Triassic marine Os isotope record from a pelagic chert succession, Sakahogi section, Mino Belt, southwest Japan

Tatsuo Nozaki, Takashi Nikaido, Tetsuji Onoue, Yutaro Takaya, Keiko Sato, Jun Ichi Kimura, Qing Chang, Daisuke Yamashita, Honami Sato, Katsuhiko Suzuki, Yasuhiro Kato, Atsushi Matsuoka

    Research output: Contribution to journalArticle

    Abstract

    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. Initial Os isotope ratios (187Os/188Os) have a wide range in this succession, from 0.197 to 0.813. The variations in this Os record are quite similar to those in the marine Sr isotope record for the same time period, although their amplitudes differ owing to the differing residence times of Os and Sr in the ocean. Together, our results and previous data trace a continuous Os isotope record for ca. 50 Myr starting in Anisian time. We document the following six notable features in the Os record, which also appear in the Sr record, and their interpretation: (1) a negative (unradiogenic) shift associated with euxinia in the latest Anisian reflecting late-stage Siberian Traps eruptions, (2) wide fluctuations from the latest Anisian to Ladinian induced by volcanism and by the late Ladinian humid pulse and volcanism of the Italian Volcanic Center, (3) a continuous decrease in the early Carnian during eruptions of the Wrangellia large igneous province, (4) stable unradiogenic values from the early to early middle Norian associated with a prolonged arid period, (5) a negative spike in the middle Norian associated with the Manicouagan impact event, and (6) a broad rise and fall from the earliest late Norian to the Rhaetian ages, attributed to the Cimmerian-Indosinian orogeny and subsequent volcanism of the Central Atlantic Magmatic Province.

    Original languageEnglish
    Article number100004
    JournalJournal of Asian Earth Sciences: X
    DOIs
    Publication statusAccepted/In press - 2019 Jan 1

    Fingerprint

    chert
    Triassic
    isotope
    Anisian
    Norian
    Ladinian
    volcanism
    large igneous province
    volcanic eruption
    Cimmerian
    Rhaetian
    Carnian
    secular variation
    orogeny
    oceanic crust
    residence time
    global warming
    seafloor
    seawater
    ocean

    Keywords

    • Accretionary complex
    • Chert
    • Re-Os isotope
    • Sakahogi section
    • Southwest Japan
    • Triassic

    ASJC Scopus subject areas

    • Geology
    • Earth-Surface Processes

    Cite this

    Triassic marine Os isotope record from a pelagic chert succession, Sakahogi section, Mino Belt, southwest Japan. / Nozaki, Tatsuo; Nikaido, Takashi; Onoue, Tetsuji; Takaya, Yutaro; Sato, Keiko; Kimura, Jun Ichi; Chang, Qing; Yamashita, Daisuke; Sato, Honami; Suzuki, Katsuhiko; Kato, Yasuhiro; Matsuoka, Atsushi.

    In: Journal of Asian Earth Sciences: X, 01.01.2019.

    Research output: Contribution to journalArticle

    Nozaki, Tatsuo ; Nikaido, Takashi ; Onoue, Tetsuji ; Takaya, Yutaro ; Sato, Keiko ; Kimura, Jun Ichi ; Chang, Qing ; Yamashita, Daisuke ; Sato, Honami ; Suzuki, Katsuhiko ; Kato, Yasuhiro ; Matsuoka, Atsushi. / Triassic marine Os isotope record from a pelagic chert succession, Sakahogi section, Mino Belt, southwest Japan. In: Journal of Asian Earth Sciences: X. 2019.
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    abstract = "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. Initial Os isotope ratios (187Os/188Os) have a wide range in this succession, from 0.197 to 0.813. The variations in this Os record are quite similar to those in the marine Sr isotope record for the same time period, although their amplitudes differ owing to the differing residence times of Os and Sr in the ocean. Together, our results and previous data trace a continuous Os isotope record for ca. 50 Myr starting in Anisian time. We document the following six notable features in the Os record, which also appear in the Sr record, and their interpretation: (1) a negative (unradiogenic) shift associated with euxinia in the latest Anisian reflecting late-stage Siberian Traps eruptions, (2) wide fluctuations from the latest Anisian to Ladinian induced by volcanism and by the late Ladinian humid pulse and volcanism of the Italian Volcanic Center, (3) a continuous decrease in the early Carnian during eruptions of the Wrangellia large igneous province, (4) stable unradiogenic values from the early to early middle Norian associated with a prolonged arid period, (5) a negative spike in the middle Norian associated with the Manicouagan impact event, and (6) a broad rise and fall from the earliest late Norian to the Rhaetian ages, attributed to the Cimmerian-Indosinian orogeny and subsequent volcanism of the Central Atlantic Magmatic Province.",
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    AU - Nozaki, Tatsuo

    AU - Nikaido, Takashi

    AU - Onoue, Tetsuji

    AU - Takaya, Yutaro

    AU - Sato, Keiko

    AU - Kimura, Jun Ichi

    AU - Chang, Qing

    AU - Yamashita, Daisuke

    AU - Sato, Honami

    AU - Suzuki, Katsuhiko

    AU - Kato, Yasuhiro

    AU - Matsuoka, Atsushi

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    N2 - 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. Initial Os isotope ratios (187Os/188Os) have a wide range in this succession, from 0.197 to 0.813. The variations in this Os record are quite similar to those in the marine Sr isotope record for the same time period, although their amplitudes differ owing to the differing residence times of Os and Sr in the ocean. Together, our results and previous data trace a continuous Os isotope record for ca. 50 Myr starting in Anisian time. We document the following six notable features in the Os record, which also appear in the Sr record, and their interpretation: (1) a negative (unradiogenic) shift associated with euxinia in the latest Anisian reflecting late-stage Siberian Traps eruptions, (2) wide fluctuations from the latest Anisian to Ladinian induced by volcanism and by the late Ladinian humid pulse and volcanism of the Italian Volcanic Center, (3) a continuous decrease in the early Carnian during eruptions of the Wrangellia large igneous province, (4) stable unradiogenic values from the early to early middle Norian associated with a prolonged arid period, (5) a negative spike in the middle Norian associated with the Manicouagan impact event, and (6) a broad rise and fall from the earliest late Norian to the Rhaetian ages, attributed to the Cimmerian-Indosinian orogeny and subsequent volcanism of the Central Atlantic Magmatic Province.

    AB - 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. Initial Os isotope ratios (187Os/188Os) have a wide range in this succession, from 0.197 to 0.813. The variations in this Os record are quite similar to those in the marine Sr isotope record for the same time period, although their amplitudes differ owing to the differing residence times of Os and Sr in the ocean. Together, our results and previous data trace a continuous Os isotope record for ca. 50 Myr starting in Anisian time. We document the following six notable features in the Os record, which also appear in the Sr record, and their interpretation: (1) a negative (unradiogenic) shift associated with euxinia in the latest Anisian reflecting late-stage Siberian Traps eruptions, (2) wide fluctuations from the latest Anisian to Ladinian induced by volcanism and by the late Ladinian humid pulse and volcanism of the Italian Volcanic Center, (3) a continuous decrease in the early Carnian during eruptions of the Wrangellia large igneous province, (4) stable unradiogenic values from the early to early middle Norian associated with a prolonged arid period, (5) a negative spike in the middle Norian associated with the Manicouagan impact event, and (6) a broad rise and fall from the earliest late Norian to the Rhaetian ages, attributed to the Cimmerian-Indosinian orogeny and subsequent volcanism of the Central Atlantic Magmatic Province.

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