ALBERT

Description: We mapped, surveyed, and dated fluvial and marine terraces that cross the Santa Ynez River fault in southern California to document the timing, amount, and rate of deformation along the fault over the past 100 kyr. This submission includes terrace mapping, terrace elevation profiles, and terrace ages from luminescence and radiocarbon dating. These data were collected between March and October of 2019. Terraces were mapped on a 3-meter digital elevation model (DEM) derived from NOAA IfSAR data. Terraces were first mapped remotely using visual analysis of the DEM, historic air photos, and Google Earth. Remote mapping was then checked and refined in the field. Elevation surveys of the terrace surfaces were used to correlate fluvial terraces along the river and to identify and measure any terrace surface deformation. We performed the elevation surveys in the field with a Trimble GeoXH GPS, which after postprocessing, resulted in elevation data with a horizontal and vertical accuracy between 10 and 75 cm. For areas not accessible due to property restrictions, we used the NOAA IfSAR 3-m DEM to interpolate transects of fluvial terrace treads. Similarly, at the mouth of the Santa Ynez River on Vandenberg Air Force Base, we constructed profiles of the fluvial and marine terrace treads with a 1-m NOAA LiDAR dataset that is available for areas within 1 km of the coastline. We used post infra-red, infra-red stimulated luminescence (postIR-IRSL) techniques on fine-grain feldspars to measure the depositional age of the terrace sediments. Samples were collected by driving a metal pipe (capped at one end) into the deposit, and were extracted and sealed under a tarp to protect the samples from light contamination. Polymineral multi-grain aliquot equivalent dose measurements were determined at the California State University, Long Beach, Luminescence Lab on a Risø luminescence reader using a postIR-IRSL protocol adopted from Buylaert et al. (2009, doi:10.1016/j.radmeas.2009.02.007.) and Rhodes (2015, doi:10.1016/j.quaint.2014.12.012). Equivalent dose values were calculated using a Central Age Model at a 1-sigma uncertainty level (Galbraith et al., 1999, doi:10.1111/j.1475-4754.1999.tb00987.x). Dose rates were determined by the USGS Luminescence Dating lab in Denver Colorado using gamma spectroscopy. In addition to luminescence dating, two detrital charcoal samples were analyzed for radiocarbon dating at the Keck Carbon Cycle Accelerator Mass Spectrometry Facility, University of California Irvine. We collected the samples from the lowest (Ft1) and third-lowest (Ft3) fluvial terrace levels.