GEOLOGICAL SURVEY CIRCULAR 338 

SUMMARY OF INVESTIGATIONS OF 

URANIUM DEPOSITS IN THE PUMPKIN 

BUTTES AREA, JOHNSON AND 

CAMPBELL 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. 

!.:' ).~:::: ': :-: . .::·: :-.:.::: ::.:·:::: :·::::·)./:: ::::};·:::;:.~ 

i1:;*ii1\r!~J!i(~_,_ ; ~----------
UNITEb STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary 

GEOLOGICAL SURVEY 

W. E. Wrather, Director 

GEOLOGICAL SURVEY CIRCULAR 338 

SUMMARY OF INVESTIGATIONS OF URANIUM DEPOSITS IN THE PUMPKIN 

BUTTES AREA, JOHNSON AND CAMPBELL COUNTIES, WYOMING 

By Max L. Troyer, Edward J. McKay, Paul E. Soister, 

and Stewart R. Wallace 

S. N JUAN URANIUM EXp_L.O&All.O~ IN~ 

This report concerns work done on 

behalf of the U. S. Atomic Energy 

Commission and is published with 

the permission of the Commission. 

Washington, D. C., 1954 

Free on application to the Geological Survey, Wa'khington 25, D. C. 

,. 

J,'if·t~-~~~ :# 
41 

I ' ' Cheyen:J 

------ 41° 

105° 

Figure 1. -Index map of Wyoming, showing location of the Pumpkin Buttes area. 

ii 
SUMMARY OF INVESTIGATIONS OF URANIUM DEPOSITS IN THE PUMPKIN 

BUTIES AREA, JOHNSON AND CAMPBELL COUNTIES, WYOMING 

By Max L. Troyer, Edward J. McKay, Paul E. Soister, 

and Stewart R. Wallace 

CONTENTS 

Page 

Abstract ..............................•...... 

Introduction ................................. . 

1 

2 

Location, culture, and accessibility...... . 2 

Physical features. . . . . . . . . . . . . . . . . . . . . . . . 2 

Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 2 

Geologic setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Stratigraphy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

General statement. . . . . . . . . . . . . . . . . . . . . . . 12 

Fort Union formation . . . . . . . . . . . . . . . . . . . . 12 

Page 

Stratigraphy -Continued 

Wasatch formation. . . . . . . . . . . . . . . . . . . . . . . 12 

White River formation .................... 12 

Uranium deposits............................ . 12 

Mineralogy ................................... 15 

Limits of known principal uranium mineralization.. 17 

Guides to prospecting....................... . . 17 

Literature cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

Unpublished reports. . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

ILLUSTRATIONS 

Page 

Plate 1. Geologic map of the east-central part of the Pumpkin Buttes area. . . . . . . . . . . . . . . . . . . . . . . . . . . In pocket 

2. Geologic map showing localities of uranium mineralization in the Pumpkin Buttes area ........ In pocket 

Figure 1. Index map of Wyoming, showing location of the Pumpkin Buttes area...................... . . . . . . . ii 

2. Sketch map of structure contours of the Wasatch formation, east-central part 

of the Pumpkin Buttes area................................................................. 3 

3. Composite stratigraphic section of rocks, showing zone of principal 

uranium occurrence in the Pumpkin Buttes area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

4. Sketches of thin sections from concretiona:ry deposits, 

showing progressive stages of mineralization .............•........... , . . . . . . . . . .. . . . . . . . . . . . . 14 

5. Map showing area of principal occurrences of uranium in the Pumpkin Buttes area . . . . . . . . . . . . . . . . . 16 

TABLE 

Page 

Table 1. Localities of known uranium mineralization or anomalous high radioactivity, 

Pumpkin Buttes area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

ABSTRACT 

Uranium minerals were discovered in the Pumpkin 

Buttes area, Campbell and Johnson Counties, Wyo., by 

the U. S. Geological Survey in October 1951. From 

June to November 1952, an area of about 750 square 

miles was examined for uranium deposits, and 21llocalities having abnormally high radioactivity were found; 

uranium minerals are visible at 121 of these localities. 

All known uranium mineralization in the area is 

restricted to sandstones of the Wasatch formation, except sparsely disseminated uranium in thA sandstone of 

1 

the White River formation, which caps the Pumpkin 

Buttes, and several localities on the Great Pine 

Ridge southwest of the Pumpkin Buttes where ironsaturated sandstone and clinker in the Fort Union 

formation have above-normal radioactivity. The 

uranium occurrences in the Wasatch formation are 

in a red sandstone zone 450 to 900 feet above the 

base of the formation and are of two types: small 

concretionary masses of uranium, iron, manganese 

and vanadium minerals in sandstone, and irregular 

zones in which uranium minerals are disseminated 

in sandstone. The second type is usually larger 

but of lower grade than the first. 
Most of the localities at which uranium occurs are 

in a north-trending belt about 60 miles long and 18 miles in 

maximum width. 

INTRODUCTION 

Location, culture, and accessibility 

Uranium was discovered in the Pumpkin Buttes 

areabythe U.S. GeologicalSurveyinOctober 1951, and a 

brief reconnaissance study was made in mid-November of 

thatyear (Love, 1952). InJune 1952, investigations were 

resumed to search for additional concentrations of uranium, to study distribution, habit, and occurrence of such 

concentrations, and to use the information thus obtained 

as a guide in outlining areas favorable for the occurrence of uranium deposits. The results of the work are 

presented in this report. 

In the vicinity of Pumpkin Buttes all rocks 

known to contain uranium in other than trace 

amounts, excepting a few thin carbonaceous shales 

and coals, are sandstones of the Wasatch formation. These sandstones were mapped by reconnaissance methods in an area of about 100 square 

miles. About 70 of these 100 square miles are 

shown on plate 1. The rest of the mapped area 

is west of the area shown on plate 1 where topographic sheets are lacking. Areas east of the 

mapped sandstones thought to be favorable for the 

occurrence of uranium are also shown on plate 1. 

Six stratigraphic sections totaling a thickness of 

7, 000 feet were measured and more than 200 localities 

were examined where anomalous radioactivity was 

detected and reported by U. S. Geological Survey and 

Atomic Energy Commission planes equipped with 

scintillation-type counters. The localities where uranium minerals were seen or above-normal radioactivity 

was detected on the ground are shown on plate 2 and 

described in table 1. 

Physical exploration in the area by the Geological 

Survey consisted of test holes drilled with a jeepmounted auger and excavation by bulldozer. 

This work is a part of the program of exploration 

for radioactive minerals being conducted by the 

U. S. Geological Survey on the behalf of the Division of Raw Materials, U.S. Atomic Energy Commission. 

The Pumpkin Buttes area (fig. 1) includes about 

750 square miles in southwestern Campbell County 

and southeastern Johnson County, Wyo., in the 

west-central part of the Powder River Basin. The 

southern part of the area is crossed by State Highway 387, and the eastern edge is accessible by a 

graveled road locally known as the Savage ton route. 

One graded dirt road leads into the area from near 

the northeast corner and ends at the Jack Christensen ranch southwest of the North Butte. Most of 

the area is accessible by ranch roads and trails 

that are in fair condition during the summer months. 

Gillette, the county seat of Campbell County, with 

a population of about 2, 000, is the largest town serving 

the region, and is about 30 miles northeast of the northeast corner of the Pumpkin Buttes area. Kaycee, 

Sussex, Edgerton, and Midwest are small towns 15 to 

20 miles west and southwest of the buttes. Access to 

the area from these towns is by private roads. 

2 

Physical features 

The Pumpkin Buttes are close to the divide between the Powder River and the Belle Fourche River 

drainage systems. The buttes rise about 1, 000 feet 

above the surrounding country and are a prominent 

landmark visible for as much as 80 miles. The land 

north and east of the buttes is grass -covered and gently 

rolling; relief between divides and adjacent ·drainage 

basins is commonly less than 200 feet. The land southwest and west of the buttes is dissected by many deeply incised valleys, and in a few places badlands have developed. 

Two-thirds of the region, including the northern 

and northwestern parts, are drained by the Powder 

River and its ephemeral tributaries, the Dry Fork, 

Cottonwood Creek, Willow Creek, and Pumpkin Creek 

(pl. 2). The area south of State Highway 387 is drained by 

Antelope Creek, which is a part of the Cheyenne River 

drainage system. The eastern edge of the area is in the 

Belle Fourche River drainage basin. Vegetation is mainly 

grass and sagebrush; small conifers are found on the 

upper slopes of the buttes and some cottonwood trees 

grow along the major valley bottoms west of the buttes. 

Acknowledgments 

Much of the information used in this report was 

gathered from the U. S. Geological Survey and the 

Atomic Energy Commission airplanes equipped with 

scintillation detectors. Spectrographic, chemical, and 

radioactivity analyses were made in the Geological 

Survey's laboratory. Arthur J. Gude, 3d, made X-ray 

analyses of some of the uranium minerals. Paleobotanical and vertebrate specimens collected in the area 

were identified by R. W. Brown and Margaret J. Hough, 

respectively. J. D. Love measured many of the stratigraphic sections. D. F. Davidson, R. Hay, T. Scott, 

W. C. Culbertson, and E. D. Patterson assisted with the 

work at various times during the ·field season. Ranchers living in the area and corporation personnel working in the vicinity cooperated in many ways. 

GEOLOGIC SETTING 

The Powder River Basin is a large topographic and 

structural basin that covers most of the northeast quarter 

of Wyoming and extends northward into Montana. The 

basin is bordered on the east by the Black Hills, on the 

southeast by the Hartville uplift, on the south and southwest by Casper Mountain and the Powder River lineament, 

and on the west by the Bighorn Mountains. 

The structural axis of the basin is near the western 

side, and all but the southwest part of the Pumpkin Buttes 

area lies east of the axis (pl. 2). In the in,_mediate vicinity of the buttes, the Wasatch formation dips generally 

west and northwest. Except for local diagenetic and depositional features, the beds are nearly horizontal; dips 

range from less than 30 feet a mile east of the buttes to 

more than 100 feet a mile in the area west of the buttes. 

Figure 2 is a generalized structur e contour map 

of the Pumpkin Buttes area compiled from limited data. 

The buttes are on the west flank of a broad northnorthwest plunging anticline, the east flank of which is 

described by Wegeman, Howell, and Dobbin (1928). A 

slight syncline and anticline are in the northeastern part 

of the area. 
I 

T. 

45 

N. 

T. 

44 

N. 

T. 

43 

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R. 74 W. 

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~North Butte 

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EXPLANATION 

-- -~ - " 

Inferred structure contours based 

on an arbitrarily selected 

stratigraphic horizon a bout 

800 feet above the base of 

the Wasatch formation 

Datum is mean sea level 

--t-~ Anticlinal axis in the 

Wasatch formation 

- -+-~ -

Synclinal axis in the 

Wasatch formation 

0 3 Miles I l I 

43°37~' 

I 05°45' 

Figure 2. -Sketch map of structure contours of the Wasatch formation, east-central part of the Pumpkin Buttes 

area, Wyoming. 

3 
Table l. -Localities of known uranium mineralization or anomalous high radioactivity, Pumpkin Buttes a!'ea, Wyoming 

Local- Field Equiva- Kind of 

ity Location 1 sample lent Uranium V205 Mn Other Type of local- Discovuranium (percent) (percent) (percent) (percent) sample2 ity 3 erer 4 Remarks no. no. (percent) 

l 15-45-75 TW-65 3.7 3.85 o.8o 1.19 ------------ s M G 

2 22-45-75 TW-64 .24 .21 .26 .248 10.83 C0 2 s M G 

3 22-45-75 TW-63 9.1 14.62 3.32 .so ------------ s M G 

4 29-45-75 TW-7 14.2 17.08 .38 1.17 ------------ s M u 

5 28-45-75 TW-21 10.0 8.43 1.51 7.4 ------------ s M G 

6 27-45-75 TW-5 3.2 3.98 1.96 7.56 ------------ s M G 

7 33-45-75 TW-6 6.7 7.7 2.69 .63 ------------ s M u 

8 34-45-75 ----------------------------- ---------~--------- ------------ -------- M G 

9 36-45-76 LW-86 5.7 6.34 .47 l.l ------------ s M G 

LW-87 4.2 4.72 l. 75 5.1 ------------ s ------------------- 10 35-45-76 LW-82 1.9 2.97 1.21 .63 ------------ s M G 

LW-83 2.1 2.30 .ss s.8 ------------ s -------- ---------- LW-84 2.3 2.43 .92 . 5.3 ------------ s r--------- ---------- LW-85 5.2 5.62 .64 2.5 ------------ s --------- ---------- ll l-44-76 LW-121 20.0 23.6 .18 .36 ------------ s M G 

12 12-44-75 TW-3 .44 .ss 1.54 .07 ------------ s M u 

TW-4 .004 .003 .32 .10 7.28 C02 s r--------- ---------- Host sandstone. 

13 9-43-75 LW-100 8.5 12.85 1.79 3.6 ------------ s -------- ---------- fl:>. LW-104 6.5 9.46 1.24 .19 ------------ s M G 

LW-105 .06 .079 .l . 12 ------------ s r--------- ---------- Host sandstone . 

14 15-43-76 LW-56 1.7 l. 77 1.31 ----------------------- s -------- ---------- LW-57 .006 .004 .05 ---------------------- c M G Host sandstone. 

15 22-43-76 LW-51 .036 .025 .07 ---------------------- c R G Near deposit. 

16 22-43-76 LW-54 s.s 5.42 2.44 ---------------------- s r------------------- LW-55 .018 .013 .04 ----------------------- c -------- ---------- Host sandstone. 

LW-59 .003 .002 .06 ---------------------- s -------- ---------- Do. 

LW-60 .009 .010 .04 ---------------------- s M u Do. 

LW-61 .26 .19 .86 ----------------------- s -------- ---------- Manganiferous part of 

deposit, 

LW-62 4.6 4.57 1.72 ---------- ----------- s .. -------- ---------- TW-41 .007 .004 .06 .147 ------------ c r---------- ---------- Highly contaminated 

auger-hole sample . 

TW-42 .45 . 48 .35 .945 6.75 C02 c f----------r-----------

TW-46 .13 .12 .19 .468 7.19 C02 c -------- ---------- Do. 

17 22-43-76 LW-52 1.2 1.38 .96 ----------r------------- s M u 

LW-53 . 006 .004 .07 f-----------r------------- c M u ~ost sandstone . 

18 22-43-76 LW-63 .079 .10 .06 ----------r------------- s -------- ---------- ~pper 4 ft of coal below sandstone. 

LW-64 .037 .008 .10 ---------- ----------- c M G ~asal 5 ft of sandstone 

19 22-43-76 LW-48 .027 .024 .06 -----------r------------ s -------- ---------- ~op 5 ft of coal below 

sandstone. 

LW-49 .004 .001 .06 ----------r------------- s f--------- ---------- !Host sandstone. 

. 
19 122-43-76 LW-50 7.4 7·27 1.63 ---------------------- s M G 

20 19-43-75 LW -120 s.8 6.59 2.09 6.00 ------------ s M G 

TW-38 .34 .34 1.02 . 6.70 4.15 C02 s ------- ----------- 21 130-43-75 LW-110 3.8 4.02 .46 17.88 ------------ s M G 

22 25-43-75 LW-66 .98 1.78 .67 ---------------------- s ------------------- LW-67 .021 . 020 .04 ---------------------- s M G ~ost sandstone . 

LW-68 .oo8 .007 .08 ---------------------- s ------- ----------- pper 0.25 ft of 

siltstone under 

sandstone. 

LW-69 .31 .53 .53 ---------- ----------- s -------------------l:ase of sandstone. 

23 136-43-76 I LW-107 .10 .026 .08 1.09 ----------- c M G ost sandstone a nd 

uranium deposit. 

LW-108 . 023 .003 .05 l.ll ------------ c -------------------Host sandstone. 

LW-109 .031 .025 .07 .76 ------------ c ------------------- 24 31-43-76 ---------- --------- --------- -------- ---------------------- --------- M G 

25 35-43-76 TW-10 .62 .63 .61 4.0 2.69 C0 2 s M G 

26 4-42-76 LW-88 7.6 9.7 .68 1.2 ----------- s M G 

27 4-42-76 -------------------- --------- -------- ---------- ----------- --------- M G 

28 4-42-76 TW·-40 .042 .030 .08 .60 8.72 C02 c M G ~ost sandstone and 

uranium deposit . 

29 I 4-42-76 LW-112 l.l . 085 .15 .17 ----------- s -------

LW-113 .21 .005 .05 2.29 ----------- s M G Manganiferous host 

I sands tone. 

30 I 2-42-76 u-9 l.l 1.27 CJ1 TW-39 .98 .99 1.1557 2.421 ----------- ----------- S M G s -------------------l 

31 22-43-76 C-171 6.9 6.79 -------- ---------- 7.4 CaO --------- ------- -----------

-------------------- 7.69 2.94 ---------- .22 so~ s M G 

C-172 2.5 2.5 l. 29 ---------- 0. 2 CaO S ------- -----------

--------- ---------- 3.09 -------- --------- .33 so~ --------- ------------------- 50 lbs of average 

grade from bulldozed deposit. 

LW-44 4.2 3.92 1.97 [ __________ [ __________ ] s ------- LW-45 .54 .54 .35 ---------- ----------- c ------- ===========1Basa1 1 ft of host 

sandstone . 

LW-46 .20 .15 . 14 ---------- ---------- c ------- ----------- Basal 3 ft of host 

sandstone. 

LW-47 .009 .007 .10 ---------- ----------- c ------- ----------- Host sandstone. 

32 5-45-75 --------- ---------- --------- -------- ---------- R A 

33 8-45-75 LW-122 .89 1.42 .31 6.20 ----------- s M G 

34 11-45-75 --------- -------------------- -------- ---------- ----------- -------- R G 

35 11-45-75 ---------·- -------------------- -------- ---------- ----------- -------- M u 

36 11-45-75 --------- -------- ---------- ----------- --------- R u 

37 11-45-75 TW-106 1.7 2.27 1.00 .237 ----------- c M G !Auger-hole sample. 

TW-107 .061 .03 .04 .028 ---------- c ------- -----------~ Do. 

38 11-45-75 TW-110 .024 .003 .05 .037 ----------- c M u 

39 15-45-75 --------- -------- ---------- ----------- --------- M G 

40 18-45-75 --------- -------------------- -------- ---------- ----------- -------- R u 

41 22-45-75 TW-111 .10 . 052 .b8 .189 ----------- c M u !Auger-hole sample . 

42 30-45-75 TW-113 .10 .006 .18 .064 ----------- s R u 

43 33-45-75 TW-114 l.O .92 .so 12.85 ----------- s M A !Manganese concre- tion. See footnotes at the end of the table. 
a:> 

Table 1.--Localities of known uranium mineralization or anomalous high radioactivity, Pumpkin Buttes area, Wyoming--Cont. 

Locality 

no. 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 

,55 

56 

57 

58 

59 

60 

61 

62 

63 

64 

65 

66 

67 

68 

69 

70 

71 

72 

73 

74 

Location 1 

34-45-75 

31-45-75 

36-45-76 

36-45-76 

36-45-76 

30-46-76 

I 5-45-76 

5-45-76 

9-45-76 

16-45-76 

16-45-76 

15-45-76 

'21-45-76 

22-45-76 

22-45-76 

22-45-76 

27-45-76 

26-45-76 

26-45-76 

23-45-76 

24.:.45-76 

33-45-76 

35-45-76 

35-45-76 

4-44-76 

l-44-77 

10-44-76 

3-44-75 

3-44-75 

3-44-75 

l0-44-75 

Field 

sample 

no. 

Equivalent 

uranium 

(percent) 

Uranium I V 2 0 5 ,. Mn 

(percent) (percent) (percent) 

Other 

(percent) Type of 

sample 2 

~---------~----------~---------~--------1----------~------------~---------

~---------~----------~---------~------------------

~--- ------------_ -----r---------r------------------!------------r--------- -------------------- --------- ------------------ ---------------------- TW-76 0.11 0 .. 078 0.35 0.13 ------------ S 

TW-78 1.2 1.84 1.53 .98 ------------ S 

TW-79 I .13 .084 .13 .05 ------------ s 

TW-80 .72 .95 .75 1.36 ------------ S 

TW-81 .20 .032 .58 .27 ------------ S 

Kind of 

locality3 

R 

M 

M 

M 

M 

M 

tDiscoverer4 

u 

u 

A 

A 

A 

---------------- ----------------------------- -----------------------~-------- R U 

TW-66 .54 .90 .93 .13 ------------ S M U 

TW -67 . 063 . 064 . 25 .10 ------------ S ----------------

Remarks 

TW -68 . 008 . 008 . 07 .11 ------------ C ----------------45-ft sample. 

TW-124 .27 .47 1.24 .027 ------------ S ---------------- TW-164 .91 .95 ------------------ --------- ------- TW-165 .71 1.26 ------------------ ------------ TW-70 . 013 . 013 . 05 .13 ------------ C --------- ------~10-ft sample. 

TW-89 .068 .027 .14 .15 ------------ C M G 

TW -90 . 22 .19 .11 .37 ------------ S ----------------- ---------·-----------·--------- -~- -------1-------- --~ ----------- -~-- ------- R U 

~=~~---------~:~-------~:~g--r--::~~------- :~~-!============r---~----r ~ g TW-72 .036 .013 .16 .14 ------------ C --------- ------~-ft sample. 

TW-35 .023 .014 .19 .258 ------------ S M G 

TW-34 .21 .17 .29 7.05 ------------ S M G 

TW-112 .06 .023 .08 .277 ------------ C M U 

~ =~~--- -

1

------: ~t8 -r ----: ~~6l ___ : ~f- ------:~~8~=========== = 

---------1 R G 

TW -88 .18 .17 I . 46 . 07 t ___________ _ c 

s 

____________________ [ _________ [ __________________ ! ____________ [ ________ 

s 

_ ------------------------------ ------------------ ------------ --------- ------------------------------ ------------------ ------------ --------- -------------------- --------- ------------------ ------------ --------- TW-8 6.0 9.35 1.54 .02 ------------ S -------------------- --------- ------------------ ------------ ---------

~~=i;;---r----9~;---r--ii~6---r---~;7--r----7~6;-~============ TW-82 2.4 2.84 .42 2.25 ------------ TW-83 .84 1.03 .64 1.25 ------------ TW-85 .067 .038 .17 .14 ------------ TW-84 2.7 2.94 .92 6.40 9.07 C0 2 

--------- s 

s 

s 

s 

s 

R A 

M A 

r--------- ------- M A 

M A 

R G 

M U 

M U 

M G 

R G 

M G 

M A 

M A 

M A 

M G 
-::J 

75 

76 

77 

78 

79 

8o 

81 

82 

83 

84 

85 

86 

87 

88 

89 

90 

91 

92 

93 

94 

95 

96 

97 

98 

99 

100 

101 

102 

103 

104 

105 

106 

107 

108 

109 

110 

lll 

112 

113 

114 

115 

116 

10-44-75 

12-44-75 

18-44-76 

18-44-76 

18-44-76 

18-44-76 

24-44-76 

20-44-75 

22-44-75 

28-44-75 

28-44-75 

28 -44-75 

32-44-76 

4-43-75 

3-43-75 

12-44-78 

28-43-75 

28-43-75 

28-43-75 

29-43-75 

30-43-76 

30-43-76 

3-42-75 

23-42-75 

21-42-75 

l-44-76 

l-44-76 

20-45-75 

TW-86 

C-25399 

.19 

-39 

.029 

2.4 

.085 

.28 

.004 

15.14 

.026 

.18 

2.61 

. 021 I .015 

.153 .153 

.876 

.0341 .006 

.136 .123 

.22 

.38 

.32 ~-----------~ c 

s 

s 

s 

s 

.54 1-------------1 c 3.60 ------------- s 

.05 ~---------~-----------~ s 

.20 

.62 

.03 1 .o4 r------------1 .10 -----------------------

s 

s 

c 

s 

8-45-76 

: ~i81 : .633 g~5~----~=~--~------~~~-t============'----~----- 1.05 --~------J- 2.2 CaO [ ________ _ 

21-45-76 --------- --------- 7+20-46-74 --------- --------- 17-45-74 TW-102 3.4 

13-44-77 --------- --------- 13-44-77 .073 

24-44-77 --------- --------- 28-47-74 .020 

+10-43-77 .323 

20-43-77 .091 

20-43-77 

20-43-77 

16-43-77 

8-43-77 

TW-ll 

See footnotes at the end of the table. 

.10 

.044 

.29 

.007 

.519 

.064 

.073 

. 031 

.49 

2.28 

.09 

.67 

.69 

.98 

. 26 

.22 

.305~------------

.07 -------------

s 

s 

s 

s 

s 

s 

s 

M 

R 

M 

R 

M 

R 

A 

u 

G 

G 

G 

G 

M 

------~Coal below sandstone. 

u ---------~-------Green siltstone near deposit. 

R U 

M G 

R U 

M U 

M G 

R U 

R G Coal below sandstone . 

R U 

M A 

R U 

M U 

M G 

R U 

M G 

M G 

R U 

R U 

M U 

R A 

R A 

M A 

M G Coal near siltstone. 

M G 

R A 

M A 

M G 

M G 

R G 

M A 

M U 

R U Ironstone . 

R U Ironstone . R ·u Do. 

M U 

R U Ironstone. 
Table 1.--Localities of known uranium mineralization or anomalous high radioactivity, Pumpkin Buttes area, Wyoming--Cont. 

Local~ i ty Location 1 Field 

sample no. no. 

117 

118 

119 

5-42-76 ILW-90 

12-42-78 

36-43:..76 

LW-16 

LW-17 

LW-71 

IM-114 

LW-115 

LW-116 

LW-117 

LW-118 

LW-119 

TW-43 

Equivalent 

uranium 

(percent) 

0.052 

.001 

.10 

.12 

.014 

4.8 

.025 

.012 

14.0 

.o88 

.033 

Uranium I V2 05 I Mn 

(percent) (percent) (percent) 

Other 

(percent) 

0.081 

.003 

.062 

. 10 

.oo8 

5.33 

.018 

.003 

22.4 

.084 

.020 

0.17 0.03 r-----------

t

-------- __________ ! __________ _ ------------------- ----------- .08 ----------- ----------- .42 20.48 -----------

.66 2.05 -----------

.07 .17 -----------

. 05 1.18 r-----------

.87 

.05 

-35 

-35 

.08 

17.9 

r------------

r-----------

1 

Type of 

1

. Kind of 

sample 2 local- ity 3 

Discoverer·4 Remarks 

s 

s 

s 

s 

s 

s 

c 

c 

c 

s 

R G Carbonaceous shale below sandstone. 

--------l----------roal near siltstone. 

M U ed baked siltstone. 

------------------- rown baked siltstone . 

===~========~====== l~::a::::l::n::::i::~e of sandstone . 

---------·------------11-ft sample of manganiferous sandstone. 

---~-----'==========j3.2-ft sample of lightbrown sandstone near deposit. Manganese 

nodule. 

OJ 120 

121 

36-43-76 

25-43-76 ~~=7~-----,----~~;;l----~~;:;-~---~;;--t==========t===========~---~-----

~--------~---------- M G 

M G Green sandstone at 

base of uranium-bearing sandstone . 

122 

123 

33-44-76 ILW-29 

LW-30 

LW-31 

IM-32 

LW-33 

LW-34 

LW-35 

LW-36 

33-44-76 ILW-28 

LW-37 

LW-38 

LW-39 

LW-40 

.003 

.019 

.036 

.014 

.092 

.027 

.032 

.007 

.020 

.015 

.10 

.031 

.029 

.002 

.003 

.009 

.003 

.008 

.003 

.010 

.006 

.022 

.004 

.053 

.026 

.004 

. 06 ~----------~-----------

.17 ---------- ----------- .18 ---------- ----------- .05 ---------- ----------- .07 ---------- ----------- .20 ---------- --------~-­ .06 ---------- ----------- .07 -----------

.13 ---------- -----------

. 08 

.24 

.12 

.12 ==========~=========== 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

R G 

-------- ---------- -------- ---------- -------------------

-------- ---------- -------- ---------- -------------------

!Samples taken at intervals along a hard 

sandstone concretion 

about 140 ft long. 

!

-------- ----------

R G !samples taken at in-

--------~----------

-------- ---------- -------- ---------- -------- ----------

tervals along a hard 

sandstone concretion 

about 220 ft long . 
m 

123 

124 

125 

126 

127 

128 

129 

130 

131 

132 

133 

134 

135 

136 

137 

138 

139 

140 

141 

142 

143 

144 

145 

146 

147 

148 

149 

150 

151 

152 

153 

154 

155 

156 

157 

158 

159 

160 

161 

162 

33-44-76 

14-43-76 

6-43-75 

3-44-75 

30-42-75 

35-42-77 

23-41-77 

7-44-75 

l-42-76 

29-43-75 

23-43-76 

34-43-76 

34-43-76 

34-43-76 

27-43-76 

14-43-76 

4-42-76 

20-42-76 

28-42-76 

15-42-76 

4-42-75 

34-43-75 

34-43-75 

34-43-75 

33-44-76 

28-44-76 

34-43-75 

36-43-76 

4-42-76 

36-45-76 

34-45-76 

6-43-74 

25-41-77 

8-43-77 

5-43-77 

12-42-76 

12-42-76 

13-4"3-76 

8-43-76 

14-41-77 

LW~41 

LW-42 

LW-43 

LW-65 

'IW-104 

'IW-103 

'IW-105 

'IW-125 

AEC-1066 

LW-106 

C-25313 

C-25316 

and 25317 

C-25314 

LW-99 

LW-89 

'IW-99 

LW-91 

LW-92 

LW-93 

LW-94 

LW-95 

LW-96 

See footnotes at the end of the table. 

.023 

.015 

.007 

.013 

8.5 

.017 

.029 

.44 

.306 

1.207 

.23 

.051 

.64 

.12 

.12 

.058 

.27 

.16 

. 10 

1.3 

2.8 

.002 

.004 

.002 

.006 

11.24 

.003 

.018 

.07 

.026 

.009 

.07 

.19 

.12 

.06 

1.99 

.04 

.oB 

.14 

.05 

.l 

.043 I .03 

.51 I .32 

.02 .05 

1.632 

.40 

.034 

.66 

.15 

.08 .18 

.063 .21 

.43 .72 

.16 ·75 

.16 .10 

.73 .75 

1.68 .l 

__________ f ____________ ---------- ------------ ---------- ------------ ---------- ------------

. 031~------------­

. 54 3 ------------ .038 37.3 Fe203 

.553 

s 

s 

c 

c 

s 

s 

s 

s 

s 

.02 1------------·1 s 

-----------32.8 CaCO 3 •---------

5.93 C02 

s 

s 

s 

s 

c 

s 

:~~5[~. ~~~~-~~=~:_. ~ .13 ------------· c 

.03 ------------ c 

.06 ------------ c 

.13 ------------· c 

. 05 ~------------1· s 

R 

R 

R 

M 

R 

M 

M 

R 

M 

R 

M 

M 

M 

M 

M 

M 

M 

R 

M 

R 

R 

R 

R 

M 

R 

R 

M 

M 

M 

M 

R 

R 

R 

M 

M 

u 

u 

u 

u 

u 

U ~ronstone. 

A 

A 

A 

u 

A 

A 

A 

A 

A 

A 

A 

A 

A 

A 

A 

A 

A 

A 

A 

G 

G 

u 

G 

u 

u 

u 

u 

G 

oil sample. 

ase of sandstone. 

Ironstone. 

Do. 

Do. 

2-ft sample. 

---------t--------]5-ft sample. -------- -------- 'Basal 2 ft of sandstone . --------- -------- 2-ft samples across deM 

M 

R 

R 

(} 

G 

u 

u 

posit. 

Ironstone. 
I-' 

0 

Table 1.--Localities of known uranium mineralization or anomalous high radioactivity, Pumpkin Buttes area, Wyoming--Cont. 

Locality I Location 1 

no. 

163 23-41-75 

164 5-43-77 

165 5-43-75 

166 4-43-75 

167 ll-45-75 

168 ll-45-75 

169 6-43-74 

170 6-43-74 

171 12-42-75 

172 12-42-75 

173 . 3-43-75 

174 16-45-74 

175 16-45-74 

176 16-42-75 

177 29-42-75 

178 29-42-75 

179 28-44-76 

180 23-44-76 

181 21-42-75 

182 14-44-77 

183 14-44-77 

184 14-44-77 

185 23-42-77 

186 8-43-77 

187 35-42-77 

188 25-45-76 

189 5-41-76 

190 12-42-75 

191 8-41-75 

192 ll-44-75 

193 8-43-77 

194 l-44-76 

195 10-44-75 

196 10-44-75 

197 2-44-75 

198 12-44-77 

199 9-43-77 

200 32-43-75 

Equiva- Field 

sample 

no. 

lent I Uranium I V205 I Mn 

uranium (percent) (percent) (percent) 

Other 

(percent) 

Kind of 

Type of ~ local- I Discovsample 2- ity3 erer 4 

TW-100 

TW-101 

TW-119 

LW-25 

(percent) 

0.057 

.oo8 

.22 

.051 

---;~;;8 ---;~;;--r----;~785~34~~~-;~:~~~----~---- . 000 .04 .134 ------------ s 

.010 .05 .628 ----------- c 

.004 .04 --------- ------------ s 

AEC-1085 -~=~g~---l-----:~~9-~----:g~~~---:~~--[-----:~~~~============[---~---- .06 .068 I .10 _________ t ____________________ _ ~; :(;)---J~----~;i7-[----~;;-]========= 

---------- ---------- -------- ---------

----------1---------- AEC-25380 .43 

AEC-25384 .15 

AEC-1080 .01 

1.05 

AEC-1065 .05 

AEC-1068 1.37 

-------- -------- --------- --------------------- .45 .37 --------- ------------ s 

.lll .13 --------- ------------ s ~ .03 --------- -------------- --- 1.01 .47 --------- ------------ s 

.oo8 .03 --------- --------------------- 1.95 1.42 --------- ------------ s 

3.21 4.87 2.39 --------- ------------ s ---------- -------- --------------------- ---------- -------- --------------------- ---------- -------- --------------------- ---------- -------- ----------- --------- ---------- -------- ----------- --------- ---------- -------- --------------------- ---------- -------- --------------------- ---------- -------- --------------------- ---------- -------- --------------------- ---------- -------- ---------------------- AEC-25401 .026 .009 Tr. ------------ S 

AEC-25402 .02 .10 Tr. ------------ S 

AEC-25400 .009 Tr. .06 ------------ S 

-------- ------------ -------- ---------- -------- ------------ -------- ___________ t _________ t --------

________ j ________ _ ------------ ---------

----------- --------- -------- --------- -----------

___________ t ---------_________ t --------_________ t --------- ________ t _________ t ____________ 

============t========~' t _______ _ ----------- --------~ -~---------------- --------- ------------ --------- ----------- --------- --------- -------- --------- ------------ ---------

R U 

R G 

R G 

________ M U l ________ _ M U 

M G 

M A 

R A 

R A 

R A 

M G 

M A 

M A_ 

M A 

M A 

M A 

R 

R 

R 

R 

R 

R 

R 

R 

R 

R 

R 

R 

R 

M 

R 

M 

R 

R 

R 

R 

R 

R 

G 

G 

A 

G 

G 

G 

A 

A 

A 

A 

A 

A 

A 

A 

A 

A 

A 

A 

G 

G 

A 

u 

Remarks 

Ironstone . 

~ost sandstone. 

~uger-hole sample. 
~ 

~ 

201 

202 

203 

204 

205 

206 

207 

208 

209 

210 

211 

32-43-75 

29-43-75 

25-43-75 

29-41-75 

28-43-75 

28-43-75 

28-43-75 

16-43-77 

3-43-77 

17-43-77 

8-43-77 

----------- ___________ ! --------- _________ ! ------------------

_________ !---- ----!---------!------------~-------- --------- ------------ -------- ----------- --------- --------- -------- --------- ------------ -------- ----------- --------- --------- -------- --------- ------------ -------- ----------- --------- --------- -------- --------- ------------ -------- ----------- --------- --------- -------- --------- ------------ -------- -----------~---------~---------~--------~---------~------------

-----------~---------~---------~--------~---------r------------~---------

===========t=========t=========t========t=========t============ --------- -----------~---------~---------~--------r---------~------------r---------

1See plate 2. Numbers indicate section, township·, and range. 2 Type of sample: C-channeled; S-selected. 3 R-Locality of high radioactivity but no uranium minerals observed; M-Locality of known uranium mineralization. 4 Locality discovered by: A-Atomic Energy Commission airplane; U-Geological Survey airplane; G-Geological Survey ground party. 

