HR: 1340h
AN: PP43B-1243    [Abstracts]
TI: Deglacial terrigenous organic matter input to sediments from Orca Basin, Gulf of Mexico - a combined optical and biomarker approach
AU: * Meckler, A
EM: ameckler@gps.caltech.edu
AF: ETH Zurich, Geological Institute, Universitaetsstrasse 6, Zurich, 8092, Switzerland
AU: Schubert, C J
EM: carsten.schubert@eawag.ch
AF: EAWAG, Seestrasse 79, Kastanienbaum, 6047, Switzerland
AU: Hochuli, P A
EM: peter.hochuli@erdw.ethz.ch
AF: University of Zurich, Paleontological Institute, Karl Schmid-Strasse 4, Zurich, 8006, Switzerland
AU: Plessen, B
EM: birgit@gfz-potsdam.de
AF: Geoforschungszentrum Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Birgel, D
EM: dbirgel@uni-bremen.de
AF: University of Bremen, MARUM, Bremen, 28359, Germany
AU: Hinrichs, K
EM: khinrichs@uni-bremen.de
AF: University of Bremen, MARUM, Bremen, 28359, Germany
AU: Haug, G H
EM: gerald.haug@erdw.ethz.ch
AF: Geoforschungszentrum Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AB: In addition to paleo-salinity reconstructions, the abundance of terrigenous organic matter (OM) in marine sediments can be a valuable indicator of past changes of river outflow and/or meltwater flux. In the Gulf of Mexico, deglacial decreases in salinity indicate large input of meltwater via the Mississippi (Leventer et al. 1983, Flower et al. 2004), which probably had a strong effect on the Atlantic Meridional Overturning circulation and hence climate. Using a sediment core from the same location, we complemented these previous analyses by assessing changes in the contribution of terrigenous OM over the course of the last deglaciation. To this end, we combined optical kerogen analyses with bulk sedimentary, biomarker, and compound-specific carbon isotope analyses. During glacial times, terrigenous OM input was higher than today, as expected due to the closer proximity of the Mississippi River mouth. Furthermore, the optical analyses revealed that much of the glacial OM is reworked, i.e. of Cretaceous age or older. In contrast, the Holocene sediment contains mainly marine OM, which is exceptionally well preserved. During the last deglaciation, terrigenous input was also generally high due to the large meltwater fluxes. However, additional influences can be inferred, such as the change in distance to the river mouth, local productivity changes, and hydrodynamic particle sorting. Towards the end of the meltwater input period, the link between salinity and the abundance of terrigenous OM is weaker. Most importantly, the early part of the Younger Dryas period, around 12.5 ka, was characterized by a secondary peak in terrigenous input, although it is generally believed that meltwater flow was rerouted away from the Mississippi at this time. These results add to the growing evidence of intra-Younger Dryas variations in meltwater routing and climate and suggest that the history of deglacial meltwater inflow to the Gulf of Mexico might not yet be fully understood.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1055 Organic and biogenic geochemistry
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4952 Palynology
DE: 9350 North America
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting