Isolated outcrops of deformed, regionally metamorphosed Paleozoic strata are scattered within the southeastern Mojave Desert region of California and western Arizona. These strata unconformably overlie a basement of Proterozoic crystalline rocks and are overlain in turn by metamorphosed Mesozoic sedimentary rocks. The strata can be correlated lithostratigraphically with the classic cratonal Paleozoic section of the western Grand Canyon, Arizona, and with nonmetamorphosed Paleozoic sections transitional between cratonal and miogeoclinal in the Ship, Marble, and Providence Mountains, California. The strata evidently were once continuous with Paleozoic epicontinental strata exposed throughout the southern Great Basin and Colorado Plateau.
Outcrops of Paleozoic strata and of the underlying Proterozoic basement in the southeastern Mojave Desert region define a terrane that has been disrupted by Mesozoic thrust faults and by Tertiary detachment faults but that nevertheless retain a gross paleogeographic coherence. This coherent terrane extends at least as far west and southwest as the Big Maria, Palen, and Calumet Mountains, and possibly beyond to include Paleozoic exposures in the San Bernardino Mountains and near Victorville. Poorly understood tectonic boundaries separate the area of paleogeographic coherence from known or suspected allochthonous terranes in the western Mojave Desert and the eastern Transverse Ranges.