Mass Extinction——A Fundamental Indicator for Major Natural Divisions of Geological History

Abstract In the Phanerozoic, there are three major geological boundaries: Precambrian / Cambrian, Permian / Triassic and Cretaceous / Tertiary. Studies of these boundaries in China and over the world strongly suggest that they have the following similar features: mass extinctions of many, taxa, positive anomalies of platinum‐group metals, and abrupt changes of stable isotopes (δ 13 C). It is quite probable that these were the consequences of some rare catastrophic events of extraterrestrial origin. Hence, the three above‐mentioned mass extinction events may be regarded as key indicators for the division of the geological history of the Phanerozoic.