Uranium in Black Shale 

Deposits, Northern 

Rocky Mountains and 

Great Plains

GEOLOGICAL SURVEY BULLETIN 1030-H

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

Uranium in Black Shale 

Deposits, Northern 

Rocky Mountains and 

Great Plains

By W. J. MAPEL

CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

GEOLOGICAL SURVEY BULLETIN 1030-H

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 GOVERNMENT PRINTING OFFICE, WASHINGTON : 1956
UNITED STATES DEPARTMENT OF THE INTERIOR 

Fred A. Seaton, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U. S. Government Printing Office 

Washington 25, D. C. - Price 55 cents (paper cover)
CONTENTS

Page

Abstract_________________.______________________ 211

Introduction._____________________________________________________ 211

Purpose and location_________________________________________ 211

Acknowledgments.-____ _____________________________________ 213

Field work and use and interpretation of the gamma-ray logs._________ 213

Summary of the results of the investigation._________________________ 215

Descriptions of selected black shale deposits._________________________ 219

Black shale at the base of the Madison limestone and equivalents. _ _ 219

Black shale at the base of the Brazer limestone....________________ 230

Heath shale__________________________________ 230

Literature cited___________________________________________________ 233

Index. ___._____-_-_-____________________._______ 235

ILLUSTKATIONS

[Plates 14 and 15 in pocket.]

PL.AT.E 14. Index map showing black shale localities examined for uranium, northern Rocky Mountains and Great Plains. 

15. Map and sections showing thickness and radioactivity of the 

Bakken formation (as used by Kordquist, 1953), northern 

Great Plains. Page 

FIGURE 51. Locations of selected wells for which gamma-ray logs were

studied____________________________________________ 214

52. Sections showing uranium content of basal black shale of 

Mississippian age at outcrops in the northern Rocky 

Mountains region.__________________________________ 229

53. Sections showing uranium content of black shale at the base of

the Brazer limestone, Utah and Idaho __________________ 231

54. Thickness and distribution of the Heath shale in central 

Montana and the Heath shale and Otter formation in 

eastern Montana and adjacent parts of North and South 

Dakota.______________________________ 232

TABLES

Page

TABLE 1. Selected wells in northern Great Plains for which gamma-ray

logs were studied_____-_-_-_____-_---_-_____-___-------- 216

2. Radioactivity of formations containing black shale in selected

oil and gas wells, northern Great Plains.__________________ 217

3. Analytical data and outcrops examined.____________________ 220

m

CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

URANIUM IN BLACK SHALE DEPOSITS, NORTHERN 

ROCKY MOUNTAINS AND GREAT PLAINS

By W. J. MAPEL

ABSTRACT

Reconnaissance examinations for uranium in 22 formations containing black 

shale were made in parts of Montana, North Dakota, Utah, Idaho, and Oregon in 

1953. About 150 samples from 80 outcrop localities and 5 oil and gas wells were 

submitted for uranium determinations. Most of the black shale deposits 

examined contain less than 0.003 percent of uranium; however, thin beds of black 

shale at the base of the Mississippian system contain 0.005 percent of uranium 

at 2 outcrop localities in southwestern Montana and as much as 0.007 percent 

of uranium in a well in northeastern Montana. An 8-foot bed of phosphatic 

black shale at the base of the Brazer limestone of middle and late Mississippian 

age in Rich County, Utah, contains as much as 0.009 percent of uranium.

Commercial gamma-ray logs of oil and gas wells drilled in Montana and adjacent 

parts of the Dakotas indicate that locally the Heath shale of late Mississippian 

age contains as much as 0.01 percent of equivalent uranium, and black shales of 

Late Cretaceous age contain as much as 0.008 percent of equivalent uranium.

INTRODUCTION

PURPOSE AND LOCATION

A reconnaissance search for uranium in black shale in the northern 

Rocky Mountains and Great Plains regions was carried out during the 

summer of 1953 by the U. S. Geological Survey on behalf of the 

Division of Raw Materials, U. S. Atomic Energy Commission. The 

work is part of a continuing program to investigate the uranium 

possibility of untested or incompletely tested black shale deposits* in 

the Western States. Most of the localities visited are in southwestern 

and central Montana, central and southeastern Idaho, and northwestern Utah. About 150 gamma-ray logs from wells drilled for 

oil and gas in Montana and adjacent parts of North and South

211
212 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

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URANIUM IN BLACK SHALE DEPOSITS 213

Dakota were scanned for anomalous radioactivity, and samples of 

drill cores or cuttings from 5 of the wells were submitted for uranium 

determinations. Plate 14, the index map, shows the localities visited, 

and the table above shows the formations examined.

Previous work by Duncan (1953) indicated that the Heath shale of 

late Mississippian age and a thin black shale sequence of early Mississippian age called variously the Bakken formation (as used by 

Nordquist, 1953), the shale of Kinderhook age, or the Exshaw formation (Warren, 1937) at some places contain abnormally large amounts 

of uranium. Particular attention was given to a systematic sampling 

of these formations in an attempt to define areas of maximum or 

minimum radioactivity which might then be related to facies changes, 

source areas, thickness, or other factors that reflect environments of 

deposition.

Black shale of the Phosphoria formation of Permian age is known 

to contain uranium in the northern Kocky Mountains region, but it 

was excluded from the study because it has been sampled extensively 

as part of a separate investigation by the Geological Survey.

ACKNOWLEDGMENTS

The present investigation is a continuation of previous reconnaissance studies made at various times since 1951 in the Rocky Mountains region, as reported by Duncan (1953).

D. C. Duncan, R. J. Ross, J. E. Smedley, R. P. Kunkel, P. W, 

Richards, and H. D. Hadley supplied samples of black shale or guided 

the writer to exposures of shale in Utah and Montana. W. J. Hail, 

Jr., compiled information from the gamma-ray logs and assisted in 

interpreting the results of this work. Radiometric and chemical 

analyses listed in this report were made in Geological Survey 

laboratories.

FIELD WORK AND USE AND INTERPRETATION OF THE 

GAMMA-RAY LOGS

Outcrops of black shale described in the geologic literature or in 

unpublished reports available to the writer were examined for radioactivity at about 80 localities. Estimates of radioactivity were made 

in the field using a portable scintillation detector or a Geiger counter;. 

At most of the localities, representative samples of the formation 

were collected for uranium determinations regardless of the observed 

radioactivity. At a few localities, however, only those parts of the 

formation which showed appreciable radioactivity were sampled.
214 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

Roads between outcrops were traversed with a car-mounted scintillation counter, and those areas with higher than average background 

were examined on foot with the portable instruments.

The examination of gamma-ray logs of wells drilled for oil or gas 

provides a convenient means of evaluating the uranium possibilities 

of many black shale formations which otherwise might be difficult to 

test because of poor natural exposures or broad outcrop areas. Gott 

and Hill (1953), in a study of commercial gamma-ray logs of uncased 

wells drilled in the Rangely field, northeastern Utah, found that, on 

the average, a 1-inch deflection of the Lane Wells gamma-ray curve 

at a 10-inch sensitivity scale is caused by about 0.0007 percent of equivalent uranium. They pointed out that variations hi this value might 

be caused by such factors as the ratio of thickness to grade of the bed 

tested, the fluid content of the well, the shielding effect of casing in 

cased wells, differences in individual logging instruments, and the 

rate of movement of the ionization chamber. The calibration, therefore, is only approximate, but it gives some measure of the order of 

magnitude of radioactivity of the formations penetrated, and it is 

useful in comparing the radioactivity of the rocks from place to place.

Tables 1 and 2 list 15 wells drilled hi Montana and the Dakotas 

and indicate the average and maximum deflections on the gamma-ray 

logs of formations containing significant amounts of black shale. The 

locations of these wells are given in figure 51. Gamma-ray logs of

c A N A D A

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FIGTTEE 51. Locations of selected wells for which gamma-ray logs were studied (table 1).
URANIUM IN BLACK SHALE DEPOSITS 215

other wells examined but not listed in tables 1 and 2 show comparable 

radioactivity values.

SUMMARY OF THE RESULTS OF THE INVESTIGATION

Uraniferous deposits of black shale thus far found in the northern 

Rocky Mountains and Great Plains regions are either deeply buried 

and inaccessible, or they are too thin or of too low grade to be of 

value at this time as a source for uranium. Only a few of the deposits 

contain more than 0.003 percent of uranium. Of these few, beds of 

black shale at the base of the Madison limestone of early Mississippian 

age contain 0.005 to 0.007 percent of uranium at three localities in 

Montana and one in North Dakota (Iocs. 43, 44, 82, and 85, pi. 14), 

and 4 feet of a bed of black shale 8 feet thick at the base of the Brazer 

limestone of middle and late Mississippian age contains 0.009 percent of 

uranium at one locality in Rich County, Utah (loc. 30). The analyses 

of samples collected at these and other localities are listed in table 3.

The evaluation of gamma-ray logs of oil and gas wells, as shown by 

table 2, suggests that the Heath shale of late Mississippian age locally 

contains 0.009 percent of equivalent uranium or more in Musselshell 

and McCone Counties, Mont., and that the Colorado and Pierre 

shales of Cretaceous age contain as much as 0.008 percent of equivalent 

uranium in Blaine County, Mont., and in Perkins County, S. Dak., 

respectively. No drill cores or cuttings from these wells were available for analyses, and so the actual uranium content of the shale is 

unknown.
216 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

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URANIUM IN BLACK SHALE DEPOSITS 217

TABLE 2. Radioactivity of formations containing black shale in selected oil and 

gas wells, northern Great Plains

Well no. 

(fig. 51) Rock unit

Depth (feet)

From To 

Thickness of 

unit 

(feet)

Gamma-ray

defle Jtion.

converted to 

sensitivity of 

10 (inches)

Average

MaxiDepth in 

well of 

maximum 

deflection 

(feet)

Estimated 

maximum eTJi 

(percent)

Cretaceous rocks

1

2

4

5

6

7

9

11

12

13

14

Pierre _______

Greenhorn ______

Belle Fourche ..........

