109 / 2025-03-31 22:05:28

Multi-stage mass extinction coincided with stepwise decrease of shallow-water oxygenation levels during the Cambrian Age 4

Cambrian Age 4; mass extinction; redox conditions; I/(Ca+Mg); cerium anamoly

Theme 3: Earth-Life Co-evolution Through Time > Session 3b: Evolution of the Earth-Life System During the Neoproterozoic-Paleozoic Transition

Following the Cambrian Explosion, the first major Phanerozoic extinction event occurred during Cambrian Stage 4, exhibiting extinction rates second only to the end-Permian mass extinction. To elucidate the marine redox conditions associated with this critical event, we conducted carbonate I/(Ca+Mg) ratio and Ce/Ce* anomaly analyses on two Cambrian Stage 4 shallow-water carbonate successions from eastern margin of the Yangtze Block. The results reveal persistently low I/(Ca+Mg) ratios (<0.5 μmol/mol) throughout the study interval, with two pronounced stepwise decreases coinciding with the primary extinction phases. These trends are further supported by synchronous Ce/Ce* anomalies, reinforcing the correlation between marine oxygen depletion and biotic turnover. Our findings provide robust evidence for a causal relationship between shallow-water deoxygenation and the Cambrian Stage 4 extinction, offering new insights into environmental-biological coevolution during the Ediacaran-Cambrian transition.