Uranium in Sharon Springs 

Member of Pierre Shale 

South Dakota and 

Northeastern Nebraska

GEOLOGICAL -SURVEY BULLETIN 1046-R

This report concerns v: ork done on behalf 

of the U.S. Atomic Energy Commission 

and is published jwitk the permission of 

the Commission

Uranium in Sharon Springs 

Member of Pierre Shale 

South Dakota and 

Northeastern Nebraska

By ROY C. KEPFERLE

CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

GEOLOGICAL SURVEY BULLETIN 1046-R

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 : 1959
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.
CONTENTS

	Page

Abstract___-___-___-_-.--___________-._______________________._-_ 577

Introduction. _-___-_-__--_--_-______-_-___--.__---__-__---_-_---___ 578

Method of investigation_--__-________-___________-_-_---_____-___ 578

Sharon Springs member of the Pierre shale--___-__-------__----_-_-__- 579

Stratigraphic setting-__________________________________________ 579

Lower boundary of the member.____________________________ 580

Upper boundary of the member.. ___________________________ 581

Organic content_____-_-__--_-___-_- ___________________________ 581

Fossils-_ _____-___-_-___-___-_____-_--_-____-__._-_---____--___ 581

Lithology _ ___________.-__________----_-_____-___-_____-_____-___ 584

Radioactivity and uranium content._. ___________________________ 585

Surface information____________ _-_--____________-___-_-___ - 586

Subsurface information._________ ___________________________ 587

Cores--___--___-__----__---_----_---___-___-___---__- 587

Gamma-ray logs___________. ___________________________ 587

Content of other elements--.________.._--_-____-_-___-_--___--_-- 592

Chemical analyses.._-_._-___-- _^__________^______________ 592

Spectrographic analyses.________ ___________________________ 594

Correlation with uranium_____. ____-_____-_-____-_-_---.___ 597

Positive correlation.._____. ___________________________ 599

Negative correlation___________________________________ 599

Reliability of the correlations.__.-__-_____-_______---___ 600

Environment of deposition____________________________________ 600

Origin of uranium.________________________________________________ 602

Conclusions_ _________--_-_____-_____..___--__--_J-_-____-____-___ 602

Selected references.______-_.____---____________-___---_________-___ 603

ILLUSTRATIONS

[Plates in pocket]

PLATE 50. Outcrop map and graphic sections of the Sharon Springs member 

along the Missouri River.

51. Map showing outcrop trace of bentonite zone of the Sharon Springs 

member and sample localities along the Black Hills.

52. Graphic sections showing uranium content of Sharon Springs member 

along the Black Hills.

53. Gamma-ray logs-showing radioactivity of the lower part of the Pierre 

shale and the upper part of the Niobrara formation.

m
IV CONTENTS

Page

FIGURE 85. Stratigraphic sections showing correlation of Sharon Springs

member and associated rocks in South Dakota. _ _ ___ 580

86. Gamma-ray and resistivity logs of Cretaceous rocks in Fred

Chute well 1, Haakon County, S. Dak. ___________ 588

87. Thickness map of the interval between the zone of high radioactivity in the Pierre shale and the top of the Greenhorn 

formation, northern Great Plains.._____________ 590

88. Isoradioactivity map of the Pierre shale, northern Great

Plains _.____________________________ 591

89. Graphic section showing relationship between uranium, selenium and arsenic___._________________________ 592

90. Diagram showing concentration range and mean for 25 elements in the Sharon Springs member ___________________ 593

91. Diagram showing correlation between concentration of uranium and 32 other elements in the Sharon Springs member. 598

92. Histograms showing frequency distribution of elements for

Sharon Springs member.__ ________ ______ 601

TABLES

Page

TABLE 1. Generalized section of Late Cretaceous and younger formations. 582

2. Uranium content of water from the Sharon Springs member 586

3. Minimum concentrations of the elements detectable_______ _ 595

4. Analyses of two samples of coalified wood-____________ __ 595

5. Elements detected by semiquantitative spectrographic analyses

of water residues_________-__-_------------_ - -- - 596

6. Numbers and symbols used in referring to semiquantitative

spectrographic analyses._____ ___________-_-_-_--____-_ 597
CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

URANIUM IN SHARON SPRINGS MEMBER OF PIERRE 

SHALE, SOUTH DAKOTA AND NORTHEASTERN NEBRASKA

By EOT C. KEPFERLE

ABSTRACT

A study of the uranium content of the Sharon Springs member of the Pierre 

shale in South Dakota and northeastern Nebraska was made in 1954. More 

than 300 samples of this black organic marine shale of Late Cretaceous age 

from 30 exposures and 2 core holes show that the uranium content averages 

about 0.0015 percent throughout the region studied. The most uraniferous 

parts are about 3 inches thick and contain as much as 0.025 percent uranium. 

The richest sample comes from an exposure along the Missouri River in Nebraska and is thought to be secondarily enriched by weathering. Water from 

the Sharon Springs member generally has a pH of less than 4, and 7 samples 

from seeps and springs contained from 7 to 780 parts uranium per billion.

The thickness of the Sharon Springs member ranges from 1 to 42 feet in 

exposures along the Missouri River and is as much as 106 feet on the eastern 

flank of the Black Hills. Gamma-ray logs and published lithologic logs from 

holes drilled for oil and gas indicate that rocks equivalent to the member extend 

northward from central South Dakota into North Dakota and that the radioactivity decreases northward.

Along the Missouri River in eastern South Dakota, the noncalcareous Sharon 

Springs member lies on the calcareous Niobrara formation. At some places 

the two units appear conformable; at others a disconformity separates them. 

Along the southeast flank of the Black Hills and northward to North Dakota, 

the Sharon Springs rests conformably on rocks equivalent to the Gammon member 

of the Pierre shale.

The upper boundary of the Sharon Springs member is poorly defined except 

at a few exposures along the Missouri River where a marly zone marks the 

base of the overlying Gregory member of the Pierre. Elsewhere, the upper 

boundary is placed at the change from the darker color and steeper slopes of 

the Sharon Springs member to the lighter color and gentler slopes of the overlying Gregory member.

Semiquantitative spectrographic analyses of 82 samples of black shale from 

the Sharon Springs member indicate that the molybdenum, iron, and phosphate 

contents tend to vary directly with the uranium content, whereas the aluminum, 

gallium, boron, titanium, magnesium, and sodium contents vary inversely with 

the uranium content.

The uranium in the Sharon Springs member is thought to have been emplaced during or shortly after the deposition of the shale.

577
578 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

INTRODUCTION

A reconnaissance search for uranium in the Sharon Springs member 

of the Pierre shale was made by the author during the summer of 

1954 in southern South Dakota and northeastern Nebraska in continuation of the investigation begun in 1953 by H. A. Tourtelot (1956). 

The main objective of the search was to determine the areal and 

stratigraphic distribution of uranium in the black shale of the member 

as a means of evaluating it as a source of uranium. Secondary objectives were to determine controls that influenced the occurrence of 

uranium in the shale that could be used as a guide in future prospecting 

and to examine the overlying and underlying rocks for uranium.

The investigation by Tourtelot (1956), using surface exposures and 

gamma-ray logs of holes drilled for oil, showed that the Sharon 

Springs member is radioactive in the subsurface over an area extending 

through western Kansas and Nebraska, northeastern Colorado, and 

southern South Dakota. Gamma-ray logs examined during the present study show that the radioactive shale extends through most of 

South Dakota into northeastern Nebraska and most of North Dakota, 

as well.

Simultaneously with the present study, other investigations of the 

Sharon Springs member were made in the Chadron area of Nebraska 

and South Dakota by E. J. Dunham (1955, p. 164) and in eastern 

Colorado and western Kansas by E. E. Landis (1959). The search 

was made by the U. S. Geological Survey on behalf of the Division of 

Eaw Materials of the U. S. Atomic Energy Commission.

The cooperation of Dr. E. P. Eothrock, State geologist of South 

Dakota at the time this investigation was made, and L. B. Underwood 

and E. E. Fisher of the U. S. Corps of Engineers, as well as the many 

farmers and ranchers of the area, is greatly appreciated. The writer 

also wishes to thank L. B. Eiley and J. D. Vine of the Geological 

Survey for their assistance in interpreting the spectrographic data. 

Geological Survey analysts, who made chemical and spectrographic 

analyses and to whom the writer is grateful, include W. Tucker, J. 

Budinsky, A. Sweeney, S. Furman, E. Cox, J. Schuch, M. Finch, H. 

Lipp, Mona Frank, Eoosevelt Moore, G. Burrow, N. M. Conklin, E. 

Duf our, and T. Miller.

METHOD OF INVESTIGATION

In order to determine the areal and stratigraphic distribution of 

uranium within the Sharon Springs member of the Pierre shale, 

stratigraphic sections were measured in detail at 15 localities along the 

Missouri Eiver valley in South Dakota and Nebraska and at 15 

localities along the eastern and southern flanks of the Black Hills in
URANIUM, SHARON SPRINGS MEMBER, PIERRE SHALE 579

South Dakota. The surface was scanned with a scintillation counter, 

and anomalously radioactive zones were sampled. Most of the route 

traveled between outcrops was scanned with a jeep-mounted scintillation counter. At a few localities channel samples were taken throughout the complete thickness of the Sharon Springs member; at other 

localities, complete channel samples were taken only through the most 

radioactive zones. A few grab samples of concretions, wood fragments, and other material anomalous to the general lithologic character 

of the member were taken from the overlying and underlying rocks. 

In all, more than 300 samples were collected. Most of the samples 

showing radioactivity of 0.003 percent or less equivalent uranium 

(eU) 1 were not analyzed chemically for uranium content. Many of 

the samples were analyzed semiquantitatively by spectrographic methods in the laboratories of the U. S. Geological Survey. A statistical 

study of the analyses of 82 samples of shale was made to determine 

factors which may affect the distribution and concentration of the 

uranium.

SHARON SPRINGS MEMBER OF THE PIERRE SHALE

STBATIGBAPHIC SETTING

The Sharon Springs member was first described by Elias (1931) as 

the basal member of the Pierre shale in western Kansas. Searight 

(1938) applied the name to the black organic shale at the base of the 

Pierre shale of South Dakota but included overlying gray shales since 

named the Gregory member by Gries and Kothrock (1941), who 

restricted the Sharon Springs member to the fossil fish bearing shale 

that overlies the Niobrara formation and underlies the Gregory member in central South Dakota. The better exposures along the Missouri Kiver are referred to by Searight (1937), Gries and Eothrock 

(1941), Gries (1942), Petsch (1946), and Simpson (1955). Many of 

the exposures have since been inundated behind Fort Eandall Dam. 

On the southeastern flank of the Black Hills the Sharon Springs 

member does not lie on the Niobrara formation but apparently on a 

wedge edge of rocks lithologically similar to the Gammon ferruginous 

member of the Pierre shale described by Rubey (1930) in northeastern 

Wyoming. On the northeastern flank of the Black Hills the Sharon 

Springs member cannot be distinguished from the Gammon ferruginous member.

In the present report the Gammon ferruginous member is referred 

to as the Gammon member, inasmuch as equivalent rocks on the eastern and southern flanks of the Black Hills lack the abundant ferrugil Percent equivalent uranium is an expression of the radioactivity in terms of the amount 

of uranium -which, in equilibrium -with its daughter products, -would produce that amount 

of radioactivity.
580 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

nous concretions found in the type area described by Rubey. Spivey 

(1940) and Gries (1942) discuss many of the better exposures along 

the southeastern flank of the Black Hills. The generalized stratigraphic relationships of the Sharon Springs member to other rocks 

in the region are shown in table 1; the detailed relationships to overlying and underlying rocks are shown by four measured sections 

(fig. 85).

23 <

Bijou Hills. Missouri River 

SWI/4sec.l3, T.IOON..R. 72 W. 

Gregory Coun ( y

Northeoat Bloc* Hills 

SI/2sec.8,T.4N,R.BE, 

Meode County

* Zone of highest uroniumxcontent in section

Number obove section refers ts locolity number on index mops, plates 50 ond 51. 

Correction linedoshed where inferred.

FIGURE 85. Stratigraphic sections showing correlation of Sharon Springs member of the 

Plerre shale and associated rocks in South Dakota.

LOWER. BOUNDARY OF THE MEMBER

At most places along the Missouri River the noncalcareous Sharon 

Springs member appears to lie conformably on the calcareous Niobrara 

formation. The two can be readily differentiated by their calcium 

carbonate content. Test holes at the Oahe Dam site near Pierre show 

an interfingering of the calcareous and noncalcareous lithologies. At 

other exposures along the Missouri River, however, a disconformity 

between the two is indicated by a "trashy" zone consisting of a lag 

concentrate of fish bones, scales and scutes, plant debris, and some silt.
URANIUM, SHARON SPRINGS MEMBER, PIERRE SHALE 581

The Gammon member of the Pierre shale, which lies beneath the 

basal Sharon Springs member in southwestern South Dakota, pinches 

out between the Black Hills and the Missouri River. At Ardmore 

(loc. 12, fig. 85 and pis. 51 and 52) 15 feet of shale and bentonite, 

thought to be equivalent to the Gammon member, lie conformably between the Sharon Springs member above and the Niobrara formation 

below. Southeast of Hot Springs at the Cheyenne River (loc. 8, fig. 

85 and pis. 51 and 52) this shale is 67 feet thick. The Gammon member is 800 feet thick at the north end of the Black Hills (Cobban, 1952).

UPPER BOUNDARY OF THE MEMBER

The upper boundary of the Sharon Springs member is locally clearly 

defined by the basal marly zone of the overlying Gregory member of 

the Pierre shale. However, where the marly zone is absent, the two 

members can be differentiated by the change from the darker color and 

steeper slopes of the Sharon Springs to the lighter color and gentler 

slopes of the overlying Gregory member. The upper contact of the 

Sharon Springs is marked at some places by a thin bentonite bed or 

a layer of concretions, most of which are gypsiferous claystone. A 

fairly continuous 3-inch bed of ankerite, goethite, and limonite, containing more than 10 percent manganese, occurs at the upper contact 

at locality 2 (fig. 85 and pis. 51 and 52).

OBGANIC CONTENT

An analysis made by W. Tucker, J. Budinsky, and A. Sweeney of a 

sample of the shale near the Fort Randall Dam (loc. 25, pi. 50) shows 

10.3 percent organic matter, from which about 4 gallons of oil per ton 

of shale may be distilled. A sample from locality 21 (pi. 50) yields 

8 gallons of oil per ton. The organic matter and sulfur in the shale 

are sufficient locally to ignite spontaneously, baking the shale to a 

brick-red clinker (loc. 9, pi. 51, and Iocs. 20 and 23, pi. 50). Much of 

the organic matter is macerated plant material, although two large 

coalified wood fragments were found (loc. 14, pis. 51 and 52, and loc, 

25, pi. 50).

