HR: 0800h
AN: PP11B-0520    [Abstracts]
TI: High-resolution past environmental reconstruction in East Asia using annually laminated lake sediments of Lake Megata in northeastern Japan
AU: * Yamada, K
EM: kyamada@soc.shimane-u.ac.jp
AF: Shimane Univ., Nishikawatsu-cho 1060, Matsue, 6908504, Japan
AU: Gotanda, K
EM: gotanda@cuc.ac.jp
AF: Chiba Univ. of Commerce, 1-3-1 Konodai, Ichikawa, 2728512, Japan
AU: Yonenobu, H
EM: yn@naruto-u.ac.jp
AF: Naruto Univ. of Education, Naruto 748, Naruto, 7728502, Japan
AU: Shinozuka, Y
EM: shino@ees.hokudai.ac.jp
AF: Hokkaido Univ., Kita8 Nishi5, Sapporo, 0600808, Japan
AU: Kitagawa, J
EM: junkokit@nichibun.ac.jp
AF: International Research Center for Japanese Studies, Nishikyo-ku,Goryooeyama 3-2, Kyoto, 6101192, Japan
AU: Makohonienko, M
EM: makoho@amu.edu.pl
AF: Adam Mickiewicz Univ., H. Wieniawskiego 1, Poznan, 61712, Poland
AU: Schwab, M
EM: mschwab@gfz-potsdam.de
AF: GeoForschungsZentrum, Telegrafenberg, Potsdam, D14473, Germany
AU: Haraguchi, T
EM: haraguti@sci.osaka-cu.ac.jp
AF: Osaka City Univ., Sugimoto-cho 3-3-138, Osaka, 5588585, Japan
AU: Yasuda, Y
EM: yasuda@nichibun.ac.jp
AF: International Research Center for Japanese Studies, Nishikyo-ku,Goryooeyama 3-2, Kyoto, 6101192, Japan
AB: 37 m-long non-glacial varved sequences were taken from Ichi-no-Megata maar in Oga Peninsula, Akita, northern part of Japan. Ichi-no-Megata maar occupies 0.25 km2 with a maximum water depth of ca. 45.1 m. The shape of lake is a kettle-type basin and the deepest bottom basin is very flat. We took core samples (named IMG06 core) at the center of the lake in November to December in 2006. In order to take completely continuous maar sediment, we drilled three holes and take every sample from each hole which apart only few meters. In this drilling campaign, we can 37 m-long continuous maar sediment except thick volcanic deposits from 26.5 to 31.7m in core. The sedimentological feature of IMG06 core is dominated by thin lamination clay/silt from most top part up to 37 m with turbidites characterized upward fining structure. The SEM image observation of lamination reveals that sponge-like lamina consists of diatom assemblage against dark colored lamina consists of mixture of detritus minerals, clay minerals, and diatom. It means sponge-like lamina deposits during spring season, and later one deposits during another three seasons, and then these thin lamination of IMG06 core could be identified as annual lamination (varves). This interpretation is supported by the correlation of historic event as earthquake and tunnel construction. In this IMG06 core, six volcanic ashes are found and we have also analyzed radiocarbon dating from 38 horizons of the core to use leaf and seeds inter-bedded varves. As the results, the IMG06 core covers from 25,000 to 4,000 14C yr BP with stable sedimentation rates (0.71mm/year).
DE: 1105 Quaternary geochronology
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4942 Limnology (0458, 1845, 4239)
DE: 9320 Asia
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting