Phosphorus-limited conditions in the early Neoproterozoic ocean maintained low levels of atmospheric oxygen
Phosphorus-limited conditions in the early Neoproterozoic ocean maintained low levels of atmospheric oxygen
复制标题
新元古代早期海洋中磷的限制条件维持低水平的大气氧
DOI：
10.1038/s41561-020-0548-7
复制
发表时间：
2020-03-02
影响因子：
18.3
通讯作者：
Lenton, Timothy M.
中科院分区：
文献类型：
--
作者：
Guilbaud, Romain;Poulton, Simon W.;Lenton, Timothy M.
在新元古代早期（大约10亿至8亿年前），缺氧大陆边缘环境的氧化还原化学从广泛的含硫化物（富氧）状态演变为全球性的含铁（含铁）状态。海洋氧化还原化学对磷（一种限制性营养物）的地球化学循环以及初级生产具有很强的控制作用，但磷循环对这一主要海洋氧化还原转变的响应尚未得到研究。在这里，我们使用地球化学形态技术，以探讨磷的相分配在一个开放的海洋，从淮南盆地，中国北方新元古代早期序列。我们发现，有效地去除生物可利用的磷与铁矿物在全球铁质海洋导致贫营养（营养有限）的条件下，因此可能在全球范围内减少初级生产，有机碳埋葬，随后，氧气生产。然而，磷的可用性和有机碳埋藏足以维持氧化气氛。这些数据意味着大量的营养驱动的变化，在大气中的氧气水平，通过元古代，而不是稳定的水平通常invoked.Early新元古代海洋生产力下降，由于营养下降后，从富含铁的切换到硫化物丰富的海洋，根据记录磷地球化学测量沉积剖面在中国北方。
The redox chemistry of anoxic continental margin settings evolved from widespread sulfide-containing (euxinic) conditions to a global ferruginous (iron-containing) state in the early Neoproterozoic era (from similar to 1 to 0.8 billion years ago). Ocean redox chemistry exerts a strong control on the biogeochemical cycling of phosphorus, a limiting nutrient, and hence on primary production, but the response of the phosphorus cycle to this major ocean redox transition has not been investigated. Here, we use a geochemical speciation technique to investigate the phase partitioning of phosphorus in an open marine, early Neoproterozoic succession from the Huainan Basin, North China. We find that effective removal of bioavailable phosphorus in association with iron minerals in a globally ferruginous ocean resulted in oligotrophic (nutrient limited) conditions, and hence a probable global decrease in primary production, organic carbon burial and, subsequently, oxygen production. Nevertheless, phosphorus availability and organic carbon burial were sufficient to maintain an oxidizing atmosphere. These data imply substantial nutrient-driven variability in atmospheric oxygen levels through the Proterozoic, rather than the stable levels commonly invoked.Early Neoproterozoic marine productivity fell due to nutrient drawdown following a switch from an iron-rich to a sulfide-rich ocean, according to records of phosphorus geochemistry measured from sedimentary sections in North China.