The Jackpile Sandstone Member of the Morrison Formation in West

Home , Morrison Formation

TheJackpile Sandstone Member 0f the MorrisonFormation in west-central New Mexico- a formaldefinition byDonald E. jwen,Consulting Geologist, Tulsa, 0K 74152,and Lester J. Walters,Jr. andRonald G. Beck, ARCO Oil and Gas Co., Dallas, IX75221

The JackpileSandstone Member of the uranium mine. The JackpileSandstone is stonelenses Contactswith the underlying Morrison Formation(Upper Jurassic)in west- typically a whitish, crossbeddedsubarkose Brushy BasinMember of the Morrison For- central New Mexico is named here formallv with clay matrix and interbedded, varie- mation may be gradational, scoured, or from a stratotype near the Jackpile-PaguatL gated, pale-greento red, bentonitic mud- interbedded. The Jackpileextends only a short distancesouth of the stratotvDedue R.5W. to truncation along the basal Dakota unconformity. However, it extendsnortheast to Lamy, north to near Cuba, and a short distancewest and a longer distancenorth- west into the subsurfaceof the San Juan Basin.Thickness of the Jackpileranges from near zero to 300ft (91 m); at the stratotype it is 100 ft (30 m) thick. Crossbeddingin- dicatesa regional easterlypaleocurrent-flow direction for the braided-streamand distal alluvial-fan complexesin which the Jackpile was deposited. Source areas were to the west and southwest,south of Gallup, and in the Mogollon Highlands.

Introduction The Jackpile sandstone of economic usage has been employed informally in stratigraphic nomenclature for a distinctive bed in the uppermost part of the Brushy Basin Member of the Morrison Formation in west- central New Mexico since the Jackpile uranium body was discovered in that bed during 1951.The stratigraphic name fackpile has

Alsoin this issue Temperatureof.mineralization in Mogollonmining district p. 53 EarlyPaleocene vertebrates, 1000 2000 3000 4000 50oo 6000 7000 FEET SanJuan Basin p. 56 1 KILOMETER Service/News p. 61 Statfnotes p. 64 JA c K P IL E s A N JURi.,s-sJgW JURASS|C B'o'"o!'o#r'$?o'ft Kffi lJ f,,BH'#J"R^P3l ^yf #3 fi ' Gomingsoon Fossilrock glaciers on CarrizoMountain QUATERNARYDEPOSITS. CRETACEOUS uNDrvrDEDl | | IDAKOTASANDSTONE Adobeas a buildingmaterial Dinosaursfrom the McRaeFormation. FIGURE 1-Geologic index map of the stratotype area of the Jackpile Sandstone Member (Morrison Formation). Note location of surface measured section illustrated in Fig. 2 and subsurface reference SierraCounty section (DDH 2664) illustrated in Fig. 3. LE is the location of an additional measured section. The map MorphyLake State Park has been simplified and modified from Schlee and Moench (1963b); small igneous dikes and sills hav-e been omitted. appeared in many publications in various sec. 35, T. 11 N., R. 5 W., Cibola (formerly Following establishedinformal usage,the forms since its first published use bv Free- Valencia)County, New Mexico. The contig- fackpileSandstone Member of the Morrison man and Hilpert (1956),The Jackpilesand- uous Jackpile-Paguatemine is the world's Formation is split from the underlying Brushy stoneappears on many geologicmaps (e.g., largesturanium mine;24.1million metrictons BasinMember. The Brushy Basinis the most Schleeand Moench, 1,963a,b), in many gov- (26.51million short tons) of uranium ore were extensivemember of the Morrison, being ernmentreports (e.g., Moench and Schlee, shipped between 1954,when the mine ^teaupresent over nearlv all of the Colorado Pla- 1967;Santos, 1.975),and in several correla- opened, and 7982, when the mine closed (Craig et a1.,igSS, p. 155).At the stra- tion diagrams(e.g., Owen andSiemers,1,977; (Mclemore, 1982). The stratotype for the totype, the fackpile is overlain unconformably Maxwell, 1982).In spite of its use, the fack- JackpileSandstone is a measuredsection of by the basalsandstone bed of the Oak Can- pile sandstonehas never been named for- a surfaceoutcrop in SEt/+NW1/s SW1/a sec. yon Memberof the DakotaSandstone, which mally. Nash (1,968,p. 738) used the term 10, T. 10 N., R. 5 W., Mesita Ttlz-min quad- forms the rimrock in all of Oak Canyon (Fig. |ackpile ". . as if a Morrison member."The rangle(Fig. 1).This locationis approximately 4). late Gary Fleschsuggested that the Jackpile 2.5 mi (4 km) southwestof the original mine should be a formal member of the Morrison opening. The section (Fig. 2; Table 1) was Description Formation and established two reference measuredon a series of south-facingcliffs LrrHolocv sectionsfor it, but he did not actually for- north of the south fork of Oak Canyon. These malize it (Flesch, 7974; 1975). cliffs occur on the face of an unnamed tri- The fackpile Sandstonevaries consider- The purposesof this paperare to designate angular mesa between South Oak Canyon ably in detailed lithology. Typically, it is an crossbedded,fri- the fackpile SandstoneMember of the Mor- Mesaand North Oak CanyonMesa at a point off-white to yellowish-tan, rison Formation as a formal stratigraphicunit 0.3mi (0.5km) eastof NM-279. A subsurface able, subarkosicsandstone with mostly me- meeting the requirementsof the new North referencesection (Fig. 3) also is provided from dium and coarse,subangular to well-rounded, American StratigraphicCode (North Amer- a core and log taken in Anaconda Diamond poorly to well-sorted grains in a white clay ican Commission on StratigraphicNomen- Drill Hole 2664in SWt/+NE1/+ NEt/a of the matrix. The white clay matrix, which is a clature, 1983)and to discussthe deposition samesection, approximately 0.8 mi (1.3km) distinctive feature of the Jackpile,is mostly very of the fackpileSandstone. northwest of the stratotype (Fig. 1). Flesch kaolinite.Some beds are coarsegrained (1974, 1975) suggestedtwo reference sec- and a few, chiefly at the base of scour sur- faces,contain a few pebbles,mostly of chert. Nomenclatureand location tions farther to the north that also are avail- able for study. His 1975section was published Chert-oebblezones are more common in the The JackpileSandstone is named for the in Siemerset al. (1975,p. 30). south*est part of the Jackpiledistribution, fackpile mine that was opened in the SEtin in the vicinity of the stratotype, than to the north and east.Some fackpile beds are fine- ELECTRICLOG grained sandstone, but very fine grained ANACONDADDH 2664 SW NE NE SEC 70 sandstoneand siltstone beds are rare. Po- T1ONRsW CENTURYGEOPHYSICAL COFP rosity rangesfrom near )Vo to 20% or more SELF poTENTtAL MAY 30, 1969 BESTSTANCE and varies inversely with clay-matrix con- tent. Most outcropscontain a few thin lenses and beds of variegated, pale-greento red, New AAexfico GEOLOGV . Scienceand Sorvice Volume 6, No. 3, August 1984

published quarterly bY New Mexico Bureau of Mines and Mineral Resources a division of New Mexico Institute of Mining & Technolo8y

BOARD OF REGENTS Ex Officio Toney Anaya, Gooernor of Nru Mexico Leonard Delayo, Supqintendent of Public lnsttuction AgDointed Judy Floyd, Pre; ; L977 1987, Ias Cruces William G Abbott, Secty/Ireas ,7961-1985, Hobbs Donald W Morris, 1983 1989, Los Alamos Robert Lee Sanchez, 1983 1989, Albuqueque Steve Torres, 7967-7985, Socorro

New Mexico Institute of Mining & Technology President Laurence H Lattman New Mexico Bureau of Mines & Mineral Resources DirecLor Frank E Kottlowski Depufy Director George S Austin Subxriptions: Issued quarterly, February, May, August, .,r."ro", "o^o"ro*.ffiotoo" November; subscription price $6 00/yr uuosrorueffi@cusrs Editorial mqllet Contributions of possible material for consrderation in future issues of NMG are welcome FIGURE Articles submifted for publication should be in the editor's 3-Electrical log and core log of the fack- hands a minimum of five (5) months before date of pile Sandstoneand adjacentunits at the subsur- publication (February, Ma, August, or November). face referencesection. See Fig. I for location of Address inquiries to Deborah A. Shaw, editor of Nru DDH2664 "Squared off" ends of spontaneouspo- Mexico Geology, New Mexico Bureau of Mines & Mineral Resources, Socoro, NM 87801 FIGURE 2-Craphic measured section of the Jack- tentialand resistancetraces indicate off-scale read- Published qs publk domain, thercfore reprcducible without pile SandstoneMember (Morrison Formation) and ings. Kdoc is the Oak Canyon Member of Dakota permission Source credlt requested adjacentunits at the stratotype. SeeTable 1 for Sandstone;fmj is the JackpileSandstone Member Ciculatiofl:1,4N description of units and Fig. 1 for location of of Morrison Formation;Jmb is the Brushy Basin Printer: lJniversily of New Mexico Prinling Plant stratotype. Member of Morrison Formation.

August 1984 Nm MexicoGeology TABLE l-Lrrnolocrc DESCRIPTIoN oF JACKPILE fining-upward sequence at brown; medium to verv coarse SaNosroNgsrRATorypE. Unit numbers correspond base; sharp lower contacti grained, moderately to poorly to numbers in Fig. 2. moderately resistant . . 10 ft (3 m) sorted, angular to rounded; clay matrix; abundant mud- Unit Description Thickness stone clastsup to 6 inches (15 IJ Sandstone (subarkose), off- cm) diameter in bed near top; DakotaSandstone: white, weathers tan; fine to medium-scale,planar to wedge basalsandstone bed of medium grained, moderately crossbedding; load casts on Oak Canyon Member: to poorly sorted, subangular base with up to 1 ft (0.3 m) 18 Sandstone(quartz arenite), tan, to subrounded; clay matrix; relief; sharp, very uneven weathers rusty brown; very small-scale trough crossbed- lowercontact. ....3-5ft fine to fine grained, well ding; sharp, uneven lower (0.9-1.5m) sorted, subangularto rounded; contact; moderately resistant ....2-4ft iron oxide and silica cement; (0.6-1.2m) Mudstone, grayish-green, thinly to poorly bedded (par- fresh and weathered; silty, tially bioturbated); abundant t2 Sandstone (subarkose), off- sandy, feldspathic, common Skalithu burrow fillings; sharp, white, weathers tan; fine to glass shards; thinly bedded; planar lower contact; eroded very coarsegrained, poorly to sharp, irregular lower con- back from canyon rim ...... 2 ft (0.6 m) moderately sorted, subangu' tact;nonresistant...... 0-3ft lar to rounded; clay matrix; (0-0.9m) chert pebbles,especially rn 17 Sandstone(quartzarenite),tan, lower 3 ft (0.9 m); medium- 5 Sandstone (subarkose), yel- weathers rusty brown; very scale planar crossbedding; lowish-tan, weathers light fine to fine grained, well sharp, planar lower contac! brown; fine to coarsegrained, sorted, subangularto rounded; moderatelyresistant ...... 2-9ft poorly sorted, subangular to silica cement; carbonaceous; (0.6-2.7m\ medium-scale planar cross- rounded; clay matrix; me- planar bedding; abundant Planolites 11 Sandstone (subarkose), off- dium-scale crossbed- burrow fillings in lower 4 white, weathers tan; fine to ding and flai bedding; sharp, inches (10cm) that extend into coarsegrained, well to poorly flat lower contact; moderately unit below; planar, uncon- sorted, subrounded to resistant .. 3-5 ft formable lowei contact; forms rounded; clay matrix; mud- (0.9-1.5m) canyonrimrock...... 13ft(4m) stone cobble zone near mid- Total thickness . 15 ft (4.6 m) dle; medium-scale Dlanar 4 Sandstone(arkose), very light crossbedding and laminated tan, fresh and weathered; fine flat bedding; sharp lower con- to very coarse grained, mod- Morrison Formation: tact; moderatelyresistant...... 8-16 ft erately to poorly sorted, sub- Jackpile SandstoneMember: (2.4-4.9m) angular to subrounded; clay 16 Sandstone (lithic subarkose), matrix; quartz overgrowths; greenish-gray, fresh and 10 Mudstone, grayish-green, small-scale trough cross- weathered; medium to coarse fresh and weathered; silty, bedding, gradational lower grained, fines upward, poorly sandv, mudstone-clast con- contact moderatelyresistant. . 5 ft (1.5m) to very poorly sorted, sub- glomerate in par! sharp lower rounded to rounded; abun- contact; non-resistant; with 3 Sandstone (subarkose), light dant clay matrix, especiallyin sandstone wedge (subar- vellowish-tan. f resh and upper part; subrounded to kose),light tan, weatherslight weathered; fine to coarse rounded chert pebbles brown; verv fine to medium grained, several fining-up- throughout, angular sand- grained, well sorted, sub- ward sequences,well to poorly stone pebbles and cobbles in rounded to rounded; clay ma- sorted, subrounded to upper part, abundant kaolin- trix; few chert pebbles; rounded; clay matrix; chert ized feldspar grains; medium- composedof one set of wedge pebbles near base; small-scale scaletrough crossbedding,ex- crossbedding; sharp lower planar crossbedding; sharp, cept in upper clayey par! gra- 1l AlCr contac! moderately resistant . flat lower contac| weakly dational lower contact;recedes t/O R-l 4 m\ resistant . . .2.5 ff (0.8m) under canyon rimrock above 8 ft (2.4 m) Sandstone(arkose), light-tan, weathers dark tan; medium to 2 Sandstone (arkose), light yel- 15 Sandstone (subarkose), off- coarsegrained, several fining- lowish-tan, fresh and weath- white, weatherstan; medium upward sequences,moder- ered; fine to very coarse to coarsegrained, moderately ately to poorly sorted, sub- grained, rnoderately to poorly to poorly sorted, angular to angular to subrounded; clay sorted, angular to rounded; rounded; abundant clay ma- matrix; few mudstone clasts; clay matrix; basal chert pebble trix; planar and wedge cross- medium-scale wedge and and mudstoneclast zone; low- bedding with some massive planar crossbedding; sharp, angle, medium-scale wedge beds; one fining-upward se- planar lower contact; moder- crossbedding; sharp, uneven quenceat basewith basalchert itely resistant 8 ft (2.4 m) (scoured) lower contact pebbles and mudstone clasts; changing to gradational to sharp, irregular lower contac! west;weakly resistant...... 9.5 ft (2.9m) (subarkose), moderatelyresistant 17 ft (5.2 m) Sandstone off- Totalthickness ...... 100 ft white, weathers tan; very fine (30.5m) to medium grained, well to moderately sorted, angular to Morrison Formation: 74 Sandstone (subarkose),tan, rounded; clay matrix; thinly upper mudstone bed of fresh and weathered; fine to flat-bedded, changesto cross- Brushy Basin Member: coarsegrained, moderately to beddedto west; sharp,planar 1 Mudstone, grayish-green, poorly sorted, subangular to lower contact; weakly weathers light grayish-green; rounded; clay matrix; mud- resistant 6.5 ft (2m) silty, sandy; poorly bedded, stoneclasts and chert pebbles fractured; lower contact con- in basal bed; small and me- cealed;non-resistant. 6 ft (1.8 m) planar dium-scale crossbed- Sandstone (lithic subarkose), Totalthickness . . 6 ft (1.8 m) ding and missive beds; one off-white, weathers light

New Mexico Geology Augtst 1984 bentonitic mudstone. Locally,these may be thick and extensive.Mudstone clastsare fairly abundantin somesandstone beds and range from pebbleto boulder size. At the stratotype,Jackpile sandstones have an averagecomPosition of 58Voquartz and chert, 1.6%feldspars, SVo rock fragments,and 2lVoclay matrix, basedon point countsof 22 thin sectionsfor major components (Table2; Fig. 5). Significant minor components include very fine crystalline pyrite, organic carbonaceousmaterial not recognized easily in hand specimens,iron ofde, and iron car- FELDSPATHIC bonate minerals. Of the 22 samples,15 are LITHARENITE subarkosesaccording to the classificationof LITHIC SUBARKOSE McBride (1963).Average porosity by point count is 10%. FIGURE S-Plot of classificationof fackpile Sand- stone samplesfrom the stratoffpe. The sandstone CoNracrs classificatibnis from McBride (ifoe). The Jackpile The contacts of the fackpile Sandstone sandstonesare predominantly subarkosic(75 of22 Memberwith adjacentstratigraphic units are samples). distinct and easilyrecognized in outcrops and cores,but not so easily recognizedon well logs.The basalcontact with the Brushy Basin tonguing just west and south of the strato- Member is well marked by a color and lith- type in the samequarter section (Fig. 1). ologic changefrom greenand red mudstone The upper contact of the jackpile Sand- to off-white to yellowish-tansandstone (Fig. stone with the Dakota Sandstoneis an easily 6). At most localitiesthis lithologic changeis recognized unconformity with a typical lith- FIGURE 4-View of the Jackpile Sandstone and ologic and color change from the light-col- adiacentunits at the stratotype.Person is gradational through a few inches; at some standing to the on upper part of BrushyBasin Member. Dark rim- localitiesthe contact is sharp and scoured; ored, near-white |ackpile sandstone rock at skyline is basal Oak Canyon Member ol and at a few localities,intertonguing of Brushy darker colored, commonly iron-oide-stained Dakota Sandstone.Light-colored cliffs are Jackpile Basinmudstone and fackpile sandstonetakes Dakota sandstone (Fig. 7). A very thin con- SandstoneMember (thickness:100 ft; 30 m). placewithin a few tens-offeet. Schleeand glomerateor pebbly sandstonebed is fairly Moench (1963b) mapped such an inter- commonon the unconformity.The basalDa-

TABLE 2-MoDAL coMposrrroNs oF THE Iecrprle SeruosroNl AT THE srRATorypE.

Constituents (%) Iron oxide/ Sample Rock Heavy iron Pyrite/ Points (unit) Quartz Chert Plagioclase K-Feldspar fragments Clayl Porosity minerals Biotite Calcite carbonate OCM, Total counted 1(1) 424 1.0 5.6 3.4 1.0 A1 I tr 1.0 tr 00 4.6 1.0 107.2 323 2(2) 47.0 2 9 10.8 3.5 IJ 30.2 1.0 tr 00 0.0 0.0 2.9 99.6 315 3(2) 39 7 4.0 9.0 9.3 5.7 70.7 18.0 0.0 0.0 20 1.3 tr 99 7 300 4(2) JL Z I.J 77.2 72.7 71 15.3 tz.J 10 0.0 tr 1.9 tr 100.0 308 s(3) 577 1.0 72.5 5.1 25 2.9 15.1 tr 00 0.0 tr 2.6 99.4 372 6(4) 52.1 1.0 76.5 3.6 36 4.6 74.2 10 u 0.0 t.6 7.6 99.8 303 7(s) 50.2 r.6 10.5 1.6 J.J 13.8 8.8 tr 1.0 00 5.9 3.6 100.3 305 8(6) 270 4.8 4.8 0.0 00 66.3 7.6 00 10 0.0 tr tr 99.5 309 e(7) 47.5 2.6 1r.3 5.0 7.4 15.3 9.3 0.0 tI tI 1.0 6 3 99.7 301 10(8) 48.9 tr 10.5 1.6 J.J 75.4 74.7 00 tI 0.0 1.0 4 9 99.7 305 11(e) 41.3 1.2 1,4.9 3.5 3-9 4.8 1.6 1.0 0.0 0.0 162 r7.7 100.1 315 12(10) 5r.8 r.3 102 2.0 .)..) 70.2 72.5 tr 0.0 0.0 0.0 8.5 99.8 305 13(11) 45.8 1.0 10.4 2.6 3.9 73.6 7.8 0.0 tr 0.0 00 r4.9 100.0 308 14(11) 56.4 1.6 9.0 3.2 8.0 16.3 0.0 tr 0.0 00 1 0 100.0 372 1s(11) 48.0 3.9 7.2 2.9 2.0 8.5 770 0.0 lr 0.0 9.7 1.0 99.6 306 16(11) 49.8 2.2 13.8 1.3 6.7 77.2 729 0.0 u 0.0 LJ 1.3 99.9 311 17(r2) 51.3 r.2 6.7 3.8 n1 728 18.3 0.0 0.0 0.0 0.0 7.6 99.9 3t2 18(13) 61.4 2.6 7.5 1.3 L.J 9.1 104 0.0 1.0 0.0 0.0 4.9 100.5 308 19(1.4) 44.7 2.0 ll J 3.6 5.8 188 9.1 0.0 0.0 0.0 00 4.8 100.1 301 20(1s) 52.4 1.6 84 79 3.2 20.4 3.6 0.0 0.0 0.0 2.6 5.8 99.9 309 21(1s) 46.6 2.0 62 7.6 4.6 28.5 7.5 0.0 0.0 0.0 0.0 2.9 99.9 305 223(16) 48.6 4.5 37 3.7 11.1 28.4 0.0 0.0 0.0 0.0 0.0 100.0 109 Mean 46.8 2.0 9.9 3.5 4.0 777 100 Ir tr tr A1 3.7 999 DakotaSandstone 23(77) 6s.3 1.6 16 00 tr 0.0 tr 0.0 0.0 0.0 0.0 31.5 100.0 JII 24(18) 82.4 00 1.0 0.0 0.0 71 78 0.0 00 0.0 r.0 1.0 100.3 307

Notes: 1. lncludes clay pore fillings, clay rims, and matrix 2. OCM = Organic carbonaceousmaterial 3 Grain mount, porosity was not determined

August 1984 New MexicoGeology gamma-raycurves and an increasein resis- Schlee(1967, pl. 3) showed that the Jackpile tivity due to the lithologic changefrom Brushy extendsnorthwest into the subsurfaceonly Basin mudstone to Jackpilesandstone (Fig. 2-3 mi (3-5 km), and Adams and Saucier 3). However, becausethe lower Jackpilelo- (1981)showed that it extendsonlv 6 mi (10 callyintertongues with the upperBrushy Ba- km) northwest from the vicinity of ihe strato- sin, becausemudstone lenses occur in the tyPe. Jackpile, and becausechannel-sandstone The extentof the Jackpilenorth of the stra- lensesoccur in the Brushv Basin. the exact totype is a subject of some disagreement, locationof the contacton somewell logs is although most recent authors agree that it debatable. extendsnorth 50-70 mi (80-110km) to ap- The fackpile-Dakota contact, an uncon- proximatelylatitude 36' N. nearCuba, New formity, does not register distinctly on well Mexico(Fig. 9). Woodward and Schumacher logs becauseit is generally a sandstone- (\973)traced it north to latitude 36"2'.Flesch FIGURE 6-Brushy Basin-Jackpile contact at the sandstonecontact. It can be correlatedwith (7974)mapped the north to 35"7'30' stratotype.Note the iedge of |ackpile JackpileSandstone some uncertainty. However, in the subsur- and was confident that it resting on fracturedBrushy Basinmudstone. extended at least face referencedrill hole (Fig. 3) the upper- north of 35"45' (Flesch,personal communi- most Jackpileis mudstone and the lowermost cation 1975). Saucier (1974) extended the Dakotais sandstone,so that the contactmay fackpilenorth to approximately35"45'. Lupe be placedat the S.P.and resistivitydeflei- (1983)correlated the Jackpilein the subsur- tions. facenear the outcropnorth to approximately 35"50'. Santos (1975)mapped the DlstnrsutroN Jackpile north to approximately35'; Owen and Sie- The extentof the JackpileSandstone to the mers (1.977)gave evidencethat the Jackpile south, southwest,and southeastof the stra- extendsto approximately36'. totype is closelylimited by truncation along The problem in definine the northern ex- the basalDakota unconformity. Accordinglf tent of ihe Jackpilelies in fistinguishing be- the fackpile is not present south of the Rio tween the JackpileSandstone and the Burro SanJose valley (Fig. 9) southwestof the stra- Canyon Formation. These two units are of totype (Moench, 1,963;Moench and Schlee, similar lithology and identical stratigraphic 1.967,pl. 3). The fackpile also is truncated position between the Brushy Basin Member FIGURE 7-fackpile-Dakota contact at the strato- southeastof the stratotvpeon the northern of the Morrison Formation and the Dakota fype. The contact, an unconformity, is at the color part of Mesa Gigante(Moench and Puffett, Sandstonealong the Nacimiento front near change from light-colored to Jackpile dark,colored 1963a,b;Moench and Schlee,1967, pl.3) and Cuba. Owen and Siemers Q977, p. 180) Dakota midway on hammer handle. The Dakota is not present south of there. Moench and is characteristically more resistant than the Jack- pile and forms an overhanging ledge. 108"00' 107'30 107"00 106"30', 106"00

kota is a fluvial-channel sandstone at some localities and a transgressive-marine sandstone with sand-filled burrows of Planolites extending down a few inches into the Jack- pile at other localities, including the stratotype (Fig. 8). The uppermost Jackpile may be green or red mudstone instead of sandsione at some localities. Rarelv a basal Dakota sandstone bed is not preient, which leaves a black, carbonaceous shale of the Dakota

LAMi left of spontaneous potential (S.p.) and ( z I -;\ PIGU '" ABSENT \-- --Ll ssrRlr6rypeI 1-

ckpile Sandstone in west-central New Mexico The area in the eastern part of the studv area, but has FIGURE8-Close-up view of sand-filledPlanolites thick Rio Crande graben fill. The boundary on the burrows on Dakota-Jackpileunconformity. The re basal Dakota unconformity. The subsurface burrow fillings are approiimately dis- I inch (2.5 cm) aucier (1981, pl. 3). The approximate in diameter. southern limit natically along the northern edge of the map.