FOSSILS

Scales belonging to a chirocentrid fish, Portheus or Icthyodectes, and 

teeth and scales of the teleost fish, Enchodus, from locality 23 (pi. 50) 

were identified by D. H. Dunkle of the U.S. National Museum. Mr. 

Dunkle also referred parts of a lower left jaw from locality 14 (pi. 51) 

to the mosasaur genus Clidastes, because of their similarity to specimens of Clidastes westii described from the Sharon Springs member 

of the Pierre shale in western Kansas.

Marine mollusks from the limestone concretions directly below the 

Ardmore bentonite zone of Spivey (1940) at locality 9 (pis. 51 and 52)

491603 59 2
582 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

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J9AJH 9«qAl
Lower 

Cretaceous

Niobrara formation 1

Smoky Hill marl member

Ft. Hays 

limestone member

Carlile shale

Greenhorn formation

Belle Fourche shale

Mowry shale

Newcastle sandstone

Skull Creek shale

= 60-120

& 40-100

270-800

25-800

500-850

150-250

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Shale, so

sandst

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ridge f

Shale, so

Shale, si

Sandston

coal be

Shale, da

i Members not clearly separable around Black Hills.
584 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

have been identified by W. A. Cobban of the U.S. Geological Survey 

(written communication, 1954) as Bacuities aquilaensis Reeside and 

Baculites aquilaensis var. separatus Reeside. Similar fossils were 

found at the same horizon at localities 8 and 10 (pi. 51).

LITHOLOGY

The areas where the Sharon Springs member crops out along the 

Missouri River in South Dakota and Nebraska and along the southern 

and eastern flanks of the Black Hills are shown in plates 50 and 51. 

Graphic sections of the shale in these two general areas are shown 

in plates 50 and 52. The member ranges from 96 to 106 feet in thickness along the eastern and southern flanks of the Black Hills (fig. 85), 

where it is characterized by three distinct units: a lower shale unit, 

a bentonitic unit, and an upper shale unit. The upper and lower 

shale units are characterized by tough, dark-gray to black shale containing numerous scales, spines, and bone fragments of fish. On the 

outcrop the shale weathers to silver-gray flakes, and the more resistant 

parts form rounded buttresses surrounded by subdued topography. 

The bentonitic unit includes as many as 20 bentonite beds, ranging 

from an inch to slightly more than 2 feet in thickness, distributed 

through an interval of about 30 feet. This unit generally has a thick 

bentonite bed near its base that may range from 2% to 3% feet in 

thickness. This bentonite zone was named the Ardmore bentonite 

bed from outcrops near Ardmore, S. Dak. (Spivey, 1940; Cobban and 

Reeside, 1952). Some of the beds within this bentonite zone can be 

traced with fair certainty from Rapid City southward to Ardmore, and 

thence northwestward to the South Dakota-Wyoming line.

Along the Missouri River, the thickness of the Sharon Springs 

member ranges erratically from 7 to 42 feet. Simpson (1955) reports 

that the Sharon Springs is only 1 foot thick in sec. 23, T. 33 N., R. 4 W., 

Knox 'County, Nebr. Similarly, 16 bentonite beds may be present at 

one outcrop, and only 2 may appear at another. The variation in 

thickness and number of beds suggests local interruptions in the deposition of the member caused by periods of local erosion. The bentonite beds along the Missouri River are much thinner and less persistent than those in the western part of South Dakota; the thickest 

bentonite is about 4 feet thick along the Black Hills and is slightly less 

than 2 feet thick along the Missouri River. Slumping of overlying 

rocks partially obscures the Sharon Springs at several localities.

Ellipsoidal concretions of limestone ranging from a few inches to 

3 feet in thickness and from 6 inches to 6 feet in diameter occur at as 

many as 15 horizons along the eastern flank of the Black Hills. Some 

contain calcite and barite as septarian vein fillings. Along the Mis-
URANIUM, SHARON SPRINGS MEMBER, PIERRE SHALE 585

souri River, limestone concretions, where present, occur at only 1 

or 2 horizons. A few ferruginous concretions generally are present 

near the top of the member.

Fresh samples of the shale of the Sharon Springs member contain 

shotlike accretions of pyrite which range from a fraction of a millimeter to 3 millimeters in diameter. The decomposition of this pyrite 

probably forms much of the iron oxides and sulf ates which stain outcrops a light yellow.

Selenite commonly occurs as fracture coatings, isolated crystals ranging from less than 1 millimeter to about an inch in length, or cone-incone concretions as much as iy2 feet in diameter. The cone-in-cone 

concretions, as well as crystals up to 5 inches in length showing multiple 

twinning, are common in the thicker bentonite beds.

A standard rock analysis of a sample from the Sharon Springs 

member of the Pierre shale is reported by Simpson (1955) from the 

sec. 17, T. 93 N., R. 56 W., near locality 28, plate 50 :

Percent

SiOa ______________________ ._ _____________ 60.98 

FeaO3 _____________________ .. _____________ 3.20 

Al*Oa _____________________ .. _____________ 16. 84 

CaO ____________________ .. ____________ 1. 84 

MgO ______________________ .. _____________ 1. 69 

SO2 ____________________________________ None 

Volatiles __________________ .. ____________ 7. 53 

Moisture ___________________ .. _____________ 5. 14

This analysis, compared with the average analysis for shales in general (Pettijohn, 1949, p. 82) indicates that the Sharon Springs contains 

somewhat more silica, alumina, and moisture, and somewhat less iron, 

lime, and magnesium. The volatiles include carbonaceous matter and 

probably the sulfur from iron sulfide.

EADIOACTIVITY AND TJBANITJM CONTENT

The maximum uranium content of samples of the Sharon Springs 

member in the report area is 0.025 percent, and the average uranium 

content for the entire member is about 0.0015 percent. This average is 

about 12 times higher than that given for sedimentary rocks in general 

(Evans and Goodman, 1941) and is on the order of the average 

uranium content reported by Breger (1955) for the Antrim shale of 

Late Devonian age in Michigan and a nodular shale of Miocene age 

from California. At three localities, zones having a uranium content 

of at least 0.005 percent aggregate more than 1.5 feet in thickness (Iocs. 

7, 10, and 22, pis. 50 and 52) .

Disequilibrium between uranium content and radioactivity expressed in percent generally favors radioactivity by about 0.002 ; for
586 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

example, samples showing radioactivity of 0.004 percent equivalent 

uranium generally have a uranium content of 0.002 percent. The shale 

is consistently out of balance, as indicated by analyses of core samples 

from the Oahe Dam site and from an oil test well drilled in the SE^ 

sec. 17, T. 15 N., E. 20 E., Ziebach County, S. Dak. Water from seeps 

in the Sharon Springs member contains 7 to 780 parts per billion 

uranium (table 2), thus indicating that some of the disequilibrium 

may be caused by leaching.

TABLE 2. Uranium content of water in seeps issuing from the Sharon Springs 

member of the Pierre shale along the eastern and southern flanks of the Black Hills, 

iSouth Dakota

[Analysts: J. Schuch, G. Burrow, and N. M. Conklin]

Laboratory No

220340

231104

223376

219172

219174

231105

231106

Location (pi. 51)

SEK sec. 8, T. 4 N., R. 8 E.,

Meade County.

SEH sec. 8, T. 7 S., R. 7 E.,

Fall River County.

NW# sec. 33, T. 9 S., R. 5 E.,

Fall River County.

NWH sec. 30, T. 10 S., R. 5

E., Fall River County.

NW& sec. 28, T. 11 S., R. 1

E., Fall River County.

NW# sec. 8, T. 12 S., R. 4 E.,

Fall River County.

SWM sec. 16, T. 35 N., R. 47

W., Shannon County.

Uranium 

content 

(PPb)

25

215

20

7

57

300

780

pH

7.8

3.0

2.6

7.9

3.5

2.9

2.6

Remarks

Water is from base of

member.

Water is from shale

below Ardmore

bentonite.

Water is from shale

between bentonite

beds above Ardmore

bentonite.

Water is frojn shale

above bentonite beds.

Water is from shale

between bentonite

beds above Ardmore

bentonite.

Do.

Water is from shale

above bentonite beds.

Marl of the overlying Gregory member of the Pierre contains less 

than 0.001 percent uranium, but gamma-ray logs (fig. 86 and pi. 53) 

indicate that the underlying Niobrara formation is more uraniferous. 

It contains as much as 0.004 percent uranium directly beneath the 

Sharon Springs member at locality 19 (pi. 50). Analyses of 8 samples of water from the Niobrara formation show a uranium content 

ranging from 2 to 90 parts per billion and averaging about 35 parts 

per billion. Part of this uranium could have been derived from the 

overlying Sharon Springs.

SURFACE INFORMATION

The vertical distribution pattern of uranium and radioactivity 

within the measured outcrops of the Sharon Springs member is shown 

by graphic sections (pis. 50 and 52). In sections along the eastern 

and southern flanks of the Black Hills, uranium generally occurs
URANIUM, SHARON SPRINGS MEMBER, PIERRE SHALE 587

within 10 feet above the bentonite zone (the Ardmore bentonite of 

Spivey, 1940). The upper limit of this zone is marked by a bentonite bed about 1 foot thick. Exceptions to this pattern are found at 

two places: first, at locality 2 (pi. 52) where the most radioactive 

portion of the shale is a bed less than 4 inches thick just above the base 

of the member, and second, at locality 4 (pi. 52) where the most radioactive and stratigraphically highest shale sampled is at least 25 

feet above the bentonite zone.

The measured sections along the Missouri Eiver appear to be enriched in uranium along the same general pattern as in the Black 

Hills. Where numerous bentonite beds make up the basal part of the 

member, the zone richest in uranium lies just above the uppermost 

thick bentonite bed in the group. Where the bentonite beds are less 

than 0.2 foot thick or are absent, the enriched zone lies at the base of 

the member, just above the Niobrara formation. The sections at localities 16 and 17 (pi. 50) are partial sections, being incompletely 

measured. The upper part of the Sharon Springs member contains 

higher than average amounts of uranium at localities 23, 25, and 26 

(pi. 50). This increase in uranium content appears to be associated 

with an increase in fish remains and plant debris in a "trashy" zone.

Bentonite beds sampled at localities 19 and 21 (pi. 50) contain 0.0007 

and 0.007 percent uranium, respectively. An analysis by S. Furman, 

E. Cox, and J. Schuch of fish scales, bones, and spines, shows a uranium 

content of 0.094 percent and a P2O5 content of 21.6 percent. A 3-inch 

zone directly overlying the Niobrara formation at locality 29 (pi. 51) 

contains 0.025 percent uranium. The sample is thought to be secondarily enriched, for it shows radioactivity of only 0.017 percent equivalent uranium, and a fresh sample from the same horizon contains only 

0.004 percent uranium.

SUB SURFACE INFORMATION

CORES

Eighteen selected core samples of the Sharon Springs member from 

the Irish Creek well in the SEi/4 sec. 17, T. 15 N., E. 20 E., Ziebach 

County, S. Dak., and 10 core samples from a test hole at the Oahe 

Dam site in sec. 1, T. Ill N., E. 80 W., Hughes County, S. Dak., contain 0.002 percent or less uranium. These selected samples are representative of the lithology of 140 feet and 98.4 feet of core, respectively 

(Eussell, 1925; L. B. Underwood and E. E. Fisher, written communication, 1954).

GAMMA-HAY LOGS

The pattern of distribution of radioactivity in rocks of central 

South Dakota (fig. 86) indicates that the highest radioactivity is in
588 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

Kerr-McGee Oil Industries,Inc.

Fred Chute No. I

Sec. 33, T. 3 N., R. 19 E., (location 20, plate 53) 

Hoakon County, S. Dak.

SOUTH DAKOTA 

"^Fred Chute No. I

INDEX MAP

1 Formation tops taken from 

electric-log and published 

strotigraphic information

' Gamma-ray log has been 

computed from a 6-inch 

to a 10-inch Lane Wells 

sensitivity index

FIGUBH 86. Gamma-ray and resistivity logs of rocks of Cretaceous age in Fred Chute 

well 1, Haakon County, S. Dak.

the Sharon Springs member of the Pierre shale. The 35 gamma-ray 

logs examined from holes drilled for oil and gas in this and adjacent 

regions indicate that this high radioactivity may be correlated from 

well to well and that the Sharon Springs extends from northern 

Nebraska northward through North and South Dakota into southern
URANIUM, SHARON SPRINGS MEMBER, PIERRE SHALE 589

Canada and westward into eastern Wyoming and northeastern Montana. Twenty gamma-ray logs reproduced at a 10-inch sensitivity 

index with the top of the Greenhorn formation as datum are shown 

in plate 53. The rocks between the radioactive zone of the Pierre shale 

and the top of the Greenhorn formation (table 1 and fig. 86) thicken 

westward in North and South Dakota (fig. 87 and pi. 53). Although 

some thickening takes place in each rock unit (Reeside, 1944), much 

of the thickening takes place in the Gammon member of the Pierre 

shale.

A study of the gamma-ray logs indicates that the radioactivity of 

the Sharon Springs ranges from 0.002 to 0.010 percent equivalent 

uranium. These determinations were based on the premise that, at a 

10-inch sensitivity index, a 1-inch deflection is caused by 0.0007 

percent equivalent uranium (Gott and Hill, 1953).

A check was made during the present study to determine whether 

Gott and Hill's calibration factor is applicable to black shales. Chemical analyses 2 for uranium were made of 23 samples of core representing 

black shale, limy shale, and dolomite of Paleozoic age from the Carter, 

Sinclair, and Socony-Vacuum Companies' Lockwood well 1 in sec. 

5, T. 147 N., R. 93 W., Dunn County, N. Dak. In comparing the 

gamma-ray log of this interval with the equivalent uranium content 

of the samples collected, the radioactivity of the samples could be 

predicted to within 0.001 percent equivalent uranium by using the 

calibration factor of Gott and Hill (1953).

Gott and Hill (1953, p. 70-71) pointed out, however, that there are 

many complicating factors that might cause erroneous interpretation 

of gamma-ray logs. The more important of these factors are the thickness versus the grade of the bed, the fluid content of the well, the shielding effect of casing, differences in individual instruments, and the rate 

of movement of the gamma-ray detector. Of the parts of the logs 

shown in figure 86 and plate 53, none of the intervals shown were cased 

at the time of logging and the rate of movement of the detector in 

most of the holes was about 35 feet per second. Even though the 

other factors cannot be critically evaluated, it is assumed their effect 

does not differ greatly from well to well.

