[B-PT23_30AM1] Decoding the history of Earth: From Hadean to Modern

[BPT23-07] Oceanic oxidation mechanisms spanning the Snowball Earth and early animal diversification

*Kunio KAIHO¹, Atena SHIZUYA¹, Masahiro OBA¹, Kenji YAMADA¹, Minori KIKUCHI¹, Naoto SENBA¹, Zhong-qiang CHEN², Jinnan TONG², Satoshi TAKAHASHI³, Li TIAN², Tsuyoshi KOMIYA³ (1.Tohoku University, 2.China University of Geosciences, 3.University of Tokyo)

Keywords:Ediacaran, Cryogenian, Neoproterozoic, oxygen, biomarkers

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.