Development of a high-productivity and anoxic-euxinic condition during the late Guadalupian in the Lower Yangtze region: Implications for the mid-Capitanian extinction event
Development of a high-productivity and anoxic-euxinic condition during the late Guadalupian in the Lower Yangtze region: Implications for the mid-Capitanian extinction event
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DOI：
10.1016/j.palaeo.2018.01.021
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发表时间：
2018-01
期刊：
影响因子：
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通讯作者：
Bolin Zhang;S. Yao;Wenxuan Hu;H. Ding;Biao Liu;Yongle Ren
中科院分区：
文献类型：
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作者：
Bolin Zhang;S. Yao;Wenxuan Hu;H. Ding;Biao Liu;Yongle Ren
广泛的海洋缺氧被认为是卡皮坦中期大规模灭绝的最重要原因之一。然而，卡皮坦中期大规模灭绝的机制和随后的硫化过程仍然存在争议。在此，我们基于多种地球化学指标，重点对卡皮坦中期大灭绝期间下扬子地区的海洋生产力和氧化还原条件进行了综合研究。我们的结果表明，氧化还原条件和海洋生产力经历了三个阶段。灭绝前的早中期卡皮坦阶以缺氧条件为主，间歇性强生条件和中高生产力；而中期卡皮坦阶则以较强的强生条件和较高的生产力为主。随后，中卡皮坦阶所有这些地球化学指标的显着下降表明了浅水含氧环境和生产力低下。缺氧-常氧条件的出现和发展可能是由于与上升流增强相关的高生产力引起的，这导致异养呼吸的加强和随后水体的氧气消耗。峨眉山大火成岩省喷发导致的全球变暖导致海洋环流更加缓慢，大退退导致化跃层向上运动，也进一步加剧了中卡皮坦阶的环境条件。这些环境条件的发展可能在引发海洋超缺氧方面发挥了重要作用，并且与卡皮坦中期生物危机同时发生，这表明它们之间可能存在因果关系。尽管瓜达卢普世晚期硫化物过程的时空非均质性仍存在争议，但通过对全球剖面的综合分析，可以建立硫化物模型，表明硫化物水在早中卡皮坦世首先出现在深水，并在中晚期卡皮坦世浅水至浅水。
Widespread marine anoxia is considered one of the most important causes for the mid-Capitanian mass extinction. However, the mechanisms and subsequent sulfidic process for the mid-Capitanian mass extinction are still debated. Here, we focus on a comprehensive study including marine productivity and redox conditions of the Lower Yangtze area across the mid-Capitanian mass extinction based on multiple geochemical indicators. Our results show that the redox conditions and marine productivity have gone through three stages. The pre-extinction early-middle Capitanian is characterized by anoxic conditions with intermittent euxinic episodes and moderate-high productivity, whereas the middle Capitanian is dominated by stronger euxinic conditions and higher productivity. Subsequently, an oxic shallow water environment and low productivity are recognized by significant decreases in all of these geochemical indicators across the mid-Capitanian. The appearance and development of the anoxic-euxinic conditions was probably caused by high productivity related to enhanced upwelling, which led to the intensified heterotrophic respiration and subsequent oxygen-depletion of the water column. More sluggish oceanic circulation that resulted from the global warming associated with the eruption of the Emeishan Large Igneous Province and upward movement of the chemocline due to great regression also further exacerbated the euxinic conditions during the middle Capitanian. The development of these euxinic conditions may have played a major role in triggering the super-anoxic ocean and is also coincident with the mid-Capitanian biotic crisis, which suggests the possible causal link between them. With comprehensive analysis of profiles across the globe, sulfidic models showing that the sulfidic water first occurred in the deep water during the early-middle Capitanian and shoaled to shallow water in the middle-late Capitanian could be established, despite the fact that the temporally and spatially heterogeneous sulfidic processes in the late Guadalupian are still debated.