Geochemical Investigations 

of Some Black Shales 

And Associated Rocks

GEOLOGICAL SURVEY BULLETIN 1314-A

Geochemical Investigations 

of Some Black Shales 

And Associated Rocks

By JAMES D. VINE and ELIZABETH B. TOURTELOT

CONTRIBUTIONS TO GEOCHEMISTRY

GEOLOGICAL SURVEY BULLETIN 1314-A

The content and association of minor 

elements in some black shales 

deposited in various types of 

geologic environments

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

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

Washington, D.C. 20402 - Price 30 cents (paper cover)
CONTENTS

Page 

Abstract_____________________________________________________ Al

Introduction._____________________________________________________ 2

Acknowledgments-______________________________________________ 4

Description of sample sets________________________________________ 5

Lower Paleozoic shales of Arkansas_____._____________________ 5

Black shale from the Tacket Formation of Jewett, Emery, and

Hatcher (1965) of Kansas_____________________________ 6

Black shale from the Heath and Tyler Formations_______________ 6

Nonesuch Shale of Michigan and Wisconsin_____________________ 7

Oil shale from the Green River Formation of Colorado-____________ 8

Upper Cretaceous shales of Kansas____-_---_-_-_________________ 8

Upper Cretaceous shales of Texas_________________._____________ 9

Upper Mississippian shales of western Wyoming_________________ 9

Ashed shale from the Minnelusa Formation of South Dakota and

Wyoming_________________________________ _____________ 10

Analytical methods.__________ _____________________________________ 10

Statistical methods._______________________________________________ 11

Distribution of elements in the sample sets___________________________ 14

Lower Paleozoic shales of Arkansas___-_-_-_-____-__________.____ 23

Black shale from the Tacket Formation of Jewett, Emery, and

Hatcher (1965) of Kansas...___________________ 27

Black shale from the Heath and Tyler Formations_______________ 29

Nonesuch Shale of Michigan and Wisconsin _____ ___________ 32

Oil shale from the Green River Formation of Colorado..___________ 33

Upper Cretaceous shales of Kansas_________-______-_---____-____ 35

Upper Cretaceous shales of Texas__________-_____-___-_-________ 36

Upper Mississippian shales of Western Wyoming._________________ 37

Ashed shale from the Minnelusa Formation of South Dakota and

Wyoming______________________________________________ _ 38

Summary______________ _____________________________________ _ 39

References cited____________________ ______________ ______ 42

m
IV CONTENTS

ILLUSTRATIONS

Page

FIGURE 1. Map of conterminous United States showing localities of

black-shale sample sets 13-21______________________ A3

2. Explanatory vector diagrams________________________ 13

3-11. Rotated two-dimensional vector diagrams showing principal components of the correlation matrix:

3. Set 13, lower Paleozoic shales of Arkansas______ 22

4. Set 14, black shale from the Tacket Formation of

Jewett, Emery, and Hatcher (1965) of Kansas __ 23

5. Set 15, black shale from the Heath and Tyler 

Formations and equivalents of Montana and 

Idaho_______-_-__-_.-.____________ 24

6. Set 16, Nonesuch Shale of Michigan and Wisconsin. 25

7. Set 17, oil shale from the Green River Formation

of Colorado-______________________ 26

8. Set 18, Upper Cretaceous shales of Kansas,___ _ 27

9. Set 19, Upper Cretaceous shales of Texas-_______ 28

10. Set 20, Upper Mississippian shales of western

Wyoming__-_______________________________ 29

11. Set 21, ashed shale from the Minnelusa Formation

of South Dakota and Wyoming-..____________ 30

12. Concentration range of chemical elements in nine sample

sets of black shale and associated rocks________________ 40

TABLES

Page 

TABLE 1. Summary description of sample sets 13-21______________ A2

2. Stratigraphic sequence of formations from which 32 samples of lower Paleozoic shales of Arkansas were collected. 5

3. Percentile and mean values in analysis of black-shale

sample sets_____________________ _ ___ _ 15

4. Element groupings in subsets of set 15, samples from the 

Heath and Tyler Formations and equivalents of Montana and Idaho____________________ ___________ 32
CONTRIBUTIONS TO GEOCHEMISTRY

GEOCHEMICAL INVESTIGATIONS OF SOME BLACK 

SHALES AND ASSOCIATED ROCKS

By JAMES D. VINE and ELIZABETH B. TOTJKTELOT

ABSTRACT

The distribution of chemical elements in nine sets of samples of black shale 

and associated rocks was examined statistically to learn which elements accompany the major rock-forming constituents, such as detrital minerals, carbonate minerals, and organic matter. The rocks sampled range in age from 

Precambrian to Eocene and in environment of deposition from eugeosynclinal 

to carbonate lake. These and other differences in the samples result in varied 

minor-element distribution patterns.

Elements associated primarily with the detrital fraction of these sets include 

the major elements silicon, aluminum, and potassium and the minor elements 

titanium, boron, gallium, scandium, and zirconium. In any individual set, these 

elements generally show a small range in abundance. Those associated with the 

carbonate fraction show much greater ranges in abundance. Calcium and 

strontium together are associated with the carbonate fraction in eight sample 

sets; manganese is associated with the carbonate fraction in the Tacket Formation of Jewett, Emery, and Hatcher (1965), a black shale of Kansas, the 

Nonesuch Shale of Michigan and Wisconsin, and the Minnelusa Formation of 

South Dakota and Wyoming; and magnesium is associated with the carbonate 

fraction in the Minnelusa Formation and in the Tyler Formation of central 

Montana.

Minor elements associated with the organic matter in these sets tend to 

show a greater range of values within individual sets and a greater range 

of median values between sets than do those elements in the detrital fraction; 

their associations also tend to differ between sets. Elements associated with 

organic matter in the Tacket Formation of Kansas include chromium, molybdenum, silver, vanadium, and yttrium; those in the Heath Formation of 

central Montana include molybdenum, silver, vanadium, zinc, and possibly 

copper; and those in the Minnelusa Formation of South Dakota and Wyoming 

include lead, molybdenum, nickel, silver, and probably copper. The epigenetic 

enrichment of copper and silver in the Nonesuch Shale of Michigan and Wisconsin shows no association with major rock constituents, which indicates that the 

distribution was not lithologically controlled. The more mobile elements, chromAl
A2 CONTRIBUTIONS TO GEOCHEMISTRY

ium, cobalt, copper, lead, molybdenum, nickel, silver, uranium, vanadium, yttrium 

and zinc, should be given primary consideration in any search for "metal-rich" 

black-shale deposits, especially in the Heath Formation of central Montana, 

the Minnelusa Formation of South Dakota and Wyoming, and the Tacket 

Formation from the Pleasanton Group of Late Pennsylvanian age in Kansas.

INTRODUCTION

This is the fourth in a series of reports that discuss the chemical 

distribution of elements in black shale and associated rocks. Previous 

reports describe the distribution of major and minor elements (1) in 

shelf and eugeosynclinal black shales, grouped into sample sets 1-4 

(Vine, 1966), (2) in black shales deposited in hypersaline, miogeosynclinal, and shelf environments, sample sets 5-8 (Vine, 1969); and 

(3) in black shales deposited in intracratonic trough and platform 

types of environments, sample sets 9-12 (Vine and others, 1969). This 

report discusses the geochemistry of nine more sample sets (13-21) 

of black shale and associated rocks deposited in diverse environments. 

The localities where the sample sets were collected are shown in 

Figure 1, and descriptions of the sets are summarized in table 1.

TABLE 1. Summary description of sample sets 13-81

Set Stratigraphic name Age State

Number Type of Environment of 

of sample deposition

13

14 

15 

16

Collier Shale, Mazarn 

Shale, Blakely Sandstone, Womble Shale, 

Bigfork Chert, and 

Polk Creek Shale. 

Tacket Formation of 

Jewett, Emery, and 

Hatcher (1965). 

Heath and Tyler 

Formations and 

equivalents. 

Nonesuch Shale ____

Early Paleozoic...

Pennsylvanian __

Mississippian and 

Pennsylvanian.

. Precambrian ......

Arkansas ...... 

Kansas ........

Montana and 

Idaho.

Michigan and

32

19 

28 

20

Outcrop...

 ..do..... 

.....do..... 

Core ......

Eugeosynclinal.

Epicontinental 

shelf.

Intracratonic 

basin.

Near-shore shelf

17 Green River Formation.

18 Sharon Springs Member 

of the Pierre Shale 

and upper part of the 

Nlobrara Formation.

19 Eagle Ford Shale and 

Buda Limestone.

20 Unnamed equivalent to 

Health (?) Formation.

21 Minnelusa Formation 

(lower part).

Wisconsin. 

Eocene______ Colorado......

Cretaceous_._ Kansas........

29 Quarry.... Carbonate lake. 

59 Cuttings.. Epicontinental 

shelf.

.__do______ Texas.........

Mississippian___ Wyoming_...

28 Core. Do.

Pennsylvanian South Dakota 

andWyoming.

14 Outcrop... Intracratonic 

basin.

22 __do..... Epicontinental 

shelf.
BLACK SHALES AND ASSOCIATED BOCKS A3
A4 CONTRIBUTIONS TO GEOCHEMISTRY

The term "black shale" as used here and in our preceding reports 

includes a variety of dark-colored fine-grained sedimentary rocks deposited in marine or saline lake environments and composed of a mixture of detrital minerals, chemically or biologically precipitated 

minerals, and organic matter. The organic matter is commonly a 

minor but characteristic feature of these rocks, whose end members include claystone, siltstone, limestone, dolomite, anhydrite, chert, phosphorite, and coal. The fine-grained texture of these rocks makes 

definition of precise boundaries between the various types impractical, 

especially for field classification. Even with refined laboratory techniques, assignment of a specific name to each rock becomes rather arbitrary. Many of the sample sets include a wide variety of rock types, 

all included under the general term "black shale."

ACKNOWLEDGMENTS

The collection of sample sets 13-21 was greatly facilitated by the 

cooperation and helpful suggestions of colleagues familiar with the 

stratigraphy of specific areas. Philip J. Sterling and Charles G. Stone, 

geologists with the Arkansas Geological Commission, aided in the collection of the lower Paleozoic black shales from the Ouachita Mountains in Arkansas (set 13). Samples of the Heath and Tyler Formations 

in Montana (set 15) were collected in the company of Edwin K. 

Maughan of the U.S. Geological Survey, who was studying the stratigraphy of these rocks at that time. Core samples of the Nonesuch 

Shale (set 16) were collected by Walter S. White and the late James 

C. Wright of the Geological Survey for their studies of copper deposits 

in Michigan and were kindly provided to the writers for inclusion in 

this study. The samples of the Green Eiver oil shale (set 17) were collected by James D. Vine and James G. Palacas of the Geological Survey 

from a quarry on an unpatented oil-shale claim held by John Savage 

of Rifle, Colo., with his permission. Drill cuttings of the Sharon 

Springs Member of the Pierre Shale and the upper part of the Niobrara Formation were provided by James E. Gill of the Geological 

Survey with the cooperation of the Kansas State Geological Survey. 

Core samples of the Upper Cretaceous shales of Texas (set 19) were 

provided by D. Hoye Eargle of the Geological Survey. J. D. Love of the 

Geological Survey suggested the section of the Upper Mississippian 

shales (set 20) in the Hoback Canyon, of western Wyoming. Computer 

programming and assistance were provided by E. N. Eicher, F. B. 

Sower, G. I. Seiner, and George Van Trump, Jr.
BLACK SHALES AND ASSOCIATED HOCKS A5

DESCRIPTION OF SAMPLE SETS 

LOWEB PALEOZOIC SHALES OF ARKANSAS

Set 13 consists of 32 samples of black shale and siliceous shale collected from natural outcrops and roadcuts in the central Ouachita 

Mountains in parts of Pulaski, Saline, Garland, and Montgomery 

Counties, Ark. Samples were collected from the Collier Shale of Cambrian age and the Mazarn Shale, Blakely Sandstone, Womble Shale, 

Bigfork Chert, and Polk Creek Shale, all of Ordovician age, as shown 

in table 2. These rocks range in lithology from clay shale to siliceous

TABLE 2. Stratigraphic sequence of formations from which 82 samples of lower

Paleozoic shales of Arkansas were collected 

[Description modified from Goldstein and Hendricks (1953)]

System

o

1

&.,i^ O o^-f 6>i

Cambrian

Formation

Polk Creek 

Shale

Bigfork Chert

Womble Shale

Blakely Sandstone

Mazarn Shale

Crystal Mountain Sandstone

Collier Shale

Thickness 

(feet)

100-200

500-700

250-1, 000

0-500

1, 000 ±

500-850

200-500

Description

Shale, black, graphitic; contains graptolites.

