380 Tectonophysics, 52 (1979) 380 0 Elsevier Scientific Publishjng Company, Amsterdam - Printed in The Netherlands

ANOMALOUSLY HIGH UPLIFT RATES ALONG THE VENTURA-SANTA BARBARA COAST, CALIFORNIA - TECTONIC IMPLICATIONS

J.F. WEHMILLER I, A. SARNA-WOJCICK~ 2, R.F. YERKES 2 and K.R. LAJOIE ’

’ University of Delaware, Newark, Del. I9711 (U.S.A.) 2 U.S. Geological Survey, Menlo Park, Calif. 94025, (U.S.A.)

(Accepted for publication May 22, 1978)

ABSTRACT

The NW-SE trending segments of the California coastline from Point Arena to Point Conception (500 km) and from Los Angeles to San Diego (200 km) generally parallel major right-lateral strike-slip fault systems. Minor vertical crustal movements associated with the dominant horizontal dis- placements along these fault systems are recorded in local sedimentary basins and slightly deformed marine terraces. Typical maximum uplift rates during Late Quate~~ time are about 0.3 m/ka, based on U-series ages of corals and amino-acid age estimates of fossil mollusks from the lowest emergent terraces.

In contrast, the E-W-trending segments of the California coastline between Point Canception and Los Angeles (200 km) parallel predominantly northward-dipping thrust and high-angle reverse faults of the western Trans- verse Ranges. Along this coast, marine terraces display significantly greater vertical deformation. Amino-acid age estimates of mollusks from elevated marine terraces along the Ventura-Sand Barbara coast imply pompously high uplift rates of between 1 and 6 m/ka over the past 40 to 100 ka. The deduced rate of terrace uplift decreases from Ventura to Los Angeles, con- forming with a similar trend observed by others in contemporary geodetic data.

The more rapid rates of terrace uplift in the western Transverse Ranges reflect N-S crustal shortening that is probably a local accommodation of the dominant right-lateral shear strain along coastal California.