Precambrian and Paleozoic rocks occur in two major structural units in the Kern Mountains and Snake Range and in three major units in the Deep Creek Range. Correlation across the intervening Pleasant Valley of the thrusts that define these units can only be inferred. Rocks older than the Prospect Mountain Quartzite are regionally metamorphosed, and rocks as young as the Devonian Guilmette Formation have been subjected to low-grade, probable contact, metamorphism. Metamorphism is believed to be post-Paleozoic. These metamorphosed rocks acted as a rigid basement above which allochthonous rocks were deformed and thrust along several decollement toward the east-southeast.