,, 

I 

, 

UNITED STATI8 DEPMtNENTOF THE INT ..... 

Ra1·~ymaa WU.ur, Seeretary 

CBOLOQICA.L SUJlVBY 

-..Otis Slillth, Dlnetor 

Professional Paper 168 

-- ··'+ 

' . 

ORIGIN AND :MI~OFOSSILS OF TH~ JUL SHALE 

OF THE GREEN RIVER FOR~~TION 

OF COLORADO AND UTAH 

. BY 

WILMOT H. BRADLEY 

UNITED STATES 

GOVERNMENT PRINTING OFFICE 

W ASBINGifON : 1931 

For nle by the Superiatendent of DoeuJ~W~Bta. Washington. D. C. - • • • • Prlee 60 el!nts 

Abstract--------------------------------------~--­

Introduction--------------------------------------

Location and extent of the area _________________ _ 

Previous geologic work ___________________ ·----- Fieldwork ___________________________________ _ 

Laboratory work ______________________________ _ 

Acknowledgments ____________ · _________________ _ 

·Topography and drainage __________________________ _ 

Structure~---------------------~------------------ Major features _____ · __________________________ _ 

Minor features _____________________ - ______ - __ _ 

Age of folding ________________________ ~ _______ _ 

. Stratigraphy _____________________________________ _ 

Lithologic terms used __________________________ _ 

Wasatch formation ____________________________ _ 

Green River formation ________________________ _ Age _____________________________________ _ 

Lithology _________________________ ._ .. _____ _ 

Rocks east of Bitter Creek, Utah _______ _ 

Douglas Creek member ____________ _ 

Garden Gulch member _______ ------

Parachute Creek member __________ _ 

Evacuation Creek member _________ _ 

Delta and shore· facies _____________ _ 

Columnar sections_~ ______________ _ 

Rocks west of Bitter Creek, Utah _______ _ 

Duchesne-Uintah county line sec- tion ___________________________ _ 

Gate Canyon section ______________ _ 

Indian Canyon section _____________ _ 

Correlation of facies and zones in Uinta and 

Piceance Creek Basins ___________________ _ 

Bridger formation ________ ----- ________________ _ 

Lower beds _____________ ---- __ ----- ____ _:_-_· 

Upper beds--------------------------------

·Relations of the Tertiary formations in the Uinta Basin ____________________________________ --

The oil shale _____________________________________ _ 

Definition ____________________________________ _ 

CONTENTS 

Page 

v The oil shale-Continued. 

1 Sedimentary structure in the oil shale and associ1 ated rocks-Continued. 

2 Minor features of stratification __________ ----

3 Lamination ___ ------------ - _ . - - - - -----

3 Contorted bedding_- __ ---_- ___ -- __ ---_-_ 4 Shale breccias _________________________ _ 

4 Mud cracks_-----_----------~-------""'-

5 Mineralogy-------------------_-_---- __ - ___ -_----

5 Syngenetic minerals_----------- _____ -_----- . 

5 Calcite and dolomite ______ ---- __ ~ ____ ---_ 

6 Analcite and sepiolite _________________ --

6 Pyrite ______ -_-_-_- ___ - __ - ___________ _ 

6 Quartz and opaL----------------------~ 

8 Clastic minerals ________________ -- __ -_-_------

9 Saline minerals and their significance _______ --

9 Secondary minerals---:-------------- ________ -- 9 Concretions ________________ -_-- ______ ---_--

9 Calcite concretions ____________ - _____ -_--

9 Chert concretions--- ____ ---- _______ ----

10 . Microfossils----_----------------------- _______ :..---

11 Previous similar studies ______ -------------------- 14 Prepa~ation of thin sections ____________________ _ 

14 Appearance of organic matter in thin sections---~-- 15 Flora of the oil shale ____________________________ _ 

15 Bacteria _____________________ - _________ -_--

Fungi ___________ --------------- _______ ..:----

15 Algae-------:------------------~-----------

16 F~ellata---------------------------~- 17 Cyanophyceae ________________________ _ 

Chlorophyceae __________ ------- ___ -----

19 Unclassified forms _____ -- __ ---- ________ _ 

19 Bryophyta and Pteridophyta ________________ _ 

19 Spermatophyta _____________________ . ___ ---

22 Gymnospermae ________________________ _ 

Angiospermae ______________ -- ____ - _____ _ 

22 Fauna of the oil shale ___________________ :_ ______ _ 22 Protozoa __________________________________ _ 

22 Sarcodina ____________ - ____ - _________ -_-

Appearance in hand specimens ___________________ · 22 Arthropoda _______________________________ _ 

Occurrence ____________________________________ _ 23 Arachnida ________________ -- __ c. ____ -----

Sedimentary structure in the oil shale and associ- Insecta _______________________________ _ 

ated rocks _______ --------- ____ ~ _____ ··---_,--- .24 Interpretation and significance of the microfossils __ Major features of bedding __________________ _ 24 Structureless organi~ matter-------------------------_ 

Regular beds and their significance ______ _ 24 Phases of Uinta Lake during the Green River epoch ___ _ 

Lenticular beds and their significance ____ _ 25 Index ______________________________________ ~------· 

ILLUSTRATIONS 

PLATE 1. Geologic map showing the distribution of the Green River formation in Colorado and Utah _________________ _ 

2. A, View near Clear (]reek, Colo., showing typical cliffs made by the Green River formation; B, Bedding plane 

of organic marlstone .covered with spinose fiy larvae ______ --------------------------------------------

3. Stratigraphic relations of the subdivisions of the Green River formation in Colorado and Utah ______________ _ 

· 4. A, View down Piceance Creek, Colo., showing the broken cliffs of the Garden Gulch and ·Parachute Creek members; B, Outcrop of_ paper shale showing its flexibility ___ ----------------------------------------------

5. A, Ellipsoidal salt cavities in Evacuation Creek member; B, Close view of cavities formed by radial aggregates 

ofsalt~rystaW-----------------------------------------------------------------------------------

111 

26 

26 

26 

28 

28 

29 

29 

29. 

30 

30 

31 

31 

32 

36 

37 

37 

37 

37 

37 

38 

39 

40 

40 

40 

40 

41 

41 

42 

44 

45. 

46 

46 

46 

4S 

48-

48-

49-

49-

49t 

51! 

5Z 

54 

57 

Page 

2 

2' 

1() 

lOt 

1() 
IV ILLUSTRATIONS 

Page 

PLATE 6. A, Calcite mold of radial aggregate of salt crystals; B, Salt crystal cavities suggesting interlocking plates of 

anhydrite---------------------------------------------------------------------------------------- 10 

7. Columnar section of the Green River formation measured on Parachute Creek, Colo ________ --- _- _- _____ - _ _ _ 10 

8. Columnar sections of the Green River formation measured in Trail Creek, Cathedral Creek, Hells Hole Canyon, 

and White River Canyon, Utah, and north of Deep Channel Creek, ColO-------------------------------- 10. 

9. A, Steev false bedding in the muddy sandstone of a delta facies; B, View southwest across the valley of Minnie 

Maud Creek, Utah------------------------------------------------------------------------------- 18 

10. A, Differential compaction of oil shale and muddy sandstone; B, Mud-cracked organic marlstone bed with 

small calcite pseudomorphs of a salt filling the cracks---------------------------------·----------------- 18 

11. Composite columnar section of the Green River formation measured in Indian Canyon, Utah----------------- 18 

12. A, Differential compaction between Bridger sandstone and the lake beds of the Green River formation; B, 

Lower sandy part of Bridger formation in Duchesne County, Utah-----------------------------"-------- · 1k 

13. Oil yields of oil-shale beds in the Green River formation------------------------------------'------------- 26 

14. A, Contorted bedding in a bed of oil shale; B, Photomicrograph showing thin regular lamination in a rich oil 

shale--------------------------------------·------------------------------------~---------------- 26 

15. A, Mosaic breccia in oil shale; B, Distributive thrust faults in a bed of rich oil shale------------------------- 26 

16. A, Oil-shale breccia showing large fragment oriented at angle to bedding; B, Coarse shale breccia in fairly rich 

oilshale----------------------------------------------------------------------·------------------ 26 

17. A, Photomicrograph of an oil shale showing calcite concretions and lenses; B, Oil shale showing loop bedding__ 26 

18. Photomicrograph showing the figured and structureless components of a rich oil shale __ -------~~---------_..:- 26 

19-28. Microfossils of the oil shale of the Green River formation--------------------------------------------- 42 

FIGURE 1. Index map showing the distribution of the Green River formation ___________________________ .:._____________ 2 

2. Diagram showing the differential compaction at the contact of the Bridger and Green River formations_______ 20 

3. Columnar section showing distribution of salt mold layers in a part of the Green River formation_---~-------- 34 
ABSTRACT 

The Green River formation of Colorado and Utah -is a series 

of lake beds of . middle Eocene age that occupy two broad, 

shallow, simple structural basins-the Piceance Creek Basin, 

in northwestern Colorado, and the Uinta Basin, in northeastern Utah. It averages about 2,000 feet in thickness but 

ranges from about 1,200 feet at the north end of the Piceance 

Creek Basin to about 2,800 feet in the central part of that 

basin and to a maximum of about 4,900 feet in the western 

part of the Uinta Basin. In both basins the Green River 

formation is underlain by beds of sandy mudstone of fluviatile 

origin that belong to the Wasatch formation. In the Piceance 

Creek· Basin the rocks of the Green River formation are the 

youngest rocks exposed except in one area, where they are 

overlain by 400 feet of sandy beds of fluviatile origin that 

appear to be lithologically and stratigraphically equivalent to 

the basal beds of. the Bridger formation of the Uinta Basin. 

In the Uinta Basin the Green River formation is conformably 

overlain by the Bridger formation and that in turn by the 

Uinta formation, both of which are dominantly of fluviatile 

origin and consist of mudstone and sandstone. 

In this paper the terms "oil shale," "marlstone," "mudstone," 

"claystone," "siltstone," "shale," and "paper shale" are 

defined before the lithology of the Green River formation is 

described. The lithology is treated in two geographic divisions-one east of Bitter Creek, Utah, which is in the eastern 

part of the Uinta Basin,· and the other west of Bitter Creek. 

·East of Bitter Creek the formation has been divided into 

four members-the Douglas Creek member (at the base), the 

Garden Gulch member, the Parachute Creek member, and the 

Evacuation Creek member (at the top). The Parachute Creek 

member contains most of the rich oil-shale beds and is divided 

into the lower and upper oil-shale groups, which are separated 

by a thin· unit of relatively barren beds. The upper oil-shale 

group, which contains the "ma:llogany ledge," is the principal 

·oil-shale zone of the Green River formation and probably was 

once continuous from east to west across both basins. At the 

north end of the Piceance Creek Basin is a thick delta and 

shore facies that appears to mark the mouth of a large stream 

that once drained· the great lake which lay north of the Uinta 

Mountains and in which the Green River formation of Wyoming 

was deposited. West of Bitter Creek, Utah, the Green River 

formation is not divided into members. In at least two 

localities it contains thick deltaic facies. In the western part 

of the Uinta Basin the lower beds interfinger with. the Wasatch 

formation. Locally the contact between the· Green River and 

the overlying Bridger formation has been greatly distorted by 

differential compaction. 

The vertical and horizontal distribution of the oil-shale beds 

in the Green River formation of Colorado and Utah are discussed, and the appearance of various sorts of oil shale is 

"\ described. The sedimentary structural features in the oil 

,~ shale and associated rocks ap~ar to indicate two extremes of 

conditions under which beds of rich oil shale were formed. The 

regular beds of great persistence with their thin regular laminae 

seem to indicate stages when the ancient Lake Uinta was not 

only relatively broad and deep but also probably thermally 

stratified, so that the lower stagnant layer of water was favorable to the accumulation of the organic ooze that late~ became 

oil shale. The short lenticular beds, the mud cracks, and the 

shale breccias indicate stages when the water level was low 

and the organic matter accumulated in more or le8s isolated 

residual-puols. · The ·-contortion· ef -the .oiLshale and associated 

beds is ascribed chiefly to differential compaction. 

Microgranular calcite and dolomite are the predominant 

mineral constituents of most of the oil-shale beds, but in a few 

clay minerals belonging to the beidellite group predominate. 

Analcite, an alteration product of volcanic ash, is plentiful in 

many beds. In lesser amounts occur either angular fragmentsor euhedral crystals of quartz, sanidine, orthoclase, plagioclase, 

muscovite, hornblende, pyroxene, zircon, apatite, and opal 

and bits of volcanic glass. A large proportion of these came in "1 

volcanic ash, and the remainder were brought in by streams.v ) 

Pyrite is abundant in most beds and indicates that the original · 

organic ooze was a strongly reducing medium wholly analogous 

to the fetid black organic oozes that are accumulating in certain 

modern lakes. The mineralogy of two typical oil-shale beds' 

is calculated from chemical analyses. Concretions of microgran~ 

ular calcite and do.l9mite and of chert are locally plentiful and 

apperu:tohave f(;rme<;J.~soon afterthe deposition of the ooze. 

The chert concretions contain finely preserved microfossils. 

Molds of salt crystals, glauberite(?), and anhydrite(?) are 

abundant in certain layers of low-grade oil shale or organic 

marlstone~ Calculations based on the distribution of these 

layers in the thickest saline unit suggest that this unit represents 

an interval of reduced precipitation or increased evaporation 

that was of the order of one and a half million ·years in length, 

or about one-fourth of the total length of the Green River epoch. 

The microfossils of the Green River formation ~cur locally in 

beds of unusually rich oil shale and in chert concretions. Thin 

sections of the chert concretions and of many of the oil-shale 

samples were ground in the usual way. The remainder of the 

oil-shale sections were cut with a microtome after the shale had 

been freed of its mineral matter, softened with phenol, and 

embedded in paraffin., Two kinds of organic matter ar~ discernible in thin sections of the oil shale; one is massive and 

structureless and is the matrix of the other, which has definite 

form and consists of organisms or· fragments of them. The 

microfiora of the Green River formation contains two forms 

that are doubtfully referred to bacteria and many fungi spores, 

of which 13 are illustrated and compared with living genera. 

In addition to the spores there are also many fragments 

of the vegetati~e par~s of fungi. Of the algae, all of which 

are microscopiq, one flagellate, a naked protoplast, five 

blue-green algae, and five green algae are described and 

referred tentatively to living genera of fresh-water algae and 

compared with living species. Five forms, probably all algae, 

which are too indefinite to be assigned to any position in the 

natural system are also illustrated and described. According 

to the numbers of individuals found the blue-green algae appear 

to have dominated the microfiora. No diatoms were found. 

Of the higher plants spores and. pollens are plentiful. Eight 

spores and three parts of reproductive organs, all probably 

belonging either to mosses or to ferns, are described. Nine 

different kinds of pollen are described, and-some of them are 

compared with the pollen of living plants. A fragment of bark, 

a part of a spiral tracheid, and a few stellate hairs are the only 

parts of tbe tissues of plants higher than the mosses and ferns 

that have been found. 

v 
. , ... •, 

VI ABSTRACT 

The fauna of the oil shale includes rhizopoda, insects, and 

a mite. Three new species of rhizopoda, all belonging to 

living genera, are illustrated and described. Many of the 

insect remains are fragmentary and include . the chitinous 

integuments of the eyes, the wing scales, and hairs of minute 

adult insects. Pieces of chitinous skins of dipterous larvae 

and their isolated spines are the most plentiful insect remains. 

Complete larvae representing five different families of Diptera 

are illustrated and discussed, though not described. One 

predaceous· mite belonging to the Chelytidae, probably the 

first fossil mite to be found in this hemisphere, is also illustrated 

without systematic· description. The abundance of the fungi 

suggests the possibility that the organic ooze was occasionally 

exposed to air. 

The predominance of microscopic fresh-water algae and 

Protozoa over the remains of land plants with the exception 

of pollens and spores suggests that the greater part of the 

organic matter in the oil shale was derived from microorganisms 

that grew in the lake and strengthens the analogy between 

the original organic ooze and the black fetid oozes now accumulating in certain lakes. The pollens and spores were brought 

into the lake chiefly by wind. Most of the fly larvae, which 

are found in beds of organic madstone, appear to indicate 

rather shallow water. 

Mo~t of the structureless organic matter in the Green River 

oil shale is isotropic, though there are also two anisotropic 

varieties. The writer concludes that the structureless organic 

material, which makes up by far the greater part of the total 

organic matter of the oil shale, was derived from the partial 

putrefaction of aquatic organisms that grew in the ancient 

lake. Mechanical and chemical actions, such as the mastication and digestion of the original material by bottom-living 

organisms, were probably also important factors in the·· disintegration of the organic matter. When the organic matter 

was reduced to a gelatinous condition it apparently resisted 

further bacterial decay. Other m~croorganisms accidentally 

entombed in the gel were completely impregnated with it, 

supported by it, and so protected from decay or. disintegration 

until the whole mass became lithified. The manner in which . 

the microfossils of the oil shale were preserved is thus somewhat'akin to the manner in which the original resins of amber 

entombed minute organisms and so preserved them. 

The ancient Uinta Lake, in which the sediments of the 

Green River formation of Colorado and Ut~h accumulated, 

appears to have had throughout its life an extraordinarily ... ~ 

large area compared with its depth. It was probably panshaped, with very gently sloping shores. At first it was large, 

shallow, relatively stable, and entirely fresh. Later and for 

the greater part of its life it seems to have fluctuated in volum.e 

considerably, having alternately an outlet and then none. 

During these stages of fluctuating level and restricted discharge the lake water became rich in foodstuffs and th~ 'water 

temperature was generally rather high, and under these optimum conditions enormous quantities of minute aquatic organisms were produced. At many times, however, during this 

part of the Green River epoch the lake was apparently deep 

enough for the water to be thermally stratified, and the deposits 

that accumulated at such times were varied. The stages 

that followed, in the later part of the epoch, were somewhat 

less favorable to the growth of aquatic organisms; the concentration of dissolved salts increased, so that in parls of the 

basin, perhaps isolated from the rest, salt was repeatedly 

deposited,. though never in sufficient quantity to make up 

continuous beds. After the saline phases the lake was again 

freshened either by increased rainfall, by diminished evaporation, or by the cutting down of the outlet. 
ORIGIN AND MICROFOSSILS OF THE OIL SHAL~ OF THE GREEN 

RIVER FORMATION OF COLORADO AND UTAH 

By w. II. BRADLEY 

INTRODUCTION 

The Green River formation offers a rare opportunity 

for the study of lacustrine sedimentation, for it records 

with remarkable completeness a varied but essentially 

. unbroken series of events lasting through nearly a 

third of a geologic epoch. Moreover, it has a great 

lateral extent, and in that al~o it is unusual for a 

laeu~trine formation. But its chief claim to interest 

is the oil shale, who~e potential economic value has 

attracted widespread attention. 

Little is known, however, about the geologic history, 

origin, microstructure, and composition of the oil ~hale 

and it is the chief aim of this study to elucidate those 

aspects. To that end the field relations of the oil 

shale to the formation as a whole have been studied 

at many places· in Colorado and Utah which the 

writer regards as critical to their proper interpretation. 

The features of sedimentary structure, such as bedding, lamination, contorted bedding, shale breccias, 

and mud cracks, have revealed much regarding the 

physical conditions under which the deposits accumulated. In a comparable way the mineralogy of the 

oil shale has revealed the ehemical and to ~orne extent 

also the physical conditions attending its formation.· 

These physical and chemical criteria, together with 

the stratigraphy of the region, make it possible to 

reconstruct a fair picture of the successive phases of 

the lacustrine history. 

Correlated with these data is a remarkably complete 

biologic record which sheds much light on the physiologic and physiographic ecology of Green River 

time. The fossil!3, which include a rather unusual 

assemblage of forms, are all characterized by the 

excellence of their preservation. The fish are numerous and famous as museum specimens. Bones of 

crocodiles and turtles are more common in the shore 

phases than has been supposed. More than 300 

species of insects from different parts of the formation 

have been described, and many more await study. 

Ostracodes are exceedingly abundant, but mollusks 

are rare except in a few of the shore phases. The 

flora is large and includes not only leaves but flowers, 

fruits, and seeds and aquatic as well as land plants. 

Fresh-water algae reefs are plentiful in parts of the 

formation and help to determine the form ratio of 

the Green River lake~ and their relative stability at 

certain stages. 

Supplementing this large and varied record of the 

life of the Green River epoch is the remarkable microscopic flora and fauna of the oil shale. These organisms exceed even the megascopic fossils in excellence 

of preservation. They include many algae, fungi, · 

spores, and pollens and a few rhizopods. 

With all this material available it has been possible 

to reconstruct in some detail the geologic history of 

the formation as a whole and to draw a fairly complete 

picture not only of the conditions within the lakes but 

also of the environment. 

LOCATION AND EXTENT OF THE AREA 

The index map (fig. 1) shows the distribution of all 

of the Green River formation in Colorado, Utah, and 

Wyoming except some small exposures of lake beds 

in the vicinity of Juab and Manti, Utah, whose identification with this formation is still uncertain. This 

report treats in particular certain phases of the formation in Colorado and U tab exclusive of that in 

Moffat County, Colo., north of the Yampa River, 

which, together with other specific parts of the formation in Wyoming, has been described elsewhere.1 

The Green River formation of Colorado and Utah 

was laid down in the ancient Uinta Lake and now 

occupies two large, shallow structural basins~the 

Piceance Creek Basin in Colorado and the Uinta Basin 

in Utah. A narrow isthmus of the formation connects 

these two large areas. South of the Colorado River 

there are two isolated areas of the formation in Battlement and Grand Mesas. The rocks in these mesas 

were once continuous with those north of Colorado 

River and indicate a former considerable southward 

extension of Uinta. Lake. 

The area in the Piceance Creek Basin where the 

Green River formation is now exposed is about 95 miles 

long from north to south and about 48 miles wide. In 

the Uinta Basin the formation is exposed in a strip 

about 135 miles long from east to west and about 46 

miles wide at the widest place. 

1 Sears, J. D., and Bradley, W. H., Relations of the Wasatch and Green River 

formations in northwestern Colorado and southern Wyoming: U.S. Geol. Survey 

Prof. Paper 132, pp. 93-107, 1924. Bradley, W. H., Shore phases of the Green River 

formation in northern Sweetwater County, Wyoming: U. S. Geol. Survey Prof. 

Paper 140, pp. 121-131, 1926. 

1 
r-· 

2 ORIGIN AND MICROFOSSIJ,..S OF OIL SHALE OF GREEN RIVER FORMATION 

PREVIOUS GEOLOGIC WORK 

Peale 2 explored the region between the Colorado and 

Gunnison Rivers and recognized in Battlement and 

Grand Mesas the Green River "group, " which then 

included the Green River and Wasatch formations. 

He expressed the belief of Hayden, Cope, and Marsh 

that the lakes of the Green River and Uinta Basins were 

ment Mesa and Thompsons, Utah. White and End~ 

lich 4 mapped the Uinta, Bridger, Green River, 

Wasatch, and older formations in the White River 

drainage basin from a point near Ouray, Utah., to the 

head of the river. This map is good for the area along 

the White River but very inaccurate for the side 

streams. Both White and Endlich 6 described the 

FIGURE I.-Index map showing the distribution in Colorado, Wyoming, and Utah or the Green River formation (shaded areas). Adapted chiefly from Winchester, 

D. E., U.s. Oeol. Survey Bull. 729, 1923, and the writer's unpublished maps 

contemporaneous and probably connected by a river. 

Two years later Peale made a good reconnaissance 

map 3 showing the distribution of the Green River, 

Wasatch, and older formations in the area drained by 

the Colorado River and its tributaries between Battlet Peale, A. 0 ., U. S. Oeol. and Oeog. Survey Terr. Ann. Rept. for 1874, pp.148, 

156, 160-161, 1876. 

'Peale, A. C., U. S. Oeol. and Oeog. Survey Terr. Ann. Rept. for 1876, pl.l1; 1878. 

Bridger and Uinta formations. They regarded the 

thick series of sandstone beds at the base of the 

Bridger formation in Utah as a part of the Green 

River formation. Peale 6 measured · several sections 

of the Green River formation between the head of Roan 

• White, C. A., and Endlich, F. M., idem, pl.. 2. 

a Idem, pp, 35-37, 82-86. 

a Idem, pp, 184-185. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLA'l'E 2 

A. VIEW UP A SMALL TRIBUTARY OF CLEAR CREEK, GARFIELD COUNTY, COLO. 

cliffs made by the principal oil-shale group of the Parachute Creek member of the Green River formation. The photograph was taken approximately from the horizon of the "mahogany ledge." Pholograph by D. E. Winchester. 

B. BEDDING PLANE OF BROWN ORGANIC MARLSTONE COVERED WITH LARGE SPINOSE FLY LARVAE, LITHOHYPODERMA SP. 

Natural size. 
LABORATORY WORK 

Creek in Colorado and Bitter Creek in Utah. He also 

described 7 several asphalt exudations in association 

with sulphurous springs in the head of Asphalt Wash. 

Many years later Gale 8 made an excellent reconnaissance map showing a. part of the Green River 

formation along the eastern margin of the Piceance 

Creek Basin. 

In 1913 Woodruff and Day 9 also made a reconnaissance survey of a part of the area occupied by the 

Green River formation in Colorado and Utah. In 

1914-1917 Winchester 10 studied the Green River 

formation in Colorado in considerable detail, mapped 

not only the base of the formation but also the principal oil-shale · zone, measured many stratigraphic 

sections, especially in the oil-shale zone, and sampled 

many 0~-shale beds. In Utah in 1918 Winchester 

mapped only the principal oil-shale zones, measured 

several stratigraphic sections, and sampled the oil 

shale. 

FIELD WORK 

The writer had the opportunity in 1921 but more 

especially in 1922, while assisting J. D. Sears, of th~ 

United States Geological Survey, to map and study 

the Green River formation in Moffat County, Colo~, 

both north and south of the Yampa River, and in part 

of southern Sweetwater County, Wyo. In 1923 the 

writer, assisted by Carle H. Dane, also of the Geological Survey, mapped and studied some shore phases of 

the formation in northern Sweetwater County. l'he 

results of that study have already, been published.11 

In 1924 the writer .~Pent the first two weeks in 

June studying samples of the bottom deposits and the 

plankton of Goose and· Klamath Lakes, in southern 

Oregon. These samples were examined in the field 

with a portable microscope and studied later in t.he 

office with more care. From the middle of June to 

the end of August, .1924, the writer was assisted by 

Charles E; Erdmann, of the Geological Sti.rvey. 

During that time most of the Green River formation 

between the Yampa and White Rivers in Rio Blanco 

and Moffat Counties, Colo., was mapped, and the 

conditions of sedimentation in that area, along the 

White River as far west as Yellow Creek, and· also 

along Piceance and Parachute Creeks were studied. 

Fossils and specimens were collected particularly from 

Hay Gulch and Piceance, Yellow, Greasewood, and 

Parachute Creeks. At the end of that season a few 

days were spent in examining the Green River formation just north of Watson, Utah. 

7:£>eale, A. C., op. cit .• (1878), p. 175. 8 Gale, H. 8., Coal fields of northwestern Colorado and northeastern Utah: U. B. 

Geot' Survey Bull. 415, p, sa, pls. 10, 18, 1910. 

o Woodruff, E. 0., and Day, D. T., Oil shale of northwestern Colorado and north· 

eastern Utah: U. B. Geol. Survey Bull. 581, pp. 1-21·, 1915. 

te Winchester, D. E., Oilshale.ofthe Rooky Mountain region: U, B. Geol. Survey 

Bull. 729, 1923. 

u Bradley, W. H., Shore phases of the Green River formatioa in northern Sweet- water County, Wyo.: U. B. Geol. Survey Prof. Paper 140, pp. 121-131, 192ft. 

3654~31--2 

In 1925 the writer and his assistant R. D. Ohrenschall made a stratigraphic study of the Green River·"· 

formation t. six critical localities in . the Uinta ~d.·, Piceance C ek Basins. These localities are shown on 

Figure 1. t each place a minutely detailed section 

was measur4d and a particular search was made for all 

possible features that wo\il.d assist in the interpret&.·-.. tion of the !formation or that would be of value for 

correlation. 1 Each section, except the one on tht:( 

north side of Minnie· Maud Creek near the Duchesne- · 

Uintah courl.ty line in Utah, is complete, so that the 

fossil collections and distinctive lithologic facies are 

accurately lpcated in the formation. In addition to 

this detaile<:J. work they made several reconnaissance 

trips to oth~r parts of the Uinta and Piceance Creek 

Basins for c~mparative study and also spent two days 

studying thl' plan. kton and bottom d. eposits of Little 

Salt Lake, ear Parowan, Utah. The field work on 

the Green , iver formation began that year July 15 

a.nd lasted qntil the end of September. ! 

LABOU.TORY WO:RK 

Several ~ars ago Charles A. Davis, late of the 

United States Geological Survey and the United 

States Bure~u of Mines, began to study the microscopic fossil$ found in the oil shale of the Green River 

formation. I He developed ~ fine technique in preparing the mat~rial for study, but his untimely death left· 

this work incomplete, and so far as the writer is aware 

none of the I microorganisms were ever described and 

only a few '\fere identified. In 1922 the writer undertpok to. expalnd and complete this study, and since then 

about half o, each winter has been devoted to a. microscopic stud~ of the oil shale. Particular emphasis has 

been place~ upon the description and classification 

of the microfossils and an inquiry into their significance 

in the orighl of the ~oil shale. Much of the remainder 

of the writer's time in the office has been spent in a 

study of th4 literature relating not only to the origin 

of oil shale ~nd related sedimentary rocks but also to 

limnology ap.d hydro biology. The results of recent 

'work on org~nic lacustrine ooze have been very useful 

in the internretation of oil shale. 

The Davi$ collection of more than 160 thin sections 

and 176 phptomicrographs formed the nucleus with. 

which the writer began the study of the microfossils 

found in th' Green River oil shale. No notes of any 

kin~ accompanied this material, many of the thin 

sections were either unlabeled or marked with symbols 

that had n~ meanll!g, and all the photomicrographs 

were unlabe~ed except a few of pollens and spores and 

one alga, w:tiich was erroneously labeled SpiMdina sp. · 

Later somel specimens were ·found whose envelopes 

bore a desc~p tion together with the letter symbols of 

the locality! from which came the material richest in 

microfossils~ All of Davis's photomicrographs repre-· 

I 

·.,. 
4 ORIGIN AND MICROFOSSILS OF OIL SHALE OF GREEN RIVER FORMATION 

sent specimens from this one locality. Subsequent 

study by the writer has considerably enlarged the 

collection of thin sections and photomicrographs. 

ACKNOWLEDGMENTS 

To David White belongs the full credit for pointing out that much of the oil shale of the Green River 

formation was derived from sapropel which accumulated in more or less saline playa-like lakes. The writer's 

paper that appeared in April, 1925/2 was intended 

simply as a diseussion of Henderson's paper qn the 

origin of the Green River formation. 13 It was prepared 

and had been accepted for publication before the 

writer had any knowledge of the contents of White's 

discussion of the origin of the Green River formation 

which was at that time in presa and which appeared in 

April, 1926.14 The writer is much indebted to Mr. 

White for his guidance during the early stages of this 

work and for his many stimulating suggestions during 

its progress. 

The writer wishes also to express his thanks to Prof. 

Gilbert M. Smith, of Leland Stanford Junior Uhiversity, who criticized that part of the report which discusses· the algae and who gave very valuable advice 

on the taxonomy of these forms. Drs. C. ·L. Shear 

and A. C. Longley, both of the Bureau of Plant Indus- . 

try, United States Department of Agriculture, have 

also helped the writer greatly. Doctor Shear examined many of the fungu~ spores and photomicrographs 

of them, and his suggestions regarding their possible 

relationships with living fungi have been incorporated 

in the writer's brief descriptive notes on those c.rypto.t 

gams. ·Doctor Longley examined some of the writer's 

photomicrographs of pollens and suggested pertinent 

literature that would assist in classifying them. Dr. 

H. G. Dyar, of the United States National Museum, 

was kind enough to examine some of the eyes of tninute 

adult insects which have been found in the oil shale. 

Dr. Charles T. Greene, of the Bureau of Entomology, 

has taken a keen interest in the fossil dipterous larvae 

which the writer has collected. He has made a careful 

study of the best specimens in the eolleetion and determined to what families and genera several of them 

belong. It is hoped that he will sometime be able 

to publish descriptions of some of these larvae. 

The writer is indebted to Prof. Carl 0. Dunbar, 

Prof. Adolph Knopf, and Dr. R. W. Brown, of Yale 

University, who read the manuscript and offered helpful criticisms. This report in essentially its present 

form was presented as a thesis in partial fulfillment 

of the requirements for the degree of doctor of philosophy at Yale University in June, 1927. 

u Bradley, W. H., A contribution to the origin of the Green River formation and 

its oil shale: Am. Assoc. Petroleum Geologish Bull., vol. 6, pp. 247-262, 1925. 

u Henderson, Junius, The origin of the Green River formation: Am. Assoc. Petroleum Geologists Bull., vol. 8, pp. 662-668, 1924. 

u Twenhofel, W. H., Treatise on sedimentation, pp. 289-304, 1926. 

Finally, the writer is grateful to his colleagues of the 

Geological Survey. W. W. Rubey gave considerable 

time to a thorough criticism of the manuscript, and 

both he and C. H. Dane have, from time to time during 

the course of the work, offered many helpful suggestions. 

TOPOGRAPHY AND DRAINAGE 

- That part of the Green River formation described in 

this report makes conspicuous highlands in central portions of a large intermontane basin inclosed by the 

Uinta Mountains on the north; the Williams Fork, 

Flattop, Elk, and West Elk Mountains on the east; 

remotely by the La Sal Mountains, Uncompahgre Plateau, and San Rafael Swell oil the south; and the W asatch Mountains on the west. Because the G:een 

River formation is resistant to erosion these .central 

highlands have in most places high and steep outwardfacing escarpments. 

Between the Colorado and Gunnison Rivers the 

rocks of the Green River formation make two high 

steep-sided tablelands, Battlement and Grand Mesas. 

The top of each mesa is about 10,000 feet above sea 

level, and between the high~st point on Battlement 

Mesa and the Colorado River near Rifle there is a 

difference in altitude of about 5,500 feet. Between 

the White and Colorado Rivers the formation makes 

a large plateau, which has a small extension north of 

the White River, known as the Gray Hills. This 

large plateau is entirely surrounded by bold ·outwardfacing bluffs. Along the south side, in the Colorado 

River Valley they are 3,000 tb 4,000 feet high. On 

the east and west sides the slopes are precipitous but 

not so high, and those along the White River are still 

lower, rising 1,200 feet or less from the river level. The 

extension of the plateau north of the White River is 

also bounded by precipitous slopes from several hundred to 1 ,000 feet high. The surface of the entire 

plateau slopes gently mward from the high rim 

toward the center of the basin. · 

The Green River formation in Utah makes a high 

monoclinal ridge, 8,000 to 10,000 feet above sea level, 

that extends from the Colorado line westward nearly to 

Soldier Summit. This ridge lies north of and roughly 

parallels the Book Cliffs and forms the southern rim of 

the Uinta Basin. The south side of the ridge is generally 

very steep, but the north side is a gentle dip slope. The 

Green River formation is exposed from this rim north 

approximately to the Duchesne and White Rivers. 

This high country comprises the East Tavaputs Plateau, east of the Green River, and the West Tavaputs 

Plateau west of the river. 

All the streams that flow over the rocks of the Green 

River formation have cut narrow, steep-sided valleys 

or deep canyons with precipitous walls. The upper 

parts of the streams that run into the Colorado River 

flow for several miles in hanging valleys. Short but 
STRUCTURE 

deep box canyons are characteristic of the streams 

draining the Green R~ver formation. (See pl. 2, A.) 

Most of the area of the fonnation in Colorado and 

Utah is drained by the Green River through either the 

Duchesne River or the White River. A part of the 

West Tavaputs Plateau is drained directly by short 

side streams of the Green River. In Garfield CountY, 

Colo., most of the area of the Green River formation is 

drained· by short tributaries to the Colorado River. 

The major streams of the region once flowed at 

higher levels on younger Tertiary rocks that covered 

this region, but they have sinre cut down through 

these rocks. They are not yet influenced by the 

structure of the older Tertiary and Mesozoic rocks 

through which they now flow, but their tributaries, 

especially in the Uinta Basin, seem to be well adjusted 

to the structure. (See pl. 1.) The tributaries to the 

Colorado River that drain parts of the Green River 

formation, on the contrary, are Iiot at all adjusted to 

the structure and are cutting back into high divides 

whose rocks dip away from the heads of the streams. 

STRUCTURE 

MAJOR FEATURES 

The structure of the Green River· formation of 

Colorado and Utah is simple. The formation occupies 

two large shallow basins-The Piceance Creek Basin 

in Colorado and the Uinta Basin in Utah. These are 

separated by a low anticlinal arch whose axis is roughly ·parallel .to the Utah-Colorado boundary line and 

a~out 15 miles east of it. 

In the southern part of the Piceance Creek Basin 

~nd in the extensions in Battlement and Grand Mesas 

the beds dip very slightly toward the north, usually 

at angles of less than 1°. On the west side of 'the 

basin the dips range between 1° and 2° E. near the 

head of Roan Creek and 7° or 8° E. or SE. near the 

White River. The earth movements that tilted up 

steeply the rocks of the Grand Hogback also affected 

the Green River beds along the eastern margin of the 

Piceance Creek Basin, wliere they dip 15°-27° W. 

However, the beds flatten abruptly basinward and a 

few miles from the rim dip 5° or less toward the west. 

Along the south side of the White River the rocks 

dip 5°-12° S., but there. also they flatten basinward 

a little way from the rim. 

North of the White River the Green River formation 

occupies a shallow and irregular syncline that ends at 

the north against the flank of Cross Mountain, a. 

dome on the eastward extension of the Uinta Mountain 

arch. Along the east side of this syncline the dips 

range from 4 ° to 23 °, generally west, but on the west 

side they are less steep, usually 1°-6° E. . 

In the Uinta Basin the rocks of the Green River 

formation are everywhere gently inclined except for :a 

short distance along Raven Ridge, just west of 

Rangely, Colo., where they dip as much as 22° SW. 

All across !the southern rim of the Uinta Basin the 

beds dip 2f-8° N. Along the north side of the .Uin'ta 

Basin. the Green River formation does not crop out 

but is covered by an overlap of younger rocks, the 

Bridger and Uinta formations,. which dip gently n~rthward. The exact location of the axis of the Uinta 

Basin is n~t known, but it is probably 12 or 1.5 mile.s 

north of the Duchesne River. North of that axis -the 

rocks of t:q.e Uinta formation dip gently southward. 

MINOR FEATURES I • 

Near De~p Channel Creek, in _the southern part of 

Moffat County, Colo., there are two small and 

apparently. short faults, the only ones observed in 

the Green River ·formation in Colorado south of the 

Uinta MolUltains. Many small and very low folds 

are superithposed on the major structurai features, 

Most of these are mere undulations that can be defined 

only by instrumental survey. In the Uinta Basin in 

Utah there1 are several small anticlines in the vicinity 

of the Strawberry River and Indian Creek, the axes 

of which roughly parallel the major axis of the basin. 

Locally these folds have dips as high as .18° S. and 

15° N. They are cut by many small faults, most of 

which are nearly parallel to. the a."i:es of the folds. It 

is probable: that more detailed mapping in the Uinta 

Basin will disclose other minor structural features like 

these. 

A few miles west of Watson, Utah, there is a remarkable system of nearly parallel long, straight 

fractures which are approximately radial to the basin. 

Eldridge/5 :after remarking about the scarcity and 

small displacement of the faults in the Uinta Basin, 

says of these fractures: 

The basin is nevertheless the seat of a large number of most 

remarkable vertical cracks, now filled with the various asphaltites, from one-~ixteenth of an inch to 18 feet across, and in 

length from a few hundred yards to 8 or 10 miles. Their 

walls· are smooth and regular, they show but the slightest 

undulation, ~nd between the strata on opposite sides not 

even the sligrtest displacement can be detected. The cracks 

have a direction varying between N. 35° W. and N. 55°. W., 

and except for an occasional short, sharp transverse throw 

are peculiarly straight in trend. In some localities they 

appear to be approximately parallel with the strike of the 

strata and the trend. of the main flexures in the ranges and 

their foothill$; in others they cut the strata diagonally to the 

strike. On this account there is· not everywhere suggested 

a connection in their genesis with the broader structural 

folds. Again, none of the cracks show the irregularities of 

fissures form~d by the tearing asunder of strata along the 

axis of an aq.ticline, nor are there the slickensides occasioned: 

by the rubbing together of the walls in displacement. The 

termination Of a crack, ·either in outcrop or vertically, may 

occur by the gradual approach of its two walls but, as will 

appear subse~uently, may also take place from other causes .. 

Farther west, in Indian and Avintaquin Canyons 

and in the 1Ji.pper part of the Strawberry River Valley, 

u Eldridge, G. H., The asphalt and bituiilino~rock deposits. of the ·united 

States: u. s. Gool. Survey Twenty~cond Aim. Rept., pt. 1, p .. 339, 1901. 
6 ORIGIN AND MICROFOSSILS OF OIL SHALE OF GREEN RIVER FORMATION 

there are several sinillar but smaller fractures filled 

with elaterite. These trend about N. 25° E. and 

are also radial to the basin. 

The minor structural features very probably were 

incidental to the major down.warping and are therefore contemporaneous with· it. The small faulted 

anticlines in the Uinta Basin are near the axis of the 

basin, the site of greatest shortening, and are apparently the res~lt of compression. Straight vertical 

cracks radial to the basin and without differential 

movements of· the walls, such as the gilsonite veins 

near Watson and Dragon, Utah, and the elaterite 

veins in the vicinity of Indian and A vintaquin 

Canyons, are apparently due to purely tensional 

strains. These tensional strains may have been produced by hills and ridges on the pre-Tertiary surface, 

which hindered downwarp of the Tertiary rocks. 

AGE OF FOLDING 

The Uinta formation, of upper Eocene age, comprising the youngest rocks of the bacsin, took part in the 

major deformation, which is therefore post-Eocene. 

It may perhaps have been later than early Miocene 

and coincident with a partial collapse of the east 

end of the Uinta Mountain arch, which faulted and 

in · places strongly flexed beds of the Browns Park 

· formation that are probably of late Oligocene or 

early Miocene age. 16 However, there are at hand no 

evident me.ans of correlating these two movements, 

and consequently there appears to be no way to 

date the movement more· closely without much more 

information on the geologic and physiographic history 

of the Green River drainage system, especially in 

the Uinta Mountains. 

STRATIGRAPHY 

Although the purpose of this report is to describe 

the Green River formation of Colorado and Utah and 

in particular to interpret the physiographic, environmental, an_d climatic conditions that attended the 

deposition of its oil shale, the study would be incom~ 

plete if it did not also briefly describe and interpret 

the rocks that immediately underlie and overlie this 

formation. The rocks described here were formed in 

large structural basb:ts by essentially continuous 

aggradation ~hat lasted throughout the . Eocene 

epoch and probably longer. The Green River formation represents a predominantly lacustrine phase of 

the basin fillings and rests upon the Wasatch formation, of fluviatile origin. It is overlain by the Bridger 

and Uinta formations, which .are also dominantly 

fluviatile. 

LITHOLOGIC TERMS USED 

Certain descriptive terms applied to sedimentary 

rocks lack precision, and through continued loose 

18 Sears, .J. D., Relations of the Browns Park formation and the Bishop conglom· 

erate and their rOle in the origin of Green and Yampa Rivers: Geol. Soc . .America 

Bull., vol. 35, pp. 286-298, 1924. 

usage a few of them have a variety of meanings, the 

extremes of which differ widely. Because of this uncertainty the writer proposes to define those lithologic 

terms used in this report that have more than a single 

common meaning. 

Claystone and siltstone are both . massive finegrained rocks defined by the size of the predominant 

grains. According to Atterberg 17 clay-sized particles 

are 0.002 millimeter or less in diameter and silt-sized 

particles range from 0.002 to 0.02 millimeter. Grains 

larger than 0.02 millimeter fall into the several grade~ 

of sand and gravel. Wentworth's classification 18 differs 

from Atterberg's scale by including larger grains in 

the silt class. Wentworth puts the division between 

clay and silt at 0.004 millimeter and the upper limit 

of silt at about 0.062 millimeter. Although the name 

"claystone" is not intended to imply any particular 

mineralogy, it is likely that most of the crystalline 

grains less than about 0.004 millimeter in diameter 

belong to the general group of so-called clay minerals. 

But these so-called clay minerals are not by any means 

restricted in size and may be of such dimensions as to 

be properly classified as silt or even as sand. The 

adjectives "clayey" and "silty" imply an appreciable 

content of either clay or silt-sized particles. 

Mudstone is also a fine-grained massive rock, but 

it consists of an indefinite mixture of clay, silt,. and 

sand-sized grains, and therefore the term is more 

general than "claystone" or "siltstone." . Consequently the adjective "muddy" signifies a rock with 

an admixture of enough particles smaller than fine 

sand to change its general aspect. 

American usage of the term "marl" is very diverse. 

Dana 19 defined marl as 

a clay containing a large proportion of lime, sometimes 40 to 

50 per cent. If it consists largely of shells or fragments of 

shells then it is termed a shell marl. Marl is used as a fertilizer, 

and beds of sand and clay that can be so used are often in a 

popular way called marl. 

Perhaps this indefinite popular use has led to vague 

usage by American stud~nts of geology. Me:nill 20 

says that 

the name shell marl or merely marl is given to an illy defined, 

often arenaceous soft earthy rock consisting essentially of shell 

material in a more or less fragmental condition and usually 

intermixed with more or less clayey matter or· siliceous sand 

and silt. 

Pirsson 21 held the apparently unique view that 

"when a soil contains. a considerable quantity of calcium carbonate it is termed a marl." Despite this 

variety, most AmeJican textbooks agree that in com11 .Atterberg, .A., Die rationelle Klassifikation der Sande und Kiese: Chern. 

zeitung, vol. 29, No. 15, pp. 195-198, 1905. 

1s Wentworth, C. K., .A scale of grade and class terms for clastic sediments: Jour. 

Geology, vol. 30, pp. 377-392, 1922. 

19Dana, J'. D., Manual of geology, 4th ed., p. 79, 1896. 

20 Merrill, G. P., .A treatise on rocks, rock weathering, and soDs~ new ed., p. 128, 

1906. 

u Pirsson, L. V., and Schuchert, Charles, .A textbook of geology, pt. 1, 2d ed., 

p. 29, 1920, 
STRATIGRAPHY 7 I 

position a marl is a mixture of clay or mud and a rather 

large percentage of calcium carbonate. -Opinions on 

the induration and structure of marl are less definite, 

for some writers regard marl as a wholly unconsolidated deposit, whereas others regard it as a soft earthy 

rock, and still _others use "marl" more or less synonymously with "greensand. " 

European usage of the term "marl, " though not 

entirely uniform, is less diverse than American usage. 

