HR: 0830h
AN: OS31B-0210    [PDF]
TI: Abrupt Climatic Transitions: Surface to Intermediate-Water Response From High-Resolution Sediment Records, Santa Barbara, California
AU: * Hill, T M
EM: tessa@umail.ucsb.edu
AF: University of California, Santa Barbara, Department of Geological Sciences, Santa Barbara, CA 93106 United States
AU: Pak, D
EM: pak@geol.ucsb.edu
AF: University of California, Santa Barbara, Department of Geological Sciences, Santa Barbara, CA 93106 United States
AU: Kennett, J P
EM: kennett@geol.ucsb.edu
AF: University of California, Santa Barbara, Department of Geological Sciences, Santa Barbara, CA 93106 United States
AU: Lea, D W
EM: lea@geol.ucsb.edu
AF: University of California, Santa Barbara, Department of Geological Sciences, Santa Barbara, CA 93106 United States
AU: White, J
EM: jwhite1@wellesley.edu
AF: Wellesley College, Geology Department 106 Central Street, Wellesley, MA 02481 United States
AB: Exceptionally high sedimentation rates in Santa Barbara Basin provide an opportunity to closely examine the character of the abrupt warming at the end of the last glacial episode. Two new piston cores collected as part of the IMAGES/MONA program span the intermediate water depths of Santa Barbara Basin, allowing us to determine the timing and amplitude of deglacial warming through the entire water column. Site MD02-2503 was drilled at 569 m water depth, recovering 47 m, providing intermittently laminated sediments to Interstadial event 6 (~32ka). Site MD02-2504 was drilled at 440m water depth, just below the modern basin sill depth and recovered 37 meters of sediment, to ~22ka. Sedimentation rates for both cores average 140 cm/ka, comparable to ODP Site 893. Preliminary results indicate a two-step warming (Termination IA and IB) recorded by oxygen isotopic values and Mg/Ca ratios of planktonic foraminifera. Planktonic foraminiferal Mg/Ca records a 9 degree (C) temperature change from the last glacial to Holocene, consistent with records from Pt. Conception (ODP 1017). A 3 per mil oxygen isotopic shift is recorded by planktonic foraminifera over this same time period. Thus, warming recorded by Mg/Ca ratios and stable isotopic values appear similar in terms of both magnitude and phasing. Benthic foraminiferal assemblages at both sites indicate changes in intermediate water characteristics on stadial/interstadial and glacial/interglacial timescales. While laminations are absent for most of MD02-2504, they are present in both cores during the Bolling-Allerod. This implies an expansion of the oxygen minimum zone (OMZ) during the Bolling-Allerod that is vertically more significant than the Holocene. Further work on these cores, combined with data from previously described ODP Sites on the California margin (893 and 1017), will allow us to determine 1) if the deglacial termination on the California margin appears synchronous with global climate change, 2) the relative timing of surface to intermediate water warming across the Termination, and 3) the strength and depth of the OMZ during abrupt climate change.
DE: 4267 Paleoceanography
DE: 4870 Stable isotopes
DE: 4875 Trace elements
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting