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 stronglysuggest that they have the following similar features: mass extinctions of many taxa, positive anomalies ofplatinum-group metals, and abrupt changes of stable isotopes (δ~(13)C). It is quite probable that these were theconsequences of some rare catastrophic events of extraterrestrial origin. Hence, the three above-mentionedmass extinction events may be regarded as key indicators for the division of the geological history of thePhanerozoic.