地球的晚期前坎布里亚绿化
L Paul Knauth1, Martin J Kennedy
1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA. Knauth@asu.edu
Nature
|July 10, 2009
概括
新新生代的碳同位素数据表明陆地植物,而不是独一无二的前剑桥碳循环扰乱,影响了海洋环境. 这一发现支持氧气水平的上升,为复杂生命铺平了道路.
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:
- 碳循环的动态通常使用海洋二碳酸盐中碳-13与碳-12 (13C/12C) 的比率来研究.
- 这种比率的变化记录在碳酸盐岩中,用于测定层次的日期,并了解甲基动物前的碳循环事件.
- 新新生代碳酸盐中13C/12C的低比率被解释为独一无二的前坎布里亚碳循环扰乱.
研究的目的:
- 重新评估新生代海洋碳酸盐中较低的 (13) C/(12) C值的解释.
- 调查这些同位素变化是否代表了独一无二的前剑桥碳循环事件或在年轻岩石中也见到的过程.
- 推断陆地光合作用社区对甲布纪前碳循环和大气的时间和影响.
主要方法:
- 编译和分析从新新生代海洋碳酸盐中公布的氧气和碳同位素数据.
- 对同位素系统的比较与已知碳酸盐二代生成的Phanerozoic实例.
- 评估已知可改变碳酸盐同位素组成的二代遗传过程.
主要成果:
- 新新生代碳酸盐的氧气和碳同位素系统学与经历了受陆地有机碳影响的二代生成的生代碳酸盐相似.
- 新生代碳酸盐中较低的 (13) C/(12) C值更能由陆地碳流入而不是独一无二的前坎布里亚碳循环中断来解释.
- 在大约8.5亿年前的碳酸盐中没有观察到显著的陆地碳流入.
结论:
- 据广泛报道,新生代碳酸盐中13C/12C的降低很可能是由于涉及陆地光合作用碳的二代生成,反映了Phanerozoic过程.
- 这种信号在8亿5千万年前之前没有出现,这表明光合作用社区的出现和扩散在晚期的前坎布里亚纪期间在陆地上.
- 这种陆地生物学增强的气候导致大规模的土壤形成,碳捕集,随后氧化,为多细胞生命的进化铺平了道路.
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