Structural Features of Eastern Tejon Embayment from Available Seismic and Subsurface Data and Field Geology

Emery D. Goodman, Peter E. Malin

The temporal and spatial relationships of normal, thrust, and strike-slip faults in the eastern Tejon embayment were investigated, and an integrated study of new CALCRUST data, industrial seismic data, well data, and surface geology yielded a set of geologic cross sections and a detailed structure map. Buried normal faults, trending northeast, dominate the central embayment structure. At the basin margins, the normal faults are truncated by younger thrust faults.

The Springs fault zone is a complex subvertical fault with branching reverse faults. The White Wolf fault is probably segmented and multi-stranded. The active, lower angle segment of the White Wolf fault may be related to buried thrust faults west of uplifted Comanche Point. Thrust faulting also may explain the presence of exhumed normal faults at Comanche Point and in the Tehachapi foothills. These exhumed normal faults are probably late Oligocene to Pliocene.

The Tunis volcanics formed during a period of widespread late Oligocene-early Miocene volcanism in central California. Volcanism and the inception of normal faulting at Tejon embayment apparently predated the passing of the Mendocino triple junction. Younger volcanic rocks are also widely distributed, probably due to regional transtensions that occurred south of the Mendocino triple junction.

Seismic data suggest that the deepening of Tejon embayment occurred mainly during the late early and middle Miocene. Convergence beginning during the Pliocene-Pleistocene is consistent with other documented changes along the modern San Andreas fault.

AAPG Search and Discovery Article #91035©1988 AAPG-SEPM-SEG Pacific Sections and SPWLA Annual Convention, Santa Barbara, California, 17-19 April 1988.