Mass-Movement Deposits in the Lacustrine E cene Green 

River Formation, Piceance Basin, Western Colorad

By Ronald C. Johnson, Justin E. Birdwell, Michael E. Brownfield, and Tracey J. Mercier

Open-File Report 2015–1044

U.S. Department of the Interior

U.S. Geological Survey

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o
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015 

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Suggested citation:

Johnson, R.C., Birdwell, J.E., Brownfield, M.E., and Mercier, T.J., 2015, Mass-movement deposits in the 

lacustrine Eocene Green River Formation, Piceance Basin, western Colorado: U.S. Geological Survey 

Open-File Report 2015–1044, 40 p., http://dx.doi.org/10.3133/ofr20151044. 

ISSN 2331-1258 (online)
U.S. Department of the Interior

U.S. Geological Survey

Mass-Movement Deposits in the 

Lacustrine Eocene Green River 

Formation, Piceance Basin, 

Western Colorado

Ronald C. Johnson, Justin E. Birdwell, 

Michael E. Brownfield, and Tracey J. Mercier
The Eocene Green 

River Formation was 

deposited in two large 

Eocene saline lakes, 

Lake Uinta in the Uinta 

and Piceance Basins 

and Lake Gosiute in 

the Greater Green 

River Basin.

Here we will discuss 

mass-movement 

deposits in just the 

Piceance Basin part of 

Lake Uinta.

Modified from Johnson 

(2012)
West-east cross section across the Uinta and Piceance Basins and the Douglas Creek 

arch. The arch acted as a hinge-line between the two subsiding basins. Little sediment 

was deposited on the crest of the arch prior to the development of saline Lake Uinta.
In a depositional sense, there are generally two types of 

oil shale in the Piceance Basin

Most people associate the Green 

River Formation with welllaminated oil shale shown here, 

largely because it is the dominant 

type of oil shale where the Green 

River Formation crops out 

around the basin margins.

But another type of oil shale, 

generally referred to as “blebby oil 

shale,” appears to have been 

deposited by mass-movement 

processes. 

80-112, sec. 16, T. 5 S., R. 98 W., Desert Gulch quadrangle, 

elevation approx. 6,970 feet (ft), elevation top of Mahogany 

zone about 7,190. Photo is from 220 ft below top Mahogany 

zone, near middle of R-6 zone.
Bradley (1931, p. 28) noted the occurrence of “shale breccias” or oil shales

that “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.” 

81-31 Tommy’s draw from float
Middle of the R-6 zone in the southwest part of the basin (Sec. 22, T. 5 S., R. 99 W., field location 80-112) 

Bradley (1931) also noted that the boundaries of the fragments, some laminated, 

were commonly sharply defined indicating that they were lithified prior to being 

exhumed and incorporated into the breccias. 
Examples of “blebby oil shale” from the central part of 

Lake Uinta Piceance Basin (from Dyni, 1981)

Dyni (1981) and Dyni and 

Hawkins (1981) studied these 

mass-movement deposits in 

core from the central part of 

the basin and attributed some 

of them to deep-water turbidity 

currents. 

Dyni (1981) and Dyni and 

Hawkins (1981) estimated 40–

50 percent of the lower part of 

the Parachute Creek Member 

in the central part of the basin 

consisted of “blebby oil shale.”

Note the grading in the blebby 

oil shale bed in the upper right, 

from abundant large marlstone 

fragments at the base to 

kerogen in a very fine-grained 

matrix at the top.
U.S. Department of the Interior

U.S. Geological Survey

Tanavsuu-Milkeviciene and Sarg (2012) studied the 

distribution of lacustrine facies in the Piceance Basin, 

and like Dyni (1981) and Dyni and Hawkins (1981), they 

found an increase in oil shale that was affected by 

mass-movement processes toward the central part of 

the basin.
U.S. Department of the Interior

U.S. Geological Survey

Here we attempt to build on the 

excellent work of these previous 

authors by placing massmovement deposits into a 

detailed spatial and temporal 

framework 
Data sources

 Photos from nine coreholes that are housed at 

the U.S. Geological Survey Core Research 

Facility in Lakewood, Colorado, were examined 

for bedding features. The photos are available 

online at the Core Facility’s Web Site. 

 Outcrop sections were measured and described 

by the authors. All of the sections have been 

published, but thickness of individual beds were 

not reported. Thickness values were obtained 

from the original descriptions in field notebooks. 
Mass-movement deposits commonly incorporated large blocks of 

laminated oil shale that appear to have been largely lithified prior to redeposition. These blocks can look like laminated intervals in core.

81-36 Tommys Draw Section, 2256' Mahogany zone

4 inch core
West-east cross section across the Uinta and Piceance Basins and the Douglas Creek arch. 
Lake Uinta began as a 

freshwater lake (Cow 

Ridge Member), became 

increasing saline during 

the illitic phase (Garden 

Gulch Member), finally 

becoming a carbonateand saline-mineral 

precipitating lake 

(Parachute Creek 

Member). Infilling with 

volcaniclastics began in 

the latter part of the 

carbonate phase (light 

purple). 

Modified from Johnson and others 

(2010)

South to north cross section
Condenser

Adapter

100-millileters 

centrifuge

tube

Cooling

bath

Oven

Retort

Rock

Uncondensed gas

to exhaust

Oil

95 grams of <8 mesh rock 

is heated from 25 to 500oC 

in 40 minutes and held at 

500oC for an additional 40 

minutes

Products collected:

condensed oil

condensed water

spent rock

Reported values:

weight percent (wt%) oil

wt% water

wt% loss (gases)

oil density

coking tendency 

Wt% oil is converted to

gallons per ton oil here.

Oil yields using the Fischer 

assay method are shown 

on the subsequent slides. 

Pictured is a Fischer assay 

retort. 
The Garden Gulch and Parachute Creek Members are subdivided into 16 recognized rich (R) and 

lean (L) oil-shale zones. Red graphs are gallons per ton oil using Fischer Assay. Maps showing 

percent of mass-movement deposits in each zone were constructed. The next slide is a 

paleogeographic map for the end of the preceding freshwater phase.

Modified from 

Mercier and 

Johnson (2012)

Index map
Extent of freshwater lakes just prior to the development of Lake Uinta. Isopach map 

is from the top of the Cretaceous to the top of the freshwater phase.

No rocks are preserved over 

the crest of the Douglas 

Creek arch from this 

extended period of time

Area of continuous 

offshore lacustrine 

shale deposition

Depositional settings shown beyond 

present-day extent of Mahogany are 

extrapolations

Uinta Basin 
Lake Uinta formed as a result of a major transgression—the Long Point transgression. This map 

shows Lake Uinta during maximum transgression when low-grade oil shale was deposited over 

large parts of the Uinta and Piceance Basins. Oil yield in gallons per ton Fischer Assay is shown.

Uinta Basin 
Subsequent slides progress through the development of the rich (R) and lean (L) oil shale zones 

in the Piceance Basin showing the distribution of mass-movement deposits.

. 

Uinta Basin 
Marginal shelves prograded (green arrows) from the southeast and northeast during R-0 time and 

from the southwest during R-1 time. No mass-movement deposits were identified in the R-0 zone, 

whereas mass-movement deposits accumulated at the base of the expanding shelf during R-1 time.

End of R-0 End of R-1 

Piceance 

Basin

Illitic Phase

Progradation

Progradation

Progradation
Total organic matter, measured by barrels of oil per acre (BPA), increases toward the center of 

the basin in the R-0 zone, which contains no mass-movement deposits, whereas total organic 

matter is greatest where mass-movement deposits are greatest in the R-1 zone.

End of R-0 End of R-1 

Piceance 

Basin

Illitic Phase

Progradation
Mass-movement deposits are much less common in the L-1 lean zone than the 

underlying richer R-1 zone.

End of R-1 End of L-1 Piceance 

Basin

Illitic Phase
Oil-shale beds are preserved in marginal lacustrine environments, indicating that 

significant organic matter was accumulating there. Many of these beds occur above 

the bulbous structures on stromatolites that may have offered protection from lateral 

transport. This bed is in the R-1 zone.

