Chemical Composition of Sedimentary Rocks: Limestone in Colorado and Kansas, Schemes and Mind Maps of Communication

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Chemical Composition of

Sedimentary Rocks in

Colorado, Kansas, Montana

Nebraska, North Dakota

South Dakota, and Wyoming

GEOLOGICAL SURVEY PROFESSIONAL PAPER 561

Chemical Composition of

Sedimentary Rocks in

Colorado, Kansas, Montana

Nebraska, North Dakota

South Dakota, and Wyoming

Compiled by

THELMA P. HILL, MARIAN A. WERNER, and M. JULIA HORTON

With an introduction by

WILLIAM W. RUBEY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 561

A compilation of 2,842 analyses

published before 1958

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1967

CONTENTS

Abstract.---________________________......... Introduction, by W. W. Rubey_______________________ Project background.____________________________ Analyses selection_____________________________ Arrangement of analyses_______________________ Classification of sedimentary rocks________________ Groups.___________________________________ Categories.________________________________ Special-rock category______________________ Discussion.____________________________________ Acknowledgments _ ______________________________ General information_______________________________ Criteria for inclusion of analyses._________________ Types of samples.__________________________ Analyses of samples.________________________ Explanation of terms and arrangement of tables____

Page Codes for permanent numbers assigned to analyses __ 195 Graphical summaries.-________------------------- 196 Areal distribution______--------------------- 196 Distribution by composition-...._________________ 196 Cumulative frequency curves ____________----- 217 References cited___________________-------------- 225 Indexes __________________---------------_------- 233 Stratigraphic names _____-_________------------ 234 Analyses by geologic age ______________________ 237 Actual and possible use.----------.-------------- 238 Chemical and spectrographic analyses for minor con- stituents, compounds, and radicals (oxides reported as elements) in rocks of the common- and mixed- rock categories; reported in only a few analyses. _ 239 Chemical and spectrographic analyses for con- stituents, compounds, and radicals (oxides reported as elements) in rocks of the special-rock category. _ 241

ILLUSTRATIONS

[Plates are in pocket]

PLATES 1-9. Maps showing sample localities

1. Groups A and C, common- and mixed-rock categories.
2. Group B, clay and bentonite, shale, and volcanic ash, common- and mixed-rock categories.
3. Groups D and E, common- and mixed-rock categories.
4. Groups F! and F2, limestone, dolomite, and chalk, common- and mixed-rock categories.
5. Sulfate-, phosphate-, and chloride-bearing rocks, special-rock category.
6. Rocks for which an actual or possible use is reported, common- and mixed-rock categories.
7. Rocks of Precambrian and Paleozoic ages.
8. Rocks of Triassic, Jurassic, and Cretaceous ages.
9. Rocks of Tertiary and Quaternary ages.
10. Diagrams showing distribution among compositional groups of analyses of various types of rock from the Northern Rocky Mountains and Great Plains region. 11-14. Diagrams showing distribution among compositional groups of analyses of materials by age
11. Paleozoic.
12. Mesozoic.
13. Tertiary.
14. Quaternary. Page FIGURE 1. Composition of sedimentary rocks showing the seven fields into which the chemical analyses are grouped. _ 3
15. Tetrahedron illustrating three categories of rock compositions____________________-------_----------- 5 3-9. Diagrams showing distribution of analyses of rocks by group content
16. Group A, content of more than 75 percent uncombined silica_________-_------------------- 197
17. Group B, content of uncombined silica and clay, each less than 75 percent; uncombined silica and clay, each more than carbonate...____________________------_--------------------- 198
18. Group C, content of uncombined silica and carbonate, each less than 75 percent; uncombined silica and carbonate, each more than clay________--_______-----------------_---------- 199
19. Group D, content of clay more than 75 percent. ____-________---------------_--------------- 200
20. Group E, content of clay and carbonate, each less than 75 percent; clay and carbonate, each more than uncombined silica._______________________________-------------------------- 201
21. Group FI, carbonate content from 75 to 90 percent..-i------------------------------------ 202
22. Group F2, carbonate content more than 90 percent._________________________---_----------- 203 ill

IV CONTENTS

Page

FIGURE 10-16. Cumulative frequency curves showing the proportion of all analyses in the common- and mixed-rock cate-

gories that contain up to (but not more than) the indicated percentage of various constituents

10. Group A_______-.______-___________ _ _ _ _ .__ 218
11. Group B____----______--.---____--______---___________________ 219
12. Group C____.--------------_____-_-___________---________________ 220
13. Group D________________________________________________________ 221
14. Group E______-_______------------______----__-__________________________ 222
15. Group FI_______________________________-----____-______---__-__________ 223
16. Group F2 .---------------------------------------------------------__________ 224

TABLES

Page

TABLE 1. Analyses of samples from Colorado, Kansas, Montana, Nebraska, South Dakota, and Wyoming, containing

more than 75 percent uncombined silica (group A), common- and mixed-rock categories._____________ 10 2-6. Analyses of samples, by State, containing uncombined silica and clay each less than 75 percent; uncombined silica and clay each more than carbonate (group B), common- and mixed-rock categories:

