29JdfP,. FERGUS ON, H. I., HIJLLER, and ROBERTS (1991'', Geology of the innemucca Quadrangle, Nevada: U.S. Geol. Survey Geol. 'Quad. Nap. SETH, J. ., (1999'!, Re-evaluation of the Salt Chronology of several Great Basin Lakes: A Discussion: Bull. G.3.A., vol 70, pp. 637-69-0. FRYE, J.C., and .’ILK , i. (1960), Classificat- ion of the Wisconsin'an stage in tiie Lake Michigan glacial lobe: 111. Geol. Survey, circ. 289. GRIM, R. ., (1953), Clay Mineralogy, McGraw-Hill Co., New York. HUNT, I V 7..RITES, I. , and TU0M.7S., H. , (1993) Lake Bonneville: Geology of Northern Utah Valley, Utah: U.S. Geol. Survey, Prof, paper 297-7. JO': r , O.J., and .037J , 0 , (W?), Pleistocene sediments of lower Jordan Valley, Utah: Utah Geol. Soc., Guidebook to the Geology of Utah, no. 10. JONH , J.C., (191G), The Pleasant Valley, Nevada, e.- rtiouake of October 0, 191 S: Bull. Seism. Soc. Aru, vol py. 190-00J. IHUNBEIN, . and FISTTIJOIIN, F.J., (193p0 , Manual of Sedimentary • otronraohy. 0. Appleto5 - Century Co., Inc., Now York. I!ORRIS Oil, (1960), Field trio in the little Cottonwood Creek area, Salt Lake County, Utah: Friends of the Pleistocene, Pocky Fountain Section, 6th Annual Field Conference. ONUoC Au:, 3. JR., (I96 '), Carbonate compounds ‘n some alluvial fans of Northern Grass Valley, Nevada: unpublished thesis ( . A).University of Nevada. PP 5GAG , , (1957), Texture as characteristic of cl stic deposition: Bull. A. . . vol V 1, pp. 19 A -19 • ROBINSON, rl. L03LTS, O.J., and PHOENIX, D. (19!+8), Groundwater i Grass Valley and: ad- jacent portions of the Humboldt River Valley, Forshi: - and Humboldt Counties, Nevada: Nevada State Engineer Hater Resources Bull, No. 9 (unpublished)• 51 , (191+9) ? Groundwater in Paradise Valley, Nui'iboldt County, Nevada: Nevada State Eng- ineer 7ater Resources Null. N o. 1 0 . l O'. ; :_iij 1 , • < • , (1 385), Geologic history of Lake Labortan, a Quaternary lake of northwestern Nevada IT.S. Geol. Survey, mono ranh 11. VflTTEP, C. (1957), Geodetic measurements in the Dixie Valley Area: Bull. S e i m . Soc. Ah ., vol !+7, p p . 321-825. .IGLOO]!, C . (195^, Cretaceous and Tertiary orogeny in the Jackson fountains, Nuuboldt County, Nevada: Pull. , vol 5?, PP. 2378-2398. , Geology and nrroral resources of NumboIdt County, Nevada: Nevada Pur. of Nines Bull. (± nreoar?tion)• : "IN'. NTT, (1938), Lexicon of geologic na.'es of the United States: U.S. Geol. Survey Bull. 896, p. 99^. JIPCON, '. (1060), Geophysical investigations in the Iiriboldt River Valley no-r Ninnemucca, Nevada: unpublished thesis 0 .0. , Univers .tv of Nevada, Definition of So: So is the Trask "sorting coeficientand is defined by the following equation: So = T/ 7~~-T where Q-j is the first quartile (the larger diameter) and is the third quartile (krumbein and PettiJohn, 1938, pp* 230-231)* Definition of 0: Phi is the negative log to the base 2 of the 1 diameter values in millimeters* This changes the uneaual geometric interval of the Wentworth grade scale to an arithmetic interval (Krumbein and Pettijohn, 1938, pp* 8*4—85)* iiiiililBil