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首页> 外文期刊>Paleoceanography >Upper ocean oxygenation dynamics from I/Ca ratios during the Cenomanian-Turonian OAE 2
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Upper ocean oxygenation dynamics from I/Ca ratios during the Cenomanian-Turonian OAE 2

机译：Canomanian-Turonian OAE 2期间I / Ca比值引起的上层海洋含氧量动态

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摘要

Global warming lowers the solubility of gases in the ocean and drives an enhanced hydrological cycle with increased nutrient loads delivered to the oceans, leading to increases in organic production, the degradation of which causes a further decrease in dissolved oxygen. In extreme cases in the geological past, this trajectory has led to catastrophic marine oxygen depletion during the so-called oceanic anoxic events (OAEs). How the water column oscillated between generally oxic conditions and local/global anoxia remains a challenging question, exacerbated by a lack of sensitive redox proxies, especially for the suboxic window. To address this problem, we use bulk carbonate I/Ca to reconstruct subtle redox changes in the upper ocean water column at seven sites recording the Cretaceous OAE 2. In general, I/Ca ratios were relatively low preceding and during the OAE interval, indicating deep suboxic or anoxic waters exchanging directly with near-surface waters. However, individual sites display a wide range of initial values and excursions in I/Ca through the OAE interval, reflecting the importance of local controls and suggesting a high spatial variability in redox state. Both I/Ca and an Earth System Model suggest that the northeast proto-Atlantic had notably higher oxygen levels in the upper water column than the rest of the North Atlantic, indicating that anoxia was not global during OAE 2 and that important regional differences in redox conditions existed. A lack of correlation with calcium, lithium, and carbon isotope records suggests that neither enhanced global weathering nor carbon burial was a dominant control on the I/Ca proxy during OAE 2.
机译：全球变暖降低了海洋中气体的溶解度，并通过增加向海洋输送的养分来驱动水文循环，从而增加了有机产量，有机物的降解导致溶解氧的进一步减少。在地质学的极端情况下，这种轨迹导致了所谓的海洋缺氧事件（OAEs）期间灾难性的海洋氧气耗竭。水柱如何在一般的有氧条件和局部/全局缺氧之间振荡仍然是一个具有挑战性的问题，由于缺乏敏感的氧化还原代理，尤其是对于亚氧化窗口，这种情况更加恶化。为了解决这个问题，我们使用大量碳酸盐I / Ca重建了记录白垩纪OAE 2的七个位置的上部海洋水柱中的细微氧化还原变化。通常，在OAE间隔之前和期间，I / Ca比值相对较低，表明与近地表水直接交换的深亚缺氧或缺氧水。但是，各个站点在整个OAE间隔内显示的I / Ca初始值和偏移范围很广，反映了局部控制的重要性，并暗示了氧化还原状态的高空间变异性。 I / Ca和地球系统模型均表明，东北原始大西洋的上层水柱中的氧气含量明显高于北大西洋其他地区，这表明OAE 2期间缺氧不是全球性的，并且氧化还原存在重要的区域差异存在条件。与钙，锂和碳同位素记录缺乏相关性表明，在OAE 2期间，I / Ca替代物对全球风化和碳埋藏的增强都不是主要控制。

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