Tectonic and sedimentary evolution of the northern Green River basin, western Wyoming
Mark W. Shuster, James R. Steidtmann, 1988. "Tectonic and sedimentary evolution of the northern Green River basin, western Wyoming", Interaction of the Rocky Mountain Foreland and the Cordilleran Thrust Belt, Christopher J. Schmidt, William J. Perry, Jr.
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Studies of the provenances, facies, and subsidence histories of Upper Cretaceous and lower Tertiary strata in conjunction with flexural modeling document the tectonic origin and sedimentary evolution of the northern Green River basin in western Wyoming. The area evolved from being part of the Sevier foreland into a nonmarine intermontane basin with the uplift of the Wind River and Gros Ventre Ranges during late Cretaceous time, and by early Tertiary time, subsidence and sedimentation related to these uplifts dominated the northern Green River basin.
Sandstone compositions and paleocurrent data indicate an abrupt change in provenance at the beginning of Paleocene time, marking the progressive uplift and erosion of the Wind River and Gros Ventre highlands. Sandstones changed from dominantly sedimentary lithic compositions to dominantly feldspathic compositions when the crystalline core of the Wind River Range was breached. Similarly, paleocurrent trends changed from southeasterly flow directions southward and southwestward, as both the Gros Ventre and Wind River uplifts flooded the basin with detritus.
The alluvial sandstone architecture of Upper Cretaceous and lower Tertiary rocks was analyzed in order to document the interaction of allocyclic controls and depositional facies as related to the subsidence history of the basin. This approach proved to be successful only where complicating factors, such as climate and source lithology, could be adequately constrained. Analyses of facies within the lenticular sandstone and shale sequence (Campanian) and the Hoback Formation (Paleocene) suggest deposition during rapid subsidence. The alluvial architecture of Eocene strata (Pass Peak and Wasatch formations) of the Hoback area cannot be easily interpreted in terms of subsidence. Rapid subsidence is indicated for the LaBarge Member of the Wasatch Formation in the Big Piney-LaBarge area.
Subsidence analysis for the Hoback, Pinedale anticline, and LaBarge areas documents the patterns and timing of tectonically induced subsidence. A subsidence event occurring at approximately 120 to 115 Ma was probably related to thrusting in the Idaho-Wyoming thrust belt. Another subsidence event at approximately 90 Ma may indicate initial uplift of the Wind River block. The very rapid subsidence event in the Pinedale anticline area during Maastrichtian time is not evident in subsidence curves from the Hoback and LaBarge areas, and thus is probably a manifestation of loading by the Wind River thrust. Rapid subsidence during Paleocene time in the Hoback area is attributed to loading from the Darby thrust and Gros Ventre uplift.
Two-dimensional profiling of the northern Green River Basin shows that the basin can be effectively modeled as a flexural depression resulting from extrabasinal and intrabasinal loading on an elastic lithosphere. Two distinct models were used to confirm regional compensation and the flexural response to loading of the lithosphère. Modern basin geometry analysis tested for regional compensation by comparing modeled deflections with observed basin geometry for a given load configuration. Sediment thickness profiling was used to determine the maximum thickness of sedimentary rocks that could have accumulated in the tectonic depression resulting from Darby, Prospect, and Wind River thrusting (assuming instantaneous uplift and adequate sediment supply). Both models are consistent with the concept of basin-margin tectonic loading as the main cause of subsidence in the Green River basin.