Paleoenvironmental reconstruction for termination stage of Superanoxia in Middle Triassic (Anisian) sedimentary sequence of the Mino belt, central Japan
Paleoenvironmental reconstruction for termination stage of Superanoxia in Middle Triassic (Anisian) sedimentary sequence of the Mino belt, central Japan
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DOI：
10.1111/iar.12262
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发表时间：
2018-07
期刊：
影响因子：
1.5
通讯作者：
Katsuhito Soda;T. Onoue
中科院分区：
文献类型：
--
作者：
Katsuhito Soda;T. Onoue
跨二叠纪/三叠纪边界的超缺氧是中二叠世晚期至中三叠世早期的一段较长时期的海洋缺氧，在二叠纪末大灭绝的背景下得到了很好的认识和争论。然而，由于地球化学指标的应用有限，对中三叠统缺氧的研究较少。为了重建超缺氧终止期的古环境变化，应用各种地球化学指标对日本Mino带中三叠统（Anisian）层状硅质岩序列的化学成分进行了分析，该层状硅质岩序列形成于泛海低-中纬度地区的深海海底环境。通过统计上可靠的地球化学指标，确定了中安尼期的3次缺氧事件。校准的化学风化强度度在这些缺氧事件中显示出较高的值，表明大陆风化加剧是中安尼世海洋缺氧事件的触发机制。此外，我们的数据表明，Panthalassa洋超缺氧的终止与中晚期大陆风化速率的逐渐降低有关。
Superanoxia across the Permian/Triassic boundary, which is a long period of oceanic anoxia from the late Middle Permian to the early Middle Triassic, has been recognized and debated well in the context of the end Permian mass extinction. However, few studies have focused on the Middle Triassic anoxia because of limited application of geochemical proxies. To reconstruct paleoenvironmental changes during the termination stage of Superanoxia, various geochemical proxies were applied to chemical compositions of the Middle Triassic (Anisian) bedded chert sequence in the Mino belt, Japan, which accumulated in a deep seafloor environment in a low‐ to mid‐latitude zone of the Panthalassa Ocean. Three anoxic events were identified by statistically robust geochemical proxies during the middle Anisian. Degrees of calibrated‐chemical weathering intensity show higher values during these anoxic events, suggesting that the intensified continental weathering was a trigger mechanism for the oceanic anoxic events in the middle Anisian. Furthermore, our data indicate that the termination of Superanoxia in the Panthalassa Ocean was associated with a gradual decrease in continental weathering rates during the middle to late Anisian.