2. Colorado.__________________________________________________----------______ 16
3. Kansas__________________________________________-__________--------------_--- 22
4. Montana and Nebraska._____-_______________-____________-------------------_----- 42
5. North Dakota___________________________________________________ 44
6. South Dakota and Wyoming..___________________--_________________________-----------_ 52
7. Analyses of samples from Colorado, Kansas, Montana, North Dakota, and Wyoming, containing uncombined silica and carbonate each less than 75 percent; uncombined silica and carbonate each more than clay (group C), common- and mixed-rock categories_________________________------------------------ 64 8-11. Analyses of samples, by State, containing more than 75 percent clay (group D), common- and mixed-rock categories:
8. Colorado.______________________________________________________________________________ 71
9. Kansas_______________________________________________________________________________ 74
10. Montana.________________________________________________________________________ 80
11. North Dakota, South Dakota, and Wyoming.________________________-----------------_ 82
12. Analyses of samples from Colorado, Kansas, Montana, Nebraska, North Dakota, South Dakota, and Wyo- ming, containing clay and carbonate, each less than 75 percent; clay and carbonate, each more than uncombined silica (group E), common- and mixed-rock categories.________________________________ 88
13. Analyses of samples from Colorado and Kansas containing 75-90 percent carbonate (group FI), common-rock category ___________________________________________________________________________________ 96
14. Analyses of samples from Montana, Nebraska, North Dakota, South Dakota, and Wyoming, containing 75-90 percent carbonate (group Fj), common- and mixed-rock categories._________________________ 108 15-18. Analyses of samples, by States, containing more than 90 percent carbonate (group F2), common-rock category:
15. Colorado..__________________________________________________ 114
16. Kansas________________________________________________________ 119
17. Montana, Nebraska, and North Dakota-_________________--____---------------------_ 146
18. South Dakota and Wyoming____________________________________________________________ 152 19-27. Analyses of samples Hk, Ha, Na, G, S, P, Fe, Mn, and M, special-rock category, by States:
19. Clays in which (2.178XA12O3)+H2O (however determined) is 50 percent or more (group Hk), Colorado, Kansas, and South Dakota._______________________-------------- 160
20. Clays in which Al2O3 + SiO2 + H2 O (however determined) is 50 percent or more (group Ha), Kansas, Montana, South Dakota, and Wyoming________________________________________________ 163 2li 50 percent or more of NaCl (group Na), Kansas...________________________________________ 164
21. 50 percent or more gypsum, gypsite, or anhydrite (group G), Colorado, Kansas, Montana, South Dakota, and Wyoming____________________________________________.__________________ 167
22. 50 percent or more miscellaneous sulfate-, carbonate-, and nitrate-bearing material (group S), Colo- rado, Montana, Nebraska, North Dakota, and Wyoming.________________________________ 170
23. Phosphate rock or nodules, containing 21.1 percent or more P2 O5 (group P), Kansas, Montana, and Wyoming.________________________________________________________________________ 176
24. Iron-rich rocks, most of which contain 50 percent or more of ferrous oxide or ferric oxide (group Fe), Colorado, Montana, South Dakota, and Wyoming_______________________________________ 184
25. Manganese-bearing rocks and nodules (group Mn), North Dakota, South Dakota, and Wyoming._ 186
26. Coal and coal ash, oil shale and oil shale ash, barites, nodules, and granodiorite and its weathered products, miscellaneous group (group M), Colorado, Nebraska, North Dakota, and Wyoming._ 188

CHEMICAL COMPOSITION OF SEDIMENTARY ROCKS IN COLORADO, KANSAS, MONTANA

NEBRASKA, NORTH DAKOTA, SOUTH DAKOTA, AND WYOMING

Compiled by THELMA P. HILL, MARIAN A. WERNER, and M. JULIA HORTON

ABSTRACT

The compilation of published chemical analyses of sedimen- tary rocks of the United States was undertaken by the U.S. Geological Survey in 1952 to make available scattered data that are needed for a wide range of economic and scientific uses. About 20,000-25,000 chemical analyses of sedimentary rocks in the United States have been published. This report brings together about 2,850 of these analyses from the Northern Rocky Mountains and the Great Plains region. The samples are arranged by three successive criteria: (a) general lithologic character; (b) locality; and (c) geologic age, formation, and relative stratigraphic order. Both a stratigraphic index of the geologic formations represented by the analyses and an index of commercial uses are provided. The analyses are classified into groups and into categories. The groups (A through F2 ) are based on a modified form of the system proposed by Brian Mason in 1952 in which the relative abundance of the three major components of sedi- mentary rocks is considered. The components are (a) uncom- bined silica, (b) clay (R2O3 -3SiCVttH2C)), and (c) calcium- magnesium carbonate. The common- and mixed-rock categories are based on the degree of admixture of these three major components with other components, such as sulfate minerals, phosphate, and iron oxide. In most of the analyses, the three major components amount to 90 percent or more, and these analyses were placed in a "common-rock" category. In a few analyses, however, the three major components make up only 50-90 percent of the rock, and the analyses were placed in a "mixed-rock" category. Analyses in which the three major com- ponents amount to less than 50 percent were placed in an arbitrarily lettered group according to the admixed substance that makes up most of the rock analyzed. These analyses (con- taining less than 50 percent of the three major components) were also called "special-rock" category. Maps show distribution of sample localities by States, and triangular diagrams show the lithologic character, classification group, and geologic age. The many analyses assembled here may not adequately re- present the geochemical nature of the various rock types and formations of the region because the analyzed samples were chosen mainly on the basis of possible economic use of the rocks sampled, rather than at random. Maps showing the areal distribution of localities from which the analyzed samples were taken indicate that many of the localities are in areas where, for economic or other reasons, special problems attracted inter- est. Sampling biases are of several kinds, and they tend to cancel one another. Several generalized but noteworthy relationships became apparent from the compilation. Most of the analyzed rocks tended to be fairly simple in composition mainly two-component mixtures of the three major components (uncombined silica, the clay molecule, and calcium-magnesium carbonate) or a

mixture of the three major components and a fourth component, such as phosphate, gypsum, salt, or iron oxide. A comparison of the number of analyses assembled here with rough estimates of the relative thickness of rocks of different lithologic types and geologic ages showed that the avail- able analyses were far from equally representative of the sedi- mentary rock column of the region. Possibly, future analytical work will correct the worst deficiencies of the existing data.

INTRODUCTION

By W. W. RUBEY

PROJECT BACKGROUND

The project of compiling published chemical analyses

of sedimentary rocks of the United States was under-

taken by the U.S. Geological Survey in 1952. Decision

to undertake the project came largely as an outgrowth

of suggestions made by a group of geochemists, geol-

ogists, geophysicists, and biologists who were called

together for a conference on May 27, 1950, by L. H.

Adams and M. A. Tuve, of the Carnegie Institution of

Washington. The conference dealt with the geochem-

ical problems of sedimentary rocks. The group pointed

out that a knowledge of the composition of sedimentary

rocks comparable to that of the composition of igneous

rocks, which had been available for several decades,

would be extremely helpful in many scientific fields.

As a result of this and other conferences on the sub-

ject, the National Eesearch Council in 1951 established

a committee, under the chairmanship of G. E.

Hutchinson, on the chemical composition of sediments.

The committee's purpose was to encourage individual

investigations which would lead to a better balanced

knowledge of the composition of sedimentary rocks.