De Lapparent 22 defines marl as a rock in which the 

clayey constituents are abundant and equal or exceed 

the quantity of carbonates. The rock may be dolomitic and may be rather hard. Rosenbusch 23 does not 

restrict the proportions of the constituents. He says: 

Marl and dolomitic marl are intimate mixtures of crystalline 

calcite, occasionally of dolomite, with clayey s1:1bstances whose 

character is not well known. * * * In such mechanical 

mixtures the individual constituents vary between the widest 

limits, and, indeed, they show transition forms between limestone 

and dolomite on the one hand and clays and sandstones on the 

other. 

The harder varieties of marl he calls marlstone. 

Many beds in the Green River fotmation not only 

have the chemical composition and n1ineralogy of 

marl, but their texture is intermediate between that 

of .mudston.e and ·limestone, so. that if they are not 

. designated by some single term they must be described 

by cumbers01ne groups of terms like "very muddy· 

limestone" or "very limy mudstone. " "~farlstone" 

appeals to the writer as a particularly appropriate 

.term to apply to these rocks. They ·are all fine grained 

arid rather dense, and they contain various proportions 

of organic matter. Their hardness r~nges from that 

of hard chalk to that of relatively pure, fine and close 

grained limestone. Their colors range from nearly 

white to chocolate-brown. 

Claystone, siltstone, mudstone, and marlstone, as 

the terms are here used, are all massive rocks. They 

may be homogeneous in color and texture, or they may 

show very pronounced bedding laminae, provided, 

however, there is no distinct tendency to part along 

these closely spaced bedding planes. 

"Shale,., is regarded as a structural term coordinate 

with "slate" as advocated by Lewis, 24 who says: · 

It implies no particular composition except so far as certain 

materials of fine texture lend themselves to the development of 

the characteristic structure. This structure, or fissility, may 

be defined as the capacity of clayey strata for splitting into 

somewhat uneven flakes, thin chips, and wedgelike fragments 

approximately parallel to the bedding. * * * Fissility is 

typically developed in most of the clay rocks of finer texture 

and in various unsorted mixtures, such as silty clay, sandy clay, 

and mud, and is commonly most conspicuous on weathered 

surfaces. 

u De Lapparent, A., LeQOns de ~trographie, pp. 376-378, 1923. 

2a Rosenbusch, H., Elemente der Gesteinslehre, 4th ed., revised by' A. Osa.nn, 

pp. 561, 563, 1923. 

"Lewis, 1. V., Fissility of shale a.nd its relations to petroleum: Geol. Soc. America 

Brill., vol. 35, p. 568, 1924. 

Althoug the term "shale" defines the size of the 

constituen particles of the rock only within a generJl 

range, it ust imply that a large proportion of tb.e · 

particles e . thin and flakelike. . ·Otherwise· the rock. 

could not be fissile. These flaky particles may httve 

been depo 'ted in that form or they may have grown 

within thel sediment during its compaction and solidification. tJ.'he characteristic particle sh~pe, therefore, 

may be o~· al or secondary. Consequently "shaly" 

is used her to modify such rock names as "marls tone" 

and "mu tone" to indicate that they have either a 

slight or a~ apparent fissility but yet insuffieient to be 

regarded a~ shale. _ 

"Paper ~hale" is the term applied to finely laminated · I 

claystones~ siltstones, mudstones, and marlstones that 

show a prqnounced tendency to part along the.· closely 

spaced be~ding planes. . This . tendency is probably. 

due in p~rt to an original structure, but it seems 

that it mtght be more or 1ess accentuated by the 

secondary I process of compaction. For ·example, if . 

for any re~son there was a concentration of minute 

flakes of aJ micaceous clay mineral, or any. other flat 

particles, ~t the top of each lamina, then compaction of 

the sedimept would induce there a parallel orientation 

of the flat 1 particles sooner than in other parts of the 

lamina. I~ so far as this parallelism is secondarily 

induced it lis virtually fissility. It might possibly be 

regarded as a special type of fissility, because it coincides exactly with the bedding planes. Actually paper 

shale consists of very thin laminae of nonfissile roek 

separated from one another by excessively thin laminae 

that are fi~sile. The origin of these laminae that give 

rise to the paper shale in the Green River formation is 

discussed :rhore fully in another report.23 

In accortlance with a recent decision 26 of the Secretary of thJ Interior, any shale that will yield oil when 

distilled wijl be regarded under the general mining laws 

as oil shal~. Although this definition is suitable for 

that purple, it is not precise enough to designate what 

most geol gists regard as oil shale, for it would also 

include mo t sorts of carbonaceous shale and also shale 

saturated {vith petroleum that can be almost wholly 

extracted iwith ordinary petroleum solvents. The 

writer ther~fore proposes the following definition: 

Oil shale! is a fine-grained sedimentary rock contain- · 

ing organi~ matter which was derived chiefly from 

aquatic organisms or waxy spores and pollen grains 1 

which is on~y slightly soluble in ordinary petroleum solvents, and ~f which a large proportion is distillable into 

artificial p~troleum. Despite the name most rich beds' 

of oil shalel in the Green River_f4rm.a.tlon could J.lQ.t .be I 

regarded strictly as shale. Instead they are more or less 

2; Bradley, W. Hl, The varves and climate of the Green River epoch: · U. S. Geol. 

Survey Prof. Pa r 158, pp, 1()()-103, 1929. , 

201. D. Free vs. G. L. Summers; Standard Shale Products Oo. vs._ -G. L. 

Summers, Sept. 130, 1927: Decisions of the Department of the Interior telating to 

public lands, volf 52 (in preparation). 

; ' 
8 ORIGIN AND MICROFOSSILS OF OIL SHALE OF GREEN RIVER FORMATION 

magnesian marlstones rich in organic matter. Nevertheless a few are shaly. On the other hand, many 

low-grade oil-shale beds are paper shale. By low grade 

is ~eant any oil shale that will yield less than 10 gallons 

of oil to the ton. This division between low and high 

grade oil shale is arbitrary and is adopted merely as a 

convenience in exposition. It is the same that the 

writer has used in his earlier reports. The character 

and~composition of the different types of oil shale in the 

Green River forn1ation are discussed fully on pages 22-

32, 36, 37. 

WASATCH FORMATION 

The Wasatch formation, of lower Eocene age rests 

upon rocks of earliest Tertiary age or older, in some 

places with distinct unconformity and in others with 

apparently transitional contact. Between theW asatchand the overlying Green River formation there is a 

transitional zone of variable thickness. 

According to Osborn, 27 the Wasatch formation of the 

Uinta Basin is characterized by fossils from the upper 

three of the life zones assigned by him to the lower 

Eocene epoch-the LambdOtherium·Eotitanops-Ooryphr 

odon zone, the Heptadon-Ooryplwdon-Eohippus zone, 

and the Systemodon-Ooryplwdon-Eohippus zone. The 

Wasatch formation of the Bridger Basin of Wyoming 

and Utah is lithologically almost identical with that 

of the Uinta and Piceance Creek Basins and separated 

from it by only about 13~ miles across the Axial Basin 

anticline in central Moffat County, Colo. In the 

vicinity of Evanston, Wyo., it is characterized by fossils fl'om the Heptadon-Ooryphodon-Eohippus zone. As 

indicated by the fossils of these life zones the Wasatch 

formation of the Uinta and Piceance Creek Basins is 

equivalent to that in the Bridger Basin. It is also 

correlative with the "Sand Coulee" and "Grey Bull" 

horizons of the Wasatch formation 'in the Big Horn 

Basin.28 

TheW asatch formation consists chiefly of variegated 

mudstone with a subordinate amount of friable gray 

or brown sandstone in irregular and. discontinuous 

lenses. Locally, however, regularly bedded sandstone 

is abundant. The mudstone displays a great variety 

of colors and shades, including drab, gray, green, 

yellow, buff, brick-red, pin~, mauve, maroon, lavender, 

bluish gray, brown, and black. Drab and pink or red, 

however, are the prevailing colors. Such colors occur 

.either in irregular zones or thin and rather persistent 

· beds presenting a banded aspect. The sandstone is 

:generally medium to coarse grained, poorly sorted, 

soft, and light gray or buff, but most of it weathers 

dark brown. Many of the lenses are massive, but 

some are cross-bedded or .ripple bedded. The more 

2; Osborn, H. F., The titanotheres of ancient Wyoming, Dakota, and Nebraska: 

U. S. Geol. Survey Mon. 55, p. 59, 1929. 

28 Granger, Walter, On the names of lower Eocene faunal horizons of Wyoming 

:and New Mexico: Am. Mus. Nat. History Bull., vol. 33, pp. 203-205, 1914. 

regularly bedded sandstone is prevailingly buff, though 

locally it ranges fro·m dark gray to almost white. 

Cross-bedding and ripple bedding are about as abundant in the regular beds as in the lenses. Conglomerate 

is locally plentiful near the base, and at a few places it 

occurs in thin zones throughout the formation. In the 

Wasatch Plateau limestone makes up nearly one-third 

of the Wasatch formation, but in most of the area considered in this report limestone is rare. 

The upper part of the Wasatch formation is exposed 

nearly everywhere adjacent to the outcrop of the Green 

River formation in Colorado and Utah except along 

the north side of the Uinta Basin, where it is covered 

by a wide northward overlap of the Uinta formation. 

The Wasatch formation makes consp\cuous and at 

places brightly colo.red badland cliffs or scars on the 

steep slopes of plateaus and buttes, particularly where 

it is sharply upturned, as along the Grand Hogback, 

just east of the Piceance Creek Basin. In the broader 

valley bottoms it weathers to low, well-rounded hills 

or isolated knobs that show badland scars in only a 

few. places. Along the eastern margin of the Piceance 

Creek Basin north of Rio Blanco the Wasatch formation contains very little sandstone but many thiD. 

zones of brightly colored chert and igneous-rock pebbles 

in a sandy mudstone matrix. Petrified 'Yood;- much 

of it waterworn, is ~lso abundant there. Southward 

from Rio Blanco lenses of channel sandstone. become 

more plentiful. In many of these the ·sandstone is 

coarse . grained or even gravelly and poorly sorted. 

Some are ferruginous. 

The thickness of the formation in northwestern 

Colorado is fairly uniform. A complete section measured at Price Creek post office, Moffat County, in 

1924, is about 3,500 feet thick. Gale 29 says that the 

Wasatch at Rio Blaneo is about 3,400 feet thick . 

.Another complete ':!ection about 10 miles northwest of 

Rifle, Col"o., measured by the writer in 1925, shows 

about 3,900 feet. According to Lee 80 the lower part 

of the Wasatch formation southeast of Grand Mesa 

is very conglomeratic but becomes less so toward the. 

west, passing from conglomerate to sandstone and 

variegated mudstone. 

The Wasatch formation thins decidedly toward the 

west side of the Piceance Creek Ba"in. C. E. Erdmann,31 of the Geological Survey, measured two com-

·plete. sections. of the Wasatch· between Debeque and 

the Fruita-Rangely Road. One along Hunter Canyon 

in sees. 21 and 16, T. 8 S., R. 100 W., Mesa County, 

Colo., is about 1,000 feet thick and includes at it':! 

base a few hundred feet of sandstone with some beds 

of conglomerate. The oth~r section, about 16 miles 

to the northwest, in the canyon of East Salt Creek, 

·29 aaie, H. s., Coal fields of northwestern- Colorado, and northeastern Utah: 

U.S. Geol. Survey Bull. 415, p. 82, 1910. . 

ao Lee, w. T., Coal fields of Grand Mesa and the West Elk Mountains, Colo.: 

U.s. Geol. Survey Bull. 510, p. 51, 1912. 

at Personal communication. 
'. 

STRATIGRAPHY 

in sec .. 15, T. 7 S., R. 102 W., Garfield County, Colo., 

is about 800 feet thick and consists chie:B.y of drab 

clay. Northwestward the formation apparently thins 

s.till more. Reeside 32 estimated the total thickness to 

be 400 feet near the divide between Douglas Creek and 

East Salt Creek, approximately on the arch that separates the Uinta Basin from the Piceance Creek Basin. 

The formation there consists mostly of drab mudstone 

with only a few thin bands of red. 

In the Uinta Basin the Wasatch thickens again. 

Spieker and Reeside 33 measured a section of it above the 

Book Cliffs a few miles west of the Green River and 

give a thickness exceeding 3,600 feet. As there are 

no measurements of the Wasatch formation between 

this locality and the Douglas Creek anticline, it is 

impossible to say how rapidly the formation thickens 

westward into the Uinta Basin. Spieker and Reeside 

also give a complete.section of the Wasatch "formation 

on Willow Creek, north of Castlegate, Utah, which is 

about 3,200 feet thick. 

In the Wasatch Plateau the same authors 34 found a 

lacustrine phase about 1,000 ·feet thick near· the middle 

of the Wasatch formation. It consists almost exclusively of dense gray limestone. 

GRIBW ~IR J'ORIU.TION 

The Green River formation of middle Eocene age, 

was named by Hayden 36 because of its excellent exposures in Wyoming along the Green River. The type 

locality of the formation is at the town of Green River, 

Wyo. Sections measured by Winchester 3

6 near 'that 

town, in Tps. 17 and 19 N., R. 106 W., show a thick-

·and at the type locality of the Green River formatio£!. . 

includes the Tower sandstone lentil. · 

AGE 

Osborn 37 assigns the Green River formation to. the · 

upper part of the lower Eocene, making it equivalent 

to the lowerY presian of the European section. ~errY 38 

believes tha.t the flora indicates a somewhat y unger · 

age and compares the Green River to the Clai orne 

and possibly also the lower part of the Jackson of the 

Gulf coast region. He at first regarded it as equivalent 

to the European Bartonian. More recently Berry 39 

has expressed the opinion that the Green River formation is to be correlated with the Auversian stage of the 

European section, thus making it a part of the middle 

Eocene of this country. 

LITHOLOGY 

The lithologic description. of the Green River forma~ 

tion is divided into two parts, covering the rocks east 

and west of Bitter Creek, Utah. This creek was 

chosen chiefly because it is a convenient fuie about 

midway between the detailed section near W ataon, 

Utah, and that near the Duchesne-Uintah county line~ 

Across the area between these localities the lithologic 

units of the -Watson section, except the principal oilshale zone, have not been traced. Partly also, however, the division was placed here because the Green 

River formation in the ·vicinity of Watson is much 

more like that in Colorado than that west of Bitter Cre~ ) 

ROCKS EAST OJ' BITTD CUEK, lJTAH 

ness of about 1,350 feet. These sections include the For convenience of description and interpretation 

Tower sandstone lentil, 125 to . 245 feet thick, at the the rocks of the Green River formation in the eastern 

top. · Most of the formation at the type locality con- area have been divided into four members-the 

sists of fip.ely laminated marlstone, some of which is Douglas Creek member (at the base), the· Garden 

oil shale. There is. a basal unit of limy or sandy shale Gulch member, the Parachute Creek member, and 

and marlstone that weathers buff or gray-buff. This the Evacuation Creek member (at the top). (See 

is the Tipton shale member. Overlying the Tipton pis. 7 and 8.) The stratigFaphic relations of these 

is the Laney shale member, which makes rip most of members in different ·parts of the Piceance Creek 

'the formation there. The Laney shale member can Basin and in the extreme eastern part of the Uinta 

be divided into two nearly equal units, of which the Basin are shown diagrammatically in Plate 3. These 

lower contains more marlstone and sandstone than members persist throughout most of this area, though 

.the upper and weathers a rather somber gray. The they vary in thickness from place to place and lose 

upper unit is nearly all finely laminated marlstone, their identity where they merge into a shore facies. 

shale, and oil shale and weathers stark white.· A thin Each member represents more or less widely divergent 

but very persistent buff zone separates the two units. · , conditions of deposition front those below and above. 

The Morrow Creek member, nearly all crudely bedded 

sandy and limy shale or shaly marlstone that weathers 

yellowish brown, forms the upper part ef the formation I 

u Reeside, J. B., jr., personal communicatiQn. 

n Spieker, E. M.,.and Reeside, J. B., jr., Cretaceous and Tertiary formations of 

. the Wasatch Plateau, Utah: G6(!1. Soc. America Bull~, vol. 36, p. 440, 1925. 

DOUGLAS CREEK ·MEMBER 

The rocks making up the high ridge which separates 

the drainage basin of West Douglas Creek from that 

of Trail and East Salt Creeks are typical of the basal 

u Idem, pp. 440, 448-449. . 37 Osborn, H. F., op. cit., p. 66. 

»Hayden, F. V., U.S. Geol. and Geog. Survey Terr. Third Ann. Rept., p. 90, as Berry, E. ·w., The middle and upper Eocene floras of southeastern North 

1869. I America: U. S. Geol. Survey Prot Paper 92, p. M, 1924. M Winchester, D. E., Oil shale of the Rocky Mountain region: u.s. Geol. Survey · :9 Berry, E. W., Flora_and ecology ofSO-calle<I'Brfdger l:ieds·ofWind'Bivei' Ba.'Stn, 

Bull. 729, ~P· 124-126, Ul23. Wyo.: Pan-Am. GeologlSt, vol. 44, p. 360, 1925. . 
I 

10 ORIGIN AND MICROFOSSILS OF OIL c SHALE OF GREEN RIVER FORMATION 

part of the Green River formation east .of Bitter 

Creek. . Because this group of beds, which constitutes a distinctive and mappable unit, is so thick and 

so well exposed at the head of Douglas Creek, especially 

in the east half ofT. 5 S., R. 102 W., Garfield County, 

Colo., the writer proposes to call it the Douglas Creek 

· member of the Green River formation. (See pl. 8.) 

The heds of this member are characteristically 

buff or yellowish brown and in most places contrast 

markedly with the underlying drab or variegated 

mudstone of the Wasatch formation and the overlying gray ·or bluish-gray marls tone and oil shale. 

The member ra11ges in thickness from about 200 feet 

~n Piceance Creek to nearly 800 feet near the head 

of Trail Creek. It diffeTs from the bulk of the formation in having relatively large proportions of sandstone, limestone, algae reefs, and oolite. Moreover, 

the marlstone and shale beds are notably different 

from those in other parts of the formation, as many 

of them are silty and interbedded with very fine grained 

sandstone. The amount of oil shale is negligible. 

The bedding is regular in general, but within the 

beds and on the bedding planes there are many small 

irregularities. Ripple marks of both oscillation and 

current origin 40 are plentiful, but oscil!ation ripples 

predominate, and most of the current ripples are 

nearly symmetrical. Sandstone and siltstone beds 

are locally ·cross-bedded through a small vertical 

range. In a few places ostracode-bearing limestone 

and oolite beds also are cross-bedded. Other small 

irregularities such as minute faults, variations in 

thickness of individual laminae, and contortion by 

differential compaction of thin laye:rs also occur in 

the sandy shale and mudstone. These are accompanied by undulating bedding planes. Mud cracks, 

curls, and edgewise conglomerate occur but are not 

nearly so abundant as higher up in the formation. 

Mudstone lumps of various shapes are more plentiful 

in the Douglas Creek member than elsewhere in the 

Green River formation. In a few places well-formed 

oscillation ripples were covered with a thin film of 

yellow mud, which in turn was distinctly mud cracked. 

Ostracode-bearing shale and madstone are characteristic rocks· of the Douglas Creek member and in 

many places are associated with oolite .. Locally 

ostracodes make up considerable masses of rock. 

Gastropods and pelecypods are also locally pl~ntiful 

but are not so characteristic of the basal· member 

in this area as west of Bitter Creek or in Wyoming. 

Vertebrae, fin, rays, and other fragments· of small 

fish skeletons are surprisingly abundant in the southwestern part of the Piceance Creek Basin. Scattered 

pieces of turtle carapaces ·and crocodiles occur near 

the base of the Douglas Creek member at the""north 

to Bucher, W. H., On ripples and related sedimentary surface forms and their 

paleogeographic interpretation: Am. Jour. Sci., 4th ser., pp. 141}-210, 241-269, 1919. 

end of this basin. Fragmentary plant ·remains, 

mostly stems and ribs of leaves, occur rather spa:ribgly 

but uniformly distributed through the member. 

GARDEN GULCH KEMBER 

In most places east of Bitter Creek the transition 

upward from the Douglas Creek member is abrupt and 

marked by a change from yellowish brown or buff to 

light gray, as well as by a distinct change in lithology. 

The overlying member will be designated herein the 

Garden Gulch member because it is so thick and so 

fully exposed in the bluffs near the mouth of Garden 

Gulch, a short gulch tributary to Parachute Creek in 

sees. 7 and 8, T. 6 S., R. 96 W., Garfield County, Colo. 

(See pl. 7.) The rocks of this member weather either 

to a smooth slope or to one interrupted only by low, 

rounded, and discontinuous benches. Its topographic 

expression is thus noticeab~y different from that of 

either the Douglas Creek member, which makes steeper 

slopes broken by low but precipitous ledge.s, or the 

overlying oil shale bearing rocks, which generally make 

steep and rather high but. broken cliffs. (~e pl. 4, A.) 

The tlli.ckness of this member ranges from a little more 

than 200 feet in Hells Hole Canyon, near W. atson, 

Utah, to about 700 feet in the Parachute Creek Can~ 

yon, north of Grand Valley, Garfield County, Colo. 

Paper shale with discrete lamintie less than 1 millimeter in thickness, many to be measured in a few 

hundredths of a millimeter, is the characteristic feature 

of this second member of the Green River f()rmation. : 

Shale of this type constitutes 20 to about 40 per cent of 

the member, and is one of the most remarkable rocks · 

of the formation. It occurs in unbroken units 20 to 70 

feet thick, aggregating thousands of monotonously uniform, paper-thin layers, each sharply separated from · 

the next. Many of these paper-thin layers are lowgrade oil shale and are surprisingly flexible. Their 

flexibility increases with their content of organic matter. Some of the paper shale will yield niore than 15 

gallons of oil to the ton upon distillation. Such shale 

is dark chocolate-brown on the fresh surface but 

weathers gray. The leaner paper shale is buff or graybuff ~nd weathers lighter gray or buff. Outcrops of 

the paper shale resemble piles of deckle-edge paper. 

(See pl. 4, B.) 

Units of paper shale are intercalated with somewhat 

thicker units of flaky shale, which is also thinly but 

much less distinctly laminated. The greater part of 

. the Garden Gulch member consists of flaky shale and 

more thickly laminated marlstone, some of which is 

shaly. Most of the marlstone is light gray or buff and 

weathers yellowish. Other limy deposits, however, 

such as oolite beds anrl: algae reefs, are few ~r absent. 

Locally there are a few beds, several inches to a foot 

thick, of pale greenish-gray mudstone that contains · 

an abundance of marcasite lenticulas and concretions. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 3 

~---~--39.5 rriiles----~-- !---- tsmile s--~-0------------- 74.5 miles ----------------->!.,....----------52 miles ----------~*'------ 38miles ------~>k----------· 

sand 6 7 

52 miles ----------~f<;--- 16miles~ 

8 

Piceance Creek, 

Colorado 

9 r. · ·· 1 tlridian Canyon IJtah 

Saline phase 

., / 

I 

I 

z Gate Canyon 

Utah 

3 Duchesne -Uintah County line,Utah 

500 

- --

-?-

250 0 

----

Vertical scale 

500 1,000 

4 

Canyon of White River near Watson, Utah 

phase 

Upper oil-shale group 

:fi"-J'--.c----- Tra ns1bonal beds 

Lower oil-shale group 

1,250 Feet 

Horizontal scale 10 s o 10 20 30 40 Miles ~~~--~--~l---~--~ 

Trail Creek divide and Cathedral Creek, Co lorado 

Parachute Creek, 

Colorado 

~ 

b'-

o.D '"" 

~~ 

~E ro 

~ 

<' 

~} Fly larvae 

f 

• 

} Saline phase 

STRATIGRAPHIC RELATIONS OF THE SUBDIVISIONS OF THE GREEN RIVER FORMATION IN COLORADO AND UTAH 

Upper oil-shale group 

Deep Channel Cr ek, Colorado 
U. S . GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 4 

A. VIEW NORTH DOWN PICEANCE CREEK IN T. 1 N., R. 97 W., RIO BLANCO COUNTY, COLO. 

Above, three units of the Parachute Creek memher of t he Green River format ion (a, the lower pa rt of the upper oil- sha le group; b, the transitional beds; c, the lower oil-shale group); below (cl), t.hc Garden Gulch member. 

B. OUTCROP OF PAPER SHALE, SHOWING ITS FLEXIBILITY 

Photograph by D . E. Winchester. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 5 

A. UPPER PART OF EVACUATION CREEK MEMBER IN EAST WALL OF 

EVACUATION CREEK CANYON IN SEC. 8, T. 10 S., R. 25 E. SALT LAKE 

MERIDIAN, UINTA COUNTY, UTAH 

Shows numerous ellipsoidal cavities formed by the growth of bladed aggrega tes of nn unknown sa lt while the beds were still plastic. 

B. CLOSE VIEW OF CAVITIES FORMED IN A RICH OIL-SHALE BED BY THE GROWTH 

OF LARGE RADIAL AGGREGATES OF AN UNKNOWN SALT 

Note the distortion of the laminae above and below the cavities. Photograph taken on the west side of 

Piceance Creek, Colo., near its mouth. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 6 

A. CALCITE MOLD OF RADIAL AGGREGATE OF SALT CRYSTALS OUND IN SOME OF THE ELLIPSOIDAL 

CAVITIES SHOWN IN PLATE 5, n 

B. SALT CRYSTAL CAVITIES IN A BED OF MARLSTONE SUGGESTING INTERLOCKING PLATES OF 

ANHYDRITE 
11. S. GEOLOI.li CAL SURVEY P ROFESSIONAL PAPER 168 PLAT E 7 

L 

Q) 

.D 

E 

Q) 

E 

c 

Q) 

-o 

L. 

<0 

~ 

L 

(\) 

..a 

E 

Q) 

E 

.X 

Q) 

Q) 

L 

0 

If) 

!0 

-<lD 

:J 

0 

0 

B 

A 

Light chocoiate-brown laminated marlstone. 

Brownish-buff marlstone. 

Papery oil shale, 15-18 gallons. 

Papery oil shale, 15-18 gallons. 

Light-brown papery shale with marlstone lenses. 

Gray and but! platy marlstone and papery shale. 

Algae reef. 

Algae reef. 

Hard buff marlstone. 

Gray to but! laminated marlstane; plant fragments near top. 

Light-brown lamin!lted marlstone; plant fragments. 

Oolitic marlstone. 

Brown sandy shale. 

Brawn to gray finely laminated marlstone. 

Algae reef. 

Alternating beds or bard and soft gray marlstone. 

Algae reefs. 

Soft limy shale, papery and sandy. 

Sandstone, fine grained, laminated. 

Sort chlppy to flaky marlstone; silty near top. 

Sandstone with plant fragments. 

Brown to gray marlstone and papery shale. 

Hard platy shaly marlstone. 

Sort brown papery shale. 

Papery shale, 10-12 gallons. 

Hard limy marlstone, somewhat blocky. 

A.laae reef. B uff aandy limeiLone. 

Soft brown papery shale. 

Hard gray platy marlstone. 

Soft brown papery shale. 

Soft gray flaky to papary shale. 

Sandstone, fine grained, gray. 

Gray flaky marlstone and sandy shale. 

Sandstone, fi ne grained, reddish brown. 

Soft chocolate-brown flaky shale. 

Medium-grained light-gray micaceous sandstone, ripple bedded 

and cross-bedded. 

Soft brown flaky shale, with thin beds ol micaceous sandstone; 

plant remains near the base. 

Oollte. 

Sbaly sandstone and marlstone; plant fragments. 

Ripple-bedded sandstone. 

Soft gray shale and muddy sandstone. 

Sandy oolite. 

Chocolate-brown papery shale. 

Fin&-grained quartz sand; ripple bedded and cross-bedded. 

Soft brown papery shale. 

Algae reel. 

Sandy shale. 

Oolite. 

L 

Q) 

..0 

E 

Q) 

E 

.X 

Q) 

Q) 

L 

0 

()) 

+' 

:J 

..c 

u 

«l 

L 

«l 

Q.. 

L 

Q) 

...a 

E 

Q) 

E 

.X 

Q) 

Q) 

L. 

0 

c 

0 

+' 

<0 

:J 

() 

«< 

> 

w 

a. 

::J 

0 

L. 

'()I) 

Q) 

Cil 

.£. 

(JJ 

I 

0 

L. 

Q) 

a.. 

a.. 

::J 

«l 

c 

-~ (JJ 

+' "0 ·u; Q) 

c ..O 

Ill 

L 

f0.. 

::J 

0 

L 

'00 

Q) 

-en 

...c. 

(JJ 

0 

L 

(\) 

~ 

0 

_J 

Qj 

c 

ro 

(f) 

300±feet. 

~~~~~~ Brown and gray carbonaceous shale; many leaves and stems. 

Fine-grained sandstone. 

111ii~~~ Buff limy clay and marlstone. ~ Oil shale. 

B 

Brownish-gray laminated marlstone. 

Buff earthy carbonaceous clay; many leaves. 

Fine-grained ocherous limy massive sandstone. 

Organic marlstone and oil shale. 

Earthy clay parting. 

Organic marlstone, with numerous thin beds ol oil shale; a few 

small fly larvae. 

Oil shale, 35 gallons. 

Organic marlstone. 

Oil shale, 35 gallons. 

Oil shale, 35 gallons. 

Oil shale, 35 gallons. 

Oil shale, 35 gallons. 

Oil shale, 35 gnllons. 

Oil shale, 35 gallons. 

Oil shale, 35 gallons. 

Cbocolat&-brown laminated marlstone, 10 to 12 gallons. 

Oil shale, 20 gallons. 

Oil shale, 30 galbns. 

Oil shale, 20 gallons. 

Oil shale, 25-30 gallons. 

Oil shale, 25 gallons. 

Soft light-brown platy marlstone. 

Mahogany marker. 

Oil shale, 60-65 gallons; "mahogany ledge." 

Oil shale, 30 gallons. 

Stubby lenses of rich oil shale In papery shale. 

Oil shale, 40 gallons. 

Oil shale, 25 gallons.!"" 

D euse sbaly msrlstone, finely banded with brown organic vaned laminae; plant stems. 

Oil shale, 30-35 gallons. 

Oil shale, 20-25 gallons. 

Hard massive brown organic marlstone; fly larvae. 

Oil shale, 25 gallons. 

Oil shale, 25 gallons. 

Oil shale, 45 gallons. 

Oil shale, 25-30 gallons. 

Oil shale, 30-35 gallons. 

Oil shale, 20-30 gallons. 

Hard marlstone and oil shale, 25 gallons. 

Oil shale, 15-20 gallons. 

Dense marlstone banded with light brown; plaut remains near the base. 

Oil shale, 12-15 gallons. Limestone, finely and regularly bedded. 

Oil shale, 18-20 gallons. 

Dense marlstone banded with brown. 

Organic marlstone. 

Oil shale, 30-35 gallons. 

Dense marlstone banded with brown . 

Oil shale, 10-12 gallons. 

Light-brown flaky shale. 

Drab platy marlstone. 

Sandstone, shaly, faintly banded. 

Gray-buff laminated marlstone. 

Organic marlstone with adult Insects; 10-12 gallons. 

Oil shale, 25 gallons. 

Organic marlstone. 

Oil shale, 25 gallons. Oil shale, 15 gallons. 

Chocolate-brown laminated marlstone and oil shale. 

Papery oil shale, 15 gallons. 

Buff marlstone; gar pike scales. 

Oil shale, 30 gallons. 

Oil shale, 20 gallons. 

Oil shale, 15 gallons. 

Chocolate-brown organic marlstone. 

Oil shale, 30 gnllons. 

Papery oil shale, 25-30 gallons. 

Marlstone; gar pike remains. 

Oil shale, 15-18 gallons. Oil shale, 20-25 gallons. 

Vertical scale 

s~&k::Ja~~fF ~s3CoE=========~·o~====================~~~o~~=================2aoFeet 

COLUMNAR SECTION OF THE GREEN RIVER FORMATION MEASURED ON PARACHUTE CREEK, TPS. 5 AND 6 S., R. 96 W., GARFIELD 

COUNTY, COLO. 

Shows t he type sections of the Garden Gulch and Parachute Creek membert. 
U. S. GEOLOGICA l. S lJHVEY 

B 

Ftne-gra/ned burr 

sendstone. current ri"pple-be dded throughout 

reef's and beds or 

maor!sto,,e Bnd oolitic 

Ma•r/,;tone w1.th thin beds oF oolitic li"mestone 

F/ne-gre /ned buff sandstone 

pert massive ,ptJrt cross-bedded 

Hard silty mar/stone 

Algae reels and 

oolitic limes tone 

reef snd oolitic limestone 

gr&eniSh-gray shsiB 

greenish-9ray mar/stone 

Med1um_ to f/ne grtJined_ sand- stone,,npart massJVe,m part 

cross·bedded;con tains shale conglomerate 

Dense r;reeni:Sh-grey pyrittferous Sh(Jie 

with s~m& lenses 

Dens11 gr~enish-gray 

pyritrFerovs shBie 

reef 

Thin-bedded stJndy sh81£J tmd 

thi"n sandstone beds. Beds 

contljm mud curls, mud lumps, and fish bones and are mvd 

cr(Jcked and ripple bedded 

'-

~ 

"' % 

E: 

-<:: 

~ 

G 

<:; 

oolit/c hinestone. {; · merl:;tbnc \... 

rdcode shale or oolite 

0 

c 

sh"le - _20 g~llon tS 

marlt~r 

shlJie -IS gtJI!ons-salt molds 

l Mar/stone. mud cracks, 

r and salt molds 

J 

-Ot! shale; salt rnola's 

I} H~rd grtJy mar/stone 

-01"1 shlJie- IS lo 20 9allons 

shBIQ; insects and leaves 

Brown and gray m.:u--lslOI1e 

Oil shale -25 g8/lon5 -.salt molds 

j

l!!lllltPapery mor!st.one 

salt molds 

Od shdle -20 gallons 

Barren mar/stone, 

;,mestone,a.nd -thtn 

oil- shale beds 

-Od shale -15 tc.- 20 gallons 

J 

Brown rinely lamina ted 

mar/stone 

~~~~~~~ • Soft insects brown and shale plant with fragments adult

;;I -Sandy shale a} Moris tone 

--Oil shale - 15 galloas 

.-"-o- -~-,!O J }Mar/stone 

~==~ ~-Q,J shale -12 /o 15 gallons 

1

11111} "'"'"'"'" '"'-,,,, "'" 

-Oil shal< - 10 to 12 gallons 

i~;ill } E:(t:::"o:r.s;;:;,t;

7

:::;: --Oil shale- 35 gallon.s 

L~m,neted choco/(Jte - brown mar/stone 

Berren mar/stone and 

severe! beds of otlshale 

IS to 20 g~t/on~ 

shale - IS gallons 

Hard 1/ght -brown mar/stone' 

L'ght- brown low-grade oil shale. wi"th -t.hm 20-gBIIon 

o/1- shale beds 

Otl shale - 20 gallon5 

shale- IS gallons 

Hard chocolate-brow" 

lam/nated sha le w/th (fui) 

streak.$ of' Cfl-shale 

Oil shale - 25 gallone5 

Tt>p of bluff,--.__ 

approximately '-.. 

top of Green River form tion 

B 

Lam/nated chocolats-brown 

shale and thrn ooldtc ltmestone 

0 /1 shale - 12 to 15 9allon.s 

F/ne(y lam,nated light- brown shole wdh mud 

curls and mudcracks 

o,; shale - 10 gallon~ 

Laminated mar/stone 

Sandy ostracode limestone 

Fine-gr<uned cross-bedded ripple-bedded and muci- cracke"l sar1dsrone 

fJShbones 

. . Osctllatton-rtppled siltstone; f"t:Shbones 

Rather sof"t light- brown 

//my 5hale and finety lamin.ated mar/stone, few beds mud cracked 

end oscillat/on nj:Jpled 

Soft pBper shale 

~ 

"' 

~ E:. 

~ 

~ \j 

-~ " ~ <J 

~ l.lj 

~ q, 

"' " 

~ <.. 

"' ..... 

~ ·-~ 

c 

Vertical scale 

so~E3~~~3C~~~o~==============~5~o~============~'oo feet 

- Mud cracKs 

Rather sort chippy 

mar/stone 

Mar/stone with thin beds of" 011 shale 8nd ssnctstone 

Very th;n betf.ded s;;t y shaltJ cont/JI/')tnq vast numher.s oF fly lervae . 

Thin beds of oil .shale 

Hard lig!Jt-I'Jrown marf:.tone. platy or finely lomm<1ted, 

w1th several "thi/7 beds or 

od shale -10 fo 20c;allon<l 

Low- gr80'11 oil $h8" 

} P!oty marfsiDne 

L 

Ql 

.D 

E 

"' E 

.:£ 

Ql 

"' L 

Q 

c 

0 

->J 

m 

:J 

() 

<0 

> 

w 

L 

QJ 

..0 

E 

QJ 

E 

.:£ 

QJ 

QJ 

L 

l) 

QJ 

..... 

:J 

.L 

u 

Cll 

L 

rJ! 

L 

(]) 

..D 

E 

E "" 

.L 

() 

:J 

(!) 

c 

Q) 

-o 

L 

ro 

(!) 

L 

Q) 

..D 

E 

Q) 

E 

...IC 

(]) 

(]) 

L 

l) 

!() 

m 

ilo 

:J 

0 

0 

D 

Bridge r f ormation 

<ll 

IIJ 

u 

10 

4-

Q) 

c 

"' (f) 

Cbippy light-gray marlstooe, poor in organic matter. 

Oil shale, lenticular, 15-20 ga.Hons. 

T,igh t-gray platy marlstone. 

Oil shale, 15-20 gallons. 

Platy and sandy marlstone, poor iu orgaulc matter; o few thin beds of oil shale. 

Platy and chippy marlstone, rather poor in organic matter; a few thin beds ol rich oil shale and a lew thin bods ol altered volcanic ash. 

Platy organic madstone, with a few widely spaced thin beds of 

rich oil shale. 

Papery shale, marlstone, and 

mycetophilid larvae. 

lew thin beds of oil shale; 

Analcite bed; mahogany marker. 

Papery shale and oil shale. 

Mahogany ledge, 00 gallons. 

Oil shale, 3Q-35 gallons; analcite lenses. 

Oil shale, :m-35 ga.ll ons. 

Oil shale, 20- 30 gallons . 

Papery shale and marlstone. 

Analcite bed. 

Oil shale and organic marlstone. 

Oil hale; thick a nalcite lenses. 

Oro.yish-brown organic marlstone . 

Organic mnrlstone and beds of oil shale. 

Oil shale with analcite lenses. 

Organic marlstone. 

P:lpery 1Jhale. Car bonaeeuu• DflPt.TY •hale. 

Papery shale aud oil shale. 

Marly and ~andy shale, locally papery and with a. few thin beds of rich oil sba.le. 

Wa satc h fo rmat io n 

Oar-pike remains. 

Papery shale and oil shale. 

Soft brown shale. 

Shaly brown marlstone with a lew thin beds ol rich oil shale. 

Oil shale, 10 gallons. 

Brown shale, in part sandy. 

Papery shale, with thin beds ol oolite. 

Oil shale. 

Fin<>-grained muddy gray sandstone. 

Oolite, algae reef, and ostracode-bearing marlstoue. 

Gray sandy shale. 

Algae reef, oolitic and ostracode-bearing morlstone. 

Algae reef. 

Rather bard sandy gray shale. 

Algae reefs, oolitic and ostracode-bearing marlstone. 

Soft gray shalo. 

Lenticular algae reefs, oolilic and ostracode-bearing marlstone. 

Gray sandy shale and ripple-bedded sandstone. 

Light-gray fine-grained sandstone, with locul sandy mudstone 

phases. 

Algae reef and oolite. 

Sandy gray shale. 

Ostracode-bearing limestone. 

Soft brown flaky shale and fine-grained muddy sandstone. 

Oolite. 

Soft gray and brown shale. 

Low-grade oil shale. 

Soft brown flaky shale. 

Oolite and algae reefs. 

Vertical scale 

PROFESSIONAL PAPER 168 PLAT>O 8 

E 

Top of' plat eou approximately ~o p of Green Rive r formation 

I 

/ 

Soft light-gray to white sandstone, in part shaly 

Soft fine-grained gray to buff sbaly and muddy sandstone. 

Pitted a lgae reel. 

Soft gray shaly sandstone and siltstone. 

Algae reel. 

Fine-grained buff ripple-bedded sandstone. 

Ripple-bedded sandstone, with waterworn shale lumps. 

Buff fine·grained soft, almost unconsolidated sand. 

Sort gray shale. 

Fine-grained muddy sandstone. 

Soft gray shale. 

Fine·grained muddy gray sandstone. 

Soft gray shale . 

Algae reef. 

Solt limy gray shale. 

Hipple·bedded sandstone. 

Soft gray "sandy shale, with a few limestone beds. 

Cross-bedded sandstone. 

Soft gray shale. 

F ine-grained gray sandstone; many ostracodes. 

Soft gray sbale. 

Ripple-bedded sandstone . Ma.rlatone with o..tracoch:•. olit~ with 011\raeodn • 

Buff ripple·hedded sandstone. 

iill; ll Gray sandy shale and thin platy sandstone. 

Ripple· bedded sandstone. 

Gray flaky shale. 

Platy buff sandstone; many ostracodes. 

Soft gray sandy shale. 

Ripple-bedded sandstone. 

Soft gray shale. 

Hipplo·bedtlod sandstone. 

Soft gray shale. 

Buff current-rippled sa.ndstore. 

satidy shale, with a few lenticular sandstone)>eds. 

Soft fine-grained sandstone, in part:sbaly and ripple bedded . 

Irregularly bedded sandy-shale . 

Hegularly bedded so!t sandy gray shale, with a lew th in b ed• 

of muddy brown sandstone. 

Gently cross-bedded sandstone. 

Regular- beds of buff tine-grained muddy sandstone, alternat- ing with soft gray shale; some beds with oscillation ripples. 

Wasatch formation 

• Mud crtocks 

COLUMNAR SECTWNS OF THE GREEN RIVER FORMATION 

A, B, C, Composite section of the Green River formation. The lower part of the section (the type section of t.he Dou.glaa Creek member) was measured near the head ol Trail Creek. Garfield 

County, Colo., and tho upper pnrt was measured on Cathedral Creek, sec. 26, T. 3 S., R. 99 W., Rio Blanco County, Colo. D, Composite sec tion of which Lhe Douglas Creek and Garden Gulch m001her8 were measured in ReUs Hole Canyon. sec. 22, T. 10 S., R. 25 E. Salt Lake meridian, Uintah County, Utah, 

and the remainder in the canyon oC White River, ooo. 27, T. 9 S., R. 25 E .. Uin tah County, Utah. 

E, Section of the delta and shore facies of the Green River formation measured a few miles north o( Deep Cha nnel Creek in sees. 29 and 30, T. 4 N .• R. 95 W., Moffat County, CoJOt 
STBATIGJtAPHY . '' 1 :!l 

The Garden Gulch member contains only a few beds 

of fine-grained sandstone and siltstone, whioh in most 

·places are thin bedded and platy. Nearly all these 

beds are gray on the fresh surface but weather dark 

·brown. Some bear oscillation ripples, and a few show 

cunent-ripple bedding and cross-bedding. 

Interbedded with the low-grade oil shal~ and nearly 

barren flaky and platy s)lale are a few thin elongate 

lenses of rich, massive oil shale, some of which are 

noticeably pyritiferous. Most of these lenses are less 

than 1 inch hick and 10 to 100 feet or more in length. 

In the northern part of tlie Piceance Creek Basin the 

Garden Gulch member includes several massive beds 

of oil shale 1 to 6 feet thick that may yield 15 gallons 

or more of oil to the ton. · 

Mud cracks are more abundant in this member than 

in any other part,of the formation east of Bitter Creek. 

In the vicinity of Parachute and Cathedral Creeks, 

Colo., there are hundreds of closely spaced layers that! 

are mud cracked. Mud cracks are less numerous in 

the section st1.1died along the White River in Utah. 

On Piceance Creek, Colo., the Garden Gulch member 

was not examined for them. Near the head of Cathe-

, dral Creek mud cracks were noted in the troughs of 

large, sharp-crested oscillation ripples. In the more 

limy shQle and sandy madstone beds there are many 

mud curls but few edgewise conglomerates. Some of 

the oii-shale beds·show'mosaic brecciation. The term 

"mosaic breccia" is d~ed on .page 28, and in that 

part of the report the structure and significance of the 

·shal~ breccias are discussed. 

Os·tracodes occur only sparingly in this member in 

thin limestone or lean paper-shale beds. Garpike 

scales are not numerous, and only a few skeletons of 

small fish were found. A few plant remains, mostly 

-stem impressions and leaf fragments, ·were found in 

the sandstone and siltstone. 

PARAC8UTE CREEK MEMBER 

The member next above the Garden Gulch member 

is distinguished from other parts of the formation by 

its content of oil-shale beds. It contains all the large 

groups of rich beds, most of the jndividual rich beds, 

and a very large proportion of the low-grade oil shale. 

As the oil-shale facies of the Green River formation 

reaches its maximum thickness and probably also its 

maximum richness in the vicinity of Parachute Creek, 

Colo., it seems particularly appropriate to name this 

· unit the Parachute Creek member. This member 

ranges in thickness from about 175 feet in the vicinity 

of Watson, Utah, to a little more than 1,000 feet in 

the vicinity of Parachute Creek. It is predominantly 

a cliff-forming unit, and its. top is marked by a soft 

limy sandstone which is conspicuous because of its 

bright ocherous color. This sandstone makes the top 

of the highest cliffs in the canyon of Parachute Creek 

and its tributaries. For convenience of description 

and discussion the 'oil-Shale -beds of the Parachute 

Creek member have bt}en grouped into three l.U'1i~· 

designated here the lower oil-shale group, the tr~J'.ilfritional b{\ s, and the upper oil-shale group. (See-pl.:; 7.) 

Lower il-shale group.-The lower oil-shale groUp is 

not a ve clearly .defined lithologic unit, -but, as its 

rocks ind cate different conditions of depositi0,n from 

those w ch produced the beds above and .below, it· 

iB a usefl unit in discussing the origin of the formation , 

and its g ologic hi'3tory. It is. also a unit of· eeo:aoude . · 

interest, s it contains a considerable quantity of oil 

shale. e group i~ determined by its greater content of il-shale beds with an estimated potential 

yield of ore than 10 gallons of oil to the ton than 

occurs in either the inember just below or the b~s 

just abo . East of Bitter Creek the thickness of the 

lower oil shale group ranges from about .45 feet- to 

nearly 20 feet, and the proportion of oil shale ranges 

from ab ut 9 per cent to a little more than 30 perv 

cent. T e percentage of oil shale in this group is 

roughly roporHonal to the total thickness of the 

group. 

In mo t of the Piceance Creek Basin the lower oilshale gr up makes a. steep cliff that is prevailingly 

light bu or yellowish gray. The oil-shale beds, which. 

weat~r luish gray, give the cliff a faint color band- · 

ing. t AI ng the White River, both in Utah and. in 

Col~i-ado the group is somewhat softer, perhapS ·beca~e of l~ss lime in· the shale, and- makes stepped. 

cliffs or 1 dges. (See pl. 4, A.) In these places where · · 

the rock are less limy they weather slate-gray rather , 

than b . · _ . i , :,. 