Neto Mexico Geology August 1984 pointed out that the only noticeablediffer- east, it is 125 ft (38 m) thick. The Jackpile from one inch to severalfeet. Regionally, the encesbetween the Burro Canyon and the variesconsiderably in thicknessin the vicin- averagedip direction of the crossbeddingis but local and bed-to-bedvariations fackpile along the eastern flank of the San ity of the stratotype.The stratotypeis located easter-iv. 32measurements Juan Basin are: 1) the Burro Canyon has an on the west flank of a syncline mapped by do occur.At the stratotype, unconformablebasal contact, whereas the Moenchand Schlee(1967, pl.3) in which the fackpile has a conformable, but locally fackpilevaries in thicknessfrom 90 to 120ft scoured,basal contacU 2) the Burro Canyon (27-37m) due to slight discordancein struc- is generally a conglomeratic sandstone, ture betweenthe Jackpileand Dakota.At an- whereasthe Jackpileis generallyfree of con- other section,measured on the south faceof glomeraticsandstone excePt for a few peb- South Oak Canyon Mesa, 0.7 mi (1.1 km) bles near the base. Basedon these criteria, south of the stratotype (LE on Fig. 1), the more strongly if it were not for a scattering in the upper we concludethat the fackpile extendsnorth Jackpileis only 52 ft (16 m) thick. of five weslerly dip directions to the excellentexposure at lat. 35'59'20"N. Regionally,the Jackpilealso variesconsid- part of the fackpile. Other sedimentary rare in the roadcutbetweenthe Nacimientoopen- erably in thickness.The Jackpileattains its structuresseen in the fackpile include casts, pit copper mine and tailings pond in SWt/+ maximum thickness and greatest average parting lineations, ripple marks, load NEt/+SEl/r sec. 2, T. 20 N., R. 1 W., 3.8 mi thicknessnortheast of the stratotype in an and very rare insect burrows. (6.1km) southeastof Cuba. Exposuresnorth east-northeast-trending,thick belt that is 13 of this locality are rare for about 17 mi (27 km) and so poor that a clearBurro Canyon- |ackpiledistinction could not be made. How- ever, the next series of well-exposed out- cropsnear Gallina (Fig. 9) from about 36'15' north clearly shows Burro Canyon charac- 2) showed that most of the fackpile is be- teristics. tween 60 and 120ft (18and 37 m) thick and The fackpile Sandstonecan be recognized that it wedgesout locally.Farther north, the in some wells near'the outcroP west of the fackpileavdrages about60 ft (18m) in thick- Nacimiento front, but we have not studied ness,but it varieslocally in the outcropsbe- to any greatextent its distribution in the sub- tween about lat. 35'30' and 35'40' N. (Fig' surfateof the Sanfuan Basin.However, Ad- 9). The Jackpileis thicker, generally about ams and Saucier(1981, pl. 3) have mapped 130ft (40m), but locallyvariable from 35'40' the subsurfacefackpile along a northwest to its northern extentnear 36o (Fig. 9). Santos

VECTORIilAG = 525% NUMBEROF READINGS distances.Measured thicknesses there range F STAT = 223 from about50 to 110ft (15-33.5m). FIGURE ll-Compass rose diagram of fackpile SsprvrpNrrRnvSTRUCTURES crossbedding directions at stratotype' The north- indicate paleo- sedimen- easterlv mode and mean (53') Crossbeddingis the dominant The mean direction is crop into the subsurface.It aPPearsthat the (Fig. .rr.r"n[-flo* direction. tary structure in fackpile sandstones 10). significantat greaterthranT% The small, can be correlatedseveral miles far- statistically fackpile southeast'erlymode is not statistically significant. north on many of his well logs. ther west and All five westerly readings are from the uPPer Part be mapped easily to the The ]ackpile can of the Jackpile. points where it enters the subsurfacein the itio Grande graben 20-25 mi (32-40 km) northeast of the stratotype. It is present in InterPretation somewells in the grabenarea. For example, the Jackpilecan be recognizedon the electric Acs log of the Shell No. 1 Santa Fe Pacificwell No index fossilshave been reported from (59 the stratotyPe(Fig. 43 mi km) northeast of the JackpileSandstone; therefore, no well- 9) at depths from 5812 to 6907ft (2075-2105 defined, paleontologicallybased age,is m). A cbre across the Jackpile-Dakotaun- known. The only fossilsthat have been discovered in the Jackpile are a few specimens of carbonaceous and petrified wood frag- insectburrows, and uniden- FIGURE 1O-Easterly dipping crossbedding in mentsand logs, bones. The stratigraphic lower part of JackpileSandiibne at stratotyPe.Note tified dinosaur the thinner, plane-bedzone in the middle part. position of the Jackpilebetween the rest of nearly all the isolatedoutcrops as far north- Large holes in sandstoneare molds formed by ihe Morrison Formation (reportedly Upper Mexico (Fig. 9), 14 mi (23 eastas Lamy, New weatheringout of mudstone clasts. furassic)and the Dakota Sandstone(Ceno- km) south of Santa Fe and 87 mi (140km) manian or lowest Upper Cretaceous)would northeastof the stratotype.This distribution allow it to be placedin the Upper furassicor east of the Rio Grande has not been well About 90Voof Jackpile sandstones are Lower Cretaceousor both. Rubidium-stron- recentlypointed out by Owen known, but was crossbedded;most of the remainderare flat- tium isotopic ages of very early, diagenetic (1e82,p.268). bedded and a few are massive.The typical barren-rockmontmorillonite from nine sam- crossbedis a medium-scalewedge set with plesof the fackpileSandstoneat the Jackpile-- TurcrNnss internal, planar cross-laminations.Tabular- Paguatemine have a mean isotopic age of * to Brookins(1980, p. At the stratotyPe,the JackpileSandstone sets,trough-sets, and concave-uPcross-lam- 1.41 14 Ma according from is 100ft (30 m) thick; in the subsurfaceref- inations are less common. Thicknessof sets 54). This isotopic age was recalculated * Lee and erencesection 0.8 mi (1.3 km) to the north- averagesabout one foot (0.3 m), but ranges the 146 5 Ma age reported by

