HR: 0800h
AN: PP41D-0778    [Abstracts]
TI: Paleoceanography Of The Middle Eocene Arctic Ocean Based On Geochemical Measurements Of Biogenic Matter
AU: Ogawa, Y
EM: oga@geo.kyushu-u.ac.jp
AF: Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University, Hakozaki6-10-1, Fukuoka, Fukuoka, 812-8581, Japan
AU: * Takahashi, K
EM: kozo@geo.kyushu-u.ac.jp
AF: Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University, Hakozaki6-10-1, Fukuoka, Fukuoka, 812-8581, Japan
AU: Yamanaka, T
EM: toshiroy@cc.okayama-u.ac.jp
AF: Graduate School of Natural Science and Technology, Okayama University, 1-1, Naka 3- chome, Tsushima, Okayama, Okayama, 700-8530, Japan
AB: The IODP Expedition 302, Arctic Coring Expedition (ACEX), recovered 428 m long sediment cores on the Lomonosov Ridge in the central Arctic Ocean. Chemical analyses for biogenic opal, total organic carbon (TOC), total sulfur (TS), and stable sulfur isotopic composition were conducted on the middle Eocene section of the ACEX cores. The previous study for microfossil assemblages on this section indicated the presence of low- salinity water mass in the Arctic Ocean. However, % TS contents were high in all intervals, indicating that abundant sea water was present in the deep layer of the paleo Arctic Ocean in contrast with low salinity surface water. The light sulfur isotope composition indicates the microbial sulfate reduction in an open system. This supports the continuous supply of sea water from the outside of the Arctic Ocean. The euxinic condition of the bottom water is suggested by the TOC-TS diagram. The anoxic environment was brought about by salinity stratification like the modern Black Sea. The high values of the accumulation of biogenic opal and TOC indicate high productivity which continued for nine myr. The high productivity was related to the estuarine type circulation in the semi-closed Arctic Ocean.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1055 Organic and biogenic geochemistry
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 9315 Arctic region (0718, 4207)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting