Siliceous shales of the Laney Member of the Green River Formation are exposed in outcrops around Fontenelle Reservoir in the northwest corner of the Green River Basin, Wyoming. An analysis of these shales is important to an understanding of the origin of laminites in the Green River formation. The shales are rhythmic, varve -like laminites, composed of quartz, authigenic potassium feldspar , dolomite, and zeolite minerals. The association of these minerals suggest that the original sediment contained significant amounts of volcanic ash, and were deposited in a shallow, near-shore, oxygenated saline - alkaline lake environment, as inferred from (1) the association of stromatolites , mud-cracked dolomicrites and ostracodal micrite, (2) fossil occurrences of Knightia (Herring-type fish) and Equisetum (horsetail), Astephus (catfish), Amyzon (sucker ) and (3) presence of dolomite and aragonite.
The excellent preservation of these mineral-organic laminites and the fossils they contain (Knightia, Astephus, and Amyzon) in shallow-water, near-shore sediments is problematic for the stratified-lake model. Fish buried by sediment in an oxygenated environment would not exhibit complete preservation if exposed to aerobic decay for extended periods. Preservation in this environment is predicted only under conditions of rapid deposition and burial. Near-shore sediments, volcanogenic minerals, low kerogen content, and excellent fossil-fish preservation indicated rapid sedimentation in a near shore, oxygenated, saline environment that is consistent with the playa - lake model.
H. Paul Buchheim
Ivan G. Holmes
Conrad D. Clausen
Master of Science (MS)
Year Degree Awarded
Date (Title Page)
Library of Congress/MESH Subject Headings
Shale -- Wyoming -- Analysis
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This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.
Rasmussen, Michael G., "Depositional Environments of Siliceous Laminites in the Laney Member of the Green River Formation, Sublette County, Wyoming" (1983). Loma Linda University Electronic Theses, Dissertations & Projects. 1015.
Loma Linda University Electronic Theses and Dissertations
Loma Linda University. Del E. Webb Memorial Library. University Archives