August 1984 Nao MexicoGeology Brookins(1978). Such an isotopicage would deposit derived from a source area to the Conclusions give a minimum age for deposition of the southwest and deposited in a fairly arid cli- The Jackpile SandstoneMember is named fackpile,but probablyit is closeto the actual mate. Recently, Beil (1981)found evidence of here formallv as the uppermost member of age of deposition. Unfortunately, the nu- tuffs that were altered in an arid climate and theMorrisonFormation (Upper Jurassic) from merical boundariesfor ages of the Late Jur- closed-basin evaporite minerals in the asso- a stratotype exposed near the fackpile-Pa- assicand Early Cretaceousare in considerable ciated Brushy Basin Member including the guate uranium mine in Cibola County, west- disagreementin the four most recentlypub- area where the Jackpile Sandstone is present. centralNew Mexico.The stratigraphicname, lished radiometrictime scales(Odin, 1982a, In order to account for the logs deposited in Jackpile, has been used informally for this b; Harland et al., 1,982;Palmer, 1983; van the Jackpile, the source area of jackpile sed- unit by numerous authors for many years. Hinte, 1976a,b). The iments may less arid furassic-Cretaceous have been somewhat The Jackpile is typically a whitish, me- boundary occurred 130Ma accordingto Odin than at the depositional site. However, after dium- to coarse-grained,crossbedded, sub- (1982a,b), 135 Ma according to van Hinte Jackpile deposition and before Dakota dep- arkosic sandstone with clay matrix and (1976a,b), and 744Ma accordingto Harland osition, there was a period of intense weath- interbedded,variegated, pale-green to red, et al. (1982)and Palmer(1983). An ageof 742 ering in a humid climate that produced the bentonitic mudstone lenses. At the strato- Ma would have occurred sometime during weathered feldsnars and white kaolinite in type the sandstoneaverages 58% quartz and the Late JurassicEpoch accordingto almost the fackpile (Adams and Saucier, 1981',pp. chert,1,5%feldspars, 5Vo rock fragments, and all recentlypublished time scalesexcept the 33-34). 21Voclay matrix. onesof Harlandet al. (1982)and Palmer(1983), In our view, the fackpile was deposited by The lower contact of the Jackpile with the whereit '(byiust barely falls within the Earlv Cre- low to moderate sinuosity, easterly flowing, Brushy Basin Member of the Morrison For- taceous only'2 m.y.). On Odin's'scale sandy braided-stream systems and on the mation is gradationalthrough a few inches, (I982a, b) 142 Ma occurred during the Ox- distal portion of low-gradient alluvial-fan Iocallv scoured. and interbedded at a few fordian Age of the Late Jurassic. complexes. Migrating sand bars of various localiiies.The upper contactwith the Dakota Until much closeragreement is reachedon shapes in shallow water under low to mod- Sandstoneis an unconformity. numericalcalibration of Latefurassic and Early erat:eflow velocities in the lower flow regime The Jackpileextends only about 10 mi (16 Cretaceousage boundaries, we canonly con- formed the abundant crossbedding in the km) southwest and 8 mi (13 km) southeast clude that the JackpileSandstone probably sandstones. The considerably less abundant, of the stratotype due to truncation along the was deposited during the Late Jurassicbe- flat-bedded sandstones may have been basal Dakota unconformity, but it also ex- causeBrookins' dates (1980)are minimum formed during periods of higher flow veloc- tends northeast across the Rio Grande to datesof deposition.Yet there still remainsa ity which produced upper flow regime plane- Lamy, New Mexico, 87 mi (1.40km) from the slight possibility that it could have been de- bed conditions. Paleocurrent data derived stratotype.It appearsto extend north about posited during the Early Cretaceous. from the abundant crossbeds indicate a mean 65 mi (105km) to just south of Cuba, New Brookins (1980)also reported that the ru- easterly paleoflow direction, although local Mexico. The Jackpilehas been mapped bidium-strontium isotopic age for Jackpile variations occurred. The thin lenses of mud- northwest into the subsurfaceof the SanJuan clays contemporaneouswith uranium min- stone were deposited mostly in temporarily Basinto near ChacoCanvon bv Adams and + eralizationwas 113 7 Ma and that the age abandoned braid channels; manv of the de- Saucier(1981, pl. 3). for very early diageneticclays from the Di- posits were later ripped up to form mud- The thicknessof the increasesto + Jackpile kota was 93 8 Ma. Thesedata indicatethat stone clasts when the channel was reoccupied. the northeastfrom 100ft (30m) at the strato- the hiatus associated with the fackpile- The less common, thick lenses and beds of type to 200 ft (6I m) or more in a contem- Dakotaunconformity might be on the order mudstone may represent local overbank de- poraneously subsiding depression. Farther of 40 m.y. (approximatelyall of Early Cre- posits. north, it thins to approximately50 ft (18 m) taceoustime) and that uranium mineraliza- The thickest part of the Tackpile was de- in the outcrops near San Ysidro, New Mex- tion occurredduring the middle of this hiatus. posited in a contemporaneously subsiding, ico, but thickensto approximately130 ft (40 The 93 Ma minimum isotopicage for the Da- structural depression according to Schlee and m) along the Nacimiento front south of Cuba, kota agreesclosely with its paleontologically Moench (1961). Other fan complexes were New Mexico.The Jackpile wedges out in sev- determinedCenomanian age and with all of developed near Cuba and Lamy (Fig. 9), but eralplaces and variesin thicknesseast of the the time scalescited above. they are generally thinner. Local areas where Rio Grande. the is absent within its area of dis- Regionally,the crossbeddingof the Jack- ConnElarroN fackpile tribution may represent small interfluvial pile indicatesan easterlypaleocurrent direc- Significantuncertainties exist in lithostra- areas between braided-stream systems. tion, but at the stratotype the direction is jackpile tigraphic correlation of the Jackpile Sand- The proximal part of the alluvial-fan com- more northeasterly (56'). The was in stone the subsurfaceof the SanJuan Basin plex south and west of the stratotvpe has depositedby braided-streamsystems and on and the possible confusion of the Jackpile been removed by truncation along the basal the distal portions of alluvial-fancomplexes with the Burro Canyon Formation, a Lower Dakota unconformity. Therefore, the dis- in a fairly arid climate. Sourceareas were a (1955, Cretaceousunit. For example, Swift tance to the source area is conjectural. Moench rejuvenated upland south of Gallup, New 45)included p. all of what is now known as and Schlee (1,967,p.21) suggested that the Mexico, and the distant Mogollon High- and Burro Canyon from the Colo- lands. Jackpile source of the Jackpile was a rejuvenated area rado stateline to Mesa Gigantein his infor- south of Gallup, New Mexico, that was also mal DeadmansPeak formation. the source area of other Morrison sandstone The exactage of the is so poorly fackpile members. In this case the Jackpile would be known that little can be said regarding a more easterly alluvial-fan complex similar References chronostratigraphiccorrelation except that to, but smaller than, the alluvial-fan com- Adams, S. S., and Saucier, A. E., 1981, Geology and rec- beds of the same age as the Jackpile may plexes in the Salt Wash, Recapture, and occur in the much more extensive Brushy ognition aiteria for uraniferous humate deposits, Grants Westwater Canyon Members as mapped by uranium region, New Mexico: U.S Department of En- Basin Member where the Jackpile*as .,ot Craig et al. (1955) and discussed by Saucier ergy, National Uranium Resouce Evaluation GJBX-2(81), developed. 226pp. (1976) and Galloway (1979). The Mogollon Bell, T. E., 1981,A Jurassicclosed basin in the Monison Highlands of southwest New Mexico and GnNrsrs Formation (abs.): Geological Society of America, Ab- southeast and central Arizona also may have stracts with Programs, v. 13, no. 7, p. 406. Thereis broad agreementamong many au- contributed detritus derived from basement Brookins,D. G., 1980,Gemhronologic shrdies in the Grants belU ln Rautman, C. A. (compiler), Geology thors who have discussedthe provenance rocks that mixed with the closer sedimentary mineral and mineral technology of the Grants uranium region and depositionalsetting of the ]ackpileSand- source areas to form the Jackpile and other 1979:New Mexico Bureau of Mines and Mineral Re- stone that it is dominantly a braided-stream Morrison alluvial-fan complexes. sources,Memoir 38, pp. 52-58.

