--> Abstract: Sedimentation and Subsidence in the Pennsylvanian and Permian Oquirrh-Wood River Basin, by J. K. Geslin, J. B. Mahoney, and B. R. Burton; #90993 (1993).

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GESLIN, JEFFREY K., University of California, Los Angeles, CA, PAUL KARL LINK,* Idaho State University, Pocatello ID, J. BRIAN MAHONEY, University of British Columbia, Vancouver, British Columbia, Canada, and BRADFORD R. BURTON, University of Wyoming, Laramie, WY

ABSTRACT: Sedimentation and Subsidence in the Pennsylvanian and Permian Oquirrh-Wood River Basin

Strata of the Middle Pennsylvanian to Lower Permian Oquirrh-Wood River basin (OWRB) comprise an overlap assemblage unconformably above the Antler orogenic belt and flysch trough/starved basin in northwestern Utah, northeastern Nevada, and south-central Idaho. A Desmoinesian uplift east of the OWRB supplied distinctive chert-pebble conglomerate of the lower Sun Valley Group and parts of the Oquirrh Formation, which was reworked progressively southward, and is recognized as far south as the Idaho-Utah border, in strata as young as Virgilian.

Virgilian to Leonardian rocks are represented by fine-grained mixed carbonate-siliciclastic turbidites that are widely distributed in the OWRB. These rocks contain north-derived cratonal, well-sorted subarkosic and quartzose sand and silt intimately mixed with arenaceous micritized skeletal material and peloids. The Snaky Canyon Formation in east-central Idaho and the Oquirrh Formation in the Deep Creek Mountains, plus newly discovered outcrops of foetid bioclastic wackestone, an eastern facies of the Eagle Creek Member, Wood River Formation, represent the carbonate platform. Intimate mixing of the two fractions suggests that they were either mixed during turbidity current transport or during residence on one or more mixing shelves above storm-wave base. Sediments ultimately were depo ited in carbonate-siliciclastic ramp systems (bulk of the Sun Valley Group and Oquirrh strata in the Sublett and Cassia mountains). Trace-fossil assemblages in ramp strata suggest that bottom water at times was anoxic, and that turbidity currents introduced oxygenated water, which fostered episodic benthic activity.

Subsidence of an integrated OWRB may have been caused by continental margin tectonism to the west involving an "elevated rim" and local reactivation of earlier, Antler-age structures.

AAPG Search and Discovery Article #90993©1993 AAPG Rocky Mountain Section Meeting, Salt Lake City, Utah, September 12-15, 1993.