Stratigraphy of the 

Pierre Shale, Valley City and 

Pembina Mountain Areas 

North Dakota

GEOLOGICAL SURVEY PROFESSIONAL PAPER 392-A
Stratigraphy of the 

Pierre Shale, Valley City and 

Pembina Mountain Areas 

North Dakota

By JAMES R. GILL and WILLIAM A. COBBAN

STUDIES OF THE PIERRE SHALE IN THE NORTHERN GREAT PLAINS

GEOLOGICAL SURVEY PROFESSIONAL PAPER 392-A

Five lithologic subdivisions of the Pierre Shale in 

eastern North Dakota correlated with equivalent 

rocks in central South Dakota^ eastern Wyoming^ 

central Montana^ and southern Manitoba

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1965
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

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

Washington, D.C. 20402 - Price 25 cents (paper cover)
CONTENTS

Page

Abstract. __________________________________________ Al

Introduction.. ______________________________________ 1

Stratigraphy _______________________________________ 6

Pembina Member.._____________________________ 6

Gregory Member.______________________________ 10

DeGrey Member______________________________ 14

Odanah Member_______________---______.--___ 15

Reference sections_____--.___-_-_________-_____--__ 17

Literature cited___________________________________ 19

ILLUSTRATIONS

Page

FIGURE 1. Index map showing localities discussed in text-._____________-_________________-_-___-_-___-_---_------- Al

2. Maps showing location of reference sections and fossil collections, Valley City and Pembina Mountain areas__. 2

3. Ammonite sequence and correlation chart for Campanian and lower Maestrichtian rocks._____________________ 4

4. Correlation chart of lower part of Pierce Shale in eastern North Dakota and central South Dakota..----------- 5

5. Photograph of interbedded bentonite and organic-rich shale in lower part of Pembina Member._______________ 6

6. Correlation chart of groups of bentonite in lower part of Pembina Member.__________-_--__-_-___----------- 8

7. Photograph of Pierre Shale exposed in roadcut east side of Sheyenne River______________--_----__- __-_ 12

HI

STUDIES OF THE PIERRE SHALE IN THE NORTHERN GREAT PLAINS

STRATIGRAPHY OF THE PIERRE SHALE, VALLEY CITY AND PEMBINA MOUNTAIN AREAS'

NORTH DAKOTA

By JAMES R. GILL and WILLIAM A. COBBAN

ABSTRACT

Reconnaissance examination of widely scattered outcrops of 

Upper Cretaceous rocks in the heavily glaciated areas of eastern 

North Dakota provides the basis for the first formal subdivision 

of the Pierre Shale in these areas. Five distinct units are 

present which can be related by both lithology and fossil content 

to equivalent units in the type Pierre Shale of central South 

Dakota and to units in the Vermilion River and Riding Mountain 

Formations of Manitoba. Existing stratigraphic names in current usage in Manitoba and central South Dakota are applied 

to four of the five members of the Pierre recognized in North 

Dakota. The Manitoba name Pembina is applied to the basal 

member of the Pierre, and the South Dakota names Gregory 

Member and DeGrey Member have been assigned to the two 

succeeding younger members. The Manitoba name Odanah is 

assigned to the hard siliceous shale that overlies the DeGrey 

Member. The fifth and youngest member of the Pierre Shale 

exposed in eastern North Dakota remains unnamed because of 

a lack of adequate stratigraphic and faunal data.

INTRODUCTION

Much of the Pierre Shale of Late Cretaceous age is 

exposed in two main areas in North Dakota (fig. !):(!) 

the Valley City area in the central southeastern part of 

the State and (2) the Pembina Mountain area along the 

international boundary in the northeastern part of the 

State. The two areas are about 150 miles apart. Glacial 

deposits cover the Pierre Shale in the eastern part of 

the State except for isolated exposures of a few feet or a 

few tens of feet of strata in some of the deeper valleys. 

Although known for many years, the outcrops of the 

Pierre in North Dakota yielded few fossils, and the 

relations of these strata to the type section of the Pierre 

Shale along the Missouri River in South Dakota were 

not determined.

As part of the stratigraphic studies involved in the 

geochemical investigations of the Pierre Shale and its 

stratigraphic equivalents (Tourtelot, 1962; Tourtelot, 

Schultz, and Gill, 1960; Gill and Cobban, 1961, 1962), 

we made a reconnaissance study of the Valley City and 

Pembina Mountain areas because these exposures include the northeasternmost strata of the Pierre Shale

available for study. They thus are important in studying the paleogeography of the eastern part of the Pierre 

basin of deposition. In addition, the outcrops in North 

Dakota provide an important datum point for better 

understanding of the Pierre equivalents to the north 

in Manitoba and Saskatchewan.

105° 103 c 101

43

FIGURE 1. Localities discussed in text.

200 MILES

_J

Al
A2 STUDIES OF THE PIERRE SHALE IN THE NORTHERN GREAT PLAINS

In the Valley City area (fig. 2J.), the Sheyenne River 

has cut through the thin veneer of glacial deposits that 

mantle the upland surface and has formed a valley 150 

to 175 feet deep and about a mile wide. Moderately good 

exposures of the Pierre Shale and the underlying 

Niobrara Formation are present in the bluffs of the 

river and its major tributaries. These exposures extend 

from Valley City southward for a distance of about 

25 miles to the vicinity of Fort Ransom. A few miles 

east of Fort Ransom 100 feet or more of pale-yellowishorange-weathering marlstone beds of the Niobrara Formation is exposed in roadcuts along the Sheyenne River. 

The lower 175 feet of the Pierre Shale and the upper few 

feet of the Niobrara Formation are exposed in roadcuts 

near Little Yellowstone Park (fig. 2J., loc. 5). These 

outcrops consist of about 50 feet of hard dark' shale 

overlain by about 120 feet of pale-yellow-weathering 

calcareous shale and marlstone. North of this locality, 

in the vicinity of Kathryn, there are good exposures of 

the basal dark shale and the overlying calcareous beds. 

Between Kathryn and Valley City, dark-gray to black 

bentonitic shales containing abundant black manganifEXPLANATION

Type locality of Pembina Member of 

Vermilion River Formation

Section after Wickenden (1945)

Pembina River section

©(§> 

Tongue River section

® 

North Valley City section

© 

Little Yellowstone Park section

x 

Fossil localities

98°

R 58 W. 57 56 R 55 W.

A. VALLEY CITY AREA, NORTH DAKOTA

R 64 W 63 62 61 60 59 58 57 56 R 55 W.

B. PEMBINA MOUNTAIN AREA, MANITOBA AND NORTH DAKOTA

10 20

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30 MILES 

_I

FIGURE 2. Location of reference sections and fossil collections, Valley City and Pembina Mountain areas.
STRATIGRAPHY, PIERRE SHALE, EASTERN NORTH DAKOTA A3

erous concretions overlie the calcareous beds and crop 

out high on the valley walls of the Sheyenne River. 

These dark shales slump extensively but form a striking dark band that is generally bare of vegetation and 

that contrasts sharply with the underlying light-colored 

calcareous beds.

The Pembina Mountain area as defined in this report 

follows the usage of Upham (1895). It includes the 

200- to 300-foot-high east-facing escarpment that extends from near the town of Park River (fig. 2B) in 

northeastern North Dakota north-northwestward about 

100 miles to near the town of Treherne in southern 

Manitoba. This imposing topographic feature, though 

not a mountain in the strict sense, has been referred to 

as Pembina Mountain or second mountain since the 

establishment of the first settlement in the region. D. D. 

Owen visited the area in 1848 during the course of his 

geological survey of Wisconsin, Iowa, and Minnesota, 

and remarked that Pembina Mountain was really a terrace or tableland which originally formed the ancient 

shore of a great body of water, glacial Lake Agassiz 

(Owen, 1852, p. 178). Pembina Mountain has also been 

referred to at various times as the Pembina Escarpment 

(Dawson, 1881, p. 15A), Manitoba Escarpment (Tyrrell, 1890), Second Pembina Mountain and Pembina 

Mountain (Upham, 1895, p. 41), Pembina Mountains 

(Leonard, 1904, p. 147), and Pembina Hills (Laird, 

1951).

The upper surface of Pembina Mountain is a relatively smooth gently westward sloping surface cut on 

nearly horizontal beds of hard siliceous shale in the 

upper part of the Pierre, which are in turn covered by 

a thin layer of glacial drift. The steep eastern face of 

Pembina Mountain is heavily wooded, and bedrock exposures are poor except along the major streams and 

rivers that breach the mountain front. Good exposures 

are to be found along tlie North, Middle, and South 

Branches of the Park River, the Tongue River, and 

the Little Pembina and Pembina Rivers. A part of the 

Niobrara Formation and 100 feet or more of Pierre 

Shale can be seen along many of these drainages. The 

Pierre Shale of this area consists of a basal unit about 

80 feet thick of moderately hard dark organic-rich shale 

containing numerous beds of bentonite. These beds are 

overlain by about 50 feet of lighter colored calcareous 

and bentonitic shale that slumps extensively. The calcareous shale is capped by from 65 feet to more than 100 

feet of light-gray hard siliceous shale which forms the 

bedrock surface of much of the Pembina Mountain area.

Upham (1895), in his monograph on the glacial Lake 

Agassiz, is the first geologist known to us to record the 

Pierre Shale in eastern North Dakota. The most extensive investigations of the Pierre were conducted by

the State Geological Survey of North Dakota in the 

early 1900's. These studies were concerned largely with 

the economic potential of the clays and marls of the 

Pierre for the manufacture of brick and cement, although some attempt was made to correlate units within 

the Pierre. Results of these investigations were published by Leonard (1904, 1906), Babcock and Clapp 

(1906), Barry and Melsted (1908), and Kline (1942). 

A very cursory examination of the Pierre along the 

Sheyenne River apparently was made by Willard 

(1909) during his mapping of the glacial deposits of 

the Jamestown and Tower quadrangles.

The stratigraphic succession of lithologic units within 

the Pierre Shale in eastern North Dakota and in South 

Dakota remained largely unknown for many years. It 

was not until 1937 that the type Pierre of central South 

Dakota was described in detail and the stratigraphic 

framework for the formation was established by Searight (1937). The first and apparently only attempt 

to relate the Pierre Shale of North Dakota to the type 

sequence in South Dakota was by Kline (1942, p. 355), 

who suggested that calcareous beds cropping out at 

Valley City, N. Dak., might be equivalent to chalk beds 

in the upper part of the Gregory Member of Searight 

(1937) of the Pierre Shale in South Dakota. Leonard 

(1904, p. 152-153) originally assigned these calcareous 

beds in North Dakota to the Pierre, but later (1906, p. 

69) he assigned them to the Niobrara Formation as did 

most subsequent workers.

Our correlation of the Pierre Shale of eastern North 

Dakota (figs. 3, 4) is based on an examination of outcrops in the Valley City and Pembina Mountain areas. 

Detailed sections were measured and fossil collections 

were made in each of these areas. In addition, many of 

the readily accessible scattered outcrops between the 

two areas were visited. Our observations have been 

supplemented by unpublished stratigraphic data obtained by H. A. Tourtelot of the U.S. Geological Survey 

in a previous reconnaissance of the Pierre Shale in eastern North Dakota. Dr. Wilson M. Laird, State Geologist of North Dakota, Dr. F. D. Holland, Jr., Mr. 

Rodney Feldmann, and Mr. A. M. Cvancara, of the Department of Geology, University of North Dakota, contributed generously of their knowledge of the geology 

of the region and reviewed the final manuscript. Data 

concerning the Pierre equivalents in the adjacent part of 

Manitoba were obtained in the course of a brief reconnaissance we made in the summer of 1963. Stratigraphic data for the Pierre Shale along the Missouri River 

in central South Dakota are based on our observations, 

on unpublished material supplied by Tourtelot and L. 

G. Schultz of the U.S. Geological Survey, and on the 

published record.
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A6 STUDIES OF THE PIERRE SHALE IN THE NORTHERN GREAT PLAINS

The Pierre Shale outcrops in eastern North Dakota 

which we examined are divisible into four major lithologic units. They are, from oldest to youngest, (1) 

dark-gray to brownish-black shale that contains numerous thin beds of bentonite in the lower part, (2) lightweathering calcareous shale and marlstone, (3) bentonitic shale and claystone that contains abundant manganiferous ironstone concretions, and (4) light-gray hard 

siliceous shale. In addition, a fifth unit of soft dark 

shale, not seen by us, was described by Barry and Melsted (1908, p. 180) as overlying the light-gray hard 

siliceous shale. This last unit appears to have been 

largely eroded from eastern North Dakota. We believe 

that new names are not necessary for any of the lower 

four units; the Manitoba names Pembina and Odanah 

can be applied to the oldest and the youngest, whereas 

the South Dakota names Gregory and DeGrey fit the 

remaining units. Figure 4 shows the probable position 

of ammonite zones in these lower four units and the correlation of these units with the type Pierre Shale of 

central South Dakota.

STRATIGRAPHY

FEMBINA MEMBER

The Pembina Member, the lowest unit of the Pierre 

Shale in the Pembina Mountain area, was originally 

defined by Kirk (1930, p. 130B) as the Pembina Beds 

and was treated by him as the uppermost of three members of the Vermilion River Formation. The member 

was named for exposures on Pembina Mountain and 

along the Pembina River valley in southern Manitoba. 

Pembina Mountain lies partly in North Dakota and 

partly in Manitoba, and the Pembina River cuts through 

the mountain in both areas (Upham, 1895, pi. 9). Kirk 

described the member as consisting of no more than 

80 feet of dark noncalcareous shale resting on the lighter 

colored speckled calcareous Boyne Member of the Vermilion River Formation (Niobrara Formation of North 

Dakota). Along Pembina River, 4 miles north of the 

North Dakota boundary, Kirk noted that the lower 11 

feet of the Pembina Member contained at least 6 beds 

of bentonitic clay and formed a very striking unit known 

as the black and white beds. The remainder and greater 

part of the member he described as black and chocolatebrown shale, of which the latter was very fissile and 

contained abundant macerated fish remains. Later, 

Wickenden (1945, p. 43-44) visited the same locality 

and presented a more detailed surface section as well 

as a bore-hole section. According jto Wickenden the 

total thickness of the member is a little more than 80 

feet. In the lower 18 feet, he measured 18 layers of 

cream-colored bentonite, each 0.8 foot or less thick, 

whereas in the rest of the member he recorded only 9

very thin layers of bentonite. More recently Tovell 

(1948, p. 4, diagram 47-7B) mentioned the twofold division of the Pembina Member and included many graphic sections of the member along the Pembina River. 

The main bentonite-bearing part of the Pembina Member is pictured on figure 5; it has also been presented 

by Wickenden (1945, pi. 4, fig. b) and by Davies and 

others (1962, pi. 19, fig. A).

The strata making up the Pembina Member continue 

southward into North Dakota along Pembina Mountain, 

where they form the lowest member of the Pierre Shale. 

We know of no reason why the name Pembina cannot 

be applied to these strata in North Dakota, especially 

as the type locality is on the same escarpment. Accordingly, the name Pembina Member of the Pierre Shale is

FIGURE 5. Interbedded bentonite (light bands) and organic-rich shale 

(dark bands) in the lower part of the Pembina Member of the Pierre 

Shale exposed in roadcut near the Pembina River in the SW% sec. 30, 

T. 163 N., R. 57 W., Cavalier County, N. Dak. (See Pembina River 

section.) Man is standing at the contact between the Pierre and 

Niobrara; thin beds of shale and bentonite just above the Niobrara 

may be equivalent to the Gammon Ferruginous Member of the Pierre 

Shale.
STRATIGRAPHY, PIERRE SHALE, EASTERN NORTH DAKOTA A7

given to these rocks in eastern North Dakota. The rocks 

of the Pembina Member are lithologically similar to the 

Sharon Springs Member of the Pierre Shale along the 

Missouri Kiver in central South Dakota and extension 

of that name into North Dakota has been considered 

by us. We believe that the usage of the name Pembina, 

which has its type locality a few miles north of the international boundary, is preferable to extending the 

name Sharon Springs 700 miles from its type locality 

in western Kansas (Elias, 1931, p. 58-77).

The rocks herein assigned to the Pembina Member 

in the Pembina Mountain area were first described by 

Leonard (1904, p. 148), who presented a generalized 

stratigraphic section along the Tongue River, which is 

the next major drainage south of the Pembina Kiver. 

Leonard noted that gray calcareous shale, assigned to 

the Niobrara Formation, was separated from bluishgray clay shale, assigned to the Pierre Shale, by a 

black carbonaceous shale unit which he apparently believed to be part of the Pierre, although he did not 

definitely state so. This black shale unit was described 

in two parts a lower 6- to 8-foot unit of "black, carbonaceous clay shale layers alternating with white clay 

seams," (see fig. 5) and an upper 60-foot unit of "black 

and highly carbonaceous shale * * * cut by joints and 

irregular cracks which are filled with gypsum" and 

containing "occasional thin layers of white clay toward 

the base." In a subsequent paper Leonard (1906, p. 

68-71) definitely assigned these beds to the Pierre Shale 

and observed that the "black and white bands" persisted over a great area. The "white bands" were described later by Barry and Melsted (1908, p. 172) as 

"yellow layers." These layers were also termed "fullers 

earth" by Kline (1942, p. 354), who gave a section 

through the lower part of the Pierre Shale near the 

Tongue River. Her section can be summarized as a 

lower part of 13 feet of black shale, alternating with 

more than 17 thin layers of "fullers earth," and an upper 

part of 58 feet of black shale that has "fullers earth partings" in the lower 8 feet and abundant selenite crystals 

in the overlying part. Kline believed the "fullers 

earth" beds to be local in distribution, although 

Leonard (1906, p. 71) and Barry and Melsted (1908, 

p. 172) had earlier pointed out their wide distribution 

and Leonard (1919, p. 10) even drew attention to a 

2-inch bed that could be traced for 25 miles. More 

recently Laird (1951, p. 12) suggested that these "fullers earth" clays were probably bentonite that came 

from volcanoes several hundred miles away.

Regional stratigraphic studies of the Pierre Shale and 

equivalent rocks farther west in the Dakotas and adjacent States indicate that the bentonite beds in the lower 

part of the Pembina Member and equivalent units 

(Sharon Springs Member of the Pierre Shale, and the

Claggett Shale) are the result of an extended period of 

explosive volcanism that took place some 700 miles west 

of Pembina Mountain, in the general area of the Elkhorn Mountains of western Montana. We believe that 

these bentonites may be equivalent to a part or all of 

the 2,500 feet of welded tuff and ash-fall crystal tuff 

that make up the middle member of the Elkhorn Mountains Volcanics (Klepper, Weeks, and Ruppel, 1957, 

p. 32) in the area between Helena and Three Forks, 

Mont. These bentonites may also be the lateral equivalents of ash-flow and welded tuffs that make up a part 

of the western facies of the Two Medicine Formation 

(Schmidt, 1963) in the area of Wolf Creek, Mont.

The apparent purity of the bentonite and the uniform 

thickness and lateral persistence of individual beds suggest that each bed may represent one or more ash falls. 

The continuity of groups of bentonite beds in the Pembina Mountain area of Manitoba and North Dakota 

is shown in figure 6. These bentonite beds are distinctive features in time-equivalent rocks throughout much 

of the Dakotas, Montana, Wyoming, Nebraska, Colorado, and the adjacent Provinces in Canada. The beds 

thus far examined are dominantly calcium bentonite 

(nonswelling). They range from a fraction of an inch 

to several feet in thickness, the thicker beds being more 

common in the western areas closer to the source of the 

ash. These bentonites have been mined for many years 

in the Miami-Thornhill area in southern Manitoba.

The Pembina bentonites are unusually absorbent and 

are used extensively in Canada in the bleaching of petroleum and fatty oils (Gallay, 1938, p. 9; Bannatyne, 

1963, p. 9-18). Equivalent bentonites in the Dakotas 

probably have the same desirable physical and chemical 

properties, but at the present time they are not being 

exploited. A small quantity of bentonite has been 

mined from the basal bed (Ardmore Bentonite Bed of 

Spivey, 1940) of the Sharon Springs Member of the 

Pierre Shale in the vicinity of Buffalo Gap and Ardmore in the southern Black Hills (Connolly and 

O'Harra, 1929, p. 326; Spivey, 1940, p. 1).

We examined the Pembina Member in the valleys of 

the Pembina and Tongue Rivers in the Pembina Mountain area. A composite section in the Tongue River 

area revealed about 75 feet as the total thickness of the 

member; an 80-foot thickness was determined by Wickenden (1945, p. 43-44) at a locality in southern Manitoba about 21 miles north of Tongue River.

The lower or bentonite-rich part of the member is 

well exposed along the main road in the Pembina River 

valley about 7 miles west of Walhalla in the SW^ sec. 

30, T. 163 N., R. 57 W. (see Pembina River section; also 

figs. 5, 6), and near the old cement plant on the Olson 

Farm on the Tongue River in the NEi/4 sec. 25, T. 161 

N., R. 57 W. In the Pembina River valley, where the
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STRATIGRAPHY, PIERRE SHALE, EASTERN NORTH DAKOTA A9

bentonite-rich part of the member is nearly 10 feet 

thick, a threefold division is apparent. The lower 2 

feet contains eight very thin layers of bentonite of which 

only the uppermost is as much as 3 inches thick. This 

sequence of beds may be a partial time equivalent of 

the Gammon Ferruginous Member of the Pierre Shale. 

This basal group of thin bentonites is separated from an 

upper and thicker group of bentonites by 1.5 feet of 

shale devoid of bentonite. The upper group of bentonite beds is about 5 feet thick and contains eight or 

more layers of bentonite many of which are 5 or 6 

inches thick and none of which are separated by more 

than 8 inches of shale. The threefold division of the 

bentonite-rich part of the Pembina Member apparently 

thickens northward into Manitoba, as indicated by the 

section on the Pembina Eiver measured by Wickenden 

(1945, p. 43-44). The lower part of Wickenden's section can be summarized, from bottom to top, as follows: 

(1) A 6.5-foot unit of shale containing 9 layers of bentonite, (2) a 4.9-foot unit of shale that lacks bentonite, 

and (3) a 7.4-foot unit of shale containing 10 layers of 

bentonite none of which is separated by more than 1.7 

feet of shale (fig. 6).

The upper or main part of the Pembina Member is 

well exposed in the vicinity of the Tongue River retention dam T-3-5 in the NE^4 sec. 24, T. 161 N., E. 57 W. 

(See Pembina Mountain section, units 29-31.) There 

it is 67 feet thick and consists chiefly of dark-gray to 

brownish-black shale that contains only a few thin layers 

of bentonite. Yellowish seams of jarosite and colorless 

plates of selenite are common. Small brown fishbones 

and fish scales are abundant. Gypsum-encrusted phosphate nodules are present in the upper 15 feet. Gypsiferous limonitic baculites are present sparingly, but 

none is sufficiently well preserved for determination to 

species. Barry and Melsted (1908, p. 184) measured 

the lower 35 feet at a locality about 8 miles farther south, 

where they described the material herein referred to 

as jarosite as forming bright-yellow hard crusts that 

resembled sulfur but tested like earthy limonite.

In the Sheyenne Eiver area only the upper part of 

the Pembina Member is present, and it is exposed about 

20 miles south of Valley City. The upper part of the 

Pembina Member rests directly on the Niobrara Formation, as outcrops show in the new cut on the north side 

of North Dakota Highway 46 on the east side of 

Sheyenne Eiver valley. (See Little Yellowstone Park 

section, units 5-12.) Here the Pembina Member is 

44 feet thick and consists chiefly of grayish-brown to 

brownish-black shale that contains gypsum-encrusted 

phosphate nodules in the upper half and yellowishorange jarosite seams throughout much of the member. 

A few ironstone concretions are present in the interval 

14-17 feet above the base. Bentonite is represented by

two thin closely spaced layers at the base and by two 

beds in the upper half of the member. A few poorly 

preserved gypsiferous limonitic baculites are present 

in the lower 13 feet, and one well-preserved specimen of 

Baculites perplexus Cobban was found in a small ironstone concretion 14 feet above the base.

The member correlates with the Claggett Shale of 

central Montana, with the Sharon Springs and Mitten 

Black Shale Members of the Pierre Shale of the 

southern part of the Black Hills of South Dakota and 

eastern Wyoming, and with the Sharon Springs Member of the Pierre Shale in the Missouri Eiver valley of 

south-central South Dakota (fig. 3).

The Claggett Shale of Montana is a dark-gray to 

dark-brownish-gray shale that contains a conspicuous 

group of closely spaced beds of bentonite in the lower 

part and a few thin layers in the higher part. It can 

be readily correlated with the Pembina Member by its 

lithologic character but timewise it correlates with perhaps only the lower half of the Pembina Member. The 

Claggett Shale, in its type area at the mouth of the 

Judith Eiver in central Montana, contains Baculites 

obtusus Meek in the bentonite-rich basal beds, B. 

mcleami Landes just above the bentonite-rich beds, and 

B. asperiformis Meek in the uppermost part of the 

formation. The presence of the slightly younger B. 

perplexus Cobban above the bentonite-rich part of the 

Pembina Member in North Dakota reveals a younger 

age for the upper part of that member than for the 

top of the Claggett Shale.

The Sharon Springs and Mitten Black Shale Members of the Pierre Shale in the southern Black Hills 

region are also dark shales that can be correlated with 

the Pembina Member by their lithology. The Sharon 

Springs is a dark-gray fissile shale that resists weathering and .tends to form ridges and steep-walled gullies. 

The shale is organic-rich and contains an abundance of 

macerated fish remains (notably scales) and shotlike 

aggregates of pyrite and many beds of medium-bluishgray nonswelling bentonites in the basal part. (For 

photographs of these bentonites, see Spivey, 1940, pi. 

opposite p. 24.) After long exposure, the bentonites 

weather pale yellowish gray to yellowish orange, and 

the pyrite contained in the shale decomposes to form 

thin platelike masses of yellow jarosite and limonite. 

Well-formed transparent selenite crystals are common 

on some outcrops. The bentonite-rich basal beds contain Baculites obtusus, the middle part contains B. 

mcleami, and the upper part contains B. asperiformis. 

The Mitten Black Shale Member is softer than the 

underlying Sharon Springs Member, and its organic 

content is much less. Jarosite and selenite are not as 

common, and bentonite is scarce. The Mitten grades 

downward into the Sharon Springs, and the transition
A10 STUDIES OF THE PIERRE SHALE IN THE NORTHERN GREAT PLAINS

beds may contain one or more layers of tan phosphate 

nodules encrusted by white gypsum. B. asperiformis 

occurs in the basal beds and a smooth unnamed baculite, 

at a slightly higher level. The upper part of the Mitten 

contains iron-stained limestone concretions that have 

numerous B. per plexus. The lithology and fossil content of the Mitten suggest a correlation with the upper 

or bentonite-poor part of the Pembina Member, whereas 

the bentonite-rich Sharon Springs Member seems to 

correlate with similar beds in the lower part of the 

Pembina.

Along the Missouri River valley in south-central 

South Dakota, deposition was very slow and was interrupted somewhat during the time that the Sharon 

Springs and Mitten were forming in the Black Hills 

region. As a result, the equivalent strata along the 

Missouri River are very thin, and they are customarily 

treated as a single member of the Pierre Shale. Searight (1938, p. 137) assigned the Kansas name Sharon 

Springs to them, and this term has been used by all subsequent workers. The member consists of a lower part 

of dark-gray to brownish-gray resistant shale that contains abundant macerated fish remains and many thin 

layers of bentonite and a less organic-rich upper part 

that contains soft phosphatic nodules and possibly no 

more than two beds of bentonite. (For a photograph of 

the bentonite-rich part, see Gries and Rothrock, 1941, 

pi. opposite p. 8.) Colorless selenite and yellow jarosite 

are common. Most of the member can be easily correlated by its lithology with the Sharon Springs and 

Mitten of the Black Hills and with the Pembina Member 

of North Dakota.

The black organic-rich shale in the lower part of the 

Pembina Member is weakly radioactive, and these beds 

have easily identifiable electric and gamma-ray curves 

that provide a reliable stratigraphic datum throughout 

the subsurface of the central and western Dakotas and 

eastern Montana and Wyoming. The Pembina Member thickens westward from the Pembina Mountain 

area, and the equivalent strata in the subsurface in extreme western North Dakota reach a thickness of slightly 

less than 200 feet (Gill and Cobban, 1961, p. D188, 

D190, fig 352.3A}. Here, these strata are separated 

from the Niobrara Formation by 800 to 1,000 feet of 

shale (Gill and Cobban, 1961, p. D185, D190, fig. 

352.25). This shale, called the Gammon Ferruginous 

Member of the Pierre Shale in the Black Hills region 

(fig. 3), thins eastward across the Dakotas and has not 

been definitely identified in outcrops of eastern North 

Dakota. The eastward thinning of the Gammon is due 

to the increasing distance from the western source and 

to lateral gradation into and interfingering with the 

Niobrara Formation (Gill and Cobban, 1961, p. D185).

The thinning is accompanied by a change from a thick 

sequence of soft bentonitic claystone and shale containing abundant ironstone concretions and a few persistent 

beds of bentonite to a thin sequence of hard platy brownish-black shale containing thin persistent beds of bentonite. The basal foot or so of the Pembina Member 

at the Pembina River section may represent a part of 

the Gammon Ferruginous Member (fig. 5). The Gammon has not been formally recognized in central South 

Dakota but it may correlate with a thin sequence of 

beds at the base of the Sharon Springs Member in the 

Chamberlain, S. Dak., area.