NetoMerico Geology Augrst 19M Craig, L. C., Holnes, C. N., Cadigan,R. A., Freeman, Moench, R. H., and Puffett, W P., 1,953a,Geologic map Saucier, A. E.,1.974, Stratigraphy and uranium potential V L., Mullens, T. E., and Weir, G. W., 1955,Stratiq- of the Mesa Gigante quadrangle, New Mexico: U.S. of the Buno Canyon Formation in the southern Chama raphy of the Morrison and relatedformations, Colo- Geological Survey, Geologic Quadrangle Map 212, 1, Basin, New Mexico: New Mexico Geological Sociefy, rado Plateau region-a preliminary report: U.S. sneet. Guidebook to 25th Field Conference, pp.27"I-217. GeologicalSurvey, Bulletin 1009-E, pp. 125-1.68. -, 1963b,Geologic map of the Arch Mesa quadran- -, 1975, Tectonic influence on uraniferous frends in Flesch, G. 4., 1.974,Stratigraphy and sedimentology of gle, New Mexico: U-S. Geological Suruey, Geologic the Late Jurassic Morrison Formation: New Mexico the Morrison Formation (Jurassic),Ojito Spring quad- Map 211, 1 sheet. Geological Society, Special Publication no. 6, pp. 151- Quadrangle 't57. rangle, Sandoval County, New Mexico-a preliminary Moench,R. H., and Schlee,J. 5., 1967,Geology and ura- discussion:New Mexico GeologicalSociety, Guidebook nium depositsof the Laguna district, New Mexico: U.S. Schlee, J. S., and Moench, R. H., 1961, Properties and to 25th Field Conference, pp. 185-195. GeologicalSurvey, ProfessionalPaper 51,9,1,77pp. genesis of "Jackpile" sandstone, Laguna, New Mex.ico; -, 1975,Stratigraphy, sedimentology, and environ- Nash, J. T., 1968,Uranium deposits in the Jackpilesand- ln Peterson, J. A., and Osmond, J. C. (eds.), Geomeiry ments of deposition of the Morrison (Upper Jurassic) stone, New Mexico: EconomicGeology, v. 63, pp.737- of sandstone bodies: American Association ol Petro- Formation, Oiito Spring quadrangle, SandovalCounty, 750. Ieum Geologists, pp. 134-1.50. New Mexico: Unpublished M.S. thesis, Universi$ of North American Commission on Stratigraphic Nomen- -, 1963a, Geologic map of the Moquino quadrangle, New Mexico,105 pp. clature, 1983, North American stratigraphic code: New Mexico: U.S. Geological Suwey, Geologic Quad- Freeman,V. L., and Hilpert, L. 5.,1956, Stratigraphyof American Association of Petroleum Geologists, Bulle- rangle Map 209, 1 sheet. the Morrison Formation in part of northwestern New tin, v.67, no. 5, pp. 841.-875. -, 1963b, Geologic map of the Mesita quadrangle, Mexico: U.S. Geological Survey, Bulletin 1030-J, pp. Odin, G. S. (ed.), 1982a,Numerical dating in shatigra- New Mexico: U.S. Geological Suruey, Geologic Quad- 309-334. phy: New York, Wiley and Sons, 1040pp. rangle Map 210, 1 sheet. John '1,975, Galloway, W. E.,1.979,Monison Formation of the Colo- Odin, G. S., 1982b,The Phanerozoictime scalerevisited: Siemers, C. T., King, N. R., and Mannhard, G. W., rado Plateau;ln Galloway,W. E., et al. (eds.),Depo- Episodes,v. 1.982,pp. 3-9. Upper Jurassic and Upper Cretaceous stratigraphy and sitional and ground-water flow systems in the Owen, D. E., 1,982,Conelation and paleoenvironments sedimentology----eastern San Juan Basin, New Mexico; exploration for uranium: Universiiy of Texas(Austin), of the Jackpilesandstone (Upper Jurassic)and inter- in Field trips to cenhal New Mexico-Rocky Mountain Bureau of Economic Geology, pp.214-228. tongued Dakota Sandstone-Lower Mancos Shale (Up- Section: American Association of Petroleum Geologists Harland,W. B., Cox, A. V, Llewellyn,P. G., Pickton,C. per Cretaceous)in west-central New Mexico: New Mexico and Society of Economic Paleontologists and Mineral- ;r A. G., Smith, A. G., and Walters,R., 1982,A geologic Ceological Societv, Guidebook to 33rd Field Confer- ogists, pp. 1-98. time scale: Cambridge, U.K., Cambridge University ence, pp. 267270. Swift, E. R., 7956, Study of the Monison Formation and Press,131 pp. Owen, D. E., and Siemers, C. T., 7977, Lithologic correlated strata, north-central New Mexico: Unpublished Kozusko, R. G., and Saucier,A. E., 1980, The Bernabe relation of the Dakota Sandstone and adjacent units M.S. thesis, University of New Mexico, 79 pp. Montaflo uranium deposit, Sandoval County; ln Raut- along the eastern flank of the San Juan Basin, New van Hinte, J. E., 1,976a,A Jurassic time scale: American man, C. A. (compiler),Geology and mineral technology Mexico: New Mexico Geological Society, Guidebook to Association of Petroleum Geologists, Bulletin, v. 60, no. of the Grantsuranium region 1979:New Mexico Bureau 28ih Field Conference, pp. 179-1.83. 