同位素表明,全球深海在坎布里亚时代没有接近现代氧化 3 甲动物辐射
Jean N R Clemente1,2, Haifeng Fan3,4, Chadlin M Ostrander5
1MIT-WHOI Joint Program in Oceanography, Woods Hole, Massachusetts, USA.
Geobiology
|August 6, 2025
概括
坎布里亚爆炸动物多样化并不是由广泛的深海氧化驱动的. 同位素数据表明,深海的氧气水平仍然很低,小幅增加可能仅限于大陆架.
科学领域:
- 地质化学 地质化学
- 古海洋学是古海洋学.
- 古生物学的古生物学
背景情况:
- 坎布里亚时代的爆炸,动物快速多样化的时期,通常与海洋氧化增加有关.
- 坎布里亚 redox 景观的重建是相互矛盾的,特别是关于深海氧气水平.
- 了解海洋氧化对于解释坎布里亚生物事件至关重要.
研究的目的:
- 为了重建坎布里亚时代第2-3阶段 (大约. 521-518 Ma) 的时间.
- 评估海洋氧化在坎布里亚时代爆炸期间元动物多样化中的作用.
- 研究 (Tl) 同位素组成作为深海氧化的代理物.
主要方法:
- 在中国南方 (青江和文安) 页岩序列中对authigenic (Tl) 同位素组成 (ε205Tiauth) 的分析.
- 样本的年代约定涵盖了坎布里亚期2-3阶段的边界和清江生物群的外观.
- 重新解释现有的 (Mo) 和 (U) 同位素数据.
主要成果:
- 观测到稳定的authigenic Tl同位素值 (ε205Tiauth) 约为-3至-4‰,与现代公海值 (-6‰) 不一致.
- 缺乏显著的Tl同位素转移表明没有短期的全球深海氧化事件.
- 当代的Mo和U同位素表明氧化量略有增加,可能仅限于大陆架.
结论:
- 全球深海在521-518万年前没有显著的氧化,这挑战了深海氧气和坎布里亚多样化之间的联系.
- 转向更好的氧气条件发生在555万年前到521万年前之间,但可能影响浅海环境.
- 多样化可能是由于浅层架设置中的氧化,而不是全球深海变化导致的.
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