1C. 352
GEOLOGICAL SURVEY CIRCULAR 352
PRELIMINARY REPORT ON URANIUM IN THE GAS HILLS AREA, FREMONT AND NATRONA COUNTIES WYOMING
This report concerns work done on behalf of the U. S. Atomic Energy Commission and is published with the permission of the Commission. UNITED STATES DEPARTMENT OF THE INTERIOR Douglas McKay, Secretary
GEOLOGICAL SURVEY W. E. Wrather, Director
GEOLOGICAL SURVEY CIRCULAR 352
PRELIMINARY REPORT ON URANIUM IN THE GAS HILLS AREA FREMONTAND NATRONA COUNTIES, WYOMING
By J. D. Love
This report concerns work done on behalf of the U. 8. Atomic Energy Commission and is published with the permission of the Commission.
Washington, D. C., 1954 Free on application to the Geological Survey, Walhington 25, D. C. EXPLANATION
R.89 W. Alluvium Landslide debris Miocene rocks White River formation Upper and middle Eocene rocks Middle and lower Eocene rocks Wind River formation Cody shale Frontier formation Mowry and Thermopolis shales Cleverly and Morrison formations Jurassic rocks Chugwater formation Phosphoria formation Tensleep sandstone ond Amsden f m. Madison limestone Cambrian rocks
Igneous rocks Tida Upper and middle Eocene intrusive rocks p u Pre-Cambrian rocks
(?) Locality at which samples were taken L7 WYOMING
Gas Hills area
R. 91 W. R. 90 W. R. 89 W.
Geology from published and unpublished maps by J. D. Love, J. L. Weitz, F. B. Van Houten, and C.J. Hares
I 5 Miles I
Figure 1. Geologic map of Gas Hills area, central Wyoming. PRELIMINARY REPORT ON URANIUM IN THE GAS HILLS AREA FREMONT AND NATRONA COUNTIES, WYOMING
By J. D. Love
CONTENTS Page Page
Abstract...... 1 Uranium occurrences Continued Introduction...... 1 Description of localities...... 4 Geography...... 2 Origin of uranium in the Gas Hills area...... 9 Geology...... 2 Possibility of industrial health hazard ...... 10 Stratigraphy ...... 2 Selected references ...... 10 Uranium occurrences...... 4 Unpublished reports ...... 11
ILLUSTRATIONS Page Figure 1. Geologic map of Gas Hills area, central Wyoming...... ii 2. Uraniferous sandstone in Wind River formation at locality 5...... 7 3. Wind River formation at locality 7 ...... 8 TABLES Page Table 1. Analyses of samples...... 6 2. Analyses of water...... 10
ABSTRACT Several uranium minerals are present. The dom inant one is meta-autunite, Ca(UO2) 2(PO4)2» 2|-6iH2O, Uranium minerals have been discovered in the a pale greenish-yellow highly fluorescent mineral. In , Wind River formation of early Eocene age, in strata some samples, arsenic appears to be more abundant of middle and late Eocene age, and in the Thermopolis than phosphorus and the mineral may be uranospinite, shale of Early Cretaceous age in the Gas Hills area of Ca(UO2) 2{AsO4)2 8-12H2O. A greenish-yellow non- central Wyoming. Localities of uranium mineraliza fluorescent mineral is present in several localities. tion were found independently by prospectors and by X-ray studies indicate that it is a calcium uranyl phos geologists of the U. S. Geological Survey. Geologists phate, possibly a new mineral. of the Atomic Energy Commission have made evalua tion studies of many of the occurrences in the area as The writer believes that the source of the urani well as reconnaissance that led to new discoveries. um may have been tuff in the White River formation (Oligocene) or younger Tertiary rocks that once over The uranium is concentrated in clayey and con lay this portion of the Wind River Basin. The avail glomeratic sandstone and in carbonaceous shale. Sev able evidence suggests that the uranium was carried eral selected samples of sandstones in the Wind River downward and laterally along sandstone aquifers in the formation, taken for mineral determination, contain middle Eocene sequence and Wind River formation and more than 10 percent uranium. The highest analysis was concentrated in favorable host rocks. of a channel sample is 6.72 percent uranium from a 1-foot section of conglomeratic sandstone in the Wind River formation. The highest analysis of a carbona INTRODUCTION ceous shale in this formation is 0.062 percent uranium. A sample of sandstone from the sequence of middle and The Gas Hills area is located in eastern Fremont late Eocene age contained 0.078 percent uranium. A and western Natrona Counties, central Wyoming (fig. 1). sample from the Thermopolis shale directly overlain A reconnaissance examination of some of the rocks in by the Wind River formation contained 0.041 percent the area was made with a Geiger counter in 1951 while a uranium. Geological Survey field party was engaged in oil and gas investigations there. A water sample (no. 1, table 2) face rises 300 to 800 feet above the Wind -River was collected for analysis by the Oak Ridge lab Basin to the north. The lip of the escarpment oratory of the Atomic Energy Commission. The is essentially the drainage divide between north water sample and the rocks showed small amounts ward-flowing tributaries of the Wind River having of uranium. Data obtained on the geologic occur high gradients and southward-flowing tributaries of rence of uranium during 1952 and 1953 in the the Sweetwater River having low gradients. Pumpkin Buttes (Love, 1952) and Miller Hill (Love, 1953) areas suggested that the Gas Hills area warranted Although the Gas Hills area has no towns a detailed scintillation counter survey. This sur and no improved roads most of the area is vey was begun on September 27, 1953, Abnor accessible by car. Moneta is the nearest post mally high background radiation was noted through office, 25 miles to the north on U. S. High out many square miles and rock samples were way 20. The nearest railroad station is at collected for analysis from several of the locali Lysite, on the Chicago, Burlington, and Quincy ties shown in figure 1. However, the writer was Railroad, 34 miles to the north. The area has unaware at that time that Mr. Neil McNeice, of no permanent residents. Sheep and cattle ranch Riverton, Wyo., had already discovered radio ing is the only industry. Vegetation is sparse active sandstone in sec. 22, T. 33 N., R. 90 W. and bedrock is moderately well exposed. (loc. 7) on September 9, 1953. Early in October, Mr. McNeice informed geologists of the Atomic Energy Commission of the location of his discov GEOLOGY ery claim and they began detailed studies of the uranium deposits in the area. N. M. Denson and The Gas Hills are hogbacks of steeply dipping the writer likewise examined and sampled many Mowry shale and of sandstone in the Cloverly forma of the localities in October. tion on the north and west flanks of the Dutton Basin anticline. This anticline branches off the Granite Mountains to the south and plunges northwestward This discovery received widespread publicity into the Wind River Basin. Folding occurred near which resulted in an intensive search for uranium the close of Paleocene time and erosion developed throughout the general region and several hundred the present topography on the pre-Eocene rocks. claims were staked in the Gas Hills area. The The overlying Wind River formation and the suc Atomic Energy Commission is continuing evalua ceeding younger Tertiary strata were then de tion studies of occurrences in the area and is posited until the structural basin between the assisting in the physical exploration and develop Granite Mountains to the south and Owl Creek ment of individual deposits. The Geological Sur Mountains to the north was filled with nearly horizon vey is making further studies of the relation of tal Eocene, Oligocene, Miocene, and possibly Pliocene uranium occurrences to geologic features. rocks, at least to the level of the present crest of the Beaver Divide escarpment. Pliocene and Pleistocene C. C. Towle, chief, Denver Exploration Branch uplift started the present erosion cycle, and as the of the Atomic Energy Commission, read the manu face of the Beaver Divide escarpment moved southward, script and contributed valuable suggestions. L. F. Rader the Gas Hills and other areas of older resistant folded and his associates made the chemical and radio- rocks along the south margin of the Wind River Basin metric analyses. Mrs. Alice D. Weeks and L. B. Riley were exhumed. Remnants of lower and middle Eocene identified the uranium minerals. The reconnais rocks are present in steep pre-Eocene valleys be sance examination of the Gas Hills area was tween the hogbacks of Mesozoic rocks. These valleys made on behalf of the Division of Raw Materials extend generally south and probably continue for some of the U. S. Atomic Energy Commission. distance beneath the Tertiary strata that form the Beaver DMde. This relationship may have a bearing Stratigraphic and structural studies of the on the orientation and distribution of uranium deposits, Wind River Basin, including the Gas Hills, have and is discussed in more detail in the description of been in progress by the U. S. Geological Survey individual deposits. About 10 miles southeast of the since 1944, as part of a regional oil and gas Gas Hills, in and south of the Rattlesnake Hills is a investigations program. The results of many of volcanic field of middle and late Eocene age, the rocks these studies have been published and are listed of which were intruded through pre-Cambrian, Paleo in the selected bibliography. The Gas Hills area zoic, and Mesozoic rocks. These vents furnished much is included in published topographic maps, scale, of the volcanic debris in the middle and upper Eocene 1:24,000, of the Puddle Springs, Coyote Springs, rocks in the Gas Hills area. Gas Hills, and Ervay Basin SW quadrangles, 7. 5-minute series, with 20-foot contour interval. STRATIGRAPHY
GEOGRAPHY Detailed descriptions and thicknesses of the rock units in the Gas Hills area are summarized below: The Gas Hills area lies along the southern margin of the Wind River Basin. The hills to Alluvium: Gravel, sand, and clay derived from Tertiary which the name is applied are steep hogbacks of rocks along the Beaver Divide escarpment and de Mesozoic rocks on the north and west flanks of posited along stream "bottoms. the Dutton Basin anticline which projects north Landslide debris: Claystone and sandstone masses of ward from the Beaver Divide. The Beaver. Divide Eocene and Oligocene rocks that nave "broken loose escarpment marks the southern boundary of the and moved north down the slopes of the Beaver area and trends generally east. The steep north Divide. Miocene rocks: Sandstone, gray and white, soft, tuff Wind River formation (lower Eocene): This is an ex aceous; containing lenses of conglomerate near the tremely variable sequence of rocks that was de base and pumicite in the upper part. Thickness posited on a rugged topography cut in folded and ranges from a feather edge to 100 feet. eroded Paleozoic and Mesozoic rocks. In the north western part of the area the basal strata are White River formation (Oligocene): Tuff, light-gray, brightly variegated claystones and clayey sand limy, biotitic, vitric, and tuffaceous mudstone. stones. In the southeastern part of the area the Basal bed is 50 feet thick. The upper 200 to basal beds are yellow to gray arkosic sandstone 300 feet is grayish-orange to yellowish-gray sandy and granitic conglomerate. Higher in the sequence mudstone with some layers of gray vitric tuff and are lenticular sandstones, some of which are highly thin lenses of conglomerate. South of Coyote ferruginous. The sandstones contain many of the Spring, this sequence is, in part, soft plastic uranium deposits in this area. Thin carbonaceous tuffaceous variegated claystone. The formation in shales and coals likewise contain some concentra the Gas Hills area is of Chadron age. The thick tions of uranium. The formation ranges in thick ness ranges from a feather edge to more than ness from a feather edge to more than -300 feet. It-50 feet. Cody shale (Upper Cretaceous): Shale, gray, soft; sandy Upper and middle Eocene volcanic rocks: Dacite, light- in the upper part. The Cody shale is more than gray to dark-gray; hornblende latite, sodic 3,000 feet thick and underlies extensive areas of trachyte, andesite, and alkalic rocks. They are the Wind River formation north and west of the Gas intruded through pre-Cambrian, Paleozoic, and Hills. Because of its low dips, extent, and imper Mesozoic rocks in the Rattlesnake Hills and fur meability, the Cody shale was of major significance nished boulders and ash that are incorporated in in confining some of the ground water containing ura the upper and middle Eocene sedimentary sequence. nium within the overlying Wind River formation. The volcanic rocks are overlain by Oligocene and Miocene strata. Frontier formation (Upper Cretaceous): Sandstone, chiefly gray, soft, lenticular; interbedded with Upper and middle Eocene sedimentary rocks: Six units gray to black soft shale. White tuff and bentonite are recognizable along the Beaver Divide escarp beds mark base of formation, which is about 580 feet ment. (Van Houten, F. B., personal communication.) thick. 6. Conglomerate, volcanic, very coarse grained, Mowry and Thermopolis shales (Lower Cretaceous): The more than li-O feet thick. Crops out in a Mowry shale is dark-gray hard siliceous; containing massive ledge at the top of the formation and abundant fish scales; weathers silvery gray and forms the lip of the Beaver Divide escarpment crops out in ridges forming the outer portion of the at some places. Gas Hills. The shale is about It-70 feet thick and is underlain by the Thermopolis shale containing the 5. Sandstone, dark-yellowish-gray, tuffaceous; Muddy sandstone member at the top. The Muddy sand and volcanic conglomerate consisting chiefly stone member is 32 feet thick and consists of gray of andesite porphyry. Uraniferous sandstone fine-grained sandstone and siltstone interbedded at locality 9 is believed to be a northward with black shale. It IB underlain by 150 feet of extension of this unit. soft black fissile shale. This shale contains one of the uranium deposits in this area. It-. Tuff, biotitic; lapilli tuff, and cobbles of volcanic rocks. Bed is 1*5 feet thick. Cleverly and Morrison formations (Lower Cretaceous and Upper Jurassic): Sandstone, chiefly ferruginous, 3. Sandstone, tuffaceous; sandy mudstone, and con 80 feet thick; and conglomerate which forms the glomerate containing pebbles and cobbles of highest inner ridges of the Gas Hills, 200 feet sodic trachyte pumice, tuff, and lava. Bed is thick. The middle and lower part of the sequence 90 feet thick. Giant boulders of pre-Cambrian is interbedded variegated claystone and sandstone. gneiss and granite are present in lower 25 feet of the unit. Jurassic rocks: Sundance formation, sandstone, gray and green shale; 2^0 feet thick; underlain by gray 2. Mudstone, soft; and arkosic sandstone contain and white Nugget sandstone, 170 feet thick. ing very little tuffaceous debris. The upper most bed is a dredge-forming arkose and con Chugwater formation (Triassic): Only the upper part of glomerate containing pebbles of sodic trachyte this formation is exposed. The Popo Agie member lava. at the top is 300 feet thick and consists of red shale, red sandstone and siltstone, and thin sparse 1. Mudstone, green to olive, ledge-forming; con limestone pellet conglomerates. It is underlain tains a thin bed of acidic tuff that probably by the Alcova limestone member, a gray thin-bedded records the initial volcanic outburst in the hard limestone 5 feet thick. The underlying Rattlesnake Hills volcanic field. Thickness Red Peak member is a red sandstone, siltstone, and at base is 25-30 feet. shale sequence about 700 feet thick. Middle and lower Eocene rocks: For a distance of 5 miles Phosphoria formation (Permian): Dolomite, interbedded,| or more north of the Beaver Divide and east of the cherty and red shale containing thin anhydrite beds. Gas Hills, the Wind River formation is overlain by This formation is about 325 feet thick. rocks of middle Eocene age. The formations look very much alike and have not as yet been mapped Tensleep sandstone and Amsden formation (Pennsylvania^): separately. Both sequences contain yellow soft Tensleep sandstone, white, hard, fine-grained, sandstone, lenses of ferruginous brown sandstone, about 200 feet thick; underlain by the Amsden and conglomerate. The chief lithologic difference formation, consisting of about 200 feet of red and is that conglomerate in the middle Eocene sequence green shale, cherty dolomite, and a basal ferruginous contains abundant boulders of andesite derived from sandstone about 60 feet thick. the Rattlesnake Hills, whereas the conglomerate in the Wind River formation contains no locally de Madison limestone (Mississippian): Limestone, blue-gray, rived volcanic rock fragments. The sequence ranges massive to thick-bedded, cherty; containing some in thickness from a feather edge to more than dolomite near the base. This formation is 300 feet 200 feet. thick. Unit Lithologic character Thickness Cambrian rocks: Sandstone, chiefly arkosic red and (feet) brown in the lower half; green and gray sandy no. and silty shale, and sparse thin limestones in 6 Sandstone, pale green, arkosic, coarse 20 the upper half. Thickness is about 800 feet. grained, finely conglomeratic in upper 10 feet; 1 3-foot granite boulder pres Pre-Cambrian rocks: Granite, chiefly red and brown, ent but average size is less than granite gneiss, and black schist cut by quartz 2 inches; no volcanic rock fragments pegmatite dikes. observed; most fragments are of gray granite. URANIUM OCCURRENCES 5 Shale, dark brown, carbonaceous, contains .5 O.OJ1 percent equivalent uranium and 0.021 percent uranium; contains flattened The purpose of this report is to present plant and tree fragments; forms top of geologic data on several types of uranium depos ledge. its in the Gas Hills area rather than to give the complete description of each locality where k Shale, black, coaly, interbedded with thin 1.5 radioactivity or uranium minerals occur. There coal partings. fore, some localities are described that are of 3 Shale, brown and gray, carbonaceous, platy; 2.2 geologic significance but in which there is no contains leaf impressions. commercial-grade uranium ore, whereas other 2 Claystone, pale green, plastic, soft. 5 localities where rocks contain more than 0.1 per cent uranium are omitted because the geologic 1 Sandstone, pale brownish green, soft, 15 coarse-grained, interbedded with arkose setting is similar to that of one already described and fine-grained conglomerate with small in this report. The Atomic Energy Commission black chert and granite pebbles. has been actively engaged in physical exploration throughout the area, beginning in October, 1953, In the general vicinity of this locality there with the objective of evaluating tonnage and grade are many places of higher radioactivity, and of many of the deposits. Therefore, the Geolog uranium minerals occur in some of them, chiefly ical Survey has made no attempt to estimate ton in sandstone, above and below the carbonaceous nage and grade in any locality in the Gas Hills shale. Although this shale is of no commercial area. value, carbonaceous shales with readily detect able uranium content probably can be useful Uranium occurs in the Thermopolis shale of guides in locating areas of possible uranium Early Cretaceous age, in the Wind River forma deposits. These shales are conspicuous and tion, and in middle Eocene rocks. Occurrences can be easily checked. Where such shales are of uranium minerals are most abundant in soft underlain or overlain by porous sandstones, if sandstones in the Wind River formation. One con any uranium is in the vicinity, some of it will spicuous feature of the area is the background of probably be concentrated in the carbonaceous radioactivity. It is commonly more than twice as shale. high on outcrops of the Wind River formation and middle Eocene rocks than on adjacent outcrops of the Locality 3 (SWiSEiSWi- sec. 1. T. 32 N.. Cody shale. R. 91 W). Meta-autunite is disseminated in sandstone of the Wind River formation at lo cality 3. The relationship of the uraniferous Description of localities sandstone to overlying and underlying rocks of the Wind River formation can be observed. Locality 1 (SWjSEJsec. 24, T. 33N.. R. 91 W). - Localities 3, 4, and 5 are stratigraphically The site of this locality is a water well at the lower than locality 2. The rocks at locality 3 Puddle Springs ranch, and is reported to be dip about 1° SW. The stratigraphic section 80 feet deep. The water issues from an arkosic shown below was measured on the west-facing sandstone in the lower part of the Wind River slope just west of the uraniferous deposit. Unit formation, A water sample obtained by hand 1 is at the base of the section. pumping contained 0.012 ppm uranium. Thickness Unit Lithologic character Locality 2 (C SWJ sec. 32. T. 33N.. R. 90 W). - no. (feet) A radioactive carbonaceous shale is the site of Sandstone, pale green, clayey, in lower locality 2. It is stratigraphically above the ura- 5 feet, grading up to ledge-forming niferous sandstone beds at localities 3, 4, and 5. coarse-grained gray sandstone, and then to granite boulder conglomerate. Locality 2 is considered significant because (a) it The top of the unit is the top of the is one of many stratigraphic zones in which ura knob just west of the uranium locality. nium occurs in the Wind River formation, and The uranium is concentrated in a pale (b) it shows how much uranium is present in car green and brown clayey sandstone about bonaceous rocks where they are overlain by a 7 feet above the base of the unit where soft porous sandstone. By comparison, another readings are locally 2.5 mr/hr. A carbonaceous shale, north of locality 1, is over trench sample of 1 foot of beds con tains 0.13 percent equivalent uranium lain and underlain by variegated claystone and and 0.050 percent uranium. Overlying contains very little radioactivity. A preliminary strata of the Wind River formation are reconnaissance section including the carbonaceous eroded away so there is no way to shale at locality 2, from top to bottom, is shown determine the total thickness of the in the following section: formation here. Unit Lithologic character Thickness sampled, a trench only 1 foot, deep was dug. This no. (feet) trench sample contained 0.13 per cent equivalent ura nium and 0.050 percent uranium (table 1). The bright Sandstone, dark brown, hard, forming 1 greenish-yellow highly fluorescent mineral at this ledge, lenticular; appears at slightly different levels in outcrops to north locality is meta-autunite which is disseminated through east and southwest; locally gives read the soft sandstone and in places is concentrated in small ings of 1.5 mr/hr. green pods. Sandstone, pale green, interbedded with 18 Locality 4 (NE4-NEiNWi sec. 12. T. 32 N.. conglomerate of granite fragments, very R. 91 W). This locality yielded some of the highest soft; sandstone is very coarse grained radioactivity measurements made in the Gas Hills area. but has a greenish clay matrix in part; roundstones are chiefly of gray granite A scintillation counter read 8 mr/hr on the surface as much as 6 inches in diameter but and a trench sample of the uppermost 1 foot of averaging 1 to 2 inches. sandstone contains 1.2 percent equivalent uranium and 1.87 percent uranium. The uranium is con Sandstone and conglomerate, greenish- 10 centrated in a very light gray slightly clayey sand brown; matrix is so soft it is almost stone at about the same horizon as that at locality 3. unlithified; rock fragments are chiefly The thickness of the uraniferous part of the sand gray granite; gives readings of 0.2 to 0.25 mr/hr. stone is not known, but 50 feet to the southwest on the point of the spur along which the sandstone Conglomerate and sandstone, gray to brown, 6 crops out, a ledge 5 feet thick is moderately forming ledges; middle part is a mass radioactive. Meta-autunite, possible uranospinite, of boulders as much as 2 feet in dia Ca(UO2)2(AsO4 ) 2 .8-12H2 O, and an unknown greenish- meter jumbled together; almost all are yellow nonfluorescent mineral are disseminated in coarse grained gray granite but some are the coarse-grained sandstone near the surface. black chert from Paleozoic rocks; sand stone is coarse grained and lenti- Readings of more than 1 mr/hr were obtained for ular; gives readings of 0.1 to a distance of 20 feet on each side of the spot that 0.15 mr/hr. was sampled and lower readings for another 50 feet beyond that. Sandstone, pale greenish brown, soft, 66 with clay matrix, interbedded with Locality 5 (SEiNEiNWi sec. 12. T. 32 N.. brownish-green plastic claystone in R. 91 W). Abundant meta-autunite, uranospinite(?), which are many sand grains, in lower half of unit; upper half is largely very and possibly the unknown nonfluorescent greenish- coarse grained greenish-brown soft yellow uranium mineral are disseminated in a arkosic sandstone. coarse-grained conglomeratic sandstone (fig. 2) at locality 5. A trench sample of 1 foot of Sandstone, gray, hard, lenticular; forms 0-12 rock at the surface contains 0.58 percent equiv ledges that appear intermittently alent uranium and 0.25 percent uranium. At a in outcrops to south at this same depth of 5 feet a 1-foot channel sample contains position; very coarse grained and pebbly; most pebbles are of granite as much as 0.19 percent equivalent uranium and 0.065 per 1 inch in diameter but commonly less cent uranium. The deposit is in a very soft than 1/10 inch; gives reading of ferruginous conglomeratic sandstone about 50 feet 0.06 mr/hr. stratigraphically below the uraniferous sandstone at locality 4. The sandstone is brown, coarse Sandstone, greenish gray, coarse-grained; 22 grained, and contains rounded pebbles of granite . with clay matrix; less clayey toward as much as 2 inches in diameter. A scintillation top; gives readings of 0.06 to counter reads 8 mr/hr at the surface point 0.07 mr/hr. sampled, and indicates a high level of radio Claystone, "brownish green, soft, plastic, 1? activity for 20 feet in all directions. About very sandy; grades up to coarse-grained 400 feet to the southeast another occurrence of arkosic sandstone with a clay matrix; high radioactivity occurs in a similar sandstone. in upper 5 feet and particularly at top are abundant groups of aragonite crystals as much as 2 feet in diameter; gives Locality 6 (SEiSEjNEi sec. 14. T. 32 N.. reading of 0.05 mr/hr. R. 91 W).- The site of locality 6 fs Coyote Spring which issues from the basal conglomeratic Total thickness of measured part of Wind 187-199 sandstone of the Wind River formation where it * River formation. overlaps northward onto a pre-Wind River hill of Mowry shale. The spring flows a 1-inch pipe full of clear cold water which contains 0.090 ppm The underlying rocks are not exposed but the base of uranium. the section probably is not more than 50 to 75 feet above the contact with Cody shale. Locality 7 (fig. 3) (NEjSEj- sec. 22, T. 33 N.. R. 90 W). The site of locality 7 is in the Gas The area within 50 feet of the spot sampled Hills area where Neil McNeice first discovered for analysis (fig. 2) is markedly radioactive. To radioactive sandstone. The uranium is in the the northwest, where the section was measured, Wind River formation which overlies the Cody the radioactivity appears to extend through a strati- shale, strikes east, and dips 3° S. Exposures graphic interval of 7 feet of sandstone, but at the spot of the Wind River formation begin about 50 feet Table 1. Analyses of samples from Gas Hills area1 Laboratory eU U V205 Se As Locality Location (fig. l), lithology, and formation sample no. (percent) (percent) (percent) (ppm) (ppm)
99202 2 0.051 0.021 0.06 10 150 C SW£ sec. 52, T. 33 N. , R. 90 W. Channel sample of 6 in. of carbonaceous shale in Wind River formation. 99201 3 .13 .050 .06 20 50 SW£SE£SW£ sec. 1, T. 32 N., R. 91 W. Channel sample of 1 ft of sandstone in Wind River formation; me. ta-aut unite present. 99204 4 1.2 1.87 .06 50 750 NE£NE£NW£ sec. 12, T. 32 N., R. 91 W. Channel sample of 1 ft of sandstone in Wind River formation; meta-autunite, possi bly uranospinite, and an unidentified nonfluorescent uranium mineral present. 99205 5 .58 .25 .06 2 400 SE£NE£NW£ sec. 12, T. 32 N., R. 91 W. Channel sample of 1 ft of conglomeratic sandstone in Wind River formation; meta- autunite, possibly uranospinite, and an unidentified non- fluorescent uranium mineral present. 206975 5 .19 .065 .1 Channel sample of 1 ft of sandstone 5 ft below sample 99205. 99206 7 .21 .24 .06 50 1000 NE^SE^ sec. 22, T. 33 N., R. 90 W. Channel sample of 1 ft of sandstone in Wind River formation. 99207 7 .047 .014 .05 12 350 36 ft SW of 99206. Channel sample of 1 ft of sandstone in (AEG sample Wind River formation. loc. EWS-6). 99209 7 .19 .24 .06 40 200 126 ft SW of 99207. Channel sample of 1 ft of sandstone in (AEG sample Wind River formation. loc. EWS-2). 99208 7 .08 .096 .06 80 400 8l ft SW of 99209. Channel sample of 1 ft of sandstone in (AEG sample Wind River formation. loc. EWS-1). 200929 7 .52 .95 Pebble of basic igneous rock from uraniferous sandstone in Wind River formation. 99210 8 .039 .041 .05 3 50 NE£SEjLSW£ sec. 23, T. 33 N., R. 90 W. Channel sample of 1 ft (AEG sample of black Thermopolis shale. loc. EWS-8). 99212 9 .06 .078 .08 2 50 NW£HE£SW£ sec. 17, T. 33 N., R. 89 W. Ferruginous sandstone in middle Eocene sequence. 58068 10 .015 .018 C SE£-NE£ sec. 27, T. 33 N., R. 89 W. Carbonaceous shale in Wind River formation. 99211 10 .078 .062 .12 15 50 30 ft southwest of sample 58068, channel 1 ft carbonaceous shale in Wind River formation. 58067 10 .003 .003 SE£SEjLNE£ sec. 27, T. 33 N., R. 89 W. Tuff in middle and upper Eocene rocks above Wind River formation. 20697^ 4.7 6.72 .1 XNWNW ^wnlc?U' j^lvn^:L l\niJ-i- oc5U.«*f»r» f*ivJ, TX . J7^~*& 1"TJ . , -TVT? * QOy\J UW L/llcLllilC/J.PVmnrxal ooul^ij.c/<*amnT e* (JJ.of JL~\ J.ft- U of conglomeratic sandstone in Wind River formation.
1 Samples analyzed by the U. 5. Geological Surrey. Analysts: Furman, Dufour, Meadows, Mountjoy, and Vilson.
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Figure 2. Uraniferous sandstone in Wind River formation at locality 5. Sample of top foot contains 0. 25 percent uranium and from the bottom foot 0.65 percent uranium. above the Cody shale. A generalized estimated sec section, contained 0.047 percent equivalent ura tion is shown below, from top to bottom (fig. 3): nium and 0.014 percent uranium. About 125 feet farther southwest, a 1-foot channel sample of Unit Estimated sandstone at the same horizon in AEC pit to EWS-2, no. Lithologic character thickness contained 0.19 percent equivalent uranium and 0. 24 per (feet) cent uranium. Another 1-foot channel sample of Sandstone, gray, medium-grained to 10 sandstone taken from the same horizon 81 feet coarse-grained, crossbedded, with hard and soft layers; forms inter farther southwest, at AEC pit EWS-1 contained mittent ledges; contains many fer 0.08 percent equivalent uranium and 0.096 percent ruginous uraniferous concretionary uranium. This zone of ferruginous radioactive masses that cut across bedding sandstone crops out for a distance of 450 feet and resemble the uranium-bearing con farther southwest but the amount of radioactivity cretions in the Pumpkin Buttes area. apparently decreases in that direction. High radio Some meta-autunite or uranospinite(?) is activity was detected at a number of additional visible. A channel sample of 1 foot of sandstone contained 0.21 percent equiv places southeast and east of locality 7 on the same alent uranium and 0.2*4- percent uranium. ridge and in the same sandstone. A pebble of dark- gray basic igneous rock from this locality contained Shale, brown, carbonaceous, slightly radio 0.5 0.52 percent equivalent uranium and 0.95 percent active. uranium. Concentric zones of alteration suggest Sandstone and claystone, greenish-brown, 10 that uranium soaked into the pebble from solutions soft, interbedded. in the surrounding sandstone. Shale, dark brown, carbonaceous, slightly radioactive. Locality 8 (NEjSEJSWi- sec. 23. T. 33 N.. Sandstone and claystone, greenish- 20 R. 90 W.). The black Thermopolis shale of Early brown, soft. Cretaceous age is the site of locality 8. A chan nel sample of the shale taken at AEC pit EWS-8 Shale, brown, carbonaceous. 1 contained 0.039 percent equivalent uranium and Sandstone and claystone, greenish- 25 0.041 percent uranium. The shale dips west about brown, soft. 35° and is overlain by essentially horizontal fer ruginous conglomeratic sandstone in the Wind River The uraniferous sandstone crops out exten formation. The radioactive zone is about 30 feet sively along the top of a broad upland area. A below the Muddy sandstone member. Neither the 1-foot channel sample of this sandstone from AEC Muddy sandstone member nor the basal sandstone pit EWS-6, about 36 feet southwest of the measured of the Wind River formation show more than a Figure 3. Wind River formation at locality 7. Arrow marks zone of uraniferous sandstone. Flats in left back- ground cut on Cody shale.
Unit Estimated normal background radioactivity count. The radio no. Lithologic character thickness active zone in the Thermopolis shale extends for (feet) more than 50 feet north-south, and has a strati- Conglomerate, gray; composed largely of 30 graphic thickness of about 10 feet, but the radio "boulders of mouse-gray andesite*de activity gradually diminishes in both directions rived from volcanic rocks of middle Eocene age in the Rattlesnake Hills; from the pit where the sample was taken. conglomerate interbedded with a minor amount of chalky white crystal tuff; The sandstones of the Wind River formation were slightly radioactive. deposited in a steep narrow valley cut along the strike within the soft Thermopolis shale and flanked on the Sandstone, yellowish-white, coarse-grained, slightly tuffaceous, soft, interbedded west by a resistant ridge of Mowry shale and on the with conglomerate in which roundstones east by resistant sandstone in the Cleverly formation. are of pre-Cambrian granite and Eocene The writer believes that the uranium carried by volcanic rocks from the Rattlesnake Hills; ground water along porous sandstones in the Wind River slightly radioactive. formation could not escape laterally because of the Volcanic conglomerate, mouse-gray, com 30 confines of the pre-Wind River valley, and was depos posed largely of "boulders of gray ited in carbonaceous shales in the nearly impervious andesite porphyry derived from Eocene underlying Thermopolis shale. Sandstones in the vents in the Rattlesnake Hills; some Cloverly formation on the east side of this pre-Wind "boulders ^ feet in diameter; slightly River valley are slightly radioactive. radioactive. Sandstone, pale yellow, very coarse 50 Locality 9 (NWJNEJSWj sec. 17. T. 33 N.. grained, arkosic, soft, with white tuff R. 89 W). A uranium occurrence in middle Eocene fragments; slightly radioactive. rocks is the site of locality 9. It is in the middle of Sandstone and conglomerate, gray to dark- 30 an area where the background radioactivity is several "brown, with very ferruginous lenses in times as high as the average in adjacent localities of middle; some lenses 15 feet thick and pre-Tertiary rocks. The rocks are very ferruginous 100 feet long; a channel sample of coarse-grained conglomeratic sandstones near the base 2 feet of sandstone from one lens con of the middle and upper Eocene sequence. A 2-foot tained 0.06 percent equivalent uranium channel sample contained 0.06 percent equivalent ura and 0.078 percent uranium; conglomerate nium and 0. 