A short-lived oxidation event during the early Ediacaran and delayed oxygenation of the Proterozoic ocean
A short-lived oxidation event during the early Ediacaran and delayed oxygenation of the Proterozoic ocean
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DOI：
10.1016/j.epsl.2021.117274
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发表时间：
2021-11-11
影响因子：
5.3
通讯作者：
Zhu, Maoyan
中科院分区：
文献类型：
--
作者：
Chen, Bo;Hu, Chunlin;Zhu, Maoyan
埃迪卡拉纪的特点是主要的碳同位素扰动。其中最极端的，类似于570 Ma Shuram/DOUNCE（斗山沱负碳同位素偏移）异常，与与含氧海水范围暂时扩张有关的大型底栖动物的早期辐射相一致。在此，我们记录了华南长江三峡地区的早期负偏移（类似于 610 Ma WANCE（瓮安负碳同位素偏移））异常，该异常达到了同样极端的碳同位素值，并与类似程度的环境扰动相关。具体来说，新的铀同位素数据表明，随着碳同位素值的下降，向更多氧化条件的转变是显着但短暂的，而锶和硫同位素数据则支持大陆风化在偏移过程中的增加。我们利用生物地球化学建模方法来证明，这种风化脉冲流入富含有机物、很大程度上缺氧的海洋，完全再现了这些不同的同位素趋势。我们的研究直接支持了这样的假设，即大型溶解的海洋有机池有效地缓冲了元古代时期海洋环境的广泛氧化，从而大大延迟了地球上复杂需氧生命的辐射。 (C) 2021 Elsevier B.V. 保留所有权利。
The Ediacaran Period was characterised by major carbon isotope perturbations. The most extreme of these, the similar to 570 Ma Shuram/DOUNCE (Doushantuo Negative Carbon isotope Excursion) anomaly, coincided with early radiations of benthic macrofauna linked to a temporary expansion in the extent of oxygenated seawater. Here we document an earlier negative excursion (the similar to 610 Ma WANCE (Weng'An Negative Carbon isotope Excursion)) anomaly in the Yangtze Gorges area, South China, that reached equally extreme carbon isotope values and was associated with a similar degree of environmental perturbation. Specifically, new uranium isotope data evidence a significant, but transient, shift towards more oxygenated conditions in tandem with decreasing carbon isotope values, while strontium and sulfur isotope data support an increase in continental weathering through the excursion. We utilize a biogeochemical modelling approach to demonstrate that the influx of such a weathering pulse into an organically-laden, largely anoxic ocean, fully reproduces each of these distinct isotopic trends. Our study directly supports the hypothesis that a large dissolved marine organic pool effectively buffered against widespread oxygenation of the marine environment through the Proterozoic Eon, and in doing so, substantially delayed the radiation of complex aerobic life on Earth. (C) 2021 Elsevier B.V. All rights reserved.