This report is an evaluation of the petroleum potential of the Cenozoic sedimentary rocks of the Imperial Valley. The Imperial Valley is within a broad zone of faulting that may be termed the "San Andreas rift." Diastrophism has produced structures comparable to those which form the traps for petroleum in the oil fields of California adjacent to the San Andreas rift.

About 7,000 cu mi (29,170 cu km) of siliceous clastic sedimentary rocks has been deposited in the California part of this complex basin. About 22 percent is of marine origin, in an area of 3,200 sq mi (8,290 sq km). Included are 455 cu mi (190 cu km) of coarse-grained clastic rocks that contain 125 cu mi (520 cu km) of sandstone suitable for petroleum reservoirs, and 1,060 cu mi (4,420 cu km) of fine-grained clastic rocks that might be source rocks for petroleum. The oxidizing freshwater environment of the nonmarine sediments and the shallow-water and apparently sterile environment of the marine sediments explain the absence of evidence of petroleum in the exposed sedimentary strata and the exploratory wells. Except for an unusual and unique source of petroleum (detrital oil shale tra sported from the eroded oil shale deposits of Colorado, Utah, and Wyoming, and distilled by the Salton Sea geothermal feild), the possibility of discovering significant petroleum reserves in the Imperial Valley area appears to be very slight.