HR: 08:45h
AN: PP41F-04 INVITED    [Abstracts]
TI: Sedimentary iron records from the Cape Basin
AU: * Latimer, J C
EM: jlatimer@indstate.edu
AF: Indiana State University, Department of Environmental and Ecological Sciences, Terre Haute, IN 47809, United States
AU: Filippelli, G M
EM: gfilippe@iupui.edu
AF: IUPUI, Department of Geology, Indianapolis, IN 46202, United States
AB: The Southern Ocean potentially has a significant role in the modulation of CO2 and the global C cycle on glacial/interglacial time scales resulting from variations in primary productivity and nutrient fluxes. For example, the ‘‘Iron Hypothesis'' suggests dust Fe deposited in the Southern Ocean during glacial intervals fueled primary productivity and led to CO2 drawdown. Ice-core records provide clear evidence that the glacial atmosphere was dustier than during interglacial times. There is also unequivocal proof from Fe fertilization experiments that primary productivity in the modern-day Southern Ocean is limited by Fe. Complicating the situation in the Southern Ocean are the substantial hemipelagic sources and the effects of sediment focusing, which dilutes and obscures the eolian signal. As a result, the relationships between Fe fluxes, terrigenous provenance, and any subsequent biological response during glacial intervals remains poorly understood. Here we present records of Fe concentrations (total and reducible) and Fe fluxes to highlight the importance of hemipelagic Fe sources at ODP Leg 177, Site 1089 in the Cape Basin as well as indicators of terrigenous provenance. We find that on average only 7% of the Fe flux to Site 1089 can be accounted for by particle settling, indicating that sediment focusing is responsible for an order of magnitude more Fe than particulate scavenging and settling processes, distribution by surface currents, or eolian deposition. We also find that on average 7% of the Fe content is easily reducible, and we speculate that a significant source of dissolved Fe to bottom waters may come from re- suspended and re-worked bottom sediments.
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4926 Glacial
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting