使用碳酸结合同位素重建Phanerozoic气候,并对海水的氧同位素组成产生影响
Nivedita Thiagarajan1, Aivo Lepland2,3,4, Uri Ryb5
1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125.
概括
海洋沉积岩的氧同位素比率自古生物早期以来增加了8%. 新的聚合同位素分析揭示了较低的奥尔多维纪海水值,这表明气候记录需要重新评估二代和温度假设.
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:
- 在海洋沉积岩中,氧同位素比率长期显著增加 (δ18O).
- 解释这种趋势是复杂的碳酸盐形成温度的不确定性,海水氧同位素组成 (δ18O海水),和diagenetic改变.
- 碳酸盐凝聚同位素温度测量提供了一种强大的方法来限制这些因素,独立于水.
研究的目的:
- 将碳酸盐凝聚同位素测量应用于波罗的海盆地的奥尔多维纪碳酸盐记录.
- 开发一个框架来解释聚集的同位素数据和重建过去的海水O.O.
- 重新评估海洋18O及其驱动因素的长期趋势.
主要方法:
- 分析碳酸盐凝聚同位素组成 (Δ47) 在保存良好的奥尔多维纪碳酸盐中.
- 同位素分离的热力学原理应用于聚集的同位素.
- 用现有的代理方法比较聚合同位素衍生的温度和水成分.
主要成果:
- 重建的奥尔多维纪海水 δ18O值低于此前估计的值.
- 这项研究为解读古碳酸盐中聚集的同位素数据提供了一个新的框架.
- 证据表明,海水的长期增加 δ18O 导致了海洋沉积岩 δ18O 的观察到的增加.
结论:
- 这些发现需要重新评估依赖氧同位素的古气候重建,特别是关于海水组成和沉积/基因温度的假设.
- 全球水层中高温与低温水岩相互作用平衡的转变可能解释了海水长期增加的原因.
- 聚合同位素温度计是解决古海洋学和古气候档案中的模两可的强大工具.
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