R 

R 

R 

M 

R 

R 

R 

R 

R 

R 

R 

u 

u 

A 

G 

G 

G 

G 

A 

A 

A 

A 
STRATIGRAPHY 

General statement 

Most of the area described in this report is underlain by the Wasatch formation of Eocene age. A thin 

band of Fort Union formation of Paleocene age crops 

out along the Great Pine Ridge escarpment in the southwestern corner of the area, and the White River formation of Oligocene age caps the Pumpkin Buttes. 

Fort Union formation 

The Fort Union formation is a sequence almost 

3, 000 feet thick, made up of gray, fine-grained sandstone, bluish-gray claystone, and coal beds. In the 

southwest part of the area and for some distance to the 

northwest and southeast, beds of coarse-grained, crossbedded sandstone in the upper part of the formation are 

expressed topographically by Great Pine Ridge. Some 

of the sandstone is ferruginous. The upper limit of the 

formation was arbitrarily placed by Wegeman, Howell, 

and Dobbin (1928) at the top of their coal bed H 

(see fig. 3); but G. Horn of the Geological Survey 

(personal communication, 1953) working in the vicinity 

of the Sussex oil field found that coal bed H occurs progressively lower in the section northwest of the Sussex 

oil field. R. K. Hose of the Geological Survey (personal 

communication, 1953) placed the Fort Union-Wasatch 

boundary at the base of the stratigraphically lowest red 

siltstone in the Crazy Woman Creek area northwest of 

the Pumpkin Buttes area and that practice was followed 

in the Pumpkin Buttes area. The upper 550 feet of the 

FortUnionformation measuredin NEt sec. 3, T. 42 N., 

R. 78 W. is illustrated in the composite stratigraphic 

section (fig. 3). 

Wasatch formation 

The Wasatch formation in the Pumpkin Buttes 

area consists of variegated claystone, relatively 

continuous thin beds of coal, carbonaceous shale, 

and thin-bedded sandstone and lenticular, crossbedded, medium- to coarse-grained sandstone (fig. 3). 

Vertebrate fossils collected during the summer of 

1952 established an early Eocene age for the major 

part of the Wasatch formation in the west-central 

Powder River Basin. No middle or upper Eocene 

rocks are recognized. 

The Wasatch formation in the Pumpkin Buttes 

area is about 1, 500 feet thick (fig. 3). The lower 

500 feet of the Wasatch formation were measured 

near Great Pine Ridge (SWt sec. 35, T. 43 N., 

R. 78 W.) and the upper 1, 000 feet were measured 

on North Pumpkin Butte (sees. 2 and 10, T. 44 N., 

R. 76 W. ) . The two parts of the composite section 

were connected by carbonaceous shale beds traced 

a distance of about 12 miles. 

The Wasatch formation is composed of approximately 3 parts of shale·, claystone, and siltstone to 1 part of sandstone. In overall aspect 

the Wasatch is lithologically a mudstone sequence 

interbedded with sandstone lenses. Reconnaissance 

by Davidson (1953) indicates in a preliminary way 

that fine-grained material is more abundant northwest of the Pumpkin Buttes area and coarse -grained 

material is more abundant southeast of the area. 

12 

Essentially all known uranium occurrences in the 

Pumpkin Buttes area are included in a predominantly 

red sandstone zone (fig. 1). The zone is about 450 feet 

thick in the line of the measured section, but at other 

places it is more than 500 feet thick. The sandstone in 

this zone typically is massive and crossbedded, mediumto coarse -grained, feldspathic, and friable to moderately 

well cemented; a few beds are tuffaceous. Lime-cemented 

concretions form "cannon balls," irregular masses, and 

elongate bodies 10 to several hundred feet long and 1 to 

6 feet in diameter. The long axes of most of the observed 

irregular masses and the elongate bodies are oriented 

in a northerly direction. 

Thin conglomerate beds within the sandstone are 

common. The pieces in the conglomerate are clay fragments as much as 2 inches in diameter. Fragments of 

plant material, either coalified or replaced by finegrained silica, are locally abundant. Some of the coalified material has been replaced by iron sulfide. 

Much of the sandstone in the uranium-bearing zone 

is colored various shades of red and brown by iron oxides, but the staining is not uniform, either stratigraphically or laterally, and gray and buff colored sandstone 

is common. Most of the sandstone units range from 

30 to 60 feet in thickness, but in places some are more 

than 100 feet thick. The sandsto!les transgress the 

section, interfinger with finer clastic material, and are 

lenticular. They are thought to be flood-plain and channel deposits. In some places the sandstone fills channels cut in Underlying beds of shale, mudstone, and siltstone, but in many places the sandstones grade laterally 

into finer grained sediments. Individual beds of sandstones range in extent from a few hundred yards to several miles. Not all of them are in the same stratigraphic position, but maybe correlatable in zones. Very 

few individual beds can be traced for any distance. Except for color, sandstones in the upper 650 feet of the 

Wasatch appear to be similar to those in ~he uraniumbearing zone. 

White River formation 

A basal remnant of the White River formation caps 

all the Pumpkin Buttes and is 30 to 75 feet thick. The 

formation, as represented here, is composed of very 

coarse-grained to conglomeratic sandstone made resistant by siliceous cement. Remnants of white and pink 

tuff and bentonitic claystone, a few feet thick, overlie 

the caprock in a few places. Vertebrate fossils collected by Love (1952) established the early Oligocene age 

of these strata. 

The White River formation overlies the Wasatch 

formation with an erosional unconformity marked by 

local channel filling. The pre-Oligocene surface was 

nearly horizontal in a northwest-southeast direction and, 

in the vicinity of Pumpkin Buttes, was cut on the underlying west and northwest low-dipping beds of the Wasatch 

formation. 

URANIUM DEPOSITS 

Almost all known concentrations of uranium occur 

in the sandstones of the uranium-bearing red sandstone 

zone 450 to 900 feet above the base of the Wasatch formation 

(fig. 3). The uranium occurrences are of two principal 

types: (1) Concretionary, orsmallirregularlyshaped 

concretionary masses of uranium, iron, vanadium, and 
Cap rock of Pumpkin Buttes 

t 2400'±. 

to base of Ttu 

~ 

pg 

~ 

illii] 

ENIT1 

F5:J 6±:3 

~ 

Ld 

~ 

m 

~ 

Em 

li 

Ill 

Ill 

II 

f""OI 

~ 

~ 

~ 

EJ . 

. 

EXPLANATION 

Conglomerate 

Coarse-grained to pebbly massive sandstone 

Fine- to medium-grained massive sandstone 

Crossbedded sandstone 

Calcareous sandstone 

Carbonaceous sandstone 

Si ltstone 

Claystone, bentonitic 

Claystone 

Shole 

Carbonaceous shale 

Coal 

Limestone 

Sandy limestone 

Calcareous sandstone 

concretions 

Limestone concretions 

Covered 

Red sandstone (commonly uranium bearing) 

150 

75 

50 

0 

vertica I scale in feet 

Figure 3. -Composite stratigraphic section of rocks, showing zone of principal uranium occurrence in the Pumpkin 

Buttes area, Wyoming. 

13 
A 

8 

Fractured grains of quartz (q) 

and plagioclase (p) and rock 

fragments, quartzite (qi) and 

shale (s) in calcite cement (c). 

Iron and manganese oxides (f -m) 

replace calcite in left part of field. 

Thin section TW -143. 

Similar to A., but iron and manganese oxides completely replace 

calcite cement and attack the 

allogenic mineral grains at left 

edge of field. At center and 

right, sheaflike aggregates of 

bladed uranophane ( u) replace the 

calcite, but not the iron-manganese 

oxides or the quartz or feldspar. 

Composite of thin section TW -140 

and two sections of TW -141, showing 

gradational changes in mineralization. 

Figure 4. -Sketches of thin sections from concretionary deposits, showing progressive stages of mineralization. 

Specimens from sec. 36, .T. 43 N., R. 76 W. 

14 
manganese minerals in sandstone. The uranium content of many of these concretions is very high. (2) Disseminated, or in irregular zones in which uranium minerals are disseminated in sandstone with little or no 

visible iron and manganese. Known deposits of this type 

are generally much larger but of much lower grade than 

the concretionary type. 

Uranium minerals were found at 121 of the 211localities shown on plate 2; above-normal radioactivity 

was detected either by airborne or ground equipment at 

the remaining 90 localities, but visible uranium minerals 

were not found. Ninety-six of the 121 occurrences are 

of the concretionary type, and 6 are of the disseminated 

type. Because of poor exposures the remaining 19 occurrences cannot be classified. 

The largest individual concretionary deposit found 

is about 10 feet in its longest dimension. The concretions tend to occur in groups. In some places half a 

dozen or so small concretions may be found in an area 

of a few tens of square feet. The density of distribution 

of the concretions at most places cannot be determined 

because of lack of exposures. Additional physical exploration is necessary to obtain data from which the 

frequency of occurrences of concretions in such areas 

can b8 predicted. Deposits of the disseminated type 

were discovered late in the field season of 1952 and little 

is known about them. The largest deposit is within an 

area of 100 by 800 feet and within a zone ranging in 

thickness from a few inches to 10 feet. Not all of the 

rock in this area is mineralized. 

l'vllNERALOGY 

The information to be presented now is based 

largely on the study of 10 thin sections cut from specimens collected at locality 119, sec. 36, T. 43 N., 

R. 76 W., a concretionary deposit. 

The sandstone at the deposit is a medium- to coarse 

grained friable sandstone that contains three types of concretions: those in which the sand grains are cemented 

and partly replaced by calcite, those in which the sand 

grains are cemented and partly replaced by both calcite 

and iron and manganese oxides, and those in which the 

sand grains are cemented and partly replaced by iron 

and manganese oxides. 

The second type contains more uranium than the 

other types, which commonly contain little or no uranium. Many of the uranium-bearing concretions exhibit 

a crude concentric banding of alternating but discontinuous zones of black, brown, and yellow mineralization 

and barren or only slightly mineralized sandstone. The 

three types seem to represent successive stages in the 

mineralization of the sandstone, and all gradations exist 

among the three types. A description of the unmineralized sandstone and of the successive changes produced 

by the development of the various types of concretions 

follows: 

Subangular to subrounded quartz grains are the dominant constituent (40-60 percent) of the nonconcretionary 

sandstone. Plagioclase (andesine and oligoclase) and 

microcline constitute about 5 to 10 percent of the rock. 

Most of the feldspar is remarkably fresh and clear, but 

a few grains in every section are badly altered to sericite or allophane or both. Accessory detrital minerals 

15 

include epidote, biotite, muscovite, garnet, tourmaline, 

chlorite, sphene, and zircon. 

\_ 

The rock is poorly sorted and much of the space 

among mineral grains is taken up with fine fragments of 

shale, which constitute an estimated 15 to 20 percent of 

the rock. Calcite cement fills the interstices. 

The sandstone of the concretions is well sorted and 

cleaner, having relatively few shale fragments. This 

suggests that the development of concretions may be correlated with greater permeability. The quartz and feldspar grains in the calcite concretions (first type) are 

commonly ruptured, and the cracks and breaks healed 

with calcite which both fills the fractures and replaces 

the quartz and feldspar (fig. 4~). Some of the plagioclase 

has been replaced along cleavage cracks. The cause of the 

fractures is unknown, but few sand grains in specimens that 

were not taken from concretions show this feature. 

The uranium-bearing concretions (second type) are 

similar to the calcite concretions except that calcite has 

been partly replaced by iron and manganese oxides, and 

at a later stage by uranophane and minor amounts of a 

carnotite-tyuyamunite( ?) mineral. Replacement of calcite by iron and manganese oxides begins along ~he grain 

boundaries. This stage is illustrated in the left part of 

figure 4.§:.. As replacement proceeds, the selvages of 

iron and manganese oxides surrounding the grains thicken, 

and irregular spots or islands of these minerals develop 

in the interstitial calcite. Finally the calcite cement is 

completely replaced, and the quartz and feldspar grains 

are attacked. This stage is shown in the left part of 

figure 4£, and resUlts in the type of concretion which 

contains little uranium. 

Uranophane does not develop in the absence of the 

iron and manganese oxides, but in the sections studied, 

it does not replace either the iron and manganese oxides 

or the relict mineral grains; apparently some calcite 

must be present ·as a site for replacement. If some calcite cement remains, then uranophane may develop. This 

stage is shown in the central and right parts of figure 412_. 

Bladed aggregates of uranophane wrap around the larger 

grains of quartz and feldspar, but do not replace them; 

small grains of quartz and islands of iron-manganese 

oxides are completely enclosed by the uranophane without 

disturbing the orientation of the individual uranophane 

crystals (fig. 412.). The uranophane fibers extend into the 

calcite, but end abruptly against the quartz grains or 

against the iron-manganese oxide selvage which surrounds 

some of the grains. 

The significance . of the associ.ation of uranium and 

the iron and manganese oxides is unknown. In a few 

places the opaque material exhibits rectangular outlines 

suggesting that some of it may be pseudomorphic after 

pyrite. This feature is shown at the border of the black 

mineralization near the top of figure 412_. 

Thin sections of specimens from other concretionary 

deposits, from disseminated deposits, and from areas 

in which there are no known deposits are not yet available for study. X-ray analyses indicate that the dominant uranium mineral in the unclassified type of deposits 

at locality 3 and at a locality in sec. 9, R. 73 W., T. 37N., 

about 25 miles south of the Pumpkin Buttes area, is metatyuyamunite. Richard Kellagher (personal communication) 

has reported manganosite (MnO) from locality 92, sec. 28, 

T. 43 N., R. 75 W. M. E. Thompson (Weeks, 1952) has 
' \ 

I 

\ 

\ 

R.77W. R.76W. 

···u-t-···~ _j" 

/ ,, 

!\ 

North Butte 

~ 

"-/1. 

I 

"' .·.~+···~ 1>- ·.·\..... .. 

,~ ·~ ... 

,g 

"""' ···--............ 

R15W. 

Middle Buttes 

~ \ ... ..---

D 

South Butte 

:_n. ··~ 

CAMPBELL COUNTY 

----...- _,..-. 

Boundary of area of principal 

occurrences of uranium 0 

I 

2 

R14W. 

I 

T. 

4 

N. 

T. 

43 

N. 

n Pine Tree T. 

ll 42 

H N. 

'"~~ ",~,, 

'\\\ 

II 

,, 

,~, 

II 

\\ 

~I 

e Miles 

II 

\I 

\, T ,, 4i 

II N. II 

II 

II 

~" ..... ~, 

Figure 5. -Map showing area of principal occurrences of uranium in the Pumpkin Buttes area, Wyoming. 

16 
identified liebigite (Ca 2U(C0 3 )4.10H20) from locality 29, sec. 4, T. 42 N., R. 76 W. The mineral occurs as a yellow -green efflorescence at a 

small water seep in sandstone exposed in a steeply 

cut bank. 

The mineralized concretions at locality 31 

contain the usual iron-manganese oxides in association with both orange and yellow uranium minerals. 

The orange mineral has been identified by X-ray 

as carnotite; the yellow material is a mixture of 

carnotite and an unidentified mineral. 

LIJvllTS OF KNOWN PRJNCIPAL URANIUM 

JvllNERALIZATION 

The area containing the principal known occurrences of uranium in the Pumpkin Buttes area is 

shown on figure 5. North and northwest of this 

area the sandstones of the uranium-bearing zone 

have not been recognized and may have either been 

removed by erosion or grade laterally into claystone, shale, and siltstone. The attitude of the 

' beds and surface elevations indicate that east of 

R. 73 W. and west of R. 77 W. the rocks exposed 

are stratigraphically below the uranium-bearing 

sandstone zone of the Wasatch formation. Anomalous radioactivity detected in siltstones., ironstones, 

and in one or two locally coarse-grained sandstones 

west of the favorable area is not associated with 

visible uranium mineralization. 

The southe rn limit of the area favorable for 

uranium deposits is still open to question. The area 

extending about 6 miles south of State Highway 387 

has been examined on the ground by reconnaissance methods and by Geological Survey and Atomic 

Energy Commission airborne scintillation detectors. 

Only one radioactivity anomaly was found. In November 1952, an Atomic Energy Commission plane 

discovered radioactivity anomalies at 3 localities 

16 to 25 miles south of the area of this report. These 

three points were examined on the ground in February 1953 and a concretionary deposit was found at one 

locality. No uranium minerals are visible at the other 

two localities, but both show above-average radioactivity over 200 to 300 square yards. Since these 

three discoveries, other deposits have been found in 

the same vicinity by independent geologists. 

17 

GUIDES TO PROSPECTING 

Three features which the writers feel will be helpful in the search for new deposits in the Pumpkin Buttes 

area are: 

1. All uranium deposits of ore grade (0.1 percent 

or more uranium) are in sandstones of the red sandstone 

zone 450 to 900 feet above the base of the Wasatch formation. Most of the known deposits are in iron-stained 

sandstone or in gray- to buff-colored sandstone that is 

closely associated, either laterally or vertically, with 

iron-stained sandstone. The red sandstones and the soil 

derived from them photograph darker than the unstained 

sandstone, and it appears that the darker areas representing red sandstones shown on the aerial photographs 

are generally favorable for uranium mineralization. 

Many of the concretionary deposits were discovered by 

noting the color contrast between dark colored iron and 

manganese oxides and the host sandstone. 

2. Most of the concretionary deposits occur in 

clusters. If one concretion is found, a thorough search 

should be made in the immediate vicinity for additional 

concentrations of uranium minerals. 

3. Water samples from shallow wells and springs 

in the vicinity of known deposits contain as much as 

50 times the amount of uranium present in water from 

wells in areas where no uranium deposits are known. Only 

a few analyses are available, but systematic sampling of 

water from wells and springs may prove helpful in finding new deposits. 

LITERATURE CITED 

Love, J. D., 1952, Preliminary report on uranium 

deposits in the Pumpkin Buttes area, Powder River 

Basin, Wyoming: U. S. Geol. Survey Circ. 176. 

Wegeman, C. H., Howell, R. W., and Dobbin, C. E., 

1928, The Pumpkin Buttes coal field, Wyoming: 

U. S. Geol. Survey Bull. 806. 

UNPUBLISHED REPORTS 

Davidson, D. F. , 1953, Distribution of coarse- and 

fine-grained rocks in the Wasatch formation and 

their relationship to uranium deposits, Powder River 

Basin, Wyoming: U. S. Geol. Survey Trace Elements 

Memo Rept. 676. 

Weeks, A. D., 1952, Summary report on mineralogic 

studies of the Colorado Plateau through April 30, 1952: 

U. S. Geol. Survey Trace Elements Memo. Rept. 431. 

INT.-DUP. SEC., WASH., D.C 69~ 27 
CHICIJUM .. l'lATt I 

105. 45'()0'" UNITED STATES DEPARTMENT Of THE INTERIOR 

GEOLOGICAL SURVEY 

~f~~~~~~~~----~~~----~--~~--~~----.---~ T¥~ --~r-~~~~~r---~--~--~~~---------- ~ 

\ 

i<Y.I 

GEOLOGIC MAP OF THE EAST-CENTRAL PART OF THE PUMPKIN BUTTES AREA , CAMPBELL COUNTY, WYOMING 

EXPLANATION 

lt . Whlte Rlver~on. Caproek aandatone on P umpkin Buttes 

D San~to.ne• of the Waaat ch format10n 

wlthln the area o! sandstone mappl.ng. 

Medium- to c:oa rae-grained aanda-tone, 

with aome conglomerate lenses: in 

l place a aanda:tone lnclude thin beda of 

j ahale and eUtatone 

c Wasatch forautton exclusive o! I sandstonee withm area of sa.nd· 

atone mapping. Includes enunone, 

claystone, shale, c arbonaceous 

shale. and coa.l of the Wasatch 

l formation. and aUuv tum J 

Contact, duhed where approx.lrnatel,y 

louted; dotted wherto mferred or covered 

ra.au:rn ltmH o( sa.ndltone mappm& 

Boundary of areu outside area of 

aaodatone mapping moat favorable 

for the occurr ence of ura.nlum 

miner a lh:alion. Dashed where 

approximately located wu;, 

hachurea nn more favorable a 1de 

of boundary 

Localhlea conta.ining radioactive ma.teraa 

I 

Section linea and corners whe re 

approximately located. Oaahed 

where no comrol avail able 

l 

4$ 

• 
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY 

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............. ( "i / 9~ ~ I~ 134 6 ·. _....& ... :--{ I <'6 202 L 93 ..--

_....... ... / 

/60 J -------

0 2 Miles 

1{1 Fd Wh;te R;w fo•mot;on ~ 

! {G Wasatch formation ~ w j {~ Fort Union formation 1-

~ 

EXPL ANATION 

__.-...-""--- Geologic contact 

Dashed where approximately located 

-........_ Fau lt 

Dashed where inferred 129 

Geology by M. L . Troyer, E. J . McKoy, 

S. R. Wallace, and P. E. Soister 

Synclin al ax is of Powder River Basin 

Approximately located 

Localities showing visible uranium minerals 

Localities showing anomalous radioactivity but no visi ble uranium minerals 

Locality number (See table I ) 

GEOLOGIC MAP SHOWING LOCALITIES OF URANIUM MINERALIZATION IN PUMPKlN BUTTES AREA, WYOMING