HR: 1340h
AN: PP53B-1396    [Abstracts]
TI: Evaluation of Geochemical Proxies Preserved in the Sapropel Record from the Eastern Mediterranean Within the Pliocene-Holocene Time Interval
AU: * Gallego-Torres, D
EM: davidgt@ugr.es
AF: Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Facultad de Ciencias. Campus Fuentenueva, Granada, 18002 Spain
AU: Martinez-Ruiz, F
EM: fmruiz@ugr.es
AF: Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Facultad de Ciencias. Campus Fuentenueva, Granada, 18002 Spain
AU: Paytan, A
EM: apaytan@pangea.stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University , Stanford, CA 94305 United States
AU: Kastner, M
EM: mkastner@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, La Jolla, CA 92093 United States
AB: Considerable research has been devoted during the last decade to productivity and oxygenation proxies of sapropel deposition in the Mediterranean. Pliocene-Holocene sapropel layers from Mediterranean basins are considered to be an important key to assess the role of productivity vs. anoxia in organic matter (OM) accumulation. Evaluation of proxy preservation within these sediments is therefore crucial to further investigate forcing mechanism for OM deposition. With this aim, diverse layers from Pliocene, Pleistocene and Holocene sediments recovered at ODP Site 964 in the eastern Mediterranean have been analyzed. Ba excess is recognized as a reliable proxy for enhanced productivity because it derives from barite crystals originated in the water column. Additionally, their S isotope composition revealed that barite is an authigenic phase (Paytan et al., 2004). This proxy also revealed of exceptional importance in Mediterranean basins because some sapropels have been partially or totally oxidized. Assessment of productivity variations cannot be based therefore on the OM record which is strongly subjected to diagenetic preservation. Certain redox-sensitive elements as Mn were also subjected to remobilization during oxidation precipitating upon encountering the oxidation front. However some well preserved trace-element ratios, used as oxygenation proxies, are still recognized. These consistently point to a relatively oxic environment during the deposition of Quaternary sapropels while Pliocene sapropels tend to be characterized by lower oxygen conditions. Ba excess also indicates that barite accumulation rates within sapropels decreased through time, being considerable higher during the Pliocene. Thus, elevated primary export production could have enhanced oxygen consumption leading to lower oxygen levels at this time. Paytan, A., F. Martinez-Ruiz, M. Eagle, A. Ivy, and S.D. Wankel (2004) Using sulfur isotopes in barite to elucidate the origin of high organic matter accumulation events in marine sediments. Sulfur Biogeochemistry, GSA Special Paper, 379, 151-160.
DE: 4875 Trace elements
DE: 4267 Paleoceanography
DE: 1030 Geochemical cycles (0330)
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1065 Trace elements (3670)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting