Tostevin R, Wood R A, Shields G A, Poulton S W, Guilbaud R, Bowyer F, Penny A M, He T, Curtis A, Hoffmann K H, Clarkson M O
Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK.
School of GeoSciences, The University of Edinburgh, James Hutton Road, Edinburgh EH9 3FE, UK.
Nat Commun. 2016 Sep 23;7:12818. doi: 10.1038/ncomms12818.
The oceans at the start of the Neoproterozoic Era (1,000-541 million years ago, Ma) were dominantly anoxic, but may have become progressively oxygenated, coincident with the rise of animal life. However, the control that oxygen exerted on the development of early animal ecosystems remains unclear, as previous research has focussed on the identification of fully anoxic or oxic conditions, rather than intermediate redox levels. Here we report anomalous cerium enrichments preserved in carbonate rocks across bathymetric basin transects from nine localities of the Nama Group, Namibia (∼550-541 Ma). In combination with Fe-based redox proxies, these data suggest that low-oxygen conditions occurred in a narrow zone between well-oxygenated surface waters and fully anoxic deep waters. Although abundant in well-oxygenated environments, early skeletal animals did not occupy oxygen impoverished regions of the shelf, demonstrating that oxygen availability (probably >10 μM) was a key requirement for the development of early animal-based ecosystems.
新元古代（10亿至5.41亿年前）初期的海洋主要处于缺氧状态，但随着动物生命的兴起，海洋可能逐渐被氧化。然而，氧气对早期动物生态系统发展的控制作用仍不明确，因为先前的研究主要集中在确定完全缺氧或有氧的条件，而非中间的氧化还原水平。在此，我们报告了纳米比亚纳马群九个地点（约5.5亿至5.41亿年前）沿测深盆地断面的碳酸盐岩中保存的异常铈富集现象。结合基于铁的氧化还原指标，这些数据表明，在富氧表层水和完全缺氧深层水之间的狭窄区域存在低氧条件。尽管早期骨骼动物在富氧环境中数量众多，但它们并未占据陆架上缺氧的区域，这表明氧气供应（可能大于10微摩尔）是早期基于动物的生态系统发展的关键条件。
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