对地质时代划分的意见及新地质年代表

<正> 1989年国际地层委员会通过了新的前塞武划分方案(Cowie 1989,孙大中1990,孙卫国1990),该方案将前塞武分为太古、元古两宙,而将元古宙又分为老、中、新三代(各以 2500、1600、1000M·Y·B·P·为底界)。元古宙各代共分出十个纪,各纪的名称采用当时地球上主要地质事件的希腊文词根来命名(如σιδηρ-铁,στενο-狭窄等)。

A new geological time scale and views on the division of geological time

The Precambria-n Geological Time Scale ptesenied by IUGS is discussed in this paper and a new geological time scale is being proposed (see Table 1).Because the non-contemporaneity of the events taking place in different parts of the earth, the periods named lor the events are meaningless.Considering lhat the duration of Proterozoic Eon is too long and does noi coincide with the tyeles of evolution nf ihe earth, the total geologic time is divided into five eons, i.e., the Katarchean, Ar-chean, Proterozoic, Eucaryotic and Phanerozoic.Each eon is 900 m.y.The Eucaryotic Eon beginning at 1700 m.y-R.P.is attrobited to the appearance oi t In cucaryotc cells.The durations nf eras are equal within individual eons, but they are as long as 400 m.y.in older eons (Katarchean and Archean), then 300 m.y.(Proterozoic and Eucaryotic) and finally as short as 200 m.y.in Phanerozoic The durations ol these eras are roughly coincided with the cycle time of the revolnlinn of the solar system around the Galaxy center.The period of revolution of the solar system changed from 400 m.y.about 3 billion years age to 200 m.y.at present.In consideration of the cycle, the Palaeozoic Era is divided into two periods (i.e..Early Palaeozoic Era and Late Palaeozoic Era), and the global Caledonian orogeny supports this division.The Mesozoic Era and Cafnozoic Era are merged into a Mesocainozoic Era.