The Bakersfield Arch as an Integral Part of the Southern Sierra Nevada (SN) Uplift
Jason Saleeby and Zorka Saleeby
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena CA 91125
The Bakersfield Arch is an active epeirogenic uplift that initiated in Plio-Pleistocene time. Facies changes across the Arch in Upper Cretaceous to Neogene strata differ from the current uplift, and reflect Late Cretaceous tectonic exhumation, and subsequent Cenozoic erosion and uplift of the adjacent SN. The southern SN batholith was exhumed to lower crustal depths in the Late Cretaceous due to Farallon plate subduction flattening beneath the Mojave arc segment. The adjacent forearc was likewise uplifted and eroded to basement. The W-SW trending hinge about which the batholith and forearc were tilted during exhumation/erosion passes beneath the Arch ~20 km south of its topographic axis. Late Cretaceous normal and strike-slip transfer faults in the basement were remobilized in the Neogene controlling extensional tectonism and subsidence within the San Joaquin basin (SJB). The sub-Eocene unconformity that is widespread along the eastern SJB can be mapped as a relict landscape surface along interfluves of the southern SN by geomorphic and He apatite thermochronometry. Provenance data on eastern SJB clasts coupled to SN basement geology indicates that the Tertiary basin edge ran well to the east of the current range front, lying above the relict landscape surface. Offsets in the relict surface mark late Neogene-Quaternary distributed extensional faulting of the basement. These structures continue westward as a dense network of faults cutting strata of the Arch. Mantle lithosphere of the southern SN region foundered in Pliocene-Quaternary time. Late Miocene-Pliocene accelerated subsidence in the Maricopa sub-basin, and late Pliocene-Quaternary Arch uplift/Tulare sub-basin subsidence are in accord with geodynamic modeling which couples epeirogenic subsidence and uplift through rolling hinge migration in response to lithosphere foundering and asthenosphere ascent. Such epeirogenic uplift and subsidence patterns extend to the eastern SN region and adjacent lake basins of the Owens-Indian Wells Valley region.
AAPG Search and Discovery Article #90076©2008 AAPG Pacific Section, Bakersfield, California