Reconciling along-strike disparity in slip displacement of the San Andreas fault, central California, USA

Abstract

The correlation of the ca. 23 Ma Pinnacles and Neenach volcanic complexes provides the most robust estimate on the timing and magnitude of Neogene right-lateral displacement on the San Andreas strike-slip fault system (California, United States). Displacement of ∼315 km has been applied rigorously along the plate margin to guide reconstruction of offset paleogeographic features. We present new detrital zircon U-Pb geochronology from the La Honda and western San Joaquin basins to document sediment provenance and reevaluate compositional constraints on a hypothesized key cross-fault tie (i.e., Castle Rock−Recruit Pass submarine fan system). Whereas the Upper Oligocene−Lower Miocene Vaqueros Formation of the La Honda basin was likely recycled from or shared a similar southern Sierra Nevada−western Mojave source with the underlying Eocene stratigraphy, we found that the Temblor Formation of the central Temblor Range (e.g., Recruit Pass submarine fan) was derived directly from Late Cretaceous northern Salinian basement. Furthermore, the Carneros Sandstone of the northern Temblor Range had a central Sierra Nevada batholith source that was likely recycled during early Miocene unroofing of the underlying stratigraphy. Conversely, strata of the southwest San Joaquin basin have provenance characteristics that match more closely with those of the La Honda basin. Our data preclude a contiguous Castle Rock−Recruit Pass submarine fan system across the San Andreas fault. These relationships are resolved by restoring the ca. 105−100 Ma basement of the northernmost Salinian block an additional ∼45 km or greater farther south relative to the Sierra Nevada batholith during late Oligocene−early Miocene time. Inconsistency in displacement along the San Andreas fault with the coeval correlation of the Pinnacles−Neenach volcanic complex is reconciled by postdepositional Miocene−Quaternary off-fault NW-SE structural shortening via major thrusts and/or transrotation of the Tehachapi block, in combination with extension of the northern Salinian block. This additional displacement reduces the need for pre−28 Ma slip on the San Andreas or predecessor faults to resolve Cretaceous through Eocene cross-fault relationships and reconciles an early Miocene discrepancy with Pacific−North America relative plate motion. This study highlights the fact that displacement histories of major strike-slip faults are divergent across changing structural domains, and recognition of slip disparities can constrain the magnitude of deformation.