Chert, hard, gray to black; 

black shale; dark-colored 

fossiliferous cherty limestone.

Shale, black to green; contains 

thin layers of limestone and 

argillaceous sandstone.

Sandstone, gray, quartzitic; 

some calcareous sandstone 

and minor amounts of black 

and green clay shale.

Shale, black and green, banded. 

Thin layers of gray sandstone, and in some areas 

thin lenses of bluish-black 

limestone.

Sandstone, massive, light-gray, 

calcareous to quartzitic.

Shale, black, graphitic; and 

dark-colored siliceous limestone. Some dense black 

chert.

Number 

of 

samples

4

4

13

3

7

0

1

364-433 69-
A6 CONTRIBUTIONS TO GEOCHEMISTRY

shale and chert. All contain disseminated organic matter, and some 

are graphitic. The samples from the Polk Creek Shale and at least one 

sample from the Womble Shale contain graptolites. Bedding is commonly at a slight angle to the cleavage which formed during regional 

metamorphism. Metamorphic minerals, however, are not characteristic 

of these rocks. The Bigfork Chert was regarded by Goldstein and 

Hendricks (1953) as the oldest of the siliceous rocks characteristic of 

the Ouachita facies, but probably all these formations were deposited 

in or near the principal downwarp of the Ouachita geosyncline. Although the samples appear similar in hand specimen, this similarity 

may be due more to the metamorphic texture and structure of the rocks 

than to their environments of deposition.

BLACK SHALE FROM THE TACKET FORMATION OF JEWETT, 

EMERY, AND HATCHER (1965) OF KANSAS

Set 14 consists of 19 samples of black shale from the Tacket Formation in the Pleasanton Group of Pennsylvanian age in Labette and 

Neosho Counties, Kans. In this area, the Tacket Formation occurs at 

the top of the Pleasanton Group; it is overlain by the Hertha Limestone, which forms the base of the Kansas City Group, and is underlain by the Checkerboard Limestone of the Pleasanton Group. The 

Pleasanton Group forms the base of the Missouri Series, which lies 

unconformably on the Marmaton Group of the Des Moines Series. In 

contrast to the many thin black-shale units that overlie coal beds in 

the Pennsylvanian System, black shale in the Tacket Formation is 

associated primarily with limestone beds. It is a marine unit that 

was probably deposited in a shallow-water shelf not far offshore. In 

the area where the Tacket black shale was sampled, it is estimated to 

be at least 20 feet thick. Jewett, Emery, and Hatcher (1965, p. 8) reported that it is 40 feet thick near Parsons and ranges in thickness 

from 15 to 60 feet in southeastern Kansas. Natural exposures of this 

unit are very poor, but relatively fresh samples were collected from 

roadcuts. The 19 samples in set 14 represent channel samples from 

three roadcuts that include 27 feet of strata. The amount of overlap 

or duplication of strata in the three sections could not be determined 

because of limited outcrops.

BLACK SHALE FROM THE HEATH AND TYLER FORMATIONS

Set 15 consists of 28 samples collected from the Heath Formation 

of Mississippian age and the Tyler Formation of Pennsylvanian age 

in Montana and Idaho. The two formations were differentiated and 

described by Maughan and Roberts (1967, p. B7-B14). Near the Big 

Snowy Mountains in central Montana, these two black-shale units are
BLACK SHALES AND ASSOCIATED ROCKS A7

locally superimposed and difficult to distinguish, although they are 

separated by an unconformity. In general, the black shales of the 

Heath Formation are associated with petroliferous limestone and gypsum, whereas those in the Tyler are associated with red shale and with 

sandstone beds that yield petroleum in several central Montana oil 

fields.

Of the 28 samples in this set, 18 were collected from outcrops in 

central Montana, chiefly from the flanks of the Big Snowy Eange in 

Golden Valley and Fergus Counties. The remaining 10 were collected from outcrops of black shale of the Heath (?) Formation, in approximately the same stratigraphic position, much farther west, in 

Beaverhead County, Mont., and Lemhi County, Idaho. The black shale 

in these 10 samples was tentatively regarded by E. K. Maughan (oral 

commun., 1965) as correlative with the Heath Formation, although 

the correlation is not well documented. In the interpretation of the 

analytical data for these samples, four subsets were considered: 15A, 

10 samples of the Heath(?) Formation from western Montana and 

adjacent parts of Idaho; 15B, 18 samples of the Heath and Tyler 

Formations from central Montana; 15C, 10 samples of the Heath 

Formation from central Montana; 15D, seven samples of the Tyler 

Formation from central Montana.

One sample of the Heath Formation from Central Montana was 

deleted from subset 15C because it contained an unusually large amount, 

of organic carbon, which suggested that it is more closely related to coal 

than to black shale, and because the high carbon and low minorelement content seemed likely to bias the statistical correlations unduly*

NONESUCH SHALE OF MICHIGAN AND WISCONSIN

Set 16 consists of 20 drill-core samples from the "striped bed" of 

the Nonesuch Shale of Precambrian age in Michigan. The striped bed 

is a zone of interlaminated carbonaceous claystone and subordinate 

amounts of impure silty limestone 6-8 inches thick, which lies about 30 

feet above the main zone of copper mineralization in the White Pine 

copper deposit, Ontonagon County, Mich. (White and Wright, 1954, 

figs. 5 and 6). According to James C. Wright (written commun., 1965), 

the striped bed is relatively uniform over the entire district and is 

the most organic rich, most limy, and most pyritiferous bed in the 

50-foot-thick cupriferous sequence. He described the silt fraction as 

consisting chiefly of quartz and detritus from mafic lavas in a clay 

matrix that is altered chiefly to chlorite. Of the 20 samples in this set, 

16 represent a Y-mile-long strip approximately normal to the presumed 

shoreline at WTiite Pine and include two mineralized samples with
A8 CONTRIBUTIONS TO GEOCHEMISTRY

visible chalcocite. Four samples represent other areas 15 to 70 miles' 

from White Pine in western Michigan, and one sample came from 

an area 87 miles from White Pine, in Bayfield County, Wis.

OIL SHALE FROM THE GREEN RIVER FORMATION OF COLORADO

Set 17 consists of 29 samples of oil shale from the Green Eiver 

Formation of Eocene age in the Piceance Creek Basin, Garfield 

County, Colo. Of these samples, 26 are large block samples collected 

from a quarry near Debeque, Colo., and three are outcrop samples 

collected from Cascade Canyon, about 14 miles north of Debeque. The 

quarry samples were collected from a stratigraphic interval of about 

18 feet that includes the Mahogany marker bed about 3 feet below 

the top. The Mahogany marker bed is a distinctive bed of analcime 

about half a foot thick that is useful as a stratigraphic marker for the 

rich oil-shale zone known locally as the Mahogany ledge (Waldron and 

others, 1951). The Cascade Canyon samples were collected from approximately the same stratigraphic interval. In contrast to the depositional history of most of the other sample sets included in this study, 

the oil shale of the Green Eiver Formation was deposited in a sodium 

carbonate-rich lake rather than in a marme environment. Moreover, 

the organic matter in these samples is a solid material called kerogen, 

which is largely convertible to oil on heating in a retort. The mineral 

matter is a fine-grained mixture of authigenic and detrital minerals, 

including quartz, dolomite, calcite, analcime, mica, and plagioclase, 

and minor amounts of pyrrhotite or pyrite. The rocks are characteristically laminated with an alternation of organic-rich and relatively 

organic-poor laminae.

UPPER CRETACEOUS SHALES OF KANSAS

Set 18 consists of 57 samples of drill cuttings collected at 5-foot 

intervals from the Sharon Springs Member of the Pierre Shale and 

the upper part of the underlying Niobrara Formation, both of Late 

Cretaceous age. These samples were collected in connection with a 

study of the type area of the Sharon Springs Member by J. E. Gill, 

W. A. Cobban, and L. G. Schultz (unpub. data) and include 44 samples 

from the Sharon Springs Member, ranging in depth from 0 to 220 feet, 

and 13 from the upper part of the Niobrara Formation, ranging in 

depth from 220 to 300 feet. Two samples from a nearby outcrop are 

included in set 18 for a total of 59. One of these surface samples is a 

phosphatic nodule; the other is a dark-gray shale. Gill, Cobban, and 

Schultz recognize three subdivisions of the Sharon Springs Member: 

a lower unit of soft dark shale 115 thick thick, a middle unit of hard
BLACK SHALES AND ASSOCIATED ROCKS A9

organic-rich shale 90 feet thick, and an upper unit of hard slightly 

phosphatic shale about 10 feet thick. The entire member is marine and 

contains abundant vertebrate remains but relatively few mollusks. The 

shales are medium gray to black and are composed of clay minerals 

and quartz and minor amounts of pyrite, dolomite, and organic matter. 

The Sharon Springs Member contains many thin bentonite beds, 

rarely as much as 1 foot thick, and numerous carbonate rich concretions. The lower part of the member is transitional with the underlying Niobrara Formation, which is characterized by a greater content 

of dispersed carbonate minerals. In general, the samples consist of finegrained detrital sediment with variable amounts of carbonate, either 

bedded or in the form of concretions, and thin interbeds of altered 

volcanic ash.

UPPER CRETACEOUS SHALES OF TEXAS

Set 19 consists of 28 core samples of the Eagle Ford Shale and Buda 

Limestone of Late Cretaceous age in southern Texas. The Eagle Ford 

Shale forms a consistently radioactive zone in the Upper Cretaceous 

formations that underlie the Texas coastal plain and is commonly used 

as a stratigraphic marker in subsurface logs. The core samples in set 

19 are from cores collected by D. Hoye Eargle for his study of the 

radioactivity and uranium content of these rocks (Eargle and Hollingsworth, 1957). The samples for this study were selected from five 

drill cores from Guadalupe, Caldwell, Karnes, and La Salle Counties, 

Tex. Twenty-six samples are from the Eagle Ford and two are from 

the underlying Buda. They range in lithology from dark-gray laminated clay to limestone. Abundant shell fragments are present in the 

Buda Limestone samples.

UPPER MISSISSIPPIAN SHALES OP WESTERN WYOMING

Set 20 consists of 14 samples of dark-gray to black shale collected 

from an interval of shale and limestone nearly 70 feet thick that is 

exposed on the north side and about 1 mile east of the mouth of Hoback 

Canyon, Teton County, Wyo. The sampled interval lies directly above 

a unit identified as the Darwin Sandstone Member of the Amsden 

Formation in a stratigraphic section described by Wanless, Belknap, 

and Foster (1955, p. 22-29). The stratigraphic identity of the rocks 

is in question, however, for San do and Dutro (1960, p. 125) reported 

fossils of Late Mississippian age in limestone beds interbedded with 

and overlying the dark shales, which indicates that these rocks may be 

approximately equivalent to the Heath Formation of the Big Snowy 

Group in Montana.
A10 CONTRIBUTIONS TO GEOCHEMISTRY

The rocks sampled range in lithology from soft black claystone to 

dark-gray fissile shale and carbonaceous brownish-gray siltstone. 

Limestone and sandstone beds in the sequence were not sampled, nor 

were any of the lower shales found to be interbedded with gypsum. The 

samples are weathered and include various secondary minerals associated with the weathering of carbonaceous rocks, including jarosite 

and limonite.

ASHED SHALE FROM THE MINNELUSA FORMATION OP 

SOUTH DAKOTA AND WYOMING

Set 21 consists of 22 ashed samples of black shale and associated 

rocks from the lower part of the Minnelusa Formation of Pennsylvanian age. The samples were collected from outcrops in the southern 

Black Hills of western South Dakota and eastern Wyoming. Black 

silty shale and carbonaceous limestone occur in thin beds 0.5-2 feet 

thick interbedded with sandstone. Some of the shale beds approximate an impure canneloid coal in composition (J, M. Schopf, written 

commun., 1951) and show as much as one-third loss on ignition. These 

black shales are commonly used as stratigraphic markers on subsurface 

well logs because of their persistently high radioactivity. Outcrops of 

the black shales are few, but they occur in several canyons in the southern Black Hills, including Hot Brook Canyon, about 2 miles northwest 

of Hot Springs, S. Dak., and in Kedbird Canyon, about 10 miles southeast of Newcastle, Wyo. Of the 22 samples in this set, 16 were collected 

from three closely spaced outcrop areas in Hot Brook Canyon: four 

from Redbird Canyon, one from Frannie Peak about 4 miles west of 

Redbird Canyon, and one from Boles Canyon about 9 miles east of 

Newcastle. The samples were ashed because of their high loss on ignition, thereby reducing the matrix problems that sometimes arise during 

spectrographic analysis of organic-rich samples that are not ashed. 

Concentrations of uranium and other metals in these black shales have 

been reported previously by J.D. Love (written commun., 1951), by 

Duncan (1953), and by Davidson and Lakin (1961).

ANALYTICAL, METHODS

The analyses on which this report is based were made primarily by 

the routine six-step emission spectrographic method, which is similar 

to the three-step method described by Myers, Havens, and Dunton 

(1961). Results for the six-step method are identified with geometric 

intervals whose boundaries are 1.2, 0.83, 0.56, 0.38, 0.26, 0.18, 0.12, 

0.083 and so forth, and are arbitrarily reported as the geometric midpoints of these intervals, using the numbers 1,0.7,0.5, 0.3, 0.2,0.15, 0.1,
BLACK SHALES AND ASSOCIATED ROCKS All

O.OT, and so forth. The precision of a reported value is approximately 

plus or minus one interval at 68-percent confidence, or two intervals at 

95-percent confidence.

Quantitative spectrography was used in the analysis for minor 

elements in sample set 16. The results have an overall accuracy of ±15 

percent except near the limits of detection, where only one digit is 

reported. The elements near the lower limits of detection in this set 

include boron, gallium, lead, silver, yttrium, and ytterbium. Chemical 

methods were used to determine arsenic, selenium, and sulfur in set 

16 and selenium in set 20. Zinc in set 16 and nickel, chromium, and iron 

in set 17 were determined by atomic-absorption analysis. A betagamma sealer was used to determine equivalent uranium in sets 18, 

19, and 20.

Separate analyses were made for total carbon and carbon in carbonate minerals following the methods outlined by Tourtelot, Huffman, and Eader (1964, p. D74). Organic carbon was calculated by 

computing the difference between total carbon and mineral carbon. 

The lower limit of detection for total and mineral carbon is about 

0.02 percent. The approximate precision of the method is about 0.02 

percent for samples containing small amounts of carbon. However, the 

precision may be reduced by a factor of about 10 for samples containing large amounts of carbon because of the necessity of using a 

smaller quantity of the sample in order to keep the evolved gas within 

the volume limits of the equipment. When subtracting mineral carbon 

from total carbon to determine organic carbon content, it is customary 

to show one less significant figure than is used for total or mineral 

carbon. Analyses for oil, gas, water, and ash were made on samples 

of oil shale in set 17 using the modified Fischer retort as described by 

Stanfield and Frost (1949).

STATISTICAL, METHODS

Statistical analyses of the nine sets of chemical data were conducted 

by methods similar to those described in previous reports (Vine, 1966, 

1969; Vine and others, 1969). The 5th, 25th, 50th, 75th, and 95th percentiles and the arithmetic and geometric means were calculated for 

each constituent. The coefficient of correlation was calculated for each 

pair of constituents after first making a log transformation to place 

the data in a more nearly normal frequency distribution. Because concentrations of some constituents in some samples were outside the 

limits of detection by the analytical methods used, some determinations by the analysts were reported as "greater than" or "less than" 

specified concentrations. These determinations were considered as given 

in the derivation of median and percentile concentrations and, where
A12 CONTRIBUTIONS TO GEOCHEMISTRY

these were few in number relative to the determined concentrations, 

they were replaced by fairly arbitrary values in estimating log correlation coefficients. The only justification for this procedure is that the 

computed coefficients are not highly sensitive to the arbitrary values 

used.

Principal-component analysis of each correlation matrix was used to 

identify groups of associated elements, after substitution for indeterminate values. This technique, described by Harman (1960), has recently been applied to a variety of geologic problems, some of which 

were described by Imbrie and VanAndel (1964), Griffiths (1966), and 

Miesch, Chao, and Cuttitta (1966). The method involves constructing 

radial vectors for each constituent so that the cosine of the angle between any two vectors is equal to the coefficient of correlation. For 

two-factor analysis, the vectors are then rotated and projected onto a 

two-dimensional diagram on which axes that will best represent most 

of the data have been selected. Figure 2A shows an example of a vector 

diagram with a strong positive correlation between aluminum and titanium (the cosine of the small angle between these two vectors approaches + 1). A strong negative correlation is shown between aluminum and mineral carbon (the cosine of the nearly 180° angle between 

these two vectors approaches 1). Little or no correlation is shown between aluminum and organic carbon (the cosine of the nearly 90° angle 

approaches 0). The vector for sodium is short, indicating that it is 

poorly represented in this two-dimensional diagram and probably has 

a low correlation with the other elements in the diagram. The vector 

for molybdenum shows a moderately strong correlation with organic 

carbon. Thus, when two elements plot close to each other near the unit 

radius a strong correlation is indicated, but when they have short vectors and plot close to each other near the center of the circle they may 

or may not correlate well.

In some sets where the vectors are short because they are poorly 

represented in two dimensions (the eigenvalues of the correlation 

matrices and communalities of variables on rotation indicate the probability of more than two principal components), it was desirable to 

use three-factor analysis to search for additional element groups. The 

interpretations from such three-dimensional diagrams are described 

but not illustrated. Even the three-component analysis sometimes fails 

to identify element groupings clearly where the coefficients of correlation have low levels of significance:

In the diagrams (figs. 3-11) illustrating the two-factor analyses of 

data for sample sets 13-21, the radial lines have been omitted for 

clarity, and only the position of the constituent within a circle of unit 

radius is shown. Figure 2Z? shows such an example, derived from the
BLACK SHALES AND ASSOCIATED HOCKS A13

364-433 69-
A14 CONTRIBUTIONS TO GEOCHEMISTRY

vector diagram in figure 2J.. The stippled segments of each diagram 

were added to suggest possible geochemical groupings of the elements. 

The resultant groupings may reflect different physical and chemical 

processes during the depositional and postdepositional history of each 

rock unit.

The fact that the correlation data are part of a closed array complicates interpretation of the element groups. This problem, described 

by Chayes (1960), may be thought of as one of dilution. As an example, 

consider a set of samples that includes the major rock constituents, 

quartz, carbonates, and clay. Each of the end members, which are 

represented by the corresponding three lithologies, siltstone, limestone, 

and shale, contains only one of the three constituents: thus a built-in 

negative correlation must exist between at least two of the principal 

constituents. Also, a corresponding positive correlation may be imposed 

on a certain pair of minor elements that vary with a major constituent 

even where there is little geochemical association between the minorelement pair. The process of dilution, therefore, affects the magnitude 

of some of the correlations that appear on the vector diagrams, but the 

problem is basically one of interpretation.

DISTRIBUTION OF ELEMENTS IN THE SAMPLE SETS

The following sections describe the abundance and distribution of 

elements detected in individual sample sets. Table 3 lists percentile and 

mean values calculated from the spectrographic and chemical analyses 

of the samples. Data from table 3 are used in the following discussions 

of element abundances in the individual sets, and the results of factor 

analysis (fig. 3-11) form the basis for interpretation of element associations within the sets. Statements about "average" or "normal" element content imply that the content is close to the median value calculated from the median contents of sets 1-20 (Vine, 1966, 1969; Vine 

and others, 1969). (Set 21 is not included in the calculations because 

the samples were ashed prior to analysis.) The median values of most 

of the reported elements do not differ greatly from those of the average element contents in shale as listed by Turekian and Wedepohl) 

(1961, table 2). Exceptions are molybdenum and copper, both of which 

show medians for black shales that are considerably higher than the 

averages shown by Turekian and Wedepohl. Statements about relatively high concentrations of some elements also are based on comparisons of all values reported for the first 20 sample sets.
BLACK SHALES AND ASSOCIATED ROCKS A15

TABLE 3. Percentile and mean values in analyses of black-shale sample sets,

in percent

[Set: 13, Lower Paleozoic shales; 14, Tacket Formation; 15, Heath and Tyler Formations; 16, Nonesuch 

Shale; 17, Green River Formation oil shale; 18, Kansas Upper Cretaceous shales; 19, Texas Upper Cretaceous shales; 20, Upper Mississippian shale; 21,Minnelusa Formation. Six-step semiquantitative spectrographic analyses of sample sets 15, 16, 18, and 20 by J. C. Hamilton, of sets 13, 14, 17, and 19 by A. L.- 

Sutton, Jr., and of set 21 by Harriet Neiman. Quantitative spectrographic analyses of sample set 16, indicated by asterisk (*), by Sol Herman. Analyses for total carbon by use of induction furnace, for mineral 

carbon by gasometric method, and for organic carbon by difference determined by I. C. Frost, E. J. 

Fennelly, and Dorothy Kouba. Zinc in set 16 and iron, chromium, and nickel in set 17 (analyses in parentheses) determined by atomic absorption method by J. D.Mensik and Claude Huffman, Jr. Selenium 

in sets 11 and 20 determined chemically by G. T. Burrow; sulfur in set 16 determined gravimetrically by 

E. J, Fennelly. Equivalent uranium in sets 18 and 20 determined radiometrically by WayneMountjoy, 

Lorraine Lee, and H. H. Lipp. Where many analyses for an element in a set are reported as indeterminate, 

the data for that set are omitted.]

Set

15

19 ........

21...........

13. .... __

14... . .

15.. .........

16..... ... .

17 ......

18 -

19.... ...... .

20 

21...-.. 

13..........

14.. ........

15.. .

16*.........

17..........

18.-.. ..

19..........

20-.... ..

21..........

13-. 

14..........

15.... ...

16*.. 

17.. 

18-.. ..

19.. ..

20-. 

21.-.-.....

P5 P25 PSO Pn PiS

Silicon

Aluminum

...... 25777

.. 55777

...... 

...... 33557

277 >10 >10

 .. 37777

Iron

.......... 0.5 1.5 2 3 5

 1.5 2 2 3 5

-. ..... .7 1.5 2 3 5

.. .... 2.4 3.1 3.3 3.8 6.0

.......... (1.2) (1.5) (2.0) (2.2) (2.8)

......-.-. 23335

--. ... .7 1.5 2 3 5

. .. 1.5 2 2 3 7

.......... .5 .7 2 3 5

Magnesium

. .... . 0.07 0.7 1.5 3 >10

 ... .3 .5 .5 .7 1.5

. -. .3 .5 .7 .7 1.5

.... ...... 1.3 1.6 1.9 2.0 2.5

 ... 23337

.......... .3 1 1.5 1.5 2

..... .... . .3 .5 .5 .5 .7

.......... .3 .5 .7 .7 .7

..... . . .72 2 >10 >10

Arithmetic 

mean

9.1

5.2

7.4

7.8

5.8

6.3

6.5

5.0

7.2

5.9

6.7

6.0

2.3

2.5

2.5

3.52

(1.94)

3.2

2.5

2.7

2.6

2.3

.61

.73

1.87

3.2

1.3

.54

.59

4.6

Geometric 

mean

8.5

4.4

5.4

6.6

5.4

5.3

6.4

4.8

6.7

4.7

6.6

3.4

1.9

2.4

2.1

3.46

(1.88)

3.0

2.1

2.5

1.9

1.1

.56

.64

1.85

2.7

1.1

.52

.56

3.3
A16 CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 3. Percentile and mean values in analyses of black-shale sdrnple sets,

in percent Continued

Set

Arith- Geometic metric

mean mean

Calcium

13-...--. . 0.01 0.02 0.07 0.2 7 1.1 0.12

14......-...-.. .. .15 .5127 1.7 .97

15.. . .31 2 >10 >10 4.5 2.3

16.................... 5 7 >10 >10 >10 6.8 8.8

17..._. .-. __ .15 >10 >10 >10 >10 __.____..._-----

IS.... .. .- 1 1.5 2 7 >10 4.2 2.9

19--.-...-......-.- 1.5 >10 >10 >10 >10 9.3 8.5

20.--......-.....--.. .07 .1 .15 .15 .3 .14 .13

21.._ ... .5 .7 2 >10 >10 4.8 2.8

	Sodium

13 . .. <0.05 0.07 0.2 1 1.5 0.53 0.26

14 .5 .7 1 1 1 .91 .89

15... .. .07 .2 .2 .3 1 .35 .25

16....- ..--.-.- 1.5 2 2 3 3 2.2 2.2

17-. . 1.5 2 3 3 5 2.8 2.7

18. . . .7 .7 1 1 1 .92 .90

19 .3 .7 .7 .7 1.5 .73 .65

20 -. .. .05 .1 .15 .15 .2 .12 .11

	Potassium

13... <1 2 3 3 5 2.6 2.3

14 . 1.5 2 2 3 3 2.4 2.3

15..- .. .... 1.5 2 2 3 5 2.5 2.3

16..... .......... 2 3 3 3 3 2.9 2.9

17 2 2 2 3 5 2.8 2.5

18-. 1.5 2 2 3 3 2.4 2.4

19... <1 1.5 2 3 3 2.0 1.8

20 ...... ...-.. . 1.5 5 5 5 5 4.3 4.0

	Titanium

13 0.07 0.15 0.2 0.3 0.5 0.22 0.17

14 .07 .1 .15 .2 .2 .15 .14

15 ._ . .07 .1 .15 .3 .5 .19 .15

16*.. .26 .38 .44 .55 .71 .47 .46

17. .1 .15 .15 .2 .2 .16 .15

18-.. . .05 .2 .2 .3 .3 .21 .18

19....-.-. -... .02 .07 .1 .15 .2 .12 .098

20... ... .-........ .3 .7 .7 .7 .7 .64 .63

21 .003 .03 .3 .5 .5 .28 .14

Manganese

13..-.. . - 0.002 0.003 0.007 0.01 0.02 0.010 0.0068

14.-- . . .003 .007 .01 .02 .1 .017 .011

15.. .002 .005 .01 .03 .1 .026 .013

16*... .-. .092 .15 .23 .28 .52 .25 .23

17-. - .015 .02 .03 .05 .05 .034 .030

18-. . .01 .015 .02 .02 .07 .020 .018

19.. .01 .015 .02 .03 .05 .025 .022

20.. . .. .001 .0015 .0015 .005 .03 .0057 .0027

21.. ., .003 .005 .007 .01 .01 .0078 .0074
BLACK SHALES AND ASSOCIATED ROCKS

TABLE 3. Percentile and mean values in analyses of Mack-shale sabn% 

in percent Continued

Set Ps Pas PEO P75 Pa,

Arithmetic 

mean

A17

\le sets,

Geometric 

mean

Silver

13......... .......

14.. 

15-.. 

16*...............

21.. ....... .......

.... <0.0001

<.0001

<.0001

<.0002

 < .0002

<0. 0001 

<.0001 

<.0001 

.0002 

<.0002

<0.0001 

.0002 

<.0001 

.0003 

<.0002

<0.0001 

.0007 

.0001 

.0004 

.0002

0.00015 

.001 

.0005 

.0024 

.0007

0. 000076 

.00040 

.00017 

.00041 

.00020

0.000074 

.00023 

.00014 

.00030 

.00012

Boron

13.... .........

U. ...............

15................

16*..- . .

17... .

18-- - 

19.......... ...

20-- - -.

.... <0.002

<.002

<.003

.002

<.003

<.002

<.002

.015

0.003 

.002 

.007 

.004 

.005 

.007 

<.002 

.02

0.007 

.003 

.01 

.005 

.005 

.015 

<.002 

.03

0.01 

.003 

.015 

.006 

.007 

.015 

.003 

.03

0.015 

.005 

.02 

.010 

.02 

.02 

.02 

.03

0.0077 

.0028 

.0096 

.0052 

.0072 

.012 

.0048 

.027

0.0057 

.0026 

.0081 

.0048 

.0058 

.0098 

.0027 

.025

Barium

13........... ...

14.... ... -.

15.-.. -.

16*-... ... ..

17.. ...... .

18-. 

19-. 

20... .........

21.... .

0.005

.015

.005

.026

.05

.02

.001

.005

.001

0.02 

.02 

.007 

.050 

.07 

.03 

.005 

.007 

.003

0.05 

.02 

.01 

.057 

.07 

.03 

.007 

.007 

.03

0.05 

.02 

.015 

.064 

.07 

.05 

.015 

.007 

.03

0.1 

.03 

.02 

.096 

.1 

.15 

.2 

.007 

.05

0.043 

.022 

.013 

.059 

.083 

.045 

.041 

.0066 

.026

0.033 

.021 

.011 

.056 

.070 

.039 

.0097 

.0065 

.017

Beryllium

13-. 

14. .... ...........

15.. 

16....... .........

21....... .........

.... <0.0001

.... <.0001

-... <. 00015

.... <.0002

.... <.0001

<0.0001 

<.0001 

<. 00015 

<.0002 

<.0001

<0.0001 

.0001 

<. 00015 

<.0002 

.00015

0.0001 

.0002 

<. 00015 

<.0002 

.0003

0.0003 

.0015 

.00015 

.0002 ..

.0005

0. 00011 

.00019 

.00012

.00022

0.000097 

.00012 

.00011

.00016

Cobalt

13.. 

14... ..

15.. .

16*.. 

17..... ........ ...

18.... ....

19.... 

20........ ........

21................

.... <0.0003

.... <,0003

.... <.0005

.... .0010

.... <.0007

.001

.... <.0005

.... <.0007

 . <.0003

<0.0003 

.0005 

<.0005 

.0014 

.0007 

.0015 

<.0005 

<.0007 

.0003

0.0005 

.0007 

.0005 

.0017 

.001 

.0015 

.0005 

.0007 

.0005

0.001 

.001 

.0007 

.0020 

.001 

.0015 

.0007 

.0007 

.0015

0.005 

.0015 

.002 

.0024 

.0015 

.002 

.001 

.002 

.007

0.0011 

.00081 

.00094 

.0017 

.00097 

.0014 

.00062 

.00079 

.0020

0.00056 

.00068 

.00067 

.0017 

.00091 

.0013 

.00056 

.00071 

.00069
A18 CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 3. Percentile and mean values in analyses of blacJc-shale sa^ynple sets,

in percent Continued

Set Pa Pas Pso Pra *, Arithmetic 

mean .

Geomean 

metric

Chromium

13--. 

14.. .

15... .

16*.........

17. ........

18.. ......

19..........

20-.. 

21.,- --.

.. ... 0.0015

 ..... .007

..... . .007

... .... . .0036

 ..... (.0018)

 ..... .005

..... - ..... .002

....... . .01

........... .0007

0. 005 0. 007 

. 015 . 05 

.01 .015 

. 0050 . 0052 

(.0023) (.0026) 

.007 .007 

.007 .01 

.015 .015 

. 003 . 015

0.007 

.07 

.02 

.0062 

(. 0029) 

.01 

.02 

.02 

.05

0.01

.1

.05 

.0030 

(.0035) 

.01 

.03 

.02 

.07

0.0065 

.046 

.019 

.0056 

(. 0026) 

.0086 

.015 

.016 

.032

0.0060 

.035 

.015 

.0055 

(. 0024) 

.0078 

.012 

.015 

.014

Copper

13 

14... .....

15- .

16*..... .

17 .......

18 ......

19 ........

20 ......

21... ........

.. 0.0015

.... . .002

.... .... ... .0015

. ..... .0064

.... .002

.. - .. .002

.... .0007

........... .0015

.... ... .001

0.003 

.005 

.003 

.0093 

.003 

.005 

.002 

.002 

.0015

0.005 

.01 

.003 

.012 

.007 

.007 

.003 

.003 

.005

0.007 

.01 

.01 

.024 

.007 

.007 

.005 

.005 

.015

0.01 

.015 

.015

.01 

.02 

.007 

.015 

.05

0.0054 

.0091 

.0056 

.14 

.0058 

.0072 

.0036 

.0039 

.014

0.0045 

.0079 

.0043 

.021 

.0052 

.0063 

.0029 

.0031 

.0058

Gallium

13... ........

14...........

15 .

16*... .--.

17... ......

18. .......

19 .......

20 .....

.... ... .... <0.0007

..... .001

.... . .0007

.... ... .... .0006

.... ... <.0007

. . ... .001

.... <.0005

........... .002

0. 0015 

.0015 

.001 

.0008 

.001 

.003 

.0005 

.003

0.002 

.0015 

.002 

.0010 

.0015 

.003 

.001 

.003

0.003 

.002 

.005 

.0011 

.0015 

.003 

.0015 

.003

0.005 

.002 

.005 

.0013 

.003 

.005 

.005 

.003

0.0022 

.0016 

.0027 

.00098 

.0014 

.0030 

.0015 

.0029

0.0018 

.0015 

.0021 

.00096 

.0013 

.0027 

.0010 

.0028

Lanthanum

13 

14 

15 

16...........

18. . .

19 . ...

20 .

21... .

-.. - <0.003

.......... <.002

..... . <.003

...... <.003

... . <.003

...... ..... <.003

. ..... <.005

.-. . <.003

<0.003 

<.002 

<.003 

.003 

<.003 

<.003 

<.005 

<.003

<0.003 

.003 

.003 

.003 

<.003 

<.003 

.005 

.003

0.003 

.003 

.005 

.005 

.003 

.003 

.005 

.007

0.005 

.005 

.005 

.005 

.003 

.005 

.5 

.01

0.0027 

.0026 

.0036 

.0037 

.0024 

.0025 

.0043 

.0046

0.0026 

.0024 

.0033 

.0036 

.0024 

.0024 

.0042 

.0034

Molybdenum

13... 

14... 

15 .. .

16*.. 

17 .

18- 

19 

20 . 

21 .

... ... <0.0005

... ... <.0005

 <.0005

 <.0004

...... <.001

...... .001

...... <.0005

... . <.0007

... ... .0003

CO. 0005 

<.0005 

<.0005 

.0010 

.001 

.0015 

<.0005 

.001 

.001

<0. 0005 0. 0005 

. 0015 . 01 

. 0005 . 007 

. 0012 . 0013 

. 0015 . 002 

.002 .003 

. 0005 . 002 

.002 .003 

.01 .07

0.002 

.02 

.02 

.0025 

.003 

.005 

.003 

.01 

.3

0.00048 

.0050 

.0042 

.0012 

.0015 

.0024 

.0011 

.0027 

.070

0.00039 

.0018 

.0014 

.0011 

.0013 

.0021 

.00077 

.0019 

.012
BLACK SHALES AND ASSOCIATED ROCKS

TABLE 3. Percentile and mean values in analyses of black-shale sapi 

in percent Continued

Set Ps P25 Pso «. "

Arithmetic 

mean

A19

nple sets,

Geometric 

mean

Niobium

15 ....... .

18 

20 ...

.. - <0.0015

.-..-- <.001

.... ... .0015

<0. 0015 

<-001 

.0015

<0. 0015 

.001 

.002

0.0015 

.001 

.002

0.003 

.0015 

.003

0.0014 

.0010 

.0019

0.0013 

.00094 

.0019

Nickel

13.- 

14.. .-..

15 

16* .

17 ........

18 .

19 

20-. ..

21 

....... 0.001

....... .002

....... .001

....... .0016

....... (.0030)

..... .. .003

.... ... .0015

...... .0007

.. .001

0.002 

.01 

.005 

.0023 

(.0035) 

.005 

.003 

.001 

.003

0.003 

.015 

.007 

.0027 

(. 0038) 

.007 

.005 

.0015 

.007

0.005 

.02 

.01 

.0032 

(. 0042) 

.007 

.005 

.003 

.02

0.007 

.03 

.03 

.0048 

(. 0059) 

.007 

.01 

.007 

.1

0.0035 

.014 

.0092 

.0029 

(.0040) 

.0060 

.0052 

.0021 

.026

0.0030 

.012 

.0063 

.0028 

(. 0039) 

.0057 

.0042 

.0017 

.010

Lead

13.. .

14..........

15.. ...

16*....-...

17.. 

18.--. ...

19.. . 

20.... ...

21...... ...

...... . <0.001

.. .. .001

-.--. . <.001

-. . . <.002

-.-.--. <.002

 .... . .001

... .... <.001

 ..... <.002

 ..... <.001

<0. 001 

.002 

.0015 

.006 

<-002 

.002 

<.001 

.002 

<.001

0.0015 

.003 

.002 

.011 

.003 

.003 

<.001 

.003 

.001

0. 0015 

.003 

.002 

.016 

.003 

.005 

.0015 

.003 

.005

0.002 

.005 

.005 

.026 

.005 

.005 

.002 

.01 

.03

0.0013 

.0027 

.0022 

.012 

.0027 

.0034 

.0011 

.0035 

.0068

0.0012 

.0025 

.0018 

.0095 

.0024 

.0030 

.0010 

.0029 

.0022

Scandium

13.. . 

14...... .

16..... ......

16*.... .

17.. ..

18... .

19.. .....

20..- ..

.... ....- <0.0003

.......... .0005

.. .... . <.0005

.. . . .0015

....... <.0007

.. ..... .0007

.. .. <.0005

.......... .0015

0.0005 

.0007 

.001 

.0016 

<.0007 

.001 

.0005 

.002

0.0007 

.001 

.0015 

.0020 

.0007 

.001 

.0007 

.002

0.001 

.001 

.0015 

.0020 

.0007 

.001 

.001 

.002

0.001 

.001 

.002 

.0021 

.001 

.0015 

.0015 

.002

0.00072 

.00084 

.0013 

.0019 

.00073 

.00097 

.00088 

.0020

0.00064 

.00081 

.0012 

.0018 

.00070 

.00096 

.00070 

.0020

Strontium

13.. ......

14...........

15-. .,

16*.. 

17.. .

18-. 

19.. ..

20.. ..

21... .

.. . . <0.001

..... .... . .01

.......... .007

. ... .014

... .... .07

..... . .015

02

..... .... . .005

..... ..... .007

0.0015 

.015 

.02 

.018 

.1 

.02 

.07 

.005 

.015

0.003 

.02 

.02 

.020 

.1 

.03 

.07 

.007 

.07

0.003 

.03 

.05 

.021 

.15 

.05 

.1 

.01 

.3

0.07 

.07 

.15 

.029 

.2 

.2 

.15 

.015 

.5

0.0089 

.024 

.059 

.020 

.12 

.059 

.088 

.0083 

.19

0.0035 

.021 

.033 

.020 

.10 

.037 

.077 

.0078 

.085
A20 CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 3. Percentile and mean values in analyses of black-shale sample sets,

in percent Continued

Set

13 ........

14 ........

15...........

16* ......

17 

18 

19... . ....... .

20.... .....

21...-..- ..

13 ......

14.............

15..... ...

16*...........

17... ... . ...

18. -...

19... .........

20- .......

21... . . ..

13... 

15 . ........

16*... ,.-.

18 

19 ........

20.... .. ......

14 

15 

16 ....... ...

18 . ........

21.... 

13..... .......

14...........

15...........

16*. .........

17-.- 

18..- 

19... 

20. ..........

Ps

......... 0.007

......... .007

......... .007

......... .0090

... ... .01

 .... .02

......... .007

......... .01

......... .003

......... 0.001

. . . <-001

. - . .001

......... .004

.. .... <.002

......... .0015

-. <.001

......... .003

......... <.001

. ..... <0.0001

......... <.0001

......... .0002

......... .0002

......... <.0001

......... .0005

 .... <0.02

..... .... <.03

... (.0055)

......... <.03

......... <.01

 ...... 0.0015

......... .0015

... ...... .003

......... .007

......... <.002

 ... .003

......... <.0015

.... .... . .02

Pis

0.015

.01

.01

.011

.01

.03

.015

.01

.01

0.001

.001

.002

.001

<.002

.002

001

.005

<.00l

n ftftfrt

.0001

.0003

.0003

.0001

.0005

<0.02

<.03

(. 0071)

<.03

<.01

0.005

003

flfVJ

.012

OO9

007

nni

.03

Pso

Vanadium

0.02

.05

.015

.012

.015

.03

.03

.015

.1

Yttrium

0.0015

.0015

.003

nm

<.002

.002

.0015

.005

.002

Ytterbium

0. 00015

.0002

.0003

.0003

.00015

.0005

Zinc

0.02

<.03

(. 0079)

<.03

<.01

Zirconium

0.01

.003

.005

fllQ

AflQ

.01

f)f\K

.03

PTS

0.03

.15

.02

.016

.015

.05

.03

.015

.3

0.002

.033

.003

.005

<.002

.003

.002

.005

.005

0.0002

.0003

.0003

.0003

.0002

.0005

0.05

.05

(. 0092)

.03

<.01

0.015

.01

.014

.005

.01

.007

.07

-Pa,

0.05

.2

.1

.024

.015

.05

.07

.02

.7

0.033

.007

.005

.007

.003 .

.003

.003

.005

.005

0.0003

.0005

.0004

.0005

.0003

.0007

0.1

.2

(.015)

.05

.02

0.02

.007

.015

.017

.007

.01

.01

.07

Arithmetic 

mean

0.023

.079

.028

.012

.014

.035

.029

.014

.23

0.0017

.0022

.0027

.0047

.0024

.0019

.0049

.0025

0.00018

.00025

.00030

.00031

.00019

.00053

0.033

.056

(. 0087)

.027

0.010

.0036

0079

.013

.0039

.0081

.0050

.044

Geometric 

mean

0.018

.041

.018

.010

.013

.034

.022

.013

.082

0.0016

.0018

.0024

.0047

.0022

.0017

.0048

.0018

0. 00016

. 00023

.00029

.00030

.00016

.00052

0.012

.029

(. 0085)

.025

0 QQ80

.0033

.0060

.013

.0035

.0075

.0042

.039
BLACK SHALES AND ASSOCIATED ROCKS A21

TABLE 3. Percentile and mean values in analyses of black-shale

in percent Continued

Set Ps P25

Arithmetic 

mean

Geometric 

mean

Total carbon

13-.. ............. 0.20 0.58 0.86 2.28 4.20 1.58 1.05

U.................... 2.51 5.58 8.99 13.24 18.80 10.19 8.31

16.................... .63 1.0 4.69 12.26 18.72 7.90 4.14

16.................... 1.95 2.47 2.97 3.58 6.07 3.17 3.01

18.................... 2.92 4.81 5.28 6.10 11.5 6.08 5.54

19..-.......--....-, 4.20 8.92 10.7 11.7 12.6 9.89 9.44

20.................... .19 .64 .81 1.12 2.06 ........................

21-..-..-........-... .82 1.20 8.32 11.0 14.1 7.45 4.96

Mineral carbon

13..-..--- - .. <0.01 0.03 0.05 0.08 2.28 0.35 0.072

14.................... <.02 .13 .19 .98 2.89 .69 .31

15.................... .02 .08 .33 3.43 5.0 1.51 .42

16.................... 1.59 2.07 2.66 3.10 5.71 2.78 2.65

18.. -. .15 .80 .97 2.23 7.93 2.15 1.16

19..- ............. .98 6.41 7.91 8.82 11.1 7.23 5.75

21.. ............... <.01 .08 .72 8.57 12.0 3.95 .68

Organic carbon

13.................... 0.1 0.4 0.8 1.2 11 1.23 0.76

14...-- ..... .. .7 3.3 8.9 13.1 22.4 9.49 6.78

15... ............... .3 .9 2.2 7.6 15.6 6.39 2.92

16-.......-........ . <.l .3 .4 .5 .9 .41 .36

18 - -.- . 1.6 3.3 4.0 4.4 5.1 3.84 3.54

19 .- - .4 1.5 2.8 3.6 4.5 2.66 2.12

20 .._.. ......... .2 .6 .8 1.1 2.1 .89 .74

21 .... <.l <.l 1.0 2.4 14.0 3.50 .72

Arsenic 

16..-.-.-... . ..- 0.0013 0.0032 0.0036 0.0040 0.0044 0.0034 0.00?3

Sulfur

16-.....-.- . ... 0.64 1.01 1.15 1.25 1.53 1.12 1.10

Selenium

16. . - <0.00005 <0.00005 <0.00005 0.00005 0.0001 0.000042 0.000034 

20 -. - . - .00005 .0001 .0001 .0002 .0003 .00016 .00014

Equivalent uranium

18..... . 0.001 0.002 0.002 0.003 0.003 0.0022 0.0020

19 . - <.00l .001 .001 .001 .003 .0013 .0012

20 .001 .002 .002 .002 .003 .0021 .0020

Oil

17. 2.8 5.0 8.2 13.3 24.6 10.1
A22 CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 3. Percentile and mean values in analyses of black-shale saf^nple sets,

in percent Continued

Set

Arithmetic 

mean

Geometric 

mean

Gas

17. 0.2 0.9 1.9 2.7 5.1 2.26 1.95

Water

17. 0.8 1.1 1. 5 1.8 2.2 1.63 1.47

17. .........

2L~ ... .

......... 68.6

......... 67

71.7

82

Ash

74.1

93

78.5

94

83.2

96

75.4

88.7

75.2

88.3

petrital group

FIGUKE 3. Rotated two-dimensional vector diagrams showing principal components of the correlation matrix for set 13, lower Paleozoic shales of 

Arkansas. Abnormally abundant elements shown in bold type.
BLACK SHALES AND ASSOCIATED ROCKS

Detritalgrpur

A23

FIGURE 4. Rotated two-dimensional vector diagrams showing principal components of the correlation matrix for set 14, black-shale from the Tacket 

Formation of Jewett, Emery, and Hatcher (1965) of Kansas. Abnormally 

abundant elements shown in bold type.

LOWER PALEZOIC SHALES OF ARKANSAS 

ELEMENT ABUNDANCE

The lower Paleozoic shales of Arkansas (set 13) are mostly finegrained detrital or siliceous rocks, chiefly claystones and cherts that 

contain relatively minor amounts of either organic matter or carbonate 

minerals. The predominantly detrital nature of these geosynclinal 

rocks is reflected by their high content of silicon and aluminum. The 

reported analyses show that all 32 samples of this set contain more 

than 10 percent silicon and that 21 of the samples contain more than 

10 percent aluminum. The medians of potassium, magnesium, iron, 

sodium, and titanium, listed in approximate order of decreasing 

abundance, are all 3 percent or less. The median content of calcium is
A24 CONTRIBUTIONS TO GEOCHEMISTRY

FIGURE 5. Rotated two-dimensional vector diagrams showing principal components of the correlation matrix for set 15, black shale from the Heath and 

Tyler Formations and equivalents of Montana and Idaho. Abnormally 

abundant elements shown in bold type.

only 0.07 percent, but four of the 32 samples contain 5 percent or 

more. The median content of mineral carbon is similarly low (0.05 

percent), but three samples contain more than 1 percent. The organic 

carbon content is also low; the median value for the set is 0.8 percent, 

and only one sample in the set has more than 5 percent. Of the minor 

elements, only vanadium and zirconium show any tendency to be 

locally enriched. The samples that contain 0.05 percent or more 

vanadium came from four formations: the Mazarn Shale, Blakely 

Sandstone, Womble Shale, and Polk Creek Shale. The samples with 

high zirconium content (0.02 percent) came from the Blakely Sandstone and Womble Shale. Most of the other minor elements are present 

in amounts that are average or less than average for black shales.
BLACK SHALES AND ASSOCIATED ROCKS 

rvtay subgroup

A25

Carbonate B'°up

FIGURE 6. Rotated two-dimensional vector diagrams showing principal components of the correlation matrix for set 16, Nonesuch Shale of Michigan and 

Wisconsin. Abnormally abundant elements shown in bold type.

ELEMENT ASSOCIATIONS

The two-factor vector diagram for the lower Paleozoic shales of 

Arkansas (fig. 3) shows three main groups of elements: a detrital 

group, a carbonate group, and an organic-matter group. No further 

subdivision of these groups was evident from a study of the threefactor analysis of the correlation matrix. Strong correlations exist 

between potassium, iron, magnesium, barium, gallium, scandium, and 

zirconium, and these represent the main part of the detrital group. 

Other elements less closely associated with the detrital group are 

manganese, boron, chromium, lead, cobalt (mostly with iron), and 

titanium. Organic carbon is inversely related to most of the elements 

in the detrital group. The carbonate group, consisting of calcium,
A26 CONTRIBUTIONS TO GEOCHEMISTRY 

Petrital group

Organic-rnat^er 

group

FIGURE 7. Rotated two-dimensional vector diagrams showing principal components of the correlation matrix for set 17, oil shale from the Green River 

Formation of Colorado. Abnormally abundant elements shown in bold type.

mineral carbon, strontium, and probably part of the sodium, is a cohesive group that appears to be independent of the others. Several 

other minor elements do not fit neatly into any of the major groups. 

Yttrium and ytterbium show a positive correlation with organic 

carbon, and so also does vanadium, but the correlation is not strong 

enough to form a cohesive group of constituents. Nickel and copper 

correlate strongly with each other but appear to be independent of the 

other elements. Boron and titanium, while listed with the detrital 

group, are in large part independent.
BLACK SHALES AND ASSOCIATED ROCKS A27

re group

FIGURE 8. Rotated two-dimensional vector diagrams showing principal components of the correlation matrix for set 18, Upper Cretaceous shales of 

Kansas. Abnormally abundant elements shown in bold type.

BLACK SHALE FROM THE TACKET FORMATION OF JEWETT, 

EMERY, AND HATCHER (1965) OF KANSAS

ELEMENT ABUNDANCE

The black shale of the Tacket Formation from the Pleasanton 

Group of southeastern Kansas (set 14) is an organic-rich detrital rock 

containing only minor amounts of carbonate minerals. Some samples 

also contain a small amount of phosphate. The major elements in the 

black shale include silicon, which exceeds 10 percent in all samples; 

carbon, which has a median of 9 percent; and aluminum, which is reported as 7 percent in 12 of the 19 samples. Iron, potassium, calcium, 

and sodium occur in approximately that order of decreasing abun-
A28 CONTRIBUTIONS TO GEOCHEMISTRY

FIGUBE 9. Rotated two-dimensional vector diagrams showing principal components of the correlation matrix for set 19, Upper Cretaceous shales of 

Texas. Abnormally abundant elements shown in bold type.

dance, and all are less than 5 percent at the median level. Most of the 

carbon occurs as organic carbon and only a small amount as carbonate 

carbon. Minor elements that are unusually abundant in these samples 

from the Tacket Formation include beryllium, chromium, molybdenum, silver, vanadium, and yttrium^; most of the other minor 

elements occur in at least average amounts.

ELEMENT ASSOCIATIONS

Three major groups of elements are evident from the vector diagram 

(fig. 4) constructed from the correlation matrix of set 14: (1) a detrital group of elements including titanium, scandium, aluminum, 

gallium, zirconium, potassium, sodium, boron, and cobalt, (2) a carbonate group consisting of mineral carbon plus calcium, strontium,
BLACK. SHALES AND ASSOCIATED ROCKS

Dgu\tal subgroup^

A29

Minor-f

FIGURE 10. Rotated two-dimensional vector diagrams showing principal components of the correlation matrix for set 20. Upper Mississippian shales of 

western Wyoming. Abnormally abundant elements shown in bold type.

and manganese, and (3) an organic-matter group consisting of organic 

carbon, zinc, copper, chromium, molybdenum, vanadium, silver, and 

possibly barium and yttrium. Several other elements fall outside the 

major groups; these include magnesium and beryllium, which fall 

between the carbonate and detrital mineral fractions, and nickel, iron, 

lead, and lanthanum, which fall between the detrital and organicmatter fractions. Lanthanum is so close to the center of the circle that 

it is probably independent.

BLACK SHALE FBOM THE HEATH AND TYLEB FOBMATIONS

ELEMENT ABUNDANCE

The black-shale samples from the Heath and Tyler Formations (set 

15) include a variety of fine-grained claystones and siltstones. Some of
A30 CONTRIBUTIONS TO GEOCHEMISTRY

FIGURE 11. Rotated two-dimensional vector diagrams showing principal 

components of the correlation matrix for set 21, ashed shale from the 

Minnelusa Formation of South Dakota and Wyoming. Abnormally abundant elements shown in bold type.

the samples contain abundant organic matter, and others, abundant 

carbonate minerals. About one-third of the samples are low in both 

organic matter and carbonate minerals. Analyses of the full set of 28 

samples show silicon as greater than 10 percent in 22 samples and 

aluminum and calcium as greater than 10 percent in 10 samples. The 

median value of total carbon is 4.7 percent. Of the 28 samples analyzed, 

13 contain 5 percent or more organic carbon, but only two contain 

5 percent or more mineral carbon. Calcium, iron, and potassium have 

medians of 2 percent, whereas magnesium and sodium are each less 

than 1 percent at the median level. Many of the minor elements are 

abundant in one or more of the samples in set 15 relative to the other 

sets of black-shale samples. Elements that may be regarded as enriched 

include gallium, which is relatively high at the 75th-percentile level,
BLACK SHALES AND ASSOCIATED ROCKS A31

and boron, chromium, molybdenum, silver, strontium, vanadium, and 

zinc, which all are relatively abundant in some samples. Lithium was 

reported as present in seven samples, cadmium in four, and cerium, 

with a value of 0.015 percent, in nine. In most black-shale samples 

these elements are below the lower limits of detection. Cobalt, copper, 

nickel, and lead are moderately abundant in some samples. The other 

reported elements, barium, beryllium, yttrium, ytterbium, lanthanum, 

scandium, and zirconium, occur in near-average amounts in this set.

ELEMENT ASSOCIATIONS

The two-factor vector diagram (fig. 5) for the full set of Heath and 

Tyler samples is not adequate to group most of the elements. Separation of the elements into the groups shown in figure 5, therefore, was 

supplemented with observations from three-factor analysis. Three 

detrital subgroups which lie within about a 90° arc on the two-factor 

vector diagram were distinguished: subgroup A, consisting of aluminum, titanium, scandium, iron, lanthanum, and cobalt; subgroup B, 

consisting of potassium, barium, magnesium, and sodium; and subgroup C, consisting of gallium, zirconium, and niobium. Three-factor 

.analysis shows boron to be more closely related to subgroup C, although 

it appears to fall in subgroup A of the two-factor diagram. The 

remaining groups lie within an adjacent arc that also covers about 

'90°; these include a carbonate group, organic carbon, and two other 

.groups of minor elements. The carbonate group consists of mineral 

^carbon, calcium, strontium, and possibly manganese. Organic carbon 

is not very closely associated with any of the minor elements, but it is 

probably most closely related to a group that includes copper, silver, 

zinc, vanadium, and molybdenum. On the two-factor vector diagram 

the carbonate group, organic carbon, and copper, silver, zinc, vanadium, and molybdenum form a single group. A second group of minor 

elements, consisting of chromium, nickel, and yttrium, falls about 

halfway between the detrital group and the other elements. Lead and 

jtterbium appear to be unrelated to any of the groups.

Samples from the Heath and Tyler Formations were separated into 

several subsets (see p. A7) which were statistically analyzed separately in an attempt to find explanations for some of the unusual 

-element groupings that were seen in the analysis of the full set (fig. 5). 

The resulting groups, as listed in table 4, suggest that the full set of 28 

.samples represents a statistically mixed population. Of particular 

significance are the association of silver, copper, zinc, nickel, chromium, 

molybdenum, and vanadium with organic carbon in the 10 samples 

from the Heath Formation in central Montana and the absence of that 

association in the seven samples from the Tyler Formation in the 

same area.
A32 CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 4. Element groupings in subsets of set 15, samples from the 

[Da, detrital subgroup A; Db, detrital subgroup B; DC, detrital subgroup C; Dd, detrital subgroup D; 

B; I, independent]

Element Al Fe Sc La Ti Co Ba K Mg Na B Ga

Set 15, all 28 samples.............. Da Da Da Da Da Da Db Db Db Db Da Do

Subset 15A, 10 western samples_ Da Da Da Da Db Da Db Db DC Da Db DbSubset 15B, 18 central Montana 

samples......................... Da Da Db Db Da Db Db Db Db Ma Da Da

Subset 15C, 10 Heath Formation, 

central Montana, samples....... Da Db Db Db Da Db Db Db Db Ma DC Dd

Subset 15D, seven Tyler Formation, central Montana, samples.. Da DC Db Da Db Db DC C C I Da Da

NONESUCH SHALE OF MICHIGAN AND WISCONSIN 

ELEMENT ABUNDANCE

The fine-grained detrital rocks of the Nonesuch Shale of Precambrian age in Michigan and Wisconsin (set 16) have a moderately high 

content of carbonate minerals and contain a minor amount of organic 

matter. Of the major elements (as determined by six-step spectrographic analysis), silicon is reported as more than 10 percent in all 20 

samples and calcium is reported as more than 10 percent in 15 samples. 

Aluminum is reported as 7 percent in 15 samples and as less than that 

in the other five. Carbon, iron, potassium, sodium, and magnesium are 

all less than 5 percent but greater than 1 percent at the median level. 

Sodium, with a median content of 2 percent, is notably higher than in 

most of the other black-shale sample sets, and potassium, with a median of 3 percent, is also higher than average. The high sodium and potassium contents probably reflects the abundance and nature of the 

clay-mineral fraction of the rock. The mineral carbon content, which 

ranges from 1.59 to 5.71 percent, is much more uniform in set 16 than 

in most of the other sample sets. The organic carbon content is uniformly low, ranging from less than 0.1 to 0.9 percent. Of the minor 

elements (as determined by quantitative spectrographic analysis), 

copper, silver, lead, titanium, manganese, and yttrium tend to be abnormally abundant in some samples. Most of the other minor elements 

are present in amounts that are about average or less than average for 

black-shale samples.

ELEMENT ASSOCIATIONS

The elements detected in the Nonesuch Shale samples from Michigan 

and Wisconsin can be separated into four principal groups on the 

two-factor vector diagram (fig. 6) : (1) a detrital group, (2) a carbonate group inversely related to the detrital group, (3) a minor-element 

group, and (4) an epigenetic group inversely related to the minor-
BLACK SHALES AND ASSOCIATED ROCKS A33

Heath and Tyler Formations and equivalents of Montana and Idaho

O, organic-carbon group; C, carbonate group;Ma, minor-element subgroup A; Mb, minor-element subgrouP

Zr Nb Ag Cu Zn Ni Cr Mo V C0,t Cmin Ca Sr Y Yb Mn Pb

DC

Db

Da

DC

Db

DC

Db

Da

DC

Db

Ma

Ma

Ma

0

Ma

Ma

Ma

Ma

O

O

Ma

Ma

Ma

0

Ma

Mb

Ma

Ma

O

Ma

Mb

DC

Ma

O

Ma

Ma

O

Ma

0

Ma

Ma

O

Ma

O

Ma

O

O

C

o

o

c

c

c

c

c

c

c

c

c

c

c

Ma

C

c

c

Mb

Ma

Db

C

DC

I

C

Db

I

Db

I

I

I

Ma

C

I

I

Da

I

Db

element group. Further analysis of the correlation matrix, using three 

factors, indicates that the detrital group and the minor-element group 

can each be divided into three possible subgroups. The detrital subgroups are subgroup A, containing titanium, boron, sodium, vanadium, 

and possibly aluminum; subgroup B, containing potassium, chromium, gallium, scandium, and zirconium; and subgroup C, which is not

 distinguishable in figure 6, containing iron and magnesium. The minorelement subgroups are subgroup A, consisting of barium, cobalt, lanthanum, and ytterbium; subgroup B, consisting of nickel, selenium, 

sulfur, yttrium, and zinc; and subgroup C, which is not shown in figure 6, consisting of arsenic, lead, and part of the molybdenum. The

 carbonate group includes mineral carbon, calcium, strontium, manganese, and possibly organic carbon and part of the molybdenum. The 

epigenetic group consists of copper and silver. Although copper and, 

silver occur as sulfides in the epigenetically mineralized samples, sulfur appears to be associated primarily with inversely related minorelement subgroup B, which may include some syngenetic sulfide 

minerals.

OIL SHALE FROM THE GREEN RIVER FORMATION OF COLORADO

ELEMENT ABUNDANCE

The oil shale from the Green Eiver Formation of Colorado (set 17) 

is mainly a fine-grained marlstone (Bradley, 1964, p. A19) that contains unusually large amounts of solid organic matter and only minor 

amounts of detrital minerals. In most of the samples, carbonate 

minerals plus organic matter (kerogen) compose more than half the 

rock; the rest of the rock consists of quartz, analcime, mica, plagioclase, and pyrrhotite or pyrite, most of which were probably chemically or biologically precipitated. Analyses of the oil-shale samples 

show that silicon is greater than 10 percent in all 29 samples. Calcium 

is reported as greater than 10 percent in 28 samples, the one exception
A34 CONTRIBUTIONS TO GEOCHEMISTRY

being a sample which is mostly analcime and came from the Mahogany 

marker bed. The presence of 8.2 percent oil and 1.9 percent gas at the 

median level indicates that organic matter is the next most abundant 

constituent, followed by aluminum, magnesium, sodium, potassium, 

and iron (5, 3, 3, 2, and 1.5 percent, respectively, at the medians). 

