Modeling the relative influence of environmental controls on marine terrace widths

Abstract

Improved understanding of marine terrace development and morphology can provide better estimates of historical sea levels and tectonic uplift rates. Using a numerical model, this study explored the relative influence of environmental controls on late Pleistocene marine terrace widths on San Clemente Island (SCI) and in the Santa Cruz region (SCZ) in southern and central California, respectively. The model was calibrated/validated based on SCI and SCZ terrace observations using digital elevation models (DEMs), modeled nearshore wave climate, as well as data from existing SCI and SCZ marine terrace studies. In total, 648 simulations were conducted considering a range of wave height decay rates, rock resistance, initial topographic slope, and tectonic uplift rates. The model outcomes were generally consistent qualitatively with observations of SCI and SCZ terrace widths from published work and the DEMs presented here. Modeled terrace widths increased with decreasing topographic slope and increasing tectonic uplift rates; terrace widths were less well correlated with variations in wave and rock strength parameters in this study. Overall, the results suggest that topographic slope and tectonic uplift rates influence terrace widths more than wave- and rock-related properties. Some of the model assumptions and modeling outcomes contrast with existing rock coast and marine terrace studies, and additional research is necessary.