[B-PT23_30AM1] 地球史解読：冥王代から現代まで

[BPT23-07] 全球凍結と初期動物多様化時における海洋酸化メカニズム

*海保 邦夫¹、静谷 あてな¹、大庭 雅寛¹、山田 憲司¹、菊池 みのり¹、千馬 直登¹、チェン ツォンチャン²、トン ジンナン²、高橋 聡³、ティアン リー²、小宮 剛³ (1.東北大学大学院理学研究科地学専攻、2.中国地質大学、3.東京大学)

キーワード：エディアカラ紀, クリオジェ二アン紀, 新原生代, 酸素, バイオマーカー

The late Neoproterozoic (780 million years ago (Ma)) to early Cambrian (520 Ma) interval witnessed the rise and evolution of early animals. Oceanic oxidation is believed to be crucial in driving the early animal evolution. However, the oxygenation mechanism in seas during this critical period remains unknown. Here we found (i) oceanic anoxia before and during the Marinoan global glaciation (MGG) (660-635 Ma), (ii) surface-water reoxidation immediately after the MGG (635 Ma), (iii) intermediate-water oxidation in the mid-Ediacaran (600 Ma), (iv) deep-water oxidation in late Ediacaran (580 Ma), (v) oceanic anoxia at the end of the Ediacaran (541 Ma), and (vi) reoxidation in the early Cambrian (535 Ma). Thus, a stepwise marine oxygenation took place from shallow to deep water through the Ediacaran epoch, and every major changes in oxygen levels coincided with an important revolutions of marine life, suggesting a coevolution of ocean chemistry and early animals occurred during this period.