GREGORY MEMBER

The Gregory Member of the Pierre Shale, as originally defined by Searight (1937, p. 10), included all the 

strata along the Missouri River in south-central South 

Dakota between the Niobrara Formation and the base 

of an ironstone-bearing siliceous shale unit that Searight had named the Sully Member. Searight's original Gregory Member was twofold, consisting of a lower 

part of "dark, bentonite bearing, bituminous shales 

which contain numerous fish scales," and an upper part 

of "a thin but characteristic zone of chalk, chalky shale, 

argillaceous chalk, or marl." Later Searight (1938, 

p. 137) restricted the name Gregory to the calcareous 

beds. Gries and Rothrock (1941, p. 11-14) further 

altered the scope of the Gregory Member by proposing 

the name Crow Creek for a thin chalky member at the 

top of the calcareous unit and restricting the Gregory 

to a partly calcareous shale that underlies the Crow 

Creek. This partly calcareous shale unit had been included in Searight's original Gregory Member but was 

assigned to the uppermost part of the Sharon Springs 

Member in his 1938 revision. Gries and Rothrock's interpretation of the Gregory has been accepted by all 

subsequent authors. The member is best exposed in the 

Chamberlain, S. Dak., area where Gries and Rothrock 

(1941, p. 12-13) determined thicknesses as great as 125 

feet and described the member as

light buff to dark gray when fresh, and from light brown to 

gray when weathered. Outcrops are typically banded with 

alternate beds of dark gray, noncalcareous shale containing 

brown ironstone concretions, and light-gray to buff calcareous 

layers. These calcareous layers range from slightly calcareous 

shale to impure chalk and limestone in composition, and from 

a few inches to several feet in thickness. * * * A conspicuous 

feature of all exposures of Gregory shale is an abundance of 

brown, fossiliferous concretions. These range from two to six 

or more inches in thickness, and may be small and intermittent, or may form nearly continuous ledges. Zones of large, 

one to two foot, gray limestone concretions are also present in 

some exposures.
STRATIGRAPHY, PIERRE SHALE, EASTERN NORTH DAKOTA All

L. G. Schultz (oral commun., 1964), who studied the 

Gregory Member in the Chamberlain area, found that 

this description applies only to the lower one-half or 

two-thirds of the member, and that the upper part of 

the member is lighter colored, bentonitic, and noncalcareous and lacks limestone concretions.

Fossils are common in the lower or calcareous part of 

the Gregory Member; they are pyritic in fresh roadcuts 

and streambanks, and dark brown and limonitic on 

weathered outcrops. Many of Meek and Hayden's types 

came from this part of the member. Baculites gregoryensis Cobban characterizes the lower part of the 

calcareous beds, and B. scotti Cobban marks the upper 

part (fig. 3). We collected B. gregoryensis as low as 

2 feet above the base of the member in the Chamberlain, 

S. Dak., area. Megafossils have not been found in the 

upper or bentonitic part of the Gregory in the Chamberlain area. This part must lie in the Eange Zone of 

B. scotti or in a younger range zone. The presence of 

bentonite suggests a range zone above that of B. scotti 

inasmuch as bentonite is absent in rocks of B. scotti age 

in the Black Hills area. Eocks lying in the next younger 

Eange Zone of Didymoceras nebrascense are very bentonitic in east-central Montana and partly bentonitic on 

the north flank of the Black Hills. The upper part of 

the Gregory Member probably lies in this range zone.

In eastern North Dakota a unit of light-colored calcareous strata overlying the dark noncalcareous Pembina Member is assigned herein to the Gregory Member. These calcareous rocks are most typical and 

best exposed in the valley of the Sheyenne Eiver at 

Valley City and southward for at least 20 miles. The 

rocks were originally described by Leonard (1904, p. 

152) as a light-gray calcareous clay shale 100 feet 

thick of which the upper part was cream colored and 

more calcareous than the lower part. Leonard 

noted that the calcareous rocks were overlain by 10 to 

20 feet of black clay shale which was more fissile. 

Later Leonard (1906, p. 69, 73) believed that this 

black shale was the same as the basal black shale member of the Pierre Shale in the Pembina Mountain area; 

and, accordingly, he assigned the underlying lightcolored calcareous strata at Valley City to the Niobrara Formation. This change in assignment was followed also by Babcock and Clapp (1906, p. 103, 106). 

At a much later date, Leonard (1919, p. 8) still assigned this calcareous unit to the Niobrara, and noted 

that it contained 45 percent of carbonate of lime at 

Valley City (erroneously reported as 75 percent in 

his 1904 paper, p. 152). Much later Kline (1942, p. 

355) correctly assigned this calcareous unit to the

Pierre Shale, and she stated that it "may be equivalent 

to the chalk in the upper Gregory of South Dakota."

We measured a complete section of the Gregory Member near Little Yellowstone Park (fig. 2J., loc. 5) 

where it is well exposed along North Dakota Highway 

46 in the Sheyenne Eiver valley about 20 miles south 

of Valley City in sec. 31, T. 137 N., E. 57 W. and sees. 

35 and 36, T. 137 N., E. 58 W. (See Little Yellowstone 

Park section, units 14-23.) Here the member is 108 

feet thick and divisible into a lower 53-foot unit of calcareous and noncalcareous shale containing yellowishbrown ironstone concretions and an upper 55-foot unit 

of marlstone. The lower or shale unit forms a banded 

outcrop owing to an alternation of darker weathering 

noncalcareous or slightly calcareous beds and lighter 

weathering more calcareous beds (fig. 7). The upper 

or marlstone unit is pale yellowish gray and grades 

down into the lower unit. The member rests with 

sharp contact on the underlying Pembina Member, and 

the contact is marked by local accumulations of a darkyellowish-orange to black mixture of gypsum, limonite, 

and manganese oxides.

Fossils are present, although not common, in the 

Gregory Member in the measured section. Unweathered ammonites are pyritic, whereas weathered ones 

are limonitic and dark brown. Baculites gilberti Cobban, which marks the middle of the Eange Zone 

of B. perplescus, was found 10 feet above the base; 

and undescribed scaphites suggestive of the Eange Zone 

of B. perplexus, were found as high as 32 feet above the 

base. B. gregoryensis, an index fossil for the next range 

zone in the western interior above that of B. perplexus, 

was collected 49 feet above the base, and juvenile baculites that may be this species were found as high as 67 

feet above the base. Some part or all of the rest of the 

upper marlstone unit probably lies in the Eange Zone 

of B. scotti judging from impressions of an undescribed 

species of the aberrant ammonite Didymoceras collected 

by members of the Department of Geology of the University of North Dakota from an outcrop of this marlstone at the north edge of North Valley City. This 

ammonite closely resembles specimens that have been 

found elsewhere in the western interior only with B. 

scotti.

H. A. Tourtelot collected samples from units 1, 2, 5, 

and 6 of the Gregory Member of the Pierre Shale near 

North Valley City. (See North Valley City section.) 

These and additional samples collected by L. G. Schultz 

from the Crow Creek and Gregory Members of the 

Pierre in central South Dakota were examined for
A12

FIGURE -7. Pierre Shale exposed in roadcut of North Dakota Highway 46 on the east side of the Sheyenne River in the SW%SW% sec. 31, 

T. 137 N., R. 57 W., Barnes County, X. Dak. Man is standing on a manganese-limonite bed that marks the contact between the Pembina 

Member (dark), and the Gregory Member (banded, light and dark). (See Little Yellowstone Park section.) Light (calcareous) and dark 

(less calcareous or noncalcareous) bands are typical of the lower part of the Gregory in both North and South Dakota.

Foraminifera by James F. Mello of the Geological Survey who reported the presence of the following fossils 

(written commun. to H. A. Tourtelot, Mar. 26, 1963) :

Sample To57-31-6 

[20 ft below top of Gregory Member, North Valley City]

Allomorphina conica Cushman and Todd

AmmodiscMS cretaceus (Reuss)

Anomalina henbesti Plummer

Planomalina (Globigerinelloides) messinae (Bronimonn)

Bolivina cf. B. incrassata Reusi^

Bolivinitella eleyi (Cushman)

Bolivinoides decorata (Jones)

Bolivinopsis rosula, (Ehrenberg)

Bulimina kickapooensis Cole

reussi Morrow navarroensis Cushman and Parker 

Cibicides cf. C. harperi (Sandidge) ? 

Dentalina niobrarensis Loetterle?

cf. D. legumen (Reuss)

gracilis d'Orbigny

consobrina d'Orbigny

Entosolenia orbignyana (Seguenza) 

Eouvigerina gracilis Cushman 

Globorotalites subconicus (Morrow) 

Gyroidina depressa (Alth)

globosa (Hagenow) of Cushman 

Haplophragmoides sp. 

He&bergella, loetterlei (Nauss) 

Heterohelix globulosa (Ehrenberg)

pulchra (Brotzen) 

Lowostoma plaitum (Carsey) ? 

Neobulimina canadensis Cushman and Wickenden 

Nodosarin cf. N. alternistriata Morrow 

Nuttallinellat n. sp. 

Oolina n. sp.

Pleurostomella, subnodosa Reuss 

Quadrimorphina allomorphinoides (Reuss) 

Ramulina globo-tubulosa Cushman 

Schackoina multispinata Cushman 

Stensioina americana, Cushman and Dorsey 

Stilostomella pseudoscripta (Cushman) 

Valvulineria infrequens Morrow
STRATIGRAPHY, PIERRE SHALE, EASTERN NORTH DAKOTA A13

Sample To57-31-5 

[40 ft below top of Gregory Member, North Valley City]

Allomorphina conica Cushman and Todd

Ammodiscus cretaceus (Reuss)

Planomalina (Globigerinelloides) messinae (Bronnimann)

Bolivinopsis rosula (Ehrenberg)

Bulimina kickapooensis Cole

reussi Morrow navarroensis Cushman and Parker 

Caucasina vitrea (Cushman and Parker) 

Dentalinacf.D. legumen (Reuss) 

Eouvigerina gracilis Cushman 

Globorotalites subconicus (Morrow) 

Gyroidina depressa (Alth)

globosa (Hagenow) of Cushman 

Haplophragmoides sp. 

Hedbergella loetterlei (Nauss) 

Heterohelixglobulosa (Ehrenberg)

pulchra (Brotzen) 

Neobulimina canadensis Cushman and Wickenden (typical form)

canadensis (newform) (?) 

