Carbonate facies patterns and oil shale genesis in Eocene Green River Formation, Fossil basin, Wyoming

Conference · Tue Mar 01 04:00:00 EST 1983 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:6320208

Buchheim, H P

Facies patterns and associated vertical sequences of kerogenous carbonates (oil shales) of the Green River Formation in Fossil basin, Wyoming, provide new insights into the deposition of oil shale. Unique to Fossil basin is a facies pattern consisting of kerogen-rich calcimicrite at the basin's depocenter succeeded laterally by laminated calcimicrite, bioturbated calcimicrite, and finally calcareous siliciclastics. This same pattern occurs cyclically as a vertical sequence with oil shale at the base. The facies patterns and vertical sequences in Fossil basin are interpreted as being deposited in a closed-basin occupied by a lake with an ephemeral and hypersaline hypolimnion that underwent frequent vertical fluctuations that affected large areas of the lake bottom. The transgression-regression of the hypolimnion over large areas of lake bottom was possible because of a low topographic gradient on the lake bottom. Deposition of oil shale occurred within the denser, cooler, and hypersaline hypolimnion waters-laminated calcimicrite in a zone of chemocline fluctuation-and bioturbated calcimicrite was deposited in fresher nearshore zones. Kerogen-rich carbonates became more widespread in the later stages of the lake when it evolved into a shallow hypersaline lake. This suggests that kerogen deposition was controlled by high salinity rather than anoxic conditions. It is concluded that the carbonate facies patterns, vertical sequences, and oil shale genesis required a dynamic and fluctuating lake as well as a fluctuating chemocline level in a closed basin with a low topographic gradient. This differs from the static, anoxic, and deep basin model frequently postulated for Green River Formation oil shale deposition.

• Research Organization: Loma Linda Univ., Riverside, CA
• OSTI ID: 6320208
• Report Number(s): CONF-8304200-
• Conference Information: Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Journal Volume: 67:3
• Country of Publication: United States
• Language: English

Related Subjects

04 OIL SHALES AND TAR SANDS
040201* -- Oil Shales & Tar Sands-- Site Geology-- (-1989)
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
CARBONATE ROCKS
CENOZOIC ERA
DEPOSITION
ENERGY SOURCES
FEDERAL REGION VIII
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GREEN RIVER FORMATION
MATERIALS
NORTH AMERICA
OIL SHALES
ORIGIN
ROCKS
SEDIMENTARY ROCKS
TERTIARY PERIOD
USA
WYOMING