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The tectono-stratigraphic evolution of the Palos Verdes Peninsula, southern California

Brian Olson

Published 2007, SCEC Contribution #6307

Lying along the westernmost border of the Los Angeles Basin, the Palos Verdes Peninsula provides a unique opportunity to examine the complex tectono-stratigraphic history of the Los Angeles Basin/Inner Borderland region. During the Mesozoic and early Cenozoic (Paleogene), western North America was the site of a convergent margin, where the Farallon plate was subducted beneath the western edge of the North American plate. One of the main expressions of this subduction is the Catalina Schist, which forms the basement rock of the Palos Verdes Peninsula. About 28 Ma, the northern end of the East Pacific Rise spreading center encountered the subduction zone. Through a process of microplate capture and stalling of Farallon plate subduction, the convergent margin gradually evolved into a transform plate boundary between 28 and 18 Ma.

This episode of microplate capture initiated the great Miocene transrotation of the Western Transverse Ranges crustal block and subsequent development of detachment faulting (~18 – ~12 Ma). This colossal rotation resulted in tectonic denudation of the Catalina Schist and the initial opening of the Los Angeles Basin/Inner Borderland along the releasing bend of the nascent transform system (early San Andreas fault system). In the Palos Verdes area, basin formation accommodated deposition of the San Onofre Breccia and Monterey Formation and triggered decompression melting and magmatic intrusion and extrusion of volcanic rocks.

Transtensional rifting continued to open and enlarge the Los Angeles and Inner Borderland sedimentary basins until the initiation of the modern strand of the southern San Andreas Fault system at ~6 Ma that formed in response to the easterly shift of the Pacific-North American plate boundary. The modern transpressional regime was established as a restraining bend in southern California that deformed and uplifted the deposits in the older depositional centers, including the Palos Verdes Peninsula.

Olson, B. (2007). The tectono-stratigraphic evolution of the Palos Verdes Peninsula, southern California. In Olson, B., , & (Eds.), Geology and Paleontology of Palos Verdes Hills, California: A 60th Anniversary Revisit to Commemorate the 1946 Publication of U.S. Geological Survey Professional Paper 207, (, pp. 23-40) , :