Nodosaria fusula Reuss 

Nuttallinellal n. sp. 

Oolinan. sp. (?)

Osangularia navarroana ( Cushman) 

Pleurostomella subnodosa Reuss 

Pseudouvigerina cretacea Cushman 

Quadrimorphinaallomorphinoides (Reuss) 

Stilostomellapseudoscripta (Cushman)

Sample To57-31-2 

[100 ft below top of Gregory Member, North Valley City]

Ammodiscus cretaceus (Reuss)

Anomalinoides n. sp.

Planomalina (Globigerinelloides) messinae (Bronnimann)

Bolivinopsis rosula (Ehrenberg)

Bulimina kickapooensis Cole

reussi Morrow navarroensis Cushman and Parker 

Caucasina vitrea (Cushman and Parker) 

Dentalina cf. D. gracilis d'Orbigny 

Entosolenia cf. E. orbignyana ( Seguenza) 

Eouvigerina gracilis Cushman 

Globorotalites subconicus (Morrow) 

Glomospira charoides (Jones and Parker) 

Gyroidina depressa (Alth)

globosa (Hagenow) of Cushman 

Haplophragmoides sp. 

Hedbergella loetterlei (Nauss) 

Heterohelixglobulosa (Ehrenberg)

pulchra (Brotzen)

Neobulimina canadensis Cushman and Wickenden 

Nuttallinella'i n. sp.

Quadrimorphina allomorphinoides (Reuss) 

Stilostomella pseudoscripta (Cushman) 

Valvulineria infrequens Morrow

Sample To57-31-l 

[115 ft below top of Gregory Member, North Valley City]

Ammodiscus cretaceus (Reuss) (?)

Bathysiphon sp.

Planomalina (Globigerinelloides) messinae (Bronnimann)

Bulimina kickapooensis Cole.

Gaudryina cf. G. bentonensis (Carman)

Gyroidina depressa (Alth)

Haplophragmoides sp. 

Heterohelix globulosa (Ehrenberg) 

Stilostomella pseudoscripta (Cushman)

Mello's study of the Forminifera from the Gregory 

Member at Valley City was undertaken at a time when 

the stratigraphic position and age of these beds was 

uncertain. In his report he concluded:

To sum up, the Valley City samples are probably equivalent or 

very nearly so with the Gregory and Crow Creek samples. They 

are all of Tayloran age. The Mobridge in north-central South 

Dakota is of Navarroan age and differs subtly but significantly 

from the Valley City samples. The Valley City, Gregory, Crow 

Creek and calcareous Mobridge beds are similar in gross faunal 

aspect (excepting To57-31-l) and were probably deposited 

under similar conditions.

There are several exposures of the upper part of the 

Gregory in the immediate vicinity of Valley City. 

Leonard (1904, p. 152) described a small outcrop of 

Gregory along the Soo Kailroad about 1% miles east 

of Valley City and mentioned other exposures of the 

member along the Sheyenne River a mile south of Valley City. The Gregory Member of the Valley City 

area appears to be about the same thickness and composition as farther south along the Sheyenne River. H. A. 

Tourtelot supplied us with a section of the Gregory that 

he measured about half a mile north of North Valley 

City. (See North Valley City section.) The lower part 

of the member is poorly exposed and the position of the 

contact with the underlying Pembina Member could 

not be accurately determined.

The Gregory Member thins northward from Valley 

City and becomes less calcareous. It is only 24.5 feet 

thick in the measured section near the Tongue Kiver 

(Pembina Mountain section, unit 32), where the member consists of alternate bands of light-colored calcareous claystone and darker colored noncalcareous shale. 

Thin beds of brown-weathering ironstone are present, 

but fossils were not observed in them.

The member in these areas can be readily correlated 

with the Gregory Member of south-central South Dakota by its lithology and fossil content. The lower part 

of the member near Valley City is, however, a little older 

than the oldest beds in South Dakota. The general relations of the Gregory Member of South Dakota to the 

Red Bird Silty Member of the Pierre Shale in the 

Black Hills region and to the Judith River Formation of 

Montana have already been shown (Gill and Cobban, 

1961, fig. 352.4; 1962, fig. 8.1). The Gregory Member 

at Valley City seems to be the time equivalent of the 

Red Bird Silty Member. The base of both units lies 

well within the Range Zone of Baculites perplexus and 

the upper part of each unit lies in the Range Zone of 

B. scotti.
A14 STUDIES OF THE PIERRE SHALE IN THE NORTHERN GREAT PLAINS

In the Pembina Mountain area in southern Manitoba, 

the strata overlying the Pembina Member of the Vermilion Kiver Formation are called the Hiding Mountain 

Formation, which is divided into a lower soft member 

termed the Millwood Beds and an upper hard member 

known as the Odanah Beds (Tovell, 1948, p. 2; Halstead, 1959, p. 9; Davies and others, 1962, p. 145). The 

Millwood Beds in this area had earlier been called the 

Hiding Mountain Beds by Kirk (1930, p. 124B-126B), 

who described the unit as greenish-gray noncalcareous 

shale that slumped easily and weathered readily to mudcracked surfaces bare of vegetation. Kirk noted further that nodules and irregular bands of dark-brown 

ironstone were abundant. He did not determine the 

thickness near the international boundary, but MacLean (1916, p. 131), who applied the name Millwood 

(Tyrrell, 1890, p. 230) to these beds, gave a thickness 

of 80 feet. Tovell (1948, p. 5) stated that the thickness 

in this area ranges "from 15 feet( ?) on the west to 65 

feet or more in the eastern sections, but no direct measurements were possible."

We briefly examined the Millwood near Miami, Manitoba, in the Pembina Mountain area as well as in the 

type area around Millwood and Harrowby some 170 

miles farther northwest. Near Miami the lowest part 

of the Millwood is slightly calcareous; and, although 

no fossils were noted, it seems reasonable to correlate it 

with the Gregory Member. Fossils found in the lower 

part of the Millwood in the Millwood-Harrowby area 

include Baculites scotti, B. gregoryensis, and scaphites 

suggestive of the B. perpleseus Range Zone. A correlation of this part of the Millwood with the Gregory 

Member in North Dakota is unquestioned.

DeGBEY MEMBER

Crandell (1950, p. 2341) proposed the name DeGrey 

Member for a gray noncalcareous bentonite-bearing unit 

of the Pierre Shale that contains numerous iron-manganese carbonate concretions. The member was named for 

a locality near the Missouri River in south-central South 

Dakota, where the unit is about 82 feet thick and rests 

conformably on the marly Crow Creek Member. Several of the beds of bentonite contain flakes of biotite, 

and two of these have proved very useful for correlation along the Missouri River (Gries, 1940, p. 18-27; 

1942, p. 21; Gries and Rothrock, 1941, p. 22-26). A 

striking feature of the member is the great abundance 

of black-weathering iron-manganese carbonate concretions which darken the outcrops. Fragments of pelecypods and ammonites are common in these concretions. 

Bits of baculites indicate a large compressed species that 

has a well-ribbed venter and a complex suture pattern; 

these features suggest either Baculites rugosus Cobban 

or a closely related ventral-ribbed species which mark

the Range Zones of Exiteloceras jenneyi (Whitfield) 

and Didynw-ceras cheyennense (Meek and Hay den) respectively (fig. 3).

Dark-colored rocks of DeGrey lithology are typical 

and well exposed along the Sheyenne River valley in 

North Dakota where they rest upon light-colored calcareous rocks as they do in South Dakota. The name 

DeGrey is herein applied to these rocks in North 

Dakota.

The unit was first described by Leonard (1904, p. 

152) at Valley City as 10 to 20 feet of "Black clay shale, 

with yellow iron stains in spots and blotches. Upon 

exposure to the weather it crumbles into thin flakes." 

Later Leonard (1906, p. 73) and Babcock and Clapp 

(1906, p. 103, 106) believed that this dark unit was the 

same as the "banded black and white shale" (Pembina Member) at the base of the Pierre Shale in the 

Pembina Mountain area.

We did not measure a complete section through the 

DeGrey Member in the Sheyenne River valley, but the 

thickness there is at least 40 feet. The member consists of dark flaky bentonitic shale weathering to a dark 

gumbo bare of vegetation. Black-weathering concretions of iron-manganese carbonate are abundant, and 

these contain fragments of fossils as they do in South 

Dakota. A collection made from these concretions 25 

to 40 feet above the base of the member 9 miles south 

of Valley City in the SW^SE^ sec. 4, T. 138 N., R. 

58 W. contained Inoceranws cf. / nebrascensis Owen, 

Inoceramus aff. /. mcleami Douglas, Pteria n. sp., Ostrea 

cf. O. plwnosa Morton, Ostrea sp., Anomm cf. A. 

argentaria Morton, Pholadom/ya hodgei (Meek), and 

Baculites sp. All of these species occur in the black 

iron-manganese carbonate concretions in the DeGrey 

Member at Chamberlain, S. Dak. The few fossils recorded by Upham (1895, p. 92) 8 miles south of Valley 

City probably came from the DeGrey Member.

The member thins northward and becomes lighter 

in color. Near the Tongue River it consists of 

about 30 feet of gray to olive-gray shale and claystone 

that weathers light gray and contains ironstone concretions weathering reddish brown, dark brown, or 

black. A conspicuous feature is the presence, at the 

top of the member, of a layer of partly swelling bentonite containing black flakes of biotite. Fossils are 

scarce, and only bits of Inoceramus were noted. The 

member seems to rest conformably on the calcareous 

Gregory Member and is conformably overlain by siliceous shale herein assigned to the Odanah Member.

Barry and Melsted (1908, p. 180) measured a 280- 

foot section of the Pierre Shale along the South 

Branch of the Park River in northern Walsh County, 

N. Dak. We interpret unit 1 of their section as representing the upper 30 feet of the DeGrey, and the over-
STRATIGRAPHY, PIERRE SHALE, EASTERN NORTH DAKOTA A15

lying 150 feet of hard shale (their unit 2) as representing the Odanah Member.