Skull Creek............

Cloverly ...............

Colorado _______

KootenaL. ............

Claggett . ...........

Eagle

Colorado _______

KootenaL- ............

Pierre . ..............

Niobrara _______

Greenhorn .............

Carlile .

Belle Fourche .......

Mowry ._.._.__...._...

Muddy and Skull 

Creek, undivided .... 

Cloverly ...............

Colorado _______

Colorado ..........

Kootenal ..............

Colorado _______

Kootenai ..............

Claggett and younger. . 

Eagle _________

Niobrara _ . ___ , ....

Frontier and Mowry, 

undivided.. .........

Skull Creek....... .....

Kootenai _ ...........

Claggett.-.. ...........

Eagle -.........-.-.-...

Greenhorn .............

Belle Fourche ____ .

Kootenai ..............

Eagle.- ________

Greenhorn and Belle 

Fourche .............

Bow Island (of Perry, 

1937).................

Greenhorn, Belle 

Fourche, and Mowry. 

Skull Creek .........

200

2,160

2,788

2,915

3,460

3,710

3,850

1,117

3,032

0

396

807

2,577

1,135

2,368

| 2,928

I

3,705 

3,945

200

1,484

0

1,030

0

2,449

0 

955

1,390

1,842

2,617

2,764

1,525

1,950

2,150

3,050

3,250

3,430

3,900

880

1,550

2,020

2,503

3,105

600

2,560

3,044 

3,605

3,853

2,160

2,788

2,915

3,460

3,680

3,850

4,100

2,952

3,273

396

807

2,472

2,903

2,368

2,928

3,705

3,945 

4,365

1,426

1,990

1,030

1,602

2,449

2,724

955 

1,390

1,842

2,585

2,764

3,148

1,950

2,150

3,050

3,250

3,430

3,590

4,094

1,550

2,020

2,503

3,105

3,737

2, 560

3 044

3,605 

3,853

4,037

1,960

628

127

545

220

140

250

1,835

241

396

411

1,665

326

1,233

560

777

240 

420

1,226

506

1,030+

572

2,449+

275

955+ 

435

452

743

147

384

425

200

900

200

180

160

194

670

470

483

602

632

1,960

484

561

248

184

3.0

3.7

3.6

3.7

3.1

3.4

2.6

4.8

2.3

3.0

4.1

4.9

3.1

2.2

3.0

3.3

3.0 

2.4

5.0

3.2

2.7

2.2

6.0

4.4

2.0 

3.5

4.0

3.3

3.5

3.0

2.7

3.0

3.4

3.7

4.1

3.7

3.4

3.4

4.6

5.1

5.1

4.2

4.8

5.0

6.2

0.8

4.7

4.8

5.7

4.7

5.7

4.9

4.0

3.7

7.3

8.0

5.1

5.7

8.0

5.0

3.4

4.5

5.8

4.0 

4.3

8.2

6.0

4.5

4.5

10.9

6.7

3.3 

4.2

6.7

5.9

4.2

5.7

6.1

3.6

5.7

5.8

6.6

5.4

4.4

4.6

6.5

7.7

7.4

6.0

11.0

8.5

10.0 

9.2

6.7

1,899

2,210

2,860

3,335

3,540

3,811

3,908

2,161

3,151

319

805

1,629

2,738

2,255

2,900

3,469

3,935 

3,955

6412

1,890

200

1,331

1,183

2,498

1,319

1,405

2,029

2,699

2,881

1,858

2,019

3,038

3,246

3,348

3,525

3,929

1,388

2,460

2,760

2,800

3,488

2,212

2,560

3,480 

3,610

3,872,3,895

0.003

.004

.003

.004

.003

.003

.003

.005

.006

.004

.004

.006

.004

.002

.003

.003 

.003

.00&

.004

.003

.003

.008

.005

.002 

.003

.004

.004

.003

.004

.004

.003

.004

.004

.005

.004

.003

.003

.005

.005

.005

.004

.008

.006

.007 

.006

.003

' 1-inch deflection=0.0007 percent eU on 10-inch sensitivity scale.
218 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

TABLE 2. Radioactivity of formations containing black shale in selected oil and 

gas wells, northern Gr'eat Plains Continued

Well no. 

(fig. 51) Rock unit

Depth (feet)

From To 

Thickness of 

unit 

(feet)

Gamma-ray

deflection,

converted to 

sensitivity of 

10 (inches)

Aver- MaxiDepth in 

well of 

maximum 

deflection 

(feet)

Estimated 

maximum eTJi 

(percent)

Jurassic rocks

1

2

4

5

6

10

11

12

13

14

Morrison ..............

.....do... ...............

 do.. ..........

 do-,...... ..

 do.....

 do.. . .

.....do....... ..........

. .do.................

 .do..... ........

 do4,100

1,990

4,365

5,600

3,148

4,315

3 717

4,037

4,180

3,473

3,120

2,245

4,405

6,002

3,162

4, 655

3,760

4,116

80

200

217

255

40

402

14

340

00

7Q

3.6

3.3

3.1

3.8

1.8

3.4

3.3

3.7

2.7

5.3

6.6

8.5

4.7

6.4

2.4

4.1

3.7

3.9

3.1

6.2

4,118

3,400

2,922

2,239

4,400

5,661

3,155

4,491

3,738

4,088

.005

.006

.003

.004

.002

.003

.003

.003

.002

.004

Mississippian and Pennsylvania!! rocks

Minnelusa______.

Amsden.....____.

Big Snowy group......

Amsden of local usage..

Heath_..............

Amsden of local usageHeath..................

Amsden of local usage..

Heath.................

Minnelusa___._.

Amsden_______.

Big Snowy group__.

Heath............

Otter....__._.__.

Amsden.___.___.

Heath and Otter formations, undivided..

Amsden._______.

Heath and Otter formations, undivided..

Bakken (as used by 

Nordquist,1953)_ .

Big Snowy group__.

Englewood_____.

Heath and Otter formations, undivided..

Bakken (as used by 

Nordquist, 1953).....

5,700

5,870

6,070

4,017

4,233

3,550

3,747

3,604

3,976

5,820

6,230

6,374

2,817

3,050

5,650

5,755

6,996

7,437

4,940

5,182

6,495

6,900

9,613

5,870

6,070

6,372

4,233

4,325

3,747

3,800+

3,976

4,622

6,230

6,374

7,118

3,050

3,395

5,755

5,990

7,437

7,929

4,976

5,432

6,570

7,340

9,721

170 

200 

302 

216

92 

197

53+ 

372 

646 

410 

144 

744 

233 

345 

105

235

441

492

36

250

75

440

108

3.1 

2.7 

2.9 

1.3 

2.7 

2.2 

3.2 

2.4 

3.0 

1.8 

1.8 

2.7 

3.0 

3.0 

2.3

2.5 

2.3

2.9

5.8

5.8 

6.0

4.6 

9.0

7.1 

5.3 

4.0 

4.8 

4.7 

4.3 

5.9 

8.5 

12.7 

3.6 

3.6 

7.5 

6.6 

8.4 

4.7

15+5, 

5.7

9.5

8.9

9.0 

8.8

7.8

5,870

5,903

6,118

4,136

9,280

3,558

3,750

3,930

4,045

6,227

6,356

6,550

2,940

3,169

5,745

5.767, 5,775

7,304

7,529

4,971

5,358

6,504

7,005 

13+9,625, 9,700

Devonian rocks

7

8

13

14

15

Three Forks ...........

.... .do ..............

 do... . 

Devonian, undiflerentiated.. _ .

Qu'appelle group (of 

Baillie, 1953) 

2,780

7 oqn

4,976

6,570

9,724

3,130

8 030

5,030

6,822

9,916

350

100

54

252

192

1.5

4.8

5.1

3.7

3.7

6.3

6.2

6.9

8.0

6.0

3,006

7,972

5,008

6,715

9,798

.004

.004

.005

.005

.004

Ordovician rocks

5

13

14

15

Winnipeg (upper part).

 do.... _ . ___ ...

 do. 

.... .do...... .... .......

9,520

6,285

9,527

13,395

9,662

6,312

9,666

13, 562

142

25+

139

167

7.8

9.2

6.6

6.3

10.6

10.0

10.4

8.0

9,535

6,309

9,635

13,453, 13,466

.007

.007

.007

.004

11-inch deflection=0.0007 percent eTJ on 10-inch sensitivity scale.
URANIUM IN BLACK SHALE DEPOSITS 219

DESCRIPTIONS OF SELECTED BLACK SHALE DEPOSITS

BLACK SHALE AT THE BASE OF THE MADISON LIMESTONE AND

EQUIVALENTS

A black shale sequence of early Mississippian (Kinderhook) age, 

which ranges in thickness from a few inches to as much as 100 feet, 

occurs locally at the base of the Madison limestone or its equivalents 

in southwestern and central Montana and in the Williston basin of 

Saskatchewan, Manitoba, Montana, and the Dakotas. The term 

"Bakken formation" has been used to identify this unit in the subsurface 

in the Williston basin, where it is described by Nordquist (1953, p. 72) 

as mainly "two thin highly radioactive black shales separated by a 

grey calcareous sandstone, siltstone, or dolomite." According to 

Nordquist, the upper shale unit may be correlative with a bed of 

black shale, a few inches to 30 feet thick, which occurs at the base of 

the Madison or Lodgepole limestones in various parts of southwestern 

Montana and Utah. The lower shale and medial sandstone-dolomite 

units may correlate with the Sappington sandstone as used by Holland 

(1952), a shale and sandstone sequence as much as 60 feet thick, 

which occurs below the Madison limestone in parts of southwestern 

Montana. In southern Canada, equivalents of the basal shale unit 

and medial sandstone-dolomite unit of the Bakken formation, as used 

by Nordquist (1953), are regarded by him to correlate respectively 

with the Exshaw shale (of Warren, 1937) and the basal sandstone of 

the overlying Banff formation (of McConnell, 1887). In most parts 

of the northern Rocky Mountains region, the Bakken formation (as 

used by Nordquist, 1953) and its equivalents unconformably overlie 

the Three Forks or Jefferson formations of Late Devonian age, and 

they are conformably overlain by limestone of the Madison or Lodgepole formations, or McConnell's Banff formation, all of early Mississippian age.
TABLE 3. Analytical data and outcrops exam

[n. d. c., not determined chemically]

Locality no. 