R.C. Johnson field locality 8/75, measured section 

North Dry Fork, The Saddle quad. Sec. 26, T. 7. S. Illitic Phase R. 99W. Upper part of R-1 
Interpretation for R-1 zone

 Mass-movement deposits 

accumulated at the slope 

between marginal shelves and 

the deep lake area. 

 The mineral matter and organic 

matter that made up the massmovement deposits originated on 

the marginal shelves and slope 

on the southeast and southwest 

parts of the lake.

 Brines that formed on the 

marginal shelves may have been 

incorporated into the massmovement deposits.

 Brines may also have formed on 

the northeast and north margins 

of the lake, but mass-movement 

deposits were rare there.

Illitic Phase
At the time of the Long Point 

transgression, a freshwater lake had 

occupied the central part of the 

Piceance Basin for more than 3 million 

years. There is no evidence that this 

lake ever filled in, and it is likely that it 

was relatively deep.

Lake Uinta transgressed across the 

marginal shelves and alluvial plains 

during the Long Point transgression 

depositing low-grade oil shale over a 

wide area.

Infilling began, producing broad 

marginal shelves that ultimately 

reached the deep central part of Lake 

Uinta before halting.

The shelf edge and slope were 

subject to failure with mass-movement 

deposits accumulating at the base of 

the slope. From Johnson and Brownfield (in press)

Illitic Phase Summary
End of illitic phase–

beginning of 

carbonate phase

Major drainage

By the end of the illitic phase, offshore oil-shale deposition had been replaced by shallow-water shelf 

deposition throughout all but the deep trough of the Uinta Basin. Sediments from the southern Uinta Basin 

spilled over to create an expanding shelf along the southwest margin of the Piceance Basin.

AAPG talk 14, also Leached zone figs. After review fig. 17 Uinta and Piceance at beginning R-2 also 2ed layer in UintaPiceance map with max Cow R

From Johnson and 

Brownfield (in press)
End of illitic phase–

beginning of 

carbonate phase

Major drainage

Many authors have stressed the importance of evaporation on lake-margin mud flats in producing 

concentrated brines (Smith, 1974, p. 77; Ryder and others, 1976; Eugster and Hardie, 1978; Surdam and 

Stanley, 1979; Johnson, 1985; Remy and Ferrell, 1989). 

AAPG talk 14, also Leached zone figs. After review fig. 17 Uinta and Piceance at beginning R-2 also 2ed layer in UintaPiceance map with max Cow R

From Johnson and 

Brownfield (in press)
By the beginning of the carbonate and saline mineral phase of the lake (Parachute 

Creek Member, R-2 oil shale zone), shelf building had slowed. Mass-movement 

deposits now accumulated mainly in the central part of the lake. 

End of R-2 End of L-2 

Piceance 

Basin

Piceance 

Basin

Saline Phase
Some shelf building continued during the early carbonate phase. 

The R-2 and L-2 zones are thickest at the base of the shelf.

From Johnson and others (2010)

End of R-2 End of L-2 

Saline Phase

Piceance 

Basin

Piceance 

Basin
End of R-3 End of L-3 

The R-3 zone is predominantly composed of mass-movement deposits in the center 

of the lake, whereas the overlying L-3 zone contains almost no mass-movement 

deposits.

Piceance 

Piceance Basin

Basin

Saline Phase
End of L-4 

The lake began to expand over the marginal shelves in R-4 time. The rich R-4 zone is 

mainly composed of mass-movement deposits in the center of the lake, whereas 

mass-movement deposits are somewhat less in the overlying leaner L-4 zone.

End of R-4 

Piceance 

Basin

Piceance 

Basin

Saline Phase
End of R-5 End of L-5 

The R-5 zone contains abundant mass-movement deposits, whereas massmovement deposits are rare in the overlying leaner L-5 zone.

Piceance 

Basin

Piceance 

Basin

Saline Phase
B-groove

The percentage of mass-movement deposits progressively decreased as deepwater conditions continued to encroach on the marginal shelf during R-6 time. The 

overlying lean B-groove contains almost no mass-movement deposits.

End of R-6 

Piceance 

Basin Piceance 

Basin

Saline Phase
End of Mahogany A-groove

Deep-water conditions were dominant over the former marginal shelves during 

deposition of the Mahogany zone. Mass-movement deposits are rare in the 

Mahogany and absent in the overlying lean A-groove.

Piceance 

Basin

Saline Phase
From Johnson and Brownfield (in press).

During the early stages of the 

saline mineral phase (Parachute 

Creek Member), Lake Uinta 

repeatedly transgressed and 

regressed across the marginal 

shelves, providing opportunities 

for sediments and organic 

matter to be exhumed and 

transported to the central part of 

the lake.

As Lake Uinta expanded and 

deepened, mass-movement 

deposits diminished.

Saline Phase Summary
Huge slumps and massmovement deposits of all 

sorts occurred during the 

infilling stage of Lake 

Uinta. 

Modified from Johnson and others (2010)

South-to north cross section

Location of photo in 

next slide Infilling Phase
Following deposition of the Mahogany zone, Lake Uinta began to fill in from north to south. Slumps 

during the infilling stage of the lake can be several hundred feet thick, cover several square miles, 

and can be underlain and overlain by laminated marl and oil shale. This slump extends along a valley 

wall for 2.1 miles.

Blebby and laminated, Uinta slumps and blebs, R.C. Johnson field locality 88-85 02 , sec. 14, T. 3 S., R. 99 W. Above Black Sulphur Tongue and below marlstone at Bull Fork

Infilling Phase
Conclusions

 Mass-movement deposits during the illitic phase of Lake 

Uinta contain fewer clasts than the carbonate phase of the 

lake suggesting that the source area was mostly 

unlithified. 

 Mass-movement deposits during the carbonate phase of 

the lake (Parachute Creek Member) contain abundant 

clasts indicating early lithification of sediments in 

marginal areas. These flows are most abundant in the 

central part of the depocenter. 

 Mass-movement deposits accumulated at the base of the 

prograding shelves until the shelves reached the deep 

central part of the lake when progradation slowed. Massmovement deposits then reached the central deep part of 

the lake.
Conclusions (continued)

 Large amounts of organic matter were included in massmovement deposits.

 Highly saline brines that evolved on the marginal shelves 

may have been incorporated into the mass-movement 

deposits. 

 Lean zones tend to include less mass-movement deposits 

than adjacent rich zones, possibly because organic-rich 

sediments were more prone to failure.
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. 

 Dyni, J.R., 1981, Geology of the nahcolite deposits and associated oil shales of the Green River Formation in the Piceance 

Creek Basin, Colorado: Boulder, University of Colorado, Ph.D. 

dissertation, 144 p.

 Dyni, J.R., and Hawkins, J.E., 1981, Lacustrine turbidites in the 

Green River Formation, northwestern Colorado: Geology, v. 9, p. 

235–238. 

 Johnson, R.C., Mercier, T.J., Brownfield, M.E., Pantea, M.P., and 

Self, J.G., 2010, An assessment of in-place oil shale resources 

of the Green River Formation, Piceance Basin, Colorado—Oil 

shale and nahcolite resources of the Piceance Basin, Colorado: 

U.S. Geological Survey Digital Data Series DDS–69-Y, chap. 1, 

187 p.
References Cited (cont.)

 Johnson, R.C., and Brownfield, M.E., in press, Development, 

evolution and destruction of the saline mineral area of Eocene 

Lake Uinta, Piceance Basin, western Colorado: U.S. Geological 

Survey Scientific Investigations Report, 73 manuscript pages, 

35 figures, and 2 plates.

 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, 85 p., 1 pl. 

http://pubs.usgs.gov/sir/2012/5076/

 Tanavsuu-Milkeviciene, Kati, and Sarg, J.F., 2012, Evolution of 

an organic‐rich lake basin—Stratigraphy, climate and 

tectonics—Piceance Creek basin, Eocene Green River 

Formation: Sedimentology, v. 59, no. 6, p. 1735–1768.