Japan Geoscience Union Meeting 2015

Presentation information

Print

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)

9:15 AM - 9:30 AM

[MIS30-02] Non-sulphidic anoxic conditions in the end-Early Triassic deep sea

*Satoshi TAKAHASHI1, Shin-ichi YAMASAKI2, Kazuhiro OGAWA3, Kunio KAIHO3, Noriyoshi TSUCHIYA2 (1.Department of Earth and Planetary Science, University of Tokyo, 2.Graduate School of Environmental Studies, Tohoku University,, 3.Graduate School of Science, Tohoku University)

Keywords:pelagic deep-sea, oceanic anoxia, trace element, Triassic, carbon isotope

This study focuses on an upper Lower Triassic (Spathian) to lowermost Middle Triassic (Anisian) section representing the central Panthalassic deep sea. Analysed organic carbon isotope ratio (δ13Corg) records from the section demonstrate that lower values in the Spathian increase by up to 6‰ at the Spathian–Anisian transition. This trend accords with the carbonate carbon isotope (δ13Ccarb) record from shallow water carbonate sections. The end of the Early Triassic trough of δ13Corg consists of black chert deposits sandwiched by black claystone beds in the study section. In these black-coloured beds and underlying siliceous claystone beds, higher concentrations of redox-sensitive elements, such as Mo and V, and coinciding low sulphide sulphur isotope ratios (δ34Ssulphide) and previously reported sulphur-bearing organic compounds are present, suggesting anoxic deep water. As enrichment factors of Mo are not higher than the typical sulphidic trend, these anoxic conditions did not become sulphidic. Oxygen-poor conditions coinciding with a carbon isotope trough have been also reported in late Early Triassic strata from shallow-water sections. These coincidences imply global environmental perturbations related to the delayed recovery of life after the end-Permian mass extinction.