Earth materials and structures in the El Casco quadrangle provide considerable information about the late Cenozoic geologic evolution of southern California’s Inland Empire region (fig. 2). Important structural and stratigraphic elements include (1) m
. Geologic and geophysical maps of the El Casco 7.5??? quadrangle, Riverside County, southern California, with accompanying geologic-map database. 2015-01-01.