Late Mesozoic and Cenozoic tectonic history of south central California

Publisher Website
Google Scholar
Abstract
The late Mesozoic‐Cenozoic history of south central California is punctuated by at least five major tectonic events. The oldest of these involves Late Cretaceous drag folding and thrusting of epizonal shelf sediments westward over and to the north along the rising eastern margin of the Peninsular Ranges Batholith. These overthrusts, with associated drag folds and nappes, form imbricate stacks of metasediments, slices of plutons, and mylonites which overlie a regional core of Cretaceous granitic plutons of the Peninsular Ranges Batholith. A second, distinct kind of epizonal, low‐temperature crustal displacement includes an episode of mid‐Tertiary detachment faulting and folding. This represents the westerly extension of the detachment terrane of eastern California and western Arizona and Utah, superimposed upon the Cretaceous structural features, The mid‐Tertiary motions involve major E‐W extension and N‐S compressive strain, with formation of east‐trending antiformal “core complexes,” remarkably parallel to a pervasive set of fold axes and B‐lineations formed in the Cretaceous thrusting and folding. All of these features are repeatedly segmented and displaced by step‐faulting as sial in the Salton Trough is fragmented and depressed 5 to 10 km below sea level at intervals throughout the Cenozoic. The irregular step‐faulted interface of the Peninsular Ranges Batholith and Salton Trough is accentuated by a series of NE to SE striking left‐lateral and dipslip faults with displacements of several to 10 kilometers. These appear to both predate and occur during movements along the San Andreas system. Pliocene‐Pleistocene right‐lateral faulting, a younger extension of the San Andreas displacements north of the Transverse Ranges, has broken and displaced all older structural features, with total net slip in south central California of perhaps 300 km. Total right‐lateral slip along the several strands of the San Andreas system are measurable via reconstruction of the mosaic of numerous older, predominantly E‐W trending linear elements, mid‐Tertiary antiforms, and Cretaceous and older rocks. Right‐lateral strain on the San Andreas appears to either alternate with or to be a byproduct of N‐S compressional strain from the Pleistocene to the present. A resultant effect is a large family of E‐W trending folds and fault scarps in Plio‐Pleistocene sediments.