在永久的大气氧化之前,有氧循环100 My
Benjamin T Uveges1,2, Gareth Izon1, Christopher K Junium3
1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 190029.
概括
大氧化事件 (GOE) 之前,有氧循环比以前认为的早1亿年. 这项研究揭示了对早期地球的新见解.
科学领域:
- 地质化学 地质化学
- 古气候学 古气候学
- 微生物进化 微生物进化
背景情况:
- 大氧化事件 (GOE) 标志着地球的氧化还原平衡发生了重大转变,影响了微生物进化和生物地球化学.
- 以前的理解将有氧海洋循环的过渡与GOE的最后阶段同步于大约233亿年前 (Ga).
- 印度政府的动态,振荡性和有限的研究范围,在永久氧化之前,对循环的演变产生了模两可.
研究的目的:
- 为了调查GOE的驱动因素和节奏,以及它对地球生物地质化学周期的影响.
- 通过使用稳定同位素地球化学来描述海洋循环在GOE之前的演变.
- 改进早期有氧条件的时间表及其对循环的影响.
主要方法:
- 分析稳定的碳 (δ13C) 和 (δ15N) 同位素的比率.
- 来自多个钻孔核心的约2.43亿年前的德意志和约2.33亿年前的Rooihoogte形成的采样.
- 同位素数据与古气候事件和氧化还原敏感元素循环的相关性.
主要成果:
- 在德意志形成中显著的负碳同位素外流 (68‰) 表明与雪球地球事件和2.43 Ga的早期氧气脉冲相关的大规模有机碳氧化.
- 在德意志形成中始终呈正值的δ15N值 (≤+20.3‰) 表明有氧循环.
- 全球 δ15N 记录中的时间转移表明有氧循环比以前确立的时间早大约 1 亿年.
结论:
- 这些发现将空气性海洋循环的时间表推迟到至少2.43亿年,比通常接受的GOE时间表更早.
- 这项研究为地球表面的早期和可能更复杂的氧化提供了关键证据.
- 这些结果完善了我们对大气氧化,古气候事件和主要生物地化学循环的演变之间的相互作用的理解.
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