Preliminary geologic map of the Jeffrey City quadrangle, Fremont County, Wyoming

A classic Laramide anticline is truncated by more recent subsidence on the south Granite Mountains fault system south of Jeffrey City, Wyoming. Petroleum and uranium production have taken place in this vicinity district. Rock formations ranging in age from upper Archean through Mesozoic have undergone intense Laramide folding and faulting, as the uplifting of Granite Mountains to the north took place. In Paleogene time, extensive erosion resulted in the partial destruction of the Sheep Creek Anticline and the deposition of thick sandstone and conglomerate units of the northeast Great Divide Basin.