Project Abstract
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The marine terrace underlying the campus of the University of California Santa Barbara dates to ~40 ka. Its current elevation suggests uplift of approximately 2 mm/yr. However, the role of earthquakes in the uplift is unknown. A recent seismic survey within the lagoon contains no fewer than 2 strong reflections exhibiting onlap onto older reflections that may represent periods of co-seismic uplift of the lagoon and its encasing marine terrace through the Holocene. We obtained 5 new sediment cores, new geochemical data, and 20 new radiocarbon ages from the lagoon with the intent of sampling and characterizing that surface in order to determine if it was exposed during past earthquakes. Although the surface is marked by carbonates, they are not of pedogenic origin as would be expected if they were created by exposure due to co-seismic uplift. Thus, although uplift during an earthquake cannot be ruled out as a contributing factor to the formation of the onlap, carbonates, and strong reflections, desiccation of the lagoon due to its isolation from the open ocean by the formation of a larger barrier or drier climates from 1-3 ka during the Holocene are just as likely a cause of the reflection pattern. Thus, although the lagoon has uplifted through the Holocene we cannot unequivocally call upon earthquakes as the cause of that uplift. |