Such minor elements as titanium and zirconium, which are characteristic of the detrital fraction in most black shales, are much less abundant in the Green Eiver oil shale than in most black shales and only 

slightly more abundant than in typical limestones. Of all the minor 

elements detected, only boron, barium, and strontium tend to be enriched in the oil shale. Even boron is not abundant in very many 

samples, although boron minerals from the saline facies of the Green 

Eiver Formation in the central Piceance Creek basin have been identified (E. J. Hite, oral commun., 1966). Elements such as molybdenum,, 

vanadium, chromium, copper, nickel, and silver, which commonly 

occur with organic matter and are locally enriched in some black 

shales, are not enriched in these oil-shale samples. Perhaps they have 

become uniformly dispersed throughout the oil shale where so much 

organic matter exists, or were dispersed by connate brines during 

consolidation of the oil shale.

ELEMENT ASSOCIATIONS

The Green Eiver oil-shale samples were submitted for Fisher assay, 

which yielded data on the percent oil, water, gas, and ash at 900°C. 

These data were included in the correlation and factor analysis along 

with the six-step spectrographic analysis in place of the usual analyses 

for forms of carbon. The results, using data from Fisher assay, can be 

interpreted in much the same terms as the data from carbon analyses 

for the other sample sets. Four principal element groupings are 

evident on the vector diagram (fig. 7) : (1) a detrital group that includes aluminum, gallium, zirconium, and ash, (2) a group that is 

probably composed largely of authigenic minerals, including carbonates, sulfides, and clay minerals, and includes potassium, iron, boron, 

manganese, titanium, cobalt, scandium, chromium, magnesium, nickel, 

strontium, copper, vanadium, and barium, (3) a group that shows an 

inverse relation to the detrital group, includes oil and gas and probably 

part of the molybdenum, and is thought to be equivalent to the organic 

carbon group of some other black-shale sample sets, and (4) a final 

group, sodium and water, which has an inverse relation to the authigenic mineral group. The analysis for water in the final group includes 

both free water and water from hydrous minerals, which makes interpretation of the group equivocal.
BLACK SHALES AND ASSOCIATED BOCKS A35

UPPER CRETACEOUS SHALES OF KANSAS

ELEMENT ABUNDANCE

The Upper Cretaceous shales of Kansas (set 18) range in lithology 

from detrital claystones that contain scattered small phosphate or 

carbonate concretions and moderately large amounts of organic matter, in the Sharon Springs Member of the Pierre Shale, to argillaceous 

limestone that contains large amounts of carbonate minerals, some 

detrital mineral matter, and relatively little organic matter in the 

Mobrara Formation. The 44 samples of Sharon Springs drill cuttings, 

the outcrop sample of dark-gray shale, and three of the 13 samples of 

Mobrara contain more than 10 percent silicon, whereas all the Niobrara 

samples and only two of the Sharon Springs samples, including the 

phosphatic nodule, contain more than 10 percent calcium. Alummum 

is reported to be greater than 10 percent in 18 samples of the Sharon 

Springs but is less than 10 percent in all the Niobrara samples. Of the 

total 59 samples, 38 contain 5 percent or more total carbon, but of these 

only 10, including nine from the Niobrara, contain 5 percent or more 

mineral carbon, and only six from the Sharon Springs Member contain 

5 percent or more organic carbon. Iron, magnesium, potassium, and 

sodium are all present in amounts of at least 1 percent but less than 

5 percent at the median level. The median concentration of most of 

the minor elements is close to the average for black shales, but a few 

may be described as enriched at the 95th-percentile level. These include 

boron, gallium, strontium, and possibly barium and copper.

ELEMENT ASSOCIATIONS

Four principal groups of elements can be recognized in the twofactor vector analysis (fig. 8) of the correlation matrix for the Upper 

Cretaceous shales of Kansas. These groupings were verified by a threefactor analysis of the same data. Titanium, boron, aluminum, zirconium, gallium, lead, and possibly potassium and equivalent uranium 

form one group, detrital subgroup A. Detrital subgroup B includesthe elements in the adjacent segment and consists of sodium, lanthanum, scandium, yttrium, ytterbium, copper, and possibly chromium,, 

niobium, manganese, and barium. Iron, magnesium, and zinc form 

detrital subgroup C on the opposite side of subgroup A (fig. 8). Anorganic-matter group, adjacent to detrital subgroup C but unrelated 

to detrital subgroup B, includes organic carbon, molybdenum, cobalt,., 

and nickel. A carbonate group including mineral carbon, calcium, and 

strontium is inversely related to detrital subgroup A. Chromium and. 

niobium, although clearly detrital, appear to have associations with 

both detrital subgroups A and.B. The distributions of barium and. 

manganese, however, appear to be largely independent of each other
A36 CONTRIBUTIONS TO GEOCHEMISTRY,

and only in part associated with detrital subgroup B, with which they 

are listed. Vanadium is similarly independent, but is partly associated 

with the carbonate group.

UPPER CRETACEOUS SHALES OF TEXAS 

ELEMENT ABUNDANCE

The 28 samples of Upper Cretaceous shales of Texas (set 19) are 

fine-grained carbonate-rich detrital rocks, chiefly claystone and marl, 

and contain low to moderate amounts of organic matter. Of the 28 

samples, 25 contain greater than 10 percent calcium, 16 contain greater 

than 10 percent silicon, and eight contain greater than 10 percent 

aluminum. The median contents are iron and potassium, 2 percent; 

sodium, 0.7 percent; magnesium, 0.5 percent; titanium, 0.1 percent; 

and manganese, 0.02 percent. The median total carbon content is 10.7 

percent; total carbon content at the 95th percentile is 12.6 percent. As 

would be expected from the high calcium content, mineral carbon 

makes up the major part of total carbon; at the median level, mineral

 carbon is 7.91 percent, and at the 95th percentile, 11.1 percent. The 

median of organic carbon is 2.8 percent, and at the 95th percentile it is 

4.5 percent. Of the minor elements, boron, barium, gallium, and 

strontium are enridhed at the 95th-percentile level. Silver was not 

detected in any of the samples, and beryllium was detected in only 

two. The other minor elements occur in near-average amounts.

ELEMENT ASSOCIATIONS

Three groups of elements can be recognized on the two-factor diagram (fig. 9): (1) a detrital group composed of silicon, aluminum, 

titanium, zirconium, potassium, copper, sodium, scandium, cobalt, 

organic carbon, iron, chromium, vanadium, nickel, yttrium, barium, 

lanthanum, ytterbium, molybdenum, and possibly magnesium, (2) a 

carbonate group composed of mineral carbon, calcium, and strontium, 

and (3) a minor-element group composed of boron, lead, and gallium. 

Manganese and equivalent uranium show no relation to each other or 

to any of the groups listed. Because so many elements occurred in the 

detrital group, a three-factor analysis was also run. Five closely related 

detrital subgroups were distinguished: subgroup A, silicon, aluminum, copper, and zirconium; subgroup B, potassium, titanium, organic

 carbon, sodium, and scandium; subgroup C, vanadium, nickel, and 

molybdenum; subgroup D, yttrium, lanthanum, ytterbium, and 

barium; and subgroup E, iron, cobalt, chromium and magnesium. 

Subgroups A, B, and C appear to be closely interrelated, and subgroups D and E are closely interrelated. The carbonate group is in-
BLACK SHALES AND ASSOCIATED ROCKS A37

versely related to the minor-element group and is not related to the 

detrital group. Organic carbon acts like a detrital element in this setr, 

suggesting that most of the organic carbon was land derived.

UPPER MISSISSIPPIAN SHALES OF WESTERN WYOMING

ELEMENT ABUNDANCE

The Upper Mississippian shales of western Wyoming (set 20) are 

predominantly detrital rocks, chiefly claystones and siltstones that contain only minor amounts of organic matter and almost no carbonate 

minerals. Secondary sulfates occur on joint surfaces. Of the major 

elements in these black shales, the median contents of silicon, aluminum, and potassium are 5 percent or greater, those of iron and calcium, 

are 1-5 percent, and those of carbon, magnesium, and titanium areslightly less than 1 percent. The median content of titanium (0.7 percent) is as high as the highest 95th percentile of the other black-shalesample sets. The minor-element content of these samples is very similar to that of average black-shale samples, with two exceptions: boron 

and zirconium. The median boron content of 0.03 percent is higher 

than that of most black-shale samples, and the median zirconium 

content of 0.05 percent is several times higher than that of most blackshale samples. Four of the 14 samples were reported to contain 0.07 

percent zirconium, which is about three times the amount listed by 

Turekian and Wedepohl (1961) as the average for sandstone.

ELEMENT ASSOCIATIONS

The element groupings for the black shales of Late Mississippian 

age from western Wyoming are scattered on the two-factor vector 

diagram (fig. 10), but six groups can be distinguished from threefactor analysis of the correlation matrix. Detrital subgroup A consists 

of potassium, boron, equivalent uranium, sodium, calcium, vanadium,, 

and chromram. Though largely independent, titanium, niobium, and 

zirconium are designated detrital subgroup B. A group that is composed of nickel, copper, manganese, and cobalt and that is inversely 

related to detrital subgroup A is designated minor-element subgroupA. Iron, lead, and molybdenum are unrelated to either detrital subgroup A or minor-element subgroup A and are designated minorelement subgroup B. Selenium is independent except for a correlation 

with lead. Minor-element subgroup C consists of lanthanum, strontium,, 

and barium and is closely related to minor-element subgroup B. 

Organic carbon and magnesium, which fall between detrital subgroup 

A and minor-element subgroup C, form the organic-matter group. Thedispersed nature of the element groupings in this set is due at least 

in part to the small range in values shown by analysis of the samples
A38 CONTRIBUTIONS TO GEOCHEMISTRY

ASHED SHALE FROM MINNELTJSA FORMATION OF SOUTH DAKOTA

AND WYOMING

ELEMENT ABUNDANCE

The carbonaceous rocks from the Minnelusa Formation of South 

Dakota and Wyoming (set 21) include lithologies ranging from black

 carbonaceous siltstone or claystone with abundant organic matter and 

little or no carbonate minerals to black dolomitic limestone with relatively few detrital minerals and little organic matter. The samples 

were ashed prior to spectrographic analysis because of the high organic 

content in some. Ash content ranged from 67 to 97 percent. Most of the 

reported major elements show a wide range in content. For example, 

the silicon content of the ashed samples ranges from 0.3 percent to 

greater than 10 percent; 14 of the 22 samples analyzed, however, contain more than 10 percent silicon. The median content of aluminum is 

7 percent, and 10 samples contain more than 10 percent. Calcium content is greater than 10 percent in eight samples, and magnesium is 

greater than 10 percent in seven, but the medians for calcium and 

magnesium are only 2 percent each. In this set, potassium and sodium 

were not looked for, and the median content of iron is 2 percent. 

Fourteen samples contain 5 percent or more total carbon, and either 

organic carbon or mineral carbon is generally predominant. About 

one-third of the samples are rich in carbonate minerals, chiefly 

dolomite, as is indicated by their high magnesium content. Some of the 

minor elements are especially abundant in these black-shale and dolomite samples from the Minnelusa Formation. Unusually large 

amounts of molybdenum, vanadium, lead, and strontium occur, and

-cobalt, copper, lanthanum, silver, beryllium, chromium, and nickel 

are also enriched. These samples were all collected from weathered 

surface exposures, and possibly some of the more mobile minor elements have been enriched at the surface; whether all the high values 

can be thus explained is not known.

ELEMENT ASSOCIATIONS

In interpreting the element associations in set 21, the ashing prior 

to spectrographic analysis must be considered. Even though the ash 

^content of the samples is high (average 88.7 percent), there tends to 

be some concentration of the elements in the ash. This concentration, 

however, is probably not great enough to significantly affect the 

^coefficients of correlation. On the vector diagram (fig. 11), the elements 

fall into three main groups: (1) a detrital group composed of 

.aluminum, silicon, titanium, chromium, vanadium, iron, strontium,
BLACK SHALES AND ASSOCIATED ROCKS A39

barium, lanthanum, yttrium, and beryllium, (2) an organic-matter 

.group, in the same quadrant as the detrital group, composed of 

organic carbon plus molybdenum, silver, lead, copper, nickel, and 

cobalt, and (3) a carbonate mineral group, inverse to the other two 

groups, composed of mineral carbon plus calcium, magnesium, and 

manganese. Ash is shown as a separate segment inverse to the organicmatter group. The association of strontium with the detrital group 

and its inverse relation to the carbonate group are unique to this set. 

Strontium shows its strongest correlation with vanadium, chromium, 

nickel, titanium, and aluminum.

SUMMARY

The nine sample sets of black shale and associated rocks described 

in this report are very diverse (table 1): They range in age from 

Precambrian to Eocene, their environments of deposition range from 

eugeosynclinal to shallow carbonate lake, and rocks sampled range 

from unweathered core to weathered outcrop; thus the geochemical 

distribution of elements also varies widely. Nevertheless, general behavior patterns for certain elements can be interpreted from the data.

The range in concentration of the elements detected in these nine 

sample sets of black shale and associated rocks is summarized in" 

figure 12. The range and median of the set medians are shown for 

 each element by a bar with open circles. Each of these is directly underlain by a second bar with solid circles that shows the range and median 

of the 95th percentiles for the nine sets. The minor elements are shown 

on the left in order of generally decreasing abundance, beginning with 

the most abundant minor element, vanadium. The major elements are 

plotted, also in order of decreasing abundance, on the right side of 

figure 12. For three of the major elements aluminum, iron, and 

potassium and eight of the minor elements boron, cobalt, copper, 

manganese, nickel, scandium, yttrium, and zirconium the lowest 95th 

percentile is equal to or greater than the median of the medians. This 

is not a geochemically cohesive group, for although it includes many 

elements that are commonly in the detrital group, it also includes 

several elements that are among the most mobile.

The elements that occur primarily with the detrital fraction show 

relatively small range in content within a single sample set, as shown 

in table 3, and include silicon, aluminum, potassium, titanium, and the 

minor elements boron, gallium, scandium, and zirconium. For most of 

these elements the concentration at the 95th percentile is commonly 

no more than one or "two spectrographic steps greater than the median, 

and occasionally the median and the 95th percentile cannot be distinguished with available data; the range in concentration between sample
A40 CONTRIBUTIONS TO GEOCHEMISTRY

.£

111 >k

EXPLANATION Highest 50th Lowest 

Median range

50th Highest Lowest 5th-percentile rang<

 a

mic-absorption anal

A

sample Mineralized 

0> o

4)

O

9

c

S

O

O O /

**

0 0

! 

 r ~

o

o

o

4) 4)

O

'

O4 »

Q

i.

0 e

-<

j 00 <>z

1 0

. Q.. , y Q

O4> 1 J-4*

<k T

i r

4>

Co c

CO

0 z

UJ

^

I

LJL!

cc

O

z

5

4

«

5

)

t 

Limits ofdetection

4

9

»( i

N

-4 

4

[

CO

0^ «

^ S

5 9 T S

oc> 8

4

1

<

5

4

T1 -** o*

i 9

o c

o

4>

c

o

>

Ott 4>

4»

I "^

o tt

» - J 

t.W ' ' y" ^ J"

6 ° 9' o "^

^Oli^ °

0 I

4

3

C4

Z

4

)

<

w »9«

i

»

D

4

^«

iL

»

>

>

i

I

4

9

(

t,

4

34

f

C

(

- 

»

>

)(

)4

4

)-

o

?

1

^4C

>

1

>

4

P 

£

n<y*

Ol

O ^*

1

I

1

%

^

associated androci 

V

"es 

f)L/i

44

u

5

2

«-+

o

uC

1u Jl

0)

a.

aoi

CO

0

=}

 I-*

a

 S

 J2

4^

S3 a>

3

fSJ "3

"«

u

1

ij

^

bJQ

a 

S

§

+3

S -i_>

Oa>

o

a

»

!=> o

fo
BLACK SHALES AND ASSOCIATED ROCKS A41

sets is likewise small, as shown in figure 12. The highest 95th percentile 

is not significantly greater than the highest median for titanium, 

potassium, boron, and scandium. Silicon content was not shown in 

figure 12 because it is reported as greater than 10 percent in most of 

the samples.

Calcium and strontium are almost always associated with the carbonate fraction of the sample sets. A large range in their values in an 

individual sample set generally reflects a large range in carbonate 

content due to lithologic differences between the samples and does not 

reflect element mobility, as described in the following paragraphs. 

An exception to this general pattern of association of strontium with 

the carbonate fraction was found in the Minnelusa Formation (set 21), 

where strontium is unusually abundant and is associated with the 

detrital fraction. Its correlation with barium and iron suggests that 

strontium may occur as a sulfate and that it may have been epigenetically enriched. Manganese is associated with the carbonate fraction in 

the black shale from the Tacket Formation of Kansas (set 14), the 

Nonesuch Shale (set 16), and the Minnelusa Formatiton (set 21); 

magnesium is associated with the carbonate fraction in set 21 and in 

the Tyler Formation of central Montana (subset 15D). All four of 

these elements show a wide range in concentration between sample sets 

(fig. 12).

Minor elements associated with the organic matter of these sample 

sets commonly differ more than three spectrographic steps between the 

median and the 95th-percentile levels of abundance. These elements 

have greater mobility than do those that occur primarily with the 

detrital fraction. To whatever extent this mobility is real, it probably 

occurs during deposition, consolidation, and much later in the history 

of the rock, possibly even during weathering. The result during each 

 episode is a local concentration of the elements. Content of these elements commonly varies directly with the amount of organic matter. 

Because organic matter is rarely a major constituent of these samples, 

the minor-element concentration is thought to be more a function of 

local physical and chemical controls in combination with the element 

mobility than of variations in lithology. The suite of chemically mobile elements varies from one sample set to another, but some of the 

same elements occur repeatedly. Chemically mobile elements in the 

black shale of the Tacket Formation of Kansas (set 14) include chromium, molybdenum, silver vanadium, and yittrium; those associated 

with the organic fraction of the Heath Formation in central Montana 

(subset 15C) include molybdenum, silver, vanadium, zinc, and possibly 

copper; and those having a similar association in the Minnelusa Formation of South Dakota and Wyoming (set 21) include lead, molyb-
A42 CONTRIBUTIONS TO GEOCHEMISTRY

denum, nickel, silver, and probably copper. These same mobile elements 

are evident in figure 12 by their extended ranges in concentration, 

especially between the highest median and the highest 95th percentile.

The greatest enrichment of minor elements among these nine sample 

sets occurs in the Nonesuch Shale of Michigan where copper and silver 

show no association with any of the major rock constituents. This 

occurrence is thought to reflect a definite secondary stage of mineralization and a distribution of the secondary elements that is not chemically controlled by variations within the rock unit.

Any search for "metal-rich" black-shale deposits of economic tenor 

should take into consideration the foregoing classification of the elements by association with major rock constituents. Elements that are 

sufficiently mobile to form epigenetic deposits or to be concentrated 

in association with organic matter are probably also those that possibly could occur in concentrations sufficiently high to form ore-grade 

deposits. Of the four sample sets that show a tendency to concentrate 

mobile elements, only the Nonesuch Shale of Michigan is known to 

contain commercially exploitable mineral deposits. The Heath Formation of central Montana, the Tacket Formation of Kansas, and the 

Minnelusa Formation of South Dakota and Wyoming may be worthy 

of additional study in the search for large low-grade deposits of mobile 

elements.

REFERENCES CITED

Bradley, W. H., 1964, Geology of Green River Formation and associated Eocene 

rocks in southwestern Wyoming and adjacent parts of Colorado and Utah: 

U.S. Geol. Survey Prof. Paper 496-A, 86 p. [1965].

Chayes, Felix, 1960, On correlation between variables of constant sum: Jour. 

Geophys. Research, v. 65, no. 12, p. 4185-4193.

Davidson, D. F., and Lakin, H. W., 1961, Metal content of some black shales of 

the western United States, in Short papers in the geologic and hydrologic 

sciences: U.S. Geol. Survey Prof. Paper 424-C, p. C329-C331.

Duncan, D. C., compiler, 1953, Reconnaissance investigations for uranium in 

black shale deposits of the Western States during 1951 and 1952: U.S. GeoL 

Survey TEI-381, 89 p., issued by U.S. Atomic Energy Comm. Tech. Inf. 

Service, Oak Ridge, Tenn.

Eargle, D. H., and Hollingsworth, J. S., 1957, Radioactivity and uranium content of Eagle Ford rocks of Texas: U.S. Geol. Survey TEI-700, p. 172-174, 

issued by U.S. Atomic Energy Comm. Tech. Inf. Service, Oak Ridge, Tenn.

Goldstein, August, Jr., and Hendricks, T. A., 1953, Siliceous sediments of Ouachita 

facies in Oklahoma: Geol. Soc. America Bull., v. 64, no. 4, p. 421-441.

Griffiths, J. C., 1966, A genetic model for the interpretive petrology of detrital 

sediments: Jour. Geology, v. 74, no. 5, pt. 2, p. 655-672.

Harman, H. H., 1960, Modern factor analysis: Chicago Univ. Press, 469 p.

Imbrie, John, and VanAndel, T. H., 1964, Vector analysis of heavy-mineral data: 

Geol. Soc. America Bull., v. 75, no. 11, p. 1131-1156.
BLACK SHALES AND ASSOCIATED ROCKS A43

Jewett, J. M., Emery, P. A., and Hatcher, D. A., 1965. The Pleasanton Group

(Upper Pennsylvania!!) in Kansas: Kansas Geol. Survey Bull. 175, pt. 4,11 p.

Maughan, E. K., and Roberts, A. B., 1967, Big Snowy and Amsden Groups and the

Mississippian-Pennsylvanian boundary in Montana; U.S. Geol. Survey Prof.

Paper 554-B, 27 p. 

Miesch, A. T., Chao, B. C. T., and Cuttitta, Frank, 1966, Multivariate analysis of

geochemical data on tebtites: Jour. Geology, v. 74, no. 5, pt. 2, p. 673-691. 

Myers, A. T., Havens, R. G., and Dunton, P. J., 1961, A spectrochemical method

for the semiquantitative analysis of rocks, minerals, and ores: U.S. Geol.

Survey Bull. 1084-1, p. 207-229. 

Sando, W. J., and Dutro, J. T., Jr., 1960, Stratigraphy and coral zonation of

the Madison Group and Brazer Dolomite in northeastern Utah, western

Wyoming, and southwestern Montana, in Overthrust belt of southwestern

Wyoming and adjacent areas: Wyoming Geol. Assoc. Guidebook, 15th Ann.

Meld Conf., 1960, p. 117-126. 

Stanfield, K. B., and Frost, I. C., 1949, Method of assaying oil shale by a modified

Fischer retort: U.S. Bur. Mines Rept. Inv. 4477 (revision of Rept. Inv. 3977),

13 p. 

Tourtelot, H. A., Huffman, Claude, Jr., and Rader, L. F., 1964, Cadmium in

samples of the Pier re Shale and some equivalent stratigraphic units, Great

Plains region, in Short papers in geology and hydrology: U.S. Geol. Survey

Prof. Paper 475-D, p. D73-D78. 

Turekian, K. K., and Wedepohl, K. H., 1961, Distribution of the elements in some

major units of the Earth's crust: Geol. Soc. America Bull., v. 72, no. 2,

p. 175-191. 

Vine, J. D., 1966, Element distribution in some shelf and eugeosynclinal black

shales: U.S. Geol. Survey Bull. 1214-E, 31 p. 

 1969, Element distribution in some Paleozoic black shales and associated

rocks: U.S. Geol. Survey Bull. 1214-G, 32 p. 

Vine, J. D., Tourtelot, E. B., and Keith, J. R., 1969, Element distribution in

some trough and platform types of black shale and associated rocks: U.S.

Geol. Survey Bull. 1214-H, 38 p. 

Waldron, F. R., Donnell, J. R., and Wright, J. C., 1951, Geology of Debeque

oil-shale area, Garfield and Mesa Counties, Colorado: U.S. Geol. Survey Oil

and Gas Inv. Map OM-114,2 sheets, with sections and text 

Wanless, H. R., Belknap, R. L., and Foster, H. L., 1955, Paleozoic and Mesozoic

rocks of Gros Ventre, Teton, Hoback, and Snake River ranges, Wyoming:

Geol. Soc. America Mem. 63,90 p. 

White, W. S., and Wright, J. C., 1954, The White Pine copper deposit, Ontonagon

County, Michigan: Econ. Geology, v. 49, no. 7, p. 675-716.

U.S. GOVERN WEST PRINTING OFFICE. 1969