The widespread Capitanian (late Guadalupian) marine anoxia/euxinia has long been regarded as a key driver of the end-Guadalupian (middle Permian) biotic crisis. However, the cause of this marine anoxia is debated, particularly regarding the influence of the Emeishan large igneous province (ELIP). To investigate the contribution of the ELIP to marine anoxia and the possible causal mechanisms, we undertook a conodont biostratigraphic and geochemical study of the middle Permian Maokou Formation in a platform-to-trough transect in the Upper Yangtze region, South China. Our results show that the depositional facies of the Maokou Formation changed from a carbonate ramp to an intra-platform trough within the Jinogondolella (J.) altudaensis zone in the northwestern Yangtze region, which can be attributed to the initial activity of the ELIP. Mantle-derived Sr inputs in the initial and main stages of the ELIP led to two decreases in 87Sr/86Sr during the Capitanian, in the J. shannoni–J. altudaensis and J. prexuanhanensis–J. xuanhanensis zones. The elevated 87Sr/86Sr values during the late Capitanian may have been due to enhanced continental weathering caused by rapid climate warming in response to subaerial eruptions of the ELIP. The deep-water anoxia–euxinia expanded during the middle Capitanian, as indicated by increased MoEF/UEF and V/(V + Ni) values, along with the disappearance of burrows and appearance of small pyrite framboids in the J. altudaensis zone in the Cheng 20 well. However, shallow-water anoxia occurred during the late Capitanian (i.e., J. prexuanhanensis–J. xuanhanensis zone), as evidenced by positive Ce anomalies and losses of aerobic benthic species in the Erya section. Importantly, marine anoxia and negative δ13Ccarb excursions occurred synchronously, but earlier in deep water than in shallow water, potentially indicating an expansion of the oxygen minimum zone (OMZ). The deep-water anoxia corresponded to a decrease in 87Sr/86Sr ratios and the appearance of an intra-platform trough in the J. altudaensis zone, whereas the shallow-water anoxia in the late Capitanian coincided with elevated 87Sr/86Sr ratios. This suggests that the initial activity of the ELIP promoted the development of the OMZ in deep waters during the middle Capitanian, while the subaerial eruptions of the ELIP drove climate warming that led to the expansion of the OMZ into shallow-water platforms during the late Capitanian.

中文翻译：

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峨眉山大火成岩省对长江上游地区卡皮塔尼海洋缺氧的潜在影响


长期以来，广泛分布的 Capitanian （晚期瓜达卢普纪） 海洋缺氧/euxinia 一直被认为是瓜达卢普纪末（二叠纪中期）生物危机的关键驱动因素。然而，这种海洋缺氧的原因存在争议，特别是关于峨眉山大火成岩省 （ELIP） 的影响。为了研究 ELIP 对海洋缺氧的贡献和可能的致病机制，我们对华南上长江地区二叠统中期茅口组平台到槽样带进行了锥齿生物地层学和地球化学研究。结果表明：在长江西北部地区 Jinogondolella （J.） altudaensis 带内，茅口组的沉积相由碳酸盐斜坡转变为台内槽，这可归因于 ELIP 的初始活动。在 ELIP 的初始和主要阶段，地幔衍生的 Sr 输入导致 87Sr/86Sr 在 Capitanian，在 J. shannoni-J. altudaensis 和 J. prexuanhanensis-J. xuanhanensis 区。卡皮塔尼世晚期 87Sr/86Sr 值升高可能是由于 ELIP 的海底喷发导致气候快速变暖导致大陆风化增强。深水缺氧-euxinia 在开普塔尼中期扩大，如 MoEF/UEF 和 V/（V + Ni） 值增加所表明，同时在 Cheng 20 井的 J. altudaensis 区中洞穴消失和小黄铁矿碎屑的出现。然而，浅水缺氧发生在 Capitanian 晚期（即 J. prexuanhanensis-J. xuanhanensis 带），Erya 剖面的阳性 Ce 异常和好氧底栖物种的损失证明了这一点。 重要的是，海洋缺氧和负 δ13Ccarb 偏移同时发生，但在深水中比在浅水中更早，这可能表明最低氧区 （OMZ） 的扩大。深水缺氧对应于 J. altudaensis 带 87Sr/86Sr 比值的降低和平台内槽的出现，而 Capitanian 晚期的浅水缺氧与 87Sr/86Sr 比值的升高相吻合。这表明，ELIP 的初始活动促进了 OMZ 在开皮塔尼中期深水区的发展，而 ELIP 的海底喷发推动了气候变暖，导致 OMZ 在开皮塔尼晚期扩展到浅水平台。