The Great Oxidation Event preceded a Paleoproterozoic "snowball Earth"
The Great Oxidation Event preceded a Paleoproterozoic "snowball Earth"
复制标题
大氧化事件发生在古元古代“雪球地球”之前
DOI：
10.1073/pnas.2003090117
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发表时间：
2020-06-16
影响因子：
11.1
通讯作者：
Claire, Mark W.
中科院分区：
文献类型：
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作者：
Warke, Matthew R.;Di Rocco, Tommaso;Claire, Mark W.
由于无法确定地球历史上两个关键事件——古元古代大氧化事件（GOE）和第一次“雪球地球”全球冰川作用之间的确切时间关系，因此无法评估大气成分变化与古代气候变化之间的因果关系。在这里，我们提出了俄罗斯西北部芬诺斯坎迪亚地盾古元古代 Seidorechka 和 Polisarka 沉积地层的时间分辨四重硫同位素测量（Delta S-34、Delta S-33 和 Delta S-36），以解决这一问题。前者中的硫化物保留了硫同位素质量无关分馏（S-MIF）的证据，其落在太古宙参考阵列的不确定度范围内，Delta S-36/Delta S-33斜率为-1.8，并且具有较小的负.33S值，而在后者中，硫同位素的质量依赖性分馏（S-MDF）很明显，Delta S-36/Delta S-33斜率为-8.8。这些趋势与地质年代学限制相结合，将 S-MIF/S-MDF 转变（GOE 的关键指标）置于 2,501.5 +/- 1.7 Ma 和 2,434 +/- 6.6 Ma 之间。这些是 S-MIF/S-MDF 转变迄今为止最严格的时间和地层限制，表明芬诺斯坎迪亚的转变时间与北美和南非的 S-MIF/S-MDF 转变一致。此外，Polisarka 地层的冰川部分出现在含有 S-MDF 信号的沉积层上方 60 m 处。因此，我们的研究结果明确证实 S-MIF/S-MDF 转变发生在古元古代雪球地球之前。这种时间关系的解决限制了地球氧合的因果驱动因素，特别是排除了全球冰川作用先于或导致含氧光合作用进化的概念模型。
The inability to resolve the exact temporal relationship between two pivotal events in Earth history, the Paleoproterozoic Great Oxidation Event (GOE) and the first "snowball Earth" global glaciation, has precluded assessing causality between changing atmospheric composition and ancient climate change. Here we present temporally resolved quadruple sulfur isotope measurements (delta S-34, Delta S-33, and Delta S-36) from the Paleoproterozoic Seidorechka and Polisarka Sedimentary Formations on the Fennoscandian Shield, northwest Russia, that address this issue. Sulfides in the former preserve evidence of massindependent fractionation of sulfur isotopes (S-MIF) falling within uncertainty of the Archean reference array with a Delta S-36/Delta S-33 slope of -1.8 and have small negative.33S values, whereas in the latter mass-dependent fractionation of sulfur isotopes (S-MDF) is evident, with a Delta S-36/Delta S-33 slope of -8.8. These trends, combined with geochronological constraints, place the S-MIF/S-MDF transition, the key indicator of the GOE, between 2,501.5 +/- 1.7 Ma and 2,434 +/- 6.6 Ma. These are the tightest temporal and stratigraphic constraints yet for the S-MIF/S-MDF transition and show that its timing in Fennoscandia is consistent with the S-MIF/S-MDF transition in North America and South Africa. Further, the glacigenic part of the Polisarka Formation occurs 60 m above the sedimentary succession containing S-MDF signals. Hence, our findings confirm unambiguously that the S-MIF/S-MDF transition preceded the Paleoproterozoic snowball Earth. Resolution of this temporal relationship constrains cause-and-effect drivers of Earth's oxygenation, specifically ruling out conceptual models in which global glaciation precedes or causes the evolution of oxygenic photosynthesis.