EPISODIC COASTAL PROGRADATION IN SOUTHERN CALIFORNIA: EVIDENCES FROM GROUND-PENETRATING RADAR, RADIOCARBON AND LUMINESCENCE DATING DURING THE LAST MILLENNIUM

Coastal communities are threatened by rising sea levels. The impact can substantially increase during droughts, as it reduces sediment supply to coastal systems. Studies have suggested that the intensity of droughts may increase in the future, in a warming climate. Determining the coastal response is pivotal for hazard mitigation in the future. Ground-penetrating radar (GPR), in combination with radiocarbon, luminescence dating (OSL) and historical topographic maps, provide insight into the coastal response of the Oxnard Plain (near Santa Barbara), southern California, to past droughts and storms through the imaging of sedimentary stratigraphy.

Twelve vibracores were retrieved for ground truthing our GPR profiles. Charcoal, plant fragments, and shell fragments were retrieved and dated by radiocarbon. Shells will be impacted by a marine radiocarbon reservoir effect (about 300 years), along with being potentially reworked in the littoral system before deposition. Thus, these should be considered as a minimum age of deposition.

Here enters luminescence dating, on quartz mineral, providing support for the chronology. The presentation will primarily center on OSL dating.