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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 79 (1995)

Issue: 9. (September)

First Page: 1377

Last Page: 1394

Title: Oblique Convergence During Northeast-Southwest Laramide Compression Along the East-West Owl Creek and Casper Mountain Arches, Central Wyoming

Author(s): Philipp C. Molzer, Eric A. Erslev (2)

Abstract:

Understanding the diversity of structural trends in the Laramide foreland of the conterminous United States is important to understanding the location, geometry, and fracturing of hydrocarbon reservoirs. East-west basement-cored arches in central Wyoming are oblique to the average northwesterly trend of foreland faults and folds. Tectonic models predict that these arches formed by one of the following mechanisms: north-south-directed thrust faulting; sinistral strike-slip faulting; or northeast-southwest-directed, oblique-slip thrust faulting. In the eastern Owl Creek Mountains, average slip directions given by slickenline directions trend from N37°E to N57°E. Geometric analysis of conjugate faults and stress inversion of minor fault data indicate nearly horizontal compression trending between N48°E and N65°E. In the east-west Casper Mountain structure, more limited minor fault data are consistent with the northeast-southwest compression seen in the eastern Owl Creek arch and indicate an additional stage of extension by normal faulting.

The northeast-southwest compression documented by minor faults suggests oblique thrusting with a component of sinistral strike-slip on the underlying, east-west-striking Owl Creek and Casper Mountain thrusts. In this area of the Laramide foreland, east-west arches probably formed during a single stage of oblique slip on thrust ramps connecting northwest-trending arch culminations. This conclusion indicates that trap geometries and reservoir characteristics of foreland hydrocarbon accumulations are dependent on their obliquity to the regional stress field.

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