Geology of the Tunis-Pastoria Creek area, Kern County, California

Abstract

The geology of the Tunis-Pastoria Creek area, located approximately thirty miles southeast of Bakersfield, California, is rather simple from a regional standpoint. It more closely resembles the geology of the eastern edge of the San Joaquin Valley than that of the Coast Range province to the west. In the area mapped, pre-Tertiary crystalline rocks of the Tehachapi Mountains are overlain with a depositional contact by Tertiary sedimentary and volcanic rocks. These Tertiary rocks range in age from Middle Eocene to Lower Pliocene. Extensive terrace deposits and tiled alluvial fans of Quaternary age record the more recent history of this part of the San Joaquin Valley. Structurally the area is characterized by strata that dip moderately to the northwest, and by two sets of faults, one trending roughly parallel and the other perpendicular to the strike of the beds. Movement along most of these faults is believed to be of the normal type. Folding is minor and limited primarily to phenomena associated with faulting. Structures have been complicated by repeated periods of uplift and subsidence that have given rise to numerous unconformities in the Tertiary section.