HR: 17:30h
AN: PP52C-07    [PDF]
TI: Normalization for Sediment Redistribution Yields Entirely Different Biogenic Fluxes for the LGM to Present in the Eastern Equatorial Pacific.
AU: * Loubere, P
EM: paul@geol.niu.edu
AF: Paul Loubere, Geology and Env. Geosciences Northern Illinois University, DeKalb, IL 60115 United States
AU: Mekik, F
EM: mekikf@gvsu.edu
AF: Figen Mekik, Dept. of Geology Grand Valley State University, Grand Rapids, MI 49401 United States
AU: Francois, R
EM: rfrancois@whoi.edu
AF: Roger Francois, Dept. of Marine Chemistry and Geochemistry Woods Hole Oceanographic Inst., Woods Hole, MA 02543 United States
AU: Pichat, S
EM: spichat@mpch-mainz.mpg.de
AF: Sylvain Pichat, Max Plank Inst. fuer Chemie, Abt. Geochemie, Mainz, D-55128 Germany
AB: The Eastern Equatorial Pacific (EEP) plays a large role in global ocean biological productivity and the exchange of carbon dioxide between the oceans and atmosphere. Because of this, much effort has been directed to reconstructing productivity and biogenic fluxes on the glacial/interglacial timescale in this region. These reconstructions are based on both sediment accumulation rate and ratio (relative abundances of microfossil taxa, element conc. ratios) methods. Traditionally, the accumulation rate results have been used and interpreted to indicate increased biogenic fluxes during glacials. However, the ratio methods have indicated the reverse. We proposed that this conflict of methodologies was the result of processes at the seabed biasing the accumulation rate data. We have tested this hypothesis by 230-thorium normalization of sediment accumulation rates in 4 cores in the EEP. This normalization shows that sediment ponding (focusing) has resulted in excess accumulation (compared to water column flux) by a factor between 2 to 8 for the LGM in the cores we examined. This increased focusing during the glacial has been observed by others previously. We use a novel transfer function to reconstruct calcite fluxes using the normalized data and show that the resulting calcite flux profiles match well with independent ratio based organic carbon flux estimators; and that both fluxes were lower at the LGM compared to the Present. Thus, normalization for sediment transport resolves the discrepancy between methodologies, and shows that biogenic fluxes were opposite to traditional interpretations for the LGM to the Present.
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1615 Biogeochemical processes (4805)
DE: 3022 Marine sediments--processes and transport
DE: 4203 Analytical modeling
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting