HR: 0800h
AN: PP41A-0588    [Abstracts]
TI: Late Cenozoic reduction in Antarctic Circumpolar Current flow from analyses of drift deposits along the Antarctic Peninsula, ODP Site 1095.
AU: * Hassold, N J
EM: nhassold@umich.edu
AF: Department of Geological Sciences, 2534 C.C.Little Building, 425 E. University Avenue, University of Michigan, Ann Arbor, MI 48109-1063 United States
AU: Rea, D K
EM: davidrea@umich.edu
AF: Department of Geological Sciences, 2534 C.C.Little Building, 425 E. University Avenue, University of Michigan, Ann Arbor, MI 48109-1063 United States
AU: Pares, J M
EM: jmpares@umich.edu
AF: Department of Geological Sciences, 2534 C.C.Little Building, 425 E. University Avenue, University of Michigan, Ann Arbor, MI 48109-1063 United States
AU: van der Pluijm, B A
EM: vdpluijm@umich.edu
AF: Department of Geological Sciences, 2534 C.C.Little Building, 425 E. University Avenue, University of Michigan, Ann Arbor, MI 48109-1063 United States
AB: All waters from the Earth's oceans flow into and are mixed in the Antarctic Circumpolar Current (ACC). Thus the ACC has a major effect on the transport of heat in the oceans and the Earth's climate. Sediment drifts, which form along the Antarctic Peninsula under the influence of the ACC, record the history of this flow. We examined samples from cores drilled during Ocean Drilling Program (ODP) Leg 178 along the Antarctic Peninsula to determine paleocurrent strength changes. Both paleomagnetic cubes and sediment samples were taken from cores from ODP Site 1095 ($66\deg$59'S, $78\deg$29'W, 3814m). Factor analysis using major element chemistry indicates a two-component system between terrigenous and biogenic opal. The terrigenous fraction of 236 sediment samples was isolated and the grain size measured to determine the terrigenous mass accumulation rate (MAR), the median grain size ($\phi$50), the $>$63 $\mu$m MAR and the biogenic opal MAR. Terrigenous mass accumulation rates reflect the overall MAR's at the site, decreasing in a series of steps at 9 my, 5.5 my, and 2.5 my. Median grain size changes occur at 5.5 my (sharp decrease followed by a slight increase) and 2.7 my (decrease). The magnetic fabric, as determined for 324 samples by anisotropy of magnetic susceptibility (AMS), decreases sharply at 5.7 my and again at 2.7 my. We interpret these step-like changes as indicating a decline in the current strength over the last 6 my, with specific decreases occurring around 5.5 my and 2.5 my.
DE: 4267 Paleoceanography
DE: 3022 Marine sediments--processes and transport
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting