The Miocene of the Palos Verdes Hills embraces a thickness of about 2,500 feet of rocks here designated as Monterey shale, and the base is not exposed in the region where the oldest beds crop out. Five main lithologic units are recognized, consisting, in ascending order, principally of silty shale, porcelaneous and cherty shale, phosphatic shale, diatomite, and radiolarian mudstone. Three local members are named and mapped, the lowest one of which includes three of the main lithologic units and also two named tuff beds. Foraminifera are found in all the main units and are assigned to nine faunal zones indicating a time range extending from early Middle Miocene to the top of the Upper Miocene, as these terms are generally used in Coast Range chronology. These beds overlap northward onto a schist basement of Franciscan (?) rocks, and this northward overlap apparently continues to the Torrance and Playa del Rey oil fields in the southern part of the adjoining Los Angeles Basin. Mollusks from detrital rocks at the base of the overlapping beds on the north slope of the hills represent a fauna that in many respects is a new one for the Coast Ranges, as it includes a number of tropical genera not heretofore recorded there.

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