--> Abstract: The Relationship between Thrust Loading, Sediment Loading, and Subsidence in the Distal Portion of the Upper Cretaceous Foreland Basin of Wyoming, by W. J. Devlin, C. A. Shaw, K. D. Ehman, and F. B. Zelt; #91012 (1992).

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ABSTRACT: The Relationship between Thrust Loading, Sediment Loading, and Subsidence in the Distal Portion of the Upper Cretaceous Foreland Basin of Wyoming

DEVLIN, WILLIAM J., C. A. SHAW, K. D. EHMAN, and F. B. ZELT, Exxon Production Research Company, Houston, TX

Subsidence in the Upper Cretaceous foreland basin of Wyoming was caused in part by thrust emplacement and flexural loading in the Idaho-Wyoming thrust belt. In the proximal foreland, three subsidence cycles are present consisting of an initial high subsidence phase followed by a phase with lower subsidence rates. These subsidence cycles correspond to periods of thrusting and relative tectonic quiescence in thrust belt. Other subsidence uplift events on geohistory plots are related to Laramide tectonic movements.

An analysis of tectonic subsidence at a locality in the distal foreland basin also indicates several accelerations in subsidence rate. However, these increases in subsidence do not correspond to times of thrust emplacements and are actually out-of-phase with these movements. Although a visco-elastic response to thrust loading may be evoked to explain these observations, we interpret the increases in subsidence as the result of flexural loading of an elastic, distal foreland basin by prograding sediment wedges. In the Wyoming foreland, large-scale progradation of sediment from more proximal portions of the basin resulted from decreased basin accommodation and high sediment supply during (1) periods of relative tectonic quiescence in the thrust belt, and (2) periods of uplift associated with intra-foreland Laramide structural movements. Accelerations of subsidence rate in the distal foreland correspond to these times of progradation. The observed subsidence events in the outer foreland can be explained in terms of the flexural response of this part of the basin to the load of the prograding sediment wedge.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)