(pl. 14)

Location (Sec., T., R.) Rock unit

Laboratory 

sample 

no.

Equivalent 

uranium 

(percent)

Uran

(perc

Frecambrian rocks: Idaho

4

5

6

7

8

9

25-46N-2W.

27-48N-2W. 

21-49N-1W..... --.. . - ..,

3 and 4-48N-3E. 

12-49N-4E..... .....................

14-49N-5E. .............. ...... .....

.....do....... 

... ..do ..... .... . ... 

.... .do.... ... ... ...

 ..do....... 

 .do... 

98503

98506

0.001

0)

0)

(0

.002

(n. d

(n. d

Frecambrian rocks: Montana

32

33

48

49

22-14N-4W. 

36-13N-6W...... ... .......... .......

30-7N-4E. 

20-7N-5E.... ..._.... .........

... ..do-.. ... ... .

 ..do ... 

94788

94150

94161

94162

0.002

.001

.002

.004

(n. d

(n. d

(n. d

Ouster County._.., 

SWJ4-16-13N-18E.

Bear Lake County.

12-138^42'E. 

Oneida County....

35-14S-36E.

Cambrian rocks: Idaho

Garden Creek phyllite 

.. do........ - .

Spence shale..... -. 

 .do... .

97044 0.003 (n. d

97045 .003 (n. d

97024 .002 (n. d

97023 .002 (n. d

97042 .003 (n. d

97043 .003 (n. d
Cambrian rocks: Utah

25

28

Cache County.. ___________ -

10-14N-2E. 

SWJ4-4-11N-4E. .-.. _..._..-.- ..do.. . _ . --... _.

97039

97040 

97041

Q7AQQ

0.003

.001 

.002

f\f\K

(n. d

(n. d

0

Cambrian rocks: Montana

39 

46

NWJ4-14-3S-5W. 

Broadwater County. , _____ .

22-5N-1W.

97012 

94790

0.005 

.002

0

(n. d

Ordovican rocks: Idaho

12 

13

14 

15

NEJ4-28-11N-17E. 

5-11N-17E. ...__ _ .

SW^-24-10N-17E. 

Unsurveyed 15 miles northeast of 

Ketchum.

Saturday Mountain formation. . . 

.....do . ....-.. ..

97046

97047 

97052 

97053

0.003

.003 

.003 

.003

(n. d

(n. d

(n. d

(n. d

Ordovician rocks: Utah 

26 

27

NWJ4-5-14N-4E. 

NEU-18-12N-3E... ................. .....do.... ........................

97026 

97024 

97031

0.004 

.004 

.003

0

> Not sampled.
222 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

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36

37

38

40

41

42

43

43

44

61

64

65

78

79

80

81 

82

NEM-5-7N-12W....... .............

SWJi-4-7N-12W............ ........

NEM-34-9S-8W.

NEM-13-3S-5W.

NWM-16-1N-2W.

11-11&-3E. 

SWM-26-2N-2E. ...................

.......do...............................

8EJ£-2-2N-2E_......___ . _._._.

9-13N-17E. 

SWJ£-8-12N-18E._ _-_.______ .

32-12N-19E. ....... .................

5-25N-24E. 

2-26N-24E.. ........................

22-26N-25E. ........................

Daniels County, SW>/4-12-36N-47E 

(Carter-Danielson well 1).

Roosevelt County, NEi/i-2-28N-51E,

(Murphy and others-East Poplar 

welll).

.....do-...-.-.-.. ___... __

..... do............ ................

-.-do......... ...................

.....do............................

-.-.do................. ...........

.....do............................

Holland, 1953). 

.....do.... .....................

... ..do.... .....................

 do . ._..

 do... ...... ..............

.....do.... ......... ...... .........

Bakken formation (as used by 

Nordquist, 1953).

.....do..... . .. ....... .

94153 

94154 

94151

94152

97015

97016 

97013

CU14S

94147 

97011

94139 

94140

94141 

94142 

94143 

94144 

94145

94155 

94156 

94157 

94158 

94159 

201460

94176

94764

201457

201458

204065 

204066 

204067 

204068 

204069 

204070

98518 

98519

.002 

.003 

.001

.002

.005

.004 

004

ft(V>

.003 

.002

.004 

.004

.003 

.002 

.003 

.002 

.006

.006 

.007 

.008 

.006 

.004 

004

.004

.004

.003

.004

.003

.006 

.005 

.010 

.007 

.008 

.003

.006 

.004

(n. d

(n. d

(n. d

(n. d

(n. d

(n. d

(n. d

(n. d

(n. d

(n. d

(n. d

(n. 

(n. 

