Sedimentation and paleotectonics during mid-Miocene transrotation, Los Angeles and Ventura basins, southern California

Abstract

Early to Middle Miocene (Relizian through Luisian, ~17-13 Ma) crustal extension of the Los Angeles and eastern Ventura basin areas occurred during vertical-axis rotation (transrotation) of the western Transverse Ranges above the captured Monterey microplate. Detachment faulting, high-angle faulting, upper-plate block rotation around horizontal axes and isostatic uplift of the lower plate produced accommodation space for diverse depositional systems. Synextensional strata consisting of complexly interstratified siliciclastic and biogenic sedimentary rock and localized thick rift-related volcanic rock define multiple depocenters in sub-basins characterized by rapid lateral and vertical facies changes. High-angle and low-angle normal faults, as well as through-going strike-slip and transfer zones define sub-basin margins. Palinspastic reconstruction of Topanga sub-basins and related offshore features suggest a network of coeval normal and transfer zones that define multiple deforming blocks that moved along complex arc paths during clockwise transrotation. Transrotation led to extension and basin development both along the primary breakaway zone (what is now near the southern edge of the western Transverse Ranges) and areas to the southeast toward the unrotated upper plate of the Peninsular Ranges. Basin subsidence and filling were especially rapid near the hinge point in the area that would later become the Los Angeles basin and its margins.

AAPG Datapages/Search and Discovery Article #90372 © 2020 AAPG Pacific Section Convention, 2020 Vision: Producing the Future, Mandalay Beach, Oxnard, CA, April 4-8, 2020 (Cancelled)