Chapter 5

Stratigraphic Cross Sections of the 

Eocene Green River Formation in the 

Piceance Basin, Northwestern Colorado

By Jesse G. Self, Ronald C. Johnson, Michael E. Brownfield, and 

Tracey J. Mercier

Chapter 5 of 7 

Oil Shale and Nahcolite Resources of the Piceance 

Basin, Colorado

By U.S. Geological Survey Oil Shale Assessment Team

U.S. Geological Survey Digital Data Series DDS–69–Y

U.S. Department of the Interior

U.S. Geological Survey

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U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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Suggested citation:

Self, J.G., Johnson, R.C., Brownfield, M.E., and Mercier, T.J., 2010, Stratigraphic cross sections of the Eocene Green 

River Formation in the Piceance Basin, northwestern Colorado: U.S. Geological Survey Digital Data Series DDS–69–Y, 

chp. 5, 7 p.

ISBN: 1–4113–2668–2
iii

Contents

Introduction.....................................................................................................................................................1

Stratigraphy of the Green River Formation, Colorado and Utah ............................................................1

Cross Sections................................................................................................................................................1

References Cited............................................................................................................................................6

Plates

1. Detailed cross section of line 1............................................................................................. link

2. Detailed cross section of line 2............................................................................................. link

3. Detailed cross section of line 3............................................................................................. link

4. Detailed cross section of line 4............................................................................................. link

5. Detailed cross section of line 5............................................................................................. link

6. Detailed cross section of line 6............................................................................................. link

7. Detailed cross section of line 7............................................................................................. link

8. Detailed cross section of line 8............................................................................................. link

9. Detailed cross section of line 9............................................................................................. link

10. Detailed cross section of line 10........................................................................................... link

11. Detailed cross section of line 11........................................................................................... link

12. Detailed cross section of line 12........................................................................................... link

13. Detailed cross section of line 13........................................................................................... link

Figures

1. Map showing location of the Piceance Basin, northwestern Colorado .............................2

2. Stratigraphic column for the oil shale zones of the Green River Formation.......................3

3. Stratigraphic column for the Piceance Basin, northwestern Colorado..............................4

4. Map showing locations of the 13 cross sections in the Piceance Basin, Colorado .........5

Table

1. Names and definitions for the column headers for the spatial-data 

spreadsheet...................................................................................................................................6
Introduction

For several decades, the U.S. Geological Survey (USGS) 

collected cores, cuttings, and other subsurface data from boreholes drilled to evaluate the oil shale deposits in the Eocene 

Green River Formation in the Piceance Basin of northwestern 

Colorado (fig. 1). In Colorado, the Green River Formation 

was deposited in Lake Uinta during early to middle Eocene 

time, with the richest oil shale deposits in the Garden Gulch 

and Parachute Creek Members (fig. 2). It was from this area 

that data were collected and preserved for use by researchers 

and industry in anticipation of the time when Green River oil 

shale deposits would become an economically viable alternate 

source of unconventional fossil fuel.

The types of data collected include (1) thousands of 

Fischer (shale oil) assays (American Society for Testing and 

Materials, 1980) on cores and cuttings from rotary-drilled 

holes; (2) geophysical and lithologic logs of drill holes; and 

(3) measured sections from outcrops within the Piceance 

Basin. As part of the in-place assessment of the oil shale 

resources of the Green River Formation in the Piceance 

Basin conducted by the USGS, subsurface stratigraphic cross 

sections were created using various types of data for correlation. These cross sections are presented on plates 1–13 in this 

report.

Stratigraphy of the Green River 

Formation, Colorado and Utah

The Green River Formation consists of fine-grained 

lacustrine and fluvial-lacustrine rocks that were deposited in 

the Eocene Lake Uinta. The lake expanded early in its history, 

during the Long Point transgression (Johnson, 1985), to cover 

much of the Piceance and Uinta Basins, as well as the intervening Douglas Creek arch, an area between the two basins 

with low rates of subsidence. Lake Uinta remained a single 

unbroken lake across both basins and the Douglas Creek arch 

throughout most of its history, and most of the Green River 

Formation can be recognized in both basins. In the Piceance 

Basin (fig. 3), the early stages of the lake are marked by clayrich oil shale zones referred to as the Garden Gulch Member, 

whereas the younger oil shale zones deposited in the lake are 

carbonate-rich and referred to as the Parachute Creek Member. 

These oil shale units grade marginward into marginal lacustrine rocks of the Douglas Creek and Anvil Points Members.

The oldest member of the Green River Formation is the Cow 

Ridge Member, which intertongues with the variegated mudstones, sandstones, and siltstones of the underlying Wasatch 

Formation. The names Garden Gulch, Parachute Creek, and 

Douglas Creek Members of the Green River Formation were 

first used by Bradley (1931); the name Anvil Points Member 

was first used by Donnell (1953); and the name Cow Ridge 

Member was first used by Johnson (1984). The sandstones and 

siltstones containing abundant volcanic debris that intertongue 

with the upper part of the Green River Formation are referred 

to as the Uinta Formation (Cashion and Donnell, 1974; see 

plate 13). 

Cross Sections

The 13 cross sections prepared for this assessment used 

the same stratigraphic contacts as were drawn in previous 

studies (Pitman and Johnson, 1978; Pitman, 1979; Pitman 

and others, 1989) in order for resource-assessment results to 

be comparable. In these new sections, we also: (1) separate 

the Green River oil shale-bearing strata into alternating layers of oil-rich zones (R-zones) and oil-lean zones (L-zones), 

following Cashion and Donnell (1972), because they are 

recognizable in much of the Piceance Basin; and (2) distinguish between the clay-rich zones (zones R-0 through L-1) 

within the Garden Gulch Member, and the carbonate-rich 

zones (zones above L-1) within the Parachute Creek Member 

(fig. 2).

The cross sections (see fig. 4 for locations) were constructed using 68 of the 780 oil-yield histograms created for 

this assessment, geophysical logs collected from wells drilled 

for oil and gas exploration, and 12 surface sections measured 

from outcrops within the Piceance Basin; table 1 provides 

information for the data used. The correlation datum for cross 

sections 1–12 (pls. 1–12) is the top of the R-4 zone, and for 

cross section 13 (pl. 13) the datum is the bottom of the R-5 

zone. A horizontal scale of 1 in. = 0.5 mi and a vertical scale 

of 1.3 in. = 100 ft were selected to best accommodate the 

Stratigraphic Cross Sections of the Eocene Green River 

Formation in the Piceance Basin, Northwestern Colorado

By Jesse G. Self, Ronald C. Johnson, Michael E. Brownfield, and Tracey J. Mercier
2 Stratigraphic Cross Sections of the Eocene Green River Formation in the Piceance Basin, Northwestern Colorado

City, town

Extrusive and intrusive

 igneous rocks

Mesaverde Fm. and Mesaverde

 Group coal-bearing rocks

Undivided Quaternary, Tertiary,

 Mesozoic, and Paleozoic

EXPLANATION

TERTIARY

CRETACEOUS

County line

Uinta Formation and undivided

 Tertiary

Green River Formation

Wasatch Formation and undivided

 lower Tertiary

0 50 MILES

Colorado

Index map

Delta

Eagle

Garfield

Gunnison

Mesa

Moffat

Pitkin

Rio Blanco

Routt

40

40

70

70

50

50

Grand 

Junction

Gunnison

Montrose

Craig

Glenwood

Springs

39°00'

41°00'

40°00'

109°00' 108°00' 107°00'

Colorado River

G

Yampa River

reen

River

Meeker

Rangely

Steamboat

Springs

64

13

13

139

Montrose

Rifle

Piceance

 Basin

Figure 1. Geologic map of northwestern Colorado showing generalized outcrops of the Cretaceous 

Mesaverde Formation (Group) and the Eocene Wasatch, Green River, and Uinta Formations in the Piceance 

Basin. Modified after Brownfield and others (2000).
Cross Sections 3

Figure 2. Stratigraphic nomenclature and correlation chart for oil-shale zones for the north-central 

part of the Piceance Basin, Colorado. This assessment uses the nomenclature of Donnell and Blair 

(1970) and Cashion and Donnell (1972) shown in yellow.

