二分抑或三分——关于二叠纪地质年表

TWO-FOLD OR THREE-FOLD?——CONCERNING GEOLOGICAL TIME SCALE OF PERMIAN PERIOD

一、前言自从六十年代以来,由于齿菊石类化石在华南、苏联及伊朗各自的卓勒法地区、伊朗的阿巴德地区、日本北上山地、苏联远东地区及墨西哥考会拉地区的不断发现,致使在二叠系上部分出一个以含齿菊石类为特征的上统的意见日趋强烈。迄今,世界上尚未发现一条完整的。

Divergent ecological differentiation is common in Permian ammonoids, but little attention has been paid to it by previous workers.Comparison of ammonoid faunal sequences between two ecological patterns of Permian ammonoids shows extensive overlap in the upper part of the current geological time scale, which was based mainly on generic-level ammonoid 'zones'. The Dzhulfian Stage (equivalent in the restricted sense to the Araksian of Furnish, 1973) in Transcaucasia and the Changhsingian Stage in South China represent the overlap of at least part of the Capitanian of North America and the Chhidruan of the Salt Range, respectively.With deletion of everlapping intervals, there is no justification for recognition of an 'Upper Series' comprising Dzhulfian and Changhsingian. The Permian geological time scale should include seven stages, in ascending order: Asselian, Sakmarian, Artinskian, Roadian, Wordian, Capita-nian, and Chhidruan or Changhsingian.The boundary between the Lower and Upper Series should be drawn at the bottom of the Wordian Stage, as before, corresponding to the extinction of the Perrinitidae.