Stratigraphy and Paleogeographic Setting of Paleozoic Rocks in the San Bernardino Mountains, California

Abstract

Extensive exposures of pre-Mesozoic metasedimentary rocks are present in the San Bernardino Mountains. Overlying Precambrian basement are quartzite-dominated sequences previously correlated with late Precambrian and Early Cambrian miogeoclinal strata of the Johnnie Formation, Stirling Quartzite, Wood Canyon Formation, Zabriskie Quartzite, and Carrara Formation. Overlying is a thick section of carbonate rocks previously lumped into the Furnace Limestone of Carboniferous age. During the last decade extensive detailed mapping and chemical and paleontological data have shown that the sequence can be subdivided and correlated with the Cambrian Bonanza King and Nopah formations, the unconformably overlying Sultan Limestone of Devonian Age, Mississippian Monte Cristo Limestone, and the unconformably overlying Bird Spring Formation of Pennsylvanian through Permian age. Ordovician and Silurian strata have not been recognized in the area. The carbonate strata are identical to cratonal and transitional miogeoclinal strata exposed in several ranges in the Mojave Desert region, and were deposited in a shallow-marine environment. Regional isopachous and facies trends originally extended southwest across the Mojave, and suggest a westward bulge in the continental margin prior to Mesozoic truncation and compressional tectonics.