Detailed studies of emergent marine terraces in south-central coastal California provide new data for assessing the nature and rates of late Quaternary uplift along the Pacific-North American transpressional plate margin west of the San Andreas fault. Between Morro Bay and the Santa Maria Valley, remnants of at least 12 marine platforms are present. The ages of the lowest two platforms (∼80 ka and —120 ka) are well constrained by uranium-series ages, amino-acid racemization analyses, and paleoclimatic analyses of invertebrate faunal assemblages. Uplift rates based on the present altitude of the 120-ka terrace in this region range from 0.06 to 0.23 m/ka. The rates of uplift change abruptly across several fault zones that intersect the coast and thus provide a measure of the vertical component of slip on these faults. Based on the assumption of constant uplift, we estimate that paleosea level during the ∼80-ka high sea stand in this region was —4±1 m (relative to present sea level).

Near San Simeon, flights of four and five marine terraces are mapped to the northeast and southwest, respectively, of the northwest-trending San Simeon fault zone, a predominantly right-lateral strike-slip fault with a slip rate of 1 to 3 mm/yr. We estimate the ages of these terraces to be 60 or 80 ka, 80 or 105 ka, 120 ka, 210 ka, and 330 ka. Outside of the fault zone, the spatial distribution and present altitudes of the terraces indicate relatively uniform coastal-uplift rates of approximately 0.17 m/ka southwest and 0.16 m/ka northeast of the fault. The uplift rate for the uplifted and deformed areas within the fault zone is approximately 0.24 m/ka.