Japan Geoscience Union Meeting 2015

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Oral

Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS30] Evolution of the Pelagic Realm

Tue. May 26, 2015 9:00 AM - 10:45 AM 304 (3F)

Convener:*Atsushi Matsuoka(Department of Geology, Faculty of Science, Niigata University), Toshiyuki Kurihara(Graduate School of Science and Technology, Niigata University), Yasuhiro Kato(Department of Systems Innovation, Graduate School of Engineering, University of Tokyo), Tetsuji Onoue(Earth and Environmental Sciences, Graduate School of Science and Technology, Kumamoto University), Katsunori Kimoto(Japan Agency for Marine-Earth Science and Technology), Tatsuo Nozaki(Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology), Hayato Ueda(Department of Geology, Niigata University), Kenta Kobayashi(Department of Geology, Faculty of Science, Niigata University), Takashi Hasegawa(Division of Global Environmental Science and Engineering, Graduate School of Natural Science and Technology, Kanazawa University), Chair:Hayato Ueda(Department of Geology, Niigata University), Satoshi Takahashi(Department of Earth and Planetary Science, University of Tokyo)

10:00 AM - 10:15 AM

[MIS30-05] Carbon isotope record from the Upper Triassic bedded chert in the Mino Belt, central Japan

*Tetsuji ONOUE1, Minoru IKEHARA2, Katsuhito SODA1, Daisuke YAMASHITA1 (1.Kumamoto University, 2.Center for Advanced Marine Core Research, Kochi University)

Keywords:Triassic, bedded chert, carbon isotope

The Late Triassic was characterized by several marine and terrestrial biotic turnover events prior to the end-Triassic mass extinction. The causes of the end-Triassic mass extinction and these Norian to Rhaetian biotic turnover events are still the subject of debate. In order to infer the Norian to Rhaetian (Late Triassic) environmental changes in a pelagic realm of the Panthalassa Ocean, the stratigraphic variations of TOC and δ13Corg of the bedded chert succession in the Sakahogi section were examined. The Sakahogi section (~26 m in thickness) crops out in the Mino Belt, central Japan, and consists of the red to greenish-gray bedded chert. The radiolarian biostratigraphy indicates a middle Norian to Rhaetian age of the bedded chert. The bedded chert of the Sakahogi section is reconstructed as a deep-sea sediment of pelagic facies forms in an open ocean realm of the Panthalassa Ocean. Our analysis shows that the middle Norian samples record stable vaues until the late middle Norian. This stability is disturbed by a small negative δ13Corg excursion at the middle Norian ejecta layer (Sakahogi ejecta). TOC values increase across the middle and upper Norian boundary interval. This interval is marked by a minor increase in δ13Corg value (~1 ‰).