Sedimentation in Nearshore Basins as Related to Paleoseismicity

Will Berelson, Alex Sessions, Josh West, & James F. Dolan

Published August 12, 2016, SCEC Contribution #6669, 2016 SCEC Annual Meeting Poster #311

The exceptional preservation and accumulation of Santa Barbara Basin (SBB) laminae has been exploited by a trove of scientists (Huselmann and Emery; Kolpack and Gorsline; Soutar; Fleischer; Thornton; Drake; Schimmelmann et al.; Kennett et al.; Behl et al. and many others) interested in resolving, at high-temporal resolution, the sedimentation history of this coastal site. Among the many curious aspects of SBB sedimentation is the relative importance of hemi-pelagic vs. mass movement contribution to the overall sediment package.

Visual characteristics of sediment has always been an important observation made by sedimentologists. The olive-dark gray package of SBB sediments, which upon closer inspection can show mm or sub-mm scale coupling of lighter and darker laminae, dominate Holocene sediments recovered in box, multi, gravity and piston cores (Behl and Kennett ). Sedimentologists who have worked on SBB cores have also noted the abundance of gray layers, distinctly lighter in color and massive, compared to the typical dark-olive laminated sediments. Described by Huselmann and Emery ( ) as distal turbidite deposits, Fleischer’s ( ) analysis of their grain size and mineralogy resulted in the interpretation that they formed from a suspension of silt-clay sized material discharged during a major flood event. Subsequent studies provided additional evidence in support this mode of formation (Thornton, Behl, Stein) and complementary work has tried to make the connection between flood layers and climate/precipitation (Schimmelmann, Li).

This poster takes another view of the relevance of flood layers in a deposit containing mainly hemi-pelagic laminated sediment. We are particularly interested in how the frequency of gray layers in SBB relate to paleoseismic events. Our first order interpretation is that gray layers are related to both seismicity and precipitation.

Key Words
paleoseismicity, marine sediments

Citation
Berelson, W., Sessions, A., West, J., & Dolan, J. F. (2016, 08). Sedimentation in Nearshore Basins as Related to Paleoseismicity. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Forecasting and Predictability (EFP)