Significance of seismic reflections beneath a tilted exposure of deep continental crust, Tehachapi Mountains, California

Abstract

The focus of this article is a process whereby lower crustal crystalline and schistose rocks can rise to the surface, with the Tehachapi Mountains in California being the case in point. Integrated geophysical and geological studies by the CALCRUST program have produced a cross section through this post-Mid-Cretaceous structure and suggest a general model for its development. It seems that during Late Cretaceous Laramide subduction the protolith of the schist was thrust eastward beneath the Mojave. Along this portion of the Cordilleran batholithic belt the subduction was evidently at very low angles. The bottom of the batholith was removed and replaced by a thick section of schist, fluids from which weakened the overlying batholith. This thickened crust collapsed by horizontal flow in the schist and faulting of the upper crust into flat-lying slabs. When emplacement of the schist ended in latest Cretaceous/earliest Paleocene, the underlying mantle rose, compensating for the extension and providing material for magmatic underplating. -from Authors