The rocks in the map area are Cretaceous shales, N:iocene volcanic rocks, and a Pliocene(?) conglomerate. The Miocene volcanic rocks, basalt flows and tuffaceous rocks, correlate to the lower part of the total Miocene volcanic section. The flows can be distinguished petrographically by their olivine content, their plagioclase composition, and the size of the plagioclase phenocrysts. The volcanic rocks are probably related to the Nuocene volcanic rocks exposed in the Palos Verdes hills and surrounding areas. Post-Cretaceous deformation was followed by an episode of erosion, extrusion of the Miocene volcanic rocks, mild defornation of the Miocene rocks, partial truncation of the J-iocene rocks, deposition of the Pliocene conglomerate, and uplift and subsequent erosion of the Pliocene conglomerate.