Premium
Two‐Phase Exhumation of the Santa Rosa Mountains: Low‐ and High‐Angle Normal Faulting During Initiation and Evolution of the Southern San Andreas Fault System
Author(s) -
Mason Cody C.,
Spotila James A.,
Axen Gary,
Dorsey Rebecca J.,
Luther Amy,
Stockli Daniel F.
Publication year - 2017
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1002/2017tc004498
Subject(s) - geology , detachment fault , clockwise , trough (economics) , tectonics , fault (geology) , seismology , paleontology , pleistocene , isochron dating , thermochronology , metamorphic core complex , plate tectonics , fold (higher order function) , geochemistry , extensional definition , mechanical engineering , isochron , macroeconomics , economics , engineering
Low‐angle detachment fault systems are important elements of oblique‐divergent plate boundaries, yet the role detachment faulting plays in the development of such boundaries is poorly understood. The West Salton Detachment Fault (WSDF) is a major low‐angle normal fault that formed coeval with localization of the Pacific‐North America plate boundary in the northern Salton Trough, CA. Apatite U‐Th/He thermochronometry (AHe; n = 29 samples) and thermal history modeling of samples from the Santa Rosa Mountains (SRM) reveal that initial exhumation along the WSDF began at circa 8 Ma, exhuming footwall material from depths of >2 to 3 km. An uplifted fossil (Miocene) helium partial retention zone is present in the eastern SRM, while a deeper crustal section has been exhumed along the Pleistocene high‐angle Santa Rosa Fault (SFR) to much higher elevations in the southwest SRM. Detachment‐related vertical exhumation rates in the SRM were ~0.15–0.36 km/Myr, with maximum fault slip rates of ~1.2–3.0 km/Myr. Miocene AHe isochrons across the SRM are consistent with northeast crustal tilting of the SRM block and suggest that the post‐WSDF vertical exhumation rate along the SRF was ~1.3 km/Myr. The timing of extension initiation in the Salton Trough suggests that clockwise rotation of relative plate motions that began at 8 Ma is associated with initiation of the southern San Andreas system. Pleistocene regional tectonic reorganization was contemporaneous with an abrupt transition from low‐ to high‐angle faulting and indicates that local fault geometry may at times exert a fundamental control on rock uplift rates along strike‐slip fault systems.