| Co-Investigator(Kenkyū-buntansha) |
HISADA Ken-ichiro Institute of Geoscience, University of Tsukuba, 地球科学系, 講師 (50156585)
HASEGAWA Shiro Graduate School of environmental earth Science, Hokkaido University, 大学院・地球環境科学研究科, 助教授 (90142918)
SUZUKI Noriyuki Graduate School of Science, Hokkaido University, 大学院・理学研究科・地球惑星科学, 助教授 (00144692)
KOIZUMI Itaru Graduate School of Science, Hokkaido University, 大学院・理学研究科・地球惑星科学, 教授 (20029721)
BARINOV K Geological Institute of the Russian Academy of Sciences, 属序研究部, 研究員
GLADENKOV Yu.B Geological Institute of the Russian Academy of Sciences, 属序研究部, 部長
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| Research Abstract |
In order to reconstruct the late Cenozoic paleoenvironmental history in the Sea of Okhotsk area, such two sections in Sakhalin as the Makarov and Schmidt Peninsula investigated from paleontological and geological point of views. On the basis of detailed columnar sections (1 : 1000 scale), samples for bio-and chrono-stratigraphical analysis collected more than 500 localities in Makarov region in 1995 and in Schmidt Peninsula in 1996. Paleontological studies such as Diatom, benthic Foraminifera, Mollusca, Pollen, Dinoflagellate have done as coupled with sedimentological studies (facies's analysis, heavy minerals and geochemical analysis). As the result, the Oligocene to Pliocene lithostratigraphy and biostratigraphy of the studied areas were established. A big chronological gape was first recognized between the Chefov and Verkhne Due Formation in Makarov region on the basis of the Dinoflagellate and Pollen biostratigraphy. The Ar-Ar dating, 22-23 Ma of the basaltic rocks from the Chefov Formation may indicated the initial rifting stage of the Sea of Okhotsk. The beds corresponding to the first mid-Neogene climatical optimum were recognized in the Verkhne Due Formation in Makarov region and Pili Formation in the Shmidt Peninsula based on benthic fossils and pollens. The Denticulopsis hyalina Zone was recognized both from the Maruyama (Makarov region) and Pili (Schmidt Peninsula) Formations, respectively. Molluscs occurred from the Machigar Formation in Schmidt Peninsula were comparable with those of the Oligocene Asagai Fauna of Japan. Consequently, the Cenozoic paleoenvironmental history of the Sea of Okhotsk area was well understood in reference to that of the Japanese Islands and Northern Pacific.
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