As well as presenting the recommendation that ulti-

mately led to establishment of the project represented

by this report, the committee encouraged investigations

of deep-sea sediments and of Precambrian sedimentary

rocks, for available chemical information on both these

materials is also inadequate. Better knowledge of the

geochemistry of sedimentary rocks must, of course, de-

pend in part upon new chemical analyses, but a wise

choice of the rock types for which new analyses are

most needed would call for the systematic assemblage

of the vast amount of information that is now widely

COLORADO, KANSAS, MONTANA, NEBRASKA, NORTH DAKOTA, SOUTH DAKOTA, WYOMING

position are variously reported as chalk, limestone,

chalk-marl, marl, and shale. As a result, a system of

classification based solely on the lithologic terms used

by the original authors would cause the closely similar

rock types to fall into seemingly quite different cate-

gories. For purposes of the present compilation, a more

nearly uniform and objective system of classification

that depends primarily upon the chemical analyses

themselves was adopted. Such a system indicates the

relations of the three main components of sedimentary

rocks (sand, clay, and carbonate minerals) and the de-

gree of admixture of these major components with other

materials such as sulfate minerals, phosphate minerals,

and iron oxide. The relations of the three main compo-

nents are expressed in terms of groups. The degree

of admixture with other materials is expressed as

categories.

GROUPS

Much has been written during the past 50 years about

various systems of classification of igneous rocks; but

there is no uniform agreement as to the best all-purpose

system. In some ways, classification on the basis of

chemical composition is simpler for igneous rocks than

for sedimentary rocks, because the various types of ig-

neous rocks can be adequately characterized in terms of

a relatively small number of standard or normative

minerals that, at least in theory, crystallized together

under conditions of approximate chemical equilibria.

But many sedimentary rocks are made up largely of

fragmental materials grains of minerals formed in

environments totally different from that in which de-

trital-sediment accumulation occurred. Thus, there are

no known rules of consanguinity comparable to those

for igneous rocks (and possibly for many metamorphic

rocks) to govern the mineral assemblages in sedimen-

tary rocks. Furthermore, clay minerals are a major

constituent of many sedimentary rocks, and the miner-

alogy and chemical compositions of these minerals are

very complex. This complexity greatly handicaps

efforts to establish a rational basis for a chemical clas-

sification of detrital sediments.

A satisfactory system may someday be devised for

the classification of all sedimentary rocks in terms of a

few theoretical minerals that are arbitrarily defined on

the basis of chemical composition. Formulation of some

such system, in fact, may well be one of the scientific

uses of a comprehensive compilation of sedimentary

analyses. Because no such classification was available

at the time this compilation was made, some other basis

for the chemical classification of sedimentary rocks was

required.

Attempts to use several possible methods of classifi-

cation showed that a system similar to that used by

Si (Uncombined silica)

75 percent

75 percent

R2 03 -3Si02 -wH2 0

(Clay)

CaC03 +MgC (Carbonate)

FIGURE 1. Composition of sedimentary rocks showing the seven fields into which the chemical analyses are grouped.

Mason (1952, p. 130-131) combines, as effectively as

any other, the desirable elements of maximum simplicity

and geochemical significance. (See fig. 1.) The sys-

tem used here a modification of Mason's treats all

sedimentary rocks as if they were mixtures of three

ideal components: (a) quartz (uncombined silica), (b)

an arbitrarily defined clay molecule (B,2O3 -3SiO2 -

nH2O), and (c) total carbonate calculated as (CaCO

+ MgCO3 ). Actually, most sedimentary rocks can

only be approximately classified as being mixtures of

these three components. Silica is a major constituent

of all the commoner clay minerals, and as a result the

most abundant types of mudstones have chemical com-

positions that fall somewhere between the composition

of the two theoretical components uncombined silica

and R2O3 -3SiO2 -nH2O. Similarly, the analysis of a

clean well-sorted sandstone that includes significant

amounts of feldspar grains contains much A12O3, and it

thus appears in the system of classification used here as

a mixture of uncombined silica and R2O3 '3SiO2 'wH2O.

If the sand grains include many particles of calcic

plagioclase and of ferromagnesian minerals, the analy-

sis of the rock then shows significant amounts of A12O3,

Fe2O3, CaO, and MgO, as well as SiO2, and in the

classification system this sandstone may appear as a

mixture of all three components. Thus this composi-

tional diagram is only roughly analogous to the com-

mon sand-mud-lime diagram. Nevertheless, when these

qualifications are kept in mind, the three somewhat

hypothetical components of the diagram afford a useful

basis for classifying the chemical analyses of a great

many sedimentary rocks.

CHEMICAL COMPOSITION OF SEDIMENTARY BOCKS

Perhaps the conventionalized clay molecule (R2(V

3SiO2 - nH2O) used in this report is too simplified to

serve most effectively in this arbitrary classification.

The clay corner of the composition diagram would be

more useful if it represented not only R2O3, SiO2, and

H2O but also the alkalies, K2O and Na2O, and that

part of the MgO and CaO which is not found in car-

bonates. The difficulty, however, is that many pub-

lished analyses do not include the alkalies and CO2 but

are otherwise useful and should be included. The

classification system should also be capable of placing

in the same groups these analyses and similar ones in

which the alkalies and CO2 have been determined.

The three-component diagram becomes more useful

for classifying large numbers of analyses when it is

subdivided into several fields that correspond to differ-

ent mixtures of the three components. Convenient

groups are arbitrarily defined as follows:

A. Silica group________ Uncombined silica, more than 75 percent. B. Mixed silica and clay group. Uncombined silica and clay, each less than 75 percent; uncombined silica and clay, each more than carbonate. C. Mixed silica and carbonate Uncombined silica and car- group, bonate, each less than 75 percent; uncombined silica and carbonate, each more than clay. D. Clay group._________ Clay, more than 75 percent. E. Mixed clay and carbonate Clay and carbonate, each less group. than 75 percent; clay and carbonate, each more than uncombined silica. F. Carbonate group- ___ _ Carbonate, more than 75 per- cent. Fi (common carbonate)_ Carbonate from 75 to 90 per- cent. F2 (high-purity carbon- Carbonate, more than 90 per- ate). cent.

The few samples that plotted on the boundary lines

of the fields defined were arbitrarily placed in an

adjacent field according to the judgment of the com-

pilers. These judgments were based on such factors

as composition of associated samples, if any, and geo-

logical association.

Samples that contained 33 percent (or more) calcium-

magnesium carbonate were given an additional nota-

tion to indicate the calculated ratio of calcite to

dolomite as follows:

CaCOj

Notation

Calcite_ ___________

Magnesian calcite_

Calcareous dolomite-

Dolomite. _________

(Ca, Mg)C

molal ratio

1. 9:1. 0 0.5:0. 9
2. 1:0. 5 0 :0. 1

CaO/MgO

weight ratio

26. 43: oo
27. 173:26. 43
28. 700: 4. 173
    1. 391: 1. 700

Organic matter had been determined separately in

relatively few of the analyses assembled in this report.

In the calculations for most of the analyses, the classi-

fication system used in this report has tended to include

the undetermined organic matter in the clay fraction.

For this reason, if organic matter is given separately,

it is added to the clay fraction.

A detailed explanation of the successive steps by

which the classification is applied to individual analyses

is given in the section "Calculations for Classifying

Analyses."

Assignment of an analysis to a compositional group

is determined by calculating the three main components

from the analysis to 100 percent. These calculated fig-

ures are not given in the tables.

CATEGORIES

The categories are based on the degree to which the

three main components used to define the groups are

admixed with other materials. The categories are de-

fined by the following amounts of the three main

components:

Percent Category

90______________________ Common rock 50-90_____________________ Mixed rock <50____________________ Special rock

The special-rock categories are designated according to

the kind of material admixed with the three main

components.

The boundaries of the special-rock category were not

always strictly followed. Several analyses that would

fall into the mixed-rock category were included in the

special-rock category because the composition of the

sample is either unusual or of interest for other reasons.

Such analyses can be found more easily when they are

listed with other analyses of similar character, rather

than with analyses grouped on the basis of the three

main components. Some of these special-rock analyses

that do not meet the definition of the special-rock cate-

gory also do not meet the general criteria, for inclusion

in the compilation. (See p. 7-8.)

The relation of the three general categories to one an-

other is clarified by the use of a four-cornered tetrahe-

dron that represents a four-component classification

system. (See fig. 2.) The base of the tetrahedron may

be taken as the triangular diagram of figure 1, its three

corners being, respectively, 100 percent uncombined

silica, 100 percent clay, and 100 percent calcium-magne-

sium carbonate. The apex of the tetrahedron is then

100 percent of some component, or components, other

than uncombined silica, clay, or calcium-magnesium

carbonate. The interior of the tetrahedron the volume

above the basal triangle represents those rocks com-

posed partly of the three components (uncombined

6 CHEMICAL^ COMPOSITION^ OF^ SEDIMENTARY^ ROCKS

amounts of uncombined silica, clay, and calcium-magnesium carbonate and yet not obscure rocks of unusual or economi- cally significant composition, a clay molecule was chosen with a SiO2/R2O3 molecular ratio of 3. The choice of this ratio means that when analyses of clay or ferruginous matter have a SiO2/R2O3 molecular ratio of less than 3 and are classified under this system, they are found to show various amounts of excess Al2Oa and excess Fe2O3. Such analyses are further examined to determine whether these more aluminous com- ponents amount to more than 50 percent. If they do, they are placed in a high-alumina special-rock category and subdivided according to the weight-percent ratio of silica to alumina determined in the analyses. The silica-alumina weight-per- cent ratios of assumed constituents are as follows:

Conventionalized clay_________________ 1. 768 Kaolinite minerals___________________ 1. Bauxite minerals____________________ 0

These ratios lead to the following divisions of group H:

Group Hk: Kaolinlike clays (kaolinlike minerals, no bauxite).

SiO2/Al2O3 weight-percent ratio from 1.178 to 1.768. 2. (AliOs)+H..O (however determined) >50 percent. Group Ha: High-alumina clays (kaolin!te minerals predomi- nant, bauxite subordinate). SiCVAUOs weight-percent ratio from 0.371 a to 1.178. Al2O3+SiO2+H2O (however deter- mined) >50 percent. Group Hb: Bauxite and bauxitic clays (bauxite minerals pre- dominant, kaolinite minerals subordinate). SiO2/Al2Oa weight-percent ratio <0.371. Al2O3+SiOi!+H2O (however determined) >50 percent. Group Hb is not represented in the analyses given in this report.

Other groups are:

Group Na (rock salt) : Analyses that include materials con-

taining more than 50 percent NaCl.

Group G (gypsum) : Analyses of rocks containing more than

50 percent gypsum (CaSO-2H2O) or anhydrite (CaSO). Group S (sodium and magnesium sulfate, miscellaneous sulfate-, carbonate-, and nitrate-bearing material) : Analyses mostly of materials containing more than 50 percent of sodium and magnesium salts.

Group P (phosphorite) : The phosphate mineral in phosphorite is calculated as fluorapatite (9CaO-3P2O5 -CaF2). The analyses of phosphorite that contain 21.1 percent P2O5 or more cor- respond to those containing 50 percent fluorapatite or more. A few analyses reporting a little less than 21.1 percent P2O are included in table 24 because the samples are part of a sequence of analyzed samples containing more than 21.1 per- cent P2O5. Other analyses that indicated a content of less than 21.1 percent P2O5 are calculated in the regular manner for uncombined silica, clay, and calcium-magnesium carbonate. Group Fe (iron-rich rocks) : Most analyses of iron-rich rocks in this report contain more than 50 percent ferric oxide or ferrous oxide.

Group Mn (manganese-bearing rocks) : Several analyses contain

less than 50 percent manganese oxides; even so, they were listed in this category on the basis of potential economic value or special interest.

Group M (miscellaneous) : In some, but not all, components

other than uncombined silica, clay, and calcium-magnesium carbonate make up more than half the rock. Analyses of

1 SiO2/Al2O3 weight-percent ratio for a mixture of equal amounts of

bauxite minerals and kaolinite minerals.

coal and the ash of coal make up most of the group. The rest of the analyses those of oil shale, weathered igneous rock, nodules, and baritic sinter are included in this group because they do not meet the criteria for inclusion in either the common- or mixed-rock categories.

DISCUSSION

No grading was made of the analyses into categories

of superior, good, and fair. This separation would re-

quire the wisdom of Solomon, and it might prevent the

user of the report from making his own assessment.

The date of original publication of the analyses affords

the user a generalized means by which the reliability of

such analyses can be appraised. Wherever available, the

analyst's name is given as an additional basis by which

the quality of the work may be judged. A critical se-

lection of truly superior analyses of sedimentary rocks

can probably best be made after the present, more inclu-

sive compilation has become available. Distribution of

analyses by State, by classification groups, by category,

or by other characteristics is given in tables 29-33.

The user should note that the published analyses,

despite their large number, are probably not truly rep-

resentative of the composition of all sedimentary rocks

of the region. Most of the analyzed rocks were selected

because they are (or were thought to be) of special eco-

nomic interest and are, hence, probably of rather unus-

ual chemical composition. For example, limestone that

contains 95 percent or more CaCO3 is grossly overrepre-

sented in the published analyses; natural limestone

analyses show a wide range in CaCO3. But this geo-

chemically unrepresentative or biased nature of the pub-

lished analyses does not necessarily detract from the

potential usefulness of these analyses for other pur-

poses ; in fact, there is a great variety of uses to which

these analytical data may be put. Carbonate rocks of

unusual purity were specially selected for analysis,

which affords the potential manufacturer of lime, in-

dustrial fluxes, and other mineral commodities valuable

information on localities where the best source materials

for his particular purpose can most readily be obtained.

The geologist or geochemist interested in estimating

the average composition of the earth's materials prob-

ably cannot find the gross averages of thousands of

published analyses of unusually pure limestones

particularly useful for his purpose. Careful observ-

ance, however, of the areal distribution and thickness of

different rock types and of different geologic formations

represented by the published analyses should enable the

geologist or geochemist to make closer estimates of

average compositions than most of those now available

(or at least enable him to discover which rock types and

formations are most in need of new analytical data).

COLORADO, KANSAS, MONTANA, NEBRASKA, NORTH DAKOTA, SOUTH DAKOTA, WYOMING

Several noteworthy questions and facts about sedi-

mentary rocks resulted from the compilation, but only

a few can be mentioned here. One possibly significant

relation became apparent when the 2,362 classified anal-

yses of this report were plotted on triangular diagrams

(figs. 3-9). A very large proportion of all the analyses

fall not within the central region of the diagram, as

might reasonably be expected, but within about 5 per-

cent of the exterior boundaries of the triangle. This

result means that many samples of uncombined silica

and clay mixtures contain very little calcium-magne-

sium carbonate, and that many samples of clay and cal-

cium-magnesium carbonate mixtures contain very little

uncombined silica, and so on.

The somewhat unexpected relation just mentioned is

closely analogous to an empirical observation also re-

ferred to previously that a very large proportion of

the classified analyses of this report fall into the com-

mon-rock category and that relatively few fall into the

mixed-rock category. (See figs. 1, 2.) Plotted on the

composition tetrahedron, the analyses tend to group

mainly along and near its edges and exterior faces, and

not in the center. The tendency of the analyses to group

at certain places in the tetrahedron can be partly ex-

plained by the predominantly economic interest that

governed the selection of certain rock types for analysis.

This bias of sample selection accounts readily enough

for the concentration of analyses of silica sand (group

A) and of high-calcium limestone (group F2 ). But the

concentration of analyses along the edges between the

corners of the tetrahedron and near its basal plane is

not so easily accounted for by this explanation. Also,

exclusion from this compilation of those analyses having

summations less than 95 percent probably tended to

eliminate the incomplete analyses of rocks of more com-

plex composition. This explanation, however, probably

accounts for only a small part of the empirically ob-

served grouping.

This relation, then, is probably not an artifact result-

ing from systematic bias in the choice of analyzed sam-

ples or in the classification system used; rather, the

grouping relation is largely a result of natural sedimen-

tation processes that tend to make these environments

favorable for deposition of sand and unfavorable for

the deposition of clay and carbonates. The reverse is

also true. Thus, the environments of sand, clay, and

calcium-magnesium carbonate deposition may, to a

measurable extent, be mutually opposite. If so, the data

of this compilation stand as a tribute to the good judg-

ment of geologists who, years ago, adopted the familiar

sand-clay-calcium-magnesium carbonate diagram. The

validity of these relations will be substantiated or weak-

ened as the compilation of analyses of rocks of other

regions progresses.

ACKNOWLEDGMENTS

Dorothy Welsh, Norene Altman, Marilyn Krog, Anne

Nalwalk, and Kuth Bell participated for various periods

of time in the compilation of data for this report. For

additional information concerning the stratigraphic

unit and the specific localities of samples, appreciation

is extended to the following members of the State Sur-

veys : W. M. Laird and Miller Hansen, North Dakota

Geological Survey; E. P. Rothrock and A. F. Agnew,

South Dakota Geological Survey; R. T. Runnels, Uni-

versity of Kansas, State Geological Survey; U. M.

Sahinen, Montana Bureau of Mines and Geology; and

H. D. Thomas, Geological Survey of Wyoming. The

writers are grateful to the approximately 50 geologists

from various parts of the United States and Canada

who contributed constructive criticism and helpful sug-

gestions during the planning of this compilation.

GENERAL INFORMATION

CRITERIA FOR INCLUSION OF ANALYSES

The chemical analyses of sedimentary rocks were

taken from many publications, and as a result the con-

stituents determined, as well as the methods used for

determination, vary widely. Uniformity seemed de-

sirable in presenting the analyses in this report, and

several general rules were formulated. The informa-

tion concerning some of the analyses included is prob-

ably inadequate for certain purposes. However, a more

critical selection from this large number of analyses can

be made by the reader.

TYPES OF SAMPLES

Sedimentary, metamorphic, and igneous rocks. The

precise dividing line between sedimentary and meta-

morphic rocks is not a sharp one in nature, and differ-

ent authors do not always clarify in their published lit-

erature which way this dividing line lies from a given

analyzed sample; nevertheless, the usage of the in-

dividual author was followed wherever possible.

Slightly altered rocks are generally included; consider-

ably altered rocks are not. An "altered" rock is in-

cluded if the "alteration" is interpreted to be due

primarily to sedimentary or diagenetic processes, rather

than to metamorphic or hydrothermal processes. In

general, Precambrian sedimentary rocks have been

greatly modified by pressure, heat, and circulating

fluids; only those that seem from the description to have

been slightly modified are included. If a sample is part

of a series (as an igneous rock and its weathered and

partly weathered products), the complete series or rep-

COLORADO, KANSAS, MONTANA, NEBRASKA, NORTH DAKOTA, SOUTH DAKOTA, WYOMING (^9)

Lithology. The rock name given to a sample is that

used in the original reference. Where the reference

gives no name, or where the compilers felt there was

some doubt as to the accuracy of the name, a name was

supplied on the basis of either the position of the analy-

sis in the classification system or the compilers' interpre-

tation of the original publication. The name supplied

by the compilers appears in parentheses and is followed

by the name, if any, given in the reference.

Treatment of stratigraphic nomenclature. Because

the stratigraphic nomenclature used in this report is

from many published sources, the names and ages do

not necessarily reflect the latest-usage of the U.S. Geo-

logical Survey. The formal geologic names have not

been capitalized in accordance with the "Code of Strati-

graphic Nomenclature" (Am. Comm. on Strat. Nomen-

clature, 1961). The age and formation of each sample

is given in the descriptive notes as reported in the pub-

lished source of the analysis, except for some samples

for which the reported assignment is so out of date as

to be misleading and better information could be ob-

tained conveniently. The age is not repeated if more

than one analysis of the same formation appears on

the same page.

Chemical analyses. The lists of constituents in the

tables were simplified as much as possible by the use

of footnotes to indicate that the entry shown as SiO

was reported in the original published analysis as in-

soluble matter; that the figures for CaO and MgO are

derived from an original analysis in which CaCO3 and

MgCO3 were reported; or that an oxide figure was

calculated from an original report of the element if the

element amounted to more than 0.05 percent, and sim-

ilar information. The analyses are thus brought into

a superficially similar form.

Minor elements such as arsenic, vanadium, selenium,

and others were determined chemically for a few

samples that were also analyzed spectrographically.

Analyses for such minor elements are listed with the

spectrographic analysis and are identified as chemical

determinations by means of a footnote.

Spectrographic analyses. Spectrographic analyses

of minor constituents are given only for those samples

for which chemical analyses of major constituents are

also available. Some incomplete chemical analyses

have been included if spectrographic analyses are avail-

able, but if a great many incomplete chemical analyses

and accompanying spectrographic determinations are

available, a selection was made. This selection shows

the upper and lower limits of each constituent analyzed.

The methods of spectrographic analysis and the con-

stituents looked for vary considerably from one labo-

ratory to another, and no attempt was made to evaluate

the spectrographic data.

Mineralogy. The word "mineralogy," as used in this

report, indicates that information on the mineralogy of

the sample is available in the original publication.

Nil, None, Trace. The words "nil," "none," "trace,"

"slight trace," and similar terms are used in accordance

with the original publications. These terms may have

different meanings to different chemists, and it thus

seemed unwise to attempt reduction to a more nearly

uniform nomenclature.

Punctuation and footnotes. Additional information

not available in the original publication but relating to

the locality, formation, or rock name is in parentheses if

it was supplied by the compilers. Information supplied

by others is cited as written or oral communication.

Parentheses are also used in the tables of analyses to

indicate those amounts not included in the total; a foot-

note for such amounts gives further information. Also,

parentheses are used for some references to aid clarity

where more than one reference is cited. Each set of fac-

ing pages with chemical analyses and accompanying

descriptive notes are considered as a unit, and the foot-

notes, numbered accordingly, apply only to that unit.

Reported use of rock. Generally, the information on

the actual or potential economic use is given only if it is

stated in the original publication. No effort was made

to equate the different terms used nor to bring the in-

formation up to date.

ANALYSES

The 2,842 analyses compiled are presented in tables

1-27 of this report. The tables are arranged in sequence

according to classification groups: the common- and

mixed-rock categories, and the special-rock category.

For groups A, C, and E, each table lists the analyses by

States in alphabetical order and contains all the anal-

yses in the group. For groups B, D, FI, and F2, each of

which contains several hundred analyses, the analyses

for each State (or group of States) are given in a sepa-

rate table. The tables for these groups are alphabetical-

ly arranged by State(s). Each group, special-rock

category, is in a separate table.

10 CHEMICAL COMPOSITION OF SEDIMENTARY ROCKS

TABLE 1. Analyses of samples from Colorado, Kansas, Montana, Nebraska, South Dakota, and Wyoming containing more than 75 percent uncombined silica (Group A) common and mixed rock categories COt. ............. s... .............. sos .............. Class ............. MgO .............

T10.J .............

PtO|.. ............ S. ................ oo MgO. ............. c/-
Class............. Colorado Kansas Kansas 1 Includes MnOz. 2 Reported as R2O3 , includes alumina but not iron oxide. 3 Includes undetermined manganese. 4 Total iron. 5 Total Fe (Clarke, 1915, p. 220). 8 Includes ZrO2 and V2O5 if present. 9 Not included in total. 10 140°-1,000° C. 11 At 1,000° C. B 105°-1,000° C. 13 98.00 percent (Haworth and others, 1904, p. 79). 14 Insoluble siliceous residue. 15 Total sulfur. w 99.58 in text.

• Si [Samples of mixed rock category indicated by an asterisk (*). Chemical analyses arranged by State, county, and stratigraphic position]
• A
  • Na Fe20s
• K
  • TiO
• P
• A SiOz...
• Fe
  • Na CaO..............
• A SiOjj..............
• Fe
  • Ti02 H20-
• P - 5A18- - 95. - 4. -. -. - 1. - 100. - 88, 12, - 5A18- - 98. -. -. -. -. - 100. - 97, 3, - 5A18- - 98. -. -. -. -. - 100. - 97, 3, - 5A18- - 98. -. -. -. -. - 99. - 97, 2, - 5A30- - 96. -. -. -. -. - 97. - 96, 1, - 6 | - 5A36- - 93. - 5. - 1. -. -. - 100. 9 (4.45) - 89. - 5. - 1. -. -. - 4. - 100. - 78,21, - 5A47- - 90. -. - 2. -. - 3. - 2. -. - 99. - 86, 8, - 15A4- - 85. - 1 6. - 4. - 1. -. - 1. - 2. - '. -. - w 1. Nil - 99. - 73, 22, - 15A4- - 97. - 2 1. -. - \ 6. - 11. - 100. - 94, 5, - 15A4- - 98. - 3 r -. -. -. - 1. - I. - 8. -. -. Tr. - tt. - 100. - 97. 3, - 15A10- - 96. - 2. - 5. - 99. - 91,9, - 15A10- - 96. - 2. - 5. - 99. - 93, 7, - 15A11- - 99. -. } - -. Tr. - 99. - 99, 1, - 15A11- - 13 98. -. -. Tr. -. - 99. - 98. 2, - 15A11- - 99. -. -. Tr. -. - 99. - 99, 1, - 15A11- - 97. - 1. -. -. -. - 100. - 94, 6, - 15A11- - w 97. - 1. -. Tr. - 99. - 95, 4, - 15A11- - M 92. - 1. - 4. Tr. - 16 97. - 90, 4, - 15A15- - 84. - / 5. - \ 1. - 3. - 95. - 72, 24, - 15A17- - 98. - 3. -. -. -. -. -. - 8. -. -. -. Nil - tt. - "100. - 97, 3, - 97. - 8 1. -. -. -. - 8. -. - W. - 99. - 15A27- - 91. - 3. -. -. -. - > 1. - 1. - 1. - 99. - 84, 12, - 15A33- - 88. - 3. - 1. - 1. -. - / 1. - \ 1. -. - 2. - 99. - 80. 14, - 15A33- - 97. - 1. -. -. -. -. - 1. - 100. - 95, 5, - 15A33- - 86. - 3. - 1. - 1. - 1. - 1. - 1. -. - 2. - 99. - 78, 16, - 15A37- - 97. - ." - 5. -. -. -. - 99. - 95, 5, - 15A37- - 98. -. - 5. -. -. -. - 100. - 96.3, - 15A37- - 97. -. - 5. -. -. -. - 99. - 96, 3, - 15A37- - 98. -. - 5. -. -. -. - 99. - 97,3, - 15A49- - 97. - 3 1. -. -. -. -. -. -. -. - «. - 99. - 95, 4, - 94. - 3 2. -. -. -. -. -. -. -. - 12 1. - 99. - 15A63- - 97. - 5. - 98. - 97,2, - 15A63- - 97. - 5. - 97. - 96, 2, - 15A69- - 98. -. -. -. -. -. - 1. - 99. - 97,3, - 15A72- - 86. - 4. - 2. - 3. - 96. - 77, 20, - 15A74- - 87. - 4. - 1. -. - 1. - 3. - 1. - 2. - 100. - 78, 17, - 15A74- - 95. - 1. -. -. -. -. - 2. - 99. - 93,6, - 15A74- - 96. - 1. -. -. -. -. - 1. - 99. - 94,5, - 7 Includes ZcOz and V2O 6 Reported as other (chiefly alkalies).

12 CHEMICAL^ COMPOSITION^ OF^ SEDIMENTARY^ ROCKS

TABLE 1. Analyses of samples from Colorado, Kansas, Montana, Nebraska. South Dakota, and Wyoming containing more than 75 percent uncombined silica (Group A) common and mixed rock categories Continued

Si ............. A ............. Fe ............. MgO. ............. CaO.............. Na2 0 ............. K .............. H20- ............. P ..............

S ..............

Class .............

SiOj .............. AljA ............. Fe2 Q, ............. MgO. ............. CaO.............. Na ............. K2O ..............

P /-\

Total ........ Class .............

AlzQ.............. FezQ,. .... ...... MgO. .............

Na2 O ............. KZ .............. H2 0 .............. Ti02. .............

Kansas

15A80- 1 71.

.

5 4.

66,13,

41 15A82-

. . . .

.

95, 4, 1

42 15A103-

97,1,

43 15A103-

98,1, Nebraska 53 26A28- 2 81. .

4 5. . .

4 1.

(76,12)

54 26A42- 2 81. .

4 5. . .

4 1.

(76,12)

55 26A55-

.

. .

93, 6, 1

56 26A55-

.

. . . .

93, 6, 1

44 15A103-

97,2,

45 15A103-

None .

94, 6, 0 South Dakota 57 40A24-

) 1. Tr. .

96,4,

58 40A52-

f 6. V.

. __ 3.

78,22, Wyoming 66 49A23- 6 84. 7 5. 8 1. . . . .

.

67 49A24-

Tr. . .

.

68 49A24-

. . . . . .

69 49A24-

. . .

.

70 49A24-

Tr. . . . .

71 49A24-

Tr. Tr.

.

46 15A103-

99, 0, 0

Montana 47 25A1- 2 88.

(80,15)

59 | 60 49A1-

.

98,2,

C .....

c/-\

Org.matter Ign. loss less H2 O Total... Class ....

.

.

48 j 25A1- 2 87.

(75,23)

49 25A14-

. . . . .

84,14,

50 25A29- 2 88. 2 .

( 84, 9) 0

Nebraska 51 26A10- 2 81. .

4 5. 34 . .

4 1.

52 26A18- 2 81.

. 73

4 5. 33 . .

4 1.

(76.12) Wyoming 61 62 49A1-

96, 4, 0

. . .

.

66

U 100. 73,23,

67

72,23,

68

Tr.

.

89jll,

63 49A7-

.

. J. 1 .«

89,10,

49A11-

91,9,

65 49A19-

.

98, 0, 0

69

Tr.

.

80L17, 0

70

91,8,

71

Tr. Tr.

86,11,

Semiquantitative spectrographic analyses l-5 percent; D = 0.1-l percent; E = 0.01-0.1 percent; F = 0.001-0.01 percent; G = less than 0.001 percent; ND=not detected. Li, Be, Co, Ga, Ge, As, Cb, Cd, In, Sn, Sb, Ba, Ta, W, Pt, Au, Hg, Pb, and Bi looked for in all samples but not detected]

Na Mg ................

Ti ................

E

E

C

E

Mn ...............

Cu ...............

E

G

G

F

E

G

Zn ............... Sr ................ Zr ............... Mo ............... Ag...............

E

ND

F

F

ND

ND

F

E

F

ND

E

F

E

F

G

1 Includes insoluble. 2 Insoluble. For samples 51-54 reported as insoluble (siliceous) matter. s Total Fe (Clarke, 1915, p. 220). 4 Calculated from reported MgCO3 , CaCO3 , and (or) lime phosphate. 5 Reported as moisture and volatile. 6 "Soluble" silica, by 5 percent Na2CO3 solution, probably about 0. percent judged by analyses of similar material.

7 Includes P£>s. P£>s probably about 0.4 percent judged by anal; of similar material. 8 FeO probably absent. 9 Reported as NaCl. "Reported as C, 0.78 percent; H, 0.07 percent. 11 100.03 in text.

COLORADO, KANSAS, MONTANA, NEBRASKA, NORTH DAKOTA, SOUTH DAKOTA, WYOMING 13

DESCRIPTIVE NOTES

[First page number in reference indicates source of analysis]

Kansas Continued (^) Nebraska- - Continued *40. Rice County. Upper Cretaceous, Dakota sandstone. (T. 20 S., R. 10 W.), 3 miles north and 2 miles east of town of Raymond. Analyst, Whitaker. (Whitaker and Twenhofel, 1917, p. 474.) (Analysis shows 12.1 percent MnsO4 ; suggests 4.4 percent gypsum, 2. 8 percent more SOS than required for gypsum.) Manganese "wad," dark-brown to black, friable, soft. Surface sample.

41. Rooks County. Pliocene, Ogallala formation. Sec. 10, T. 6 S., R. 19 W. (Frye and Swineford, 1946, p. 63, 39, 62, 71, pi. 8.) Quartzite, green to brownish-green; fine-grained to conglomeratic; in lentils. Bulk density, 2.39. Soluble in HC1, 5.10. Estimated tonnage. Index map, outcrop map; physical tests. Possible use: Railroad ballast, riprap, road metal. 42-45. Wilson County. Pennsylvanian, Stranger formation, Tonganoxie sandstone member and Lawrence shale, Ireland sandstone member (R. T. Runnels, written communication, 1953) reported as Buxton formation and as St. Peter sandstone. Analyst, Steiger. (Burchard, 1906, p. 463, 462, 470, 471; Clarke, 1915, p. 220.) Sandstone. Physical properties. Possible use: Glass sand.
42. Sec. 20, T. 29 S., R. 14 E. Lab. No. 1. Sandstone, grayish-white.
43. Sees. 20 and 21, T. 29 S., R. 14 E. Lab. No. 2. Sandstone, grayish- white.
44. T. 29 S., R. 14 E. , 5 miles southwest of town of Fredonia. Lab. No. 4. Sandstone, yellowish-brown.
45. T. 29 S., R. 15 E., 1.5 miles southeast of Fredonia. L^b. No. 3. Sandstone, light-gray, micaceous, porous; grains angular; coarser than other sandstones in vicinity; cross-bedded; 6 ft exposed.
46. County, formation, analyst, name and use as in samples 42-45. (T. 30 S., R. 16 E., town of Neodesha.) Lab. No. 2222. (Clarke, 1915, p. 220.)

