HR: 0800h
AN: PP11A-0202    [Abstracts]
TI: Temporal and Spatial Changes in Bottom-Water Oxygenation in the Japan Sea During the Late Quaternary : The Effects on the Benthic Foraminiferal Assemblages
AU: * Usami, K
EM: k-usami@es.sci.kumamoto-u.ac.jp
AF: Division of Natural Environmental Sciences, Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto, 860-8555, Japan
AU: Ohi, T
EM: ohi@es.sci.kumamoto-u.ac.jp
AF: Division of Natural Environmental Sciences, Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto, 860-8555, Japan
AU: Hasegawa, S
EM: shiro@sci.kumamoto-u.ac.jp
AF: Division of Natural Environmental Sciences, Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto, 860-8555, Japan
AB: Late Quaternary hemipelagic sediments in the Japan Sea are characterized by alternating beds of light and dark layers which are synchronous basin-wide and considered to be reflections of bottom-water oxygenation during the depositions (Oba et al., 1991; Tada et al., 1999). In this study, benthic foraminiferal assemblages are analyzed to understand temporal and spatial variations of sea-floor environments during times of dark layer formation for the last 160ka, based on the 3 cores IMAGES MD01-2407 and D-GC-6 recovered at the same position (water depth 932m) in the southeastern Japan Sea, and KR05-09, PC-1 (water depth 1792m) in the northeastern Japan Sea. The dark layers in these cores are classified into six types by dominant species of benthic foraminifera and benthic foraminiferal abundance mainly in the core MD01-2407 (Usami et al., 2007), as follows: Barren-type (almost absent of benthic foraminifera), Angulogerina-type (abundant Angulogerina ikebei), mixture-type (relatively high species diversity and equitability), Islandiella-type (abundant Islandiella norcrossi), Eilohedra-type (abundant Eilohedra nipponica), Brizalina-type (abundant Brizalina pacifica). In the core KR05-09, PC-1, to the contrary, benthic faunas are adopted only three types, barren-type, mixture-type and Brizalina-type. In particular, most of the dark layers from MIS3 to 5b are barren-type, suggesting more severe oxygen depletion in benthic ecosystem of the northeastern Japan Sea. Oba, T., Kato, M., Kitazato, H., Koizumi, I., Omura, A., Sasaki, T., Takayama, T., 1991. Paleoenvironmental changes in the Japan Sea during the last 85,000 years. Paleoceanography 6, 499-518. Tada, R., Irino, T., Koizumi, I., 1999. Land-ocean linkages over orbital and millennial timescales recorded in late Quaternary sediments of the Japan Sea. Paleoceanography 14 (2), 236-247. Usami, K., Ohi, T., Hasegawa, S., 2007. Foraminiferal response to late Quaternary climate variability in the Japan Sea : Concerning low oxygen environment and productivity. 9th International Conference on Paleoceanography [ Shanghai, China ], Abstracts (in press).
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0459 Macro- and micropaleontology (3030, 4944)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting