HR: 11:35h
AN: PP42A-05    [Abstracts]
TI: Elemental Imaging and Proxy development in Deep Sea Corals
AU: * Fallon, S J
EM: stewart.fallon@anu.edu.au
AF: The Australian National University, Research School of Earth Sciences, Canberra, ACT 0200, Australia
AU: Roark, E B
EM: broark@stanford.edu
AF: Stanford University, Dept. of Geological and Environmental Sciences, Palo Alto, Ca 94550, United States
AU: Guilderson, T P
EM: tguilderson@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, Ca 94550, United States
AU: Guilderson, T P
EM: tguilderson@llnl.gov
AF: University of California, Santa Cruz, Dept. of Marine Science, Santa Cruz, Ca 95004, United States
AU: Dunbar, R B
EM: dunbar@stanford.edu
AF: Stanford University, Dept. of Geological and Environmental Sciences, Palo Alto, Ca 94550, United States
AU: Weber, P
EM: weber21@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, Ca 94550, United States
AB: There is an increasing interest in developing proxy records of oceanographic conditions from intermediate and deep-water environments. Elemental and isotopic ratios incorporated into the calcite skeleton of deep-sea corals have been proposed as a method for obtaining this information. Before elemental proxies can be used, rigorous testing of elemental spatial variability and calibration is needed. Using the high-spatial resolution NanoSIMS 50 we examined the spatial variability of Mg/Ca, Sr/Ca and Ba/Ca ratios (potential temperature proxies) in 10 micron square images using a ~200 nm size primary beam (O^-) in thin-sections of the deep-sea corals Corallium secundum and the Isididae family corals. We found that the distribution of magnesium is not homogenous. There are many <1 micron features with Mg/Ca concentrations that ~40% higher than the surrounding area.. At this point we speculate that these features may be organic molecules rich in Mg, centers of calcification, or perhaps amorphous calcium carbonate. The Sr/Ca and Ba/Ca patterns are more homogenous; they do not show features related to the high Mg/Ca spots. The heterogeneity seen in the Mg/Ca ratio in these deep sea corals suggest that even if there is a temperature dependence, the occurrence of these high concentration Mg/Ca locations may hinder the accurate reconstruction of water temperature. The more homogenous Sr/Ca is compared to available temperature data from the region and shows good correspondence as s potential water temperature proxy.
DE: 1065 Major and trace element geochemistry
DE: 4215 Climate and interannual variability (1616, 1635, 3305, 3309, 4513)
DE: 4825 Geochemistry
DE: 4916 Corals (4220)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting