HR: 09:15h
AN: PP11C-06    [Abstracts]
TI: Pore Fluid Records of the Salinity and Temperature of the LGM Deep Pacific
AU: * Adkins, J F
EM: jess@gps.caltech.edu
AF: Dept. of Geological and Planetary Sciences, Caltech 1200 E California Blvd, Pasadena, CA 91125, United States
AU: Schrag, D P
EM: schrag@eps.harvard.edu
AF: Dept of Earth and Planetary Sciences, Harvard University 20 Oxford St, Cambridge, MA 02138, United States
AB: The [Cl] and δ¹⁸O-water profiles of deep-sea pore fluids can constrain the Last Glacial Maximum (LGM) bottom water content of these two tracers. Over a range of sites, and when combined with local measurements of benthic foraminifera, the pore water data yield the T/S plot and the δ¹⁸O-S plot for the LGM deep ocean. We report two new pore fluid profiles from the eastern equatorial Pacific that compliment previous work on this topic. IODP site 1239 at 1414 meters water depth yields LGM values for Cl and δ¹⁸O that are 4.6±0.6% and 1.2±0.1‰ larger than the modern bottom water. Site 1240 at 3000 meters water depth, on the other hand, has a complex profile for both tracers. This site is in close proximity to the ridge axis and clearly contains enhanced advection of pore fluids, over and above the "normal" model of compaction driven fluid flow. There is evidence for forced flow along the sediment-basalt interface and for enhanced vertical flow due to local temperature gradients. Including both of these sources of advection in our standard 1-D advection-diffusion model results in good fits with the measured [Cl] and δ¹⁸O. While the new sources of advection induce large uncertainties in the reconstructed LGM bottom water values, the Holocene portion of the pore fluid profile may be better resolved than at other sites. Both [Cl] and δ¹⁸O show a large freshening at 10-20 meters deep in the sediment. This feature may be the result of a global redistribution of ice volume between land and sea during the Holocene that has been recognized, though much more subtly, in our previous profiles.
DE: 4924 Geochemical tracers
DE: 4926 Glacial
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting