Late Precambrian and Paleozoic strata of the Cordilleran continental margin (miogeocline) form a westward-thickening wedge of sedimentary rocks in the southern Great Basin region (Stewart, 1970). Facies boundaries and isopachs of these rocks can be traced across this region into the eastern Mojave Desert, southeastern California, where these older trends are crosscut by the younger, Mesozoic-age magmatic arc terrane (Fig. 1). Miogeoclinal rocks involved in the Cordilleran fold-and-thrust belt in the eastern Mojave Desert become more highly deformed and metamorphosed southwestward as the magnatic arc is approached.
The geologic complexity of the central and western Mojave Desert, however, has posed a major stumbling block in attempts to reconstruct the paleogeography and tectonic history of the southern part of the Cordilleran orogenic belt. In the central and western Mojave Desert, bed-rock exposures consist chiefly to Tertiary volcanic rocks and Mesozoic granitic rocks. Because of the lack of exposure of older rocks in this terrrane, the southwestward continuation of miogeoclinal facies and isopach trends and the timing and nature of structural events in this region are very poorly known in comparison to what is known about the eastern Mojave Desert region.