The DeGrey Member in the Valley City area is the 

lithologic continuation of the DeGrey Member of South 

Dakota. Along the Tongue River the member has 

changed to a lithology more like that of the upper part 

of the Mill wood Beds in the adjoining part of Manitoba. However, inasmuch as the member along the 

Tongue River overlies the Gregory Member and still has 

some DeGrey features such as bentonitic beds and black 

ironstones, it seems best to apply the name DeGrey as 

far north as the international boundary rather than 

use some other term such as upper part of Millwood 

Beds or to introduce a new name. In the MillwoodHarrowby area of Manitoba, the uppermost part of the 

Millwood Beds is darker and more bentonitic and 

gumbo forming than the underlying part. Diagnostic 

fossils were not found by us in this part, bijt the presence of baculites of late Gregory age (Range Zone of 

Baculites scotti} lower in the Millwood suggests that 

the upper part of the member could well be of DeGrey 

age.

The DeGrey Member in North Dakota probably correlates with both the DeGrey and Crow Creek Members 

in the Missouri River valley of South Dakota. The 

Crow Creek conformably underlies the DeGrey, whereas it apparently disconformably overlies the Gregory 

Member (Crandell, 1952). The only fossils known 

from the upper part of the Gregory Member in both 

North and South Dakota lie in the Range Zone of 

Baculites scotti. This similar dating of the upper part 

of the Gregory in both areas and the apparent hiatus 

separating the Crow Creek from the Gregory make it 

more logical to assume that the lower part of the DeGrey Member in North Dakota is the time equivalent of 

the Crow Creek.

The presence of Baculites scotti in the uppermost 

part of the Red Bird Silty Member of the Pierre Shale 

in the Black Hills area shows that the DeGrey Member 

is the time equivalent of a part of the overlying unnamed shale member which contains baculites having 

corrugated venters suggestive of the fragments in the 

DeGrey Member at Chamberlain, S. Dak. Similar baculites are present in the lower part of the Bearpaw 

Shale south of the Bearpaw Mountains in central Montana. Accordingly, the DeGrey Member is correlated 

with the lower part of the Bearpaw Shale and with the 

lower part of the unnamed shale unit that overlies the 

Red Bird Silty Member of the Pierre Shale (fig. 3).

Beds equivalent to the DeGrey have wide distribution 

in southwestern Manitoba. Near the SaskatchewanManitoba line, some 250 miles north of the international 

boundary, bentonitic claystone and shale containing

abundant iron-manganese nodules, were described by 

Dawson (1942, p. 10-11) as follows:

iThe nodular deposits [iron-manganese] of Porcupine Mountain 

area have an interesting similarity in stratigraphical position, 

lithology and manganese content to those of the lower Missouri 

Valley in South Dakota. In the latter area manganiferous nodules occur in the Oacoma zone of the Sully shale member [DeGrey Member] which is a subdivision of the South Dakota 

Pierre. The Pierre in Manitoba includes the upper part of the 

Vermilion River formation, the Riding Mountain [Millwood] 

formation and the Odanah formation. The stratigraphical position of the known manganiferous horizon or horizons in the 

Riding Mountain [Millwood] formation is, further, similar to 

the position of the Oacoma zone in the Pierre of South Dakota.

ODANAH MEMBER

Tyrrell (1890, p. 230) gave the name Odanah Series 

to "a great thickness of light gray rather hard clay 

shales which are locally known as slate." The Odanah 

overlies the softer dark-gray clay shale unit which 

Tyrrell had named the Millwood Series. The name 

Odanah was taken from a locality near Minnedosa, 

Manitoba, about 85 miles north of the North Dakota 

boundary. MacLean (1916, p. 131) applied the name 

Odanah to the hard light-colored shale above the soft 

Millwood Beds in the Pembina Mountain area. Wickenden (1945, p. 48) believed the Odanah to be only a 

poorly defined hard facies of the Riding Mountain 

Formation, but Tovell (1948, p. 6), Halstead (1959, p. 

9-10), and Da vies and others (1962, p. 145) treated 

the Odanah as a distinct member.

The Odanah, along the Pembina River a few miles 

north of the North Dakota boundary, was described by 

Tovell (1948) as chiefly hard gray siliceous shale that 

has a greenish cast and contains some thin beds of 

bentonite, of which a layer 0.8 foot thick near the base 

is a persistent marker bed. Some softer bentonitic 

shale is interbedded with the hard siliceous shale. 

Tovell noted further that the shale showed purple 

staining as well as limonitic staining and that irregularly distributed purple-stained concretions were 

common.

In the Pembina Mountain area of North Dakota, the 

soft DeGrey Member is overlain conformably by hard 

light-gray siliceous shale that contains ferruginous concretions. This hard shale is obviously the southward 

continuation of the Odanah Beds, and the name Odanah 

is herein used as a member of the Pierre Shale. Outcrops of this member in the Pembina Mountain area 

have been described by Upham (1895, p. 93-96) and 

Barry and Melsted (1908, p. 180-183), who observed the 

slatelike character of the shale, the iron-stained joint 

surfaces, and the abundance of ferruginous concretions. 

Barry and Melsted also recorded a persistent 1-foot layer 

of yellow clay [bentonite] in the lower part of the member. This bed may be the same as the widespread 0.8-
A16 STUDIES OF THE PIERRE SHALE IN THE NORTHERN GREAT PLAINS

foot bentonite noted by Tovell (1948, p. 6) farther 

north.

The thickness of the Odanah Member in the Pembina 

Mountain area of North Dakota is largely unknown. 

The lower 65 feet can be seen along North Dakota 

Highway 5 near the Tongue Kiver. (See Pembina 

Mountain section, unit 36.) Barry and Melsted (1908, 

p. 180) measured 150 feet of hard shale along the South 

Branch of the Park River in northern Walsh County 

which we interpret as representing the Odanah Member 

in this area. Farther north, about 200 feet of the member is present in the Manitoba part of Pembina Mountain (Tovell, 1948, p. 6). Outcrops of the member in 

North Dakota outside the Pembina Mountain area are 

scarce, and the thickness of beds exposed at most places 

is small. One of the largest outcrops, in the Devils Lake 

area (fig. 1), shows only 20 feet of beds (Laird, 1957, 

pi. 1). A cursory examination of logs of oil and gas 

test wells in northern North Dakota suggests that the 

Odanah may reach a thickness of about 200 feet in 

eastern Rolette County, from where it appears to thin 

abruptly to the west.

Fossils in the Odanah are scarce, and little is known 

concerning the time range of the member. Wickenden 

(1945, p. 49-50) mentioned the occurrence of numerous 

radiolarians, and listed the foraminifers Glomospira 

charoides (Jones and Park) var. corona Cushman and 

Jarvis, Ammodiscus cretacea (d'Orbigny), .Bigenerina 

-hastata Cushman, and Silicosigmoilina califomica 

Cushman and Church; the pelecypods Oooytoma nebrascana Evans and Shumard and Ostrea sp.; the cephalopods Scaphites (Discoscaphitesl) sp. and Bacuities 

compressus Say; and the calcareous worm tube Serpula 

sp. Three species of pelecypods Leda hindi, Inoceramus canadensis, and Anomia ftemingi described by 

Meek (1860, p. 196, pi. 1, figs. 2-5, 8-9) from southern 

Manitoba probably came from low in the Odanah. The 

only fossils we observed in North Dakota were bits of 

Inoceranws. TJpham (1895, p. 94) recorded /. sagensis 

Owen, Baculites ovatus Say, /Scaphites nodosus Owen, 

and fish teeth from the Pembina Mountain area. The 

presence of radiolarians, presumably from this part of 

the Pierre Shale, was mentioned by Holland (1961, 

p.59).

Part of the Odanah grades southward into the Virgin 

Creek Member of the Pierre Shale of South Dakota 

("lower Virgin Creek" of Searight, 1937, p. 36). In 

south-central South Dakota the Virgin Creek is a soft 

medium-gray flaky shale that contains several thin 

layers of bentonite. Farther north the member becomes 

harder and lighter colored; and at its type locality 18 

miles southwest of Mobridge, part of the member, as 

described by Searight (1937, p. 39), is "light gray, 

erodes first to buttresses with red to rusty brown coating. Later breaks down to gentle shopes. Where recently undercut breaks into flattish pieces which produce dull slaty 'clink' when struck. Later breaks down 

to flakes which have a faint purplish cast which produces a sub-metallic sheen. Contains 11 thin bentonite beds * * *" Rothrock (1947, p. 12) also noted the 

northward change of the Virgin Creek from nonsiliceous to siliceous shale. The Virgin Creek is separated 

from the DeGrey Member by the Verendrye Member, 

a gray shale that weathers to bands of brown and gray 

gumbo and contains numerous flattish brown-weathering ironstone concretions. Both the Verendrye and the 

lower part of the Virgin Creek Members are probably 

equivalent to the Odanah (fig. 3). The Virgin Creek 

contains Baculites eliasi Cobban. The Verendrye may 

include more zones although the best fossils found so 

far are poorly preserved fragments of baculites suggesting B. cuneatus Cobban.

The upper part of the Virgin Creek is a bentonitic 

shale unit that readily forms a bare gumbo. This unit 

was called "upper Virgin Creek" by Searight (1937, 

p. 37), but later Rothrock (1947, p. 11) assigned most or 

all of it to the overlying calcareous Mobridge Member. 

Rothrock's assignment of Searight's "upper Virgin 

Creek" to the Mobridge has not gained wide acceptance, 

and most recent workers have followed Searight's original treatment.

The Kara Bentonitic Member and the uppermost part 

of the underlying unnamed shale member of the Pierre 

Shale in the southwestern Black Hills region contain 

Baculites eliasi Cobban and correlate with the lower 

part of the Virgin Creek Member. This ammonite is 

also found high in the Bearpaw Shale of central Montana. By inference, the upper part of the Odanah may 

correlate with this part of the Pierre and Bearpaw 

Shales, whereas the rest of the Odanah may correlate 

with the middle part of the Bearpaw and most of the 

upper half of the unnamed shale member of the Pierre 

underlying the Kara Bentonitic Member.

The upper part of the Pierre Shale has been largely 

removed from eastern North Dakota by pre-Pleistocene 

erosion, and outcrops of Cretaceous rocks younger than 

the Odanah Member were not seen by us. Barry and 

Melsted (1908, p. 180) reported that on the South 

Branch of the Park River in northern Walsh County 

10 to 100 feet of dark fissile shale that weathers to a 

black sticky clay overlies beds which we interpret as 

Odanah. These shales may be equivalent to the upper 

part of the Virgin Creek Member of the Pierre Shale.

The original thickness of the Pierre in eastern North 

Dakota is unknown, but an extrapolation of rates of 

eastward thinning of the Pierre in the central and 

western parts of the State suggests that between 500 

and 600 feet of beds may have been deposited. The
STRATIGRAPHY, PIERRE SHALE, EASTERN NORTH DAKOTA A17

thickness and distribution of the marine Cannonball 

Member of the Fort Union Formation of Paleocene age 

in North Dakota and adjacent areas might be interpreted to mean that in the extreme eastern part of the 

State slow but continuous marine deposition lasted until 

early Paleocene time.

REFERENCE SECTIONS

Reference sections of parts of the Pierre Shale were 

measured in eastern North Dakota. The purpose of 

these sections is to supplement previously published 

sections mentioned in the text and to provide a framework for additional stratigraphic studies of the Pierre 

Shale in eastern North Dakota.

Little Yellowstone Park section

[Measured in readouts along North Dakota Highway 46 near Little 

Yellowstone Park about 20 miles south of Valley City. Lower part 

measured in the SW%SW% sec. 31, T. 137 N., R. 57 W., and the 

upper part measured in the SW%SW% sec. 36 and SE%SE% sec. 35, 

T. 137 N., R. 58 W., Barnes County (fig. 2A, loc. 5)]

Pierre Shale (lower part) :

DeGrey Member (part) : Feet

23. Shale, black, noncalcareous, flaky________ 8.0 

Gregory Member:

22. Marlstone, pale-yellowish-gray; very clayey and 

soft at base and top; moderately hard in middle ; weathers to a grayish-yellow slope. A few 

pyritic juvenile baculites collected 13 ft above 

base; USGS Mesozoic loc. D4098, Baculites cf. 

B. gregoryensis Cobban ______________ 55. 0

21. Shale, dark-gray, slightly calcareous, flaky; interbedded with a subordinate amount of lighter 

colored calcareous claystone which imparts a 

banded appearance to the weathered outcrop. 

Unit contains thin beds of shaly reddish-brownweathering ironstone. Unit becomes increasingly calcareous upward and grades into the 

the overlying marlstone. A few small pyritic 

baculites collected in middle of unit; USGS 

Mesozoic loc. D4098, Baculites cf. B. gregoryensis Cobban___________________ 7. 0

20. Shale, dark-gray; slightly calcareous becoming 

more calcareous and lighter gray in upper part. 

A few fossils collected at 10 and 13 ft above 

base; USGS Mesozoic loc. D4097, Trachytriton vinculum (Hall & Meek), Baculites gregoryensis Cobban, Didymoceras sp_______ 13. 8

19. Claystone, pale yellowish-brown, very calcareous; 

weathers to a yellowish-gray soft slope; contains thin beds of yellowish-brown-weathering 

shaly ironstone. A few fossils collected 3.5 ft 

above base; USGS Mesozoic loc. D4096, Baculites sp., Hoploscaphites n. sp_________ 4. 0

18. Shale, olive-gray, noncalcareous to slightly calcareous, flaky; forms a dark slope; contains 

thin ironstone beds. A 0.6-ft calcareous claystone bed 3 ft above base contains a few fossils; 

USGS Mesozoic loc. D4095, Inoceramus sp., 

Baculites sp_____________________ 7.0

Little Yellowstone Park section Continued

Pierre Shale (lower part) Continued 

Gregory Member Continued

17. Claystone; weathers light yellowish gray; very 

calcareous. Contains a few fossils; USGS 

Mesozoic loc. D4005, Inoceramus sp., Baculites sp______ 1.7

16. Bentonite, orange, deeply weathered; contains

abundant limonite and gypsum . 3

15. Shale; in medium-light-gray calcareous units alternating with medium-dark-gray noncalcareous units; weathers to small soft flakes; contains layers of yellowish-brown ironstone and a 

few tan phosphate pebbles. Basal 1.5 ft is 

light-gray very calcareous shale. A few fossils collected at 1 ft and 4.5 ft above base; 

USGS Mesozoic loc. D4094, Inoceramus sp., 

Baculites cf. B. gilberti Cobban, Hoploscaphites 

n. sp___________ _ 8. 8

14. Shale; in medium-light-gray noncalcareous flaky 

units alternating with medium-dark-gray slightly bentonitic units; contains thin beds of rustyweathering shaly ironstones and scattered small 

pyrite nodules. A few fossils collected 10 ft 

above base; USGS Mesozoic loc. D4093, calcareous worm tubes, Baculites gilberti 

Cobban _____ 11.0

Total Gregory Member 108.6

Pembina Member:

13. Nonpersistent layer of a mixture of gypsum, limonite, and manganese oxides ±0.3 

12. Shale, grayish-brown to brownish-black; weathers 

to light-olive-gray thin flakes; contains a few 

scattered gypsum-encrusted phosphate nodules 

in upper 3 ft. Unit is slightly harder than 

underlying beds 11.2 

11. Bentonite, very pale orange, nonswelling; contains numerous weathered pyrite nodules . 3 

10. Shale, similar to unit 12 but containing abundant 

streaks of yellowish-orange jarosite; contains 

a thin layer of limonitic bentonite 8 ft above 

base. Unit contains persistent beds of gypsumencrusted phosphate nodules at 2.6, 3.4, and 

4.6 ft above base, and 4 layers of phosphate 

nodules in upper 5 ft 14. 8 

9. Ironstone, dark-yellowish-orange, slabby . 4 

8. Shale, similar to unit 10; contains gypsum-encrusted phosphate nodules, large gypsum-encrusted bones, and gypiferous limonitic baculites at 8 ft and 13 ft above base. One pyritic 

baculite collected 14 ft above base; USGS Mesozoic loc. D4092, Baculites perplexus Cobban__ 17. 0 

7. Bentonite, very pale orange, nonswelling 0.1 

6. Shale, similar to unit 10______ .2 

5. Bentonite, similar to unit 7 . 2

Total Pembina Member __ 44. 6

Total Pierre Shale measured 161.2
A18 STUDIES OF THE PIERRE SHALE IN THE NORTHERN GREAT PLAINS

Little Yellowstone Park section Continued

Niobrara Formation (uppermost part) : Feet 

4. Shale, medium yellowish-brown, calcareous; cemented with gypsum and jarosite_________ 0. 8 

* 3. Chalk, very pale orange, hard____________ . 5 

2. Covered interval; probably soft chalk______ 5.5 

1. Chalk, dark-yellowish-orange to pale-yellowishorange__ _____________________ 5.0

Total Niobrara Formation measured_____ 11. 8 

North Valley City section

[Measured in 1957 by H. A. Tourtelot in roadcut half a mile north of 

North Valley City, just north of road to east, and along this road to 

the east in the NE% sec. 9, T. 140 N., R. 58 W., Barnes County (fig. 

2A, loc. 4) ]

Pierre Shale (lower part) : 

DeGrey Member (part) : Feet

7. Shale, dark-gray, soft, highly bentonitic; has a 

flaky fracture; weathers to a black 0.5-ft thick 

gumbo that contains abundant selenite. Blackweathering concretions of iron-manganese carbonate containing fragments of Inoceramus 

are moderately abundant. Unit is at least 50 

ft in total thickness (estimated from outcrops 

across valley to south)______________ 15 

Gregory Member (part) :

6. Chalk and clayey chalk, gray; forms steep slope

in roadcut; weathers tan to creamy yellow 35

5. Shale, gray, marly, bentonitic, soft; weathers

bluish gray_____________________ 15

4. Chalk and marly chalk; gray; weathers tan;

much ferruginous debris on surface______ 10

3. Covered interval____________________ 40

2. Marly chalk; grayish-buff; ferruginous debris 

scattered on surface; joint planes stained with 

manganese oxide__________________ 10

1. Shale, dark-gray, calcareous, bentonitic, soft; 

flaky fracture; weathers to a 0.5-ft thick grayish-brown gumbo that contains much ferruginous debris; iron oxides and scattered minute 

selenite crystals coat joint planes. Base not 

exposed _______________________ 20

Total Gregory Member exposed__________ 130

Total Pierre Shale measured____________ 145

Pembina Mountain section

[Beds 1-27 measured by H. A. Tourtelot on the Olson Farm in the NE% 

sec. 25, T. 1,61 N., R. 57 W. (fig. 2B, loc. 3a) ; beds 28-36 measured 

by J. R. Gill at the spillway cut for the Tongue River retention dam 

T-3-5 in the SE^NE^ sec. 24, and along North Dakota Highway 5 

in the NW%NE% sec. 24, T. 161 N., R. 57 W., Cavalier County 

(fig. 2fi, loc. 3b)J

Pierre Shale (lower part) :

Odanah Member (part) : peet 

36. Shale, medium-light-gray to light-gray, siliceous, 

hard; weathers to thin angular chips; contains 

a few thin ironstone concretions in lower part. 

Thickness determined by altimeter_______ 65. 0

Pembina Mountain section Continued

Pierre Shale (lower port) Continued

DeGrey Member: Feet

35. Bentonite, light-olive-gray; slightly swelling; contains numerous black euhedral crystals of biotite in lower 0.1 ft________ .5

34. Shale, olive-gray; weathers light gray; lower 5 

ft soft, but rest of unit hard and tends to form 

ridges. Unit contains several thin layers of 

reddish-brown-weathering ironstones. Fragments of Inoceramus common 15 ft above base 23.0

33. Claystone, gray, noncalcareous, bentonitic; weathers to light-gray gumbo barren of vegetation; 

contains a few small dark-brown to black ironstone concretions that weather into small angular fragments 6.0

Total DeGrey Member_____ 29.5

Gregory Member:

32. Claystone and shale; interbedded to form a light 

and dark banded outcrop. Dark layers consist 

of olive-gray noncalcareous shale that weathers 

to a lighter flaky crust. Light layers consist of 

light-olive-gray calcareous bentonitic Claystone 

that weathers to pale-yellowish-brown gumbo. 

A 2-f MMck yellowish-gray-weathering very calcareous Claystone bed 13 ft above base and a 0.2- 

ft-thick cream-colored slightly swelling bed of 

bentonite 2 ft above base. Unit contains numerous thin beds of light-brown-weathering 

ironstone ______ _ 24. 5

Pembina Member:

31. Shale, dark-gray; weathers to light-olive-gray 

thin plates; fish scales and jarosite seams less 

abundant than in underlying unit. Numerous 

gypsum-encrusted phosphate nodules in upper 

15 ft, and tan phosphate nodules in upper 2 

ft. Very thin layers of dark-yellowish-brown 

limonite and jarosite impregnated bentonite at 

7, 27, 30.3, and 32 ft above base________ 34.0 

30. Bentonite, pale-yellowish-gray, nonswelling_ . 25 

29. Shale, dark-brownish-black; weathers to olivegray thin plates; contains abundant fish scales, 

seams of jarosite, and plates of selenite; becomes harder and more organic rich in lower 

part. A 0.05-ft-thick layer of bentonite 29 ft 

above base___________________ 32. 8

28. Bentonite, yellowish-orange, nonswelling, granular __________________________- .3

27. Shale, black; weathers to light-gray flakes 5 mm

or more in diameter; organic rich . 8 

26. Bentonite, similar to unit 24____________ .02

25. Shale, similar to unit 27____ _ . 4 

24. Bentonite, creamy-tan, nonswelling, granular; irregular conchoidal fracture; tastes acidic. .4 

23. Shale, similar to unit 27____________ .2 

22. Bentonite, similar to unit 24_____________ . 4 

21. Shale, similar to unit 27______________ .1 

20. Bentonite, similar to unit 24____________ . 2

19. Shale, similar to unit 27_______________ . 1
STRATIGRAPHY, PIERRE SHALE, EASTERN NORTH DAKOTA A19

Pembina Mountain section, Continued

Pierre Shale (lower part) Continued

Pembina Member (part) Continued Feet 

18. Bentonite, similar to unit 24____________ 0.3 

17. Shale, similar to unit 27_______________ . 3 

16. Bentonite, similar to unit 24____________ . 2

15. Shale, similar to unit 27_______________ . 1

14. Bentonite, similar to unit 24; contains irregular

tubelike masses of gray shale 1 mm in diameter

and as much as 20 mm in length in upper 0.1

ft ____________________________ .4

13. Shale, similar to unit 27_______________ . 5

12. Bentonite, similar to unit 24_____________ . 2

11. Shale, similar to unit 27___________-___ . 1

10. Bentonite, similar to unit 24_____________ . 5

9. Shale, similar to unit 27_______________ . 3

8. Bentonite, similar to unit 24____________ . 2

7. Shale, similar to unit 27_______________ . 2

6. Bentonite, similar to unit 24____________ . 1

5. Shale, similar to unit 27_______________ . 3

4. Bentonite, similar to unit 24 but has grayish

cast __________________________ .05 

3. Shale, similar to unit 27 but contains noticeable

pyrite ______ ____ __ . 5

2. Bentonite, similar to unit 24 but has irregular

fracture coating of yellow highly plastic clay_ . 3 

1. Shale, similar to unit 27_______________ . 1

Total Pembina Member (rounded)_______ 75.0

Total Pierre Shale measured ________194.0

Iron oxide in irregular crust; appears to have been 

formed on present outcrop cementing basal shale of 

Pierre and uppermost chalky marl of the underlying 

Niobrara Formation into a heterogeneous ledge___ . 5 

Niobrara Formation:

Chalky marl and chalk. Forms cliff. Not measured.

Pembina River section

[Partial section of the Pembina Member of the Pierre Shale measured 

by J. R. Gill and W. A. Cobban In a roadcut west of the Pembina 

River in the SW% sec. 30, T. 163 N., R. 57 W., Cavalier County 

(fig. 2B, loc. 2)]

Pierre Shale (part) :

Pembina Member (part) : Feet 

35. Shale, dark-brownish-black; hard, forming a buttress ; contains abundant fish scales and numerous streaks of yellowish-orange-weathering 

jarosite ________________________ 3.0 

34. Bentonite, pale-yellowish-orange, nonswelling;

sharp upper and lower contacts_________ . 5 

33. Shale, similar to unit 35_______________ . 15 

32. Bentonite, similar to unit 34____________ . 4 

31. Shale, similar to unit 35_______________ . 15 

30. Bentonite, similar to unit 34____________ .30 

29. Shale, similar to unit 35_______________ .25 

28. Bentonite, similar to unit 34____________ .45 

27. Shale, similar to unit 35_______________ .45 

26. Bentonite, similar to unit 34____________ .20 

25. Shale, similar to unit 35_______________ . 15 

24. Bentonite, similar to unit 34____________ . 50 

23. Shale, similar to unit 35_______________ .50 

22. Bentonite, similar to unit 34_____________ . 10

Pembina River section Continued

Pierre Shale (part) Continued

Pembina Member (part) Continued Feet 

21. Shale, similar to unit 35___ _ _ . 15 

20. Bentonite, similar to unit 34____ .45 

19. Shale, similar to unit 35_______________ 1.50

18. Bentonite, similar to unit 34__ 

17. Shale, similar to unit 35 

16. Bentonite, similar to unit 34_ 

15. Shale, similar to unit 35_ 

14. Bentonite, similar to unit 34_ 

13. Shale, similar to unit 35_ 

12. Bentonite, similar to unit 34. 

11. Shale, similar to unit 35_____

10. Bentonite, similar to unit 34_ 

9. Shale, similar to unit 35_____

8. Bentonite, similar to unit 34_ 

7. Shale, similar to unit 35_____

6. Bentonite, similar to unit 34. 

5. Shale, similar to unit 35______

4. Bentonite, similar to unit 34_ 

3. Shale, similar to unit 35___

________ .25

________ . 05

________ .05

________ . 10

________ . 05

________ . 05

________ . 05

________ . 10

________ . 10

________ . 15

________ .10

________ . 15

________ . 10

________ . 10

________ . 15

________ .40

2. Limonite and gypsum, rusty-brown, hard 1.40

Total Pierre Shale measured (rounded) 12.60

Niobrara Formation (uppermost bed) : 

1. Marlstone, yellowish-orange___

LITERATURE CITED

Babcock, E. J., and Clapp, C. H., 1906, Economic geology of 

North Dakota clays: North Dakota Geol. Survey 4th Bienn. 

Rept, p. 95-189, pis. 6-13.

Bannatyne, B. B., 1963, Cretaceous bentonite deposits of Manitoba : Manitoba Dept. Mines and Nat. Resources, Mines 

Br. Pub. 62-5,44 p.

Barry, J. G., and Melsted, V. J., 1908, The geology of northeastern North Dakota with special reference to cement materials: North Dakota Geol. Survey 5th Bienn. Rept., p. 

115-211, pis. 20-29.

Connolly, J. P., and O'Harra, C. C., 1929, The mineral wealth 

of the Black Hills: South Dakota School Mines Bull. 16, 

418 p.

Crandell, D. R., 1950, Revision of the Pierre shale of central 

South Dakota: Am. Assoc. Petroleum Geologists Bull., 

v. 34, no. 12, p. 2337-2346.

 1952, Origin of Crow Creek member of Pierre shale in 

central South Dakota: Am. Assoc. Petroleum Geologists 

Bull., v. 36, no. 9, p. 1754-1765.

Davies, J. F., Bannatyne, B. B., Barry, G. S., and McCabe, H. R., 

1962, Geology and mineral resources of Manitoba: Manitoba Dept. Mines and Nat. Resources, Mines Br., 190 p., 

20 pis.

Dawson, A. C., 1942, Manganese occurrences in Manitoba: Manitoba Dept. Mines and Nat. Resources, Mines Br. Prelim. 

Geol. Rept. 42-1, 23 p.

Dawson, G. M., 1881, On the lignite Tertiary formation, from 

the Souris River to the 108th meridian: Canada Geol. 

Survey Rept. Prog. 1879-80, p. 12A-49A.

Elias, M. K., 1931, The geology of Wallace County, Kansas: 

Kansas Geol. Survey Bull. 18, 254 p., 42 pis.

Gallay, Wilfred, 1938, Canadian bentonites: Canadian Jour. 

Research, v. 16, p. 6-34.
A20 STUDIES OF THE PIERRE SHALE IN THE NORTHERN GREAT PLAINS

Gill, J .B., and Cobban, W. A., 1961, Stratigraphy of lower and 

middle parts of the Pierre Shale, northern Great Plains, in 

Short papers in the geologic and hydrologic sciences: U.S. 

Geol. Survey Prof. Paper 424-D, p. D185-D191.

 1962, Red Bird Silty Member of the Pierre Shale, a new 

stratigraphic unit, in Short papers in geology, hydrology, 

and topography: U.S. Geol. Survey Prof. Paper 450-B, p. 

B21-B24.

Gries, J. P., 1940, A structural survey of northeastern Stanley 

County, South Dakota: South Dakota Geol. Survey Kept. 

Inv. 34, 52 p., 5 pis.

 1942, Economic possibilities of the Pierre shale: South 

Dakota Geol. Survey Kept. Inv. 43, 79 p., 1 pi.

Gries, J. P., and Rothrock, B. P., 1941, Manganese deposits of 

the lower Missouri valley in South Dakota: South Dakota 

Geol. Survey Kept. Inv. 38, 96 p., 9 pis.

Halstead, B. C., 1959, Ground-water resources of the Brandon 

map-area, Manitoba: Canada Geol. Survey Mem. 300, 67 p., 

2 maps.

Holland, F. D., Jr., 1961, The status of paleontology in North 

Dakota : North Dakota Acad. Sci. Proc., v. 15, p. 45-63.

Kirk, S. R., 1930, Cretaceous stratigraphy of the Manitoba 

escarpment: Canada Geol. Survey Summ. Kept., 1929, pt. B, 

p. 112B-135B.

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