The Nitchie Shear Zone, Wyoming

Abstract

The Nitchie Shear Zone is a 400 mile long surficial and topographic anomaly extending from the Fontenelle reservoir region, in western Wyoming, east and northeastward, crossing the Casper Arch. It is easily recognized in the vicinity of Nitchie Gas Field in Sweetwater County, Wyoming, where it runs east to west across the northern plunge of the Rock Springs Uplift. The localized hydrologic environment associated with the Nitchie Shear Zone (NSZ) distinguishes this surficial feature from surrounding terrains and highlights the associated geologic and geomorphic characteristics. The linear geomorphic features that identify the NSZ transect structural features including the Rock Springs and Sweetwater Uplifts as well as the Casper Arch. At Pathfinder Reservoir, Precambrian rocks involved in the NSZ are well exposed with strong evidence of shear and related stress. Southwest of Pathfinder Reservoir the NSZ plunges into the Red Desert Basin where there is over 20,000 feet of Cambrian to Tertiary sediment above the Precambrian basement. Here, the surficial characteristics of the NSZ continue indicating near vertical faulting and fracturing propagates from basement to the surface. Similarly, the surficial expression of the NSZ along the 450 mile path from the western Green River Basin to the western side of the Powder River Basin crosses basin axes, numerous folds and complex structural terrains.

AAPG Datapages/Search and Discovery Article #90193 © 2014 Rocky Mountain Section AAPG Annual Meeting, Denver, Colorado, July 20-22, 2014