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氧和同位素证据表明,在342亿年前,气候温和
M T Hren1, M M Tice, C P Chamberlain
1Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, Connecticut 06511, USA. mhren@umich.edu
Nature
|November 13, 2009
概括
古代地图分析显示,地球早期的海洋比以前认为的要冷得多. 新的稳定同位素方法表明,古代海洋温度低于40°C,这挑战了早期的高温估计.
科学领域:
- 地质化学 地质化学
- 古气候学 古气候学
- 同位素地球化学 同位素地球化学
背景情况:
- 在前坎布里亚时代的桃中,稳定的氧同位素比率 (delta(18) O是了解早期地球气候的关键.
- 之前的研究表明,基于delta{18) O的基础上,高Archaean海洋温度 (5585°C),但由于原始海洋同位素组成的不确定性,这是有争议的.
- 结合delta(18) O和同位素 (deltaD) 分析提供了一种更可靠的方法来确定形成温度,而无需先前了解环境水同位素.
研究的目的:
- 通过结合的delta{18) O和deltaD分析方法,重新评估Archaean海洋温度.
- 为了限制3.42亿年前的巴克珊瑚礁的形成温度.
- 评估古老时代海洋与现代海洋相对的同位素组成.
主要方法:
- 对来自巴克礁图的样本中稳定的氧同位素比率 (delta(18) O) 和同位素比率 (deltaD) 的分析.
- 对沙丘形成环境的地球化学和沉积物分析.
- 同位素数据与现代水和水标准的比较.
主要成果:
- 巴克珊瑚礁的同位素分析表明,它是由不同低温的水形成的.
- 最多 (18) O 丰富的样本表明基因温度低于大约 40°C.
- 地化学和沉积物证据支持海洋形成条件,从浅到深的环境.
结论:
- 古考古时期的海洋比以往仅仅基于三角洲测量所估计的要冷得多 (<或=40°C).
- 古老时代的海洋相对于现代海洋而言,在同位素方面已经耗尽.
- 综合的delta(18) O和deltaD分析提供了可靠的古气温限制,而不需要先前了解海洋水的同位素组成.
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