HR: 09:30h
AN: OS31C-07    [Abstracts]
TI: Sources of Fe to the Equatorial Pacific Ocean from the Holocene to Miocene
AU: Ziegler, C L
EM: christa.l.ziegler@exxonmobil.com
AF: Earth Sciences, Boston University, Boston, MA 02215, United States
AU: * Murray, R W
EM: rickm@bu.edu
AF: Earth Sciences, Boston University, Boston, MA 02215, United States
AU: Plank, T
EM: tplank@bu.edu
AF: Earth Sciences, Boston University, Boston, MA 02215, United States
AU: Hemming, S R
EM: sidney@ldeo.columbia.edu
AF: Earth and Env Sciences, LDEO, Palisades, NY 10964, United States
AB: Biological productivity in the modern equatorial Pacific Ocean, a region with high nutrients and low chlorophyll, is currently limited by the micronutrient Fe. Whether this region was Fe limited in the past remains unclear. In order to test whether Fe was limiting in the past and to identify potential pathways of Fe delivery that could drive Fe fertilization (i.e., dust delivery from eolian inputs versus Fe supplied by the Equatorial Undercurrent), we chemically isolated the terrigenous material from marine sediment along a cross-equatorial meridional transect in the central equatorial Pacific at 140W and at Ocean Drilling Program Site 850 in the eastern equatorial Pacific. We quantified the contribution from each potential Fe-bearing terrigenous source using a complete suite of chemical- and isotopic discrimination strategies as well as multivariate statistical techniques. We find that the distribution of the terrigenous sources (i.e., Asian loess, South American ash, Papua New Guinea, and ocean island basalt) varies through time, latitude, and climate. Regardless of which method is used to determine accumulation rate, there also is no relationship between flux of any particular Fe source and climate. Moreover, there is no clear connection between a particular Fe source or pathway (eolian versus Undercurrent) to total productivity during the Last Glacial Maximum, Pleistocene glacial episodes, and the Miocene Biogenic Bloom. This would suggest an alternative process, such as an interoceanic reorganization of nutrient inventories, is responsible for past changes in carbon export in the open ocean, rather than simply Fe supply from dust and/or Equatorial Undercurrent processes.
DE: 4231 Equatorial oceanography
DE: 4273 Physical and biogeochemical interactions
DE: 4924 Geochemical tracers
DE: 4926 Glacial
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting