Lasuen Bank is a prominent feature of the Continental Borderland located between Dana Point and the south end of Catalina Island. It is elliptical in plan, elongate NW-SE, and asymmetrical in profile. Rocks ranging in age from Middle Miocene to Late Pliocene are exposed over most of the Bank's surface. The most distinctive lithology present is contained in a group of sedimentary rocks very similar to the Altamira, Valmonte, Malaga, and Capistrana Formations cropping out on the nearby mainland. Abundant volcanic rocks are interpreted as interbeds within these sediments. There is no evidence to support the presence of "Franciscan" Basement. Rock fragments of this type are referred to the San Onofre Formation. Representatives of the Topanga, Repetto, and Pico Formations are lso present. Exposures become progressively younger toward the east. Lasuen Bank is a result of block faulting originating in the Late Pliocene or Early Pleistocene and continuing to the present. A system of fractures trending N 30° W is visible on profiles. Several terraces and associated features occurring down to 360 meters indicate the Bank was very near or above sea-level at least once during the Pleistocene.

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