Grey Layers in Santa Barbara Basin: measures of earthquake frequency

Will Berelson, Laura Morine, & Nick Rollins

Published 2015, SCEC Contribution #6062

We have been studying the geochemical nature of grey layers found frequently in Santa Barbara Basin laminated sediment cores. These grey layers have been considered to represent flood deposits as they contain clays and many layers are correlated across the basin. However, we find that many layers are NOT correlated across the basin and think this argues for a submarine landslide source rather than flood. Further, we find marine fossils within the grey layer, suggesting marine source. The grey layers that we've examined (8 of them) are very consistent in terms of carbon content and inorganic and organic C isotope value. Relatively few 14C ages indicate that grey layer Corg is a few hundred years older than surrounding Corg but grey layer Cinorg is 4,000-7,000 years older than surrounding Cinorg. This observation, and the light 13C isotopic composition of the Cinorg are difficult to reconcile with either a flood or submarine landslide source. Organic compound analysis is underway.

Citation
Berelson, W., Morine, L., & Rollins, N. (2015). Grey Layers in Santa Barbara Basin: measures of earthquake frequency. Poster Presentation at 2015 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Forecasting and Predictability