Abstract Over 165 species of megainvertebrates, mostly mollusks, from the lowest three (of approximately 17) emergent marine terraces along the southwestern coast of Santa Barbara County, California, provide the basis for both paleoecological and paleoclimatic interpretation. Most of the fossiliferous exposures on the two lowest terraces at Canada de Alegria, Gaviota, and Arroyo Hondo are situated at or very near to the original shoreline angle (i.e., base of the fossil sea cliff) of their respective terraces, physically constraining any interpretation of their depositional setting. The overall composition of their faunas, however, suggests sources from several near-shore marine habitats, all at intertidal to shallow inner sublittoral depths (0 to 18-27 m). Only the sandy bottom faunas from localities at Cojo Bay differ, representing a position about 700 to 750 m from shore and a water depth of about 15 m. Composite faunas from localities on the first terrace at Cojo Bay, Gaviota, and Arroyo Hondo, and from the second terrace at Canada de Alegria contain from four to 12 extralimital northern species each, indicative of slightly cooler water paleoclimatic conditions, comparable to those occurring today in the vicinity of Monterey Bay, central California. The fauna from the third terrace at Arroyo Hondo contains four extralimital southern gastropods, whose zoogeographic ranges suggest a more southerly geographic equivalency and slightly warmer water conditions, comparable to those occurring today between San Diego, California, and Ensenada, Baja California. On the basis of terrace mapping, uranium-series age estimates of bones, amino-acid racemization and epimerization analyses of bivalve mollusks, long-term uplift studies, and the zoogeographic signatures of the terrace faunas, the three lowest terraces are assigned ages of 85 to 80 ka (Cojo Bay, Gaviota, and lower Arroyo Hondo localities), 105 to 100 ka (Canada de Alegria second terrace locality), and 130 to 120 ka (Arroyo Hondo upper terrace localities), correlative with dated sea-level highstands recorded elsewhere as reef terraces, and in deep-sea sediments as marine oxygen isotope substages 5a, 5c, and 5e, respectively.

Abstract Amino-acid and oxygen isotope data for fossils from terraces of the Palos Verdes Hills and San Pedro areas in Los Angeles County, California, shed new light on the ages of terraces, sea-level history, marine paleotemperatures, and late Quaternary tectonics in this region. Low terraces on the Palos Verdes peninsula correlate with the ∼80-ka and ∼125-ka sea-level highstands that are also recorded as terraces on other coasts. In San Pedro, the Palos Verdes sand (the deposit on what is mapped as the first terrace by Woodring and others, 1946) was previously thought to be a single deposit; amino-acid, oxygen isotope, U-series, and fauna] data indicate that deposits of two ages, representing the 80-ka and 125-ka highstands occur within this unit. Oxygen isotope data show that on open, exposed parts of the Palos Verdes peninsula, ocean waters during the 125-ka highstand were cooler than present (by about 2.3-2.6°C) similar to what has been reported for other exposed coastal areas in California. In contrast, in the protected embayment environment around San Pedro, water temperatures during the 125-ka highstand were as warm or warmer than present. During the 80-ka highstand, water temperatures were significantly cooler than present even in the relatively protected embayment environment of the San Pedro area. Late Quaternary tectonic-uplift rates can be calculated from terrace ages and elevations. Correlation of the lowest terraces around the Point Fermin area shows that the Cabrillo fault has a late Quaternary vertical-movement rate of 0.20 m/ka, based on the difference in uplift rates on the upthrown and downthrown sides of the fault. Elsewhere in the Palos Verdes Hills-San Pedro area, late Quaternary uplift rates vary from 0.32 m/ka to possibly as high as 0.72 m/ka. These rates, which reflect vertical movement on the Palos Verdes fault, are in broad agreement with estimated Holocene vertical rates of movement determined for offshore portions of the fault.