47-48. Beaverhead County. Permian, Phosphoria formation. NW?SW? sec. 23, T. 9 S., R. 9 W., near Sheep Creek Canyon. Spectrographic analyst, Mortimer. Index, outcrop map; generalized columnar section. (For other analyses from same measured section see samples 1-3 group B, sample 1 group D, and samples 15-18 group P; of this compilation.)

47. Lab. No. ERC-51. (Swanson and others, 1953b, p. 18, 2, pi. 1.) Sandstone, cherty; bed C-12; 7.2 ft thick, 5.2 ft from top of member; trench sample.
48. Lab. No. LAT-78. (Swanson and others, 1953b, p. 16, 2, pi. 1.) Mudstone and chert; bed E-10; 10.2 ft thick, 1. 9 ft from top of member; trench sample.
49. Fergus County. Upper Cretaceous, Eagle sandstone (U. M. Sahinen, written communication, 1957). Sec. 23, T. 17 N., R. 18 E., about 3 miles south- west of town of Hilger. (Robertson, 1950, p. 66, figs. 1,2.) Silica sand, light-gray; grains slightly rounded; loosely consolidated. Channel sample across 7 ft of lower part of exposure. Index map, generalized geologic map; screen analysis. Possible use: Molding sand, green or amber glass.
50. Madison County. Phosphoria formation. SEjNEi sec. 35, T. 5 S., R. 1 E., near Jack Creek. Spectrographic analyst, Mortimer. Lab. No. RWS-103-47. (Swanson and others, 1953b, p. 5, 2, 7, pi. 1.) Chert and quartzite; bed 21; 8.6 ft thick; 47.5 ft below top of formation. Trench and outcrop sample. Index, outcrop map; generalized columnar section.

Nebraska 51-54. (Pleistocene.) Analyst, Aughey. (Aughey, 1876, p. 246; Aughey, 1880, p. 267.) Loess.

51. Buffalo County. (T. 8 N., R. 15 W.) bluffs near town of Kearney.
52. Clay County. (T. 7 N.. R. 5 W.) near town of Sutton.
    53. Douglas County. (T. 15 N., R. 14 E.) near town of Omaha.
    54. Harlan County. (T. 2 N., R. 19 W.), Republican Valley, near town of Orleans. 55-56. Lancaster County. Dakota sandstone. (T. 10 N., R. 6 E.)
53. Robber's Cave, near town of Lincoln. (Burchard, 1907, p. 382, 381; Condra, 1908b, p. 195.) Sand, iron-stained. Most of sand caught on meshes 30, 40, and 50. Possible use: Green or dark glass, if washed.
54. (May be same as sample 55.) Near Lincoln. Analyst, Borrowman. (Condra, 1908b, p. 44, 42, 43.) Sand, light-yellowish or brownish color; angular to rounded quartz grains coated with iron oxide. Possible use: Low-grade glass.

South Dakota

57. Fall River County. Pennsylvanian, probably Minnelusa sandstone. (T. 7 S., R. 5 E.) town of Hot Springs. (Carpenter, 1888, p. 168.) Sandstone, reddish. Use: Building stone.
58. Pennington County. Lower Cretaceous, Fuson shale. (T. 1 N., R. 7 E.), Rapid City. (Todd, 1902, p. 104, 103.) Clay, light-gray, compact, con- choidal fracture. Possible use: Refractories.

Wyoming

59. Albany County. Pennsylvanian, Casper formation. Sec. 25, T. 16 N., R. 73 W., 3 miles east of town of Laramie. (Osterwald and Osterwald, 1952, p. 62.) Glass sand, white, friable, soft. Thickness, 2-4 ft; overburden, 0-10 ft thick. Partial stratigraphic (measured) section. Use: Glass.
60. Probably another analysis of sample 59. (Haugh, 1942, p. 63.)
61. Information as in sample 59.
62. Probably another analysis of sample 61. (Haugh, 1942, p. 63.)
63. Fremont County. Upper Cretaceous, Fox Hills sandstone. (T. 27 N., R. 98 W.), St. Mary's Peak. Analyst, Brewster. Lab. No. 98. (Hague, 1877, p. 155; King, 1878, table 7A.) Sandstone, steel-gray, compact, bedded.
64. Laramie County. Dakota sandstone. (T. 16 N., R. 69 W.) outlying ridge north of Wahlbach Spring. Analyst, Brewster. Lab. No. 99. (Hague, 1877, p. 41; King, 1878, table 7A.) Sandstone, yellowish-brown, fine-grained, even textured.
65. Sweetwater County. Upper Cretaceous, Laramie formation. (T. 18 N., R. 101 W.), Black Butte. Lab. No. 96. (King, 1878, table 7A, p. 336, 337.) Sandstone. Description of Black Butte area.
66. Weston County. Upper Cretaceous, Mowry shale, upper part. Sec. 7, T. 48 N., R. 65 W., near town of Thornton. Analyst, Fairchild; collector, Rubey. Lab. No. C-870. (Rubey, 1929, p. 157.) Siliceous shale, weathered. 67-71. Yellowstone National Park. (Recent.) Upper Geyser Basin.
67. Artemisia Geyser. Analyst, Whitfield; collector, Weed. (Clarke, 1915, p. 223.) Siliceous sinter. 68-69. (Alien and Day, 1935, p. 145, 232.) Siliceous sinter, air-dried. Index map.
68. Biscuit Basin, 50 ft from Mustard Geyser.
69. Near Daisy Geyser. 70-71. Analyst, Whitfield. (Weed, 1889a, p. 670.) (Minor differences in constituents and amounts, see Clarke, 1915, p. 223.)
70. Emerald Spring. Siliceous gel, light-pink, bouyant. Air dried.
71. Old Faithful Geyser. Sinter, white, compact.