Geologic Map of the San Emigdio Mountains, Southern California

Abstract

New and existing geologic mapping and geochronology of the San Emigdio Mountains are compiled in a 1:40,000 scale map, establishing the framework for recently published and ongoing studies of Cretaceous assemblages belonging to the Sierra Nevada batholith and the Late Cretaceous San Emigdio Schist. Basement exposures of the San Emigdio Mountains are subdivided into four principal fault-bounded assemblages: (1) mid- to Late Cretaceous shallow-level granitoids and Paleozoic to Mesozoic metamorphic pendant rocks of the Pastoria plate; (2) Early to mid-Cretaceous deep-level intrusives of the Tehachapi-San Emigdio complex; (3) mid-to Late Jurassic gabbro, tonalite, ultramafic rocks, and framework basalts of the Western San Emigdio mafic complex; and (4) the Late Cretaceous San Emigdio Schist. The field relations summarized here, when viewed in a regional context, constrain the lateral extent of major Laramide detachment systems (the Pastoria and Rand faults) that were active during Late Cretaceous extensional collapse of the southern Sierra Nevada batholith and adjacent Mojave Desert area and document a highly dismembered and deeply exhumed ancient flat slab system.

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