PP002-0004
A new paleoceanographic record from Tanner Basin in the outer California Borderlands: preliminary results from the southern California Current System
Monday, 7 December 2020
Poster
Jason A Addison, USGS Geology, Minerals, Energy, & Geophysics Science Center, Menlo Park, CA, United States, Summer Kate Praetorius, USGS, Geology, Minerals, Energy, and Geophysics Science Center, Menlo Park, CA, United States, Linda E Heusser, Lamont -Doherty Earth Observatory, Palisades, NY, United States, Amy J Wagner, California State University Sacramento, Sacramento, CA, United States and Valerie Schwartz, Juul Labs Inc., Mountain View, CA, United States
Abstract:
The California Current System (CCS) extends ~3,000 km along the margin of western North America. Recent work in the northern California sector of the CCS (~41°N) shows that CCS upwelling underwent at least four shifts in intensity during the last 7,500 years, with the onset of “modern” conditions occurring as recently as 2.9 calibrated kiloyears before present (cal ka BP), but additional research is needed to assess the full geographic complexity of the CCS. Data from new sediment cores recovered in 2017 by the R/V
Sally Ride from Tanner Basin (~33°N) document change in the southern California sector of the CCS. Computerized tomography (CT) imaging was used to stratigraphically align all recovered cores and develop a composite depth scale that shows complete sediment recovery to 11 meters. A preliminary geochronological model was constructed using
14C dating of planktic foraminifera and by bulk density correlations to previously dated cores from Tanner Basin, including ODP Site 1014, which suggest a continuous record for the last 96,000 years.
Non-destructive XRF geochemical analyses show the Holocene is marked by enrichments in biogenic and/or porewater components (Ca, Br, Cl) while the preceding glacial interval is enriched in terrigenous components (K, Ti, Fe). The highest measured Br concentration (proxy for organic C) is observed as a distinct peak at ~80 ka BP and is preceded by a peak in Ca/Ti (proxy for carbonate C) at ~83 ka BP, both of which occur during Marine Isotope Stage 5a. These results contrast with the Holocene, where high Ca/Ti values are stable, and low Br values increase during the early/middle Holocene to maximum values at ~3 cal ka BP, similar to the timing of maximum upwelling in the northern CCS. The Tanner Basin data suggest a consistent system-wide CCS response to late Holocene conditions, but the differences between the Holocene and MIS 5a also suggest there may be fundamental differences in how the CCS functions during past interglacials.