' Not sampled. 
224 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

3

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Chip sample, bed 10^-ft i lenses thinbltaining of Channel middlesample, :shalehaly 11 andblack Channel sample, 2^-ft

shale. brown 

Channel sample, 2-ft bed

shale. 

Chip sample, half upper 

shale. blck 

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roadwater CounSEV4-29-3N-2E, Coun roadwater 

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9 ft
70

73

14-9N-10E.

SW1/4-3-16N-10E.

NEV4-2-16N-10B... ................

6-15N-12E_. __.__. ...............

, NE1/4-11-14N-11E. .................

NW>/4-19-14N-12E _ .__ _

2&-12N-14E.. ....... _______

21-11N-15E. __ . ___________

Wheatland County __________

5-10N-13E. 

7-10N-13E.. ______________

._ do - ____ 

7-13N-18E. 

NWJi-23-13N-17E _ _ .

.....do.. . ... _.._..-

6-12N-20E.. ______________

. _ .do-. __ 

SWM-30-16N-19E.... ________

SWJ£-14-15N-19E. .................

17-14N-2IE ....... ______ .. __

SE&-30-HN-21E.. ... ...........

NE^-8~13N-21E. ........... _......

SW^-17-14N-21E..,_i _______

6WM-16-14N-22E.... __ . ........

.....do.......... ..................

. .do................. ........

..... do...... .... .......... ........

.....do... ..... ..... ....... ....... .

.....do.... ........................

.. do 

.....do.... ............... .........

.....do........... . 

 do . __._

Otter formation __________

.....do.. ____ 

So-called Amsden formation of

local usage.

- _ do. 

do. _ . __ . ,. ...

 ..do... ........ ..

 do .. ... ... 

local usage.

94163

94778

94779

94780

94781

94773

94771

94772 

94766

94765

94783

94785

94784

94177

94173

94174 

94175

94755

94756

94757

94758 

94759 

94760

94761 

94762

94786

94169

94178 

94179

94182 

94183 

94184 

94185

94180

94192

.002

.002

.002

.004

.001

.003

.002

.001 

.001

.003

.001

.002

.003

.002

.003

.004 

.004

.001

.001

.001

.002 

.001 

.003

.003 

.006

.001

.004

.003 

.002

.002 

.002 

.003 

.001

.003

.002

(n. d

(n. d

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(n. d

(n. d

(n. d

(n. d

(n. d

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(n. d

(n. d

(n. d

(n. d

(n. d

(n. d

(n. d

n. d

n. d

n. d

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226 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

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sample, middle of60-ft tnear ninous shale (top of the sequen el bottom sample, IJift ofsar dark-gray ample, ^-ftbed o1 el sample, 1-ft bedlight-yello of ample, bed 4-ft oblack bitumi el sample, b< fttop 3 of25ninous shale te (base of sequel

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74

Judith Basin County _________

1-16N-11E. 

Fergus County.... __________

NW^-20-14N-24E.

.....do...........................

.....do...........................

94777

94776 

94775 

94774 

94189

.005

.002 

.002 

.002 

.002

(n

(n

(n

(n

1 Not sampled.
228 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

The black shale sequence at the base of the Madison limestone was 

sampled at 17 localities in the mountainous parts of southwestern aad 

central Montana and northwestern Utah. Sections at 10 of these 

localities are shown in figure 52. The maximum observed uranium 

content of the sequence is 0.005 percent, in the lower half of a 2K-footthick bed of black shale near Three Forks, Mont. (loc. 43), and 0.005 

percent in the basal part of a 10-foot bed of brownish-black shale 

nearby (loc. 44).

The Bakken formation (as used by Nordquist, 1953) was sampled 

in three wells, two of them in northeastern Montana and the third 

in northwestern North Dakota. Drill cuttings representing 30 feet 

of black shale from one of the wells, Amerada Petroleum Corporation-Harry Bakken well 1, Williams County, N. Dak. (well 15, table 

1), contain 0.005 to 0.007 percent of uranium. A sample of drill core 

from a 10-foot-thick bed of black shale in the C. H. Murphy, Jr., and 

others-East Poplar well 1, Koosevelt County, Mont., sec. 2, T. 28 

N., K. 51 E., contains 0.006 percent of uranium. One of six samples of 

drill core from a 10-foot-thick bed of black shale in the Carter Oil 

Company-S. W. Danielson well 1, Daniels County, Mont., sec. 12, 

T.36N.,K.47E., contains 0.004 percent of uranium. The samples 

from this well are anomalous in that they are decidedly out of balance 

in favor of equivalent uranium, as indicated in the following table:

Descriptions of samples: Carter Oil Company-S. W. Danielson well 1, Daniels

County, Mont.

Sample no.

204065 

204066 

204067 i .- -

204068 

204069 .. -.

204070 

Depth 

(feet)

6964

6966

6968

6970

6971

6974

Description

- do. - - . . -- 

laminae.

eU 

(percent)

0.006

.005

.010

.007

.008

.003

U 

(percent)

n fin?

.002

.003

.004

.004

.002

i J. N. Rosholt, Jr., U. S. Geological Survey Trace Elements Laboratory, investigated the source of the 

high radioactivity in sample 204067, with the following result:

Equivalent uranium (percent)______________________ - ______ -__ - _ 0.010 

Uranium (percent)________________________-_____ ___...____ .003 

ThMss (radio-chemical) (percent). ___ ..._._ .. .- .. ................... .003

Th^o (ionium) (percent equivalent).. .... - ..... ....... .009

Radium (percent equivalent)_ --__ . .... .006

The analysis above indicates that Th230 and radium, both daughter 

products of uranium, are the principal contributors of excess radioactivity. The relatively high concentrations of these elements in 

comparison to uranium suggest that leaching of uranium or addition 

of Th230 and radium has occurred in this deeply buried shale [in 

comparatively recent time.

The thickness and the areal distribution of radioactivity in the 

Bakken formation (as used by Nordquist, 1953) as determined from
______CARBONIFEROUS______________ 

MISSI3SIPPIAN. ~ ' DEVONIAN 

formation VLeatham Jefferson 

toiestone __________Madison 1952_______ Holland, of | formation' 

member shale black Lower 

iTH
230 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

published sample descriptions and gamma-ray logs, are shown in 

plate 15. These maps suggest that black shale in the Bakken formation (as used by Nordquist, 1953) is thickest in the northwestern 

corner of North Dakota and that the formation is most radioactive 

slightly east of this area, near the northeastern corner of Montana. 

It seems evident that radioactivity in the Bakken formation (as 

used by Nordquist, 1953) varies appreciably from place to place with 

a definite pattern. Recognition of the pattern will help in outlining 

areas in which maximum concentrations of uranium in the formation 

may be expected.

BLACK SHALE AT THE BASE OF THE BBAZEB LIMESTONE

In parts of Utah and Idaho the basal part of the Brazer limestone 

of middle and late Mississippian age consists of a black phosphatic 

shale sequence ranging in thickness from a few inches to about 

75 feet. Exposures of this zone were tested at two places in southeastern Idaho (Iocs. 21 and 22), and at one place in northwestern 

Utah (loc. 30). Beds of black shale at the two Idaho localities are 

mostly nonuraniferous, but in Rich County, Utah, a bed of shale 14 

feet thick in the upper part of the sequence contains as much as 

0.006 percent of uranium, and a bed of shale 8 feet thick in the lower 

part contains as much as 0.009 percent of uranium. The measured 

sections and uranium content of the black shale at the three localities 

are shown hi figure 53.

Black shale at the base of the Brazer limestone was examined by 

Duncan (1953) in Ogden Canyon, Weber County, Utah, about 45 

miles southwest of the Rich County locality described above. In 

Ogden Canyon, Duncan reported, beds of phosphatic shale about 

1 foot thick contain as much as 0.005 percent of uranium, 0.18 

percent of vanadium oxide, and 17.3 percent of phosphate.

HEATH SHALE

The Heath shale of late Mississippian age crops out along the margins of the Little Belt and Big Snowy Mountains in central Montana, 

and it has been penetrated in drill holes throughout a large area in 

eastern Montana and western North Dakota. The formation consists mainly of black shale, with subordinate amounts of gray lime* 

stone and fine- to coarse-grained sandstone. It is as much as 650 

feet thick in the subsurface in the northeastern corner of Musselshell County, Mont., and it is as much as 400 feet thick where it is 

exposed on the flanks of the Little Belt and Big Snowy Mountains to 

the west. (See fig. 54.) The Heath is underlain by the Otter forma-
URANIUM IN BLACK SHALE DEPOSITS 231

tion of late Mississippian age, which consists of green and black shale 

and gray limestone; it is overlain by the Amsden formation of local 

usage of late Mississippian and Pennsylvanian age, which consists 

mostly of red shale and sandstone and gray limestone and dolomite.

Sec 32, T. 13 N., R. 6 E., NEJ* sec 23, T. 12 S., R.44 E., SE3* sec 33, T. 7 S., R 40 E 

Rich County, Utah Bear Lake County, Idaho Caribou County, Idaho

A A A A Not sampled

- 10 -

- 20 Feet

FIGUBB 63. Uranium content of black shale at the base of the Brazer limestone, Utah and Idaho.
232 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

11<a 5

C8 _.

a 3 

II
URANIUM IN BLACK SHALE DEPOSITS 233

Outcrops of the Heath shale were examined for radioactivity at 8 

places by W. J. Hail and J. K. Gill in 1951 (in Duncan, 1953), and outcrops of the Heath shale were examined at 24 places by the writer in 

1953. The most highly uraniferous black shale thus far found in the 

formation was discovered by Hail and Gill 3 miles southeast of Forestgrove, Mont., in the NWK sec. 24, T. 14 N., K. 20 E., Fergus County. 

At this locality, the upper 4 feet of a bed of black shale 6 feet thick 

near the top of the formation contains 0.006 percent of uranium. 

Samples of black shale from the Heath shale elsewhere in central 

Montana contain a maximum of 0.003 percent of uranium.

A sample of water from a seep in the upper part of the Heath shale 

on the north flank of the Big Snowy Mountains (loc. 66) contains 7 

parts per billion of uranium.

The Heath shale is characterized locally by large deflections on 

gamma-ray logs of oil and gas wells. A bed 10 feet thick in the Heath 

shale penetrated by the Marigold Oil, Ltd.-Farnham well 1, McCone 

County, Mont, (well 3, table 1), may contain more than 0.01 percent of 

equivalent uranium; and gamma-ray logs show some parts of the 

formation in Musselshell County, Mont., to be almost as radioactive. Not enough information is available so far to attempt to 

analyze the distribution of radioactivity in relation to the variations 

in thickness and lithology of the Heath.

LITERATURE CITED

Anderson, S. B., 1954, Stratigraphic sections of the Mississippian system in North

Dakota: N. Dak. Geol. Surv. Dept. of Inv. no. 16. 

Baillie, A. D., 1953, Devonian system of the Williston Basin area: Manitoba

Dept. Mines and Nat. Res., Mines Br., Pub. 52-55. 

Barnes, T. R., 1952, The Williston Basin a new province for oil exploration:

Billings Geol. Soc. Guidebook, 3d Ann. Field Conf., Williston Basin-Black Hills,

p. 97-117. 

Duncan, D. C., 1953, Reconnaissance investigations for uranium in black shale

deposits of the Western States during 1951 and 1952: U. S. Geol. Survey

TEI-381, U. S. Atomic Energy Comm., Tech. Inf. Service, Oak Ridge, Tenn. 

Gardner, L. S., Hendricks, T. A., Hadley, H. D., and Rogers, C. P., Jr., 1946,

Stratigraphic sections of Upper Paleozoic and Mesozoic rocks in south-central

Montana: Mont. Bur. Mines and Geology Mem. no. 24. 

Gott, G. B., and Hill, J. W., 1953, Radioactivity in some oil fields of southeastern

Kansas: U. S. Geol. Survey Bull. 988-E, p. 69-122. 

Holland, F. D., Jr., 1952, Stratigraphic details of lower Mississippian rocks of

of northwestern Utah and southwestern Montana: Am. Assoc. Petroleum

Geologists Bull., v. 36, no. 9, p. 1697-1735. 

McConnell, R. G., 1887, Report on the geological features of a portion of the

Rocky Mountains, accompanied by a section measured near the 51st parallel:

Geol. and Nat. History Survey of Canada, Ann. Rept. (new ser.) v. 2,

p. 1D-41D.
234 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

Nieschmidt, C. L., 1953, Subsurface stratigraphy of the Heath shale and Amsden 

formation in central Montana: U. S. Geol. Survey Oil and Gas Inv. Chart 

OC50.

Nordquist, J. W., 1953, Mississippian stratigraphy of northern Montana: Billings 

Geol. Soc. Guidebook, 4th Ann. Field Conf., Little Rocky Mts., Mont., 

southwestern Saskatchewan, p. 68-82.

Perry, E. S., 1937, Natural gas in Montana: Mont. Bur. Mines and Geology, 

Mem. no. 3, 96 p.

Sonnenberg, F. P., Rader, M. T., and Clement, J. H., 1952, Electric and lithologic cross-section from Norcanols Ogema [well] to Weller-Bush-Weisman 

[well]: Billings Geol. Soc. Guidebook, 3d Ann. Field Conf., Williston BasinBlack Hills.

Vine, J. D., 1956, Geology of the Stanford-Hobson area, Judith Basin and Fergus 

Counties, Mont.: U. S. Geol. Survey Bull., 1027-J, p. 405-469.

Warren, P. S., 1937, Age of the Exshaw shale in the Canadian Rockies: Am. 

Jour. Sci., 5th ser., v. 33, no. 198, p. 454-457.
INDEX

Bakken formation as used by Nordquist, correlation__ 219 

radioactivity, thickness and areal distribution of. - 228,230 

uranium content in drill cuttings 228 

Banff formation of McConnell, correlation 219 

Big Snowy Mountains..--. __ - 230-233 

Brazer limestone)' black shale at base of, description, radioactivity_ 230

Daniels County, Mont.. . 228

Exshaw shale of Warren, correlation.. .. 219

Forestgrove, Mont.. ... 233

Gamma-ray logs, use in present study. 214 

value of sensitivity scale...._ .. 214 

Geologic formations, stratigraphic relations of,

table... .. __.. _ 212

Heath shate, description, radioactivity._.. 230,233 

Jefferson formation, correlation. .. _ - 219

Page 

Little Belt Mountains. ... 230

McCone County, Mont 233 

Madison limestone and equivalents, black 

shale at base of, description, correlation.. 219 

uranium content observed.. __._ 228 

Musselshell County, Mont. 233

Ogden Canyon, Utah 230

Phosphoria formation, excluded from present

study__ . 213

Koosevelt County, Mont . 228

Sappington sandstone as used by Holland,

correlation_ . __ 219

Three Forks formation, correlation. __ 219 

Three Forks, Mont- 228

Williams County, N. Dak.._________ 228

o

235