Depositional Architecture and Provenance of the Petroliferous Upper Stevens Sand Deep-Marine Depositional System, Southern San Joaquin Basin, California: ABSTRACT

Abstract

Deep-marine sandstones of the upper Miocene Stevens Sandstone, derived from both easterly sierra Nevada and westerly Gabilan Range sources, were deposited by sediment gravity flows in the Bakersfield arch area of the southern San Joaquin basin. Access to previously unavailable proprietary 2-D and 3-D seismic data sets, calibrated by well-log and core data, permits a more complete understanding of the depositional architecture of this highly petroliferous, deep-marine depositional system. The Stevens interval consists of packages of thick siliciclastic units separated by thin, intervening biosiliceous shales. Seismically, the upper bounding surfaces of these shales represent major downlap surfaces. The structurally controlled Upper Stevens Sandstone is generally considered to be one of succession of high-density turbidity current deposits shed off the southern sierra Nevada. The Upper Stevens in the Bakersfield Arch area lacks a typical deep-sea fan morphology and cores do not display classic Bouma sequences. Slumping and debris flows appear to have significance as depositional processes. Furthermore, stratigraphic architecture suggests that a significant proportion of Upper Stevens coarse clastic sediment in the Bakersfield arch area may have been derived from the west side of the basin.