[M-IS15] Evolution of Pelagic Realm

[MIS15-04] Triassic marine Os isotope record reconstructed from a pelagic chert succession, Sakahogi section, Mino Belt, southwest Japan

★Invited Papers

*Tatsuo Nozaki^1,2,3,4, Takashi Nikaido⁵, Tetsuji Onoue⁶, Yutaro Takaya^7,1,2,4, Keiko Sato¹, Jun-Ichi Kimura⁸, Qing Chang⁸, Daisuke Yamashita⁶, Honami Sato^4,1, Katsuhiko Suzuki¹, Yasuhiro Kato^2,4, Atsushi Matsuoka⁵ (1.JAMSTEC/R&D CSR, 2.Univ. of Tokyo, 3.Kobe Univ., 4.ChibaTech, 5.Niigata Univ., 6.Kumamoto Univ., 7.Waseda Univ., 8.JAMSTEC/D-SEG)

Keywords:Chert, Re-Os isotope, Triassic, Accretionary complex, Mino Belt, Southwest Japan

Pelagic cherts preserved in accretionary complexes represent former seafloor sediment that can retain geochemical evidence of paleoceanographic conditions that predate the oldest extant oceanic crust. The ratio of Os isotopes in seawater, in particular, is of wide interest as a source of insight into notable geologic events such as oceanic anoxic events, rapid global warming episodes, and eruption of large igneous provinces, but marine Os isotope records from before 80 Ma are scarce. We present a record of secular variations of marine Os isotope ratios from a thick, continuous succession of Middle and Upper Triassic pelagic chert in the Sakahogi section of the Mino Belt accretionary complex.