Basement-involved Contractional Wedge Structural Styles: Examples from the Hanna Basin, Wyoming

In a typical wedge structure developed in layered sedimentary rocks, displacement is transferred from a deep fault to a shallow fault. The deep and shallow faults dip in opposite directions and merge with one another to form a wedge-shaped indentor. Displacement within the wedge fault system is transferred vertically into structures overlying the faults instead of being transferred laterally toward the foreland as in a typical fault-bend fold. Wedge structures associated with basement-involved contractional uplifts are commonly observed where faults that uplift a basin margin emanate from competent basement rocks into layered sedimentary rocks within the basin. Two categories of basement-involved wedge structures have been identified based on the level of the wedge point with respect to the basement surface. In the first category, the wedge point occurs within the sedimentary section overlying the basement, and in the second category, the wedge point occurs within the basement material. Interpretations of both categories of basement-involved wedge structures imaged in long-offset seismic data from the Hanna Basin in south-central Wyoming are presented.