Oil shale formed in desert environment: Green River Formation, Wyoming

GSA Bulletin



The oil shale beds of the Wilkins Peak Member of the Green River Formation differ from most of the Green River oil shale of Colorado and Utah because very few of them have varves; they have numerous mud cracks and, locally, desiccation breccias. Many have a copropelic microstructure and contain labial plates and skin fragments of chironomid larvae. Microfossils of some of these oil shale beds include such normally perishable things as first instar midge larvae, a single spiral chloroplast of a green alga, and sporangia of aquatic fungi. Taken together, these features indicate that the oil shale originated from algal ooze that formed on the bottom of very shallow, spring-fed lakes. The algae (dominantly blue-greens) were not planktonic but grew on, and in, the flocculent ooze. At intervals, perhaps tens to hundreds of years, the lake levels fell enough to expose the algal ooze to the air and partial drying. In the resulting rubbery organic gel, the most delicate microorganisms were heat-fixed and thereby preserved as “mummified” tissue.

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Publication type Article
Publication Subtype Journal Article
Title Oil shale formed in desert environment: Green River Formation, Wyoming
Series title GSA Bulletin
DOI 10.1130/0016-7606(1973)84<1121:OSFIDE>2.0.CO;2
Volume 84
Issue 4
Year Published 1973
Language English
Publisher Geological Society of America
Description 4 p.
First page 1121
Last page 1123
Country United States
State Wyoming
Other Geospatial Green River Formation
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