1. Kochi Institute for Core Sample Research; Japan Agency for Marine-Earth Science and Technology, 200 Monobe Otsu; Nankoku-city Kochi 783-8502 Japan
2. Office of Liaison and Cooperative Research; Tokyo University of Marine Science and Technology, 4-5-7, Konan, Minato-ku; Tokyo 108-8477 Japan
3. Department of Natural History Sciences, Graduate School of Science; Hokkaido University, N10-W8, Kita-ku; Sapporo-shi Hokkaido 060-0808 Japan
4. Atmosphere and Ocean Research Institute; The University of Tokyo, 5-1-5 Kashiwanoha; Kashiwa-shi Chiba 277-8564 Japan
5. Department of Earth and Environmental Sciences; Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto; Kagoshima 890-0065 Japan