Abstract

The general east-west trend of the regional-scale, fault-related Casper Mountain uplift in central Wyoming reflects a preexisting Precambrian fabric along which there was Laramide compressional reactivation. Initial fault displacement on the south-dipping Casper Mountain fault zone probably predates displacement on the intersecting, northwest-trending, northeast-dipping Casper arch thrust that forms the northeastern border of the Wind River basin. Later phase, incremental, Laramide displacements occurred along both fault zones: left-oblique slip on the Casper Mountain fault zone, dip slip on the crosscutting Casper arch thrust. Basement-involved thrust generation of the subsidiary Laramide, northwest-trending Iron Creek and Emigrant Gap anticlines along the north (footwall) side of the Casper Mountain fault zone also occurred during this later phase Laramide deformation.

Perturbation of far-field, northeast-southwest, Laramide maximum horizontal paleostress trajectories (σ1) to local, nearly fault-normal orientation at Casper Mountain, together with strain partitioning, is proposed to explain the apparent coeval development of divergent hanging-wall and footwall, basement-involved, fault-related structures. This kinematic and dynamic interpretation may be applied conditionally to other east-west-trending Laramide uplifts in the central Rocky Mountain foreland province.

You do not currently have access to this article.