First record of the early Toarcian oceanic anoxic event in the Hebrides Basin (UK) and implications for redox and weathering changes
First record of the early Toarcian oceanic anoxic event in the Hebrides Basin (UK) and implications for redox and weathering changes
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DOI：
10.1016/j.gloplacha.2021.103685
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发表时间：
2021-10
影响因子：
3.9
通讯作者：
Wenhan Chen;D. Kemp;Tianchen He;Chunju Huang;Simin Jin;Yijun Xiong;R. Newton
中科院分区：
文献类型：
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作者：
Wenhan Chen;D. Kemp;Tianchen He;Chunju Huang;Simin Jin;Yijun Xiong;R. Newton
早期Toarcian（~183 Ma）的特点是一个突出的火山活动引起的变暖事件与大量增加的12 C-富集的碳的海洋-大气系统。这种变暖可能导致了这段时间海洋的明显脱氧，这一事件因此被命名为：早期托阿西亚海洋缺氧事件（T-OAE）。虽然T-OAE已得到全球的认可，但已注意到该事件的性质及其环境影响存在明显的地理差异。在这里，我们提出了新的碳同位素，元素丰度和有机地球化学数据，从一个较低的Toarcian继承的岛屿，苏格兰（赫布里底群岛盆地，西北欧大陆架）。这些数据提供了苏格兰T-OAE的第一个证据。继承一般富含有机质通过T-OAE间隔，虽然氧化还原敏感的微量元素数据表明，氧-亚氧底层水条件占上风，可能穿插短暂的缺氧事件。我们的元素数据对比与证据持续缺氧/euxinia在附近的盆地，并强调如何脱氧是空间可变的，并依赖于水深和盆地水文。同样，这些数据强调缺氧是如何不是一个先决条件的沉积有机丰富的岩性在T-OAE。沉积学证据，再加上无机地球化学数据，表明增加粗粒碎屑通量和增强化学风化在T-OAE。我们的研究结果支持新出现的证据表明，在T-OAE期间，全球热带和亚热带地区的水文循环明显加强，风暴增加，以应对全球变暖。
The early Toarcian (~183 Ma) was characterized by a prominent volcanism-induced warming event associated with a massive addition of12C-enriched carbon to the ocean-atmosphere system. This warming likely contributed to marked ocean deoxygenation during this time, giving the event its name: the early Toarcian Oceanic Anoxic Event (T-OAE). Although the T-OAE has been recognized globally, clear geographic differences in the character of the event and its environmental effects have been noted. Here we present new carbon isotope, element abundance and organic geochemical data from a lower Toarcian succession on the Isle of Raasay, Scotland (Hebrides Basin, Northwest European Shelf). These data provide the first evidence of the T-OAE in Scotland. The succession is generally enriched in organic matter through the T-OAE interval, though redox-sensitive trace element data indicate that oxic-suboxic bottom water conditions prevailed, potentially interspersed with ephemeral anoxic episodes. Our elemental data contrast with evidence for persistent anoxia/euxinia in nearby basins, and emphasize how deoxygenation was spatially variable and dependent on water depth and basin hydrography. Similarly, the data emphasize how anoxia was not a prerequisite for the deposition of organic-rich lithologies during the T-OAE. Sedimentological evidence, coupled with inorganic geochemical data, indicates increased coarse-grained detrital flux and enhanced chemical weathering during the T-OAE. Our findings support emerging evidence for a marked strengthening of hydrological cycling and increased storminess at tropical and subtropical latitudes globally in response to global warming during the T-OAE.