Simplified Stratigraphic Cross Sections of the Eocene 

Green River Formation in the Piceance Basin, 

Northwestern Colorado

By John D. Dietrich and Ronald C. Johnson

Open-File Report 2013–1012

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013 

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Suggested citation: Dietrich, J.D., and Johnson, R.C., 2013, Simplified stratigraphic cross sections of the 

Eocene Green River Formation in the Piceance Basin, northwestern Colorado: U.S. Geological Survey 

Open-File Report 2013–1012, 20 p.

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endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

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

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

References Cited........................................................................................................................................................ 2

Figures........................................................................................................................................................................ 3

Figures

Figure 1. Map showing extents of Uinta, Piceance, and Greater Green River Basins and approximate 

extent of oil shale in the Eocene Green River Formation............................................................................................ 4

Figure 2. Cross section showing members of the Eocene Green River Formation, stages in the evolution 

of Lake Uinta, correlation of rich (R) and lean (L) oil shale zones of Cashion and Donnell (1972), and oilyield histograms. Line of cross section is indicated on figure 1................................................................................... 5

Figure 3. North-south cross section through the Piceance Basin, northwestern Colorado, showing 

stratigraphic subdivisions, stages of Lake Uinta as defined by Johnson (1985), and some of the rich and 

lean zones defined by Cashion and Donnell (1972) ................................................................................................... 6

Figure 4. Map showing locations of the 13 stratigraphic cross sections in the Piceance Basin, Colorado............. 7

Figure 5. Cross section line 1 ................................................................................................................................ 8

Figure 6. Cross section line 2 ................................................................................................................................ 9

Figure 7. Cross section line 3 .............................................................................................................................. 10

Figure 8. Cross section line 4 .............................................................................................................................. 11

Figure 9. Cross section line 5 .............................................................................................................................. 12

Figure 10. Cross section line 6 .......................................................................................................................... 13

Figure 11. Cross section line 7 .......................................................................................................................... 14

Figure 12. Cross section line 8 .......................................................................................................................... 15

Figure 13. Cross section line 9 .......................................................................................................................... 16

Figure 14. Cross section line 10 ........................................................................................................................ 17

Figure 15. Cross section line 11 ........................................................................................................................ 18

Figure 16. Cross section line 12 ........................................................................................................................ 19

Figure 17. Cross section line 13 ........................................................................................................................ 20

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3) 

gallon (gal) 3.785 cubic decimeter (dm3) 
Simplified Stratigraphic Cross Sections of the Eocene 

Green River Formation in the Piceance Basin, 

Northwestern Colorado

By John D. Dietrich and Ronald C. Johnson

Introduction

Thirteen stratigraphic cross sections of the Eocene Green River Formation in the

Piceance Basin of northwestern Colorado are presented in this report. Originally published in a 

much larger and more detailed form by Self and others (2010), they are shown here in simplified, 

page-size versions that are easily accessed and used for presentation purposes. Modifications to 

the original versions include the elimination of the detailed lithologic columns and oil-yield 

histograms from Fischer assay data and the addition of ground-surface lines to give the depth of 

the various oil shale units shown on the cross section.

Stratigraphy of the Green River Formation, Colorado and Utah

The Green River Formation of the Piceance Basin was deposited in the Eocene Lake 

Uinta, a long-lived lake that covered much of the Piceance Basin, the Uinta Basin to the west in 

eastern Utah and westernmost Colorado, and the intervening Douglas Creek arch (fig. 1). Lake 

Uinta remained a single continuous lake across both basins and the Douglas Creek arch 

throughout most of its history, and most stratigraphic units can be recognized in both basins

(fig. 2). The early stages of the lake are marked by deposition of clay-rich oil shale referred to as 

the Garden Gulch Member (figs. 2, 3). Oil-shale zones deposited later in the lake’s history 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 

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” of the Green 

River Formation was first used by Donnell (1953). Sandstones and siltstones containing 

abundant volcanic debris intertongue with the upper part of the Green River Formation and form 

units within the Eocene Uinta Formation (Cashion and Donnell, 1974) in the northern part of the 

basin.

Cashion and Donnell (1972) recognized that the Parachute Creek and Garden Gulch 

Members could be subdivided into a sequence of oil-rich zones (R-zones) and oil-lean zones 

(L-zones) that could be recognized throughout much of the central part of the Piceance Basin and 

eastern part of the Uinta Basin (fig. 2). These zones appear to form approximate timestratigraphic units representing changing rates of organic matter production and preservation that 

occurred simultaneously throughout Lake Uinta. The rich and lean-zone stratigraphy formed the 

basis of the recent assessments of in-place oil shale resources in the Piceance and Uinta Basins

by the U.S. Geological Survey (Johnson and others, 2010a, 2010b). The lower zones, from the 
2

L-0 zone through the L-1 zone, are rich in clay and contain little carbonate; these form the 

Garden Gulch Member (fig. 2). All zones above the L-1 zone composing Parachute Creek 

Member (fig. 2) are dolomitic. Units above the R-6 zone are, (in ascending order); the B-groove, 

a lean zone; the Mahogany ledge, the richest oil shale zone in the basin; and the A-groove, 

another lean zone. The 13 cross sections (locations shown in fig. 4–17) show the distribution of 

the Green River Formation and the rich and lean zones within them.