The o' shale that characterizes tb.e lower oil-shale~: 

group oc urs in beds ranging in thickness from a frac- 4> 

tion of a inch to about 8 feet. Most beds, however, 

are 1% 3 feet thick. The probable yield of oil 

differs fr m bed to bed, but few if any beds 3 feet or 

more thi ·k will yield more than 35 gallons to the ton, 

Nearly a 1 the beds over 1 foot thick have an estimated 

potentia yield between 10 and 25 gallons to the ton. 

Most of them are massive, but a few are papery .. or . 

have pa ery phases. The massive beds are nearly 

black or very dark reddish brown on the fresh surface 

and we her dark to light bluish gray. Some beds 

show a ost no bedding, but most oi them are finely 

banded ith lighter-gray or yellowish-buff· layers of 

leaner a d more limy oil shale and appear laminated. 

The i egularities of bedding in the oil shale .range 

from s · ht undulations or loop bedding or discontinuity of the layers without any appreciable waviness 

to exces ive mosaic brecciation and intricate plicstie.ns 

due to ifferential compaction. (See pls. 14, A, and 

15, A.) Another common feature of the oil-shale beds · 

in this it is a speckled or finely mottled appearan-ce 

due to akes or short, very thill lenses of barren 

cream-c lored or ash-gray madstone. These limy lnclusions range in size from dustlike particles up :iQ 
12 ORIGIN AND 'MICROFOSSILS OF OIL SHALE OF GREEN RIVER FORMATION 

films or layers several inches long. Small lentil-like or 

irregular limy concretions, mostly dark yellowi8h 

brown, are associated with these inclusions but are 

distinct from them. Locally also there are black 

chert concretions in the oil-shale beds. Mud cracks 

are not plentiful. Edgewise conglomerate, mudstone 

lumps, mud curls, ripple marks, and ripple bedding are 

rare or absent. 

Some beds of oil shale are exceedingly variable along 

the strike, changing abruptly not only in thickness but 

also in structure, from massive to papery or the reverse. 

Locally, as along Piceance Creek, ·massive beds contain a great many lenses of papery oil shale, and some 

papery beds contain stubby lenses .of massive oil shale. 

Only one or two beds in the lower oil-shale group show 

distortion by the growth of large radial aggregates of 

salt that crystallized out in the plastic ooze that later 

hardened and became shale. 

Paper shale containing more or less organic matter is 

fairly abundant in this unit. It is most plentiful along 

Piceance Creek, where it makes up about 35 per cent 

of the group. There is less at Cathedral Creek and 

only about 2 per cent along the White River in Utah. 

The largest part of the group, however, consists of 

hard platy madstone and a smaller amount of somewhat softer flaky shale. In these materials most of 

the bedding is regular, but locally it is wavy or distorted by differential compaction, especially in the 

thicker beds. Much of this ·madstone contains a 

small ~,tmount of organic matter that ranges from a 

trace up to enough to yield a few gallons of oil to the 

ton. The organic matter may be uniformly distributed, giving the fresh rock a pale chocolate-brown 

color, or it may be distributed in layers that range in 

thicknes8 from mere films to some several -inches 

thick. Only a little of the madstone is sandy. 

Along the White River in Utah about 49 per cent of 

the lower oil-shale group consists of larvae-bearing 

beds. These are beds of oil shale that contain innum-

. erable remains of fly larvae, most of which are about 

an inch in length, although some are only about oneeighth inch and others nearly 2 inches. Some of the 

families and genera to which these larvae belong are 

given on pages 50-51. They cover nearly every bedding 

plane and in places are so abundant that they make 

glossy dark-brown layers or partings between the thin 

beds of rock. The beddmg planes bearing larvae are 

either regular or only slightly undulating and about 

0.1 inch apart. The larvae-bearing shale is chocolatebrown or gray-brown, and some of it is capable of 

yielding 8 to 15 gallons or more of oil to the ton. 

(See pl. 2, B.) 

Limestone makes up but a very small part of the 

lower oil-shale group. Most of it is muddy, hard, thin 

bedded, and platy and occurs in zones a few inches to 

several feet thick. It weathers cream-colored or 

ocher-yellow. 

Sandstone is rare or absent in the lower oil-shale 

group. Most of the beds are very fine grained or 

muddy and are interbedded with shaly mudstone. 

There are a few beds less than 5 inches· thick that are 

remarkably persistent. Closer study h~s shown that 

some of these are beds 9f volcanic ash that have 

changed to · zeolites. Probably many of the others 

are also beds of similar altered ash. 

Scales and partial skeletons of garpike (Lepidosteus 

sp.) are locally abundant in the low-grade oil shale of 

this unit. Ostracodes are also numerous in some of 

the limestone beds. At one place only were fragments 

of plant stems found. 

Transitional beds.-Between the lower and upper 

oil-shale groups of the Parachute Creek member is a 

relatively thin unit of transitional beds consisting 

predominantly of madstone that is nearly barren of. 

organic matter. (See pl. 7 .) These beds, however; 

indicate· ~ distinct phase in the history of the 

Green River lake. In most places they weather buff 

or gray and make either broken, steplike ledges or, 

where softer, smooth slopes interrupted by ledges. 

They range in thickness from 43 to about 118 feet. 

The marlstone of these beds is either hard and platy 

or somewhat soft and shaly. Much of it is finely 

laminated, and some is even papery. The madstone 

varies from place to place. In the vicinity of Cathedral Creek much of it is sandy, but along the White 

River in Utah it is only slightly sandy and rather soft 

and shaly. As in the rocks below, much of the socalled barren madstone and shale contains a small 

quantity of organic matter that is either distributed 

uniformly or segregated in layers. There are also a 

few beds of hard greenish-gray mudstone that contain 

considerable FeS2, most of which is marcasite. 

Oil shale occurs but sparingly in the transitional beds. 

Along Cathedral Creek there are se_veral beds of lowgrade oil shale which, curiously enough, are burned in 

a few places at the outcrop. On Piceance Creek the 

unit contains several very thin beds of rich massive 

oil shale. These are elongate lenses, rarely more than 

1 inch thick, and are intercalated with thick units of 

nearly barren marlstone. 

Limestone and sandstone occur locally in thin beds. 

Much of the limestone is muddy and slightly organic. 

The sandstone, which was found only in the Parachute 

Creek section, is fine grained, muddy, and limy. 

Some of the oil shale shows mosaic brecciation. 

Mud curls and waterworn fragments of shale and claystone occur locally in the sandy limestone. One sandstone bed showed contorted bedding and small ripple 

marks. No mud cracks were observed in this unit. 

Plant fragments and adult insects were observed in 

several places, but only one bed, along the White River 

in Utah, was found to contain fly larvae. 

Upper oil-shale group.-The upper oil-shale group 

contains most of the rich oil-shale be4s in the Green 
STRATIGRAPHY 13 

River formation and is therefore the object of greatest 

economic interest. (See pl. 7 .) It is a single unit that 

is coextensive with the formation in Colorado and Utah 

except for the shore facies in the Gray Hills north of the 

White River; It ranges in thickness from about 87 

feet along the White River in Utah to more than 730 

feet in the vicinity of Parachute Creek. In much of 

the area east of Bitter Creek the upper oil-shale group 

makes a high, nearly vertical cliff that is a conspicuous 

feature of the landscape. (See pl. 2, A.) This cliffforming tendency is due in part to the extreme resistance that the ma~ive beds of rich oil shale offer to 

weathering and in part to the fact that much of the 

low-grade oil shale of this group is very limy and hard. 

'The rocks weather prevailingly light gray or gray-buff 

but are more or less distinctly banded with dark bluish 

gray. 

Oil shale makes up 29 to 38 per cent of the group, and 

much of this will yield more than 20 gallons of oil to the 

ton. (See pl. 13.) Nearly all the oil shale is massive, 

but some weathers papery. The massive oil shale 

that will yield 20 to 25 gallons of oil to the ton occurs 

in beds from a fraction of an inch to 9 or 10 feet thick. 

These weather dark bluish gray to almost black, but 

are always finely lined with lighter-gray or buff lines 

that indicate thin bedding. The rock, however, is 

truly massive, as it breaks across these minute bedding 

laminae. On the fresh surface the high-grade oil shale 

is either very dark gray finely lined with black layers 

that have a satiny luster or en~irely black with a satiny 

. luster or dark reddish brown. 

The buff bands in the massive oil shale may be mere 

fragmentary films that occur but rarely or they may 

be an inch or more thick and make up an appreciable 

part of the ·bed. Most of them are slightly lenticular, 

and in many beds they are accompanied by small limy 

concretions. In some beds the concretions consist of 

bla~k chert. Locally . a great many beds of oil shale 

show mosaic brecciation, but in the vicinity of Parachute Creek that structure is rare. 

Some of the oil-shale beds are massive with papery 

phases. These beds also are finely laminated and contain thin limy layers and concretions. Locally they 

show mosaic brecciation. 

In addition to the richer beds there are some that 

range in potential yield from about 10 to 20 gallons of 

oil to the ton. Most of these beds are papery or platy, 

but some are massive and very hard. Their poorer 

quality is generally indicated by greater weight and 

yellowish-gray or distinctly yellow weathered surface. 

They are also lighter colored on a fresh fracture. 

East of Bitter Creek many of the oil-shale beds include ellipsoidal cavities ranging from about an inch 

_to nearly 5 feet in length, which originally contained 

salt,aggregates that apparently formed before the beds 

had completely hardened. The bedding is greatly distorted by these cavities. (See pl. 5, B.) Some have 

fillings of calcite that are evidently the molds of large 

radial aggregates of bladed salt crystals. (See pl. 6, A.)·. 

Very similar radial molds occur also in the low-grade 

oil shale of this group. These range from a fraction of 

an inch to several inches in diameter. Although some 

of the molds ar~ sharp, no satisfactory measurement 

could be made . to determine the original crystals, 

because they are so complexly intergrown. Molds of 

somewhat similar bladed crystals locally cover the 

bedding planes. (See pl. 6, B.) 

Contorted bedding is a common structure in the oilshale beds and also in some of the more massive marlstone beds in the Piceance Creek Basin. Along the 

White River in Utah it is rare. The folding in some 

beds is simple and very regular, the axial planes being 

nearly parallel to the normal bedding. In other beds · 

the folding is exceedingly compfex. (See pl. .14, A.) 

Minute faults also occur in the sam~ kinds of roc~s, 

but few were found closely associated with the beds 

that were contorted by differential compaction. Mosaic· brecciation is a distinct structure which is only 

very rarely associated with the contorted bedding. 

The remainder of the upper oil-shale group consists 

almost wholly of slightly organic marlstone·similar to 

that in the lower parts of. the formation but a little 

harder and somewhat richer. These leaner beds have 

been tested, and most of them will yield 4 to lO:gallons 

of oil to the ton. (See pl. 13.) Paper shale is not 

-plentiful in the upper oil-shale group. The quantity 

of limestone is insignificant, and there are only a few 

sandstone beds. These are thin but persistent, and 

some of them have been confused with beds of altered 

volcanic ash. 

Along the White River and in Hells Hole Canyon, 

north of Watson, Utah, the upper oil-shale group 

contains near its base two analcite beds. One bed 

consists of lenses one of which is about 40 feet long 

and 3 feet 3 inches thick at its thickest place. This 

lens comes into the middle of a. rather rich bed. of oil 

shale. The other bed is 13 feet above the .lenticular 

one and is abou't 4 inches thick. It seems to be fairly 

persistent, but 'it was not studied with particular care 

in the field, as its unusu~l composition was not recognized until specimens were studied in the office. It 

lies between two beds of low-grade oil shale but is 

strongly saturated with bitumen, which exudes from 

it in minute droplets. These peculiar zeolite beds, 

which are alteration products of volcanic ash, have 

been treated fully in another report.41 . .J 

Mud crackS are common in this unit, bu~ mud curls, v 1 

mudstone lumps, and ripple marks are rare. v 

Fly larvae are extremely abundant in the upper part 

of the upper oil-shale group on Parachute Creek, where 

there are more than 120 feet of larvae-bearing bed_s. 

Larvae were also found in this group along Piceance, 

41 Bradley, W. H., The occurrence an1 origin of analcite and m!lerschaum beds 

in the Green River formation: U. S. Gaol. Survey Prof. Paper 158, pp. 1-7, 1929. 
14 ,-·-·· . _9RIGIN AND MICROFOSSILS OF OIL SHALE OF GREEN RIVER FORMATION 

Creek and alo;ng- the White River in Utah. Adult 

insects, fragmentary leaves, and stem impressions also 

occur in this group, but they are not plentiful. 

EVACUATION CREEK MEMBER 

The uppermost lithologic unit of the Green River 

formation is the Evacuation Creek member, so named 

because of the excellent exposures on Evacuation 

Creek, Utah, and because in that locality it is a 

definite and readily mappable unit. (See pl. 8.) In 

the vicinity of Piceance Creek it is at least 84(} feet 

thick and is overlain by about 400 feet of beds that 

are dominantly sandy. No fossils have been found 

in these uppermost sandy beds, but they are lithologically and stratigraphically equivalent to the basal 

part of the Bridger formation of the Uinta Basin and 

are here . tentatively assigned to that formation. In 

the Uinta Basin the Evacuation Creek member is also 

a definite unit ,and along the White River in Utah is 

about 530 feet thick. 

This member consists chiefly of barren shale and 

madstone that weather brown or brownish gray, and 

in most places it makes gently rounded slopes broken 

by irreguiar and discontinuous ledges. Most of the 

shale is limy, thin bedded, and platy or irregularly 

chippy ~ Locally it is sandy\ In the vicinity of 

Piceance Creek more or less sandy marlstone makes 

up nearly one-third of the unit, and groups of fine to 

medium grained dark-brown sandstone beds alternate 

. with the marlstone. In other parts of the area east 

of Bitter Creek the marls tone of the unit is sandy, but 

sandstone is not so abundant. Locally there are thin 

beds of soft ·claystone. The Evacuation Creek member also contains a few thin beds of rich oil shale 

similar to .those in the Parachute Creek member. 

They are nearly everywhs:re too thin and too discontinuous to be considered workable deposits. 

Along Parachute Creek in Colorado and the White 

River in Utah the Evacuation Creek member contains 

nu~erous salt cavities. (See pl. 5, A.) Many of 

the'·oil-shale beds and a few of marlstone and muddy 

sandstone show contorted bedding, but shale breccias, 

mudstone lumps, and mud cracks are not so abundant 

as in the Garden Gulch member. At one place near 

the top of the section on the White River in Utah mud 

cracks were found on the upper surface of a bed of 

low-grade oil shale, and in another place mud cracks 

occur on a bed of sandstone marked with oscillation 

ripples. Several other beds of sandstone show oscil-

.~ lation ripples, but current ripples and cross-bedding ) 

\'--- ~re rare. 

Most of the finely preserved adult insects and leaves 

of the Green River formation came from the lower part 

of the Evacuation Creek member. Larvae-bearing 

beds are also abundant in the lower part. 

DELTA AND 8B9RE FACIES 

A shore and delta facies of the Green Riverformation 

constitutes the Gray Hills, north of the White River 

in Colorado. This facies is chronologically equivalent 

to most of the formation described above, but as none 

of the lithologic units recognized south of the White 

River have been surely identified north of the river, 

the exact equivalence of the facies is unknown. Two 

complete sections north of Deep Channel Creek are 

about 1,100 and 1,175 feet thick. (See pl. 8.) The 

shore facies in that locality is a littJe less than one-half 

as thick as the section measured about 15 miles farther 

south along Piceance Creek, and probably therefore 

some of the upper part has been eroded, although .the 

relative thinness of the shore facies is probably a1so to 

be explained by breaks in sedimentation. ' 

Nearly 50 per cent of the shore facies north of Deep 

Channel Creek is sandstone. The sandstone beds 

form groups 10 to 80 feet thick, which alternate With· 

shale units of about the same size. The shale is monotonously uniform, being either gray or. grayish-buff, 

soft, flaky, and prevailingly sandy. A little of it is 

hard and platy. The sandstone is less liniform. Its 

colors range from nearly white through gray, buff, and 

yellowish brown to dark reddish brown, but light-gray 

or buff hues predominate. Most of the sandstone is 

fine or medium grained, but locally it is coarse grained 

&nd contains varicolored chert pebbles· as much as 

half an inch in diameter. Gravel of this kind is rather 

plentiful near the base along the east face of the Gray 

Hills. In a few places there are also coal lumps in the 

sandstone. Most of the beds are massive and broadly 

lenticular. ·Some are regularly bedded, and a few- . 

the more muddy and harder beds-are platy. There 

is more ripple bedding than cross-bedding; oscillation 

ripples are only Inoderately abundant. Many of the 

beds of siltstone and muddy sandstone show mud· 

cracks, mud curls, and mudstone lumps, a few of 

which are waterworn. 

There are several noteworthy algae reefs in the upper 

part of this facies, but beds of limest.one and oolite 

are rare. Most of the limestone beds are brecciated. 

Ostracodes are abtmdant in some of the sandstone 

beds. The shale contains a few fragmentary leave3 

and stsms and locally also ostracodes and Estheria'! 

shells; Some of the thin limestone beds consist largely 

of gastropod shells. Scattered crocodile and turtle 

bones, garpike scales, and the bones and teeth of other 

fish were also found. 

Southward along the Gray Hills the shore facies 

changes gradually; shale, oolite, and marls tone become 

more abundant; the sandstone becomes finer grained, 

thinner bedded, and more muddy and limy; and the 

shale becomes less sandy and more evenly and dist.inctly bedded. Paper shale and thin beds of oil'shale 
'· 

STRATIGRAPHY 15 

also ~ppear. There is therefore a cornplete gradation 

southward from the very sandy shore and delta faciesv 

into the typical f~rmation of the Piceance Creek Basin. 

COLUMNAR SECTIONS 

Plate 7 shows a columnar section of the Green River 

formation that was measured in the canyon of Parachute Creek, Colo. It is a composite section measured 

in four parts. The base of the section is in sec. 4, T. 

6 S., R. 96 W., and the top in sec. 10, T. 5 S., R. 96 W. 

As the parts of the section were correlated by tracing 

some single bed which had a distinctive topographic 

expression, the error in correlation is probably small. 

A Brunton compass was used as a hand level to measure 

the section~ but a great many of the beds were measured 

with a 6-foot steel tape. This section contains the 

type sections of the Garden Gulch and Parachute 

Creek members. It also has particular significance 

-for the specific study whose results are recorded here, 

because it represents the locality of greatest accumulation of oil shale in the basin of the ancient Uinta 

Lake. Plate 8 shows another composite section of 

the Green River formation. The lower part of this 

section, with the exception of a sandstone bed at the 

top, which is about 73 feet thick, was measured along 

the road from Fruita to Rangely, Colo., from a point 

near the head of Trail Creek to the top of the divide 

between Trail Creek and West _Douglas Creek. The 

upper part of the section, including at the base the 

thick sandstone bed just mentioned, was measured on 

the north side of Cathedral Creek in sec. 26, T. 3 S., R. 

99 W., Rio Blanco County, Colo. The two parts of 

this section are widely separated, and their correlation· 

is therefore doubtful, but nevertheless the writer 

believes that the interval not represented at the top 

of the Douglas Creek member is rather small. 

Plate 8 also shows a composite section that illustrates the litholQgy typical of the Green River 

formation in the extreme eastern part of the Uinta 

Basin. The lower part of this section was measured 

in Hells Hole Canyon, in sec. 22, T. 10 S., R. 25 E. Salt 

Lake meridian, and the upper part in the canyon of 

the White River in sec. 27, T. 9 S., R. 25 E., both in 

Uintah County, Utah. As measured in the field the 

two parts of this ·section overlap, and by matching 

several distinctive groups of beds it was possible to 

correlate the two parts so that the composite section 

is a complete cross section of the folmation for that 

vicinity. At. the top this columnar section contains 

the type section of the Evacuation Creek member. 

Plate 8 also shows a columnar section of the Green 

River formation measured a few miles north of Deep 

Channel Creek in sees. 29 and 30, T. 4 N., R. 95 W., 

Moffat County, Colo. This section illustrates the 

lithology of the delta and shore facies that make up 

the Gray Hills of that vicinity. 

ROCQ WEST o• Jmmm CUU;.AH 

DUCHESN.E-UINTAH COUNTY LINE SECTION 

West of Bitter Creek the lithologic units of the Green 

River formation are different from those recognized in 

Colorado. and the extreme eastern part of Utah near 

Watson. Only the upper oil-shale group of the Parachute Creek member has been traced continuously 

across the region between Watson and that part of tbe 

Uinta Basin west of Bitter Creek. Two d·etailed sections were studied in this part of -the Uinta Basinon-e on the north side of Minnie Maud Creek, near the 

Duchesne-Uintah County line, and the other a composite section in Indian Canyon along the post road 

from Castlegate to Duchesne. These sections are so 

different from each other and so unlike the formation 

east of Bitter Creek that they can best be described 

separately. 

The section on Minnie Maud Creek is not complete. 

By comparison with the section 13 miles to the west, 

in Gate Canyon, the writer estimates that about 300 

feet at the. base is not exposed. But the remainder of 

the section on Minnie Maud Creek is excellently exposed and may be divided, for convenience of description, into two parts. The lower part or delta facies is 

about 440 feet thick and contains about 52 per cent of 

sandstone; the upper part is about 900 feet thick and 

consists principally of marlstone and shale., 

Deltafacies.-The delta facies makes the walls of the 

narrow inner canyon along Minnie Maud Creek. (See · 

pl. 9, B.) It also makes the walls of a great number of 

short side canyons such as Gate, Petes, and Water 

Canyons. Most of the sandstone beds of· this facies 

are medium grained, somewhat muddy, dark yellowish 

brown or olive-brown, and either crudely platy or 

massive. They contain an abundance of muscovite. 

and some biotite. Many are cross-bedded or ripple 

bedded and fill shallow channels in the beds below. 

In a few the bedding is highly distorted, and in two 

places the writer measured dips as steep as 35°. (See 

pl. 9, A.) The sandstone beds range in thickness froin 

about 1 foot to 55 feet. One thick bed that is greatly 

contorted contains several large lenticular blocks of oil 

shale and evenly bedded marlstone and also many 

small shreds-1 inch to several inches·· long-of very 

rich oil shale. (See pl. 10, A.) Some beds are very 

fine grained, muddy or limy, light gray to brown, and 

regularly bedded; others are coarse grained, light gray 

to white or very ferruginous, and variable in thickness. 

A few thin beds are saturated "\\ith bitumen. Mud 

curls, clay pellets, and waterworn mudstone fragments 

are plentiful in the sandstone beds in this part of the 

section. Current ripples are abundant, but oscillation 

ripples are rare. 

Much of the shale in this facies is light brown to ashgray and flaky, but there are also many distinctly and 

finely laminated or even papery beds that contain some 
16 ORIGIN AND MICROFOSSILS OF OIL SHALE OF GREEN RIVER FORMATION 

organic matter. In some of the marlstone beds organic 

matter is distributed uniformly; in others it is segregated in thin layers. There are also several beds of 

rather hard sandy and inicaceous greenish-brown mudstone that show little or no bedding. The weathered 

outcrop of these beds is spheroidal, because the n1aterial 

spalls off in much the same manner that some homogeneous igneous rocks weather. Some of the limiest 

marlstone beds contain mud curls and edgewise conglomerate. 

About 100 feet below the rin1 of the inner canyon 

that marks the top of the lower sandy part of the formation there are several rich oil-shale beds intercalated 

with thick beds of sandstone. Thes3 represent the 

upper oil-shale group of the Parachute Creek member. 

Where this section was measured it contains only three 

beds that have any probable economic interest. Each 

~s about 3 feet thick and will yield 15 to 25 gallons of 

~il.to the ton. These beds, however, are not regular. 

They have been distorted, broken, and pinched off by 

differential compaction that occurred soon .after they 

were deposited. (See pl. 10, A.) Inter]?edded with 

them are several conside-rably thinner beds, which the 

writer estimates to range in potential yield from about 

10 to nearly 40 gallons ef oil to the ton. Some are 

papery and scabrous, but most of them are hard and 

massive and show unusually good mosaic brecciation. 

Upper shaly facies.-The upper shaly facies of the 

formation is about 900 feet thick It is interrupted a 

little above the middle by a group of hard sandstone 

beds, here named the Horse Bench sandstone lentil, 

which makes a remarkably smooth and extensive 

bench .or table-land. (See pl. 9, B.) Below this bench 

the shale makes. a steep slope down to a narrower 

bench at the top of the inner canyon. Above the 

Horse Bench sandstone there is a similar shale slope 

~p to the base of the Bridger formation. 

Qrayish-brown shale and shaly marlstone, much of 

:which is sandy and either regularly laminated or rather 

crudely flaky, makes up the larger part of the sh.aly 

unit below the Horse Bench sandstone. There are also 

some hard platy marlstone beds, a larger amount of 

hard greenish-gray micaceous mudstone that weathers 

spheroidal, and a few zones of very soft buff shale. 

Above the Horse Bench sandstone hard drab, either 

uniformly colored or faintly banded mudstone which 

weathers spheroidal and contains much marcasite is 

most plentiful, but chocolate-brown soft flaky shale 

also occurs. 

In the lower part of the upper shaly facies beds of 

fairly rich oil shale 3 to 8 inches thick occur sparingly. 

Most of them are massive and show mosaic brecciation, but a few are papery and scabrous. Only a few 

thin beds of shale or marlstone above the Horse Bench 

sandstone contain organic matter, and they are very 

lean. About 250 feet below the top ·of the Horse 

Bench sandstone are three thin beds of low-grade 

papery. oil shale that contain abundant fly larvae. 

Sandstone makes up less than 9 per cent of the upper 

shaly facies of this section. The Horse Bench sandstone includes about half of it, and the rest occurs 

either as single thin regular beds or as small groups of 

beds. Most of it is fine grained, hard, thinly and 

·evenly bedded, and micaceous. Muscovite is more, 

plentiful than biotite, but in a few beds fresh black 

biotite is abundant. Perhaps these contain considerable volcanic ash. The colors of the sandstone range 

from light gray to nearly black in the more limy beds 

and from buff to dark reddish brown in the ferruginous 

beds. 

The Horse Bench sandstone is about 55· feet thick 

and consists of nearly equal groups of thin-bedded and 

ripple-marked sandstone beds that alternate with a. 

lesser amount of hard greenish-gray micaceous and 

sandy mudstone. About 15 feet of similar but thin 

and obscurely bedded mudstone separates the twosandstone groups. The whole unit is much more. 

resistant than the associated rocks and makes a very 

conspicuous topographic feature. (See pl. 9, R.) 

Because it forms the broad table-land between Minnie 

Maud Creek and Jack Canyon, known as Horse Bench,. 

the writer has named it the Horse Bench sandstone 

lentil. It is about 475 feet below the top of the formation and about 500 feet above the principal oil-shale 

beds. It makes a very convenient horizon marker 

and has been traced about 25 miles west and about 2() 

miles east from the Green River and probably could 

be traced many more miles in each direction. 

. Limestone is very rare in the upper shaly facies,." 

despite the abundance of lime in the beds of marlstone,.: 

shale, and sandstone. There are, however, two thin 

algae reefs at the top of the formation. 

Mud cracks are remarkably plentiful, having been 

found at 27 horizons in the upper 900 feet of the forma-:-

tion. Moreover, at most of these horizons more than 

one b~d is mud cracked, and at many there are several 

hundred thin beds, a quarter of an inch to 2 inches 

thick, that are mud cracked. Mud curls and rain 

prints accompany some of the ·mud-cracked beds. 

Current ripples are very numerous in the beds of 

sandstone and sandy shale, but oscillation ripples are 

more rare. Some unusually fine sharp-crested oscilla...: 

tion ripples with well-formed medial ridges were 

found at the top of the Horse Bench sandstone. 

Plant fragments were Jound at only two places. 

The complete absence from this section· of the molds 

of salt crystals, in comparison with their abundance at 

other localities, is worthy of note. 

·GATE CANYON SECTION 

In the yicinity of Gate and Argyle Canyons the 

writer examined the formation and estimated the thick-
STRATIGRAPHY 17 

ness of the larger units. A comparison _of the rocks at 

these places ~th -those just described is interesting. 

At the base, in the northeastern part of T. 12 S., R. 

13 E. ·Salt Lake meridian, there is a predominantly 

shaly unit which consists of thin-bedded gray and 

greenish-gray shale with a lesser amount of evenly 

bedded fine-grained limy sandstone. It also contains 

many beds of ostracode-bearing shale and limestone 

and a few beds of nearly black papery -low-grade oil 

shale which also contain ostracodes. 

A sandstone facies 500 to 600 feet thick overlies the 

basal part. It makes the deep, narrow canyon of 

Minnie Maud Cre-ek and is the westward extension of 

the delta facies near the Duchesne-Uin tah county 

line. However, in the vicinity of Gate Canyon it 

contains 75 to 80 per cent of sandstone. The sandstone is fine to medium grained, dark brown, and 

somewhat muddy. Many of the beds are mas!3ive 

and variable in thickness, but some are thin bedded 

and platy. 1\!any also are cross-bedded or ripple 

bedded; some contain bottom-set, foreset, and topset 

beds, and others fill shallow channels cut into the beds 

below. The cross-bedding in one muddy channel 

sandstone is inclined 21° from the normal bedding 

planes. Thin regular beds of hard greenish-gray mudstone are interbedded with the sandstone of this 

facies. A few red mudstone partings were also found. 

Westward, up Argyle Canyon, the sandstone facies 

changes; beds of hard, evenly bedded greenish-gray 

mudstone with thin red bands replace sandstone beds 

and compose about half of the unit. · 

About 1,000 feet of shale and marls tone similar to 

the upper shaly facies 13 miles to the east, near the 

Duchesne-Uintah county line, makes the remainder qf 

the formation at Gate Canyon. It also contains the 

Horse Bench sandstone, which is nearly identical with 

that farther east near the Green River. 

INDIAN CANYON SECTION 

The composite section along Indian Canyon Is 

complete. It is about 4,900 feet thick and is the 

thickest known section of the Green River formation. 

It contains two tongues at the base-one, which presumably disappears westward, is lacustrine, and its 

lithology is .cha:r;acteristic of the basal member of the 

Green River formation; the other, which _disappears 

eastward, overlies the lacustrine rocks and is identical 

in lithology with the Wasatch formation, to which it 

probably belongs. The rest of the Green River 

formation may be divided for conv~nience of descrip-. 

tion and interpretation into four distinct units-(1) 

the second lacustrine facies, which overlies the tongue 

of the Wasatch formation, (2) a thick delta facies, 

(3) an oil-shale facies, arid (4) at the top ·a thick 

barren and saline facies. . (See pl. 11.) 

Tongw, of Green River formation.-The basal part, 

a tongue of the Green River formation, is about 200 

feet thick and consists mostly of light chocolate-brown 

flaky or paper shale wi~h an abundance of cyprid 

ostracodes and hard gray platy marlstone that locally 

contains gastropod and thin pelecypod shells. Limestone, consisting mostly of ostracodes, and hard gray. 

mudstone, together with several thin beds of darkcolored shell marl that contain Goniobasis, Anodontalike shell fragments, and ostracodes, make. up about 

20 per cent of this unit. It also includes a sm-all 

amount of carbonaceous shale and two thin beds of 

coal. Sandstone is rare, and only a little of the shale 

and marlstone is sandy. Very few beds contain. 

enough organic matter to be considered low-grade 

oil shale. Oolitic beds are absent, and there is ·but 

one small and completely silicified algae reef.-

Tongue of Wasatch formation.-The tongue of the 

Wasatch formation is about 380 feet thick and consists 

of drab, buff, greenish, and red mudstone withrather 

numerous thick l~nticular beds of medium to coarse 

grained sandstone. Most of the sandstone beds are 

massive, but a few are cross-bedded. Their colors 

range from nearly white to dark reddish brown, but 

yellowish brown predominates. At the base and top 

of the tongue of Wasatch beds the changes in lithology 

are transitional. 

Second lacustrine facies.-The tongue of the Green 

River formation at the base represents the first lake 

stage; the lithologic unit above the tongue of the· 

Wasatch formation represents the second and is 

called the second lacustrine facies. It is not greatly 

different from the basal unit but lacks the beds of 

carbonaceous shale, coal, and shell marl. It is about 

7 50 feet thick and consists predominantly of shale, 

much of which is light gray or light grayish brown 

and flaky. A little is soft and papery. There is also 

some hard platy marlstone with delicate color banding. Only a few beds are sandy. Many of the beds1 

especially the chocolate-brown, papery, and flaky 

on~s, contain great numbers of ostracodes. These 

b.eds are very low grade oil shale. A little above the 

middle of the unit, in the lower part of a low but 

persistent cliff, is a massive oil-shale bed which the 

writer estimates will yield about 20 gallons of oil to 

the ton. · 

Most of the limestone of the second lacustrine facies 

is thin and rather poorly bedded, light brown to buff, 

and muddy. A few beds are sandy; others are soft 

and earthy and might. be regarded simP,ly as marl. 

Many contain abundant ostracodes, and some near the 

top of the facies contain numerous fi.shbone fragments. 

Mud cracks are also plentiful in those beds that contain the bone fragments. 

All the sandstone of this unit is very fine grained, 

limy, and micaceous. Most of it is thin and evenly 

bedded, but a little is cross-bedded or ripple bedded. 

Yellowish gray and dark reddish brown are the prevailing colors. 

j 

,....,'.

,, 

~ 
18 ORIGIN AND MICROFOSSILS OF OIL SHALE OF GREEN. RIVER FORMATION 

Delta .facies.-The delta facies is about 1,875 feet 1 

thick and makes up a little more than one-third of the 

formation in this part of the Uinta Basin. More than 

7 5 per cent of the facies consists of hard sandy and. 

micaceous grayish or brownish-green mudstone in 

fairly regular beds a few inches to 2 or 3 feet thick 

which are either homogeneous or vaguely laminated 

and which_ exfoliate so that the weathered face consists 

of many spheroidal ·surfaces. Locally thin regular 

bands of brick-red or maroon ·mudstone or flaky shale 

alternatP. with the greenish beds. 

Most of the sandstone of the delta facies is fine 

grained, muddy, micaceous, and light to dark gray, and 

forms rather regular beds from a few inches to about 

1 foot thick. Many beds are gently cross-bedded or 

ripple bedded, but some are massive. Thick irregular 

lenses of fine to medium grained buff or brown sandstone 

are plentiful in the lower 350 feet of the facies. They 

rest in channels cut into the beds below and grade 

laterally into hard sandy greenish mudstone. A few of 

them contain very unusual conglomeratic lenses whose 

subangular to well-rounded pebbles of shale and claystone are firmly bound in a matrix of calcite in which 

there is some sand. These lenses of conglomerate 

contain many fragments of the carapaces and bones of 

turtles, the teeth and bones of crocodiles and fish, 

large garpike scales, pieces of carbonized wood and 

leaves, and the impressions of pelecypod shells. 

Interbedded with the greenish m.udstone and finegrained sandstone are rather numerous thin massive 

beds of marlstone. These are dense and buff; light 

chocolate-brown, or pinkish gray. Some, however, 

are greenish gray, sandy and micaceous, and crudely 

bedded or platy; others are soft, earthy; and ocherous. 

Several layers contain mud curls or mud cracks. One 

bed contains many palm-leaf and stem impressions. · 

Papery shale, evenly laminated, or flaky shale makes 

· up only about 1 or 2 per cent of the delta facies, and 

most of that is in the lower few hundred feet. It is 

· gray or light chocolate-brown, rather soft, and limy. 

Some beds are sandy; others somewhat carbonaceous. 

Oil-shale jacies.-The oil-shale facies is about 380 feet 

thick and contains many thin beds of oil shale, most of 

which are papery or have thin. platy bedding. A few 

are massive, and nearly all show excellent mosaic . 

brecciation. They are brown to bls.ck and weather 

ash gray to purplish gray. One bed near the base of 

the -unit is ~f minable thickness, 4 feet 8 inches, and 

would yield, as estimated, 25 to 30 gallons of oil to the 

ton. The lower part of this bed is papery and tough 

but only moderately rich; the very rich upper part is 

tough and slightly contorted and weathers purplish 

gray. The rest of the oil-shale beds range in thickness 

from 4 inches to about 1 foot. Near the top of the unit 

a thin bed of rich oil shale is very clearly mud cracked. 

Another thin bed of rich oil' shale about 50 feet lower 

in the unit contains abundant fly larvae, the only ones 

found in the Indian Canyon section. 

The greater part of the oil-shale facies consists of 

barren or very lean gray or light-brown flaky ·shale. 

Some beds of marls tone are hard, sandy, and platy; 

others are soft and somewhat clayey. Thin beds_ of 

gray to brown very fine grained sandstone or siltstone_. 

are interbedded with the marlstone, shale, and oil shale. 

A few of them are cross-bedded or ripple bedded, and 

some show small .oscillation ripples. Mud cracks and 

mud curls were found in some beds of shale and sandy 

mudstone. The oil-shale facies contains only a few 

thin beds of limestone. These are hard, dense, and 

muddy or sandy. . 

Barren and saline facies.-The barren and saline 

facies is about 1, 700 feet thick and makes up the 

remainder of the Green River formation. Almost all 

of the upper half of this unit represents a distinctly 

saline stage of the lake. Calcite pseudomorphous 

after glauberite(?) and anhydrite(?) and empty molds 

of these crystals are extremely abundant in that part. 

Mud-cracked- bedding planes are remarkably numerous. 

More than 90 per cent of this facies consists of 

lean or barren shale and marlstone. Beds or groups 

of beds -of soft clayey finely flaky shale alternating 

with beds of harder sandy marlstone having thin 

platy- bedding predominate. The colors of t4ese 

rocks are light brownish or greenish gray, buff, brown, 

and brownish pink. Shades of gray and brown prevail. 

. Some beds are massive but show faint color ban~ing 

that indicates bedding laminae; others are papery~ 

Calcite fillings of glauberite(?) molds make up as 

much as half of some of the shale beds. Most of the 

crystals are less than one thirty -second of an inch 

long, but in a few beds there are salt crystal molds 

about five-eighths of an inch long. · The mud cracks 

of some beds are Jilled with sm~ll salt pseudomorphs. 

(See pl. 10, B.) A few beds contain innumerable 

radiating bundles of thin bladelike crystal molds. 

Beds of sandstone and limestone also contain crystal 

. molds. These salt-crystal molds and their significance are ·discussed more fully in another report.42 

Mud cracks were recorded at 38 different horizons 

in the barren and saline facies, and at n~arly all of 

these horizons many rather than a few bedding planes 

showed the cracks. 

. Oil-shale· beds in this facies are few and of poor 

quality. One near the top of the saline zone which 

the writer estimates would yield 15 to 20 gallons to 

the ton is 4 feet thick; another richer bed, but only 

1 foot 6 inches thick, is just below the saline zone. 

Other oil-shale beds are thinner and less rich. 

A few beds of muddy or sandy limestone are interbedded with the oil shale, marlstone, and sandstone. 

u Bradley, W. H., The occurrence and origin of analcite and meerschaum beds 

in the Green River formation: U. B. Geol.·Sunrey Prof. Paper 158, p. 5. 18. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 9 

A. STEEP FALSE BEDDING IN A FINE-GRAINED MUDDY SANDSTONE 

OF THE DELTA FACIES IN A SMALL CANYON TRIBUTARY TO MINNiE 

MAUD CREEK NEAR THE DUCHESNE-UINTAH COUNTY LINE, UTAH 

The steepness of the bedding is local and apparently due Lo differPnllal compaction. 

B. VIEW SOUTHWEST ACROSS THE VALLEY OF MINNIE MAUD CREEK NEAR THE BOUNDARY 

BETWEEN DUCHESNE AND UINTAH COUNTIES, UTAH 

The remarkably Oat bench is the top of the Horse Bench sandstone lentil. The inner canyon of Minnie Maud Creek is cut into the sandy deltaic facies of the Green River formation , and the principal oil-shale group is 

.iust below · the rim of the inner canyon. The road in the foreground furnishes n scale. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 10 

A. LARGE LENS OF OIL SHALE AND ORGANIC MARLSTONE I N THE MODDY SANDSTONE 

OF THE DELTA FACIES OF THE GREEN RIVER FORMATION NEAR THE DUCHESNEUINTAH COUNTY LINE 

Lens shown by white line. By differential compaction the top of this lens has been d epressed several feet below its original position, which is indicated at the right. 

B. MUD-CRACKED ORGANIC MARLSTONE BED FROM INDIAN CANYON, UTAH 

Small calcite pseudomorphs of a salt, probably glauherite, fill the cracks. No te the marked convexity of the polygon surfaces. 
<l.l 

0 

c 

0 

·..:; 

<1) 

E' 

L 

<2 

L 

<l> 

> 

e:r 

c 

<l) 

()) 

L 

t') 

'o 

I1J 

(f) 

(\) 

...r: 

n.. 

(i) 

c 

L 

it 

:J 

() 

co 

lJ 

c 

0 

<J 

QJ 

en 

c 

0 

~ 

<0 

E 

L 

..£' 

L 

~ n:: 

c 

<I) 

. ., 

L 

<.') 

'b 

· <l> 

" · '()j) 

c 

0 

.... 

<V 

1/) 

Ill 

. OJ 

U . S. GEOLOGICAL SUR VET 

B 

A 

Wasqtch formation 

cro ... bedded sandstone lens; woody plant fragments. 

Light-brown flaky shale. 

Mudstone and marlstone, 

Drab sandy mudstone and muddy sandstone; plants and croco. dile and turtle bones. 

Conglomeratic lens with turtle, crocodile, and fish hones and 

many plant fragments. 

Alternating thin beds of greenish mudstone and sandstone. 

Thin beds or sandstone, shale, and marlstone, containing near the top many plant remains. 

Alternating thin layers of maroon and ~eenish mudstone. 

Sandstone and mudstone. 

Maroon and greenish mudstone. 

Alternating beds or sandy greenish-gray mudstone and :floegrained muddy sandstone. 

Oil shale, 15-20 gallons. 

Papery shale, with numerous ostracodes and beds or marlstone 

and limestone. 

Fine--grained sandstone, sandy shale, and marlstone. 

011 shale, 1Q-15 gallons. 

Gray to yellowish·hrown marlstone with thin beds of papery shale and sandy shale. 

Oil shale, 8-10 gallons. 

Alternating thin beds of papery shale and limestone, 

Bull papery shale with abundant ostracodes. 

Gray and bull sandy mudstone, locally banded with red. and 

containing thick lenses of soft brown and gray medmm· 

grained muddy sandstone. 

Papery ostracode shale and shaly mudstone with many thin 

beds of she11 bearing madstone. 

Lignite, 

Soft papery ostracode shale with many thin beds of shell marl 

and two layers of lignite. 

Soft brown !laky shale and mudstone; ostracodes. 

Hard blocky marlstone. 

Papery shale and muddy sandstone; ostracodes. 

Ill 

Q) 

<l 

~ 

al 

..., 

Q) 

0 

c 

B 

Pale groonlsh·gray mudstone; 

Soft muddy sandstone, 

Pale greenish-gray mudstone, 

Marlstone; ostracodes and :flsh scales. 

Regularly bedded pale green!sh·gray mudstone, locany;shaly. 

Sandstone and sandy mudstone. 

Limestone with bone fragments. 

Regular beds ol pale greenish·grey mudstone. 

Mud lump•, land. pebbl ... and bonee of turUot ao.cl car J)flre; plant fr.amezat& 

Greenish-gray mudstone. 

Marlstone with !ish bones. 

Regular beds of pale greenish-gray mudstone. 

Limestone with algal nodules 

Regular beds of drab sandy mudstone and micaceous muddy sandstone . 

Alternating regular beds of muddy sandstone and red and 

greenish mudstone. 

MarJy gray mudstone, 

Alternating red and greenish-gray mudstone. 

Rippl .. bedded muddy sandstone. 

Greenish-gray mudstone, 

.o\lternatiug red and greenish-gray mudstone. 

Alternating regular beds of drab sandy mudstone:and micaceous 

muddy sandstone, 

Marly mudstone', 

Alternating regular beds of drab sandy mudstone and micaceou. 

muddy sandstone. 

Light-brown mar !stone. 

Alternating regular beds of drab sandy mudstone and micaceous 

muddy sandstone, with a few thin beds of mudd y limestone. 

Several mudstone beds are carbonaceous and contain turtle 

bones. 

Carbonaceous shale and marlstone; turtle bones. 

Alternating beds ol drab sandy mudstone and micaceous muddy sandstone, with a few thin beds of muddy limestone. 

til 

.. ~ 

0 

~ Cl) 

iii 

.r:. 

(/) 

_J, 

0 

Vertical scele 

~Mud cr'eeke 

D 

c 

Algae reel. 

Sort shaly morlstone. 

Algae reef. 

Sort shaly marlstone. 

Oil shale with salt molds, 

Plant !ragments. 

Soft marly shale, 

Tu1!aceous sandstone. 

Rather soft sandy grey shale and thin shaly sandstone beds, 

Light-brown !laky shale. 

Sandy shale and sandstone 

Soft limy brown shale. 

Flaky and marly shale with several thin beds of rich oil shale. 

Oil shale, 30 gallons. 

Shaly sandstone. 

Oil shale, 20-2~ gallons. 

Flaky brown shale. 

on shale, 20-25 gallons; tly larvae, 

Soft sandy and marly shale. 

Tuffaceous sandstone. 

Marly shale. 

Turtle bones. 

Flaky grey shale. 

Oil shale, 1Q-15 gallons. 

Flaky brown shale. 

Oil shale, 1Q-15 gallons. 

Sandy and shaly mudstone. 

Andesitic crystal tuff. 

Light greenish-grey sbaly mudstone. 

Breccia. 

Oil shale, 3o-35 gallons. 

Platy madstone. 

Papery oil shele, 20-25 gallons. 

Marlstone and thln beds of low-grade oil shale. 

Flaky greenisb·brown shale • 

Shaly marlstone • 

Low~e oil shale, papary, Sort shale. 

(/) 

<11 

'() 

<E 

QJ 

c 

10 

([) 

lJ 

c 

rn 

c 

<11 

!... 

L 

<!) 

ro 

COMPOSITE COLUMNAR SECTION OF THE GREEN RIVER FORMATION MEASURED IN INDIAN CANYON; DUCHESNE COUNTY, UTAH 

The beae is in """· '1:7, T. 11 S., R. 8 W. Untah opecial meridian. and the top is about 26 mil .. to the """"-t;. 

D 

PROFESSIONAL PAPER 168 PLATE U 

Yellowish· brown flaky shale, 

Organic madstone; gar-pike remains. 

Brown to grey sandy shale and cherty marlstone; gar.pik remains. 

Pinkish-gray sandy and marly shale; numerous gar·pike remains 

and a few plant fragments. 

Pinkish-grey shale and marlstone with a lew salt molds; gar. pike scales. 

Organic marlstone with a few salt molds near the top. 

Sbaly brown and gray marlstone with a small quantity of salt 

molds. 

Marly shale without salt molds. 

Marlstone with salt molds. 

Marly shale without salt molds. 

Oil shale, 15-20 gallons. 

Marlstone with salt molds. 

Analcite beds 

Shaly marlstone with abundant salt molds. 

Sepiolite beds, 

Marly gray and brownish-gray shale with an abundance of salt 

molds. 

Marlstone without salt molds; plant fragments. 

Marlstone with salt molds. 

Shale with bladed salt molds. 

Marly shale without salt molds. 

Merly shale with salt mold"' 

Sort brown shale without salt molds. 

Sbaly marlstone with salt molds. 

Oil shale, 15 gallom. 

Marly shale; thick units with an abundance :or salt :nolds alternating with thin units without salt. 

Coarse-grained tuffaceous sandston .. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 12 

A . CONTACT BETWEEN THE BRIDGER AND GREEN RIVER FORMATIONS IN THE VALLEY 01< EVACUATION 

CREEK , SEC. 12, T. 10 S., R. 24 E. SALT LAKE MERIDIAN, UINTAH COUNTY, UTAH 

This viP.w shows plainly the differential compacLion be tween the shaly marls tone of the Green Rivel' formation (below while line) a nti the channel sandstonP. lensP.s at the base of t he Bridger formation (above white line). 

B . LOWER SANDY PART OF THE BRIDGER FORMATION BESTING I N EVIDENT CONFOHMITY ON THE 

GHEEN RIVER FORMATION, APPROXIMATELY I N SEC. 2 1, T. 11 S., R. 17 E., DUCHESNE COUNTY, UTAH 

The arrows at the margins mark the boundary. 
STRA'riGRAPHY 19 

Most of them are thin bedded, dense, and buff or 

light chocolate-brown. Some beds contain an abundance of biotite. 

Sandstone is even less abundant than limestone and 

makes up less than 3 per cent of this facies. Most of 

the beds are fine grained, muddy, micaceous, and 

platy. A very few are cQarse grained and massive. 

Many 'of them are mud cracked, and some contain 

mud curls or plant fragments. 

·A thin bed near the base of the oil-shale zone, 

about 2,900 feet above the base of the formation, is 

saturated with bitumen but proved upon microscopic 

examination to be an andesitic tuff. It consists largely 

of fresh crystals of augite, andesine feldspar (An40Ab60), 

and biotite, together with small irregular fragments of 

brownish glass whose index of refraction is about 1.49. 

Some of these fragments of acidic glass contain aggregates of pyroxene and ·plagioclase feldspar, evidently 

fragments of a glassy lava. In addition to these major 

constituents, there are a few minute crystals of zircon 

and apatite. The secondary minerals are opal, which 

forms the groundmass of the rock, and calcite, which 

is coarsely crystalline and rare. · 

About 550 feet above the oil-shale facies is a group 

of sandstone beds about 16 feet thick which makes a 

conspicuous and very persistent bench. These beds 

are gray or brown, fine grained, and micaceous. Many 

are current-ripple bedded; some are massive and others 

platy. This persistent sandstone unit may be. the 

westward extension of the Horse Bench sandstone, 

which it resembles. It is also at approximately the 

same stratigraphic horizon, 500 to 550 feet above the 

principal oil-shale beds. 

There are only two thin algae reefs in the barren 

and saline facies. These are just · below the saline 

zone. 

Columnar section.-Plate 11 shows a columnar 

section of the Green River formation measured in 

Indian Canyon. It is a composite section whose 

base is in sec. 27, T. 11 S .. , R. 8 W. Uinta special 

meridian and the top is approximately in sec. 21, T. 

4 S., R. 5 W. A Brunton compass was used to measure the section. The beds were correlated by tracing out distinctive beds or groups of beds from one 

locality to another. Although none of the groups. of 

beds of this composite section are widely separated, 

the base and top are about 26 miles apart. The 

section is therefore not a true cross section of the 

formation at any one place, and some of the changes 

of lithology ·upward from the base may be due to the_ 

fact that the parts of the section represent different 

parts of the basin. 

CORRELATION OF FACIES AND ZONES IN UINTA AND 

PICEANCE CREEK BASINS 

The correlation of the various facies and zones of the 

Green River formation in the Uinta Basin · west of 

Bitter Creek is shown diagrammatically in Plate 3. 

The basal facies, which in the vicinity of Indian Canyon 

is a lacustrine tongue, has been traced from Soldier 

Summit to the eastern part ofT. 12 S., R. 13 E., where 

it crosses Ninemile Creek. Although it has ne"Yer been 

traced from that point across the south margin of the 

basin, it is probably, from its similarity in lithology and 

stratigraphic position, exactly correlative With the basal 

unit along the White River near Watson. The second 

lacustrine facies, which includes a few beds of oil shale, 

has been traced from Narrows, in T. 9 S., R. 5 E., 

where it crosses the main line of the .Denver &~Bio 

Grande Western Railroad, toT. 12 S., R. 13 E. Between Willow Creek and T. 12 S., R. 13 E., the tongue 

of theW asatch formation dies out and the second lacustrine facies becomes a part of the basal U)lit of the Gate 

Canyon sec.tion. Although notably different, the delta 

facies of the Indian Canyon section is equivalent ·to 

that at Gate Canyon and that in the vicinity of the 

Duchesne-Uintah county line. Probably the delta 

facies near the Duchesne-Uintah county line is represented in the section along the White River north of 

Watson by the Garden Gulch member and the lower 

oil-shale group and overlying transitional beds of the 

Parachute Creek member; Winchester 43 mapped the 

group of richest oil-shale beds and demonstrated that 

it is continuous from the head of the Strawberry River~ 

in T. 8 S., R. 6 E., eastward along the south rim of 

the Uinta Basin to the Colorado line. (See pl. 1.) 

The group of richest oil-shale beds of Colorado is altnost 

surely an eastward extension of that in Utah. 

BRIDGER I'ORIIATIOII 

In the Piceance Creek Basin, Colorado, no formation younger than the Green River formation has been 

certainly identified, although the writer believes that 

the uppermost 400 feet of sandy beds in the center 

of the basin are lithologically and stratigraphically 

equivalent to. the Bridger formation, and he has tentatively assigned them to that formation. No fossils 

have yet been found in these beds. . Both the Bridger 

and Uinta formations have been defined by vertebrate 

fossils in Utah. 

LOWER BEDS 

In the eastern part of the Uinta Basin a thick series 

of brown massive or cross-bedded medium to coarse 

grained sandstone beds overlies the Green River for-· 

mation. It forms a rough and rather steep southwardfacing slope interrupted by many benches of harder 

sandstone. (See pl. 12, B.) This unit is about 800 

feet thick, contains a small amount of hard greenishgray sandy mudstone interbedded with the sandstone, 

and in niost places rests with evident conformity on the 

Green River formation. In an area extending over 

n Winchester, D. E., Oil shale of the Rooky Mountain region: U.S. Geol. Survey 

Bull. 729, p. 100, pl. 16, 1923. 
20 ORIGIN AND MICROFOSSILS OF OIL SHALE OF GREEN RIVER FORMATION 

many square miles in the vicinity of Evacuation Creek 

and the White River north of Watson, Utah, however, 

the contact between the two formations is decidedly 

irregular, having locally a relief of as much as 50 feet. 

(See pl. 12, A.) This irregular contact does not appear 

to indicate an erosional unconformity but seems rather 

to have been due to differential compaction of the 

shaly marlstone beds at thfl top of the Green E,iver 

formation and the sandy mudstone beds and streamchannel sandstone lenses at the base of the Bridger 

formation .... The regular thin beds of marlstone at the 

top of the Green River formation have been flexed so 

as to conform to the lower surfaces of the thick sandstone lenses, and though they have been distinctly 

squeezed and thinned below the lowermost salients of 

A 

Bridger beds were uniformly distnbuted, the contact 

is regular. (See pl. 12, B.) But in those areas where 

the lowest beds of the Bridger formation contain large 

stringers and lentils·of medium to coarse grained sandstone the contact with the underlying Green River 

formation is irregular. Apparently in these areas the 

first deposits in the Bridger epoch consisted of sandy 

mud, and these beds were trenched rather deeply by 

streams, which later filled their own channels with 

relatively clean medium to coarse grained and crossbedded sand. Locally these streams cut down close 

to the top of the Green River formation. After the 

stream channels were filled with sand a thick group of 

rather regular beds of muddy sand were laid down, and 

above them the remainder of the Bridger formation 

s:: CD .c: 

0. , ~ a: 

00. (/) 11) Q) , ::J 

Q. cr 

, 

3 

Ol 

3~ 

.... 

a· t::::l :,:, 

~ 

d'~ 3!: ,It)_ 

5.~. 3::3 

~::0 a·<· 

::JCI> , 

ti' .,co 

3~. 

o, ~ 

:J 

0 100 300FEET ~~~~~------~------~ 

FIGURE 2.-Probable original relation (A) between the beds of limy mud at the top of the Green River formation and the thick chan-

' nel-sandstone lenses near the base of the Bridger formation near the mouth of Evacuation Creek, in sec. 12, T. 10 S., R. 24 E. 

Salt Lake meridian, Uintah County, Utah, and the present relation between them (B) after having been compacted under the 

weight of nearly 2,000 feet of muddy sandstone and mudstone of the ~ridger and lJinta forn:aticns 

the sandstone lenses few of them have been truncated. 

Moreover, the beds of marlstone were deformed less 

and less downward, and a short distance below the 

sandstone lenses they were not at all disturbed. (See 

pl. 12, A.) In the same way but to a less marked degree 

the beds of muddy sandstone overlying the sandstone 

lenses have been deformed, being compacted more over 

the highest parts of the lenses and less over the intervals 

between them. Likewise the sandy shale surrounding 

the sandstone lenses was much compacted abov~ and 

below the sandstone lenses and less so between them. 

The irregularity of the contact between the Green 

River and Bridger formations in certain localities, then, 

appears to be correlat~d with an irregular distribution 

of sandstone near the base of the Bridger formation. 

Where the sand and mud making up the lowermost 

and the Uinta formation. These overlying beds 

aggregate nearly 2,000 feet in thickness. Under this 

load the sediments at the top of the Green River formation and at the base of the Bridger formation were compacted. (See fig. 2.) Because the uppermost beds of 

the Green River formation and the sandy mud between 

the channel fillings were very fine grained they were 

distorted most by the relatively incompactible sand 

lentils. The beds of muddy sandstone· that lie above 

the sand lentils were much less compactible than the 

fine-grained beds and accordingly were much less 

deformed. · 

For clarity the diagram shown in Figure 2 is considerably sin;lpli:fied. Actually in most places the 

sandstone lentils occur at various levels above the 

contact, overlap one' another, and interfinger with the 
\ 

STRATIGRAPHY 

sandy shale, so that not only have the· beds of marlstone and sandy shale been complexly contorted, but 

the thin fingers and marginal extensions of the sandstone lentils were co:dSiderably deformed and the crossbedding of the sandstone was twisted and tilted locally 

15° to 20° from its original attitude. Because of this · 

distortion of the cross-bedding it has been impossible 

to make out any regional trend in the dips of the cross 

beds and so determine the probable direction in which 

these early Bridger streams flowed-a determination 

that Rubey and Bass 44 were able to make with certain 

stream-channel deposits of the Dakota sandstone in 

Kansas. 

Winchester 45 found fossil insects similar to those of 

the Green River formation in a thin mudstone bed of 

this large sandy unit and therefore included it in the 

Green River formation. Osborn 46 and Peterson, however, regard this series of sandstone beds as a part of 

the Bridger formation, having found bones of Bridger 

mammals ·in it. The lower part of this sandstone -

unit, about 500 feet in thickness, contains few fossils, 

but according to Peterson 47 the type specimens of. 

Metarhinus and Sphenocoelus were found near the base. 

The upper part is more fossiliferous and according to 

Riggs 48 contains Metarhinus, Dolichorhinus, Telmatherium, Mesatirhinus superior, Rhadinorhinus, Eobasileus, Triplopus, Mesonyx, and Harpagolestes, all of 

which are Bridger fossils. A few crocodiles, many 

turtles, and beds of fresh-water clams were also found. 

Reeds, leaves, and branches of trees were associated 

with the vertebrate fossils. 

Because this sandstone series contains vertebrate 

fossils of Bridger age and because the very distinct 

lithologic change from regularly laminated marlst0ne 

and shale to medium-grained massive or cross-bedded· 

sandstone indicates an abrupt change from lacustrine 

to fluviatile conditions, the ,writer prefers to regard it 

as a part of the Bridger formation, in spite of the fossil 

insects which it contains. Moreover, the insects are 

so like those now living that it seems dubious if they 

_could be used to date so small a stratigraphic interval 

and to controvert the evidence of so large a vertebrate 

fauna. 

It is somewhat puzzling that the vertebrate fossils 

found near the base of the sandstone series indicate 

middle or late Bridger time. This suggests that, as 

there appears to have been no significant break in sedimentation between the· Green River and Bridger formations, the uppermost portion of the Green River 

formation is perhaps of Bridger age. In other words, 

u Rubey, W. W., and Bass, N. W.-, TbegeologyofRussell County, Kans.: Kansas 

Geol. Survey Bull. 10, pp. 54-62, 1925. 

u Oral communication, September, 1925. 

46 Osborn, H. F.1 Fossil mammals of the Uinta beds: Am. Mus. Nat. History 

Bull., vol. 7, p. 73, 1895. · 47 Peterson, 0. A., quoted by Riggs, E. S., New or little-known titanotheres from 

the lower Uinta formations: Field Mus. Nat. History Pub. 159, G~ol. ser., vol. 4, 

p. 23, 1912. 

" Idem, p. 24. 

if the boundary between the Green River and Bridger 

formations were to be determined wholly by the ver~- _ 

brate fossils it apparently should be placed at some 

indefinite horizon below the present lithologic boundary. According to this definition of the boundary, 

lakes seem to have persisted longer in the Uinta Basin 

than in the Green River Basin of Wyoming, where all 

· of the Bridger epoch is represented by fluviatile 

deposits. 

The writer has traced the contact between "the 

Bridger and Green River formations a'ong the 

north side of the White River from a place near the 

Colorado line southwestward to the mouth of Evacuation Creek, where the contact crosses the river, and 

westward across Uinta Basin to the Green River. It 

crosses the Green River near the northeast corner of 

T. 11 S., R. 18 E. Salt Lake meridian. Thence westward to the head of Gate Canyon it is· nearly parallel 

to the road from the head of Gate Canyon to Hill 

Creek. West of Gate Canyon it has not been traced, 

and in Indian Canyon the contact between the two 

formations is transitional and uncertam. 

The lower part of the Bridger formation is variable. 

along the strike, and in places the lithologic changes are 

rather abrupt. In sec. 22, T. 11 S., R. 17 E. Salt Lake 

meridian, it consists almost wholly of fine-grained brown 

micaceous sandstone in fairly regular beds, most of 

which are massive but some of which are cross-bedded 

or ripple bedded. The ripple bedding consists of only 

the steeper foreset beds, which dip g~nerally northwest. Near the base are a few thin zones of hard gray . 

sandy mudstone that -have thin and regular bedding. 

One such zone contains a thin bed of carbonaceous 

shale. Near . the top are several more beds of hard. 

greenish-gray sandy m-qdstone. At this place the unit 

makes a steep cliff, which was measured by triangulation and found to be 454 feet high at one ·point and 

495 feet at another. (See pl. 12, B.) 

A few miles west, about in sec. 10, T. 11 S., R. 16 E., 

the Bridger formation contains only a little sandstone 

and makes a rather gentle slope that is faintly color 

banded. It consists mostly· of buff and light-gray 

sandy mudstone. At the head of Gate Canyon the 

lower third of the unit consists of brown irregular 

·sandstone with a smaller amount of gray sandy m~dstone, and the rest consists of mudstone with a subordinate amount of sandstone. 

In· Indian Canyon the writer measured a detailed 

section of the lower part of the Bridger· formation. It 

is about 550. f~et thick. A little less than half of it is 

sandstone, most of which is medium grained, muddy, 

dark brown, and crudely platy. The beds are ripple 

bedded and discontinuous and alternate with sandy 

mudstone and shale. Locally this part contains thick 

massive lenses of yellowish-brown sandstone. The 

rest of the section .consists of coarsely flaky sandy and 

limy shale and several beds of hard marlstone. Some 
22 ORIGIN ,AND MICROFOSSILS OF OIL SHALE OF GREEN RIVER FORMATION 

of the shale is lavender, and some is distinctly reddish. 

Many beds contain small mud flakes and curls; a few 

are carbonaceous and mottled red and pale green. 

UPPER BEDS 

The upper part of the Bridger formation, zone B of 

Osborn 49 and Peterson and the "Amynodon beds" of 

Riggs,50 consists of greenish, drab, red, maroon, ashgray, and buff sandy mudstone with lenticular medium 

to· coarse grained massive or cross-bedded muddy 

sandstone beds, many of which are ferruginous and 

dark brown. Some are greenish brown and somewhat shaly. The writer observed this part of the 

formation at several places in the Uinta Basin, but 

did not study it. · 

The Uinta formation overlies the . Bridger with 

apparent conformity. 

RELATIONS OF THE TERTIARY FORMATIONS IN THE UINTA 

BASIN 

The major relations of the Bridger and Uinta formations to the other Tertiary formations are not wholly 

·clear. At the southern outcrop of the Bridger and. 

Uinta there is no angular discordance between them 

or between the Bridger and Green River, and yet on 

·the north side of the basin in the vicinity of Vernal 

the Uinta formation rests with marked angular unconformity upon the Mesaverde formation. Either 

of two explanations accords with these observations. 

One explanation is based on the hypothesis that 

the Cretaceous rocks (the Mesaverde formation} were 

already flexed so as to form a basin whose north rim 

turned up rather steeply along the flanks of the Uinta 

Mountains. In that basin the Tertiary, Wasatch, 

Green River, Bridger, and Uinta forma.tions were all 

deposited in strict conformity with one another. 

Accordingly each successive Tertiary formation would 

overlap more and more upon the edges of the rather 

steeply inclined Mesaverde formation along the north 

rim of the Uinta Basin. Around the other parts of 

the basin rim the initial inclination of the Cretaceous 

rocks was presumably so gentle that there is now no 

discernible discordance ·between them and the overlying Wasatch formation. 

The other explanation also postulates a similar 

original basin of Cretaceous rocks but one whose 

northern rim was less steeply upturned. This hypothesis differs chiefly frDm the first, however, in assuming 

an angular unconformity either betwe~n the Green 

River and Bridger formations or between the Bridger 

and Uinta formations. The writer has found no 

evidence that leads him to regard as probable an 

unconformity between the Wasatch and Green River 

4t Osborn, H. F., Fossil mammals of the Uinta beds: .A.m. Mus. Nat. History 

Bull., vol. 7, p. 74, 1895. 

so Riggs, E. S., New or little known titanotheres from the lower Vinta formations: 

Field Mus. Nat. History Pub. 159, Geol. ser., vol. 4, p. 22, 1912'. 

formations, although Eldridge 51 bas explained this 

same overl~p of the Uinta formation ~n the Cretaceous 

rocks along the north margin of the Uinta Basin by 

that assumption. The very ablllpt change in lithology between the Green River and Bridger formations 

makes a. diastrophic break there much more probable 

·than one between the Bridger and Uinta formations, 

whose rocks are so nearly identical that the boundary 

between them· can be determined only by the vertebrate fossils. According to this second hypothesis 

the Wasatch and Green River formations might rest 

with only a slight angular discordance upon the 

Cretaceous rocks, but the Bridger formation would 

truncate the Green River and Wasatch formations 

and overlap the Mesaverde. The Uinta would then 

overlap the Mesaverde still more, producing the 

relations observed in the vicinity of Vernal, Utah. 

Further speculation is unwarranted without more 

field study in the area extending {rom the place where 

the White River enters the Green River. formation 

west of Rangley, Colo., along Raven Ridge to the 

asphalt quarry about 3 miles southwest of Vernal, 

Utah. 

THE OIL SHALE 

DEFINITION 

The term-" oil shale" is defined on page 7, where 

it is also pointed out that most of the oil shale of the 

Green River formation could not be regarded strictly 

as shale, but instead that it is really a more or less 

magnesian madstone rich in organic matter. 

APPEARANCE IN HAND SPECIMENS 

The organic matter in oil shales imparts to them 

a· distinctive aspect, which, however, vari~s greatly 

in different shales, depending chiefly upon the amount 

of organic matter and its distribution in the rock. To 

some extent also the appearance of these organic rocks, 

particularly the lower grades of oil shale, is determined 

by their predominant inorganic constituents. Rocks 

consisting largely of clastic mineral grains of clay size 

with which is admixed only a small quantity of organic 

matter resemble ordinary barren shale or mudstone 

except for a faint brownish tone on the fresh fractures. 

Such beds are particularly common in the shore phases 

of the formation and range in potential oil yield from 

2 or 3 to as much as 10 or 12 gallons to the ton. Beds 

of ostracode-bearing limestone and ostracode-bearing 

shale, also in shore phases of the formation, are colored 

buff, yellowish brown, or even dark chocolate-brown 

with the ·organic matter that is uniformly diffused 

through the;m. They will yie,ld oil in quantities ranging from 5 or 6 to perhaps 20 gallons to the ton. Dense 

marlstone, which ranges in color from light brownish· 

gray or buff to chocolate-brown on fresh surfaces, is 

5t Eldridge, ·a. H., The asphalt and bituminous rock deposit$ of the United 

States: U. 8. Geol. Survey Twenty-second .Ann. Rept., pt. 1, p. 338, ftg. 29, 1901. 
OCCURRENCE 

very common, especially in the central parts of the 

basins. In rock of this type the organic matter may 

be uniformlv diffused, imparting a light-brown or 

dark grayish-brown color, or it may be segregated in 

fine dark-brown laminae. As these three distinct types 

of low-grade oil shale weather buff, yellowish brown, or 

greenish gray, they can only with difficulty be distinguished from beds wholly barren of organic matter. 

All transitions· exist between these low-grade types, 

which themselves are intergradational, and the highgrade oil shale, which in general has a more uniform 

aspect both on fresh and weathered surfaces. Highgrade oil shale, which may be regarded as that capable 

of yielding more than about 10 gallons of oil to the 

ton, ranges in color from grayish brown, which may 

have a faint yellowish or reddish cast, to jet black. 

In most beds· brown laminae are intermingled with 

darker-brown or black laminae which have a satiny . 

luster. However, some beds are apparently homogeneous. These are either of a dull, lusterless black or 

jetlike with a high luster. Both of these varieties are 

very rich in organic matter and represent the highestgrade oil shale of the Green River formation. They 

grind down to a light grayish-brown, somewhat waxy 

powder. They resemble rather closely the purer varieties of algal bogheads, such as the kerosene shale of 

New South Wales or the Bathgate boghead of Scotland. 

Weathered surlaces of rich oil-shale beds are distinctive and easily distinguished from other beds. 

Most of them weather light. bluish gray, a color which 

is apparently due to a very thin residual layer of the 

mineral constituents of the rock from which the organic 

matter has been oxidized. The dark organic m&tter 

showing through this thin film lends it the bluish tint. 

If the weathered filni is thick it appears stark white. 

All transitions exist between this white weathered 

surface through shades of grayish blue and grayish 

lavender to black surfaces which have only a fine 

dusting of white or yellowish -brown. Some of the 

· richest beds weather to look like antique unfinished 

mahogany. Polished surfaces of shale of that kind, 

even when examined critically with a hand lens, simulate old mahogany in a remarkable manner. From 

this resemblance the group of richest oil-shale· beds in 

the Green River formation known as the "mahogany 

ledge" takes its name. 

There are a few aberrant types of rich oil shale which 

might easily be ignored in the field on the assumption 

. that they were nearly barren shale. The most unusual 

of these looks like a felted mass of coarse brown-paper 

pulp. It weathers silvery gray and has a distinctly 

talcose appearance. Almost the only mineral constituent of this rock is a fibrous variety of sepiolite. Somewhat similar but more papery beds look equally poor. 

They are finely speckled with white. Still others 

consist of alternating coarse laminae of brown shale 

and vitreous black scabrous organic material. 

OCOUDENCE 

The oil shale of the Green River formation is most 

abundant in the vicinity of ·Parachute and R~an 

Creeks, Colo., and gradually decreases in amount in 

all directions from that area toward the original margins of the ancient lake basin. . . · 

For the lake which occupied the Uinta and Piceance 

Creek Basins during the Green River epoch and in / 

which the sediments were deposited that now make 

up the Green River formation of Utah and Colorado 

the writer has proposed the name "Uinta Lake." 52 

For the ancient contemporary lake that occupied the 

Green River Basin north of the Uinta Mountains the 

writer has used the name "Gosiute Lake," 53 which 

King 54 sugg~sted long ago. Northward beyond the 

White River the beds of oil shale rapidly thin and 

be~ome poorer in quality until in the area north of 

Deep Channel Creek none of the beds contain more 

than a minute quantity of organic matter. This relation between oil shale and shore phases of the Green 

River formation is typical and, as the writer has 

shown, 55 is well illustrated in several parts of the 

Green River Basin of Wyoming. 

The oil-shale units extend more than 140 miles 

westward from the vicinity of Parachute and Roan 

Creeks but thin gradually in that direction and be-

. come progressively less rich as they approach the 

western margin of the ·lake basin~ In the Uinta 

Basin the changes in the oil shale from south to north 

can not be observed, for the beds do not crop out 

along the north margin of the basin but are buried 

beneath an overlap of younger rocks. . 

The vertical distribution of the oil shale in. the 

Green River formation of Colorado and Utah is 

indicated in a broad way in Plate 3. It is shown in 

much more detail for several localities in the columnar 

sections of Plates 7, 8, and 11. In these columnar 

sections the estimated yields of many of the beds are 

given, but it should be noted that these estimates are 

subject to rather large errors, and therefore the columnar sections are chiefly of lJ.Se in sho~g the number 

and distribution of the richest beds. Many beds 

indicated in the sections as organic marlstone or 

simply marlstone will yield oil upon distillation in 

amounts ranging from 2 or 3 gallons to as much as 

10 or 12 gallons a ton. In general the richest of these 

beds of low-grade oil shale or organic marlstone are 

associated with. beds of rich oil shale. 

A more accurate picture of the relative richness of 

the beds in the principal oil-shale zories is given in 

= Bradley, w. H., The varves and climate of the Green River epoch: U. S. Geol. 

Survey Prof. Paper 158, p. 88, 1929. 

13 Idem, p. 88. 

u King, Clarence, U. S. Geol. Expl. 40th Par. Rept., vol. 1, p. 446, 1878. 

u Sears, J.D., and Bradley, W. H., Relations of the Wasatch and Green River 

formations in northwestern Colorado and southern Wyoming: U. S. Geol. Survey 

Prof. Paper 132, p. 101, 1924. ]Jradley, W. H., Shore phases of the Green River 

formation in northern Sweetwater County, Wyo.: U.S. Geol. Survey Prof. Paper 

140, p. 127, 1926. 
24 ORIGIN AND MICROFOSSILS OF OIL SHALE OF GREEN RIVER FORMATION 

Plate 13, which shows the results. of several long 

series of retort tests. These series of retort tests 

designated A, B, and C in Plate 13, can be correlated 

with the columnar sections shown in Plates 7 and 8 

by means of the mahogany marker, which was used 

as a datum for the retort tests and whose position is 

indicated in the columnar sections of Plates 7 and 8. 

Of these series of retort tests the series designated A 

in Plate 13 was the longest and the one that show~d 

the greatest differentiation of the beds. This series 

of tests was submitted to the Department of the 

Interior at a hearing on oil shale held before the Secretary December 1,· 1926. · 

Additional information as to the correlation of the 

groups of beds sampled was given to the Geological 

Survey by Mr. Flavius Wood/6 who was the engineer 

in charge of the sampling and testing of the group of 

beds in this section extending from the base to a level 

328 feet above the mahogany· marker. The samples 

were collected on Clear Creek in sec. 9, T. 5 S., R. 98 

W., Garfield County, Colo., and the retort tests were 

made in standard test retorts according to the Bureau 

of Mines specifications 57 at the American Shale Oil 

Co.'s camp. The oil yields from about half the samples 

were checked by duplicate tests. The uppermost 

group of beds in section A were collected on the West 

Fork of Parachute Creek in sees. 2 and 3, T. 5 S., R. 97 

W., Garfield County, Colo., and tested by J. W. 

Richards & Son, of Denver, for the Federal Oil Shale 

Co. Several thin beds in the lower part of section A 

i ( 

all have decidedly lower potential oil yields than the 

·adjacent beds. These occur at 8, 26, 56, 101}~, and 

103% feet belo~ the mahogany marker and, like the 

\' 

mahogany marker, are probably beds of altered volcanic ash. It is probable that they too have great 

lateral extent and could be used as horizon markers. 

The series of retort tests designated B in Plate 13 was 

furnished by the Columbia Shale Oil Co. It was nearly 

as long and showed almost as much differentiation of 

the beds as series A. The samples for this series. were 

collected by Mr. F. A. Goodale and two assistants on 

the East Middle ·Fork of Parachute Creek in sec. 16, T. 

5 S., R. 95 W., Garfield County, Colo. The oil yields 

were determined in standard test retorts at the Columb~a Shale Oil Co.'s camp, in sec. 16, by Mr. Goodale and 

his assistants. 

The series of tests designated C in Plate 13 was furnished by the Ute Oil Co. The samples were collected 

in the canyon of the White River in sec. 5, T. 10 S., R. 

25 E. Salt Lake meridian, Uintah County, Utah, by 

Mr. Thomas J. Davis and his assistants. The tests 

were made in small test retorts comparable to those 

recommended by the United States Bureau of Mines at 

the Ute Oil Co.'s camp in sec. 5, T. 9 S., R. 25 E. This 

"Personal communication, Dec. 18, 1927. 17 Karrick, L. C., Manual of testing methods for oil shale and shale oil: u. s. 

Bur. Mines Bull. 249, pp. 2-28, 1926. 

series of tes.ts was considerably shorter than the others,. 

and the samples tested represented groups of beds 

rather than individual beds as in the other two series. 

Nevertheless it affords an interesting comparison of the 

oil-shale beds in the extreme eastern part of the Uinta. 

Basin with th'Ose in the deepest part of the Piceance 

Creek Basin; represented by series A and B. 

SEDIMENTARY STRUCTURE IN THE OIL SHALE AND 

ASSOCIATED ROCKS 

MAJOR FEATURES OF BEDDING 

REGULAR BEDS AND THEIR SIGNlFICANCE 

In general the bedding of the oil-shale groups is thin 

and regular. Bed follows bed with 1nonotonous uniformity through series measured in hundreds of feet. 

Slight differences in texture, relief, and color tone serve 

to distinguish the beds. Planes that appear to be geometrically perfect separate them. Such sharply defined beds range in thickness from a few inches to about 

29 feet and repr~sent units of sedimentation separated 

from one another by apparently abrupt changes in 

conditions. These abrupt changes may have been 

caused by breaks in sedimentation or merely by quick 

changes in the kinds of material deposited. The sharp. 

change from dense marlstone which is banded with 

more or less regularly spaced fine laminae colored brown 

by organic matter to rich oil shale indicates a marked 

change in the conditions of deposition. 

The leaner beds of dense marls tone with their minute ,. sharply defined varves, which average about 0.15 millimeter in thickness, must have been deposited in very 

quiet water. Otherwise the organic matter, which 

was an ooze at the time of deposition would have been 

stirred up and scattered through the deposit, giving it 

a nearly homogeneous and lighter-brown color. Probably these varved beds accumulated in water so deep 

that waves and ordinary currents had pract~Cflly n() 

effect upon them. At rare intervals small groups of 

varves in these beds have evidently been disturbed,. 

for the lamination has been almost wholly effaced and 

organic matter is diffused through zones a few milli- · 

meters thick. Apparently much of the rich oil shale 

als9 accumulated in relatively deep water, for it has an 

analogous laminate structure, but on the other hand 

many beds seem as clearly to have accumulated in 

shallow water at stages when the area of the lake was 

considerably reduced. The evidence upon which this 

conclusion is based is summarized on pages 28-29. 

Certain of these abrupt changes in lithology are rhythmic and appear to be related to cyclic changes of climate · 

induced by the precession of the equinoxes. At a horizon roughly 150 feet above the "mahogany ledge" is a 

small group of beds of oil shale a11;d organic marlstone 

that altema~e in a regular manner. This group has 

been recognized at three localities in Garfield County, 

Colo.-near the head of the East Middle Fork of Parachute Creek, in sec. 16, T. 5 S., R. 95 W.; on the north 
SEDIMENTARY STRUCTURE IN THE OIL SHALE AND ASSOCIATED ROCKS ·25 

side of Cathedral Creek, aiproxim~tely in sec. :16; T. . At s few places, high itt the formation, the writet 

3 S., R. 99 W.; and on Clea Creek m sec. 9, T. 5 S., R·. fmmd very short stubby lenses of rich oil shale tha-t 

98 W. Most of the beds o organic marlstone, which clearly had been deposited in small dishlik:e depres-r 

contain fly lariae in remarJFable abundance, are about sions. Some of these short lenses found about 2,300 

6 feet thick, and the beds. <))f oil shale average a little feet above the base of the Parachute Creek section 

less than 2 feet tJ.ick. According to the rates of accu- rest in irregular depressions in the upper surface of 

mulation indicated by varves in rock of these two types a low-grade oil-shale bed and are overlain by a bed 

each sedimentary cycle, wlttich is represented by one of earthy and somewhat carbonaceous marl. Most of 

oil-shale bed and one marlstone bed, has an average these lenses are less than 1 foot long and from 1 to 3 

interval of a little more than 21,600 years.58 The inches thick. ,All end abruptly, wedging out from the 

average interval of the pre¢ession cycle and the cycle ·maximum thickness within 4 or 5 inches along the bed. 

of the change in eccentricit~'of the earth-'s orbit is about These short stubby lenses seem to have accumulated 

21,000 years. in small isolated pools that filled the depressions which 

The significance of the ot er similar but nonrhythmic the lens~s now occupv. Thus they appear to corroboabrupt changes of litholo is obscure, but it seems rate otHer evidence that at certain stages the ancient 

likely that the dominant factors were climatic, for the lake contracted greatly, so that large areas of the botdifferences between successive beds lie chiefly in the tom were exposed to the ai_r. It is difficult to imagine 

content of organic matter .rather than in the miner- such small pools having existed over periods of time 

alogy, and the rate of production of organic matter in long enough for the production of so much organic 

lakes depends largely upon the temperature. Changes matter unless thew ater table was practically coincident 

in rate of warping of the lake bottom and other like with the surface of the lake bottom, so that in effect 

physical changes probably would have been too gradual these small disconnected pools were furnished ·with 

to cause such abrupt changes in the sediments. .But, spring water a.t a rate about equal to the. evaporation. 

whateve~ the causes, it seems necessary, in order to Of course, the water level must have been subject to 

· r.ccoun ior the abruptness of these changes, to assume rPpeated changes from this assumed stable equilibrium. 

that C\ .aditions favorable tithe formation of one type Some indication, of these supposed changes is furnished 

of sedin1ent, once establish d, were fairly stable until by irregular, somewhat contorted limy layers within 

a certain critical point was r, ached, when they changed the oil shale, which the writer regards as deposits 

rather quickly to another set of conditions which were forn1ed at stages of higher water and then later warped 

equally stable but which f~;tvored the formation of a and distorted by drying out when exposed to the air .. 

somewhat different kind of sediment. In 1924 the writer found small isolated spring-fed 

LENTICULAR BEDS AND THEIR SIGNMCANCE I • 

Not all oil-shale beds in the Green River formation 

are so extensive or so reg~arly bedded as those just 

described. On the contrary, many are exceedingly 

irregular either in thicknesb or in structure, or both. 

A great many beds of oil shale, especially those not 

included in the two chief oil-shale units, are lenticular. 

Most of these lenses are mte1calated between: relatively thick units of low-g11ade oil shale. They vary 

greatly in size and proportions. The most plentiful are lenses· ·of very rich oil shale from half an inch 

to about 3 inches thick in the center and from about 

15 feet to about 300 feet long. These taper uniformly 

to very t~ but well-defi.ned edges. Some lenses of 

these proportions, however~ appeal' to be merely local 

thickenings of very thin, nlmlike layers of . organic 

matter which can be dis~ned only with difficulty. 

Locally thicker beds finger out into beds of low-grade 

oil shale by splitting up in several long, thin wedges 

whose rate of taper is abo 1t equivalent to that just 

described for the individual thin lenses. Presumably 

such thin lenses of oil shale accumUlated in residual 

pools in the lake bottom. 

i8 Bradley, W. H., The varves and clinutte of the Green River epoch: U.S. Geol. 

Survey Prof. Paper 158, pp. 1os-100, 1929. 

pools similar to those just postulated on the terraces 

of Strawberry Cl!eek in sec. 12, T. 2 N., R. 95 W., Rio 

Blanco County, Colo. These terraces consi&t of sandy 

clay derived chiefly from the Wasatch formation. 

The. pools were fed at a rate apparently just balanced . 

by the rate of evaporation, for they did not overflow~ 

They contained a prodigious quantity of organic mat~ 

ter, chiefly blue-green algae. Decay was going o~ 

along with the rank growth of vegetable matter. The 

whole mass, which was about 6 inches deep, had the 

consistency of very thick soup and supported countless 

nematodes and a lesser number of small dipterous 

larvae. In 1925 the writer found similar though 

somewhat larger spring-fed pools that were nearly as 

thick with living and decomposing aquatic organisms 

in the valley of the Strawberry River in the eastern 

part of Wasatch County, Utah, and again on the broad 

mud flat on the, west side of Little Salt Lake near 

Pa't'owan, Utah .. 

The soft, earthy, and somewhat carbonaceous marl 

that immediately overlies the short stubby lenses of 

oil shale n·ear the top of the Parachute Creek section of 

the Green River formation is interpreted as a deposit 

~omewhat akin to material now accumulating in places 

along the margins and out on the mud flats of Abert 

Lake, in southern Oregon, and Little Salt Lake, in 
26 ORIGIN AND MICRO.FOSSILS OF OIL SHALJJ OF GREEN RIVER FORMATION 

Utah, where there is a rather sparse stand of sedges. 

Such a deposit, therefore, is regarded as indicating a 

period of time following the oil-shale deposition when 

the lake bottom at that place was exposed to air. 

MINOR FEATURES OF STRATIFICATION 

LAJIDrATIOll 

The distinction between bedding and lamination 

is one of size, and Twenhofel's suggestion 59 that 

the term "laminae " be restricted to layers less 

than half an inch thick is followed in describing the· 

sedimentary structure of the oil shale and related 

rocks of the Green River formation. 

With a very few exceptions the beds of oil shale 

are thinly laminated. A few beds of fine-grained 

limy sandstone contain laminae near the maximum 

thickness, and some rich oil-shale beds have no 

discernible lamination. In a rough way, the greater 

the proportion of organic matter in the rock the 

thinner the laminae. Thus in some of the poorer 

grades of oil shale the laminae may be as much as 

0.5 millimeter thick, but in the higher-grade shales 

they may be as thin as 0.014 millimeter. (See pl.14, B.) 

In most beds, however, the laminae are grouped 

more or less regularly, so that in the hand specimen 

the lamination appears to be somewhat coarser than 

it really is. 

The lamination is due to an alternation of layers 

rich and lean in organic matter. In some beds the 

lamination is rhythmic, but in others it seems to be 

unsystematic. The rhythmic laminae have been 

interpreted by the writer as varves, ·and as their 

origin and significance have been fl:llly discussed in 

ano.ther report 60 it will suffice here merely to summarize 

the conclusions drawn from that investigation. Each 

varve consists of two laminae, one of which is made 

up principally of carbonate and clay particles and 

the other chiefly of structureless organic matter. 

This bipartite structure of the varves is explained 

in part by the differential settling rates of the two 

groups of constituents and in part· by assuming 

essentially continuous sedimentation . of the mineral 

and organic constituen~, with first a peak in the 

production of the carbonates and then a peak in 

that of the plankton. Both peaks apparently occurred 

in the summer. The varves differ considerably in 

t~ickness, according to the kind of rock in which 

they occur, ranging from a minimum of 0.014 millimeter in the beds of richest oil shale to about 9.8 

millimeters in the beds of fine-grained sandstone. 

The time value of the varves is tested by analogy 

with the varves in the deposits of certain modem 

lakes. and also by calculating from data m1 present 

stream loads the thickness of annual laminae to be 

expected in the ancient Gosiute Lake. On the basis 

69 Twenhofel, W. H., Treatise on sedimentation, p. 432, 1926. 

oo Bradley, W. H., op. cit. (Prof. Paper 158), pp. 87-110. · 

of th~ varves the ·writer estimates that the Green 

River epoch lasted· between 5,000,000 and 8,000,000 

years. 

Not all the thin laminae in the oil shale and related 

rocks are as regular and persistent as the varves. 

In some beds, particularly the richer oil-shale beds, 

the laminae are lenticular. The organic laminae 

range in length from about 1.5 to about 7.3 millimeters and in thickness from about 0.015 to about 

0.075 millimeter. The lenses of mineral grains are 

a little thicker and range in length from about 0.5 · 

to about 2 millimeters, but they are ill defined, and 

most of them terminate by an insensible gradation 

into the organic matter. Although they are characteristically thin, they appear,.locally, to be transitional in to larger, sharply defined concretionary lenses 

of mineral grains which range from about 0.25 to 

20 or more millimeters in length and whose thickness 

is about . one-fourth the length. This transition 

into distinct concretions suggests that the lenticula-r 

mineral laminae may owe their form to a rather weak 

tendency for the mineral grains to aggregate into 

concretionary masses. Nevertheless it is equally 

reasonable to suppose that their form may be entirely 

original. They may be the mineral laminae of varves 

that were deposited in slight depressions in the 

organic ooze, or the mineral particles may have been 

assembled by feeble water currents at the time of 

deposition. 

OOIITOI.TID BEDDIBG · 

Contorted bedding is common in bed& of the Green 

River formation above the . basal zone. In general 

it is more common in high-grade oil shale than in 

low-grade oil shale, but locally beds of sandy shale, 

·marlstone, and even fine...grained sandstone show it. 

· In the ·section measured along Parachute Creek contorted bedding was found at 23 different horizons. 

At 20 of these the structure was in high-grade oil 

shale, at two it was in dense marlstone finely banded 

with laminae rich in organic matter, and at the other 

it was in a fine-grained limy sandstone. 

The flexures in the rich oil shale range in ooin.Jle:xity . 

from rather simple folds whose axial• planes are con.; 

siderably inclined from the vertical, through large 

overfolds upon which one or two sets of minor folds 

are imposed, to extremely intricate plications and loa.g 

overthrusts whose thrust plAnes undulate. (See pl. 14, 

A.) Practically all the deformation in these beds 

occurred when the material was plastic enough to 

yield readily without fracturing and yet firm enough to 

retain its form after deformation. Only in a few places 

are the strata broken at rather obtuse angles to the bedding, and where parts of one. bed overrode the lower 

parts the laminae are drawn out greatly along. ·the 

gliding surface. Consequently the gliding surf&ce$ 

are not sharply defined, because the material which is 

drawn out into "schlieren" blends insensibly into other 
• 

-,--

U. S, GEOLOGICAL 8URV111T 

A 

Oil yields of oil-sllale beds in the Parachute 

Creek be~ oHM Green 

--lliililormalon oo ~~~ Cre<k and Wesl 

PROFESSIONAL PA.t'Ellt 168 PLJI.TG l~ 

felt of Parachute Cfeek (lOwer part, sec. 9~ 

T. 5 S., R. 98 W.; upper p2rt, sees. 2 and 3, 

l 5 ~ .• R. 97 W. .•. CoiOfado) as indicated by 

retort tests of the American Sl\ale Oil Co. by 

Flavius Wocd and of the Federal Shale Oil 

Co. by J. W. Richa~ & San. 

GALLONS PER TON 

0 1,0 2Q 30 '10 50 

8 

Oil yields of oil-shale beds in the Parachute 

Creek and Evacuation Creek members Gf tile 

Green Rivel. formation near the ltead ~~ East 

Middle F<lrll of Parachute Creek (see. 16, 

T. 5 S., R. 95 W., Coklrado) as indicated by 

retort tests of tht Colu'mbia O,il Shale "-.Re. 

fining Co. by F. A. Goodale. 

PER TON 

30 '10 5ll. 

c 

Oil yields of oil-shale Deds In a p11t of Ill 

Plrldlute Creell memt. of the 6rw .., lomlltiOil on White RiVer (T. 9 S., R. 25 [ 

Salt Lillie meridian, Uintah Collllly, Utili) • 

indicated by retort tests of the IIIII 01 Co. 

GALLONS PER TON 

0 10 20 30 >40 50 

GRAPHIC SECTIONS jSHOWINGj,THE OIL YIELDS OF OIL-SHALE 

BEDS IN THE GREEN RIVER FORMATION 

A. Results ol retort testa on aamplm of oil lhale oollected on Cleat Cre&k, sec. 9, T, 5 S., R. 98 W. and on We~~t Fork ol Parachute Croek in 8«::1. 

2 e.nd 3, T. 5 S .. R. 97 W~t.OOth in Gar6eld County,~. Colo. De.ta~pptied by F1o.vius WO(Id and J. w. RicluU'~ & Son, H. n esnlta ol ~t teats on eamplt'l!l of oil $hale collected on Eut Middle Fork of Parachute Creek, -.. l61 _T. 5 8.:1 R. 95 W., Garfield Coun\y, Colo. Data 1upplied by 

Columnia Oil ~hale Co. C. Reoulta ot """"- test'l on aamples ot oD 1ho.le collected in the co.nyon ol White Rlv..-, T. 9 S., R. 25 E., Salt Lake Meridian, Uint.a.h ,C01mty, Utab. ThltaiiUpplied by the Ute Oil Co. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 14 

A . CONTORTED BEDDING DUE TO DIF:FERENTIAL COMPACTION IN A RED OF OIL SHALE 

NEAR THE MOUTH OF PICEANCE CREEK, COLO. 

B. PHOTOMICROGRAPH OF A THIN SECTION OF RICH OIL SHALE FROM THE "MAHOGANY 

LEDGE" NEAR THE HEAD OF CLEAR CREEK, IN SEC. 9, T . 5 S., R. 98 W., GARFIELD 

COUNTY, COLO. 

Shows t.hin regular lamination (varves). The black partS are organic matter, and the light-gray areas are mineral grains. 

• 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 15 

A. MOSAIC BRECCIA IN OIL SHALE SHOWING THE CONTRAST ON A WEATHERED SURFACE BETWEEN THE 

FLAKES OF VERY RICH OIL SHALE AND THE SLJGHTLY LESS RICH MATRIX 

B. THIN BED OF FAIRLY RICH OIL SHALE WHICH FAILED LOCALLY UNDER STRESSES DUE TO DIFFERENTIAL COMPACTION 

BY DISTRIBUTIVE THRUST FAULTS 

Other parts of the same hcd yielded hy folding. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 16 

A . SPECIMEN OF OIL-SHALE BRECCIA 

Shows a large fragment in the middle, oriented at a small angle with the normal bedding so that it shows its own lamination, which is quite different from that of the rock. Upon that upturned fragment is a patch 

of Lepidosleus scales. 

B. COARSE SHALE BRECCIA IN FAIRLY RICH OIL SHALE FROM PICEANCE CREEK, COJ,O. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 17 

A. THIN SECTION OF A RICH OIL SHALE SHOWING SEVERAL RELATIVELY LARGE CONCRETIONS AND AN 

ABUNDANCE OF MINUTE CONCRETIONS, ALL OF MICROGRANULAR CARBONATES 

B. OIL SHALE FROM PARACHUTE CREEK, COLO., SHOWING "LOOP BEDDING" 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 18 

THIN SECTION OF .A RICH OIL-SHALE BED FROM ASPHALT TUNNEL, SEC. 1, T. 7 .s., R. 98·W., GARFIELD COUNTY, COLO., SHOWING FIGURED ORGANIC 

MATERIAL EMBEDDED IN A STRUCTURELESS ORGANIC GROUNDMASS 

This photomicrograph shows the spines of insect larvae, probably a species of Oestridae, still arranged in tiers. It also shows parts of larval skins (the large black areas) and fragments of the eyes and wings of minute adult insects. 
SEDIMENTARY'· STRUCTURE IN· THE OIL SHALE AND . .ASSOCU.TED ROClaJ 27 

par~ of the bed, where the .bedding laminae are 

neverthelesS plainly. truncated. . 

In· ·,some beds of oil shale· the differential movement 

has resulted in true "schuppen" structure. (See pl. 151 

B.) In the hand specimen illustrated each plate is 

about 6 centimeters long and 7 to 10 millimeters thick. 

The thrust planes are inclined approximately 25° from 

the horizontal; and the faulted zone has been shortened· 

from about 41 centimeters to about 17 centimeters, or 

reduced to one-third its original length. This fault 

zone is about 4 feet long and therefore represents a 

differential movement of about 12 feet. Other· parts 

of this same thin bed were evidently more plastic, for 

they yielded by folding. 

Steep distributive thrust faults whose fault surfaces 

are somewhat obscured by merging of the wet, partly 

plastic material- were found in beds of dense marlstone that is finely banded with dark-brown organic 

laminae.. . 

Any of ·several factors may have been dominant 

causes of the contorted bedding and microfaulting. 

Floating ice that dragged along the bottom produced a 

comparable disturbance of the deposits in certain 

glacial lakes, but as there is no evidence to indicate the 

presence of ice in the ancient Green River lakes and 

much evidence that suggests its absence this possible 

· cause may be ruled out as improbable. Deposition of 

the ooze upon a part of the lake bottom that sloped 

gently, so that a considerable .thickness· could be built 

up before the stress tending to. make the material 

adjust. itself to the inclination exceeded the rigidity, 

seems somewhat more likely. Now .some of the oilshale beds whose laminae are deformed by flowage are 

as much as 3 feet thick. Before compaction by overlying deposits and before dehydration and shrinkage of· 

the orga.ruc matter such a bed, according to an estimate 

by W. W. Rubey,61 of the Geological Survey, may 

have been about 30 feet thick. But during compaction 

an organic ooze of that sort loses water and becomes 

less fluid and more gel-like. Core samples of the 

deposits·in a certain modern lake show that the ooze a 

few inches. below the surface has a jellylike consistency 62 

firm enough to retain its laminated structure. Therefore it may be that thick beds of plastic ooze would 

yield by folding and flowage and where stiffer, even by 

faulting, to adjust themselves to. a slight inclination 

of the bed apon which they accumulated. Essentially 

the sanie result might be produced by local abnormally 

rapid sedimentation. In the shallower parts of the 

lake the growth of organisms and also the precipitation 

of carb()nates may have been appreciably more rapid 

than in the deeper parts, by reason of the slightly 

higher temperature. Thus the organic ooze may have 

accumulated more rapidly in places an<:{ built low 

01 Oral communication. 12 Whittaker, E. J., Bottom deposits of McKay Lake, Ottawa: Roy. Soc. Canada 

Trans., sec. 4, vol. 16, pp. 15o-153, 1922. 

36544-31-. ~ 

ridges or perhaps reef .. like thiekeiiin.gs of the- ooze 

layer~ Such irregularities would· probably· tend to 

adjust themselves, either by :ftowiil.g near. the surface 

if the angle of repose were exceeded or by squeezing 

out from under the loaded areas .. Local loading of 

ooze beds might· also have occurred in other ways~ 

such as the building out of deltas or sublacustrine slides 

like those described by Heim 63 as occurring in the lake 

of Zug, Switz·erland, which were due to oversteepening 

of the shores by local erosion. But these means see:ni 

less probable in shallow lakes that had nearly flat 

shores. 

The differential movements and readjustments 

within and between the beds after burial and during 

compaction of the sediments may ·perhaps ·account 

more adequately for the contorted· bedding. The 

irregularities in thickness of an essentially homogeneous bed of ooze would tend to smooth themselves 

·out and so cause movement of the material from one 

part of the layer to another. Again, lenses poor in 

organic matter or lense"S in which the mineral grains 

were for some reason unusually coarse would be less 

compacted than other parts and so would produce 

local thickenings in the layer that contained them. 

Then during further compaction such irregular beds, 

would cause· unequal pressure and differential movement in adjacent more readily compactible beds. As 

a large part of the compaction of an argillaceous 

sedim~nt occurs before .it has been buried more than, 

about 100 feet, the contortion of the beds probably 

occurred when they were only shallowly buried and 

while at least some of the layers. were still plastic. In 

beds containing about equal quantities of organic 

matter presumably those that contained a relatively 

large proportion of clay minerals would remain plasticlonger than those that contained an abundance of 

calcium and magnesium carbonates, which would be 

likely to harden relatively rapidly. These mineralogic differences may be a part of the reason why 

certain oil-shale beds and particularly why thin layers 

within a bed are contorted, whereas others immediately adjacent and apparently identical are not. This 

suggested correlation between the miri.eralogy and 

contorted bedding has not been adequately tested, 

but of 10 thin sections from as many samples of oil 

shale that showed contorted bedding, 6 contained a 

large proportion of micaceous clay minerals and 4 

contained chiefly carbonate grains,· though 1 of these 

was exceptionally fine grained. All wer.e very rich in 

organic matter. To summarize, it seems likely that 

contorted bedding due to differential stresses duringcompaction would be most commonly localized in 

beds that contained an abundance of organic matter, 

a relatively large proportion of micaceous clay minerals, and an unusually fine grained miperal aggregat~. 

ea Heim, Arnold, tiber rezente und fossile subaquatische Ru~hungen und deren 

lithologiscbe Bedeutung: li'eues Jahrb., 1908, Band 2, pp. 137-141. · · · 
.. · 

28 ORIGIN AND MICROFOSSILS OF OIL SH.A.LE .OF GREEN .RIVER FOJUrlATION 

A rather different explanation for the contorted 

bed.ding in the oil shale was proposed by David White 

in discussing a paper presented by Winchester 64· to 

the Geological Society of Washington. He suggested 

that inasmuch as the organic muds must have remained 

soft for a long tinie after being deeply buried, they 

were probably deformed by differential movements 

between somewhat more competent beds above and 

below. This suggestion seems to imply that these 

movements were related to crustal warping. 

SHALl BRECCIAS 

Many of the rich oil-shale beds are apparently 

brecciated. They are not strictly breccias, however, 

for the beds themselves are not broken up. Instead 

they contain as inclusions many comparatively large 

angular fragments or flakes of more or less similar 

rock, which are clearly derived from the breaking up 

of a bed elsewhere. These fragments, then, are 

simply embedded in an oil shale which except for the 

irregular lamination is a normal oil shale. The pieces 

range in size from tiny flakes' to fragments as much 

as 3 inches long." Most of them consist of oil shale· 

whose content of organic matter differs enough from. 

that of the matrix to make them easily distinguishable 

on the weathered surface. (See pl. 15, A.) Not all 

the fragments, however, are oil shale, some consist of 

marlstone. These weather buff or reddish yellow and 

are particularly conspicuous on the weathered surface 

of the rock. Most of the fragments in the shale breccias are flat and chiplike, or flakelike and are oriented 

nearly parallel to the normal beddmg. But some are 

tilted at rather large angles and on their weathered 

edges show plainly their own lamination. (See pl. 16, 

A.) In general the boundaries of the pieces within 

a breccia are sharply defined, indicating that the fragments were hard before being embedded. Yet in 

some beds the fragments are rounded at the angles, 

have indistinct boundaries, and are drawn out into 

threadlike stringers that merge with the matrix. 

Moreover, several pieces that were turned so that their 

lamination was normal to the regular' bedding were 

apparently soft enough to settle down, probably during compaction of the beds, with the result that they 

are rather minutely crenulated. In one bed a few 

pieces of marlstone are curved upward at the margins, 

suggesting mud curls, but the evidence is not conclusive. Only one of these beds has contorted bedding, and aside from the gentle irregularities of the 

lamination around the foreign fragments they appear 

to be normal beds of oil shale. 

· Two sorts of oil-shale breccias were distinguished in 

the field. One contains coarse fragments of both oil 

sh~le and marlstone which are in generar oriented at 

appreciable angles to the bedding. (See pl. 16, B.) 

tj Winchester, p,·E., Contorted bituminous shale of the Green River formation · 

in northwestern Colorado: Washington .Acad. Sci. Jour., vol. 9, p. 295, 1919, 

These seem to be most common near the margins of th~ 

basins, although one bed in the. ~cinity .of· Parach-u.t~ 

Creek was locally brecciated in this. manner.' ShAle 

breccias of this sort are not to be confused With beds 

of oil shale that contain abundant thin, fia.k~lik.e lense~ of iron-stained dolomite and calcite and thin ironstained concretions. Thin sections show that such 

inclusions are merely the thin carbonate-rich laminae 

of the normal oil shale or else incipient concretion&. 

The other kind of oil-shale b:reccia contains great 

numbers of small flakes of richer oil shale;. most of 

which are oriented nearly parallel to the lamination 

of the bed that contains them. (See pL 15, A.) 

Shale breccia of this type, which may ·be termed a 

mosaic breccia,65 is much more common than the 

coarser breccia and is particularly abundant in the 

vicinity of. Cathedral Creek, Colo., where it was.found 

at 13 different horizons. 

White 66 has called attention to the brecciated structure in the oil shale of the . Green River formatipn, 

which he explains as follows: 

The organic muds were evidently subject to sun cracking 

and scaling-, and in some cases fragments of the scales appear to 

have fallen into sun cracks. The concentrateq h1.1mic substances, being insoluble in water after once becoming dry, impart 

a degree of hardness and toughness or rigidity to the scales of 

sun-cracked organic muds, tending to preserve their integrity 

· of form and relations when .ap-ain they are submerged. 

This explanation seems adequate to account for the 

brecciated structure. Apparently the dried and hardened scales and flakes were mixed with m<?re organic 

ooze upon rise of the water level, for they appear to be 

embedded through several inches of otherwise nonnal 

oil shale. · The :Qatness of the particles is perhaps to be 

explain~ by a certain amount of softening when wetted again, or by compaction of the beds. 

It seems rather likely that· the shale flakes in these 

beds were derived from areas of the lake. bottom that 

stood a llttle above the water level duriri.g the low 

stages of the lake. Thus these shale breccias may not 

have any relation to the position of the shore lines. 

They do, however, provide strong evidence that locally, 

at least, the lakes repeatedly became very shallow and· 

furthermore that at these stages there was practically 

no rainfall. This conclusion accords with other evidence that the climate was characterized by a seasonal·. 

distribution of the rainfall.67 

XlJ'D CRACKS 

Mud cracks are very plentiful in some parts of the 

Green River formation, as in th~ section measured 

along Indian Canyon, Duchesne County, Utah, where 

they were found at 51 different horizons. Moreover, 

u Norton, W. H., Studies for students; a classification of breccias: .Jour. GeologY, 

vol. 25, p. 161, 1917. 

oo White, David, The carbonaceoUs sediments, in Twenhofel, W. H., Treatise on 

sedimentation, p. 302, 1926. 

or Bradley, w; H.~ Tbe varvesand·cUmate ofthe GTeen·River·epoob:·U. s. Geol. 

S1,1rvey Prof. Paper 158, pp. 90-95, 1929. 

- ' -· ·~ 
. MINERALOGY 

· at most ·of. -these ·horizons m~y: bedc:tirig planes· are 

cracked. White 18 . also found . mud~racked beds. of 

high-grade oil shale in the Green River formation in· 

northeastern Utah. 

Sharply defined mud cracks filled with light·gray 

mudstone were found by the writer on the bedding 

planes of rich oil shale at about 3,100, 3,400, and 3,450 

feet above the base of the "formation near the head of 

Avintaquin Canyon, about sec. 27, T. 10 S., R. 8 W., 

Duchesne County, Utah.· The uppermost of these 

beds· is particularly significant, ·for the thin,. mudcracked laminae also show mosaic- brecciation, a fact 

which strengthens the · hypothesis that the shale 

breccias are due to desiccation. · The leaner shale and 

siltstone beds associated with the mud-cracked rich 

oil-shale beds in this part of the section are alsO mud 

cracked. A bed of ·rather low grade oil shale with 

excellent mudstone-filled mud: cracks on its upper 

·surface was found about 850 feet above the base of the 

formation in the canyon of the White River in sec. 27, 

T. 9 S., R. 25 E., Uintah County, Utah. Upon. that 

· mud-cracked surface rests a thin bed of very rich -oil 

shale. · 

. Comparatively few bedding planes of the oil shale 

are exposed so that the surface features can be seen, 

but the edges of the beds in the cliff face show plainly 

a structure which the writer ';regards as possibly due 

to mud cracks and which he recorded in his field 

notes as "loop bedding." Small groups of laminae 

that are otherwise quite regular are sharply constricted 

or even end abruptly at intervals, giving the effect 

of long, thin loops or links of a chain. (See pl. 17, B.) 

The groups of laminae so interrupted range from 

about one-sixteenth to about one-fourth inch in thickness. The intervals ~etween constrictions range 

from about three-eighths inch to more than 5 inches. 

At the· constrictions the uppermost and lowermost 

laminae of the affected groups converge .abruptly 

and apparently pinch off the intervening laminae. 

Yet at many constrictions the upper and lower laminae 

do not end; instead they merely approach one another, 

then separate again to their normal distance apart. 

This detail of the structure can be best observed 

in thin sections. It is also clear from examination 

of thin sections and polished specimens of ''loopbedded" oil shale that the central laminae of such 

constricted groups have indefinite terminations, which 

apparently indicates that the structure was formed 

when the original mud or sapropel was· moist and 

plastic. These "loops" may possibly be explained 

as cross sections of mud cracks formed on a wet 

mud flat. The fact that the uppermost and lowermost laminae of each group are very ·clearly defined 

where they converge seems to preclude the possibility 

that the walls of the cracks were ever nearly vertical 

" ~bite, David, The carbonaceous sediments, in Twenhofel, W. H., Treatise on sedimentation, p. 302, fig. 43, 19'.!6. 

and were beh.t or slumped down at" the angle· when~ 

they were again covered by ~ater. Rather it' ~ms· 

that the mud dried out to a certain depth, so ~at. 

a surface .Jayer comprising a group of ·laminae ~l:l-'. 

tracted into polygonal blockS, which however,. shrank· 

more along the margins of the polygons, thus. beeotn .... 

ing. somewhat lentil-shaped. These units . may not· 

have dried sufficiently to curl up or, what is perhaps 

more ·probable, they were wet with more or less saline 

.water and consequently showed no, tendency to curl. 

The layers th.at ·broke· into lentil-like polygons were 

surely niuch thicker at the time the mud was cracked, 

and the. cracks may have been as :r.0.:uch as several 

inches deep. 

"Loop bedding" was observed only . in: bed~ of ' 

oil shale that were estimated to he_ capable o.tyield~ 

ing at least 15 gallons of 9il to the ton and only in, . 

that part of the .formation above the base of the 

Parachute Creek meinber. Furthermore, in that part. 

of the formation many of the richer beds contain 

an abundance of salt crystal cavities. Beds that· 

contain "loop bedding" were observed at 23 horizons·' 

in the Parachute Creek section, 10 horizons in the 

Cathedral Creek section, and 10 horizons in the., 

White River section in Utah. "Loop bedding" 

was not studied ·very critically in the field, where 

· its significance was not realized, and it is probable i 

that a careful search would reveal this structure at 

many more horizons in the·upper part of the forination. 

KIN'DALOGY 

SYNGENETIC MINERALS 

Calcite and dolomite.-Calcite and dolomite are the ~ 

predominant minerals of both the rich a.nd the lean • 

oil-shale beds ·of the Green River formation. The ' 

grams, which are essentially equidimensional, average 

about 0.008 millimeter in diameter, but some are 

less than· 0.001 millimeter and a few as much· as 0.038> . 

millimeter. Perfect rhombs of either dolomite orcalcite are also fairly plentiful and are 'of about the 

same order of size. It seems more likely that these 

idiomorphic crystals are dolomite, but th~re is no 

evident relation between the number of rhombohedral 

crystals and· the ma.gnesium content of the shale. 

Lime and magnesia determinations have been made 

on 10 different samples of oil ~hale, and the relative . 

proportions. of dolomite and calcite in these ro~ks. , 

have. been calculated. In these calculations it was , 

assumed that all the MgO was combined as dolomite .. 

One shale from Fossil Butte, Wyo., contains 45.3-. 

per cent of dolomite and 7.1 per cent of calcite, whereas · 

another from Green River, Wyo., contains 56.6 per 

cent of calcite and only 22.2 per cent of dolomite. 

These two samples represent the extremes. The, 

average of the other seven analyses shows · 35.6 per 

cent of dolomite and 16_.5 per cent of calcite. This. 
\ 

" 

ORIGIN AND MICROFOSSILS OF OIL 8JlAL'B: ·.oF GREEN RIVER FORMATION 

may be regard~d as a f~ir average for the dolomite. 

contimt of the Green River oil shales. 

~he dolomite was Ciearly formed before solidifica~<;m of th~~ ·rock, for the organic matter through 

w~ich. the fine carbon~te grains are scattered is almost 

whollY. __ impervious to solutions. The d«;.lomite may 

· have been formed by a simultaneous precipitation 

of ~]le calcium and magnesium carbonates, which 

later combined to form the double salt, or it niay 

have fonned by reaction between solutions of magnesium salts and the minute calcite grains soon after.· 

they were precipitated. Or again the dolomite may 

have been precipitated as the double salt. There 

is no petrographic evidence to favor any one of these 

hypotheses more than f!Lnother. Most of the grains 

of both dolomite and calcite are anhedral; some are 

eu~edraJ. There is apparently no differentiation in 

siz~~ between the two carbonates. 

According to Clarke 60 the experiments of Scheerer 

and Hoppe-Seyler showed that finely divided calcium 

carbonate will precipitate magnesium carbonate from 

its solution in sea water. Clarke also says that hi this 

process the mixed carbonates form and not true dolo~ 

mite, but that if given sufficient time they might unite 

in the col<J to produce dolomite, in much the same way 

that Klem~nt made· them combine rather rapidly by 

ele~ating the temperature. Van Tuyl/0 however, 

regards this process as less probable than a precipitation of the c~cite grains, which soon thereafter react 

with the magnesium salts in solution to form magnesium carbonate, which in tum immediately combines 

with the calcium carbonate to form dolomite. Some 

experimental work done ·under conditions more nearly 

simulating ·those within a decomposing organic ooze 

are eVidently necessary before the way in which 

the dolomite of the oil shale was formed can be 

determined. 

Analcite and sepiolite.-Analcite crystals are scatte;red through many oil-shale beds and in a few make 

u~~-as muc~ as 16 per cent by weight of the rock. The 

crjistals average about 0.065 millimeter in diameter 

but. range· from, about 0.004 to 0.15 millimeter. 

They are clear and wholly isotropic and contain inclu-. 

sions of minute irregular grains and rhombs of carbonates and tiny flakes of clay minerals. · In general, 

those larger than 0.03 or 0.04 millimeter in diameter 

have been distinctly flattened parallel to the bedding 

laminae. Vertical sections of some of these crystals 

show only vague or badly distorted crystal faces, but 

considered together with the horizohtal sections they 

~how that the crystals are clearly trapezohedrons that 

have been compressed to only about half their normal 

diameters during the coll}paction of the shale. Moreu Clarke, F. W ., The data of geochemistry, 5th ed.: U. S. Geol. Survey Bull. 770, 

p. 571,.1924. 

1o Van ·Tuyl, F. M., The origin of dolomite: Iowa Geol. Survey Bull. 45, pp. 40()-

-401, 1914. . 

over, these distorted crystals· oonta.in mMly irregular: 

cracks.· The general distortion of the arialelte Cry8tals· 

in oil shale seems to indieate that th&y. wer&~fOl"llledJ 

when the shale was only shallowly buried; for.·a·larg"e'. 

part of the compaction of an argillaceous sediment 

occurs before it has been buried to a depth of as much. 

as 100 feet. Minute ·apophyllite crystals are ra-ther· 

consistently associated with the analcite. Most of. 

these are prismatic and range_ between 0.02 and 0.03 

millimeter in length. Considerable evidenee has been 

assembled which indicates that both minerals were 

formed in place on the lake bottom as a result .of 

interactions between various s8J.ts dissolved in the. 

lake water and the dissolution ·products· of volcanic 

ash that fell into the lake. This evidence has been 

presented and fully discussed in another teport.71 

The principal inorganic constituent of a few thin 

beds of rather rich oil shale is 'fibrous sepiolite. Thesebeds, all of which are less than 1 centimeter thick, 

were found about 4,400· feet above. the base of the for .. 

mation in Indian Canyon, near- the lniddle ·ofT. 10 'S.; · 

R .. 7 W., Duchesne County, Utah. The weathered: 

surface is ligh:t bluish gray and has a distinctly silky 

luster. Below the weathered surface the rock ia;d&rk 

grayish brown. Like some other oil-shale strata of. 

this formation it has a pronounced fissility and 

resembles matted coarse brown-paper pulp. Unlike, 

other oil shales, however, it is light enough when dry 

to float on water. An analysis and the physical and 

optical. properties of the sepiolite have been· given. 

elsewhere by the writer.72 

Pyrite.-Pyrite occurs in various amounts in all the 

oil shale of the Green River formation. The· greater 

part of it is in subspherical or irregalar grains that 

range from 0.002 to about- 0.05 millimeter in diameter, 

but in some beds, particularly the very rich beds in the' 

eastern part of Uintah County, Utah, ·there are numer· 

ous discoid aggregates of microgranular ·pyrite from. 

0.5 to 3 millimeters across. In vertical section· it is 

clear that these aggregates have a sort of laminate 

structure and 'that the thin edges of successive disks· 

interfinger with the microscopic laminae of. the oil 

shale. Radial aggregates of elongate rodlets of pyrite. 

were alsQ . found in some beds,. but cubes or other 

crystal forms are less common. · 

Most if not all of the pyrite in the ·oil shale formed 

in place on the lake bottom while the organic ooze was 

still soft. Hydrogen sulphide is a characteristic by .... 

product of the putrefactive process through which the 

greater · pa.rt of the orgamc. matter in oil shale has· 

passed and during which nearly all the minute aquatic 

organisms were reduced to a more or less fluid gel. · 

Thus the organic ooze contained a plentiful supply of· 

hydrogen sulphide, which would have reacted with any 

n Bradley, W. H., The occurrence and origin of analcite and meerschaum beds in 

the Green River formation: U. S. Geol. Survey Prof. Paper 158, pp. 4-6, 1929. 

11 Idem, pp. 6-7. 
IQNERA.LOGY 

iron salts diSsOlved· in the 1J4{e water tO fOrm. iron sulphide. · This theory is ap:parently supported by the 

abundance of pyrite in tlie'orge,nie ooze now forming. 

Furthermore the pyrite so formed seems··to have a 

distinctive microgranular or rather microspharitic 

habit. Naumann 73 has described . in considerable 

detail thege minute spherioal or subspherical grains that 

characterize pyrite formed in putrescent organic lake 

ooze. These grains, which range from one to several 

thousandths of a millimeter in diameter, show a marked 

tendency to aggregate mto larger . spheroidal mas8es 

0.01 to about 0.025 millimeter in diameter. He found 

that minute grains and agglomerated masses of them 

occur together with cubical· grains of pyrite in the 

skeletal parts of dead plankton organisms, such as the 

Cjadocera, and within the cells of partly decomposed 

plant tissue. Clearly the pyrite forms contemporaneously with the decay of the organic· matter and therefore very soon after its deposition. Potonie 74 also has 

described minute spherical grains of pyrite within and 

associated with the remains of plankton org~nisms in 

the fetid organic ooze from the Black Sea. The. analogy between the occurrence of . microgranular pyrite 

in recent lacustrine organic ooze a.nd the occurrence 

of nearly identical granular aggregates of pyrite in the 

organic matter of. the oil shale leads the writer to 

believe that the pyrite in oil shale formed contemporaneously With the deposition and . putrefaction of the 

original organic ooze. Furthermore, the pyrite is 

more or less intimately intergrown with the' analcite 

crystals, which seem_ clearly to have formed soon after 

deposition of the ooze. A small quantity of marcasite 

was also found in some of the shale beds. 

Quartz and opal.-A few minute bipyramidal quartz. 

prisms were found in several rich oil-shale beds. These. 

seem to have grown while suspended in the organic 

ooze. Opal occurs in rather small quantities in the 

oil shale. 

C.LASTIC MINERALS · 

· The predominant clastic constituents of the oil shale 

are clay minerals belonging to the beidellite group. 

In some beds these minerals make up as much as 21 per 

cent of the rock. They occur as isolated micaceous 

flakes of irregular shape that range from 0.03 to 0.045 

millimeter in diameter or as minute lathlike flakes, 

few of which exceed 0.01 millimeter in length. According to the indices of refraction (a= 1.50; {1, 'Y = 1.54) 

n NauDlfUID, Einar, 'Vber das Auftreten der verscbiedenen Eisenverbindungen 

in den Hmnisohen· Ablagerungen: Sveriges geol. Undersokning Arsbok, ser. C, No. 

289, p. 39, 1918. 

1'4 Potoni~, H., Die rezenten Ksustoblolithe und ihre Lagerstatten: K. preuss. 

geol. Landesanstslt Abb., new ser., Heft 55, Band 1, p, 213, 190&. 

this miner8.1 probably oo*t~ s ·or 9 per cent t)f'iron, ,I 

and its composition is therefore near. that of the type 1. 

beidellite, w~ose composition. and optical properii~·l 

were determined by Ross and Shannpn~ 75 Gr~s of 

·quartz, sanidine, orthoclase and plagioclase feldspars, I 

muscovite, zircon, and apatite were also found· iri the 11 

oil shale, but they are not abundant. Quartz and j 

feldspar grains are more common than flakes of musco-·! 

vite and crystals of zircon . and apatite, which. are i 

really rare. Man:r- of the grains of quartz and feldsp;ar 1! 

are either sharply angular or subangUlar and range U,: 

size from about 0.01 to ab01it 0.16 millimeter. · How~ · 

ever, a fair proportion of the ~rurldine ·and orthoc~ase' 

crystals are euhedral, and in a few beds euhedra.l 

crystals of plagioclase, hornbl()nde, and pyroxene were 

found. ·In addition to these m.inerQ.}s some bedtt· · 

contain a few scatter~d fragments of volcanic glass 

which is partly replaced by analcite. The most.strik:+ 

ing feature of the clastic grains, other than· the clay 

m,inerals, is their complete lack of .sorting. an4 their 

random arrangement." They are not assembled in 

layers but disseminated through the deposit, and, the 

large and small sizes are. intermingled without sem."!' 

blance of order. This arrangement of the minerals , 

the predominance of .. sa.nidine over .orthoclase, the · 

association of euhedral crystals. of sanidine, orthoclase, : 

plagioclase, ferromagnesian minerals,· and volcanic : 

glass, and the prevalence of analcite and .apophyllite i 

imply that a -considerable portion of the clasticuiinerali 11 

are of volcanic origin. Moreover, thin ash beds. are ~ 

rather common in. the Parachute Creek member, i 

which is the oil-shale member of the Green River ! 

formation.· Neverthelesst' probably the.. ~ater part 1 

of the clastic materi'al was brought into :the lake by 

streams and distributed by currents. So.rne may also 

have come in as wind-blown dust, though no ·grams 

with a mat surface have been observed. 

The inorganic constituents of two samples of rich 

oil shale have been analyzed in the chemicallil.boratory 

of the United States Geological Survey. One of the8e 

samples (No. 17) was obtained just below the "mahogany ledge" in the Monarch Shale Oil Co.'s mine in 

sec. 32, T. 6 S., R. 97 W:, Garfield County; Colo., and 

is characterized by an abundance of analcite. ·The 

other (No. 111) came from the "mahogany ledge" 1 

near the head of the East Middle Fork of Parachute 

Creek, in sec. 10, T. 5 S., R. 95 W., Garfield County, 

Colo., and is characterized by a predominance of clay 

minerals. The analyses are given on page 32, together 

with the computed mineral composition. 

76 Ross, c. s., and Shannon, E. V., The chemical composition and optical proper· 

ties of beidellite: Washington ~cad. Sci. Jour., vot 15, pp. 467-468, lt25. 

... 
.~s 

I I _tfrl--

'i--·-

32 ORIGIN AND MICROFOSSILS OF OIL • SHALE OF GREEN RIVER FORMATION 

AnalyBeB of mineral portion of oil shales from the· Green River 

formation 

[1. G. Fairchild, analyst] 

Analysis Calculated mineral com~ition (per cent by wei t) 

17 111 17 111 

-- SiOa------- 26.51 22.89 Dolomite _______ 31.6 9. 3 

AlaOs-- ---- 5. 19 4. 77 Calcite _________ 6. 8 . 2 

MgQ FetOsa----- 2. 56 2. 97 Beidellite group_ 21. 0 ______ 6. 77 1. 94 Siderite ___ ----- . 2 CaQ _______ . 13.50 6. 29 Analcite ________ 17. 1 Naao __ . ____ ----- 2. 36 2.05 Quartz.,. _____ ,. __ 12. 1 10.4 

K20------- 1. 55 1. 52 Sanidine and or- H2o _______ . 22 . 22 thoclase ______ 7. 2 ----- TiOa------- . 20 . 20 Pyrite __ "-------~ 1. 6 2. 3 

ZrOa------ _ Faint -------- Potash fel.dspar _______ 2. 0 

trace? Collophamte ____ · . 4 1.1 COa:.~----- 18.27 4. 38 Apophylllte_____ 1. 0 1. 0 

-FtOs-- ----- . 02 . 48 Octahedrite_____ . 1 . 2 

SOa-------- Trace? Trace? Organics ______ ------ 1. 5 

s __ . __ ------ . 86 2. 66 Organic matter 

Loss on ig- minus com- nition, ___ 22. 17 49. 52 bined water.-_ 21. 6 46.1 

·,.1·'J ,,h 

Excess K20 _____ . 3 1. 1 }~ Excess Naao ____ ------ 2. 1 .-..I 

I t Excess Cao ____ ..., ------ 1.7 ---- 100. 18 99.89 100.0 100.0 

" From total Fe. .. • Loss on ignition less COs includes H20 of hydrous minerals. 

Estimated oil yield, No. 17, 38 gallons to the ton; No. 111, 

about 60 gallons to the ton. 

The mineral composition as calculated from the 

analysis of No. 17 is fairly satisfactory and agrees 

well with estimates of the more plentiful minerals 

made by petrographic methods. The quantity of 

dolomite was computed by calculatitig out MgO and 

CaO as magnesite and calcite and then uniting all 

the magnesite with a chemically equivalent amount 

of calcite. Collophanite was not recognized under 

the microscope, but it seems to be a reasonable mineral to postulate to account for the P20 5• Apophyllite 

was recognized, and its quantity estimated at about 

1 per cen't. The excess K20 is probably adsorbed on 

the finest mineral particles. 

The mineral composition as calculated from the 

analysis of No. 111 is much less satisfactory, yet it 

will serve to show approximately the proportions of 

the different minerals. In most beds of oil shale the 

carbonates predominate,. but in this rock clay minerals belonging to the beidellite group are the principal 

mineral constituents. The beidellite occurs as irregular flakes from 0.20 to about 0.1 millimeter in 

diameter. It is optically negative, its refractive 

indices are a= 1.50, ~' 'Y = 1.54, and the axial angle 

is .rather large. The other clay mineral occurs as 

v~ry minute lathlike flakes whose refractive indices 

are close to those of beidellite, b'ut the birefringence 

is lower. The quantities of beidellite, potash feldspar, and apophyllite were estimated under the 

microscope, and then the remaining Al20 3 was computed according to the formula of montmorillonite, 

which though formerly regarded· as a distinct mineral 

species is now regarded by C. S. Ross/6 of ·.the.·G~ 

-logical Survey, as a member of the b'eidellite · group 

of clay minerals. The excess CaO is puzzling, but 

the Na20 and K20 are probably in large part adsorbed 

on other small mineral particles. The rock contains 

also a very small quantity of analcite, which would 

account for a part of the excess Na20. In both rocks 

the quantity of organic matter was determined by 

subtracting the percentage of water in the hydrous 

minerals from· the loss on ignition minus C02• As 

small quantities of both vanadium and chromium are 

commonly associated with well petroleum, sample 17 · 

was tested for V203 and Cr20a, but no trace of either 

was found. 

SALINE MINERALS AND THEIR SIGNIFICANCE 

·salt-crystal cavities are very plentiful at certain 

levels in the Green .River formation. Some of these 

have been examined by W. F. Foshag, of the United 

States National Museum, and W. T. Schaller, of the 

United States Geological Survey, who have· measured 

.the angles and concluded that they probably represent 

glauberite and anhydrite. The occurrence of these 

crystal cavities and the measurements of the angles 

have been given in an earlier report.77 

The relative abundance of the salt molds in certain 

parts of the formation furnishes the basis for some 

interesting speculation as to the approximate length 

· of the stages of the ancient Uinta Lake .when it had 

no .outlet and the dissolved salts accumulated and also 

as to the stages when the lake appears to have been 

freshened by at least intermittent overflow. These 

. speculations are based in part on the distribution ·of the 

. salt niolds in the 'saline phase of the Green River formation as exposed in Indian Canyon, Utah, in part on 

tP.e distribution of salt molds in the Green River for-· 

mation in Wyoming, and in part also upon the inferred 

relations between the area of the ancient Gosiute Lake 

and its hydrographic basin (in Wyoming) and the 

climate that prevailed in the vicinity of that basin 

during the Green River .epoch. 78 

In the western part of the Uinta Basin, in the vicinity 

of Indian Canyon, the Green River formation contains 

a zone a little more than 800 feet thick in which molds 

of saline minerals are more or less plentiful. Glauberite(?) is the predominant mineral represented, but 

several thin beds contain pseudomorphS or molds of an 

·unknown mineral, presumably an. alkali salt. Units 

within this zone that contain molds of glauberite(?) 

range in thickness from a .few inches to 65 feet. Tbev 

are separated by units of shaly marlstone and shale, 

which are generally thinner and which show no trace 

76 Personal communication. . 

77 Bradley, w. H., The occurrence and origin of analcite and meerschaum beds in 

the Green River formation: U. 8. Geol. Survey Prof. Paper 158, p. 5, 1929. 

11 Bradley, w. H,, The varves and climate of the Green River epoch: U.s. Geol. 

Survey Prof. Paper 158, pp. 93-95, 106-:-107, 1929. · 
MINERALOGY 

of saline material. Nearly all the beds in this phase of 

the fonnation are limy, and most of them also contain 

some organic matter. A few of the beds, in fact, are · 

moderately good oil shale, but the others are of low 

grade. At places the rocks are silty or even sandy and 

micaceous, and at wide intervals in the unit there are 

thin beds of micaceous sandstone and muddy limestone. 

The prevailing color range of the rocks is from graybuff to light chocolate-brown, but in the upper part 

many beds have an odd pinkish or lavender tone. Mud 

cracks are characteristic of the entire saline phase and 

are Intimately associated with the impressions of the 

saline minerals. (See pl. 10, B.) The distribution of 

the various saline beds within the zone is shown in 

Figure 3. 

As in the rocks of the saline phase of the Green River 

formation near Green River, Wyo., the layers of glauberite(?) molds in many beds of this phase in the Uinta 

Basin recur at rather regular intervals. Yet in those 

beds in which .the molds make up perhaps as much as 

·50 per cent of the rock by volume either there is no 

rhythmic arrangement or· the cycle of salt deposition 

was so short that its effect is obscured by the closeness of 

the salt-niold layers and their relatively large size. On 

the other hand, molds are so sparsely scattered through 

· otherbedsthatnosystematicarrangementis discernible. 

In a specimen of comparable rock, though somewhat 

richer in organic matter, collected by the writer from 

the saline phase of the Green River formation in Wyoming the.average interval between layers of salt molds 

is 3.4 millimeters. According to the varves in the 

intervening layers of oil shale the interval of salt 

(glauberite?) deposition recurred about every 50 

years.79 

The writer estimates that each layer of salt molds in 

. this specimen represents a layer of solid glauberite 

about 0.5 millimeter thick. If this amount of material 

~ came into the lake in solution during each 50-year 

period intervening between times of salt deposition, then the annual increment of the constituentg 

necessary for glauberite would be equivalent to 0.01 

cubic centimeter or 0.27 gram of glauberite per 

square centimeter of lake bottom. This much glauberite contains 0.0186 gram of S04• A measure of the 

total dissolved solids in the streams feeding the lake 

can now be obtained if a ratio between the S04 and 

the total dissolved solids is assumed. For reasons 

explained below the Santa Maria River, in southern 

California, is taken as representative· of the ancient 

streams in the Green River region. According to 

Clarke 80 S04 constitutes about 52 per cent of the total 

dissolved solids in the water of this river. · Using this 

figure would . make the annual increment of total 

dissolved solids q.0276 gram for each square centimeter 

"Bradley, W. H., op. cit. (Prof. Paper 158), pp.l06-107. 

ae Clarke, F. W., The composition of the river and lake waters of the United States: 

u s. Geol. Survey Prof. Paper 135, p. 138, 1924. 

of lake bottom. Suppose next during each 50-year 

period the lake did not overflow but that evaporation 

balanced precipitation. Then the difference between 

the average annual precipitation over the land area of 

the drainage basin and the average annual evaporation 

from the land and plant surface· will represent the runoff, or the annual increment of stream water reaching 

the lake. According to the estimates of rainf-all and 

evaporation in the basin of the ancient Gosiute Lake 

given by the writer in an earlier paper,81 this figure is 

approximately 2.3 inches (5.84 centimeters). Hence, 

if the assumed annual increment of 0.0276 gram of 

dissolved solids per square centimeter of lake bottom 

was brought to the lake in the streams they must have 

had an average concentration of about 4, 700 parts 

per million of total dissolved solids. 

The Santa Maria River is a torrential river in a 

region with a semiarid climate. It has an exceptionally· 

large content of dissolved solids (2,412 parts per million), and of those solids S04 makes· up an exceptionally 

large p~rcentage. The Santa Maria ~iver was chosen 

for this calculation, not because it was regarded as 

havib.g a particuiarly close resemblance to the streams 

that. fed the ancient Gosiute Lake, but because of its 

high percentage of sulphates, which would make the 

estimate of the total dissolved solids carried in the 

ancient streams a minimum. Even by using for the 

ancient streams the improbably high percentage of 

sulphates found in the Santa Maria River, which would 

give the lowest possible concentration, the calculation 

indicates a concentration of about 4, 700 parts per million of total dissolved solids. The writer haa estimated 

by two independent methods that the average annual 

rainfall of the Gosiute Lake Basin was of the order of 30 

to 40 inches, 82 and ina.Smuch as few or perhaps none of 

the streams that fed Gosiute Lake could have been very 

long, this concentration or even one-quarter of it seems 

excessive. Because the assumption that all the material 

for each thin glauberite layer accumulated in the lake 

during the 50-year interval between times of salt deposition requires an improbable concentration of dissolved 

solids in the feeding streams, it seems valid to regard 

this assumption as wrong and to conclude on the contrary not only that the saline constituents· had been 

accumulating for a relatively long time before the first 

glauberite began to form but also that this reserve of 

salts was being drawn upan, to some extent at least, a8 

long as layers 0.5 millimeter thick continued to form at 

intervals of 50 years. Although a part of ·the saline 

phase of the Green River formation near its type 

locality in Wyoming has been used to reach these conclusions, the saline phase in the western part of the 

Uinta Basin is so similar that in a general way conclusions reached from a study of one will apply equally 

well to the other. 

StBradley, W. H., op. cit. (Prof. Paper 158), pp. 91-03 

u Idem, pp. 91-03 
34 ORIGIN AND MICROFOSSILS OF OIL SHALE OF GREEN RIVER FORMATION 

Numerous chert concnitions 

wi'tk e!aterite (?) 

~-fl.'eg,?e!!.~ite ct;ystals 

~-,:,,~pt.oll'l.:e beds 

EXPLANATION 

~ ~ G/euber/te(i>)molds 

spersefy clistri'buted 

~ Gleuheritef.'Jmolds ~abundant 

=== 

~ 

Gleuber/te(.")mqlds 

with cycli'c arrangement· 

~ 

~ 

Molds o/'iJn unlmowQ salt 

with bladed habit 

.. Mudcrack-s 

Vertical scale 

50L-i-~-L-OL--------5~0--------J~OO--~-----L~----~2QO FEE~ 

FIGURE 3.-Columnar section of the saline phase of the Green River formation in Indian Canyon. 

Duchesne County, Utah, showing the distribution of the salt molds, mud cracks, fossils, and volcanic-ash layers ai:J.d the positions at which a few unusual minerals occur .) 
. MINERALOGY , . 35 

Hence the ancient Green River lakes may be pictured One of these b~rren units is 24;5 feet thick. If the . 

. as without outlet for long periods of time during the rate of sedimen~ation inferred from' the varves in the 

saline phasei · While the lakes occupied closed basins marlstone beds pf the Green River formation in Colothe water vplume apparently fluctuated periodically rado 85 is assun;led, namely about 2,000 years to the 

and at the etxtreme low levels precipitated some of its foot, then ~hi~ 1:· it represents a ~ttle le~ :han 50,000 

salt. However, as much of the salt or rather its molds years. If It IS· assumed that durmg this mterval the 

are found o:p. deeply mud-cracked bedding planes it streams which. fed the ancient Uinta Lake had an 

may well bei that even at the extreme low levels the average concen~ration of about 72 parts per million 

brine was not so co_ncentrated that glauberite crystal- (the a~erage c~ncentration of 17 rivers in the South • 

lized from it, but rather that as the lake shrank salt Atlantic States) 86 and that the average annual run-off 

formed only ion the mud flats as the result of excessive amttunted to a llay0r of water 2.3 inches {5.84 centievaporation.: The higher temperature of the mud meters or in :ropnd numbers 6 centimeters) deep per 

and the thi4 sheet of water at the strand line would unit area of th. lake surface and a layer of water of 

also favor t]!le formation of glauberite, for according equal depth w~ lost from the lake by evaporation, as 

to Van't Hoff 83 glauberite can be precipitated by has been estim~ted for the ancient Gosiute Lake,87 

itself from s<>lutions saturated with respect to gypsum which lay nort~ of the Uinta Mountains, then it will 

and the dec~hydrate of sodium sulphate only between be possible to t~st the hypothesis that ~t was necessary 

the temperatures of 29° and 32.4° C. (84.2° and 90.3° for the lake t~ overfl9w, for a short time at least, 

F.). Below i29° C. gypsum forms, and above 32.4° C. during this 50!000-year interval in order that the 

the anhydrous sodium sulphate thenardite crystallizes thickest barren marlstone unit in the Indian Canyon 

out. But the _presence of other common salts tends saline zone co~d have been deposited free from salt. 

to lower the temperature limit for glauberite, and V an't Assume that tlfe lake was entirely fresh . and had an 

Hoff 84 also spows that glauberite will form at temper- average depth qf about 50 ~eet (15 meters). Consider 

atures as loJ as 10° C. (50° F.) if the brine is saturated a unit column ~f the lake water 1 centimeter square 

with respect to sodium and potassium chlorides and in cross section I and 1,500 centimeters (about 50 feet) 

magnesium sulphate as well as gypsum and Glauber's deep. Each y~ar for 50,000 years the amount of 

salt. As it is likely that chlorides, as well as the bases solids dissolved! in 6 cubic eentimeters of the stream 

magnesium and potassium, were present in the waters water, whose cd;ncentration is about 72 parts per milof the· ancient Uinta and Gosiute Lakes, the actual lion, is added tp. this column of lake water; but .the 

temperatures at which the glauberite formed probably volume of the polumn remains constant, for in each 

varied with the composition of the brine and were year a layer 6 ~entimeters deep is lost from the lake 

generally less than the maximum possible temperature surface by eva~oration. The total dissolved solids in 

of 90° F. No traces of thenardite, halite, or primary 1 cubic centim~ter of the stream water amount to 

gypsum have been found directly associated with the 0.000072 gram, 1and as the annual increment of stream 

glauberite(?) impressions, and hence the composition water per unit ~~rea .is 6 cubic centimeters the annual 

of the water and the environmental conditions prob- increment of ~lids to the unit column would be· 

ably were nearly alike each time the lake reached a 0.00043 gram ~d in 50,000 years about 21.5 grams. 

stage of salt deposition. Different conditions are indi- This amount of! material dissolved in the unit column 

cated by only six thin beds in the saline phase of the would give the [water a concentration of a little more 

Green River formation in the western part of the than 1,400 par~s per million, which is far· below that 

ltJinta Basin, where the_ saline zone is a little more necessary to pr~cipitate out salts like glauberite. If 

~han 800 feet thick. These beds indicating different the lake instead of being nearly full at the beginning 

onditions contain abundant molds of an unknown of this interval ~ad been quite low, as it probably was 

laty mineral, which is presumably, however, an alkali just after salt djeposition, and.had expanded consideralt. ably during th~ deposition of the marlstone unit that 

1 Although for very long periods during the saline contains no sal~ ~olds, it seems likely that the resulting 

phase the lake had no outlet, there were also intervals concentration 91 the lake water would have been of 

of considerable length in which the ooncentration of about the sam~ order of magnitude, despite the fact 

dissolved material was diminished and the lake may that the small vplume of water in the lake at the begineven have been freshened by occ~sional overflow. ning of this. !' 'terval would probably have been a 

Several of these intervals are indicated in the saline strong brine. · rom these considerations it is perhaps 

phas.e in the western part of the Uinta Basin by units conceivable th t even during the deposition of the 

of shaly marlstone that contain remains of ganoid thickest marlst ne unit without salt molds Uinta Lake 

fish but no traces of salt and relatively few mud cracks. 

sa Van't Ho:ff,J. H., Untersuchungen fiber die Bildungs-verh!Utnisse der ozean· 

ischen Salzablagerungen: K. Akad. Wiss. B~Hn Sitzungsber., 1906, pp. 478-479. 

u Idem, pp. 482-483. · 

36544--31-4 

81 Bradley, W. H., oE' cit. (Prof. Paper 158), p. 99. 

ee Clarke, F. W ., The •. position of the ri.ver and lake waters of the United States: 

U. 8. Geol. Survey Pro . Paper 135, p. 48, 1924. . 

87 BradleY., W. H., o cit., pp. 9HI3. 

I . 

I I· 

I 
36 ORIGIN AND MICROFOSSILS OF. OIL SHALE OF GREEN RIVER FORMATION 

was not partly freshened by overflow. However, it 

is about equally justifiable to assume that the lake did 

~overflow, for if, as seems wholly possible, the streams 

carried a greater quantity of dissolved solids, if the 

average depth of the lake even when full was less than 

about 50 feet, and if there was a considerable quantity 

of strong brine left at the beginning of the interval 

when the thickest barren unit was deposited, then as 

no salt was deposited it would be necessary to conclude 

that some of the dissolved solids had discharged. from 

the lake by overflow. The presence of remains of 

ganoid fish in these barren units favors the hypothesis 

that the water was freshened. 

A. quite different interpretation might be placed 

upon some of the thinner barren units-namely, that 

they represent areas of the lake bottom which by 

reason of slight local warping were covered by deeper 

water from which no salt crystallized. According to 

this interpretation salt may have formed at the strand 

line in other parts of the lake basin and so maintained 

the balance between supply and precipitation. 

The section of the Green River formation measured 

near the Duchesne-Uinta4 cmmty line a few miles west 

of Desolation Canyon, Utah, contains no saline faciesa lack which appears to be significant in accounting 

for the utter dissimilarity between the saline zone of 

the Indian Canyon section and the saline zones east 

of Desolation Canyon. Approximately the lower half 

of the formation near the Duchesne-Uintah county 

line consists of a sandy facies which the writer regards 

as a sublacustrine deltaic deposit. This interpretation of the lower part of the formation and the absence 

of salt in the upper part suggest that a relatively large 

supply of fresh water continued to come into this part 

of the lake for most of the rest Jlf Green River time. 

· Detrital material brought in by the stream that furnished this water would tend ultimately to build up 

t:t low ridge that in times of low water would isolate 

the west end of the Uinta Basin. Nevertheless, the 

greater relative compaction of the predominantly 

shaly formation on each side of the less compactible 

sandy deltaic facies was probably a more effective 

factor in creating a north-south divide across this 

part of the Uinta Basin. According to this interpretation the saline phases in the western part of the Uinta 

Basin may have formed independently of those in the 

eastern part and in the Piceance Creek Basin. This 

would explain the lack of similarity in mineral composition and in ·general aspect between the two groups 

of saline phases. 

The saline phases in the eastern part of the Uinta 

Basin and in the Piceance Creek Basin are less well 

defined and can not yet be correlated with one another. 

(See pl. 3.) The salt in these phases formed as radial 

aggregates and in layers much less closely spaced than 

the layers that contain glauberite (?) molds. Ellipsoidal cavities whose major axes ra.nge from a fraction 

of an inch to more·than 5 feet in length now represent 

these radial aggregates of the saline mineral. 

A few cavities from the beds alorig .the ·lower part 

of Piceance Creek contain cellular calcite fillings which 

preserve as molds the long bladelike salt crystals. 

(See pl. 6, A.) Unfortunately the crystals were so 

complexly intergrown that they can not now be 

identified .. 

A general climatic change involving a diminution of 

the average annual rainfall or perhaps increased 

evaporation due to changes ill the seasonal distribution 

·of the rainfall was probably the principal factor controlling the ·shrinkage of the ancient Uinta Lake and 

consequently the precipitation of salt. Using as a 

measure the thickness of the saline· facies· in Indian 

Canyon, Utah, about 800 feet, and assuming again 

that the average rate of accumulation of the rocks in 

this facies is 1 foot in about 2,000 years makes the 

length of this interval of reduced precipitation or 

increa8ed evaporation of the order of .1,500,000 years. 

This is about one-fourth of the totallength·of the Green 

River epoch according to an estimate based upon the 

varves in the Green River formation in the vicinity 

of Parachute Creek, Colo.88 

The absence of salt and the differences in lithology in 

that part of the formation above the saline facies 

seem to indicate a. reversion· to a somewhat moister 

climate or a reduction of the evaporation rate, perhaps 

more nearly comparable to that which prevailed during 

the earlier stages of Uinta Lake. The absence of salt 

from these uppermost beds might also be accounted for 

by either of two alternative hypotheses. If the outlet 

were cut down so that the area of the lake was materially diminished, the total loss by evaporation from the 

lake and its drainage area would be diminished, because 

in general the rate of evaporation from a free water 

surface is greater than from the land and plants. Thus 

if the outlet were cut down and the climate remained 

constant the run-off from the drainage basin might be 

sufficient to cause intermittent discharge from the lake 

and.so prevent salt deposition. Accession of additional 

drainage area by stream capture would bring about the 

same condition of discharge from the lake, even if both 

the climate and the altitude of the outlet remained 

unchanged. 

SECONDARY MINERALS 

Apparently few changes have occurred in the :mi.nerals of the oil shale since the compaction _and lithification 

· of the original ooze. Very small quantities of chalcedony were found In some oil-shale beds, aD:d secondary 

calcite is hardly more plentiful. The secondary calcite 

occurs as large irregular crystals or as minute spherulites with perfect radial structure. 

8s Bradley, W. H., op. cit. (Prof. Paper 158), p. 107. 
MICROFOSSILS 37 

CONCRETIONS· 

Calcite concretions.-Concretions of microgrft.nular 

calcite are exceedingly abundant in some oil~shale 

beds and occur at least in small numbers in nearly 

all the oil-shale beds of the Green. River formation. 

They are ellipsoidal· and range in length from 0.25 

millimeter to about 2 centimeters. The minor axes . 

average about one-fourth of the major axes. · (See 

pl. 17, A.) 

As the beds that are rich in organic matter are 

so extremely fine grained and compact, it seems very 

doubtful if solutions could have moved freely enough 

in them after lithification to produce these calcite 

concretions. On the contrary, it seems rather probable 

that the concretions were formed while the ooze was 

still soft and plastic. Nevertheless, as they have 

crowded the laminae away from them both above and 

below, the ooze must have been a stiff enough gel 

to ;retain its original laminate structure. The carbonate grains in the smaller of these concretions 

average about 0.001 millimeter in diameter. This 

small size suggests that the minute mineral particles 

migrated and so a~sembled under the impulsion of 

the same forces that control the agglomeration of 

any extremely fine particles. Thus the fine mineral 

grains, although larger than colloidal particles, may 

be considered analogous to the dispersed phase of 

a colloid, and the organic matter may be regarded 

as the dispersion medium. An active . coagulating 

agent might then have assembled many of these 

p~rticles, the larger aggregates growing at the expense 

of the smaller ones, which by reason of: their greater 

convexity would haye been unstable in the presence 

of the larger aggregates. 

Chert concretions.-Concretions of chalcedonic quartz 

are not particularly common but were found in several · 

oil-shale beds, some of which are of rather low grade. 

These concretions like those of_ calcite, are roughly 

ellipsoidal. They range in length from about 5 millimeters to 5 centimeters. These concretions also displace the laminae of the oil shale, but they must 

have formed immediately upon the burial of the 

sediments, for they contain beautifully preserved 

organic structures, fern sporangia and spores, various 

pollens, algae, and fragments of the tissues of higher 

plants._ (See pl. 23, figs. 5, 8, 10, 12.) -Apparently 

these organisms together with other organic matter 

were suspended in a mixture of organic -and . silica 

~els. The .. parts of organisms were thus perfectly 

embalmed, though their original composition has 

doubtless .been altered. Yet in that alteration and 

despite the· crystallization of the silica the organisms 

were not at all crushed, distorted, or cracked by 

. shrinkage. 

These chert . concretions are unusual in another 

feature. Each contains a peripheral layer of pyrite, 

which -1s m cubes, ·octahedra,. aeimdar ccystals, and 

minute spheroidal graitis. The pyrite- also must 

have been suspended in the mixture of organic . and 

silica gels, as is shown by its- excellent crystal- form 

8.nd with particularly convincing force by the hundles 

of acicular crystals. No satisfactory explanation can 

yet be offered to account for the ~gregation of the 

pyrite in peripheral zones of the concretions. . . MICROFOSSILS 

Microorganis s, including algae,: fungi, Protozoa, 

and bacteria_, f om oil shales and bogheads in many 

parts of the w rid have been described. The writer 

believes that t e first to recognize ·.,nd describe t;~uch 

fossil gelosic al ae were Bertrand and Re~ault,89 who 

as long ago as 892 pointed out that the boghead of 

Autun,_ France consisted chiefly of the thalli of a 

simple colonial alga, to which they gave the name 

Pila bibractens ·s. This work was followed by a 

noteworthy seri s of publications by the same authors.90 

The most rem rkable of these paperS are the two 

large systemati works, one by Renault (1899, 1900) 

and the other b Bertrand (1898). 

Potonie's rep rt 91 on his study of the recent sapropelsororganico zesappearedin1908. · Itisparticularly 

valuable for th light it sheds upon the conditions governing the accu ulation of sapropel. and the stages of 

putrefaction w.qich the material passes through~ 

Zalessky 92 h~s commented on the genus Pii!L and 

the sapropel of ~ake Balkash, which consists chiefly of 

Botryococcus brqunii. In later papers 93 he described 

some ·very ancil nt blue-green algae in the Esthonian 

boghead ari.d other· species of Pila· in a deposit 

near Tcherem ova, Russia. 

Davis,94 in a reliminary paper, reported finding wellpreserved blue- een and green algae and unclassified 

algae in the oil shale of the Green River formation. 

Of the blue-gre n algae he mentioned specifically one 

which he regar ed as Spirulina sp. His photograph 

of this organis is reproduced in Plate l9, Figure 10, 

and the writer' description, together with some comao Bertrand, C. E., d Renault, B., Pila bibractemfB et le boghead d'Autun: 

Soc. hist. nat. Autun B 11., vol. 6, pp. 159-253, 1892. 

Do Renault, B., &ins ia amtraZia et premieres reDlallques sur le keroaene shale 

de la Nouvelle-Galles d Sud: Soc. hist nat. Autun Bull., vol. 6, pp. 321-425, 1893; 

Sur quelques microorg 'sme8 des combustibles fossiles: Soc. ind. min. St.-Etienne 

Bull., 3d ser., vol. 13, p. 865-1169, 1899; vol. 14, pp. l!-159, 6i .figs., 30 pis., 1900. 

Bertrand, C. E., Nouv lles remarques sur le kerosene !!hale de la Nouvelle-Galles 

du Sud: Soc. hist. nat. tun Bull., vol. 9, pp. 193-292, 1896; Les charbons humiques 

et Ies charbons de purin : Univ. Lille Trav. et m6m., vol. 6, M6m. 21, 214 pp.; 1898. 

• 91 Potoni(;, H., Die re nten Kaustobiolithe und ihre L~gerstlitten: K. preuss. geol 

Landesanstalt Abh., ne ser., Heft 55, Band 1, pp. 3-36,:59-238,1908. 

02 Zalessky, M.D., 0 the nature of Pila or the yellow bodies of boghee.d and on· 

sapropel of the Ala-K Gulf of the Lake Balkash: Com. gOO!. Bull., vol. 33, pp. 

495-507, Petrograd,l914. 

93 Zalessky, M.D., S lesaprop6lite del' Age silurien form6 par nne algue cyanophycoo: Soc. paloont. ussie Annuaire, vol; 1, pp. 25-42, 1916; Sur quelques 

saprop6lites fossiles: S • gool. France Bull., 4th ser., .vol. 17, pp. 373-379, 1917. 

u Davis, C. A., On t e fossil algae of the petroleum-yielding shales of the Green 

River formation of Col ado and Utah: Nat. A cad. Sci. Proc., vol. 2, pp. 114-lU»,. 

1916. 
38 ORIGIN AND MICROFOSSILS OF OIL SHALE OF GREEN ~R FOR¥A.'.fiON 

ments, is. given on page 42. Davis also mentioned a 

gree!l alga which he thought should be referred to 

Pediastrum or a closely related genus. His photograph 

of this is reproduced as Plate 21, Figure 5, of this 

report, and the writer's description and reasons for 

transferring to another genus are given on page 43. 

In addition to these algae he referred to another green 

alga which had spiral chloroplasts and which he 

• regarde~ as either a prototype of Spirogyra or perhaps 

even a species of that genus. . Unfortunately no phqto:-

graph of this remarkable fossil was found among Davis's 

photomicrographs, and the writer has never discovered 

anything comparable to it in his own thin sections or 

those made by Davis. So far as the writer is aware 

Davis's mention i-s the only record of chloroplasts in 

fossil aigae from the Green River formation. 

Some brief notes made by Davis were published in 

Winchester's latest bulletin on oil shale.95 They are 

reproduced here, as they are particularly pertinent to 

this study. 

Flora of the oil shale of the Green River formation 

[Notes by C. A. Davis, March 30, 1915] 

Bacteria: Crenothrix and similar low filamentous types. 

Myxophyceae: Blue-green algae. · 

Algae: 

Protococcaceae: . Protococcus pediastrum. 

Conjugate: Spirogyra. 

Fungi: Saprophytic molds, etc. 

Mosses: Spores probably from these plants. 

Pteridophyta: Ferns; annuli from fern sporangia. 

Spermatophyta: 

Gymnospermae: Pinaceae: Pollen of Picea and Pinus. 

Angiospermae: Pollen and fragments of cells, tissues, etc. 

Bark cells and residues, small pieces, poorly preserved. 

In addition there are abundant and well-preserved remains of good size and of frequent occurrence; which seem 

to be structureless so far as· cellular structures are concerned. However, they have definite and pretty regular 

forms and, in Dictyonophora, definite areas which carry 

well-marked and characteristic patterns which seem like 

cells -but which show no cell walls. These ano~alous 

forms seem to have been the most abundant organisms 

in the w.aters in which the shales were laid down and are 

evidently vegetables of a low order of development. 

They are manifestly in place as they grew, for they do 

not show in pressed-down masses but were buried in 

natural positions, very slowly. 

White and Stadnichenko,96 in a recently published 

paper, describe some fucoid algae and spore exines and 

their chemical compositions. 

The writer 97 in 1924 described a new species of 

Epipolaia. The genotype of this alga was described· 

by Bertrand 98 and came from the Brow.n oil shale of' 

Broxburn, Scotland. 

96 Winchester, D. E., Oil shale of the Rocky Mountain region: U.S. Geol. Survey 

Bull. 729, p. 32, 1923. 

U& White, David, and Stadnichenko, Taisia, Some mother plants of petroleum 

n the Devonian black shales: Econ. Geology, vol. 18, pp. 238-252, 1923. 

t7'Bradley, w. H., An oil shale and its microorganisms from the Fuson formation 

of Wyoming: Am. Jour. Sci., 5th ser;, vol. 8, pp. 228-234, 1924. 

ta Bertrand, C. E., Les charbons humiques et les charbons de purins: Univ. Lille 

Trans. et mem., vol. 6, Mem. 21, pp. 179-181, 1898. 

Thiessen'~ study of eoorqngi~ 99 demonstrated in a 

most satisfactOry manner the. algal origin of boghead 

coals. Coorongite consists of the gummified. thalli of 

a modern alga whose systematic position is unknown 

but which he called Elaeopkyton coororigiana. These 

planktonic algae live in salt lakes and lagoons in South 

Australia. During the summer the lakes dry up· and 

the accumulations· of algae quickly dry into sheets of 

rubber-lik~ dark-b1own material. The similarity, 

even in the minutest details, of Elaeopkyton to the fossil 

colonial algae in many bogheads is most convincing. 

White 1 has recently given a comprehensive and 

concise summary of. the work- which has thus far been 

done on the. sapropelic deposits. This summary he 

enriches with information· from his own studies. He 

treats in particular the oil shale of the Green River 

formation and presents his conclusions regarding its 

origin together with some of the evidence upon which 

they are based. 

The writer in a recent paper 2 gave the descriptions 

of four of the algae described herein {pl. 21, figs. 3, 6, 

7; pl. 22, fig. 1), together with a· brief discussion of 

factors that have probably contributed to their excellent preservation. This paper was writtf.-11 in response 

to Potonie's recently published assertion 3 that the so.;. 

called fossil algae from certain boghead coals and oil 

shales were never organisms but instead structures 

resulting from the coagulation of certain qolloidal 

constituents of the original organic ooze. In order to 

get some of these fossils before botanists·. eight of 

the algae described in this· report (pl. 19, figs. 7, 8; 

pl. 21, figs. 1, 3, 5, 6, 7; pl. 22, fig. 1) were described in 

another recent paper 4 together with some brief notes 

on the manner of their preservation. 

PREPARATION OF THIN' SECTIONS 

Many thin sections of the oil shale were· ground in 

the ordinary manner in the petrographic laboratory 

of the Geological Survey. However, heat was avoided 

as much as possible, and to this end the sections were 

mounted in a mixture of canada balsam and xylot 

This mixture was thin enough to :flow readily at room 

temperature. Small weights supported on cork disks 

were placed upon the cover glasses for several days, as 

otherwise the sections would have been badly wrinkled 

after a few months. Moreover, in most unpressed 

sections the distance between the section and the 

upper surface of the cover glass is so great that an· 

immersion objective can not be used. A few grades 

u Thiessen, Reinhardt, Origin of the bogltead coals: u. B. Geol. Survey Prof. 

Paper 132, pp. 126-135, 1925. 

1 White, David, The carbonaceous sediments, in Twenhofel, W. H., Treatise on 

sedimentation, pp. 289-304, 1926. 

• Bradley, W. H., ·Neue Beobachtung iiber Algen a1s Urma.terialen der Bogheadkohlen und Schiefer: Centralbl. Mineralogie, Abt. B, No.5, pp. 182-190, 1928. 

a Potoni~, R., Einfifurung ·in die allgemeine Kohlenpetrographie, pp. 131-140. 

Berlin, 1924. Potoni~, R., and Hellmars, H., Zur Entstehung der Gerrlnunp]dirper 

(der sogenannten Algen) der Bogheadkohlen und Schiefer: Preuss. geol. Lim~· 

stalt Jahrb., vol. 48, pp. 152-157, 1926. 

• Bradley, W. H., Fresh-water algae from the Green River formation of Colorado! 

Torrey Bot. Club Bull~, vol. 56, pp, 421-428, 1929. 
APPEARA.NCB .·OF! OBG.ANIC MA'rl'ER IN THIN SECTIONS I·_ 39·' 

<>f oil shale may • be so rich that it i8 ad'risable to 

avoid even the. heat necessary to cement the chip 

to the glass slide~ These may be cemented with and 

mounted in sodium ·silicate, which, however; . is an 

unsatisfactory mounting medium because it does not 

clear the specimen enough, because bubbles are almost 

sure to develop; and because after a few' years i• 

eeystallizes. · 

Oil shale, especially the richer grades; can be softened 

and cut in .a microtome. Theae sections are very 

satisfactory, particularly for study of the microorganisms and pollens, because all the mineral g~ains that 

transmit and diffuse the light have been removed. In 

prepari.D.g the oil shale for microtome sectioning the 

writer has followed essentially the method outlined by 

Jeffrey 6 except that the ·treated shale is embedded in 

paraffin instead of celloidin. The use of paraffin not 

only eliminates the long, tedious process of the celloidin embedding but also makes. it· possible with a 

rotary microtome to cut good ribbons of sections as 

thin. as 6 microns (0.006 millimeter). 

. So far as the writer is aware C. A. Davis left no notes 

describing his t~chnique of preparing microtome 

sections. However, on some small specimen bottles · 

in which he treat'ed the shale are a few fragmentary 

notations from which it is clear that he used dilute 

nitric acid, potassium. hydroxide, pyridine, phenol, 

and .chloral hydrate as softening agents and hydrofluoric acid to remove the mineral matter. What the 

order of procedure was is unknown. He used paraffin 

as an embedding medium. 

The writer's method of treatment is outlined here 

briefly. The fresh shale is cut with a hack saw into 

rectangular blocks 5 or 6 millimeters square and 3 or 

4 millimeters thick, so oriented that the square surfaces are parallel to the bedding. These pieces are 

treated with equal parts of hydrofluoric acid 8illd dih1te 

nitric acid (1-1) at room temperature for about a 

week, or longer if the shale is obviously rich in pyrite. 

The ex~ess acids are washed out with running water, 

and the shale is· then soaked for several days in a very 

dilute sodium hydroxide solution to neutralize the 

acid remaining in the specimens. H any of the nitric 

·acid remains the shale will be dissolved rapidly in the 

hot phenol. After thorough rinsing the shale blocks 

are then immersed in melted phenol, where they are 

· kept at about 70° C. until soft enough to be penetrated 

easily with a fine needle. The time required for this 

softening varies greatly, but roughly it bears an inverse 

ratio to the richness of the shale. The time necessary 

to soften various sorts of shale from the Green River 

formation ranged from three days to as many months. 

All kinds swell more or less in the softening process, 

and some warp and crack badly. From the phenol the 

shale is transferred to hot water, in which it retnains for 

•1effrey, E. C., Methods of studying coal: Science Conspectus, vol 6, pp. 71-76, 

1916. . 

·several days. 'The hot water· ,must, of oourse; ·be 

changed frequently. When . entirely free '.of pheb.dl' 

the· shale is ·dehydrated in stroD.g alcohol and firiadlY 

with three changes ·of absolute ·alcohol. F:tO:rn the· 

absolute alcohol it is transferred to a mixture of, equal 

parts of Xy-1~1 and ·abs<>lute alcohol. After about one 

hour in the xylol and. alcohol it can be transferred to 

warm paraffin dissolved in xylol, and from ·that into 

pure melted paraffin, in which it should soak for at 

least 24 hours, b,ut to leave it 48 hours is safer.. The 

oil shale can then be cut with a sliding or rotary microtome. Serial sections so cut are valuable for making 

counts of. the microorganisms or pollens and spores. 

Although some shale can be. cut as thin as· 5 microns, . 

there is no advantage in such thin sections. Ordinarily 

sections 12 to 15 microns thick are satisfactory~ The 

material is so translucent that. sections as much as 

150 microns thick can be studied easily under the· 

microscope. These very thick sections are necessary 

to get complete individuals of the larger microfossils, 

such as some of the insects. The microtome sections 

are mounted i:D. a mixture of Canada balsam and xylol, 

and the cover glasses are weightedlm the same way as 

for the ground sections. 

APPEARANCE OF ORGANIC MATTER IN THIN SECTIONS 

• • • I 

Two kinds of organic matter can be clearly dis .. 

tinguished in thin sections of oil shale. One is entirely 

structureless, translucent, and lemon-yellow to reddish· 

brown. It makes up the groundmass of the shale. and 

contains various quantities of finely divided n;rineral 

matter, which in many shales is segregated m more or 

less well-defined laminae. The. other kind of organic 

matter consists of complete or fragmentary organisms 

such as algae, Protozoa, and insects and parls of higher 

plants-spores, pollen grains, or minute pieces of tissue. 

For the sake of brevity all this material that has definite· 

form will here be designated "figured,material" In 

this sense "figured" implies nothing in the way. of. 

illustrations. All the figured material is emb~ded in. 

the structureless component and in addition to having 

definite form may even show internal structure. (See 

pl. 18.) 

St~ctureless material exceeds the figured material 

in all thin sections of· oil shale from the Green River 

formation which the writer has exammed. Hence the 

mi~roscopic aspect of this shale is very unlike. ihat of 

pure alga bogheads-for example, the kerosene shale of 

New South Wales, which consists almost exclusively .of 

well-preserved colonial algae. Nevertheless all thin 

sections of rich Green River oil shale contain some 

figured material, and a few contain considerable 

quantities. Relatively little of the figured materi&l 

is well enough preserted to be identified and described, 

but in certain beds microfossils are fairly ·common. 

This fact explains why ~ many of the microorg~ms. 

described below came from only a few localities. 

.. A 

,•

~ 
40 ORIGIN AN]) MICROFOSSILS OF OIL' SHALE O]f GREEN RIVER FORMATION 

.The e~tire area of each thin section containing 

microfossils was searched systematically at a magnification of about 250 diameters. Objects to be studied 

more critically were located and recorded by means of 

the coordinates of the mechanical stag~. 

The writer tried several stains on the. microtome 

sections but was. wholly unsuccessful. The organic 

matter is evidently too inert and dense to react to them. 

. FLORA OF THE OIL SHALE 

BACTERIA 

. ·' , . . Plate 19, Figures 1, 4 

· P,avis 6 .:repQr~ed Orenothrix, but none of his photomicrographs show filaments with internal structure 

definite enough to convince the writer that they should 

be referred to that genus. Yet several thin sections 

show an abundance of minute filaments 1 to 5 microns 

in diameter which are probably trichobacteria. (See· 

pl. 19, fig. 4.) None of them show vegetative cells or 

gonidia, however, and so they can not be surely 

distinguished from some of the simplest Cyanophyceae, 

whose structure is nearly identical. Their unusual 

length and abundance favor the assumption that they 

are bacteria which lived within. the organic ooze rather 

than algae, for most of the algae in the oil shale are 

fragment~ry. . • 

A few bacilli (?)occur in the richest beds, but they are 

so rare that it does not seem worth while to name them. 

The largest one shown near the center -of figure 1, 

Plate 19, is about 1 micron in diameter and 20 microns 

long. It is constricted near one end, _just b~low a 

beadlike termination. This cell resembles somewhat 

the large cells of Bacillus subtilis, some of which are 1 

micron in diameter and as much as 17 microns long.7 

Locality: Both the filamentous bacteria(?) and the 

~acilli (?) occur in a sample collected by E. G. Woodruff . 

from Asphalt Tunnel, about 2,300 feet above the base 

of the formation, in sec. 1, T. 7 S., ·R. 98 W., Garfield 

County, Colo. . 

Cocoid bacteria have not been found in the oil 

shale of the Green River formation. This seems 

rather strange, for they are exceedingly abundant in 

the Miocene oil shale from Elko, Nev., and the writer 8 

showed that they were plentiful in the oil shale of the 

Fuson formation. In neither of these oil shales is the 

organic matter so much disintegrated by microbiStn 

decomposition as that in the Green River oil shale. 

FUNGI 

Spores of fungi are more or less plentiful in 

mos.t thin sections -of the oil shale. Conidia and 

o Davis, C. A., notes cited by Winchester, D. E., Oil shale of the Rocky Mountain 

region: U.S. Geol. Survey Bull. 729, p. 32, 1923. • 

7'Lohnis, F., Studies upon the life cycles of the bacteria: Nat. Acad. Sci. Mem., 

vol. 16, pl. 23, 1921. 8 Bradley, W. B:., An oil shale and its microorganisms from the Fuson formation 

of Wyomfug: Am. Jour. Sci., 5th ser., vol. 8, p. 242, fig. 4, 1924. 

fragments .of hyphae were: .also ·found,· and locally·· 

they are numerous. ; The follo-wing ,notes, on the fungi 

spores are .based very largely on suggestions rltade .by· 

Dr. C. L. Shear, 9 of the Bureau ·of 'Plant Industry. 

Plate 19, Figure 2.-The rigid epispore, together. 

with its fusiform shape and symmetrical septation,·. 

lltrongly suggests that this ·is a spore belonging to~ 

Leptosphaeria or a closely related genus. . Species of· 

Leptosphaeria- are common parasites, have a · wid.e 

geographic distribution,· and thrive in .all climates.· 

Plate 19, Figure 3.__.:.The general form and apparent 

hyaline terminal compartments, coupled with the 

thick epispore and thicker septa, suggest t~at this is 

probably a spore of a species of Pestalozzia with the 

filiform terminal appendages lacking. 

Plate 19, Figure 5.-Apparently there are two elon-, 

gate multiseptate spores .here. These resemble the 

spores of the hyphomycete Septonema. 

Plate 19, Figure 6.-This group of spores may repre-. 

sent an ascospore group, although there are apparently· 

only seven spores.. More probably, however, it is a 

chain o~ conidia similar to those of the genus Bispora. 

Plate 20, Figure 1.-If thes~ are ponidia they may 

belong to a genus like Trichothecium; if they are . 

· ascospores they may belong to a genus like Mycosphaerella or Didymella, many species of which have 

similar unequally divided spores. 

Plate 20, Figure 2.-This is evidently a chain of 

conidia similar to those produced in various genera of 

Hyphomycetes, such as Aspergillus and Haplographium. 

Plate 20, Figure 3.-This sm~ll spore suggests the 

spores of Helminthosporium sp. 

Plate 20, Figure 4.-This is probably a germinating. 

spore. It suggests Hendersonia sp. 

Plate 20, Figure 5.-These appear to be chains of 

conidia and may belong to a genus like Torula. 

Plate 20, Figure 6.-This group suggests a hyphomycete with sporophores and detached uniseptate conidia. 

It somewhat resembles Cladosporium sp. 

Plate 20, Figure 7.-These thick-walled. spores resemble rather closely those of Macrosporium sp. · 

Plate 20, Figure 8.-This resembles a rust sorus and 

suggests the sorus of Uromyces sp. with spores. 

·Plate 20, Figure 9.-This slightly broken form is 

very similar to the conidia of Brachysporium sp. 

ALGAE 

The ·algae found in the oil shale are all microscopic, and although their outlines are remarkably 

well preserved their internal structural features, . 

such as chloroplasts, nuclei, vacuoles, and pyrenoids, 

have disappeared except possibly in a fragment ·of 

Spirogyra in which Davis reported having found the 

chloroplasts. Other features have likewise disappeared, 

g Personal communication, March, 1927. 

II 
FLORA OF THE OIL SHALE 41, 

such as the gelatinous sheaths that very likely inclosed 

so1ne of the Cyanophyceae. Moreover, in none of 

the fossil algae has the writer been able to establish 

to his own satisfaction the mode of reproduction, 

despite the statement of Davis 10 that "many of them 

show a series of reproductive stages so characteristic 

as to fully establish their taxonomic relationships.'' 

Of course, their color has not been preserved, and 

therefore the writer's assignments to genera of living 

algae· are based wholly on their external forms. Yet 

these are all simple and distinctive forms, and for 

that reason the writer feels that these assignments 

are probably not greatly at variance with the truth. 

SOme of the algae are too uncertain to warrant assignment to even a tentative position in the natural 

system, but the similarity of some of these two living 

forms is pointed· out. A few, on the other hand, 

are unique so far as the writer has been able to determine. One of the most unusual of- these, Eoglobella 

longipes,. is described in this report. 

Class FLAGELLATA 

Order EUGLEBIDA 

Pamil7 EUGLININEAB 

Genus PHACUS Dujardbi 

Ph.acus sp. ct. P. caud.ata H11bner 

Plate 19, Fiaure 7 

Phacm sp. cf. P. caudata H iibner. Bradley, 'rorrey Bot. Club 

Bull., vol. 56, pp. 423-424, 1929. 

This pyriform cell is-remarkably like certain species 

of the euglenoid genus Phacus. In the short, straight 

caudal spine, the asymmetry of the forward end, 

and the dimensions it · is very close to P. caudata 

Hubner, which, according to Pascher,11 is 2.5 microns 

wide. and . 45 microns long. The fossil is about 25 

microns wide and 46 microns long. However, no 

longitudinal striae and no longitudinal fold are discernible, though these characters may have been 

obscured dur-ing compaction and lithification of the 

organic ooze in which the organism was embedded. 

The fossil is also very nearly like Lepocincles teres 

Schmitz, especially in the shape and length of the 

spine, but this living species is symmetrical. Pascher 12 

gives 'the dimensions of L. teres as 41 microns long 

and 17 microns across. This fossil is remarkable in 

that it apparently represents the preservation of a 

naked protoplast. In commenting upon this unusual 

fossil Professor Smith 13 called the writer's attention 

to a central light dot in just the position of the pyrenoid 

of Phacus. Examination under polarized light shows 

that this dot. is due to the presence of a minute 

mineral grain which only by chance happens to occupy 

the position of the pyrenoid. 

10 Davis, C. A., On the fossil algae of the petroleum-yielding shales of the Green 

River formation of Colorado and Utah: Nat. Acad. Sci. Proc., vol. 2, p. 116, 1916. 

u Pascher, A., Die Siisswasserfl.ora Deutschlands, Osterreic.hs und der Schweiz, 

Heft 2, p. 138, 1913. 

12 Idem, p. 13.5. 

1a Smith, G. M. (Stanford University), personal communication. 

C1ua OYANOPliYOBAE 

Order CDOOCOCOALIS 

F~yCBBOOCOCCACEAI 

Genua CDOOCOCCUS llipli 

ChrOOOOoous? sp. ct. c. westll (W. West) P. Boye 

Plate 19, Figure 8 

Chroococcus sp. cf. C. westii (W. West) P. Boye. Bradley, 

Torrey Bot. Club Bull., vol. 56, pp. 422-423, 1929. 

Each specimen of this fossil alga consists of a pair 

of broadly ovate semicells that range from 12 to 18.5 

microns in diameter. The cell walls are thick and 

homogeneous. Sheaths are apparently absent, though 

originally they may have been present and have merely 

contracted and merged with the cell wall, thus making 

it appear somewhat thicker. In shape and size these 

cells agree very well with the living 0. westii. According to Pascher 14 the cells of 0. westii, without the 

sheaths, range from 13 to 27 microns in diameter. 

The microflora of the Green River oil shale contains 

more individuals of this species than of any other. 

The writer calculated that in the sample of .oil shale 

in which the specimen illustrated was found there are 

about 5,700 individuals to the cubic centimeter. This 

calculation depends upon the assumption that the 

fossils are as numerous in other parts of the shale as 

that from which the thin sections were cut and is 

obviously subject to a very large possible error, but. 

the result is probably of the right order of magnitude. 

Volumetrically these algae are negligible, but their . 

numbers indicate in a rough way the comp.osition and 

aspect of the microflora. 

Occurrence: The specimen illustrated was found in 

a sample of pyritiferous oil shale that yielded 44 gallons 

of oil to the ton. The sample was collected by D~ E. 

Winchester from a bed of black thin-bedded oil shale 

in the Oil Shale Mining Co.'s quarry in sec. 27, T. 

7 S., R. 100 W., Garfield County, Colo. This specie~ 

was also found in samples of oil shale from other parts 

of Garfield County (sec. 1, T. 7 S., R. 98 W.; Monarch 

Shale Oil Co.'s mine, sec. 32, T. 6 S., R. 97 W., and 

sec. 25, T. 5 S., R. 95 W.), from Rio Blanco .County, 

Colo. (sec. 25, T.1 N., R. 95 W.), and from Utah (sec. 

. 6, T. 11 S., R. 24 E.). 

Chroocooous? sp. ct. c. dlSpersus (Von Ke.tsSier) Le:m.m.erinan 

Plate 19, Figure 9 

This small group of tightly packed spherical cells is 

referred to Ohroococcus with considerable hesitation. 

Of the species ·in this genus it comes nearest to 0. 

dispersus, but its cells, which are about 6.5 microns in 

diameter, are a little larger and more tightly appressed. 

The cells of 0. dispersus without their investments are 

3 to 4 microns in diameter. The fossil might almost 

as well be referred to Microcystis, as in habit and cell 

size it is comparable with M. flos"!"aquae (Wittrock) 

Kirchner. 

u Pascber, A., op. cit., Heft 12, p. 78, tl.g. 70, 1925. 
42 ORIGIN AND MICROFOSSILS· OF OIL· SHALE OF GREEN RIVER -FORMATION 

OccUITence: The specimen illustrated was found in 

a sample collected by E. G. Woodruff from Asphalt 

Tunnel, about 2,300 feet above the base of the formation, in sec. 1, T. 7 S., R. 98 W., Garfield County, Colo. 

These algae also occur in small nodules of black 

pyritiferous chert from a bed of hard carbonaceous 

ostracode shale about 140 feet above the base of the 

formation in sec. 22, T. 11 S., R. 10 E., Duchesne 

County, Utah. 

Order HORKOGOHIAE 

Family OSCU.LATOBIACEAE 

Genus CIUHALIUM: Crow 

CrlnaJ.1um.? sp. 

Plate 19, Figure 10 

Spirulina sp. Davis, Nat. Acad .. Sci. Proc., vol. 2, p. 116, 1916. 

The trichomes of this alga are a little less than 3 

microns in diameter, duplex, and jomed at the ends so 

that if untwisted they would apparently make a · 

complete ring. As they have been flattened during 

compaction of the rock it is impossible to tell whether 

they were originally circular in cross section or flat . 

and straplike. . However, they apparently are. not 

septate, though the numerous transverse shrinkage 

cracks now give that impression. The filaments form 

an ellipse about 60 microns long and 32 microns wide. 

In all these characters the fossil is remarkably like 

Spirulina duplex Wolle, but Wolle's species has not 

been generally accepted as valid. Recently Crow 15 

found an alga that agrees in many ways with Wolle's 

species but differs from it in having a sheath and in 

being U-shaped rather than closed as a complete ring. 

The fossil alga described here seems to belong rather 

to Orinalium than to Spirulina, as Davis thought. 

Occurrence: In a sample of . oil shale collected by 

E. G. Woodruff from Asphalt Tunnel, about 2,300 

feet above the base of the format~on, in sec. 1, T. 7 S., 

·R. 98 W., Garfield County, Colo. 

Genus CIUH ALlUM: Crow 

·crlnaJ.1um.? sp. ct. c. endophytlcum. crow 

Plate 21, Figure 1 

Crinalium'l sp. cf. C. endophyticum Crow. Bradley, Torrey 

Bot. Club Bull., vol. 56, p. 423, 1929. 

These strap-shaped filaments· are much like those 

of Crow's genus Orinalium. They are duplex, slightly 

twisted, and without apparent transverse septae. 

Moreover, some of them are sharply bent in the middle 

though none are really U-shaped. They differ from 

· 0. endophyticum in that they are nearly 7 microns 

broad, whereas the filaments of the living species are 

3 ·to 4 microns in diameter. Like other fossil algae of 

this microflora they have no discernible sheath, and it 

is impossible to tell if there ever 'was one. Filament~ 

like these are common in the oil shale, and all are much 

u Crow, W. B., Orinalium, a new genus of Cyanophyceae, and its bearing on the 

morphology of the group: Annals of Botany, vol. 41, No. 161, pp. 161-lM, 1927. 

broken by· shrinkage cracks. · : .Theil'; d.a.rk . ·reddish-·'. 

brown color is also a constftllt,feature an(l, Se$18 ·to 

indicate that they are rather strongly bitundnite(t· 

Occ:urrence: In a sample of. oil ·shale collected by: 

E. G. Woodruff from Asphalt Tunnel; about ~2;000 

feet above the base of the formation, in see.'l;.T. 7 8.,. 

R. 98·W., Garfield County; Colo; 

Family STIGOHIM:ATACI.U . 

Genus HAPA.LOSIPHOR Hitgeli 

Hapalosipho;n. sp. ct. H. contervaceus ~orzi 

Plate 21, Figures 2, 3 

Hapalosiphon sp. cf. H. conjervaceus Bor.zi. _ Bradley, Centr&lbl. 

Mineralogie, Abt. ·B, No. 5, pp. 184-185, 1929; Torrey 

Bot. Club Bull., vol. 56, p. 423, 1929. 

This alga is remarkably suggestive:of Qertain living. · 

·species of Hapalosiphon, yet it d~s ~ot agree exactly 

with any of them. It comes closest_ to H. conjeroace'Uit 

Borzi but differs in being slightly smaller and in. J;l.Ot 

having its filaments coated with small grains of calcium 

carbonate, as described by Pascher.16 The trichomes. 

of H. confervaceus range froin ·15 to 22 microns in 

diameter, whereas those of the fossil range fron 11 to 13 

microns. Moreover, no sheath is discernible in the 

fossil alga,· and whether it ever had one is impossible 

to tell. The fossil also resembles H. aureus W. and 

G. S. West, but it is more richly branched, and the 

branches are of a·bout the same size as the. principal 

filament rather than smaller. H. flexuosus Borzi has 

all the cha.T8.Cters of 'the 'fossil but is considerably 

smaller. Its trichomes average 6 to 8 microns in· 

diameter. 

Occurrence: In a sample of oil shale collected by 

E. G. Woodruff from Asphalt Tunnel, about 2,300 feet 

above the base of the forma.tion, in sec. 1. T. 7 S., R. 

98 W., Garfield County, Colo. 

Class CHLOROPHYCEAE 

Order PROTOCOCCALES 

Family PROTOCOCCACEA.E 

Genus cf. IREMOSPHAIRA sp. De Bary 

Plate 21, Figure 4 

These large spherical unicellular algae seem to be 

members of the Protococcaceae, but as their chromato-. 

phores, pyrenoids, and mode of reproduction are 

unknown they can not be placed in any existing genus. 

Eremosphaera viridis De Bary is the only living member 

of this family comparable in cell size with ·these fossils. 

According to Pascher 17 G. T. Moore's variety minor 

has cells that range from 30 to 50 microns in diameter. 

The fossil cells range from about 39 to about 65 PlicrQns 

in diameter. Moreover, the cell walls of the fossils are 

thin and smooth, like those of E. viridis. Bc;trydiopsis 

Borzi is another member of this family whose cell 

shape is like that of the fossil, but even the largest 

IS Pascber, A., op. cit·., Heft 1~, p. 201, 1925. 

lf Idem, Heft 5, p. 108, 1915. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 19 

Jx J130~ 

MICROFOSSILS OF THE OIL SHALE OF THE GREEN RIVER FORMATION 

1. Large bacillus? 6. Chain of conidia? similar to those of Bispora. 

2. Ascospore of Leptosphaeria sp.? 3. Spore of Pestalozzia sp.? 

4. Trichobacteria? 

5. Spores resembling those of Septonema. 

7. Phacus sp. cf. P. caudata Hiibner. 

8. Chroococcus? sp. cf. C. westii (W. West) P . Boye. 9. Chroococcust sp. cf. C. dispersus (V. Keissler) Lemmerman. 

10. Crinaliumt sp. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 20 

MICROFOSSILS OF THE OIL SHALE OF THE GREEN RIVER FORMATION 

1. Spores resembling those of Trichothecium, 1\Jycosphaere/la, and Didyme/la. 2. Chain of conidia resembling those of several genera of H yphomycetes. 3. Spores resembli ng those of Helminthosporium . 4. Germinating spore suggestive of rienderson}a sp. 5. Chains of conidia suggesting those of Torula 

6 . Conidia and sporophores resembling Cladosporium sp. 7. Spore similar to the conidia of Brachysporium sp. 8. Group of spores ugge tio ~ sorns of Uromyces sp. 

9. Spores (esembling those of Macrosporium sp. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 l 'LATE Zl 

MICROFOSSILS OF THE OIL SHALE OF TiiE GREEN RIVER FORMATION 

1. Crinalium? sp. cf. C. endophyticum Crow. 

2, 3. Jlapatosiphon sp. cf. H. confervaceus Borzi. 

4. A member of the Protococcaceae, cf. Ere;nosphaera De Bary. 

5. Coelastrum1 sp. cf. C. verrucosum Reinsch. 

6. Tetraedron sp. cf. T . regulare var. torsum (Turner) Brunnthaler. 

7. Microspora sp. cf. M. pachyderma (Wille) Lagerheim. 
U . S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 22 

MICROFOSSILS OF THE OIL SHALE OF THE GREEN RIVER FORMATION 

1. Stigeocloniumf sp. cf. S. lubricum (Dillwyn) Kiitzing. 2. Alga, probably one of the Chroococcaceae. 3. Eoglobella longipes Bradley, n. gen. and sp. 4. Alga with some of the vegetative characters of the Siphonales. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 23 

MJCROl<OSSTLS OF THE OIL SHALE OF THE GREEN RIVER FORMATION 

1, 2, 5, 7, 8, 11. Spores. 3. Alga, possibly related to Vaucheria De Candolle. 

4. Zygospore, perhaps of a desmid. 

6. Large tetrahedral spore. 

9. Group of spores. 10. Optical section of a fern sporangium. 12. Fern sporangium with annulus. 
U. S. GEOLOGl CAL SURVE Y PROFESSIONAL PAPER 168 PLATE 24 

MICROFOSSILS OF THE OIL SHALE OF THE GREEN RIVER FORMATION 

1. Peristome tooth ? of one of the Bryales. 2. Transverse section of bark. 5 . Spiral thickening of a tracheid. 

6. Pollen of Pinus. 

3. Pollen similar to that of Thuja. 

4. Pollen similar to that of Quercus prinus. 7. Stellate plant hair? 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 25 

MICROFOSSILS OF THE OIL SHALE OF THE GREEN RIVER FORMATION 

1. Pollen similar to that of the Umbelliferae. 

2. Triangular pollen with very large apertures. 3. Trilobate spinose pollen grain. 4. Magnolia type of pollen. 

5 . Malvaceae type of pollen. 6. Citrus type of pollen. 

7. Quadrula minuta Bradley, n. sp. 8. Tupelo type of pollen. 9. Dif!lugia calcifera Bradley, n. sp. 10. Euglypha robusticornis Bradley, n. sp., individual with 5 spines. 11. Euglypha robusticornis Bradley, n. sp., individual with 4 spines. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 26 

A. A PREDACEOUS MITE BELONGING TO THE CHELYTIDAE 

B. SPECIMEN SHOWN IN A ENLARGED SO AS TO SHOW DETAILS OF HEAD PARTS 

MICROFOSSILS OF THE OIL SHALE OF THE GREEN RIVER FORMATION. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 27 

MICROFOSSILS OF THE OIL SHALE OF THE GREEN RIVER FORMATION 

1. Eyes of a minute adult insect. 2. Wing scales of Culicidae"? 

3. Insect eyes and wings. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 168 PLATE 28 

MICROFOSSILS OF THE OIL SHALE OF THE GREEN RIVER FORMATION 

l. Larva of Tabanidae. 

2. Larva of Chironornidae. 3. Larva of Odontomyia sp. 

4 . Larvae of Syrphidae. 

5 . Larva of Litholtypoderma sp. 6. Stiff, bristlelike hairs of an insect. 7. Plumose appendages of insects. 
·FLORA., OF THE OIL·SHALE 

species,.]J.· arhisa Borzi, which is 30 to 40 ·microns· in 

·diameter, is too s:mall. Furthermore, as Prof. Gilbert 

Smith 1* has pointed out to the writer, neither E. mridi8 

npr·B. arh,iza would·be expected far out in a lake like 

~· · aneitmt ·Uinta Lake. Eremosphaera is generally 

1 

found: in sphagnum bogs associated with desmids, and 

only one fossil of the Green River microfiora might. 

conceivably be interpreted as a desmid. (See pl. 23, 

fig. 4.} Botrydiopsis arhiza is a distinctly terrestrial ~a. , 

. Occurrence: The individuals are plentiful in the oil 

shale of the Green River formation, but the best ones 

were found in a sample of oil shale collected by E.G~ 

·Woodruff from Asphalt Tunnel, about 2,300 feet above 

the base of the formation, in sec. 1, T. 7 S., R. 98 W., 

Garfield County, Colo. 

