HR: 0800h
AN: PP51F-1371    [Abstracts]
TI: Sedimentary Characteristics through Glacial/Interglacial Transitions at ODP Site 1233
AU: * Joseph, L H
EM: Ljoseph@ursinus.edu
AF: Environmental Studies Program, Ursinus College, PO Box 1000, Collegeville, PA 19426 United States
AB: ODP Site 1233, located shoreward of the Chile Trench on the Chilean continental slope ($\sim$38 km offshore; $41\deg$0.005'S, $74\deg$26.992'W, 838 mbsl), recovered a 136 mcd-thick continuous and extremely high-resolution sedimentary sequence that extends through 70 ka, providing the potential to significantly enhance our knowledge of Southern Hemisphere climates. The sediment collected originates in an area where the erosion and transport of sediment to the continental margin is enhanced by alpine glaciation and heavy rainfall. This study investigates glacial/interglacial sediment variations in through the use of magnetic fabric (anisotropy of magnetic susceptibility, AMS), terrigenous grain size, and flux calculations. Site 1233 consists primarily of homogenous nannofossil clay, nannofossil silty clay, and nannofossil-bearing silty clay. Ninety-one samples were taken at approximately 1.5-meter intervals from a composite splice. On average, one sample was obtained for every $\sim$800 years. Bulk magnetic susceptibility values range from 3.4 x 10$^{-4}$ to 4.6 x 10$^{-3}$ SI with an average of 3.0 x 10$^{-3}$ SI. Values of AMS parameter P' (the strength of the magnetic fabric) range from 1.005 through 1.058, with an average of 1.025 while T values (shape factor) fall almost exclusively within the oblate realm, especially when samples from noted intervals of diagenesis are disregarded. The depositional environment, as indicated by P' and T, plots within the field of low to mid-velocity currents, indicating some current influence at this site. The strength of the magnetic fabric (P') varies through time, with maxima present at $\sim$38 and 13 ka, and may represent fluctuations or changes in the surrounding AAIW. Analyses of terrigenous grain size and flux are on-going and will facilitate further interpretation of the magnetic fabric results.
DE: 4267 Paleoceanography
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3022 Marine sediments--processes and transport
DE: 1518 Magnetic fabrics and anisotropy
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting