[B-CG05] 地球史解読：冥王代から現代まで

[BCG05-14] 美濃帯の三畳紀／ジュラ紀境界における連続層序の改訂と古環境復元

*曽田 勝仁¹、冨松 由希²、尾上 哲治²、池原 実¹ (1.高知大学大学院教育研究部自然科学系理工学部門　高知大学海洋コア総合研究センター、2.九州大学理学研究院地球惑星科学部門)

The Triassic-Jurassic boundary (TJB) is marked by one of the big five biotic mass extinction events in the Phanerozoic. Anchoring at the TJB, previous stratigraphic framework in the Inuyama area of the Mino Belt established a floating astronomical time scale (ATS) converted from chert bed thickness variations. However, recent detailed stratigraphic studies indicated stratigraphic gaps by tectonic deformation across the TJB in the Inuyama ATS. Here we present paleoenvironmental reconstruction based on the revised continuous stratigraphy of the pelagic deep-sea rocks deposited in the Panthalassa across the TJB of the Mino Belt, central Japan. The several layers showed high Cr concentrations and low contents of redox sensitive elements in the latest Rhaetian, implying compositional effects from the Large Igneous Provinces and/or extraterrestrial impact. The Mg enrichment increased toward the Hettangian, suggesting enhanced inputs from the contemporaneous mafic materials like the Central Atlantic Magmatic Provinces. The low Mn enrichment indicated development of the reduced environment in the pelagic deep-sea realm of the Panthalassa during the latest Rhaetian.