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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Astrochronology of the Ediacaran Shuram carbon isotope excursion, Oman
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Astrochronology of the Ediacaran Shuram carbon isotope excursion, Oman

机译：阿曼埃德拉兰·什氏碳同位素释放的航空学

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摘要

The Ediacaran is a highly dynamic period in terms of large perturbations in Earth's atmosphere, biosphere, and climate. Among these perturbations, a pronounced negative carbon isotope excursion, known as the Shuram excursion (SE), is characterized by the most depleted delta C-13 values (-12 parts per thousand) that have ever been observed in the geological record. A poorly determined chronostratigraphic framework makes the SE difficult to correlate and compare globally. Therefore, it is hard to study the potential connection between the SE and coeval climate and biological variations. Here, we present a high-resolution astrochronological study of the Ediacaran Shuram and Buah Formations, Nafun Group, Oman, in which the SE is reported for the first time. Power spectral analysis of the 600-m long gamma ray log of the Miqrat-1 Well shows that a hierarchy of astronomically-forced climate cycles (eccentricity, obliquity, and precession) is accurately-preserved. Using multiple statistical tests, we constructed a sedimentation rate variation profile that covers the entire SE, which is characterized by low rates in shale-dominated layers and high rates in shale-carbonate interbedded layers. The duration of the SE in Oman is suggested to be 7.7 +/- 0.2 Myr, which agrees with estimates from South Australia, South China, and the United States. An identical duration of the SE supports its global synchroneity and indicates a primary origin of the depleted delta C-13 values. Combined with the newly proposed termination age (562.5 +/- 1.1 Ma) of the SE, our astrochronological results suggest that the onset age of the excursion is 570.2 +/- 1.1 Ma. The astrochronology of the SE delineates the tempo of the excursion, with a rapid decrease (similar to 1 Myr) from the onset to its isotopic nadir followed by a more gradual recovery (similar to 6-7 Myr) towards the termination. The new chronostratigraphic framework permits further investigations of the potential causal links between the global carbon cycle and the widespread glaciation, the oceanic oxygenation, and the biological diversification in Ediacaran time. (C) 2020 Elsevier B.V. All rights reserved.
机译：EdiaCaran在地球大气层，生物圈和气候的大型扰动方面是一种高度动态的时期。在这些扰动中，称为Shuram偏移（SE）的明显的负碳同位素偏移，其特征在于在地质记录中观察到的最耗尽的ΔC-13值（-12份每千）。确定的计时框架不良，使SE难以与全球相关和比较。因此，难以研究SE和辅人气候与生物变异之间的潜在联系。在这里，我们提出了一项高分辨率的天球学研究，对埃德拉南岛和蟾蜍组织，Nafun集团，阿曼，首次报告了SE。 MIQRAT-1的600M长伽马射线日志的功率谱分析表明，准确地保留了天文迫使气候循环（偏心，倾斜和进气）的层次结构。使用多种统计测试，我们构建了一种沉积速率变化曲线，其覆盖整个SE，其特征在于页岩主导层的低速率和页岩碳酸盐互粘连的层。阿曼的SE的持续时间被建议为7.7 +/- 0.2 MYR，这与南澳大利亚，华南和美国的估计一致。 SE的相同持续时间支持其全局同步性，并指示耗尽的Delta C-13值的主要来源。结合新拟议的终止年龄（562.5 +/-1.1 mA），我们的天中学结果表明，偏移的发病年龄为570.2 +/- 1.1 mA。 SE的天中学描绘了偏移的节奏，从发病到其同位素Nadir的快速减少（类似于1 myr），然后更加逐渐恢复（类似于6-7 Myr）。新的计时器框架允许进一步调查全球碳循环和广泛冰川，海洋氧合和埃迪纳兰时间的潜在因果关系。 （c）2020 Elsevier B.v.保留所有权利。

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