References Cited

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.

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 on 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.

Donnell, J.R., 1953, Columnar section of rocks exposed between Rifle and DeBeque Canyon, 

Colorado: Rocky Mountain Association of Geologists Guidebook, Field Conference, 

Northwestern Colorado, p. 14.

Donnell, J.R., 2008, Intertonguing of the lower part of the Uinta Formation with the upper part of 

the Green River Formation in the Piceance Creek Basin during the late stages of Lake Uinta: 

U.S. Geological Survey Scientific Investigations Report 2008–5237, 25 p. (Also available at 

http://pubs.usgs.gov/sir/2008/5237/.)

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.

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, in Flores, R.M., 

and Kaplan, S.S., eds., Cenozoic paleogeography of the west-central United States: Rocky 

Mountain Paleogeography Symposium 3, The Rocky Mountain Section, Society of Economic 

Paleontologists and Mineralogists, p. 247–276.

Johnson, R.C., 2012, The systematic geologic mapping program and a quadrangle-by-quadrangle 

analysis of time-stratigraphic relations within oil shale bearing rocks of the Piceance Basin, 

western Colorado: U.S. Geological Survey Scientific Investigations Report 2012–5041, 35 p.

(Also available at http://pubs.usgs.gov/sir/2012/5041/.) 

Johnson, R.C., Mercier, T.J., Brownfield, M.E., Pantea, M.P., and Self, J.G., 2010a, An 

assessment of in-place oil shale resources in the Green River Formation, Piceance Basin, 

Colorado, chap. 1 of Oil shale and nahcolite resources of the Piceance Basin, Colorado: U.S. 

Geological Survey Digital Data Series Report 69-Y. (Also available at 

http://pubs.usgs.gov/dds/dds-069/dds-069-y/REPORTS/69_Y_CH_1.pdf.) 

Johnson, R.C., Mercier, T.J., Brownfield, M.E., and Self, J.G., 2010b, Assessment of in-place oil 

shale resources in the Eocene Green River Formation, Uinta Basin, Utah and Colorado, chap. 1

of Oil shale resources of the Uinta Basin, Utah and Colorado: U.S. Geological Survey Data 

Series Report DS 69-BB. (Also available at http://pubs.usgs.gov/dds/dds-069/dds-069-

bb/REPORTS/69_BB_CH_1.pdf.) 
3

Mercier, T.J., and Johnson, R.C., 2012, Isopach and isoresource maps for oil shale deposits in the 

Eocene Green River Formation for the combined Uinta and Piceance Basins, Utah and 

Colorado: U.S. Geological Survey Scientific Investigations Report 2012–5076, 86 p., 1 plate.

(Also available at http://pubs.usgs.gov/sir/2012/5076/.) 

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, chap. 5 of

Oil shale and nahcolite resources of the Piceance Basin, Colorado: U.S. Geological Survey 

Digital Data Series Report DS 69-Y. (Also available at http://pubs.usgs.gov/dds/dds-069/dds069-y/REPORTS/69_Y_CH_5.pdf.) 

Figures
4

Figure 1. Map showing the extents of Uinta, Piceance, and Greater Green River Basins and approximate 

extent of oil shale in the Eocene Green River Formation. Modified from Mercier and Johnson (2012).
5

Figure 2. Cross section showing members of the Eocene Green River Formation, stages in the evolution of Lake Uinta, correlation of rich (R) and 

lean (L) oil shale zones of Cashion and Donnell (1972), and oil-yield histograms. Line of cross section is indicated on figure 1. Modified from 

Mercier and Johnson (2012). (ft, feet) 
6

Figure 3. North-south cross section through the Piceance Basin, northwestern Colorado, showing stratigraphic subdivisions, stages of Lake Uinta 

as defined by Johnson (1985), and some of the rich and lean zones defined by Cashion and Donnell (1972). Modified from Johnson (2012).
7

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

Modified from Self and others (2010).
8

Figure 5. Cross section line 1. Modified from Self and others (2010).
9

Figure 6. Cross section line 2. Modified from Self and others (2010).
10

Figure 7. Cross section line 3. Modified from Self and others (2010).
11

Figure 8. Cross section line 4. Modified from Self and others (2010).
12

Figure 9. Cross section line 5. Modified from Self and others (2010).
13

Figure 10. Cross section line 6. Modified from Self and others (2010).
14

Figure 11. Cross section line 7. Modified from Self and others (2010).
15

Figure 12. Cross section line 8. Modified from Self and others (2010).
16

Figure 13. Cross section line 9. Modified from Self and others (2010).
17

Figure 14. Cross section line 10. Modified from Self and others (2010).
18

Figure 15. Cross section line 11. Modified from Self and others (2010).
19

Figure 16. Cross section line 12. Modified from Self and others (2010).
20

Figure 17. Cross section line 13. Modified from Self and others (2010).