Cocorp Deep Seismic Profiles Across the Wind River Mountains, Wyoming
R.W. Allmendinger, L.D. Brown, J.E. Oliver, S. Kaufman, 1983. "Cocorp Deep Seismic Profiles Across the Wind River Mountains, Wyoming", Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces, A. W. Bally
Download citation file:
The origin of basement uplifts in the Laramide province has long been a major controversy in the tectonics of the western United States. Surface geology on a regional scale (Figure 1) has emphasized the diversity of fault trends and orientations of uplifts, resulting in interpretations favoring dominantly vertical uplift (Prucha et al, 1965; Stearns, 1971). Others working with the same data base have concluded that horizontal compression was more important (Berg, 1962; Blackstone, 1963; Sales, 1968). Because the Laramide deformation occurred 1,000 to 1,500 km (621 to 932 mi) from the coeval plate margin along the western margin of North America, resolution of this controversy has important implications for the dynamics of plate interactions and the deformation of continental crust.
The Wind River Mountains are the largest Laramide uplift in Wyoming. The structure is a northwest trending, asymmetric feature, approximately 220 km (137 mi) long and 70 km (43 mi) wide. On the northeast side, Paleozoic shelf sediments, resting unconformably on Archean crystalline basement, dip gently to the northeast into the Wind River basin. The southwest side of the uplift is a northeast-dipping reverse fault, as shown by surface mapping, industry and government boreholes, and industry seismic reflection data (Berg, 1962; Royse et al, 1975). The minimum vertical structural relief between the Precambrian in the high peaks of the Wind River Mountains and the bottom of the Green River basin to the southwest is about 13 km (8 mi).
The Archean rocks consist of migmatites from deeper crustal levels now exposed in the core of the uplift north of the COCORP profiles, and at the south end in the vicinity of the seismic lines, granitic intrusions into gneisses and schists that represent shallower levels of the crust. These supracrustal rocks, which include iron formation, metaandesite, and metagraywacke, are steeply dipping and strongly folded. Condie (1972) suggested that an Archean greenstone belt and suture zone is located in the region beneath the COCORP profiles.