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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.
In the Phanerozoic, there are three major geological boundaries: Precambrian / Cambrian. Trim / Triassic and Cretaceous / Tertiary. Studies of these boundaries in China and over the world strongly suggestive 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. Therefore, the three above-mentioned mass extinction events may be deemed as key indicators for the division of the geological history of thehanethrozoic.