HR: 0800h
AN: PP41D-0781    [Abstracts]
TI: Paleoceanography of the Eocene Arctic Basin Reconstructed With Chemical Parameters and Siliceous Microfossils
AU: * Takahashi, K
EM: kozo@geo.kyushu-u.ac.jp
AF: Department of Earth & Planetary Sciences, Kyushu University Graduate School of Sciences Department of Earth & Planetary Sciences Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan
AU: Ogawa, Y
EM: oga@geo.kyushu-u.ac.jp
AF: Department of Earth & Planetary Sciences, Kyushu University Graduate School of Sciences Department of Earth & Planetary Sciences Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan
AU: Onodera, J
EM: jm-jo@kochi-u.ac.jp
AF: Center for Advanced Marine Core Research, Kochi University, B200 Monobe, Nankoku, Kochi, 783-8502, Japan
AU: Yamanaka, T
EM: toshiroy@cc.okayama-u.ac.jp
AF: Graduate School of Natural Science and Technology, Okayama Univeristy, 1-1 Naka 3- chome, Tsushima, Okayama, 700-8530, Japan
AB: With the currently predicted drastically different future environments of the Arctic Ocean without perennial sea-ice cover, it is important to learn how the ice-free Arctic basin behaved in the past. The environmental reconstruction of the middle Eocene Arctic basin explored by the IODP Arctic Coring Expedition (ACEX) provides excellent opportunity to advance our knowledge on the ice free Arctic basin. The early to middle Eocene represents the warmest interval of the Cenozoic Era. Of this ACEX retrieved approximately 120 m long more or less continuous Eocene section from the Lomonosov Ridge located in the central Arctic. The measured parameters includes total organic carbon, total sulfur, stable sulfur isotopic composition (δ³⁴S), nitrogen, biogenic opal, silicoflagellates, ebridians, chrysophytes, and diatoms. The interpreted environments of the middle Eocene arctic basin are represented by the presence of fresh water chrysophytes near the seasurface, brackish waters in the subsurface indicated by the presence of diatoms, silicoflagellares, and ebridians, followed by anoxic waters lying below the brackish waters but within the euphotic layers indicated by ebridians. The position of the boundary between the oxygenated and anoxic layers reconstructed by ebridians conforms with those obtained by organic compounds such as lycopane and isorenieratene derivatives (Dr. R. Stein, Pers. Comm., 2007). High biological productivity and poor basin water circulation was evident from abundant pyrites. Although the seasurface was covered by fresh waters, the middle Eocene Arctic basin contained ample amount of seawaters indicated by the continuous high abundance of sulfur mainly in the form of pyrites as well as sporadic occurrences of radiolarians. Based on the silicoflagellate paleotemperature reconstruction, 20-25°C have been obtained for the middle Eocene Arctic. This range is conformable with those of 19-23°C SST estimated by TEX86 (Sluijs, et al., Nature, 441, 2007) as well as surrounding continental temperatures of 18-25°C shown by MPT as an indicator of soil bacteria (Dr. H. Brinkhuis, Pers. Comm., 2007).
DE: 4802 Anoxic environments (0404, 1803, 4834, 4902)
DE: 4835 Marine inorganic chemistry (1050)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4944 Micropaleontology (0459, 3030)
DE: 4948 Paleocene/Eocene thermal maximum
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting