摘要
SINCE Alvarez first used iridium anomaly to explain the Cretaceous-Tertiary impact eventand mass extinction, more than 70 sites of iridium-nickel anomalies have been found. The Per-mian-Triassic boundary extinction is more prominent than that of the Cretaceous-Tertiary.This leads us to make research on whether similar events happened during that period.
基金
This work was supported by the National Natural Science Foundation of China (Grant No. 49572084).
