Structure of the Laramide Wind River Uplift, Wyoming, from Cocorp deep reflection data and from gravity data

Abstract

The question of the structure of the Wind River uplift, a Laramide foreland structure in Wyoming, has been answered by Consortium for Continental Reflection Profiling (Cocorp) deep crustal reflection profiling and by gravity interpretation. Wyoming uplifts are asymmetrical anticlines whose steep limb is commonly cut by a reverse fault or thrust. If the thrust continues into the crust with low dip, the uplift is caused by horizontal movements; and if the fault steepens into a high‐angle reverse fault in depth, the uplifts are caused by vertical movement. The Wind River uplift is the largest of the Laramide structures in Wyoming, and the thrust fault has 14 km of vertical separation and 26 km of horizontal separation. About 168 km of crustal reflection profiling has been completed by Cocorp across the uplift. The Wind River thrust fault generates a continuous reflection from near the surface to a depth of about 24 km, and the thrust appears as a complex zone of faults. Apparent dip of the thrust is 30°–38°, and true dip may be up to 48°. Interpretation of deep crustal reflections is complicated by the presence of multiple reflections. A structure whose complexity approaches that of basement outcrops is found in the deep crust. Gravity modeling also suggests that the fault dips moderately and that dense rocks are uplifted in the deep crust. The Moho does not seem to be presently displaced by faulting. The crust in the Wind River uplift began to deform by large‐scale folding and then broke and faulted as a rigid slab. Faulting is caused by crustal shortening from compression that is related to plate movements.