Fam.ily AUTOSPORAOBAB 

Genus TETRAEDROli X1itzing 

·the fossil ~ure about .Ql millib,leter. :a.t.: 'tibet; 

irregulJ}X lobes on th~ cells f the .fossil ate app~'. 

more rounded and larger in roportion to the size ol:tlut~ 

cell thap. the irreglllar ;wart ke prominences on the ceB.;, ·1 

of 0. verrucoBUm. ·. N&cvertij,eless, in number, size, and:~ 1 

general asp. ect the cells. ar.. e~n· early en?~gh• ·like thosf) ~f·. I 

0. verrucosum to wa.rrant t e suggestlon th~t the fossil 

is probably a species' of a elastrum comparable to 0~ 

verrucosum. : 

Occurrence: In a $-&mp~ of oil shale collected by 

E. G. Woodruff from As.,halt Tunnel, about 2,300 

feet above the base of the formation, in sec. 1, T. ·7 S., 

R. 98 W., Garfield County~ Colo. 

Order ULOlruCHALIS 

Fatnily ULOtmCHACIAI 

Genus JIIOR~PORA Thuret 

.Microspora sp. cr. H. ~erma (WIDe) Lagerhetm. I 

Plate 21, Figure 7 

Tetraedron sp. cr. T. :reguiare var. torsum. (TUrner) Brunn:th.aler Microspora sp. cf. M. padkyderrka (Wille) Lagerheix:D.. Bradley,. 

Centralbl. Mineralogie, ~bt. B, No.5, pp. 186-187, 1929;. Plate 21. Figure 6 

Tetraedron sp. cf. T. regulare var. torsu,m (Turner) Brunnthaler. Torrey Bot. Club Bull., rol. 56, PP· 424:-425, 1929. 

Bradley, Centralbl. Min.eralogie, Abt. B, No. 5, pp. 185- I This alga, which is repr~sented in the nueroflora of 

186, 1929; Torrey Bot. Club Bull., vol. 56, p .. 424, 1929 . f · ..J... b · 1 f · the Green R1ver onnatlvjU y a smg e ragmen,t, IS· 

This alga. shows a remarkable resemblance to the . very close to M. pacltyde,rma in filament structure, 

living Tetraedron regulare '\Tar. torsum. It is finely pre- : cell shape, and ·dimensions~. The filament of the ·fossil· 

served and shows no shrinkage cracks. It is brownish ! is about 16.5 microns in di~meter, and the cells average 

orange-colored, and although clear and translucent it : 13.5 microns in diameter I and 20 microns in length·. 

is somewhat darker than the groundmass, which ranges Pascher 20 gives the ·dimeJlsions.of M. pachyderma· e;s. 

from reddish orange-colored to light lemon-yellow. 9 to 12 microns wide and lone to two times as long a$ 

The alga appears to be perfectly homogeneous, and all wide. · ; · · · 

differentiation between the cell wall and contents has The color of this fossil is unusual. It is pale lemondisappeared. . yellow and almost transp~rent, whereas most of the 

Occurrence: In a sample which upon distillation ! algae in the oil shale a~e re1dish ye~ow? reddish orangeyielded 44 gallons of crude oil to the ton, collected by colored, or dark reddiSh ijrown. This color suggests 

D.·E. Winchester from a bed of blackpyritiferous thin- that the plant is not.mucti bituminized. · The.color is 

bedded oil shale in the Oil Shale Mining Co.'s qu~y, I very close to that of the ppllen' grams· ruui waxy spore 

sec. 27, T. 7 S., R. 100. W., Garfield County, Colo. I exines and might perhaps ijldicate that the living plant 

had a different compositiqn from most of the. o·thers 

associated with it. . l · . Genus COBLASTRUII liitgeli 

CoeJastrum.? sp. cr. c. verrucosum. Retnsch 

Plate 21, Figure 6 

Occurrence: This spechnen ·was found in an un,;. 

labeled microtome sectio~ ·.in the collection . of· C. A. 

Pediastrum sp. Davis, Nat. Acad. Sci. Proc., vol. 2, p. 116, 1916. Davis. The thin section fs clearly oil shale from the 

Coelastrum? sp. cf. C. verrucosum Reinsch (or Pediastrum sp.). Green River formation, b~t the locality is unknown. 

Bradley, Torrey Bot. Club Bull., vol. 56, p. 424, 1929. 

This group of cells, which Davis regarded either as a 

Pediastrum or a member of a closely related genus, is 

probably. a Ooelastrum, and Professor Smith 18 pointed 

out its similarity to 0. verrucosum Reinsch. According 

to this interpretation the group of eight cells represents 

a flattened and partly fragmented coenobium whose 

cells were more or less rounded and irregularly lobed. 

The individual cells of 0. verrucosum, according to 

Reinsch, 19 are 0.0097 millimeter in diameter. Those of · 

ta Personal communication, January, 1928. 

u Reinsch, P. F., Contributiones ad ftoram algarum aquae dulcis Promontorii 

Bonae Spei: Linnean Soc. London Jour., Botany, vol. 16, p. 238, pl. 6, fig, ;J, 1877~ 

Familr CliABJOPHORACBAB 

Genus ~TIGBOQLOllliU. XtitziDg 

Stlgeoolontuin? sp. cr. s. ~brtcum (l)mJVYD.) Kdtzmg 

Plate ~ Figure 1. 

Stigeoclonium·'l sp. cf. S. ZubricJm (Dillwyn) ·Ktitzing. Bradl~y,. Centralbl.·Mineral. ogie, ~bt. B, ·No: 5;'pp. 1. 87!'"1897 19~; 

Torrey Bot. Club Bull.,] vol. 56, p. 426, '1929~ · ·' I . 

It is not at all certain th~t this fr~gm~t of a bran~h:.. 

ing alga belongs here. · Tpo few of it~ characters are · known to be sure; in "the! first pla.ce, whether it is a . 

ao Pascher, A., op. cit., Heft 6, p. 152, f914 •. 

•• -.f-
44 ORIGIN AND MICROFOSSILS OF OIL SHALE OF GREEN RIVER FORMATION 

member of .the Chlorophyceae or ·the Cyanophyceae. 

However, it is placed here provisionally because its 

manner of branching and the size and shape of the 

cells are so strongly suggestive of S. lubricum. The 

cells are quadrate or cask-shaped and range in diameter from about 7 to nearly 10 microns. Hazen 22 gives 

the diameter of the branchlets of S. lubricum as 6 to 7 

microns and the diameter of the principal filaments 

as 14 to 16.5 microns. The fossil, which is unusually 

large compared with other specimens of the microflora, also resembles the. blue-green alga Oapsosira 

Ki.itzing. 

Occurrence: In a sample of oil shale collected by 

E. G. Woodruff from Asphalt Tunnel, about 2,300 

feet above the base of the formation, in sec. 1, T. 7 S., 

R. 98 W., Garfield County, Colo. 

Family undetermined 

Genua IOGLOB:BI.LA Bradley, n. gen. 

. Eoglobella lon.glpes Bradley, n. sp. 

Plate 22, Figure 3 

Thallus of definite shape, radially symmetrical, con-

. sisting of a single spherical cell to which are attached 

four equally spaced, greatly elongated cylindrical 

appendages. These are apparently single cells that 

are enlarged-and flattened where they join the globular 

cell and tapered to a rather blunt conical point at the 

distal end. They arise from the globular cell a little 

below the. equator and diverge slightly downward. 

The globular cell is about 38 microns in diameter; 

the appendages are about 6 microns in diameter and 

range in length from 115 to about 145 microns. The 

characters of the genus will also serve to define the 

species. 

This organism does not resemble any living algae so 

far as the writer is able to judge. The name was 

suggested by C. A. Davis and appears on the labels of 

his photomicrographs. Only ·a single specimen has 

been fo~nd. 

Type: The type, which is also the genotype, is a 

photomicrograph taken for Charles A. Davis. The 

negative, No.3, is filed in the photographic laboratory 

of the United States Geological Survey, Washington, 

D.C. 

Occurrence: In a sample of oil shale collected by 

E. G. Woodruff from Asphalt Tunnel, about 2,300 

feet above the base of the formation, in sec. 1, T. 7 S., 

R. 98 W., Garfield County, Colo. 

UNCLASSIFIED FORKS 

Plate 22, Figure 4.-This alga apparently has the 

general vegetative characters of the Siphonales. The 

fronds are continuous, without dissepiments eX,cept 

perhaps at the junction of the stem and branches, but 

.at those places the fossils are too opaque to make out 

22 Hazen, T. E., The Ulothricaceae and Chaetophoraceae of the United States: 

Torrey Bot. Club Mem., vol. 11, p. 196, 1902. · 

the internal structure. Except for the minute size 

and the absence of roots, the fronds, which are cle&l'ly<~ 

differentiated into stem and foliaceous branches, resem- · ble species of Oaulerpa Lamouroux, . which is marine.·, 

The stolon was apparently horizontal and either rested 1 

on the bottom or' was shallowly buried, for the branches· 

all arise from one side of it. The branches have a· 

variety of shapes: some are relatively broad at the 

base and taper uniformly to a point; others are narrow 

at the- base, broaden distad, and terminate in a blunt· 

point; a few have rounded tips; and still others, usually short ones, are filiform with vecy acute tips. The 

branches a:re about 5 microns thick, but they were . 

probably originally somewhat thicker. They range· 

in length from about 83 to 675 microns. The broadest 

foliaceous branches are about 33 microns wide, but· the 

filiform branches are not more. than 8 microns. Both 

the branches and the stolon are homogeneous and 

excessively cracked by shrinkage. Apparently the . 

membranaceous tissue was firm and tough. The 

branches are dark reddish brown but translucent, 

whereas the stolon is opaque. 

Occurrence: Two complete plants and many isolated 

branches have been found in the oil shale. Most of 

these were found in thin. sections cut from a sample 

collected by E. G. Woodruff from Asphalt Tunnel, · 

about 2,300 feet above the base of the formation, in 

sec. 1, T. 7 S., R. 98 W., Garfield- County, Colo. A 

few were found in sections cut from a sample of oil 

shale collected by D. E. Winchester at an unknown 

locality along ·Parachute Creek, Garfield County, 

Colo. 

Plate 22; Figure 2.-This closely agglomerated mass 

of cells probably represents a member of the Chroococaceae, perhaps either Aphanocapsa Nageli or 

Microcy&tis Ki.itzing. Yet in one part of the mass· the 

cells appear to be clearly united into fila.ments that 

show repeated dichotomous branching. In this respect 

they resemble certain species of the green alga Ohaetophora Kutzing. 

Occurrence: In a sample of oil shale collected by 

E. G. Woodruff from Asphalt Tunnel, about 2,300 

feet above the base of the formation, in sec. 1, T. 7 8., 

R. 98 W., Garfield County, Colo. 

Plate 23, Fig-ure 3.-Apparently this cystlike cell 

grew upon the filament. The texture, color, and 

shrinkage cracks of the two parts appear to be identical 

and strengthen the impression that the fossil consists 

of a nonseptate filament to which is attached a large 

spherical cell. If this interpretation is correct the 

fossil.has some of the characters of the Siphonales, and 

the large spherical cell suggests the oogonium of 

Vaucheria De Candolle. · · 

Occurrence: In . a sample of oil shale collected ·by 

E. G. Woodruff .from Asphalt Tunnel, about 2,300 

feet above the base of the formation, in sec. 1, T. 7 S.,. 

R. 98 W., Garfi'eld County, Colo. 
FLORA OF THE OIL SHALE 45 

· Zygospore of desmidt (pl. 23, fig .. 4).-This delicate 

fossil may possibly be the zygospore of a desmid. Its 

appendages are too short .for it to be the perithecium 

of a .powdery mildew. 

Occurrence: Asphalt Tunnel, about 2,300 feet above 

the base of the formation, in sec. 1, T. 7 S., R; 98 W., 

Garfield County, Colo. 

BRYOPHYTA AND PTERIDOPHYTA 

Spores, sporangia, annuli, and ·scattered fragments 

of tissues of mosses· and ferns are also found in the oil 

shal~ and in chert concretions. These the writer feels 

entirely unqualified to classify. Photomicrographs of 

some of· the better_ preserved of them, together with 

brief descriptive notes on the spores, are included in 

this report for the sake of completeness. In the titles 

of a few the writer has suggested comparison with 

certain large groups of living plants. 

MOSS AJID FBRl'f SPOUS 

Plate 23, Figure 5.-Exine thick, translucent, 

brownish yellow, rather coarsely scabrous and somewhat obscurely reticulate. No lines of rupture are 

discernible. 

Occurrence: Chert concretion fr-om a bed of oil shale 

about 1,300 feet above the base of the formation, in 

sec. 19, T. 5 S., R. 96 W., Garfield County, Colo. 

Plate 23, Figure 2.-A large .tetrahedral spore with 

a thick rigid exine and prominent episporic ridges 

along the interfacial· angles. Elsewhere there is either 

no epispore or it is so thin as to be· indistinguishable . 

from the exine. The surface is minutely granular, 

almost smooth. The color is light orange. 

Ooourrence: Asphalt Tunnel, about 2,300 feet above 

the base of the formation, in sec. 1, T. 7 S., R. 98 W., 

Garfield County, Colo. 

Plate 23, Figure 6. -8everal of these microspores 

have been found. They are clear deep yellow, and all 

are finely preserved except for a few shrinkage cracks. 

The exine is very thick and perfee,tly smooth, and the 

lines of dehiscence are long and sharply defined. The 

diameter of the spore measured from the middle of 

one side through the center to the opposite angle is 

61 microns. Renault 23 described tetrahedral spores 

from a Russian boghead from Kourakino that are 

identical with these. 

Plate 23, Figure 7.-An ellipsoidal spore with a thick 

scabrous epispore, which is not notably thickened 

along the lines of rupture and which is without ridges 

or spines. The color is strong reddish orange. · 

Occurrence: Asphalt Tunnel, about 2,300 feet above 

the base of the formation, in sec. 1, T. 7 S., R. 98 W., 

Garfield County, Colo. · 

Plate 23, Figure 1.-These perfectly smooth, spherical spores, which are pale yellowish orange-colored 

and translucent, are fairly common in oil shale from 

various parts• of ,the formation.. They are of very 

nearly the same color and index. of refraction as. the· 1

structureless organic matter· and so do not-photograph 

well.· The lines of dehiscence,. howev.er, ·are plainly: 

visible. · . 

Occurrence: Asphalt Tunnel, about 2,300 feet &bove · 

the base of the formation, in sec. 1, T. 7 8., R. 98 W~,) 

Garfield County,. Colo. . · 

Plate 23, Figure B.-This spore has .a rather thin . 

exine but a well-developed epispore, which is distinctly 

and coarsely reticulated with low but sharJ?ly defined 

episporic ridges. It is obviously broken and empty. 

This resembles the spores of some lycopods. 

Occurrence: Chert concretion from a hard ostracodebearing shale about 140 feet above the base of the for-· 

· mation in sec. 27, T. 11 S., R. 10 E., Duchesne. County, 

Utah, along the road from Castlegate to Duchesne. 

Plate 23, Figure 9.-8pores of this sort are fairly. 

common in the oil shale. This group of them shows 

particularly well the differentiation between the exine 

·and epispore, especially the central spore, which is cut 

:longitudinally. The exine and co~tents of that spore 

:have shrunk away from the epispore. The spores are 

reniform and slightly flattened, suggesting that they 

were united in a tetrad. The exine is thick and rigid . 

and is sheathed with a thick epispore, which is ornamented with high ridges and coarse conical and truncate 

conical spines. The spines are rather openly distributed over the surface. These spores resemble spore8 

of some of the Marchantiales. 

Occurrence: Asphalt Tunnel, about 2,300 feet above 

the base of the formation, in sec. 1, T. 7 8., R. 98 W., · 

Garfield County, Colo. 

Plate 23, Figure 11.-This spote has a thick rigid 

exine and an epispore which is ornamented with thickly 

set, sturdy conical spines. Locally the epispore is thickened but not in ridges. Lines of rupture are not discernible. The color is dark reddish orange. This 

specimen resembles the spores of some of the Marchantiales. 

Occurrence: Asphalt Tunnel, about 2,300 feet above 

the base of the formation~ in sec. 1, T. 7 S., R. 98 W., 

Garfield County, Colo. 

Plate 23, Figure 12.-Several fern annuli have been · 

found in the oil shale. One photographed by Davis is 

shown in Winchester's latest bulletin.24 The annulus 

illustr~ted in the present report, . however, is still in 

place on the sporangium. The cells within the spo~ 

rangium have disappeared, and the space is now filled 

with chalcedonic quartz. Presumably this is the 

sporangium of a leptosporangiate fern. 

Occurrence: Chert concretion from a hard bed of 

ostracode-bearing shale about 140 feet above the base 

of the formation, in sec. 27, T. 11 S., R.lO E., Duchesne 

County, Utah. 

2a Renault, B., Sur quelques microorganismes des combustibles fossiles: Soc. ind. 24 Winchester, D. E., Oil shale of the Rocky Mountain region: U. S. Geol. Survey 

min. St.-Etienne Bull., 3d ser., vol. 13, p. 1036, 1899. Bull. 729, pl. ·7, C, 1923. 
46 ORIGIN AND MICROFOSSILS OF OIL SHALE OF GBEEN RIVER FORMATION 

Plate 23, Figure 10.-This fossil is apparently an 

optical section of a sporangium. It shows plainly a 

number of cells whose dark granular contents· have 

been preserved. There is apparently no· annulus on 

.the sporangium. 

Occurrence: Chert concretion from a· hard bed of 

ostracode-bearing shale about 140 feet above the base 

of the formation, in sec. 27, T. 11 S., R. 10 E., Duchesne 

County, Utah. 

Plate 24-, Figure 1.-This tapered filament strongly 

resembles the tip· of an outer peristome tooth of one of 

the Bryales. 

Occurrence: Asphalt Tunnel, about 2,300 feet above 

the base of the formation, in sec. 1, T. 7 8., R. 98 W., 

Garfield County, Colo. 

SPERMATOPHYTA 

GYMl'iOSPERJIAE 

The gymnosperms are represented in the oil shale 

only by the pollen of Pinus. Notes and photographs 

by C. A.· Davis published in Winchester's bulletin 25 

record the occurrence of Picea and Pinus pollens. 

His photomicrograph of Pinus pollen is reproduced 

in this report· as Plate 24, Figure 6. The writer has 

not been able to establish to his own satisfaction the 

presence of Picea pollen, though it is likely enough 

present. Pine pollen, as might be expected, is widely 

distributed in the oil shale, and most of it is very 

finely preserved. Most grains are lemon-yellow, clear, 

and of so nearly the same index of refraction as the 

structureless organic matter that it is often most difficult to discern them. 

ANGIOSPERM:AE 

Davis 26 also recorded, the occurrence of pollen and 

fragments of tissues of angiosperms in the oil shale. 

He mentions also bark cells. His photomicrograph 

of a group of bark cells is reproduced in this report as 

Plate 24, Figure 2. As fragments of the tissues of 

higher plants are extremely rare in the oil shale their 

state of preservation is perhaps worthy ·of pas~ing 

· note. Hence some notes on these bark cells, a spiral 

tracheid which the writer found, and some stellate 

·plant hairs are included here. 

Transverse section or bark 

Plate 24, Figure 2 

The fragment consists of a few layers of typical 

flattened, prismatic cork cells whose walls are much 

thickened secondarily. · On the convex side of the 

strip are a few layers of thin-walled cells, much compressed and imperfectly preserved. These appear to 

be remnants of the cork cambium. A thin layer of 

poorly defined tissue on the other side may represent 

some of the bark. · Owing to suberization and an 

adsorption of tannins, the secondary . thickening of 

2t Winchester, D. E., op. cit., p. 32, pl. 7, A. 

2t Idem, p. 32. 

cork and bark cells .become8 very resistant to .:d~Jil. ... 

position and persists long after. the .pnr-ely -eellul0sio1 < 

tissues have been destroyed. The middle :cla.tnella ;~; 

cork cells is usually lignified. · RenaUlt zr , :described; 

two varieties of Micrococcus paludis which he lolmd to .. 

be especially common in the woody tissues in peats;: · 

the variety a he found. attacking most ·frequently the, 

thickening of cell walls, and the variety {3. was most 

frequent in the median lay~rs. ·He _also found 28 that 

when the constituents of lignites were in a very .advanced state of disorganization the bark was usually 

reduced to the :Battened cork cells. . " · · 

The fragment of bark from the oil shaJ.e·$nows ·a 

stage of disorganization apparently simil~r . tO th,.t· 

described by Renault. The middle lamellae· haye 

almost entirely disappeared from .·the 90rk eel~. 

Microbian activity very prol;>ably accounts for. Sl\Ch a 

· selective destruction. Unfortunately Davis's thin 

section from which this photograph was taken. has 

been lost, and it is useless to look for the traces ·of 

bacteria, such as ·corrosion pits, at this magnifi0ft#on~­

At least it is evident that the median layers of the·aeJ.t 

walls must have been destroyed after the bark strip 

was entombed in the -orgari.ic ooze, or it would not have 

retained its organization. The suberized secondary 

thickenings were little affected by the. process~ but they · 

have been so much compressed, by mechanical action 

or shrinkage, that the lumen is visible in but few _of 

the cells, and in these it is represented by a mere 

.longitudinal slit. 

Occurrence: Asphalt Tunnel, about 2,300 feet. above 

the base of the formation,· in sec. 1, T. 7 8., R~ 98 W., 

Garfield County, Colo. 

Spiral thickening ot tracheld 

Plate 24, Figure 5 

This fragment represents a conducting vessel of a 

vascular plant. Only the strongly humified · spiral 

thickening remains;, the thinner and probably less 

lignified cell walls have disappeared in the maceration · 

through which the original tissue must have passed.· 

The fragment is dark reddish brown but still trans ... -

lucent. If the color and ·opacity may serve as indi..; 

cators, it has apparently reached about th-e stage· of 

carbonization of similar plant tissues in woody lignites. 

Occurrence: Locality unknown; the fossil was 

found in an unlabeled microtome section of Green 

River oil shale in the collection of C. A. Davis. 

Stellate plant hair? 

Plate 24, Figure 7 

These minute fossils seem most likely to be stellate 

. plant hairs, despite the fact that no point of attachment or stalk can be discerned on them. The leaves 

t7 R-enault, B., Sur quelques microorganismes des combustibles totisiles: Boo", 

ind. min. St.-Etienne Bull., 3d ser., vol. 13, p. 892, 1899. 

11 Idem, p. 945. 
I 

FLOB:A. OF THE OIL SHAL1il 

Qf at leas~ two vascular pl~ts, Vi~ alnijolium 29 

and· Ma1'7'Ubium peregrim.tm, 30 have stellate ·. hairs 

comparable to these fossils. Some of the · peltate , 

scales from the petals of Thesjleaia poptdnea also 

resemble• these fossils rather closely.31 All the plant 

hairs have definite cell wallS, and no trace of this 

sil1lctlire can be m·ade out in the fossils. There 

remains the possibility that these forms are unicellular 

algae unlike any known species. 

Pollens 

Pollens in great number and diversity occur in the 

oil shale, and many of them show their structural 

characters with fair clarity. If these pollens could 

be surely referred to their proper genera they would 

shed much additional light upon the flora of the Green 

River epoch. ·Unfortunately the morphology of pollens is imperfectly known, and consequently they have 

never been accurately correlated with the elassified 

plants. Mohl 32 cla.Ssified a great many pollens according to their superficial rather than fundamental 

characters, and in · consequence, as W odehouse 88 . 

points out, many of his groups widely separate species 

of the same genus and also associate species of totally 

unrelated ·plants. However, Wodellouse's studies 34 

established the fact that there are certain fundamental 

characters of pollen grains, 'such as the structure and 

shape of the germ apertures and textures of exines, 

which are constant within certain orders or families. 

These fundamental characters may also be found. in 

other families, but taken with the superficial characters, such as ornamentation, number and arrangement 

of folds, and shape and size of the grains, they show 

a profound and intimate phylogenetic relationship 

of the pollens with the plants. In the hope that the 

morphology and relationship of pollens to the classi-

. fied plants will be known these pollens are described 

in notes that make clear as many as possible of the 

characters that W odehouse found to be of taxonomic 

value: 

Doctor Wodehouse is now making a ·systematic 

study of the pollens found in the writer's thin sections 

of oil shale and chert from the Green River formation 

and expects to publish later the results of his investigations. 

Some comparisons of the pollens with those of living 

plants are suggested here, but they are not to be 

regarded as rigorous de_terminations. The comparisons are based in part upon examination of fresh pollens 

ao McCleery, E. M., Stellate hairs and pelt11te scales of Ohio plants: Ohio Natur-

.alist, vol. 7, No. 3, pp: 51-M, pl. 6, figs. 25, 26, 1907. 

· ao Schmidt, Carl, Vergleichende Untersuchungen fiber die ~ebaarung der Labiaten nnd Boragineen (Inaug. Diss., Univ. Freiburg, Berlin), p. 39, fig. 7, 1888. 

at YOOJliDllUl. W., and Pande, S. S., The epidermal outgrowths of the genera 

Thupufa and Go:tB1fPium: Annals of Botany, vol. 43, p. 722, pl. 19, fig. 25, 1929. 

at MOhl, Rugo von, Sur la structure et les formes des graines' de pollen: Annales 

. sci. nat. bot., vol. 3, p. 148, 1835~ . 

aa Wodehouse, R. P., Morphology of pollen grains in relation to plant classification: New York Bot. Garden Jour., vol. 71, p. 145, 1926. K Idem, pp. 145-151. • . 

. . 

and in part upon Young's key for the detemiinauioa,·of . 

pollens,35 which aimS .. simply to ~P similar _}loll$D. 

grains and thus indicate more or less: closely :tli.eir' 

relationships. '· · 

Plate 24, Figure B.-Apparently there are ·t11ree 

equally spaced gerp1 ap~rtures in this pollen. The 

thin smooth walls of the grains are notably thickened 

around the apertures. Grains like this are very pleati--

ful in the oil shale and chert concretions~ 

The writer compared these grains with fresh TAuja 

pollen, and they seem to be identical in every respect. 

Plate 24-, Figure 4.-The three distinct germ apertures on these pollen grains are in slight bosslike 

elevations which are equally spaced around the periphery. The walls are comparatively thin except 

near the bosses, where they are somewhat thickened. 

The writer compared these grains, which are not 

common, with fresh QuerC'Us pollens. · They are very 

similar to Q. prinus. 

Plate 25, Figure 1.-In these pollens there are two 

pores midway on the grain ·and two on t~e inner edges 

of the longitudinal folds~ The pair on the folds are 

shown by the semicircular indentations. The ·exine is 

thick, rigid, and finely granular except between the 

longitudinal folds, where it is smooth and apparently 

·thin. The longitudmal folds ·are hlgh 'and prominent 

and extend the full length of the grain. · 

According to Erdtman36 most of the Umbelliferae, a 

family of herbaceous plants that includes Oarum carvi 

(caraway), have pollen grains like these. They are · 

very common in many beds of oil shale and in the chert 

concretions. · 

Plate 25, Figure 3.-The single pore of this trilobate 

grain is near the center of the grain, in a slight depres-. 

sion within a short groove between two of the rounded 

lobes. The grains are thickly beset with fine -cylindrical spines. There are apparently no folds, and the 

exine seems to he fairly thick and rigid.· 

These grains are common in the oil shale and in chert 

concretions. They do not find a place in Young's 

classification, nor has the writer been able to find any 

to compare them with. 

Plate 25, Figure 4..-This grain is a large depressed 

ellipsoid that has on one side a clear, highly refringent 

lunate margin. The exine is very thick, strong, and · 

conspicuously scabrous. No pores were observed. 

It runs out in Young's key to the magnolia type. 

These grains are only slightly larger than those. of 

Liriodendron sp. They are not plentiful in the. oU 

~al~ ' 

Plate.25, Figure 5.-0nly part of this grain sl,lows in 

the photograph. It is spherical, apparently without 

pores, and ornam~nted with rather openly spaced ~ong 

aa Browne, c. A., and Young, W .1., ChemicaiSnalyses and compositions of AII,lerican honeys, including a microscopic study of honey pollen: U.S. Dept. Agr. Bur . 

Chemistry Bull. 110, pp. 7o-93, 1908. · 

38 Erdtman, G., Beitrag zur Kenntnis der Mikrofossilien in Torf und Sedimenten: 

Arkiv for Botanik, Band 18, Hiilfte 4:, pp. 2-3, fig. 3, 1924. 
48 ORIGIN AND MICROFOSSILS OF OlL SHALE _·oF GREEN RIYER FORMATION 

conical spines. The exine llas a mlcrogranula.r texture 

and does not appear to be thick. 

This falls in Young's mallow type, but it is slightly 

smaller than the pollen of most Malvaceae. These 

grains are not plentiful in the oil shale. 

Plate 25, Figure 2.-This somewhat triangular pollen 

grain has three very large germ apertures situated at 

the angles. The exine is thick, rigid, and smooth. 

No folds are discernible. 

According to Dr. A. E. Longley,37 of the Bureau of 

Plant Industry, this pollen resembles pollen of some 

of the Primulaceae. Very few of these grains have 

been found in the Green River formation. These grains 

also resemble the pollen of Betula sp., Oorylus sp., 

and Ostrya carpinifolia, according to the figures of 

Erdtman.38 

Plate 25, Figure 8.-The four germ pores which are 

located at the angles of this tetrahedral pollen are small. 

·The exine is thin and perfectly smooth. 

It resembles closely the tupelo type of Young but 

is somewhat smaller. It also agrees fairly well with 

the pollen of Oorylus sp. figured by Hesmer.39 These 

grains are uncommon in the oil shale .. 

Plate 25, Figure 6.-This pollen grain is subquadra:te, and the small germ apertures are at the corners. 

They are marked by slight depressions and slight 

thickenings of the wall. The exine is thin and perfectly smooth. . 

This runs out to the citrus type in Young's key. 

Only one such grain has been found. It may, however, 

be a diagonal section of the pollen of MyriophyUum 

spicatum according to Erdtman 's figure. 40 

FAUNA OF THE OIL SHALE 

The microfauna of the oil shale is not large. It 

includes representatives of the Protozoa and Arthropoda. Fragments of insects very greatly predominate. 

The most remarkable member of this fauna is a finely 

preserved mite. 

PROTOZOA 

Clau SARCODINA 

Subclass RHIZOPODA 

Order TESTACBA. 

Family ARCELLIDAE 

. Genus DIFFLUGIA Leclerc 

DJ.mugta caJcl:lera Bradley, n. sp. 

Plate 25, Figure 9 

Shell pyriform, narrowed to a short cylindrical neck; 

mouth terminal, large, and apparently circular; fundus 

obtusely rounded; shell thin and composed of a compact mosaic of minute calcite grains. 

This rhizopod might with some justification have 

been referred to D. pyriformis Perty, frorq which it 

If Oral communication, March, 1927. 

as Erdtman, G., op. cit., p. 7, pl. 2, figs. 50-56. 

ao Hesmer, H., Mikrofossilien in Torten: Palaeont. Zeitschr., Band 11, Nr. 3, fig.ll, 

p. 246, 1929. 

fo Erdtman, G., op. cit., pl. 2, fig. 88. 

differs only in the kind of material uaed for. the -shell 

and in size. It is considera;bly smaller · than lilfJSt · 

species of ~fflugia. , 

Type: The type is in· a thin section of· a: chert concretion cut for the writer and marked 25/3 c; · It. is in 

the writer's collection at the United States Geological 

Survey,.Washington, D. C. 

Occurrence: In a small blaek pyritiferous chert con• 

cretion from a bed of hard carbonaceous ostracodebearing shale about 140 feet abo~e the base of the 

formation, in sec. 22, T. 11 S., R. 10. E., Duchesne 

County, Utah. 

Genus QUADRULA Schulze 

QuadrUI.a mJnuta BradleY,. n. sp. 

Plate 25, Figure 7 

Shell ellipsoidal, composed of distinct rectangul~ 

transparent plates regularly arranged in tiers transverse to the major axis of the shell, plates at either end 

notably larger and more triangular in outline. , By 

changing the focus of the microscope the outline of the 

plates on the other side of the shell may be clearly.~en 

through the upper layer of plates, and the small' oral 

opening at the right may be discerned. Near tq.e 

posterior end half a row of plates h~ been lost; only 

those on the lower side of the shell show at that place 

in the figure. The shell was probably once chitinoid 

and may even now be unchanged, as it is not marred 

by shrinkage cracks, nor is it colored reddish brown 

like so many of the oil-shale microfossils. No trace 

of the sarcode mass remains. The fossil is represented 

by three individuals.· 

Except for its minute size (28 microns long and 16 

microns wide) it might be included in the living species · 

Q. symmetrica (Schulze). The smallest individual of 

that species mentioned by Leidy41 is 80 microns long 

and 40 wide, and the largest 140 microns long and 96 

wide. The fossil species resembles most closely in .. 

shape an individual of Q. symmetrica figured by Conn/2 

but it is less than one-third the size of that individual. 

Type: The type is in a microtome section cut by 

Charle8 A. Davis and marked "No. 7." It is in the 

writer's collection at the United States Geological 

Survey, Washington, D. C. , 

Occurrence: Oil shale of the Green River formation, 

Uinta Basin of Colorado and Utah, exact location 

unknown. 

Genus EUGLYPHA Dujardin 

Euglypha robustlcorn1s Bradley, n. sp. 

Plate 25, Figures 10, u 

Shell spherical, 40.2 to 61.5 microns in diameter; com .. · 

posed of slightly overlapping elliptical translucent 

plates whose major axes are parallel to the axis of the. 

animalcule; plates probably consisted originally of chiti41 Leidy, Joseph, Fresh-water rhizopods of North America: U. S. Oeol. alld Geoc' 

Survey Terr. Rept., vol. 12, p.143, 1879. . 

'' Conn, W. H., The Protozoa of the fresh waters of Connecticut: Connecticut 

Nat. Hist. and Geol. Survey Bull. 2, pl. 3, fig. 20, 1905. 
,,_ ,

:.~' 

FAUNA OF THE OIL -SH.A.LB. 

· noid membrane~ Shell armed at the ·top with four or 

five exceedingly stout s-pines each of which tapers uniformly to a rather acute point; they appear to be hollow 

and thick walled. The ·spines range in length from 

about 30 to 80 microns in different individuals. On 

all specimens of the fossil species the spines are confined 

to a smaller area of the fundus. than those of living 

species, in which they usually arise from the sides more 

or less remote from the top. 

None of the specimens are so oriented as to show the 

mouth clearly. Two, however, present side views, and 

in both of these the oral end is devoid of denticulate 

· marginal plates: The opening appears to be a little 

more than one-third of the diameter of the shell. 

This protozoan is represented by four specimens, 

all rather well preserved. The shells are pale lemon-

. yellow to brownish yellow and translucent., but the 

spines are dark reddish brown and · nearly opaque. 

The shells are remarkably little crushed, and only the 

spines show breaks due to shrinkage after entombment. 

Type: The · type is in a microtome section cut by 

Charles A. Davis and marked "Loc. · P, sp. la, box 6, . 

slide 2." It is in the writer's collection at the United 

States Geological Survey,_Washington, D. C. 

Occurrence: The type specimen came from an unknown locality in either Colorado ·or Utah. It is. 

possible that the letter P refers to Winchester's location d!!signated by the same letter in sec. 22, T. 6 S., R. 

95 W., Garfield County, Colo.43 Other individuals are 

recorded by Davis's photomicrographs from Asphalt 

Tunnel, about 2,300 feet above the base of the formation, in sec.1, T. 7 S., R. 98 W., Garfield County, Colo. 

ARTHROPODA 

Class ARAORBIDA 

Order AOARIDA 

Family ORELYTIDAE 

Plate 26 

According to Dr. H. E. Ewing,44 of the United States 

National Museum, this niite is clearly a member of the 

. Chelytidae, but the smaller parts of the palpi by means 

of which the genera are distinguished are concealed, 

so that it can not be compared with any existing form 

now known. The living members of this family are 

predaceous and feed upon other mites. Only this one 

individual has been found in the oil shale of the Green 

River formation, and so far as Doctor Ewing is aware 

this is the first fossil mite to be reported from this hemisphere. It was found by C. A. Davis, under whose 

direction it was photographed. The thin section containing it was not among those which came to the writer 

when he began this study. The photographic negatives, Nos. 109 and 110, are filed in the photographic 

laboratory of the United States Geological Survey. 

43 Winchester, D. E., Oil shal~ of the Rocky Mountain region: U.S. Gaol. Survey 

Bull. 729, pp. M-55, pl. 8, 1923. 

" Oral communication, May, 1928. 

The oil shale from which the thin section wasnJ.. ·WM 

collected by E. G .. W oodrufi from Asphalt Ttamel, 

about 2,300 ·feet above the base of the Green .River 

formation, in sec.l, T.'5 S., R. 98 W., Garfield County, 

Colo. 

C1a.sa INDqTA 

Fragments of-insects are very common in many beds . 

of rich oil shale. Most plentiful are pieces of th~ 

·chitinous skins or sclerites. · Although many ~ 

apparently smooth or finely granular, others bear 

hairs or spines. In some seetions. the spines are still 

arranged in tiers. (See pl. 18.) The mono-, di-; and 

polyspiculated spines are characteristic· of dipterous 

larvae and particularly of the Oestridae or bot flies. 

(See pl. 28, fig. 5.) 

Much more remarkable and hardly less common 

are the ·remains of the eyes of minute but adult insects . 

(See pl. 27, figs. 1, 3.) Only the chitinous integument remains; the facets have apparently been decomposed. These eye remains commonly occur in pairs, 

and many of them are still attached to parts of the 

insect. These parts include antennae, wings, sclerites, 

hairs, and unidentifiable smooth pieces of the skin. 

H. G. Dyar,46 of the. United States National Mu.seum, 

thought that these insects were rather highly specialized, perhaps as much so as the Hymenoptera. The 

· wings of some are apparently paired and the antennae 

fork from a common cylindrical pillar. · 

David White 46 has long. regarded these peculiar 

netlike fossils as the eyes of insects, . but' apparently 

Davis 47 believed that they were plants, for in his 

notes he describes them as plants of a low order. 

(Seep. 38.) 

The minute scales from the wings of insects are 

plentiful in some thin sections of oil shale. (See pl. 

27, fig. 2.) These scales range in length from 61 to 

about 98 microns and in maximum width from 11 

to 18 microns. The striae are pale yellowish -brown, 

and the membrane between them is transparent and 

very difficult to differentiate from the straw-colored 

organic matrix in which the scales are embedded . 

Probably the membrane ·is colorless .. The striae are 

spaced about 1.5 microns ·apart, are essentially parallel, and end abruptly against the margins near the 

pedicle. The margins of the scales are entire except 

at the distal end, where the striae terminate in acute 

points, thus making the scale arcuate. The pedicles 

are cylindrical, not enlarged at the base, and rather 

· long. Although the scales are intermediate between 

the generalized hairlike type and the broad, digitate 

scales like tho~:~e of certain Lepidoptera they incline 

more toward the generalized type, because they ·are 

narrow. They resemble most nearly the scales on 

the wings of mosquitoes (Culicidae), of which four 

•a Oral communication, March,l927. 

" Oral communication, 1924. 

u Davis, C. A., notes cited in Winchester, D. E., Oilshaleofthe Rocky Mountain 

region: U. s. Geol. Survey Bull. 729, p. 32, pl. 7, B, 1928. 
ORIGIN AND .·~CROFOSSILS OF OIL SHALE OF GRE¥N' RIVER FOIWATION 

species, according to Winchester,41 have already been 

found in the Green River formation. 

Occurrence: These scales, together with fragments 

()f larger scales. whose structure is identical, are rath~r 

plentiful in thin sections. cut from a sample of oil 

shale collected by D. E. Winchester from a bed of 

black pyritiferous thin-bedded oil shale in the Oil 

Shale Mining Co.'s quarry in sec. 27, T. 7 8., R. 

100 W., Garfield Comity, Colo.· This sample yielded 

44 gallons of oil to the ton. · 

In addition to these there are also a few short 

'Seetions of legs showing the joints and pieces of cuticlebearing hairs. (See pl. 28, fig. 6.) Plumose appendages are not rare. Some of these have stout, rigid 

bristles but the bristles of others are fine and almost ' . . hairlike. (See pl. 28, fig. 7 .) 

Order DIPTEltA. 

Though the larvae of fli~s are plainly not microfossils and though they have not been given the 

detailed study they deserve, a few of them are included 

in this report because they are so abundant in certain 

zones in the Green River formation, especially in 

most of the rich oil shales. Dr. Charles. T. Greene, 

-of the Bureau of Entomology, has examined the larvae 1 

illustrated here and determined the families, and for 

·s<.me the genera, to which they belong. 

Family CHIRONO:MIDAE 

Plate 28, Figure 2 

Most of the members of this faJ:D.ily of minute flies 

.have aquatic larvae. They inhabit the bottom oozes 

Qf lakes even to great depths, for their oxygen requirements are apparently low. Fossil chironomid larvae 

are plentiful at certain horizons in the upper part 

of the Green River formation. The one illustrated 

was found about 2,200 feet above the base of the 

forrilat~on, in sec. 16, T. 5 S., R. 95 W., Garfield 

County, Colo. Adult members . of this family have 

been found on the bedding planes of certain marlstone 

beds, and three of them (Ohironomus septus Scudder, 

0. depletus Scudder, and 0. _patens Scudder) have 

already been described. 

Family STRATIOKYIDAE 

Genus ODONTOJIYU 

Odonto:myJ.a sp. · 

Plate 28, Figure 3 

These larvae ate, .aquatic and breathe through the 

tail spiracles while isuspended from the surface film. 

Many of them pupate in the mud close to shore. In 

the Green River formation these larvae are abundant 

and are associated with chironomid, mycetophilid, 

oestrid, and tabanid larvae and unidentified adult 

insects. The Odontomyia larva shown he~e was collected from a bed about 2,200 feet .above the base of 

"Winchester, D. E., op • .cit., p. 28. 

the formation, in sec. 16, T. 5·8., R. 95 ~,.,Garfield 

County, Colo. No adult s:Peciesof ~a,.~ · 

been described, ·but species of four related'g~~'Of 

this family have been described. · ' · 

. FamilY TAlU.BIDAB 

Plate 28, Figure 1 . :. 

To this family belong the hon~e flies, gad flies, deer · 

flies and the like. The larvae are predaceous, and 

ma~y are aquatic. In the Green ~iver formation these 

larvae are fairly plentiful. Specrme~s. were collected 

from a bed of marlstone about 1,500 feet above the 

base of the formation, in sec. 26,. T. 3 8., R. 99· W~, 

Garfield County, Colo. At this place they are. associ-. 

a ted with the larvae of Tabanidae, Oestridae, and. 

Mycet.Qphilidae, various adult insects, and a f~w 

leaves. Adults of this family apparently have not 

been described. 

Family SYBPKIDAI 

Plate 28, Figure 4 

The larvae of this family live in putrefying vegeta.ble 

matter. Their · well-preserved remains abound·.· .. i~ 

certain organic marlstone beds of the Green River 

formation. Those illustrated here were collec~ 

from a bed in the upper po.rt of the formation, hi the 

south half of T. 2 S., R. 95 W., Rio Blanco County, 

Colo. Adults of five genera of this f.amily have. been 

described. 

Family OISTRID.AB 

Genus LITHOHYPODBRIU. Townsend 

Ltthobypoderma sp .. 

Plate 28, Figure 5 

Genotype: Musca ascarides Scudder, U. S .. Geol. and Geog. 

Survey Terr. Rept., vol. 3, p. 551, 1890. . . 

These larvae are among the most interesting fossils · 

found in this formation. Scudder regarded them as 

probably members of the Muscid~e, despit~ their 

remarkable similarity to certain Oestndae, particularly 

11 Hypoderma 49 • d sp. Later Cockere exawne. new 

collections of these larvae and referred them ·to the 

living genus Hypoderma, though he said that .they 

should probably constitute a new .genus of Oestndae. 

Townsend 50 pointed out several distinct differences 

between the fossil larvae and Hypoderma and founded 

the new genus Lithohypoderma. Scudder's reluctance 

to place these larvae in the Oestridae 51 was apparently 

influenced somewhat by the difficulty he found in 

conceiving the conditions under which so man~ pa.ra- · 

sitic larvae could have becom.e embedded m the 

lacustrine mud, .for he said: · 

It would seem improbable that so large a number of oestrid 

larvae could be found, when the only way in which they eould. 

have reached· their present condition would be through, the 

droppings of animals affected by the bots standing in the water. 

•v Cockerell, T. D. A., Some American fossil insects: U. S. Nat. 1\lU&.· Proc., 

vol. 51, pp. 91-92, 1916. . 

ao Townsend, c. H. T., Lithoh1JPoderma, a new fQSSil genus of oestnds: IDsecutor 

inscitiae menstruus, vol. 4, Nos. 1G-12, pp. 128-130, 1916. 

11 Scudder, s. H .• op. cit., p. 551. 
· ··r!v:;';~i~!d:~~J:~ ··· '~ ". " 

, ~BPR!lWA'l'lpN ..ufn,SIGND'ICANCE OF 1$JAU~~-J,lB t-:'/:·.:::1.;: 

. ~ckerell'2 also expr,essed :a. littl& ~of _:ms doubt It may meft,Jl the;.t~.Lit~pode1'1!14· rMlly ·h~'·fk· when in referring to the rem,a.rk just· quoted frol!l another fa.n:xlly and. that. this is merely an ex~ifl 

Scudder he said: "This, however, is quite possible if oonvergent.evol.ution, or it::may mean that theSe,;~ 

they infested gregarious animals, though we must really forerunners of Hypoderma but were : &4~~ 

·~~:that the infestation seems· to have been remark- free-living forms that either f~P. .upon the deca~. 

ably he1,1.vy ." . . organic matter or war~ predaceous and fed up~ /~: 

The idea that these spinose larvae lived in tumors other ooze-dwelling organisms. The writer is inclin~>, • 

under the skin of mamm.als, like the modem species to regard the second hypothesis as. more proba~l~.: 

of· Hypoderma, ·and that their occurrence in the lake According to this idea these free-living forms acquired I 

beds is merely accidental and the result of their hav- their parasitic habit lEt.ter in geologic time. -

ing fallen from their hosts while the hosts were drink,;. · The Lithohypoderma larvae illustrated here (pl. 281 

ing from the lake seems to the writer. quite beyond any fig. 5) ~ere collected from a bed about 1,100 feet abov:~ 

reasonable possibility. The larvae are far too abun- the base of the formation on the west side of Piceanct 

dant and occur in continuous beds over far too large Creek, in sec. 11, T. 1 N., R. 97 W., Rio Bl~c9 

areas to have· come from that source~ In general, County, Colo. The group of oestrid 'iQ.Ntle shqwn,~ 

wherever they are found· they are numerous. Scat- Plate 2, B, were collected from a bed about 875 feit 

tered individuals are rather rare. On certain bedding above the base of the formation in the canyon of the 

planes so many larvae overlap one another as to make White River, in sec. 27, T. 9 S~, R .. 25 E.,. Uin.tah 

up continuous thin laminae of chitinous material. County, Utah. 

· But on most bedding planes of· the shale in the flylarvae zone of the Green River formation the larvae 

are very closely spaced or touch one another. (See 

pl. 2, B.) Furthermore, these beds that contain so 

many oestrid and other dipterous larvae are continuous 

over many! square miles. (See pl. 3.) Accordingly, 

it seems to the writer utterly inconceivable that so 

many animals coul.d have been so badly infested with 

hots as to drop the countless numbers of them that 

occur in these beds. Moreover, these larvae-bearing 

beds have been examined carefully at many places in 

Colorado and Utah, and no mammalian remains of 

any kind have yet been found in them, although in 

general watering places are particularly liable to have 

about the1J1 the bones of the animals that drink there. 

Again, if the~e maggots came from mammals the ooze 

into which they fell must have been thoroughly trampled so that all traces of original lamination were 

effaced; but, nearly all the larvae-bearing beds are. 

rather 'thinly laminated, and· indeed in some beds the 

layers of rock a few millimeters thick that lie between 

laminae containing the larvae have distinct varves. 

For these reasons the conclusion that the larvae of 

Lithohypoderma spent at least a part of their larval 

life on the lake bottom in decaying organic ooze ~eems 

inesco.pable~ As the writer noted in an earlier paper,63 

this hypothesis is materially strengtpened by the 

intimate association of Lithohypoderma with the larvae 

of .Stratiomyidae (Odontomyia sp.), Syrphidae, Myce:-

tophilidae, Tabanidae, and Chironomidae, many of 

whose living species are aquatic and live among decay- . 

ing vegetable matter. The syrphid ·larvae o.re particularly noteworthy, for they are saprophytic. 

· The taxonomic significance of the larval habitat of 

Lithohypoderma must be left to students of Diptera. 

n Cockerell, T. D. A., op. cit., p. 92. 

. as Bradley, W. H., A contribution to the origin of the Green River formation: 

Am. Assoc. Petroleum Geologists Bull., vol. 9, p. 261, 1925. · 

INTERPRETATION AND SIGlm'ICAllCB QF' Till 

XICROPOSSILS 

The fossil bacteria in the oil shale · of.· the <keen 

River formation are too doubtful to be of any value. 

The · fungi, however, . su.gg~st an interpretation of 

certain phases in the formation of oil shale. The 

abundance of fungi, particularly the delica.te filaments, 

indicates that they probably grew 'in place, and· the 

fact that some of them seem to be .forms that lived 

upon decaying plants suggests .that ·they grew on. the 

surface of the organic ooze while it was exposed to 

the air for brief periods of time. . Renault 54 observed 

that woody peats which had rema~ for a short 

tin;te above the water table contained a great &bUlldance of fungus filaments and spores, •hereas those 

which had been continuously submerged oontained 

relatively few fungi. It seems logical·~ assmne th-at 

the relation between the number of fungi and exposure 

to air might be similar also in deposits of orgamc ooze. 

Yet it should be emphasized that the evidence wlrieh 

the fungi bring to the interpretation of the origin of. 

the oil shale is tenuous. Moreover, at least some of 

the fungi (Saprolegniae) were probably aquatic. 

. Blue-green algae apparently donnnated the algal flora 

of the ancient Green River lakes. In general algae of 

this class find their optimum temperature several degrees higher than that of the other algae~ Furthermore, 

a great many of them flourish in stagnant and·~ore or 

lt~ss foul waters. Hence they o.re peculiarly adapted to 

live in shallow stagnant pools. Indeed, they are· ~o · · 

characteristic of the shallow old-age lakes of Denmark 

that Wesenberg-Lund 66 calls that stage of the ·life 

histories of lakes the "cyanophyoean <Stage." 

u Renault, B., Sur quelques mieroorganismes.des combustibles follsiles: Soo. 

ind. min. St.-Etf.enne·:Bwl., 3d ser., vol. 13, p. 002, 1899. · 

n WeseD.berg-Lund, C., cited by Lenz, F., Bchlammschiehtung in Binnenseen: 

Naturwiss. Wocbenscbr., vol. 18, p. 330.1~21. 
r 

>. 

"'"· 

52 ORIGIN . AND MICROFOSSILS OF OIL SHALE OF GREEN RIVER FQBMATION 

· The absence of diatoms from the oil shale of the Green 

River formation is astonishing, but its significance is 

ambiguous. It may be that fresh-water diatoms do 

not go that far back in geologic time, or it may be that 

the lakes were too saline for them. According to Dr. 

Albert Mann,66 of the Carnegie Institution of Washington, who· studied the diatoms from a core of Lake 

Lahontan beds, the diatoms became depauperate and 

finally disappeared at one or more stages in the lake's 

history when it was low ·and consequently saline. It 

seems doubtful, therefore, if diatoms ever lived ln the 

ancient Green River lakes, for none of their tests have 

been found even in the limy and clayey beds associated 

with the oil shale, where there is little likelihood that 

the products of putrefaction of the organic matter 

have dissolved them all, as might perhaps have happened in ·the organic oozes. · 

. The green algae suggest stages of the lake when the 

water was less saline and better aerated, but they do 

not provide conclusive evidence, for their range of 

habitats is too great. 

The unclassified algae are particularly interesting for 

their exotic forms, but they contribute little else. 

Six of the algae described here seem from their structure and by comparison with similar-shaped living 

algae to have been plankton organisms. Eight others 

seem to have been attached to substrata and must 

therefore have lived either on the bottom or upon 

other plants. One, EoglobeUa longipes, may have been 

either a free-living or a bottom-dwelling form. 

The great abundance of the remains of rather large 

fly larvae (Oestridae, Stratiomyidae, Syrphidae, Mycetophilidae, and Tabanidae) in the oil shale indicates 

a. probable moderate depth of water. Certain living 

members of these families (Odontomyia)frequent chiefly 

the very shallow water close to the shores of ponds and 

lakes. The living aquatic members of the Tabanidae 

also generally frequent shallow pools. The larvae of 

Syrphidae and Mycetophilidae live in decaying vegetable debris, and as the other larvae (Lithohypoderma) are 

associated with all . these forms and occur in rock of 

exactly the same sorts they probably were accustomed 

to the same habitat, despite the utterly different life 

habits of their nearest living relatives (Hypoderma). 

The midge-fly larvae (Chironomidae), however, have 

no significance whatever as depth indicators, for their 

living representatives abound alike in the shallowest 

pools and. at the bottoms of really deep lakes. The 

parts of minute adult insects are of little use in inter-

·pretation, for they might have fallen into a water body 

of any sort. Their fragmentary condition and the loss 

of all but the most strongly chitinized parts seem to 

indicate rather distinctly that they did not get stuck 

on exposed mud flats, like so many of the larger adult 

insects found in the Iiiarlstone. Forms caught in that 

10 Oral communication, 1922. 

way and covered quickly are eharacterized by the perfection of their preservation. 

· Pollens and spores were carried in bY wind an:d 80· ate 

erratically distributed through the· deposit. -··Locally 

they are veri plentiful. The shriv-eled condition ·of 

certain groups of pollen suggests that they fell upon' i. 

dried mud flat. Their possible relation to· known: types 

of plants shed a little additional light on the composition of the flora of the adjacent region. When the 

pollens and spores are bet~r known they undoubtedly 

can add much information about the land flora of that 

region in the Eocene epoch. 

STRUCTURELESS ORGANIC MATTER 

The material here termed "structureless ,. is so 

designated to differentiate it from that with definite 

outline called here for the sake of brevity the figured 

organic material. It appears perfectly homogeneous, 

even at magnifications of 1,500 diameters, unless the 

light is reduced and slightly oblique, and then it appears 

somewhat floc.culent. Its color in very thin edges of 

sections ranges from straw color to a faint reddishorange color, but in slices the thickness of ordinary thiri. 

sections most of it appears broWnish or reddish orange. 

Trager 57 pointed out that there· were· two kinds of 

structureless organic matter, one optically active and 

the other not. He gave none of the optical properties; 

however. According to the writer's observations most 

of the structureless material is apparently ·isotropic. 

In a few sections two sharply differentiated sorts of 

optically active organic material were· found. One is 

a clear, brilliant cadmium .. yellow·. This material hi\s 

an index of refraction about equal to 1.61. It .is not 

pleochroic but has sharply defined parallel extinction· 

and birefringence a little higher than quartz. It is 

uniaxial negative. The structureless material of the 

other kind is clear. reddish orange-colored and very 

slightly pleochroic, with the absorption greater in the 

plane normal to the bedding. Its index of refraction is 

a little less than 1.61; the extinction is shadowy and the 

birefringence feeble. The interference figure is vague 

but appears to be uniaxial or perhaps biaxial, with the 

. value of 2V very small. 

Davis 58 said that "the structureless material.prob~ 

ably originated in a collection. of plant debris which has . 

by decomposition and the activities of bacteria and· 

other microscopic organisms passed into a jellylike 

phase such as is to be found in certain kinds of modem 

peat deposits." 

The evidence appears conclusive that the structure-· 

less material which makes up by far the greater part 

of the total organic matter of the Green River oil shale 

was derived from the partial putrefaction· of aquatic 

67 Trager, E. A., Kerogen and its relation to the origin of oil: Am. Assoc. Petroleum 

Geologists Bull., vol. 8, p. 309, 1924. · 

as Davis, C. A., notes in Winchester, D. E., Oil shale in northwestern Colorado and 

adjacent areas: U.S. Geol. Survey Bull. 641, p. 165, 1916. 
STB\JOTUBELESS ORGANIC MATTBR . ·., '' •. 

organisms that grew in the lakes. The organic matter 

is most abundant in the center . of th:e lake basin and 

diminishes in all directions toward ~he shore phases, 

from which it is practically absent.: Aquatic micrporganisins dominate the micro flora; and microfauna 

of the oil shale. Fragments of the i tissues of higher 

land plants are exceedingly rare, though their spores 

and pollens are not uncommon. And finally, as the 

writer has pointed out in a previous paper," there is a 

remarkably close parallelism between the oil shale and 

recent lacustrine organic oozes or, sapropels. This 

analogy with recent sapropel has l~tely been greatly 

strengthened by the results of a brief study of an algal 

ooze from It small lake nea.r Reddick, Marion County, 

Fla. Thisoozeconsistachiefiyoffragmentary and complete blue-green algae belonging chiefly to the genera 

Gloethece, Aphanotkect, Arlhrospira1 .Microcystis, Phormidium, and Ohroococcus. It also contains bacteria, 

· diatoms, fungi, sponge1spicules, and pollens, as well as 

a fairly large proportion of structureless organic jelly. 

D. Stuart Mossom,60 assistant State geologist of 

Florida, collected some of this material more than 

three·years ago and permitted it to dry out very slowly 

in a warm place. It contracted greatly and dried 

down to a dense grayish-black subst$.nce fully as hard 

. as oil shale, which it r~sembles in every way s~ve that 

it is more brittle. Moteover, it is very significant that 

in the drying no perceptible odor was given off, showing 

that decomposition had been very greatly retarded, 

if it had not ·entirely ceased. Thin sections of the 

dried material, pieces of which Mr. Mossom was kind 

enoUgh to supply, are identical in most respects with 

oil sh~le. Even the structureless organic material has 

the same appearance and nearly the same optical 

properties as the structureless matter in some sections 

of the Green River oilshale. Furthermore, the hardened Florida sapropel will burn with a smoky flame. 

The smoke, however, smells quite unlike that of burning oil shale. Evidently the two materials are not 

precisely alike, yet the similarities are very remarkable 

and· suggestive. Upon· distillation this dried sapro.pel 

yields about 16 gallons of tarry oil to the ton. 

The predominance of structureless organic matter 

in the oil shale of the Green River formation is in 

itseH fair testimony of an active microbian decomposition. The partly decomposed organisms and particularly the large quantities of syngenetic pyrite or 

marcasite afford strong evidence of the extensive 

putrefaction of organic matter. 

Mechanical and chemical actions, such as the mastication and digestioJil of the original material by 

bottom-living organisins, were probably also important factors in the disintegration of the organic 

matter. Saprophytic organisms, too, assisted in the 

decomposition. 

11 Bradley, W. H., A contributwn to the origin of the Green River formation and 

its oil shale: Am. Assoc. Petroleum. Geologists Bull., vol. 9, pp. 252-258, 1925. 

tt Oral communication, November, 1921:J. 

In disc~ the wcrobian· doootnposition· of s&propelic matte~, White•1 says: 

It appears that plant protoplasm, and in most cues tb:e 

gelatinm,ts and mucous substances,· which are less resistant· to 

bacterial decomposition,·· quickly disintegrate, and later :the 

cellulosic matter of the original cell membranes, whereas . ~l}.t 

waxy and waxy fat or ''higher fat" products, the resinou~ 

exines, and the chitins are la.St to be lost. 

White also believes 82 that the ~nials in the ancient 

lakes contributed only indirectly to theorganicdeposits. 

The soft parts of animals are very rare in the oil shale. 

He says, however: 

The products of the total. biochemical decomposition of the 

animal tissue may form part of the colloidal groundmass solu: 

tion, and the decomposition derivatives, mingling with those 

of the plants, may contribute new compounds and impart new 

qualities to the humic aggregate, thus making the derivative 

solution more distinctly bituminous. · , 

To judge by analogy with the life societies in·modern 

· lakes, the production of zooplanktoRwas very probably 

also large in the Green River lakes. ·Insect larvae were 

surely plentiful in some of the o~ze beds, and probably 

nematodes were also. It seems reasonable that these 

organisms should have contributed some of the "fatty" 

constituents in · the sapropel. ·Naumann 63 demonstrated that the Entomostraca synthesize fats. and 

thus may . .account for a considerable fat production 

in lakes where they abound. 

The preservation of so much organic matter must 

have been determined by a copious supply of the 

organisms, an effective check upon the microbian 

activity, and the absence of strongly oxidizing conditions. That the rate of supply of organisms far 

exceeded the rate of decomposition is obvious,- and 

from that it follows that the production of organisms 

within the lakes was large. The absence of strongly 

oxidizing conditions is amply proved by the quantity 

of syngenetic iron sulphide disseminated, through the 

oil shale. But the means by which the nricrobian 

decay was held in check ~re less certain. White" 

suggests that toxic humic solutions derived from the 

decomposition of the organic material impede the 

putrefactive processes and so conserve the material. 

Other factors, however, may have been·equslly effective. As the organisms decayed the material clearly 

passed over into a gel, which might have adsorbed 

large quantities of water and-held it so fumly that it 

was not available for hacteria. ·Hence the organic 

ooze might have become physiologically dry as soon 

as it gelatinized. It would then have been entirely 

unfavorable for bacteria. Potonie 66 called attention 

6t White, David, The carbonaceous deposits, in Twenhofel. W. H., Treatise on 

sedimentation, p. 291, 1926. 

62 Idem, p. 293. 

61 Naumann, Einar, Einige Gesichtspunkte betreffs der Fettproduktlon des 

Siisswasserzooplanktons: Archlv Hydrobiologie und Planktonkunde, vol. 13, pp. 

307-312, 1922. ' . . 

64 White, DaVid, The carbonaceous sediments, in Twenhofel, W. H., Treatise 

on sedimentation, pp. 289-294, 1926. 

as Potonie, H., Die rezenten Kaustobiolithe und il:are · Laaerstitten: K. preW!I 

geol. Landesanstalt Abh., new ser., Heft 55, Band 1, p. 13, 1908. · 
ORIGIN' AND MICROI'OSSIIS OF OIL -SH:Arl.im ··()!' ·Gft8BN. RIVER FORl\I.ATION 

to·. the·· stability· ·of sapropel after · the . first · stage· of 

putrefaction and said that· he had kept it in an oozy 

or. slimy condition in poorly corked bottles for years 

without detecting any odor of decomposition. ·This 

accords with Mossom's ·observation on the sapropel 

from Florida and with the writer's eXperience with 

some sapropel collected by C. A. DaVis nearly 18 years 

ago. Biochemical studies of this material are much 

to be desired, and the results would probably elucidate 

m:any puzzling questions regarding the preservation 

of sapropelic material. 

The asepticity of the gelatinous organic ·ooze explains 

the remarkable preservation of delicate organisms 

like algae and Protozoa. When these were mixed into 

the gel accidentally they were apparently mummified 

and, having escaped the biochemical stage were subsequently changed only by a slow process of bituminiza.tion, which evidently affected both the gelatinous 

organic ooze and its entombed microorganisms, spores, 

pollens, and fragments of animal and plant tissue. 

Spate 66 gave a very concise definition of bituminization, which may be freely translated as fo-llows: 

Bituminization as well as coalification leads to an enrichment 

in carbon. But in coalification carbon is enriched at the expense of all the other components together, whereas in bituminization both carbon and hyrogen are increased in proportion to 

the other components, oxygen, nitrogen, and sulphur. 

PHASES OF UINTA LAKE DURING THE GREEN RIVER 

EPOCH 

Uinta Lake, the great Eocene lake in which the 

Green River formation of Utah and Colorado accumulated, may be pictured at its earliest stage as a very 

broad sheet of water flooding a large fluviatile plain, 

bounded by mountains or high hills except on the 

south, where the country must have been fairly low. 

This plain was built up of clay, silt, and sand brought 

down by streams from the surrounding mountains, 

and as the alluvial material is predominantly mudstone 

the basinward slopes must have been rather gentle. 

The mudstone and stream-channel sandstone beds 

make up the Wasatch formation and in the greater 

part of the basin are comparable to the youngest 

flood-plain deposits in Sacramento Valley, California, 

between Butte City and the Montezuma Hills, which · 

according to Bryan 67 consist chiefly of clay and silt with 

more or less braided stream-channel deposits of coarser 

sand and gravel. The gradient of the Sacramento 

River through this area is a little less than 1 foot to 

the mile. 

If this gradient is assumed for the basin floor over 

which Uinta Lake first spread and if it is also assumed 

that the water was not more than 10. or 15 feet deep 

• Spate, Friedrich, Die Bituminierung, ein Beitrag zur Chemie 'der Faulschlamm.gesteine (lnaug. Diss., Friedrich-Wilhelms-Univ., Berlin), pp. 44-45, 1907; 

cited by Potoni6, H., op. cit., p. 20, 1908. 

.., Bryan, Kirk, Geology and ground-water resouroos of Sacramento Valley, Califor_nta: U.S. Geol. Survey Water-Supply Paper 495, pp, 7, 10, 30, pl. 4,1923. 

uear· the shores, where the· algae. reefs 0~~if~ · 

the deepest }latta of the lake-. net¢ the ~~tet{ifr1t)if, · basin may have been as much as· 5o· or ,6Q~f8Mt,i!~~ 

But other things being equal,l laclistrine isedhn~W .... 

tion would probably soon hate lessened·· tihi&~\'f•¥ef 

on the lake floor, so that while the greater·~ .'Qf . 

the basal member was being formed the lake bobtolli · · 

was nearlY. level. · On the other hand, the la.ke may . 

have started as small ponds and ·backwatel's along 

the stream courses in the alluvial plain ana eXpanded 

very gradually, filling the basin and leveling up the 

plain as it grew, until finally a ~ontinuous lake,'Pfeaa 

over the entire plain from m01j1ntain flank to mou.n;.. 

tain flank. I • 

In this great shallow lake algae 6ouri$b.ed.· ud 

built bedlike reefs that expanded broadly ove:r ·'tlh6 . smooth lake floor, Fish, mollusks,· crustaeeanB)·-aad 

aquatic .insect larvae were also plentiful in the lake, 

and turtles (Baptemys sp. and Echmatemy& . sp;), 

crocodiles, birds, and small camels, as well as· m~de · 

of winged insects, frequented the shores. Alo;ag 

some shores there were marginal swamps, ·.whiob. 

persisted for a considerable time and . whose . fol'lll!er 

positions are revealed now by thin beds of ooal-and 

carbonaceous mudstone. But 'this lake, despite its' 

enormous area and slight depth, must have been a 

fairly stable water body with an outlet, for the writer. 

estimates 68 that some of the thicker algae reefs 

required at least 355 years to form. During that 

time only slight changes in water level, r-ate :f.nd· 

manner of circulation, and _rate of sedinumtation 

could have occurred. Such changes would register 

in the growth layers of the reef. A considerably·· 

longer period when the ·lake overflowed is indiCated · 

by the composite reef near the divide between Douglas 

and Salt Creeks, Colo., which is 18 feet thick. Nevertheless it is possible that between these long periods 

of apparent stability in the early stages of Uinta 

Lake the overflow was intermittent. The prevalence 

of mud-cracked bedding planes and mud curls .in' 

some parts of the ·basal member supports this· 

hypothesis. Yet complete desiccation probably' was 

·not even approached. At this stage Uinta Lake 

may have been entirely fresh, or it may have beeii 

comparable in relative permanence, depth, and content 

of dissolved salts to Goose Lake, Oreg., which con ... 

tains about 1,000 parts per million of dissolved. salt&~ 

rarely overflows, and although very shallow has never 

been known to dry up.611 Yet much more convincingevidence that the lake had an outlet is found in the 

absence of salt crystal molds from· the Dougla.s·Creek 

or basal member of the Green· River formation. · 

The climate of the Green River epoch seems to have 

.exerted a marked influence upon the fluctuations of 

es Bradley, W. H., Algae reefs and oolites of the Green River formaUOJt: V~ W •. 

Geol. Survey Prof. Paper 154;p. 220, 1929. ·. 

ee Waring, G. A., Geology and water resources of a portion of soutb-centr&l~: 

U.s. Geol. Survey Water-Supply Paper 220, pp. 12,-38, 1908. 
tJinta. ,Uk:e. ·: In another. re.p0rt· 7P the· wri~r has·· attt\mpted , r<Juigh quantitative estimates ·of sel'eral 

faetors oftllis climate and cqncluded from the :relativ-e 

area&· of Gositite Lake (the ancient Green River Lake 

in Wyommg) and its hydrographic basin and from the 

fossil flora that the climate was characterized by cool, 

moist·· Winters and relatively long, warm summexs. 

Presumably the ·temperatures fluctuated rather widely 

from a mean annual temperature that was of the order 

o{l 66° F. The rainfall also appears to have varied 

With the seasons and-probably departed rather widely 

from a mean annual precipitation between 30· and 43 

inches, The evaporation from the lake surface seems 

tO' have nearly balanced the supply of water from rain 

and the streams, for the lake level fluctuated repeatedly 

and apparently between wide limits. The seasonal distribution of the precipitation probably played a large 

part in determining this characteristic of the ancient 

lake. If, as the writer supposes, the greater part of . 

the rainfall came during the winter, then the relatively 

long, hot summer would have been particularly favorable to evaporation. Thus at certain stages Uinta 

Lake_ may have overflowed during part of each wet 

season and then have contracted more or less during the 

dry seagon, so that, as the lake was rather shallow, large 

parts of. the bottom were ·repeatedly left exposed. 

But at one st~ge the lake J\P)Parently did not overflow 

for a long time. During that stage the water beQame 

so saline that at times of ex~ptionally low levels salts 

crystallized out on the mud-cracked fiats or below the 

surface of the wet mud. At times the deposition of 

salt was apparently cyclic. In the saline zone of the 

Green River formation thus produced the most common crystal cavities are those which were formed by 

glauberite(?) and anhydrite(?). 

But between these stages characterized by extreme 

low lake levels occurred periods in which the lake seems 

to. have maintained a persistently rather high level. 

The preservation of the varves in certain rocks of the 

Green River formation 71 appears to indicate that while 

they were forming the lak~ was so. deep that the 

water was thermally stratified. While so stratified the 

water at· the botto;m. of ~ lake is virtually stagnant. 

Only the water in the warm uppermost layer circulates 

and transports material for ·sedimentation. The 

supply of oxygen is soon exhausted from the stagnant 

bottom water, and so because of the decaying organic 

matter the bottom ooze becomes a strongly reducing 

medium that is distinctly unfavorable for most bottomdwelling anunals. The original ooze of the varv0d rocks 

could not have supported an active population of 

worms, larvae, crustaceans and the like, for these organisms ~ould surely have destroyed the delicate _lamination. Moreover, the abundance of finely granular 

te Bradley, W. H., The varves and climate of the Green River epoch: U.S. GeoL 

.Survey Prof. Paper 158, pp. 93-96. 1929. 

n Idem, pp. 101-103 • 

• ! 

~_.r:;" • ' ~~ '''. ---:1: • '"r__, ·~ • -~-•: 

J ,, .'~; '' *1c~'ff;~;f~··.·· · "''-(.: ': ~~-· 

d~\.;;1:3 

primary pyrite alsosuppo!W the kypothesis tlwt:.~::~.;;:;, varved depoeiteut.ectmlula.ted under reducing e~~ · 'L.::. 

such as prev-ail generally ~ the stagn8llt hypo~t 

or lower stratum, of ln.()dem. lakes that are th--. ·

stratified. Now, as not only marlstone but also·OOdsof 

exceptionally rich oil shale contain varves=arid an ab'ltP 

dance of microgranular pyrite the two kinds- of roelt> 

must have accumulated under essentieJ.Iy;these ·same · ' 

conditions of quiescence and stagnation. : : Th~'eo~ 

tions seem to iniply that the water may haV&heeil' 'ilJ:or 

100 feet deep.72 The regularity of most of the oil-shale 

beds and their remarkable persistence over many square 

miles in the central part of the basin make-it ~em likely 

that the greater part of the high-grade· oil sh~e. in th~ 

Green River formation was formed in ·the relatively 

cool, stagnant hypolimnion of a lake tha~ Wf.tS deep 

enough for a thermal stratification ol its water to pe:r .. 

sist for long periods of time. 

On the other hand, it seems quite clear that some of 

the lenticular and irregular beds of oil shale, especially 

those that are mud cracked and brecciated and those 

that are full of salt-crystal cavities; must have been 

formed in very shallow water. These shallow-water 

bodies seem to have been residual pools or ponds left 

in depressions of the lake bottom at ·sttlges of extreme 

low !evel. They probably contained in solution an 

ampLe supply of nitrates accumulated from the decay 

of organic matter during the shrinkage of the parent 

lake. Dissolved salts must also have· beeome concentrated in them. In short, they must have been 

exceedingly rich in the foodstuffs ·necessary to the 

production of vast numbers of organisms. Ward 73 

makes the following generalization about the life in 

lakes and ponds: · 

Purely tempora~y water bodies, such as pools that form· in 

hollows after a heavy rain or in a wet season, develop .little if 

any life. Such places on poor soil are most barren of afi; t4e 

aquatic life increases with the fertility of the soil, the age of the 

water body, and the consequent accumulation of organic d~bris. 

Residual ponds, water bodies in which the drying out is more 

gradual and often incomplete and in which the central area 

may be protected from complete desiccation by vegetation or · 

proximity to the general water level, afford conditions at the 

opposite extreme. 

Conditions ·were evidently near the optimum in . 

these shallow residual lakes of Green River time, for 

they had a tremendous production -of aquatic organisms. In fact, the abundance of the organisms a.na 

consequently the large quantity of decaying organicmatter must have given rise to strongly reducing 

conditions in .these pools, comparable to those that 

prevailed in the stagnant hypolimnion when .the water 

was deeper. At certain stages these. pools perhaps 

approached playa conditions, though they could have 

been dry ·f~r only rel~tively very short intervals. 

12 Idem, p. 103. 

78 Ward, H. B., and Wqipple, G. C., Fresh~water bioJogy, p~ 3, 1918. 
ORIGIN AND IIICB0l!'OI!IIIL9 OF 0U. ~ ".(lir. GllUif • ~ .. JfeJUu.TIOllf 

0 

a. . ;\~~t~ .· . ""' . . . . .. j' •. (' 

After· the deposition of most of the oil shale the lake-. 

seems to have reverted nearly io the conditions that 

prevailed duriD.ft ~~ earlier stages, when the marlstone 

and low-grade J*. shale of the basal member were 

formed. l{owever, the . central parts may have been 

even shallower than at first, as is suggested by the 

occurrence far eut in the basin of mud cracks and fossil 

· leaves and iulects. During this last stage the water 

level also fluctuated and the bottom was repeatedly 

exposed, so that the large mud flats were dried and 

and cmcked. But sometimes apparently the watm 

was withdrawn only for shor.t intervals~ for many 

bedding planes are uncra.cked, and yet they bear adult 

insects which, it seetns, must have fallen on a wet mud 

flat, where t1iey stuck until covered. Perhaps such 

temporary withdrawals were due to a steady wind that 

piled up the water on the opposite shore. Similar 

phenomena have been observed repeatedly in the 

't ·~ 

.... ,. 

shallow lakes of the West .. For: examp)e;itW~~-:~,\: 

repo:rts that the north end· of the Aben·Lt.ke _·»-iA~ .· r··~-:r 

so nearly level that a strong south. Wj~ i~~ , , .t~:~_; 

water back nearly 2 miles. Leaves,· fiOWC"S,; ;~\~?· ·'' 

and seeds were also found 011 theae bedd.U.lig ,-..; :, ;. · 

. Locally, too, there are many small fish able~ 

· ~ppa.rently indicating that the fish were straaded~r- -~. · .a 

. · A sudden but not large diastrophic :change· rejwt,. 

vena ted the streams in the vicil:lity of Uinta Lake •SO 

that- they carried a great quantity of ~~, to, . 

coarse grained sand far out into .the.basin andlQrmeci . 

a thick layer over the lake beds. Thus the aepos\~Jt :. ·,. 

of the basal sandstone of the Bridger .formatie~ 

brought the lacustrine history of the Green. Bivef"'"': 

epoch to a close. · ~ , ;;·; :·· -

7t Waring, G. A., Geology and water resources of a portion ofaout~ ·~ ~ 

U. B. Geol. Survey Water-Supply Paper %10. p. 38, 1908. : ':;"~;;, 

-.' :=;. 
A 

. _ .- __ . "" . Page 

.;;~ ==;~~;~d----~~~~~~~~~~~~~~~~~~:~::~::~:~~~~~~~=~~~~~:::::::::: v-v! 

, ·~ ·£A]pe of the on shale------------:------------------------------ 40-4li, pls. 19, 21,22 

\ e~~:~~:~~~:~~:=~~~~~~~~~~~~~~~~~~~~~~: j ' '~08----------------------------------------- --------------------- 40, pl. 20 

B 

snbtllis •• _ ------------------------------------------------------ 40, pl. 19 Ja of the oil shale ________________________________________________ .• 40, pl. 19 

ark, transverse section of·---------------------------------------------- 46, pl. 24 

ula sp., pollen of •• ·------------------------------------------------------ 48 

=~-;~-ii~.=d~---~:::::::::::::::::::::::::~:~::::::::::::::::_~~ pl.!: 

racbJ'SporiUDl SP------------------------------------------------------- 40, pl. 20 

Brecctaa, oil-shale, occurrence and character oL----------------------------- 28 

formation, contact of, with Green River formation in valley of Evacuation Creek·------------------------------------------.----- pl. 12 

~ of __________ ------------------------------------------------------. 21 lower sandy part of, contact of, with Green River formation. ____________ pl. 12 

· ooaorrence and character oL--------------------------------------------- 19-22 

r ¥uvu•r ...... -----------·----------·--·---·-··-•• ------------.-----••• -------- 45-46 

c 

Calcite, occurrence and character of, in oil-shale beds----------------------- 29-30 

calcite pseudomorphs of a salt :ftlling cracks in organic marlstone ____________ pl. 10 

Carum carvi, pollen or________________________________________________________ 47 

Cathedral Creek, columnar section of Green River formation on ••• ·---------- pl. 8 

Caulerp&. _______________ -----· --------------------- ___ ------- __ • ---------- 44 

Cbaetophora •• ---~------- ---· ________ ---------------- _ ---------·------------ 44 

CbiroDomid larvae·-·---------------------------------------------------- 50, pl. 28 

ChJronomus deplitus Scudder----------------------------------------------- 50 

patens Scudder •• _____ ------- _______ ------------------------------------- 50 

septus Scudder------------------ ___ .------ ____ ---------·----------------- 50 

Chroococcus? sp. cf. C. dispersns (Von Keissler) Lemmerman ________ 41-42, pl. 19 

sp. rq[IO. westii (W. West) P. Boye·-------~------------------------- 41, pl. 19 

Clj; .. ~por:ium sp __ • ----.-----· ------------~--------------------··-------- 40, pl. 20 

occurrence and character of, in oil-shale beds-----------·--- 31-32 

of ••• ----- ___ • ____ ---_____ --------------------__________ 6 

Colo., typical clitrs made by Green River formation on_________ pl. 2 

D. A., quoted-----------------------·-------------~----------- 51 

sp. cf. C. verrueosum Reinsch ______________________________ 43, pl. 21 

"---••-·· •- oD-shale beds, occurrence o'-··------------------------------- 37 

in on shale, occurrence and character of __________________ 26-28 

pollen of ••• ------------------------ ____ ------- ____ · ______ ----____ 48 

----------------------------------------------------------------- 40 SP----------------------------------------------------------- 42, pl. 19 

sp. cr. c. endophyticum Crow--------------··--------·-------------- 42, pl. 21 

D 

1. D., quoted •.• ---------------------------------------------"'-------- 6 

C. A., quoted.·------·----------------------------------------_______ 62 

Creek, Colo., columnar section of Green River formation on__ •• pl. 8 

J¥D~tlm•••••••••••••••·•••••·••••••••••••••••••••••·••••••••••••••••• • 40, pl. 20 

compaction of sedimentary beds, views showing _____________ pis. 10,12 

Bradley, n. SP------------~-------------- -------------- 48, pl. 25 

: py1riformis PertY-----------------------------------------______ ----_ ----- 48 

oooun1ln41l8 md character of, in oil-shale beds ______________________ 29-30 

member of GJ188D River formation, occurrence and character of. 1-10 

~neme-UlntaiD County line, seotion of Gl1!en River formation at __________ 15-16 

E 

.· 

c';. ...- • ... 

~-: ~ .. -

. . :. "'-¥-• ~:·; . 

Fairohnd, J. G., chemical analyses bY--~----------·------.;-~--~-~-: .. ~ ... L~.:: "1";· Fall!8 bedding in muddy sandstone of a delta facies~-----------------·•---~-- pl. 0 

Faults ill bed of oil shale--··----------------------------·-····---------~----- pl. IS 

Fauna of the oil shale ••••• _.---------------'!'~---------_r.---·-----=--~---.:.:. •. :.~. 41-61' 

Fern spores •• -------------------.,----------------------..-~-.--~-"'·--J..- ~pl. 21 . Field wor~ character of-------·---·----~--------·-·-···---=---:··------~---- 3 

Flora of the oil shale •••• -----------------------~-----~·---"'------•~:. •••• .:~ 88.4&-48 

Fly larvae, orpilfc marlston$ covered with-------.---~----------.-·---· .. ··- pl._t 

Folding, age 'of..·-----------------------------------=~---------------------- G 

Fungi of ~oil shale---------------------------------.-------:·"----.· ·4.0, pls,:to; 29 

G 

Garden Gulch member of Green River formatiotl, broken c1ftfa formed by __ pl. f 

ocCIII'l'ence and character of·------------------------·--·--·--·------~---· ·.10-11 

Gate Canyalll secdon of Green Ri'v:er formation in--------------------------- 18-17 

Geologic map showing. distribution of Green River·fonnation in Colorado 

aad Utah--------------------------------------·---------~------- pl. 1 

Geologic W41k, previoUS.-----··------------------···-----------------.:. ••• ,... W Green River epoob., geologic and biologic record of ____ _,______________________ 1 

phases of UintA Lake during _______ .., ___________________________________ .• 64-liG 

Green River formation, age of.---------------· --··-· -·-------------------·- t · columnar sect1ems of.--.----------------------------------------· 15, pis. 1, 8, 11 

contact of. with Bridger formation in valley of Evacuation Creek •••••••• pl. l2 

correlatiGta of facies and zones of, in Uixita and Pioeance Creek Basins.... 11 

delta and ahere facies oL •••••••••. -------------··--------------------- 14.15-16 

geDeral features of._------------·-------------------------------------· .. - 9 

geologic map showing distribution of, in Colorado and Utah----------·-- pl. 1 

lithology of. ____ ----···---~----------------------------·--------·--.--·-· 9-11 

microfossils of oil shale oL------------------------------------·--·-- pia. li'-28 

on yields of oil-shale beds in--------------------------------------------- pl. 13 

'stratigraphic reJations of subdivisions of, in Colorado and Utah.......... pl. 3 

Gymnospermae ••• -------------------------------------------------------··· 41 

H 

HapalQIIiphon aureus W. and G. B. West------------------------------------ 42 

ftemosus Bom. __ ~--- -------------·----------·-------------------------- 42. 

sp. cf. H. confervaceus Borzi •• ------------··--·-------···---··------ 42, pl. 21 

Haplographium •••••••• -------------------· -----------------------------. e, pl. 20 

Hells Hole Canyon, columnar section of Green River formation in-------- -· pl. 8 

Helminth•porium SP------------··----------------------------------- • 40, pt. !10 

Hendersonia SP---------------------------------------------------------- •• pl. 20 

.dorse Bench sandstone member of Green River formation, OCCW'l'eDce ad 

cllaracter of. •••• _____ --·-----------------------·------·--·----.... 16 

Hypoderma.------------------------------·-------------------~--------. lie. 61, 52 

I 

Indian Canyon, composite columnar section of Green River formation in---- pl. 11 

section of Green River formation in-----·---------------------------·-- 17-llJo 

Insects, fl81Dlents of fossiL----------------------------------- 49-51, pis. 1~, !rl, 28 

L 

Laboratory work, character of .. ------------------------------------··------- 3-4 

Lamination in oil shale, character of----------------------------------------- 26 

Lenticular beda in oil shale and their significance.--·------------------------ 20-26 

Lepocincles teres Schmitz._------------------------------------------------- 41 

Leptosphaeria ••. _______ ------- _____ ------------------------------------- 48, pl. 1& 

Lewis, J. V., quoted.-----------------------·-----·------------------·------- 7 

Liriodendron, sp., pollen oL----------------------------------------·------- . 47 

Litbohypodermasp ________ ~--------------------------------------- M-51, 52, pl. 28 

Lithologic tenns used .. _---------------------------------------------------- 6-8 

Location and extent of area------------·-------------------,-------------------- 1 

Loop bedding in oil shale, ocCUirence and character of--.-t-----------------~- 2& i 

M 

Macrosporium sp __________ ---------------------------------------------- 40, pl. ·2& 

Map, geologic, showing distribution of Green River formation in Colorado 

and Utah--------------~--------------;------------:-------------- pl. 1 

Marl, definition of. •• _-_----------------------------------------------------- stellate hairs of _________________ --------------------

... ----------...... ,. ... ...; ______ .,. ------------------------

6-'T 

4T. 

& 

----------------------------------------------------- . 

57 

a 

3.:.~~i-· 

:w :1/f 

···~ 

--~ -'\~ 

. )~it~ 
Pqe 

'~(W~~~:::::::::::::::::::::::::::::::::::::::::: ~. ~of oU ~of ·Gleim R~ f~, IDuatrattonsGf ···------:PlJ.liHII 

' ;:::::..~':.':~-~:::::::::::::::::::::::::::::::::::::::: !~! 

E

. sp. or. i4 ... ~ (W.nte) .Leterheim------------------- 43, pi. 21 

. . 

017 of\M oD-8bale beds----·---------"·---------------------------~-- 29--37 

' Maud cirek, aeetion of Oreen River forma;ion on •• -------------···· tS8 

::• · view-- vaDe'J' oL-------------------------------~--------------:.... pl. 9 

· lfite, fossil/bel~ to ObeJytidae ••••. -----------------------.,.-------- 49, pl. 2G 

·x0880Dl, n; s:, wodt'of.---------------------------------------------------- 53 Jitoas apores_ ____________________ .,. ________________________________ 45-46, pls. 23, 24 

·1,_~ In oilslt.ale, -900lll'.NBC8 ani! character of------------------------- 28-29 

MUsca MndstoDe, ascarides definition<~'------------------------------·---------------------- Scudder. ____ .:_______________________________________________ 50 6 

XJ\l'O$ph118rella ••••••••••••••••••••••••••••••••.•••••••••• ~---------·-~-- 40, pl. 20 

I(Jriqpbyllum spicatum, pollen of--------------------------------··-------- 48 . . 0 

Qd.obtom:vta sp ___ -----------~---------- ------------------------------ 50, 52, pl. 28 

. Qatbala, appearance of, in hand specimens •• --------------------------------- 22-23 

'Q84ding in------------------------------------------------ M-29, pis. 14, 16, 17 

~In------------------------------------------------------------ pis. 15, 16 

ehemieal analyses of mineral portiGn of·----------------~---------------- 32 

~torte4 beddin& itl,.-------------------------------------------.------- pl. 14 

, MD!tton of----------------------------------------------------------·-- 7-8 . ~-of _______________________________________________________ pis. 19-28 

~of____________________________________________________________ 23 

on )'fe1ds of--~---------------------------------------------------------- pl. 13 

. ~oroarapbs of.-------------------------------------;. ______ pls. 14, 17, 18 

tbin rfJiular lamination b;l. _ ---------------------------------------------- pl.l4 

&.Pal.-oaourrenoaof, in oll-sbale beds---------.-------------------------------- 31 · : ~niatter, appearance Of, in thin sections _________________ ----- ··--·-· 39-40 

' ~...-rpjnjfolia, pollen oL-----------------------·-----.. ····-------------- 48 

fit ,. ' p 

Rli1111<1MlL d6:tbilti0n Of •••••••••••••••••••••••••••••••••••••••• -........... 7 

shoWtngJleldbDity of·------------------------------------------- pl. 4 

~~'--~~~*ateOri~- eolumnar section of Green River formation on------------· pi: 7 W.~tm.1•· O$jk ttleli11:ler of Green River formation, broken clr.tJS. formed 

. ocourre:c!~'d~;;~:::::::::::::::::::::::::::::::::::::::::::: ~~:1! ~----------------~------------------"·---------------------------- ~ia ____________ 43 .:. ____________________________________________ -______ 40, pl. 19 

PJaaeus sp. ef. P. caudata Hfibner ••• .: •••••••••••• ________________________ 41, pl. 19 

Plao~pbs 

~ 

of oil shale ......................................... pis. 14,_17, 18 

cNek, broken cliffs of Garden Gulch and Parachute Oreltk members 

. ~n·---------·-·-·--····-·-·-----------·-··--·············-·-····• pl. 4 

fJ,cea.. ~of •. ------------------------------------------------------·-··-- 46 · ~. ·PGUen of.---~------------···--·-------------------····-···-------- 46, pi; 24 

Q 

~-

~ 

niliru.ia Bradle7, n.JP--------------------·-.;~c~.~~,;_ ..... '~•~~~~~~~ 

{8chnlle). ---------------------.. ·····-···--···--·~-·-'-.. ~--,. Quartz, trCIOUl'l'eDce of, in oll-sbale beds ..................................... ~:..:. •• ~ .... . 

Quereas JWinUI, pollen ol----·-····---~-----------·-··-···,;;;...'" • ..., ..... ~--<~.-o-. 

R 

BoaeQMseb, H., quoted •• ------------··-·---------------.. --------·• 

s 

Saline minerals and th&i~ sfg:oUicaxwe in the on-.. ~!ids ...... .,:. ••.•• 

Salt; calcite pseudomorphs of, 6Jling cracks in ~lstone ______ · 

Salt Cavities in Evaouation Creek member of Orela lf.f9'er fOI'DlMiola--~ 

Scudder, S. H., qnoted ................................................... . 

SeootrdarY minetals, occurrence of, in the oll....,.balls... ••••••• ..: •• -:-.. ·-···- : sepiolite, oeeurrenoe and "Character of, in oD-abale .,.._ ______ ..: .... ;.;.~~..::...~---~ 1 

::~:~ii~;~·--:_-_-_-_-_-_-_-_-_-_·_~---_-_-_·_~--------~--·:_~_-_-_-_-~-~·:.~.-_-_-_-_·:::..:·--~----·.-:i?::~· ' 

Siltstone, definition of.---------------··--·--------~--------·········--·~"-~·--

::!!::~~~~~----=::::::::::::::::::::::::::::::::::~::::::::::~~;f 

Spirogyra ... ---------..... ---------------------------· ~--· ----------------~ 

Spirulina duplex Wolle •• ---·-----·----·--------"'··--:.-•• .: .................. _ 

SteUate plant hair?------------------·-----------------------·-------· 40-47, 

StigeocloJlium? sp. cf. S.lubricum (Dillwyn) Kiit&ing • .., •••••• ;..;. ••••• ~ 

Strueture, features oL.---·------------------------------------.. --.;. ....... ,..,. •• : Strueturelesa organic matter ______________________________ .. _ ......................... : 

Syrphid larvae ............................................................. .., 

T 

Tabanid larvae.:_-----.----------•••• --·--·------.... -•• :. •••.••• --.......... - Tetraedron sp. cf. T. regulare var. torsum (Turner) Brunntbaler ....... .. 

Tbespesia populnea, peltate lllales of-----------------.;. ..... -.. ••• ~---··--:.:. • 

ThiJl sections, appearance of organic matter m:.:. •.•••.•••••.••••• .;;. •• .; •. ·..::..~.:.: 

preparMion of ••••. ---------------------------·-----·•---.:-••••• -.:.·.~_._ ..... __ 

Thuja, polleu of--------------------~- .••••••••• ..: •••• ;..;.:..;;.;.;.. ••••••••• · · · 

Topoarapby and drainage, features of. •••• ~----..:-~~-:--~-~·~.;.;--~-----·.: Torula.. _______________________________________ ~-------~·-----.; .. --~-:.. •• ::. 

Tlacheid, spiral thickening oL ••• r·······--·---'---:..-••.••• .; • .; _____ _ Trail Creek, oolumnai section of Green· River fonllat!cm OU..-------·-

Trichotbecirim •••••••••••••••••••••••• 7 •• --:---------··r ... " •• .,.:,.~_--.,?.~i"!'!;'"", 

u 

Uinta Basin, relations of Tertiary formations in.······-·-·------·.· .• ·! ..... ,...~...,. •. ~ 

Uinta Lake, phasee-of, dt1riDc the Gn!en RiVer;IP90L.--~---···-·,·--·~.._·f'· 

Unclassified fOl'lllS--------------------------... -.;..; .•••••.•• .; .•• .; ••. 

Urom,.. SP-------------·-·-----------:..---···-------~-----i-A 

v 

Varves, occurrence and cbaraeterd.. .......................... .._.,.,_,,.,.. .. ,.'"" ......... "'~,.., 

Vaucheria De Candolle-•• ·--·-·····---------·-----···'"""'·.,.,,,,.,,~.-.i.~·---·.;;.flr<­

Vlbumum amnouum, stell&t& haia Gf----.. ---------·-·.-···----;.~ .... ,."*.,'*,'"""~~'N~ 

w 

~,d8aeript1on and illllStrations oL-----------------------·· 47-48, pls. 24, 25 . 

Ward, H. :b., quoted ---------------·----;.·-------.--.-------------------~d.:.:. 

wu:,~gue~~~=~;~;;.::::::::::::::::::::~::::::::::::::::~::j 

Jt 

-~ 

, . 

;i 

·; 

-~ 

'=~=:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ::: 

!Jrite, ooourrenoe and character of, in oil-shale beds----·-----·-·------------ 30-31 

White, David, quoted ................ ~----------;. •••••••• ., ••• ..: •• -•••••• ..,! ....... ~ 

White River Canyon, Utah, columnar aectioa fl Green Rf'Vef fortrtatJoJl._..::; I . 

0 

,•