Because of the demonstrated accuracy of predictions using the Gott 

and Hill calibration factors, the data gleaned from the study of 

gamma-ray logs of wells drilled for oil and gas in North Dakota, 

South Dakota, and Montana showing radioactivity of the Sharon 

Springs member are presented as a fairly reliable guide to the radioactivity of the member. The highest radioactivity shown by each well

3 Analysts: S. Furman, M. Finch, and H. Lipp. 

491603 59 3
590 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

« E 

f £

* e

If

o .

O O o

§ g p

= §

 - o

1

8-

S E

OJ

I

« p

£ O
X -q ' A r - - ^ S

r\N^ i \i 3 ^ \ \ \

^ ^'^ \\ \ \ \ ^x, \ ^- \

^ \ 1 \ N \

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ix . / x" / j 

x v. I f . s-' \ 

^^ _--^ / / / NORTH DAKOTA v

[ \ i ' / \

j ' j I* / _ S MONTANA! -y^-^-^. L \ \- 1 -- -- ~~ j 

| / X^>\\ J-> I 1 ' 

! / //^^xV5 / ^ 

,~^ / / / \ -°° 1 ' | 

f/VXi/ / / \ / / SOUTH DAKOTA 

" ^//7^k / ' \ * * / / 

WYOMING/K^A/ ^\ \ / '

ty^//fy//\ 1 \ Vpd /

K///\/j/(/'//\ I \ ^

\f//^/y////\ \ \ /

\///j(////\ \ ^~^ * no9 ^J^ y^l

\^/\////A\ ' » s777y~>~^ YS

\IV/////I \ <=Q C//^//ffi7?//A 

/ \§(//y/] \ ^\. ^^^^/^/'////^ 

I f^^ ^V^ ^%,0f^^^ 

I S § °4 ~~~ ^- 009 \ NEBRASKA^^^^

1 r L °&o \ v>>^

III * * * ^ -= 00.T-X \ Y///A

FIGUEB 88. Isoradioactivity map of the Pierre shal
592 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

was plotted on a map and lines were drawn through points of equal 

radioactivity intensity. This map (fig. 88) indicates that the radioactivity is highest in south-central South Dakota and decreases westward and northwestward in western South Dakota and North Dakota 

to the extent that the Sharon Springs could not be identified with certainty in eastern Montana and Wyoming. This decrease in radioactivity probably reflects a decreasing amount of organic matter for 

a given volume of shale, a factor that may be explained in part by the 

increasing nearness to the source of the sediments, which may have 

been chiefly in the west throughout most of Late Cretaceous time. It 

is interesting to note that the direction of increasing radioactivity 

coincides roughly with the eastward thinning of the interval between 

the Sharon Springs member and the Greenhorn formation even though 

the thinning is mainly due to the wedging out of the Gammon member.

CONTENT OF OTHER ELEMENTS 

CHEMICAL ANALYSES

Eighteen channel samples (loc. 19, pi. 50) were analyzed for arsenic 

and selenium. These analyses show a parallel relationship between 

the uranium content of the shale and the contents of arsenic and 

selenium (fig. 89). This relationship appears to be due to the reducing

FIGURE 89. Graphic section showing relationship between uranium, selenium, and 

arsenic in channel samples of the Sharon Springs member, Lyman County, S. Dak.

environment under which arsenic, selenium, and uranium are deposited (Rankama and Sahama, 1950, p. 742, 749; and Davidson 

and Ponsford, 1954). Phosphatic fish remains are also known to concentrate arsenic as well as uranium (Goldschmidt and Peters, 1934).
.oooi -poo; .ooo« .001 OO2 -OO4 .OOe .01 .02 XJ4 .06 OS 

X 

G )

 XYb | 

 *-) J 

" < c

_

Co

O

"L^..

Y

Cr

-*-

Mo| |

,:-

u

 1 

Ni

 I- © 

Zr 

-t 

C

s

e

i __ .

Mn

--

«-x 

nt:

Bo

-* 1-

(

V

 1 

,x

__ -

0

FIGURE 90. Diagram showing concentration range and mean for 25 ele

member of the. Pierre Shale, South Dakota 
594 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM 

SPECTHOGRAPHIC ANALYSES

More than 300 samples of the Sharon Springs member and associated 

rocks were analyzed by the semiquantitative spectrographic method 

to determine the content of trace elements and their relationship to 

uranium in the black shale of the Sharon Springs. In this semiquantitative spectrographic method, standard plates for each element are 

prepared from artificially prepared standard samples. These samples 

contain amounts of each element that divide each decimal order of 

magnitude into three equal intervals or groups on a logarithmic scale. 

(See table 6.) The interval between 1 and 10, for example, is divided 

into 1-2, 2-5, and 5-10 percent, when rounded off to one significant 

figure. The spectrogram of the sample is visually compared with that 

of the standard plates and the values for individual elements are 

reported within the appropriate group. Comparisons of this type of 

semiquantitative results with those obtained by quantitative methods, 

either chemical or spectrographic, show that the assigned group includes the quantitative value at least 60 percent of the time (A. T. 

Myers, oral communication, 1958).

Trace amounts of 25 elements were detected in nearly all the samples. 

These elements, except silicon and with the addition of chemically 

determined uranium, are listed in figure 90. Those elements which 

occur in amounts greater than uranium, in order of their apparent 

abundance, are silicon, aluminum, iron, potassium, titanium, magnesium, calcium, sodium, barium, vanadium, boron, zinc, manganese, 

copper, strontium, zirconium, nickel, chromium, and molybdenum. 

Those elements which occur in concentration less than uranium, in 

order of decreasing abundance, are yttrium, lead, cobalt, scandium, 

gallium, and ytterbium. The mean concentration of copper and 

vanadium in the Sharon Springs is notably higher than in other 

shales (pelitic rocks) (Shaw, 1954). Those extremely rare elements 

which are found in a few of the samples are beryllium, niobium, and 

silver. Elements which may be present in amounts greater than 

uranium but which are rarely detected are arsenic, phosphorus, cerium, 

dysprosium, lithium, neodymium, samarium, lanthanum, and cadmium. (See table 3.)

The germanium content of two samples of coalified wood is particularly noteworthy. Partial analyses of these two samples are given 

in table 4. A similar association of uranium and germanium in coalified wood from black shale of Upper Devonian age has been reported 

by Breger and Schopf (1955).

Five-gallon samples of water were collected from the Sharon 

Springs member at two of the localities listed on table 2 and from an 

additional locality on the Chadron arch in Shannon County, S. Dak.,
URANIUM, SHARON SPRINGS MEMBER, PIERRE SHALE 595

TABLE 3. Minimum concentrations of the elements generally detectable by the 

semiquantitative spectrographic method

[August 10,1954]

Element

Ag__. __________________

AL _ _____-__-_-___---_

As.___ ____ _______ ___

Au_._ _ _-_.___-___ _ _

B

Ba___ ___ ____ _ ___

Be__-_--_____-_-___--_-

Bi___. _._______.-__----_

Ca___________-_-__---__

Cd-_._. _ 

Ce__ ---_----_------_

Co... __________________

Cr-___-___-__ _______

Cu-______-________-_-__

Dy__________________-_

Er_________-_______--__

Fe------_ _ 

Ga_______-________.____

Gd _- _ _._

Ge

Hf_____________________

Hg 

In __ _____ _ __ ___ __

Ir _ _ ___ _-_-. ___ _

K _ __ _ _ ...

La_. ___________________

Li__ _ ___________ ____

Me

Mo___ ___ __._.___. _ _ Mn_, ___________________

Percent i

0. 00005

.001

.05

.003

.005

.0001

.0001

.001

.001

.005

.05

.0005

.0001

. 00005

.05

.005

.001

.001

.005

.0005

.05

1. 0-0. 1

.001

.005

.5

.005

.01

.001

.001

.0005

Element

Na

Nb_____________________

Nd .___.- 

Ni.--_._ _ _-

Os___ _ ______ _ ______

P

Pb_________________.___

Pd_. ._.__. _...._.__.._.

Pt___-_-__-----_- ____

Re__ __ _ __ _ -___

Rh _ ________ ____ ___

Ru_--____..-__ _ _______

Sb__... ________________

Sc

Si.. ___ _ __

Sm_-_______--___-_--___

Sn-_--_____-____---___-

Sr_-__-___---_-_---____-

Ta._ _ _ ________

Te_._. _________________

Th-____-____-_-_-______

Ti _ __ _ _ _ __ ___

U_

V

W-___.__ _ _-__.._

Y _ ______ __

Yb_____________________

Zn--_-______________-__

Zr _ _ _ __

Percent 1

0.05

.001

.01

.0005

.005

. 1

.001

.0005

.003

.005

.005

.005

.01

.001

.001

.01

.001

.0001

.05

.08

.05

.0005

.05

.001

.01

.001

.0001

.02

.001

1 The limits of detection given are based on the semiquantitative method used in the analytical laboratory 

at the time of analysis.

TABLE 4. Analyses of two samples of coalified wood from Sharon Springs member 

of the Pierre shale, South Dakota

[Analysts: Mona Frank, Roosevelt Moore, and Carmen Johnson]

Percent by weight

Item

Uranium __ ___ _ ____ ____________ __ _

Ash__ _________ _ __ _ __ _ _ -___-_-__._ _

Uranium in ash_ _ _ _________ _ _ _____ _ ___

NWJ4 sec. 28, 

T. 11 S., R. 1 

E., Fall River 

County (loc. 

14, pi. 51)

0.003

.002

19.3

.014

.5 -1

1. 0 -2

.2 -0.5

. 05 -0. 1

NEK sec. 8, T. 

95 N., R. 65 

W., Charles 

Mix County 

(loc. 25, pi. 50)

0.006

.009

58.9

.010

. 05 -0. 1

.5 -1

.1 -0. 2

.1 -0. 2

1 Semiquantitative spectrographic determinations. (See table 3.)
596 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

to the southeast. An aliquot from each sample was analyzed for 

uranium and the remainder was evaporated to dryness. The weight 

of the residues ranged from 125 grams in the least uraniferous to 232 

grams in the most uraniferous. These residues were analyzed spectrographically and the results are presented in table 5.

TABLE 5. Elements detected by semiquantitative spectrographic analyses of water 

residues from the Sharon Springs member of the Pierre shale, South Dakota

[Analyst: N. M. Conklln]

Element

Na 

Me

Ca ___ 

Al. ...-_----

Fe

Mn___- 

Zu 3 ___ - __ -

Li ------

Si. - 

Ni. ---------

Sr ------

Cu - ,--

Co 

Y 

V- - 

P» ______ -. ___ _

B __ __

Cd _ .

Cr-_ 

Yb ___---_-

Sc... ...... 

BeBa

U (ppm) « ....

Laboratory No. 231104

Sec. 8, T. 7 S., R. 7 E., 

Fall River County

Percent In 

residue 1

3.2 

3.2 

3.2 

1.5 

.15

. 15 

.19 

.15 

.068 

.015

.015 

.0068 

. 0068 

.0068 

(«)

.0019 

Trace 

Trace 

. 00068 

. 00068

(4) 

. 00015 

. 00015

Parts per 

million In 

water J

200 

200 

200 

100 

10

10 

12 

10 

4.5 

1

1 

.45 

.45 

.45

. 12 

<. 28 

<. 28 

.045 

.045

.01 

.01

0. 215 (pH 3.0)

Laboratory No. 231105

Sec. 8, T. 12 8.. R. 4 E., 

Fall River County

Percent In 

residue '

6.8 

3.2 

1.5 

1.5 

. 15

.32 

.22 

.068 

.068 

.032

.015 

.0068 

.0068 

.0068 

(4)

.0014 

Trace 

Trace 

. 00032 

. 00068

(4) 

. 00015 

Trace

Parts per 

million in 

water >

700 

350 

150 

150 

15

35

24

7 

7 

3.5

1.5

.7 

.7 

.7

. 15 

<. 52 

<. 52

. 035 

.07

. 015 

<. 015

0. 300 (pH 2.9)

Laboratory No. 231106

Sec. 16, T. 35 N., R. 47 W., 

Shannon County

Percent in 

residue 1

6.8 

3.2 

3.2 

1.5 

3.2

.15

.18 

.068 

.068 

.015

.0068 

.015 

.0068 

.0068 

.0032

.092

mW

Trace 

.0015 

.00068

. 00068 

. 00015 

. 00015

Parts per 

million in 

water '

850 

400 

400 

200 

400

20 

22 

8.5 

8.5 

2.0

.85 

2.0 

.85 

.85 

.4

11

<. 62 

.2 

.085

.085 

.02 

.02

0. 780 (pH 2.6)

i Logarithmic average of concentration range reported by semiquantitative spectrographic analyses 

(table 6).

» Computed from semiquantitative spectrographic analyses (table 6), this figure Is accurate to plus or 

minus one half reported value.

s Chemical determinations from residue. Analysts: J. Schuch and R. Dufour.

< Not detected,

»Chemical determinations from water. Analyst: T. Miller.

A statistical study of the spectrographic analyses from 82 samples 

of black shale followed a method outlined by A. L. Miesch (written 

communication, 1954), in which logarithmic averages were assigned to 

each concentration range detected spectrographically (table 6).
URANIUM, SHARON SPRINGS MEMBER, PIERRE SHALE 597

TABLE 6. Numbers and symbols used in referring to semiquantitative spectrographic 

analyses of Sharon Springs member

Concentration range (percent)

More than 10___---________________-_____ __ ____

5-10 ________ ____ . ____ __....___ _____

2-5-__-_-_--_-_______________________-____-_

1-2 ______ ___________ _____ . __ -._ _-_

.5-1.0_________________________________._____

.2- .5. ______ __.__.__.-_._ ____ . _____ _

.1- .2

.05- .1.- ___ _________ ____ _____________ _ -

.02- .05 __ ___ ____ ____ __ _______ _ _______

.01- .02______. _______________________________

,005- .01_ _______ _________ ____ ____________

.002- .OQ5__ __ _ __ _ ____ __________ ________

,001- .002________ ____ _____________ ____ ___

,0005- .001_____.__ __ ____ __ _______ _ _ ___ _'

.0002- .0005. _ _ ____ _ ____________ _ _

.0001- .0002--_________ _ __ _ _________________

,00005- .0001_________ __ ____ _ ____ _ _________

.00002- .00005 _ __._ _____ __ _ __ __

,00001- .00002_-___._. ___________________________

Logarithmic average (percent) '

6. 8

3.2

1.5

.68

. 32

.15

.068

.032

.015

.0068

. 0032

.0015

. 00068

. 00032

. 00015

. 000068

. 000032

. 000015

Symbol used 

on figure 92

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

i This figure was used in the statistical treatment of the samples.

These samples were collected from 30 localities to be representative of 

unweathered black shale containing no appreciable bentonite or lime. 

Chemical and radiometric determinations indicate that the samples 

have an average uranium content of 0.003 percent.

The mean concentration and range in concentration of the elements 

present in the Sharon Springs member are plotted on a semilogarithmic scale (fig. 90). This is to conform with the logarithmic 

method used by the laboratory in reporting semiquantitative spectrographic data (table 6) and is at least tentatively substantiated by 

results of experiments by Ahrens (1953), who reports that trace 

elements are log-normally distributed in the earth's crust.

CORRELATION WITH URANIUM

The correlation between concentration of uranium and other elements in the Sharon Springs member (fig. 91) was determined statistically by means of correlation coefficients. A correlation coefficient is 

used to express the relationship of two variables as a single number. 

This coefficient ranges from a positive 1 to a negative 1, where 1 indicates a complete association of two components and a value of zero 

indicates that there is no association whatsoever between the two com-
598

Correlation coefficient

Negative

i i i i

Mo

X p

Fe 

x Nd 

x Ce 

*Cd 

x Lo 

V 

Cu 

Ni 

Cr 

xNb 

Co 

Bo 

Sr 

Yb (

, ,

' '

M^Hi^^MH^BM 

WMMM 

 MMI^MM 

»

xBe 

Pb 

Co

Sc « 

xLi Ve 

Mn 

K 

Zr

Y 

xZn x 

No

:

B 

Go 

Al

i tic a 

show 

relat 

>ercc 

3 amp 

[Sned

Calci 

few d 

Jires 

.ban 

:orre

iii«

Positive

EXPLANATION

JL lines at CUSand O.ZZ 

lower limits of cor- 

.on significance for 99 

snt and 95 percent of 

les, respectively 

ecor, 1946).

ilations based on too 

eterminations -above 

hold values to be more 

mere indications of 

lation.

FIGUBE 91. Diagram showing correlation between concentration of uranium and 32 

other elements in 82 samples of the Sharon Springs member of the Pierre shale, South 

Dakota and Nebraska.

ponents. A positive correlation indicates that the two components 

vary directly, whereas a negative coefficient indicates that they tend 

to vary inversely in relation to each other.

A good positive correlation was found between the content of 

uranium and molybdenum and the content of iron (fig. 91). A tentative correlation is indicated between the uranium content and the 

contents of phosphoros, neodymium, cerium, cadmium, and lanthanum. A strong negative correlation is shown between the content of 

uranium and the contents of aluminum, gallium, boron, titanium, 

magnesium, and sodium. A discussion of a few of these correlations 

follows.
URANIUM, SHARON SPRINGS MEMBER, PIERRE SHALE 599 

POSITIVE CORRELATION

In addition to positive relationships indicated for uranium with 

arsenic and selenium by chemical analyses, a positive correlation coefficient of 0.53 was found between uranium and molybdenum, and a correlation coefficient of 0.36 was found between uranium and iron (fig. 

91). This relationship may be explained in part by the fact that in a 

reducing environment hydrogen sulfide causes precipitation of all four 

elements in the original sapropelic sediments (Kankama and Bahama, 

1950, p. 637). Abundant pyrite in the shale of the Sharon Springs 

member, together with the positive correlation between uranium and 

iron, indicates that the environment in which uranium occurs in black 

shale is favorable for the occurrence and deposition of pyrite. Kecent 

work by E. D. Strahl and others at Pennsylvania State University 

(written communication, 1955) has disclosed a very strong correlation 

between the concentration of uranium and the abundance of pyrite in 

the Chattanooga black shale, confirming an association pointed out 

by McKelvey and Nelson (1950), Goldschmidt (1954, p. 566), and 

others. Autoradiography by Davidson and Ponsford (1954) indicates a tendency toward close association of uranium and pyrite in 

lignite.

The correlation between uranium and phosphoros results from high 

phosphate content of fish scales and bones and the corresponding high 

uranium content of that material (p. 587). Many of the shale zones 

showing particularly numerous fragments of such material have a correspondingly higher uranium content. This relationship may also 

hold for the samples that are very low in uranium, but confirmative 

data are lacking because the phosphorus content of such samples is 

below the amount detectable by semiquantitative spectrographic 

methods (table 3). The tentative correlation between uranium and the 

elements neodymium, cerium, cadmium, and lanthanum is little understood. These rare elements may be associated with phosphatic 

material.

NEGATIVE CORRELATION

Most of the elements showing a strong negative correlation with 

uranium (fig. 91) are common in clay and other inorganic allogenic 

detrital material, indicating that the most concentrated accumulations 

of uranium are in association with organic material. These elements 

include aluminum, magnesium, and sodium as clay minerals, and gallium associated with aluminum (Rankama and Sahama, 1950, p. 727). 

Boron and titanium are thought to be mainly present as detrital 

minerals boron being one of the constituents of tourmaline, and titanium, being found in sphene, ilmenite, rutile, brookite, and anatase.
600 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM 

RELIABILITY OF THE CORRELATIONS

Because of ever-improving techniques of spectrographic analysis, 

and because of the ease with which large numbers of samples may be 

analyzed for a suite of as many as 60 elements, so much data are 

amassed that they can be interpreted only by statistical methods. 

Table 6 shows the ranges used in reporting concentrations determined 

by the semiquantitative spectrographic method, and it also shows the 

numerical amount assigned to each range for the purpose of statistical 

study. The histograms (fig. 92) present a condensation of the data 

on which the statistical study is based by showing the number of 

samples (of a possible 82) reported by the laboratory to contain a 

given concentration of the elements studied. In order to treat statistically the semiquantitative spectrographic analyses of all 82 samples 

for the 25 elements shown on figure 92, concentrations reported as 

"trace" or "zero" by the laboratory were arbitrarily assigned percent 

vajues relative to the lowest amount generally detectable by semiquantitative spectrographic methods (table 3).

ENVIBONMENT OF DEPOSITION

The overall chemical environment of deposition and diagenesis of 

the Sharon Springs member of the Pierre shale was reducing, as is 

indicated by its sapropelic nature. In common with other marine 

uranium-bearing black shales (McKelvey and Nelson, 1950, p. 43), 

the Sharon Springs is noncalcareous and highly carbonaceous. It is 

high in sulfides and somewhat phosphatic (due largely to fish remains), and it probably accumulated slowly, as is evidenced by the 

high proportion of organic matter (plant and fish remains) to allogenic sediments. That the source of the sediments lay to the west is 

indicated by the sandstones and light-colored shales which interfinger 

with the black shales in eastern Montana and Wyoming, by the fact 

that the thicker bentonites in the Sharon Springs member are also 

found in the western part of South Dakota, and by the westward 

thickening of the Sharon Springs member.

The depth at which the Sharon Springs sediments accumulated is 

inferred from the following evidence to have been less than 250 feet : 

(1) the excellent state of preservation of the long delicate shells of 

Baculites found along the southeastern flank of the Black Hills indicate that the water may have been quiet and fairly shallow (W. A. 

Cobban, written communication, 1955); (2) the marl of the Gregory 

member directly overlying the Sharon Springs in the Missouri Eiver 

valley contains Foraminifera typical of the neritic zone and probably 

representing a depth no greater than 250 feet (Steven K. Fox, U. S. 

National Museum, written communication, 1955); and (3) thin zones
URANIUM, SHARON SPRINGS MEMBER, PIERRE SHALE 601

HI -

I C 00

K\ ~ S » 3 ° o o ? ° ° 

la \f i i i i r in pj _ a| S°oo2~-oOo
602 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

of coarse fragments of fish scales and bones found at a few localities 

are thought to represent a lag concentration from an underwater surface eroded by wave action.

ORIGIN OF URANIUM

The uranium appears to have been emplaced in a reducing environment during deposition and diagenesis of the shale, the highest concentrations of uranium being found where deposition of allogenic 

sediments was probably the slowest. Most of the uranium appears to 

be associated with the organic constituents of the shale.

The fact that the peak in radioactivity lies just above the bentonitic 

sequence may be due to fortuitous circumstances. Or, as suggested by 

Tourtelot(1956),

* * * the volcanic ash deposited in the sea probably would have released much 

of its metal content, including uranium, in the early stages of its alteration to 

bentonite and thus would have increased the metal content of the waters of the 

Sharon Springs area.

This also may explain uranium-rich layers where no bentonites are 

present, for the absence of bentonites by nondeposition or erosion still 

permits the distribution throughout the sea of the elements derived 

from bentonites.

CONCLUSIONS

The study of the Sharon Springs member in South Dakota and 

northeastern Nebraska leads to the following conclusions:

1. The Sharon Springs member of the Pierre shale is a lithologic 

unit which may be traced from exposures and from subsurface information throughout most of South Dakota and North Dakota and 

adjacent areas to the south.

2. Most of the member accumulated under quiet water, probably 

less than 250 feet deep, and the source of the sediments was mainly 

to the west.

3. The uranium is held, at least in part, by phosphatic material 

such as fossil fish bones and scales and in part by carbonized macerated 

plant remains.

4. The vertical distribution of uranium content in the member is 

thought to be a function of the uranium content of the sea water 

following the deposition of volcanic ash now altered to bentonite.

5. The highest uranium content in the Sharon Springs member is 

about 0.025 percent, in beds no thicker than 5 inches. The uranium 

content of the entire member averages about 0.0015 percent higher 

than any average hitherto reported for black shales of post-Paleozoic
URANIUM, SHARON SPRINGS MEMBER, PIERRE SHALE 603 

SELECTED REFERENCES

Ahrens, L. H., 1953, A fundamental law of geochemistry: Nature, v. 172, p.

1148. 

Beers, R. F., and Goodman, Clark, 1944, Distribution of radioactivity in ancient

sediments: Geol. Soc. America Bull., v. 55, p. 1229-1254. 

Breger, I. A., 1955, Radioactive equilibrium in ancient marine sediments:

Geochim. et Cosmochim. Acta, v. 8, p. 63-73. 

Breger, I. A., and Schopf, J. M., 1955, Germanium and uranium in coalifled

wood from Upper Devonian black shale: Geochim. et Cosmochim. Acta, v.

7, p. 287-293. 

Cobban, W. A., 1952, Cretaceous rocks on the north flank of the Black Hills

uplift: Billings Geol. Soc. Guidebook, 3d Ann. Field Conf., p. 86-88. 

Cobban, W. A., and Reeside, J. B., Jr., 1952, Correlation of the Cretaceous formations of the western interior of the United States: Geol. Soc. America

Bull., v. 63, p. 1011-1044. 

Condra, G. E., and Reed, E. C., 1950, Geologic map of Nebraska: Nebraska State

Geol. Survey. 

Davidson, C. F., and Ponsford, D. R. A., 1954, On the occurrence of uranium in

coals: Mining Mag., v. 91, p. 265-273. 

Dunham, R. J., 1955, Sharon Springs black shale in the Chadron area, Nebraska

and South Dakota, in Geologic investigations of radioactive deposits Semiannual progress report, Dec. 1, 1954, to May 31, 1955: U.S. Geol. Survey

TEI-540, p. 164, issued by U.S. Atomic Energy Comm. Tech. Inf. Service,

Oak Ridge, Tenn. 

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Gesell. Wiss. Gottingen, Math.-physik. Klasse, IV, Neue Fortsetzung 1, no.

2, p. 11. 

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

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

Gries, J. P., 1942, Economic possibilities of the Pierre shale: South Dakota

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Gries, J. P., and Rothrock, E. P., 1941, Manganese deposits of the lower Missouri

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96 p. 

Landis, E. R., 1959, Radioactivity and uranium content of the Sharon Springs

member of the Pierre shale and associated rocks in western Kansas and

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grinding as determined spectrographically: Am. Jour. Science, v. 251, p.

814-830.
604 CONTRIBtJTIONS TO THE GEOLOGY OP URANIUM

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Missouri Valley in South Dakota: South Dakota State Geol. Survey Rept.

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40, p. 62-83.
Contributions to the 

Geology of 

Uranium, 1956

GEOLOGICAL SURVEY BULLETIN 1046

This bulletin was printed 

as separate chapters A-R

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1959
UNITED STATES DEPARTMENT OF THE INTERIOR 

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director
CONTENTS

[The letters in parentheses preceding the titles designate separately published chapters]

Page

(A) Inferred relationship of some uranium deposits and calcium carbonate

cement in southern Black Hills, South Dakota, by G. B. Gott___ 1

(B) Rare-earth-bearing apatite at Mineville, Essex County, New York, by

F. A. McKeown and Harry Klemic_______________________ 9

(C) Uranium-bearing minerals in placer deposits of the Red River Valley,

Idaho County, Idaho, by F. C. Armstrong and P. L. Weiss_____ 25

(D) Uranium resources of the San Rafael district, Emery County, Utah 

a regional synthesis, by H. S. Johnson, Jr____________________ 37

(E) Reconnaissance for uranium in asphalt-bearing rocks in the Western

United States, by W. J. Hail, Jr_______________________ 55

(F) Notes on the geology of uranium, by M. R. Klepper and D. G. Wyant_ 87 

(G) Uranium in carbonaceous rocks in the Townsend and Helena Valleys,

Montana, by G. H. Becraft______________________ 149

(H) Geology of the Jomac mine, White Canyon area, San Juan County,

Utah, by A. F. Trites, Jr., and G. A. Hadd______________ 165 

(I) Geology of Majuba Hill, Pershing County, Nevada, by A. F. Trites,

Jr., and R. H. Thurston_________________________ 183 

(J) Geologic features of areas of abnormal radioactivity south of Ocala,

Marion County, Florida, by G. H. Espenshade.____________ 205

(K) Results of geologic exploration by core drilling, 1953, land-pebble

phosphate district, Florida, by S. H. Cathcart and McGreevy____ 221 

(L) Radioactivity and uranium content of the Sharon Springs member of

the Pierre shale and associated rocks in western Kansas and eastern

Colorado, by E. R. Landis________________________ 299 

(M) Reconnaissance investigations of uranium occurrences in the Saratoga

area, Carbon County, Wyoming, by H. G. Stephens and M. J.

Bergiu______________________________________ 321 

(N) Preliminary study of radioactive limonite in Colorado, Utah, and

Wyoming, by T. G. Levering and E. P. Beroni______________ 339

(O) Reconnaissance for radioactivity in metal mining districts of the San

Juan Mountains of Colorado, by C. T. Pierson, R. A. Weeks, and

A. G. Kleinhampl_______________________________ 385 

(P) Uranium deposits in Dripping Spring quartzite, Gila County, Arizona,

by H. C. Granger and O. B. Raup___________________________ 415

(Q) Stratigraphy of Triassic and associated formations in part of the

Colorado Plateau area, by J. H. Stewart, G. A. Williams, H. F.

Albee, and O. B. Raup__________________________ 487 

(R) Uranium in Sharon Springs member of Pierre shale, South Dakota and

northeastern Nebraska, by R. C. Kepferle-_______________ 577