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Early Cambrian oceanic oxygenation and evolution of early animals: A critical review from the South China Craton
Global and Planetary Change ( IF 4.0 ) Pub Date : 2021-07-02 , DOI: 10.1016/j.gloplacha.2021.103561
Ziheng Li 1 , Min Zhang 2 , Zhong-Qiang Chen 2 , Thomas J. Algeo 1, 2, 3 , Laishi Zhao 1 , Feifei Zhang 4
Affiliation  

Co-evolution of marine redox conditions and early animals during the early Cambrian was fundamental to the development of modern Earth ecosystem. Numerous Burgess Shale-type fossil Lagerstätten (i.e., the Chengjiang and Qingjiang biotas) in South China offer taphonomic windows to probe the evolutionary traits of early animals and marine redox variations, and to evaluate the relationship between the two during the Cambrian Ages 2 and 3 (~529 to 514 Ma). Here, we critically review records of various geochemical proxies and fossil assemblages from 24 Lagerstätten-bearing lower Cambrian sections representing a wide variety of depositional settings from the deep basin to inner shelf across the Nanhua Basin, South China. Geochemical redox proxies: Fe speciation, and Mo and U enrichment factors were utilized to reconstruct water depth-related redox gradients within the early Cambrian Nanhua Basin. The results show that a dynamic ‘euxinic wedge’ may have existed at the mid-depth, and its expansion/contraction may have controlled redox variations in the Nanhua Basin during the early Cambrian. The dramatic contraction of the euxinic wedge in the Cambrian Age 3 suggests that local oceanic oxygenated states coincided with the emergence of the Chengjiang and Qingjiang biotas. Meanwhile, a ~ 25‰ negative shift in pyrite sulfur isotopes deciphers a major increase in seawater sulfate availability, reflecting strongly enhanced subaerial oxidative weathering and/or a lower burial flux of pyrite. Concurrent variations in U and Mo isotopes support the global extent of this ocean oxygenation event. Accordingly, the global marine oxygenation may have facilitated the emergence of both ecologic complexity and biodiversification of early animals indicated by the Chengjiang and Qingjiang Lagerstätten in the early Cambrian (mainly Cambrian Age 3).



中文翻译:

早寒武世海洋氧化作用与早期动物演化:来自华南克拉通的批判性回顾

寒武纪早期海洋氧化还原条件和早期动物的共同进化是现代地球生态系统发展的基础。华南地区众多的伯吉斯页岩型化石Lagerstätten(即澄江和清江生物群)为探索早期动物的进化特征和海洋氧化还原变异,以及评估两者在寒武纪2和3纪之间的关系提供了埋藏学窗口(~529 至 514 Ma)。在这里,我们批判性地审查了来自 24 个含拉格施泰腾的下寒武统剖面的各种地球化学替代物和化石组合的记录,这些剖面代表了从深盆地到华南南华盆地内陆架的各种沉积环境。地球化学氧化还原代理:Fe 形态,利用Mo和U富集因子重建早寒武世南华盆地与水深相关的氧化还原梯度。结果表明,中深部可能存在动态的“euxinic楔”,其膨胀/收缩可能控制了早寒武世南华盆地氧化还原变化。寒武纪 3 期富氧楔的剧烈收缩表明局部海洋氧化状态与澄江和清江生物群的出现相吻合。同时,黄铁矿硫同位素的约 25‰ 负移解释了海水硫酸盐可用性的显着增加,反映了强烈增强的地下氧化风化和/或较低的黄铁矿埋藏通量。U 和 Mo 同位素的同时变化支持了这种海洋氧化事件的全球范围。因此,

更新日期:2021-07-07
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