078 percent uranium. These rocks crop intertongued with the sandstone con tains rounded fragments of pre-Cambrian out as dark-brown discontinuous ledges for half a mile. granite and Eocene andesite porphyry A reconnaissance section of the rocks is listed from the Rattlesnake Hills; some andesite from top to bottom as. follows: "boulders are 3 feet in diameter. Locality 10 (C SEJNE4- sec. 27. T. 33 N.. ORIGIN OF URANIUM IN THE GAS HILLS AREA R. W.). A carbonaceous shale near the top of the Wind River formation is the site of locality 10. A chan Insufficient data are available on the occurrences nel sample of 1 foot of shale contained 0.078 percent of uranium minerals now known in the Gas Hills area equivalent uranium and 0.062 percent uranium. This to warrant a definite statement as to the origin of the carbonaceous shale bed overlies coarse-grained deposits. It is apparent that these minerals were de greenish-yellow arkosic sandstone. The top of the bed posited in their present sites by water moving through grades upward through 6 inches of slightly carbonaceous ithe rocks and bringing uranium into an environment shale to a greenish-gray plastic claystone. Leaves favorable for precipitation. The source of the uranium identified by R. W. Brown of the U. S. Geological Sur ions and the origin of the water that carried them can vey from this carbonaceous shale are: Ulmus sp., only be assumed at the present time. Leguminosites sp., Aralia sp., Quercus castaneopsis, and Zizyphus cinnamomoides and are considered to be The uranium deposits may be the result of hydro- of early or middle Eocene age. The carbonaceous shale thermal solutions coming from the volcanic rocks in is exposed in an area about 75 feet long and 25 feet wide and south of the Rattlesnake Hills. These volcanic but its uranium content suggests that uraniferous ground rocks are dacites, andesites, and alkalic rocks waters have been in the area and that higher grade de F. B. Van Houten (personal communication) and posits may be present in more favorable host rocks. B. D. Carey, Jr., (1954) of middle and late Eocene age. There is no known evidence of hydrothermal activity in Locality 11 (NE cor, sec. 11. T. 32 N.. the Gas Hills area other than, possibly, the uranium R. 90 W.). -The site of locality 11 is Cameron Spring deposits themselves. The writer prefers the theory that which issues from the White River formation of Oligo- the uranium originally was a primary constituent in the cene age, 100 feet or more above the base of the se ashes in the White River formation or younger Tertiary quence, and 250 feet or more below the top. The water rocks in this area, that the uranium was leached out by is clear, cold, and comes out along fractures in light- ground water which transported it downward and later tan hard tuffaceous claystone. The water contains ally along sandstone aquifers in the middle Eocene se 0. 010 ppm uranium. quence and the Wind River formation, and that the ura nium concentrated wherever favorable host rocks were Other localities of interest. A spring issues found. This theory of origin was likewise advocated from a very ferruginous conglomeratic sandstone in the for the uranium deposits in the Pumpkin Buttes area upper part of the Wind River formation in the NW-JSEl of northeastern Wyoming (Love, 1952, p. 17). The sec. 33, T. 34 N., R. 89 W. This spring flows about Oligocene and younger rocks once extended over the a 1-inch pipe full of clear cold water that contains Gas Hills area and across the Wind River Basin, for 0.073 ppm uranium. The presence of this much ura remnants are found in the mountains on both sides. In nium is significant because the locality is at an altitude the Pumpkin Buttes area, the Wasatch formation, which of about 6, 800 feet, higher than nearly all the uranium is the same age as the Wind River formation and has deposits found in the Gas Hills area, and is about 3 miles much the same lithology, contains uranium deposits and northeast of the Gas Hills, beyond the border of the is overlain by the White River formation, which is ura area shown in figure 1. niferous (Love, 1952). A locality near the center of the SWi sec. 29, Denson, Bachman, and Zeller (1951) have re T. 33 N., R. 90 W. shows many places where meta- ported uraniferous lignites of Paleocene age overlain autunite is concentrated in ferruginous coarse-grained by the White River formation in South Dakota. soft porous sandstone in the middle part of the Wind J. R. Gill (personal communication) has found carno- River formation. A spectrographic analysis of a sam tite in the White River formation in the Slim Buttes ple collected for mineralogic study showed more than area, South Dakota, and G. W. Moore and H. A. Tour- 10 percent uranium. telot (personal communication) have found uranocircite and tyuyamunite in rocks of the White River formation In the NWiSWiNWi sec. 6, T. 32 N., R. 90 W., in the Big Badlands of South Dakota. Miocene (?) rocks there are localized concentrations of an unidentified in the Miller Hill area, southern Wyoming, contain calcium uranyl phosphate mineral, greenish-yellow in 0.15 percent or more uranium (Love, 1953), and tuff color, nonfluorescent, and which, according to aceous limestones of Pliocene (?) age in the Split Rock L. B. Riley (personal communication, 1954), contains area, 16 miles south of the Gas Hills, contain0.023per more than 10 percent uranium, 1-2 percent elemental cent uranium (Love, 1952, unpublished report, sup phosphorus, traces of barium, and arsenic. The min plemented by later field studies). Carnotite occurs in erals are concentrated in and adjacent to a petrified log tuffaceous sandstones in the lower Pliocene(?) North which is embedded in a coarse-grained gray sandstone Park formation of the Saratoga area. in the middle of the Wind River formation. A channel sample of 1 foot of sandstone adjacent to the log con In all of these areas, the possibility of hydro- tained 4. 7 percent equivalent uranium, 6. 72 percent thermal activity that would form uranium deposits seems uranium, and 0.1 percent V2 O 5. slight. The White River formation in the Gas Hills area is contributing above-normal amounts of uranium to Another locality where considerable uranium min ground water today (table 2) and may have supplied the erals occur is about half a mile northeast of Coyote uranium now found in the underlying rocks. The ura Spring (locality 6), in the southern part of the SEi sec. 12, nium in the water in the Wind River formation may come T. 32 N., R. 91 W. Both meta-autunite and the either from the White River formation or from second unidentified greenish-yellow uranium mineral are pres ary uranium minerals previously deposited by ground ent. The host rock is a ferruginous conglomeratic water in the Wind River formation. sandstone in the lower part of the Wind River formation northeast of a partly exhumed hill of Mowry shale sur Characteristics of the currently known deposits rounded by the Wind River formation. that need further investigation and that will assist in determining the origin and history of the deposits in clude (1) additional mineralogic studies of the meta- autunite, uranospinite(?), and the unidentified calcium In bO uranyl phosphate mineral, and (2) the relationship be O S tween the level of radioactivity expressed as percent O "> co O O equivalent uranium and the amount of uranium chemi o3 ^-d C cally determined. O « cd > o5 ^J The level of radioactivity of the samples expressed O O £> * as percent equivalent uranium and uranium chemically o3 .»Ch In H t- determined is out of balance; in some samples the radio -P O CM In « activity is in excess of the uranium content and in others O "d O 0 the radioactivity is deficient. In sample 99207 (table 1), O » > I H O H the radioactivity of 0.047 percent equivalent ura fe O d C oo nium is more than 3 times the uranium content of o3 »> co «CO iH 0.014 percent, and in sample 99205, the equivalent- uranium content of 0.58 percent is more than twice the uranium content of 0. 25 percent. In other samples, O O -H however, the uranium content is greater than the radio S vH H CO O H ps activity expressed in percent equivalent uranium. For Pi O S example, sample 99204 contains 1. 87 percent uranium o ,rj but only 1. 2 percent equivalent uranium, and sample Pi C c -p CO O H vH -H 206974 contains 6. 72 percent uranium but only 4. 7 per H P H > C H cent equivalent uranium. The significance of these var 0 H co O O -P -P -H O PivH bO O iations may become apparent as more data accumulate, H -P C 03 Pi 05 -H -P and should lead to a better understanding of the origin jii » TJ -d o H c & £ o o and history of the deposits. H Pi vH O O H O 00^ C In In O CO H O
-I** ^ H O bO O POSSIBILITY OF INDUSTRIAL HEALTH HAZARD > C ,a ^ P-. In bOv-H -H 03 o c' C « P H Pi-P Eleven samples were analyzed for selenium and O C 3 arsenic, as well as for uranium (table 1). Beath (1946, o t^- H v-H 0) "-9 01 p. 7-10)has described the occurrence of highly seleni- -p Pj ^ "O C > c bOln !>a O ferous tuffaceous strata of middle and late Eocene age
O H| j O H| j O Beath, O. A., Hagner, A. F., and Gilbert, C. S., 1946, Some rocks and soils of high selenium content: CM K\ H t^- Wyo. Geol. Survey Bull. 36, 23 p. 00 Carey, B. D., Jr., 1954, Geologic map and structure sections of the Rattlesnake Hills volcanic field, Natrona County, Wyoming: Wyo. Geol. Assoc. 9th Ann. Field Conf. Guidebook map. Love, J. D., 1952, Preliminary report of uranium de VO posits in the Pumpkin Buttes area, Powder River Basin, Wyoming; U. S. Geol. Survey Circ. 176. ______1953, Preliminary report on uranium de P O posits in the Miller Hill area, Carbon County, O C Wyoming: U. S. Geol. Survey Circ. 278. 03 O t- M E~- K\ Love, J. D., Johnson, C. O., and others, 1945, Strati- O Pi ON O graphic sections and thickness maps of Triassic >O CM rocks in central Wyoming: U. S. Geol. Survey Oil ON and Gas Chart 17. 10 Love, J. D., Thompson, R. M., and others, 1945, Voegtlin, Carl, and Hodge, H. C., 1949, Pharmacology Stratigraphic sections and thickness maps of Lower Cre and toxicology of uranium compounds: National taceous and non-marine Jurassic rocks of central Wyo Nuclear Energy Series, Manhattan Project, Tech. ming: U. S. Geol. Survey Oil and Gas Chart 13. Sec., Div. 6, v. 1, pts. 3 and 4, Chronic inhalation Love, J. D., Tourtelot, H. A., and others, 1945, and other studies, McGraw Hill Book Co. Stratigraphic sections and thickness maps of Jurassic rocks in central Wyoming: U. S. Geol. Survey Oil and Gas Chart 14. UNPUBLISHED REPORTS ______1947, Stratigraphic sections of Mesozoic rocks in central Wyoming: Wyo. Geol. Survey Bull. 38, 59p. Denson, N. M., Bachman, G. O., and Zeller, H. D., Love, J. S., Weitz, J. L., and Hose, R. K., 1952, 1951, Summary of new information on uranif- Geologic map- of Wyoming: U. S. Geol. Survey map. erous lignites in the Dakotas: U. S. Geol. Thompson, R. M., Love, J. D., and Tourtelot, H. A., Survey Trace Elements Memo. Rept. 175. 1949, Stratigraphic sections of pre-Cody Upper Cre Love, J. D., 1952, Preliminary report on uranium- taceous rocks in central Wyoming: U. S. Geol. Sur bearing Pliocene (?) rocks in the Split Rock area, vey Oil and Gas Chart 36. central Wyoming: U. S. Geol. Survey Trace Ele Trelease, S. F., and Beath, O. A., 1949, Selenium, ments Memo. Rept. 282. its geological occurrence and its biological effects Rachou, J. F., 1951, Tertiary stratigraphy of the in relation to botany, chemistry, agriculture, nu Rattlesnake Hills, central Wyoming: [Unpub trition, and medicine: 292 p. Published by the lished master of arts thesis in files of Univ. authors, Box 42, Schermerhorn Hall, Columbia Wyo. library. ] University, N. Y. Weeks, A. D., and Thompson, M. E., 1953, Van Houten, F. B., Volcanic-rich middle and upper Identification and occurrence of uranium and Eocene sedimentary rocks northwest of Rattlesnake vanadium minerals from the Colorado Plateaus: Hills, central Wyoming: U. S. Geol. Survey Prof. U. S. Geol. Survey Trace Elements Inv. Paper 264. [In preparation. ] Rept. 334.
INT.-DUP. see., HASH.. 0,0.71409 11