Extension of the Cordilleran Miogeosynclinal Belt to the San Andreas Fault, Southern California

Abstract

Correlations of marine sedimentary rocks in the San Bernardino Mountains and western Mojave Desert area with known uppermost Precambrian and some Paleozoic rocks of the southern Great Basin suggest that a nearly complete succession of Cordilleran miogeosynclinal rocks extends into southern California. Pre-Mesozoic rocks in the San Bernardino Mountains consist of (1) gneiss and schist of Precambrian age (in part older than 1,750 m.y.); (2) the Saragossa Quartzite, here considered to be latest Precambrian and Early Cambrian in age; and (3) the Furnace Limestone, the upper part of which is locally dated by megafossils as Mississippian and possibly Pennsylvanian or Permian but considered here to contain strata ranging in age from Early Cambrian to Permian(?). The Saragossa Quartzite contains distinct units that can be lithologically correlated confidently with parts of the uppermost Precambrian and Lower Cambrian sequence containing the Johnnie, Stirling, Wood Canyon, and Zabriskie Formations of the eastern Mojave Desert and the southern Great Basin. Some rock units on Quartzite Mountain in the western Mojave Desert are lithologically correlated with the uppermost Precambrian and Cambrian Wood Canyon, Zabriskie, Carrara, and Bonanza King Formations of the eastern Mojave Desert and southern Great Basin. The Cordilleran miogeosynclinal belt is obliquely truncated by the San Andreas fault in southern California; a displaced segment may occur in the Salinian block 450 km to the northwest. Cordilleran miogeosynclinal rocks also occur in northwestern Mexico east of the San Andreas fault, indicating a major change in trend of the geosyncline between the Great Basin and Mexico.