FIGURE 3.3.-Geologic sketch map of California, showing distributionof principal basement rocks. Cenozoic cover not shown except for the Modoc Plateau, northeastern Sierra Nevada, Great Valley, and Santa Barbara-Ventura Basin. Based on U.S. Geological Survey (1966), Jennings and others (1977), and Ross (1934). Units: 1, Quaternary alluvium-shown only in Great Valley; 2, basement rocks concealed by thick Upper Cretaceous and Tertiary deposits in the Santa Barbara, Ventura, and Los Angeles Basins; 5, Franciscan assemblage of Lower Jurassic to Tertiary oceanic rocks; 9, Salinian block-dominantly Cretaceous plutons intruding metamorphic rocks of questionable age (Barrett Ridge slice [BRS], commonly shown as part of the Salinian block, is here shown as part of unit 11); 10, southern California batholith-dominantly Cretaceous plutons intruding sedimentary and volcanic rocks of Jurassic age and metamorphic rocks of mostly unknown age; 11, mainly Precambrian metamorphic and plutonic rocks, in part overlain by Paleozoic continental shelf deposits and intruded by Mesozoic plutons, locally underthrust in southwestern part of region by schist (similar in lithology to the Pelona Schist) of probable Cretaceous age.