HR: 15:25h
AN: PP43E-08    [Abstracts]
TI: Modern Calcium Carbonate Preservation in Equatorial Pacific Sediments in the Context of Late Pleistocene Glacial Cycles
AU: * Anderson, R F
EM: boba@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, P.O. Box 1000, Palisades, NY 10964, United States
AU: Lao, Y
EM: Yong.Lao@mwra.state.ma.us
AF: Massachusetts Water Resources Authority, 190 Tafts Avenue, Winthrop, MA 02152, United States
AU: Fleisher, M Q
EM: martyq@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, P.O. Box 1000, Palisades, NY 10964, United States
AU: Winckler, G
EM: winckler@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, P.O. Box 1000, Palisades, NY 10964, United States
AB: The CaCO₃ content of marine sediments in many regions of the ocean has varied systematically with climate throughout the late-Pleistocene glacial cycles. Both biological productivity and carbonate preservation have been proposed to be the master variable regulating this variability. We have evaluated the preserved flux of CaCO₃ in cores from the central equatorial Pacific Ocean (140° W) using the ²³⁰Th - normalization technique. Neither barite fluxes nor ¹⁰Be /²³⁰Th ratios, both geochemical proxies for export production, correlate with CaCO₃ fluxes, indicating that productivity is not the principal factor controlling CaCO₃ accumulation in these sediments. Preserved fluxes of CaCO₃ in central equatorial Pacific sediments correlate in time with the benchmark CaCO₃ record from the Cape Basin (South Atlantic Ocean; Hodell et al., EPSL 192 (2001) 109-124), supporting the view that changes in ocean chemistry (carbonate ion concentration) have controlled the pattern of CaCO₃ preservation and accumulation at these sites. Modern CaCO₃ preservation in equatorial Pacific sediments has dropped to levels nearly as low as those experienced at any time in the late Pleistocene. Similar changes occurred at the end of each of the late- Pleistocene interglacial periods, from which we infer that ocean carbonate chemistry has already undergone changes that are expected to precede the transition into the next ice age. However, during the late Pleistocene, the time interval between the decrease in CaCO₃ preservation and the end of the interglacial has varied substantially from one interglacial to another (from 2,000 to 15,000 years), so the late-Holocene decrease in CaCO₃ preservation cannot be used to predict the end of the Holocene interglacial period.
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 4806 Carbon cycling (0428)
DE: 4835 Marine inorganic chemistry (1050)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting