HR: 1340h
AN: PP13A-0598    [Abstracts]
TI: High-Resolution Records of Deglaciation on the California Margin: Rapid Warming as Recorded in Surface and Intermediate Waters
AU: * Hill, T M
EM: tmhill@ucdavis.edu
AF: Marine Science Institute, University of California, Santa Barbara, CA 93106 United States
AU: Kennett, J P
AF: Marine Science Institute, University of California, Santa Barbara, CA 93106 United States
AU: Behl, R
AF: Department of Geological Sciences, California State University, Long Beach 1250 Bellflower Blvd, Long Beach, CA 90840 United States
AU: Pak, D
AF: Marine Science Institute, University of California, Santa Barbara, CA 93106 United States
AU: Ohkushi, K
AF: Faculty of Education, Ibaraki University, Mito, 310-8512 Japan
AU: Robert, C
AF: CEREGE-CNRS, Europole Mediterraneen de l'Arbois, Aix-en-Provence, cedex 4 France
AU: Beaufort, L
AF: CEREGE-CNRS, Europole Mediterraneen de l'Arbois, Aix-en-Provence, cedex 4 France
AU: Zeleski, C M
AF: Department of Geological Sciences, California State University, Long Beach 1250 Bellflower Blvd, Long Beach, CA 90840 United States
AB: We present results from cores in Santa Barbara Basin that reside within (MD02-2503; 569 m) and above (MD02-2504; 441 m) the modern oxygen minimum zone (OMZ). These cores provide a high-resolution marine sediment deglacial record of surface and intermediate water processes. Oxygen isotopic values of benthic and planktonic foraminifera indicate a two-step deglaciation (including Terminations IA and B). During the deglacial period, oxygen isotopic values decrease by 3.2 per mil in planktonic species, indicating an 8-$9\deg$C warming assuming a 1.0 per mil ice volume effect. Benthic species record a 1.95 per mil d18O decrease across the deglacial, interpreted as a 3-$4\deg$C warming at intermediate depths. d18O values of both planktonic and benthic species indicate that surface and intermediate waters warmed synchronously, ~2ka prior to Termination IA, following an episode of cooling from 18-17 ka. This record adds to increasing reports of "Pre Bolling warming" around the globe and indicates the influence of Antarctic warming on surface and intermediate waters on the California margin. In addition to recording the timing of deglacial warming at high resolution, comparison of the two intermediate depth cores provides insights into OMZ processes during the glacial termination. Preservation of laminations and dysoxic benthic foraminiferal assemblages indicate that the OMZ extended to above the sill depth during Bolling-Allerod chronozone (B/A). Bolivina tumida, a benthic species associated with anoxia and methane-rich environments, dominates the assemblage at both the shallow and deep sites during the B/A. Planktonic foraminifera record decreased d13C values during the B/A, indicating a perturbation in the surface water DIC reservoir during this time.The B/A exhibited pronounced expansion of the OMZ around the North Pacific, typically attributed to changes in productivity and ventilation. Records from Santa Barbara Basin indicate the combined influence of water column methane oxidation, ventilation and/or productivity in OMZ expansion during the Bolling-Allerod.
DE: 3344 Paleoclimatology
DE: 3030 Micropaleontology
DE: 1040 Isotopic composition/chemistry
DE: 1050 Marine geochemistry (4835, 4850)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting