STRUCTURAL AND TECTONIC EVOLUTION OF THE CHEROKEE RIDGE ARCH, SOUTH-CENTRAL WYOMING: IMPLICATIONS FOR RECURRING STRIKE-SLIP ALONG THE CHEYENNE BELT SUTURE ZONE

The Cherokee Ridge arch is an east-west trending structure that separates the Washakie Basin of south-central Wyoming from the Sand Wash Basin of northwestern Colorado. It is characterized by a distinct east-west trending lineament on Landsat images and a zone of NW-SE striking, en echelon, high-angle faults that cut Upper Cretaceous to Miocene age sedimentary rocks. The lineament is interpreted to be the surface expression of a buried suture zone, the Cheyenne belt, which separates Proterozoic crust of the Colorado Province from Archean crust of the Wyoming Province. This structure has undergone repeated periods of strike-slip movement since Upper Cretaceous time and possibly before. The resulting surface and near surface structures along the Cherokee Ridge arch may be explained by periodic strike-slip motion along this suture zone. Left-lateral motion took place during the Late Cretaceous and early Tertiary as the area was under a compressional tectonic regime during the Laramide orogeny. The left-lateral shear zone represents a tear fault accommodating westward-directed thrusting and uplift of the Rock Springs uplift as the Colorado Plateau rotated clockwise at the end of the Laramide. Right-lateral motion took place after the Miocene as the Colorado Plateau rotated to the west relative to the more stable Wyoming province during Tertiary crustal extensional events. Surface structures observed along the arch are related to this most recent period of wrenching.