4, pp. 489-497. of Mines and Mineral Resources,Memoir 38, pp.262- Palmer, A. R., 1983, The decade of North American geol- -, 1976b, A Cretaceous time scale: American Asso- 268. ogy, 1983 geologic time scale: Geological Society o( ciation of Petroleum Geologists, Bulletin, v. 60, no. 4, Lee, M. J., and Brookins, D. G., 1978, Rubidium-stron- America, Geology, v. 11, pp.503-504. pp.498-516. tiurn minimurn ages of sedimentation, uranium min- Santos, E. 5., 1975, Lithology and uranium potential of Woodward, L. A., andSchumacher, O. L., 1973,Morrison eralization, and provenance, Morrison Fomation (Upper Jurassic formations in the San Ysidro-Cuba and Majors Fomation of southeastern San Juan Basin, New Mex- Jurassic),Grants mineral belt, New Mexico: American Ranch areas, northwestern New Mexico: U.S. Geolog- ico: New Mexico Bureau of Mines and Mineral Re- Associationof PetroleumGeologists, Bulletin, v. 52, no. ical Suruey, Bulletin 1329, 22 pp. sources, Circular 129,8 pp. n 9, pp.7673-1.683. Lupe, Robert, 1983,Stratigraphic sections of subsurface MINING REGISTRATIONS rocks in ihe San Juan Basin, New Mexico, Col- Jurassic (ocToBER APRIL 76,^1984) orado, Utah, and Arizona: U.S. Geological Survey, Oil 25, 1983THROUGH and Gas InvestigationsChart 118,2 sheets. StateMine Inspector 2340Menaul N.E. Albuquerque,NM 87107 Maxwell, C. H., 1982,Mesozoic stratigraphy of the La- Date and guna-Grants region: New Mexico Geological Society, operation Operators and owners Location Guidebook to 33rd Field Conference, pp. 261,266. McBride, E. F., 1963,A classification of common sand- 10-25-83 Operator-Garrett Mine, D'Appolonia Consulting Engi- McKinley Co.; sec. 22, T. 1.5N., R. 18 W.; stones:Journal of SedimentaryPeftology, v.33, pp. 664- clay neers,2340 Alamo SE,Suite 306,Albuquerque, NM 87106; Gallup mining district; private land; drift- 669. Gen. Mgr.-Dr. A. K. Kuhn, sameaddress, phone: 842- abandoned; no material to be mined; ex- McLemore,V T., 1982,Uranium in the Albuquerque area, 0835;Person in charg-Bruce W. Hassinger,same ad- isting adits to be opened in order to in- New Meico: New Mexico Geological Society, Guide- dressand phone;Gen. Supt.-Jeny Farris,PO. Box587, vestigate subsidence problems; directions book to 33rd Field Conference,pp. 305-311. Granrs.NM 87020; to mine: immediately east of NM-32, 0.5 Moench, R. H., 1953,Geologic map of the Laguna quad- Property owner-Frank J. Burke, P.O. Box 278, CaIIup, mi south of the intersection of NM-32 and rangle, New Mexico: U.S. GeologicalSurvey, Geologic NM 87301 NM-40 in Gallup, NM Quadrangle Map 208, 1 sheet. 10_25_83 Operator-Ambrosia Lake Mill, Quivera Mining Co., PO. McKinley Co.; sec. 31, T. 1,4N., R. 9 W.; mul Box218, Grants, NM 87020;Supi.-Charley Stanley,same Grants mining district; private land; ores address;Gen. Mgr.-Arthur Gebeau,same address; Other milled-uranium; cu5tom milling; capac- official-Rob Luke, Rod Tregembo, Billy Stevens,Kerr- ity of mill-7,000 tons per day; directions McGee Center, Oklahoma C\ly, OK 73"125 to mill: approximately 21 mi north of WyomingGeological Grants, NM on NM-509 spur Association 12)0-83 Operator-U.S. Treasury,St. Cloud Mining Co., PO. Box Sierra Co.; sec. 25, T. 11 S., R. 9 W.; private gold, 1570, Truth or Consequences,NM 87901, phone: 244- land; directions to mine: 12 mi SW of Win- Fallfield conference and symposium silver 5215;Gen. Mgr.-P S. Freeman,1006 Kopra St., Truth ston, NM, past St. Cloud mill, follow signs TheWyoming Geological Association will or Consequences,NM, 87901, phone: 894-7739; Gen. Supt.-James Ray Nations, General Delivery, Winston, hold its annual field conference and sym- NM, phone: 894-7495;Other official-Walter Palass,Ad- posium entitled The Permianond Penisyl- min. Mgr., Box 1,670,Truth or Consequences,NM 87901; aannngeology of WyomingSeptember 23-26, Property owner-The Goldfield Corp., P. O. Box 1899, 7984,at the Hilton Inn, Casper,Wyoming. Melbourne, FL32907 The tentative scheduleis: Bighoms field trip 72-20-83 Operator-St. CloudMill, The St.Cloud Mining Co.,P O. Siena Co.; sec. 4, T. 12 S., R. 8 W.; Chlo- and eveningicebreaker on Sunday,Septem- mill Box 1570,Truth or Consequences,NM 87901,phone: (505) ride mining district; private land; ore ber 23;symposium on Monday, September 7M-5215; Supt.-John Gilson, sameaddress and phone; milled-copper, silver, and gold; capacity 24;and Hartville Uplift and Black Hills field Gen. Mgr.-Patrick Freeman, same address and phone; of mill-400 tons per day; directions to trip (overnightin Newcastle,Wyoming) on Other official-Walter Palass,Admin. Mgr., sameaddress mill: 10 mi SW of Winston Tuesdayand Wednesday,September 25-26. and phone: Someof the subiectsto be discussedat the Property owner-The Goldfield Corp., PO. Box 1899, symposiumare the CooseEgg saltsand the Melbourne, FL 32901 Tensleep,Casper, Leo, and MinnelusaFor- 1-18-84 Operator-Black Silver Venture, Gold-Silver Exploration, Siena Co.; sec, 13, T. 15 S., R. 9 W.; Kings- mations.For further information contactPaul silver Inc., 631 Broadway, Truth or Consequences,NM 87901; ton mining district; federal land; direc- Trump, % Mitchell Energy Corp., 1670 Gen. Mgr.-Dan Medley, 531Broadway, phone:89421.21.; tions to mine: turn north on forest road Broadway, Suite 3200, Denver, CO 80202 Personin charge-Arthur Misquez, 1315Caballo Rd., Truth 157 halfway between Hillsboro and Kings- phone: 894-3943; Gen. ton, go 9.5 mi to mine (303-867-2226\ or Consequences, NM 87901, or Alec Steele, % Marathon Supt.-A. D. Richins,P.O. Box 155, Hillsboro, NM 88042, Oil Co., PO. Box 2659, Casper, WY 82602 phone: 895-5594; (307-577-1555\. Propertyowner-Black SilverVenture, 531 Broadway, Truth or Conseouences,NM 87901 continued on page 55

August 1984 Nan Mexico Geology