From abstract: The Santa Monica Mountains lie only a few miles northwest of the city of Los Angeles and comprise one of the prominent structural features that adjoin the Los Angeles Basin, one of the most prolific oil-producing districts of California. Even though the eastern part of these mountains may yield no oil, information concerning the rock types, structural character, and detailed geologic history of this area should be of value to petroleum geologists. The area described in this report, which lies between Topanga Canyon on the west and the Los Angeles River on the east, presents a section of varied rock types including coarsely crystalline plutonic rocks, basic and acidic intrusive and pyroclastic rocks, metamorphic slate and schist, and a wide assortment of sedimentary rocks.