Donnell and Blair,

(1970); Cashion and

Donnell (1972)

A-groove A-groove

B-groove B-groove

Rich oil shale

zone R-6

Rich oil shale

zone R-5

Rich oil shale

zone R-4

Rich oil shale

zone R-3

Rich oil shale

zone R-2

Mahogany

zone

Correlation chart of stratigraphic

nomenclature for oil shale zones

Parachute Creek Member (part)

Green River Formation (part)

Rich oil shale

zone R-1

Rich oil shale

zone R-0

Lean oil shale zone L-2

Lean oil shale zone L-1

Lean oil shale zone L-0

Lean oil shale

zone L-4

Lean oil shale zone L-3

Lean oil shale

zone L-5

Uinita Formation

(part)

Wasatch

Formation

(part)

Eocene

Age Unit Green River Formation Garden Gulch

Member Parachute Creek Member

Dyni (1974)

Garden Gulch

Member

Lower

Middle

Upper

Zone 9

Zone 10

Zone 11

Zone 12

Zone 13

Zone 8

Zone 2

Zone 3

Zone 4

Zone 5

Zone 6

Zone 1

Zone 7

Mahogany zone
No

Mahogany zone Uinta Formation 

 Top of Cretaceous R-0, L-0 zones R-1 zone L-1 zone R-2, L-2, R-3, L-3 zones R-4, L-4, R-5 zones L-5 zone R-6 zone and B-Groove Wasatch Formation Wasatch Formation Wasatch Formation Cow Ridge Member, Green River Formation Garden Gulch Member Fort Union Formation Top of Mahogany oil shale zone South Uinta Formation Parachute Creek Member Parachute Creek Mbr. Freshwater lacustrine and paludal rocks with molluscs and thin coal beds Lean dolomitic oil shale Rich dolomitic oil shale with nahcolite and halite Variegated mudstone, sandstone, and siltstone Lean illitic oil shale Rich illitic oil shale Carbonate-rich marginal lacustrine mudstone with ostracodal, oolitic, and stromatolitic limestones Volcanoclastic rocks Disseminated nahcolite in oil shale Nahcolite and halite EXPLANATION Douglas Creek Member 0 20,000 60,000 FEET 10 KILOMETERS 0 500 1,000 1,500 400 200 FEET METERS Vertical exaggeration x 40 DATUM Anvil Points Mem

Figure 3. Stratigraphic column for the Piceance Basin, northwestern Colorado, showing the Wasatch, Fort Union, Green River, and Uinta Formations and associated members.
Cross Sections 5

108°30' 108°00’

12 MILES

40°00’

39°30'

Area underlain by the

 Mahogany bed

EXPLANATION

0

Colorado

R. 100 W.

R. 100 W.

R. 101 W.

R. 101 W.

R. 99 W.

R. 99 W.

R. 98 W.

R. 98 W.

R. 97 W.

R. 97 W.

R. 96 W.

R. 96 W.

R. 102 W.

R. 102 W.

R. 95 W.

R. 95 W.

R. 94 W.

R. 94 W. R. 93 W.

T. 8 S.

T. 7 S.

T. 6 S.

T. 5 S.

T. 4 S.

T. 3 S.

T. 2 S.

T. 1 S.

T. 1 N.

T. 2 N.

1

2

3

4 5

6

7

8

9

10

12

11

13

Figure 4. Map showing locations of the 13 stratigraphic cross sections in the Piceance Basin, Colorado.
6 Stratigraphic Cross Sections of the Eocene Green River Formation in the Piceance Basin, Northwestern Colorado

distances covered and the need for stratigraphic detail. Sources 

of stratigraphic data include Johnson (1975) for the Long 

Point measured section, and Johnson and others (1988) for the 

Douglas Pass, Little Burma Road, and Tommy’s Draw sections. Measured sections at Yellow Creek, Spring Creek, and 

References Cited

American Society for Testing and Materials, 1980, Standard 

method of test for oil from oil shale: Annual Book of 

ASTM Standards, Part 25, Designation D 3904-80, 

p. 513–515.

Bradley, W.H., 1931, Origin and microfossils of the oil shale 

of the Green River Formation of Colorado and Utah: U.S. 

Geological Survey Professional Paper 168, 58 p.

Brownfield, M.E., Hettinger, R.D., and Johnson, E.A., 2000, 

A summary of the stratigraphy, coal resources, and coal-bed 

methane potential of Northwest Colorado: U.S. Geological 

Survey Professional Paper 1625-B, p. I1–I25,

Cashion, W.B., and Donnell, J.R., 1972, Chart showing 

correlation of selected key units in the organic-rich 

sequence of the Green River Formation, Piceance Creek 

Basin, Colorado, and Uinta Basin, Utah: U.S. Geological 

Survey Oil and Gas Investigations Chart OC-65.

Cashion, W.B., and Donnell, J.R., 1974, Revision of nomenclature of the upper part of the Green River Formation, 

Piceance Creek Basin, Colorado, and Eastern Uinta Basin, 

Utah: U.S. Geological Survey Bulletin 1394-G, 9 p.

Table 1. Names and definitions for the column headers for the spatial-data spreadsheet (Spatial_Information.xlsx).

Column name Column definition

USGSID Unique ID assigned by staff geologist

COMPANY Name of the company or agency that drilled the borehole 

NAME Name of the borehole assigned by the company or agency that drilled it

SECTION Section

TOWNSHIP Township 

RANGE Range

LATITUDE Latitude, in decimal degrees, North American Datum 1927, software-calculated, original record

LONGITUDE Longitude, in decimal degrees, North American Datum 1927, software-calculated, original record

COUNTY Name of county in Colorado 

DEPTH IN FEET Total depth of the borehole, in ft

PLATE NUMBER The Piceance Basin cross section where that piece of data can be found

Donnell, J.R., 1953, Columnar section of rocks exposed 

in Field 

Conference in northwestern Colorado, Rocky Mountain 

Association of Geologists Guidebook, Field Conference, 

Northwestern Colorado, p. 14.

Donnell, J.R., and Blair, R.W., 1970, Resource appraisal of 

three rich oil-shale zones in the Green River Formation, 

Piceance Creek Basin, Colorado: Colorado School of Mines 

Quarterly, v. 65, p. 73–87.

Dyni, J.R., 1974, Stratigraphy and nahcolite resources of the 

saline facies of the Green River Formation in northwest 

Colorado; in Murray, D. Keith, ed., Guidebook to the 

Energy Resources of the Piceance Creek Basin, Colorado, 

Rocky Mountain Association of Geologists, 25th Field 

Conference, p. 111–122.

Johnson, R.C., 1975, Preliminary geologic map, oil-shale yield 

histograms and stratigraphic sections, Long Point quadrangle, Garfield County, Colorado: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-688, scale 1:24,000 

(Two sheets with descriptive text).

Johnson, R.C., 1984, New names for units in the lower part 

of the Green River Formation, Piceance Creek Basin, 

Colorado: U.S. Geological Survey Bulletin 1529-I, 20 p.

Johnson, R.C., 1985, Early Cenozoic history of the Uinta and 

Piceance Creek Basins, Utah and Colorado, with special 

reference to the development of Eocene Lake Uinta United 

States: Rocky Mountain Section, Society of Economic 

Paleontology and Mineralogy: Denver, Colo., p. 247–276.
References Cited 7

Johnson, R.C., Nichols, D.J., and Hanley, J.H., 1988, 

Stratigraphic sections of lower Tertiary strata and charts 

showing palynomorph and mollusc assemblages, Douglas 

Creek arch area Colorado and Utah: U.S. Geological Survey 

Miscellaneous Field Investigations Map MF-1997, 2 sheets.

Pitman, J.K., 1979, Isopach, structure contour, and resource 

maps of the R-6 oil-shale zone, Green River Formation, 

Piceance Creek Basin, Colorado: U.S. Geological Survey 

Miscellaneous Field Investigations Map MF-1069, scale 

1:126,720.

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Pitman, J.K., and Johnson, R.C., 1978, Isopach, structure 

contour, and resource maps of the Mahogany oil-shale zone, 

Green River Formation, Piceance Creek Basin, Colorado: 

U.S. Geological Survey Miscellaneous Field Investigations 

Map MF-958, scale 1:126,720.

Pitman, J.K., Wahl Pierce, Frances, and Grundy, W.D., 1989, 

Thickness, oil-yield, and kriged resource estimates for the 

Eocene Green River Formation, Piceance Creek Basin, 

Colorado: U.S. Geological Survey Oil and Gas Investigations Chart OC-132.