Structural Geology of Wind River Canyon Area, Wyoming

Abstract

The Wind River Canyon of Wyoming provides a structural cross section of the Owl Creek-Bridger uplift, and gives effective indication of the processes and stages by which Laramide deformation proceeded in this region. Exposures in the canyon area also indicate the roles of competency variations within the stratigraphic column in controlling pressure responses of different rock units. The Laramide faults and folds are in part reflections of these competency variations, and in part owe their trends to the resolution of the applied Laramide deformative forces. The structure of this canyon area is particularly interesting because of the illustrations it affords of the structural contrasts between the nature and origin of the primary inter-basin Owl Creek-Bridger uplift, and the secondary intra-basin ramp and other basin-mechanics products which feature the Bighorn Basin. The Owl Creek-Bridger uplift was initiated as an anticlinal fold by inter-basin competition early in Laramide deformation; and was subsequently ruptured by southward and slightly eastward crowding of the Bighorn Basin, relative to the Wind River Basin, as deformation progressed. The Boysen fault is a normal one, developed after the southward overthrusting was largely complete, and was due to the (relative) downdropping of the toe of the overthrust mass. Some additional post- oysen-fault thrusting is also indicated by the drag effects shown south of this fault. Post-Laramide dips in the adjacent Wind River Basin are interpreted as due to accentuation of initial depositional slopes after compaction under once-present sedimentary overburden.