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Late Holocene environmental history of Campus Lagoon, Santa Barbara, California

Ryan Owings, Dillon J. Osleger, Angel Roman, & Alexander R. Simms

Published November 7, 2023, SCEC Contribution #13405

Large earthquakes, drought, and heightened storm activity associated with El NiƱo Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) have the potential to impact daily life and transform the coastal landscape across Southern California from San Diego to the northern Channel Islands. The stratigraphy and seismic architecture of Campus Lagoon, a flooded river valley incised into a marine isotope stage (MIS) 3 marine terrace near Santa Barbara, California, was examined to better understand the nature and frequency of these events. The valley fill provides a record of late Holocene environmental history for the Santa Barbara region including climate change and potential coseismic uplift within the western Santa Barbara Fold Belt (SBFB). Ten sediment cores and high-resolution seismic data collected from UCSB Campus Lagoon between 2013 and 2023 were examined in this study. The oldest sediments sampled were coarse-grained sands dating to 5-4 ka, a period of heightened ENSO. Clayey silts with and without evaporites overlie the sands and were deposited during periods of Holocene aridity between 3.2-0.6 ka. This period of aridity is found in regional records across the area including sea-surface temperature records from the Santa Barbara Basin and by changing behavioral patterns of peoples and isotopic signatures of mollusks on the northern Channel Islands. Upper beds of coarse-grained sands suggest a return to stormy conditions and heightened ENSO around 0.6 ka. In addition, seismic surveys collected from Campus Lagoon show two downward shifts in onlap, occurring within the last 4 ka. In the absence of eustatic changes in RSL over this period, they may have been triggered by large magnitude earthquakes that uplifted the lagoon out of an intertidal zone and into an upper intertidal / lower supratidal mudflat.

Owings, R., Osleger, D. J., Roman, A., & Simms, A. R. (2023, 11). Late Holocene environmental history of Campus Lagoon, Santa Barbara, California. Poster Presentation at 10th Annual California Islands Symposium.