--> --> Abstract: Radiogenic Isotope Chemostratigraphy and Stratal Geometries of the Lacustrine Laney Member, Green River Formation, Southwestern Wyoming, by M. K. Rhodes; #90925 (1999)

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RHODES, MEREDITH K., University of Wisconsin-Madison, Dept. of Geology & Geophysics, Madison, WI

Abstract: Radiogenic Isotope Chemostratigraphy and Stratal Geometries of the Lacustrine Laney Member, Green River Formation, Southwestern Wyoming

The Eocene Green River Formation of southwestern Wyoming represents the long-lived Lake Gosiute. Lake Gosiute was located in the structurally divided foreland of the Sevier Thrust Front, bounded by geochernically distinct Laramide style uplifts to the north, east, and south. Lake Gosiute existed 5° to 8° south of its present location and hosted a diverse flora and fauna determined to have subtropical affinities.

The sediments that were deposited in Lake Gosiute indicate a great change in the lacustrine system throughout its history. The lithologies of the Luman, Tipton, and Wilkins Peak Members of the Green River Formation suggest that Lake Gosiute shifted from a freshwater to a saline lake, characterized by the occurrence of oil shales and evaporite deposits. The final stage of the lake represents a shift back to freshwater conditions with the deposition of the Laney Member.

I propose to study the relationships between lacustrine facies, stratal geometries, changing paleohydrology, and clastic provenance across the saline/freshwater transition in the Laney Member to draw conclusions about the relative contribution of climate and tectonics to the change in lake type. The preservation of the saline/freshwater transition provides and opportunity to examine stratigraphic relationships in a changing lacustrine system. Within this stratigraphic framework, geochemical analysis of lacustrine carbonates and clastic fill will indicate any changes in paleohydrology with respect to the specific clastic provenance. Geochemical trends will be reviewed and combined with previously documented climatic and tectonic interpretations to create a model for lacustrine stratigraphic packaging in a variable system. 

AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid