HR: 0800h
AN: PP11A-0232 [Abstracts]
TI: Equatorial Pacific Reactive Phosphorus Accumulation Rates across the Eocene/Oligocene Transition
AU: * Faul, K L
EM: kfaul@mills.edu
AF: Environmental Sciences Program/Chemistry and Physics Department, Mills College, 5000
MacArthur Boulevard, Oakland, CA 94613, United States
AU: Stewart, K L
EM: kstewart@mills.edu
AF: Environmental Sciences Program/Chemistry and Physics Department, Mills College, 5000
MacArthur Boulevard, Oakland, CA 94613, United States
AB:
Paired benthic foraminiferal stable isotope and trace metal records from ODP Site 1218 in the equatorial Pacific
have shown that the Eocence/Oligocene (E/O) transition (~34 Ma) represents a major increase in Antarctic ice
accumulation and a rapid deepening of the global calcite compensation depth (CCD) occurring in two steps [e.g.,
Lear et al., 2000; Lear et al., 2004; Coxall et al., 2005; Palike et al., 2006]. Simultaneous increases in biogenic
mass accumulation rates (MARs) around Australia and in the Atlantic Ocean have been interpreted as
representing increased productivity and/or organic carbon (C) burial possibly linked to cooling and ice sheet
growth [Diester-Hass and Zahn, 2001; Anderson and Delaney, 2005]. Because the global CCD deepens across
the transition, there is a need to distinguish organic C burial changes from CCD changes. We are determining
reactive phosphorus (P, micromol P cm-2 kyr-1) MARs as an indicator of organic C burial for Site 1218
to help constrain the relative role of productivity during the E/O climatic transition. Reactive phosphorus (the sum
of oxide associated, authigenic, and organic P; sequentially extracted from bulk sediment), delivered to the
sediment water interface with organic C, is well preserved in oxygenated sediments. Preliminary results show an
order of magnitude decrease in reactive P concentrations (from ~100 to ~10 micromol P g-1) across the E/O
boundary. This may indicate that absolute organic C burial as well as the ratio of organic C burial to calcite burial
may have decreased across the E/O transition in the equatorial Pacific upwelling zone.
DE: 0428 Carbon cycling (4806)
DE: 4845 Nutrients and nutrient cycling (0470, 1050)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4924 Geochemical tracers
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting