The interaction of the Moxa Arch (La Barge Platform) with the Cordilleran thrust belt, south of Snider Basin, southwestern Wyoming
David H. Kraig, David V. Wiltschko, John H. Spang, 1988. "The interaction of the Moxa Arch (La Barge Platform) with the Cordilleran thrust belt, south of Snider Basin, southwestern Wyoming", Interaction of the Rocky Mountain Foreland and the Cordilleran Thrust Belt, Christopher J. Schmidt, William J. Perry, Jr.
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Interaction of the Rocky Mountain foreland and the Cordilleran thrust belt has taken place in the Snider Basin area, west of Big Piney, Wyoming. Here, the central segment (La Barge Platform) of the Moxa Arch, a Late Cretaceous, basement-cored uplift, plunges northwestward beneath, and disrupts the continuity of, the Darby, Hogs-back, and Prospect thrusts. Although to the north and south of the La Barge Platform, basement shortening appears to have been along low-angle thrust faults, this was probably not the case for the platform. The 2,600 m of west-verging structural relief along the southwest limb of the La Barge Platform occurs over about 5 km of horizontal distance and might be the result of shortening of the basement across a zone of discrete, closely spaced reverse faults, generally restricted to basement. This shear zone (here termed the La Barge shear zone) dips about 60°NE. Shortening in the basement appears to have been matched by shortening of the cover rocks along a pair of west-dipping reverse faults, the upper of which is the Tip-Top thrust. According to our interpretation, Tip-Top thrusting was synchronous with the emplacement of the La Barge Platform and thus predated the Hogsback thrust. Our work confirms earlier interpretations that the Darby and Prospect thrusts link in the subsurface below Snider Basin and continue to the south as the Hogsback thrust. According to our interpretation, Hogsback thrusting is a composite of Paleocene Prospect thrust movement and later Darby thrusting. In the area of the La Barge Platform, the Hogsback thrust was localized by following west-dipping Cretaceous beds on the monocline above the La Barge shear zone.