Abstract Widespread oceanic anoxia has been implicated as a killing mechanism during the end-Permian mass extinction (EPME). A high-resolution investigation of pyrite framboids and bioturbation structures in the Shangsi section of South China has revealed repeated and frequent fluctuations of coupled anoxic/euxinic to dysoxic/oxic episodes in the latest Permian, immediately preceding the EPME. Anoxic bottom waters and interstitial water conditions are documented by the smallest pyrite framboids (3–5 μm) and the absence of bioturbation, and dysoxic bottom waters and anoxic interstitial waters are inferred from larger pyrite framboids (6–10 μm) and the occurrence of Zoophycos. In comparison, oxic conditions for both bottom waters and interstitial waters are revealed by a high bioturbation index (BI = 4) and the occurrence of mid-tier Thalassinoides. Fluctuating pyrite framboid sizes and bioturbation structures suggest that bottom and interstitial oxygen levels were neither fully, nor persistently, anoxic/euxinic before the EPME, and instead recorded frequent periodic fluctuations between anoxic/euxinic and dysoxic/oxic conditions. The paleoceanic redox variation appears to correlate with the 405-ka eccentricity cycles in the anhysteretic remanent magnetization (ARM) series, suggesting that fluctuations might have been controlled by Milankovitch cycles. The role of fluctuations between anoxic/euxinic and dysoxic/oxic episodes in the latest Permian to the EPME is unclear, but it seems plausible that they represent a prelude to the highly stressed conditions that are characteristic of the EPME.

中文翻译：

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最近二叠纪海洋含氧量的周期性波动

摘要 广泛的海洋缺氧被认为是二叠纪末大灭绝 (EPME) 期间的一种杀戮机制。对华南上寺段黄铁矿小枝状体和生物扰动结构的高分辨率调查显示，在紧接 EPME 之前的最新二叠纪，缺氧/富氧与缺氧/有氧事件的耦合反复和频繁波动。缺氧底水和间隙水条件由最小的黄铁矿小枝状体（3-5 μm）和没有生物扰动记录，而缺氧底水和缺氧间隙水是从较大的黄铁矿小枝状体（6-10 μm）和动物藻类。相比之下，高生物扰动指数 (BI = 4) 和中层 Thalassinoides 的出现揭示了底水和间隙水的含氧条件。波动的黄铁矿小叶形尺寸和生物扰动结构表明，在 EPME 之前，底部和间隙氧水平既不是完全的，也不是持续的缺氧/富氧，而是记录了缺氧/富氧和缺氧/有氧条件之间的频繁周期性波动。古海洋氧化还原变化似乎与无磁滞剩磁 (ARM) 系列中的 405-ka 偏心率循环相关，这表明波动可能已被米兰科维奇循环控制。在 EPME 的最新二叠纪中，缺氧 / euxinic 和缺氧 / 缺氧事件之间波动的作用尚不清楚，但它们似乎是 EPME 特有的高度压力条件的前奏。