Scarcity of chert in upper Lower Triassic Panthalassic deep-sea successions of Japan records elevated clastic inputs rather than depressed biogenic silica burial flux following the end-Permian extinction
Scarcity of chert in upper Lower Triassic Panthalassic deep-sea successions of Japan records elevated clastic inputs rather than depressed biogenic silica burial flux following the end-Permian extinction
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DOI：
10.1016/j.gloplacha.2020.103330
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发表时间：
2020-12
影响因子：
3.9
通讯作者：
Shun Muto;S. Takahashi;S. Yamakita;T. Onoue
中科院分区：
文献类型：
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作者：
Shun Muto;S. Takahashi;S. Yamakita;T. Onoue
与覆盖较老和较新地层的深海硅质岩为主的层序相比，沉积在泛海拉萨远洋区域的下三叠世沉积岩显示出异常丰富的粘土和二氧化硅贫乏的岩性。二叠纪末的大规模灭绝，影响了放射虫，已被提出作为一个解释，这个所谓的“硅质岩间隙”，通过其推断的生物硅生产的影响。为了检验这一假设，我们评估了线性沉积速率（LSR）的上Olenekian（上下三叠统）硅质粘土岩序列在筑美，大分县，日本西南部。牙形石生物层位的对比可以将华南地区以往研究获得的绝对年龄外推到我们所研究的剖面上。结果表明，下三叠统粘土岩的LSR值高于典型的中生代放射虫层状硅质岩。这意味着增加的碎屑物质的埋藏通量，而不是减少生物硅的埋藏通量，驱动富含粘土的沉积物在大洋泛地中海在奥伦尼克晚期沉积。
Lower Triassic sedimentary rocks deposited in pelagic regions of Panthalassa show anomalously clay-rich and silica-poor lithologies compared with the deep marine chert-dominated successions that characterise older and younger strata. The end-Permian mass extinction, which impacted radiolarians, has been proposed as an explanation for this so-called “chert gap” through its inferred impact on biogenic silica production. To test this hypothesis, we evaluated linear sedimentation rates (LSRs) for an upper Olenekian (upper Lower Triassic) siliceous claystone succession in Tsukumi, Oita Prefecture, Southwest Japan. Correlation of conodont biohorizons allows extrapolation of absolute ages obtained by previous studies in South China onto our studied sections. Results show that LSR is higher in the Lower Triassic claystone than in typical Mesozoic radiolarian bedded chert. This implies that increased burial flux of clastic material, not decreased biogenic silica burial flux, drove deposition of clay-rich sediments in pelagic Panthalassa during the late Olenekian.