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有关地质历史时期中各大时代(如代与纪)的界线问题已经成为地质研究领域里的重大课题。地层与古生物学者采用多种手段(如化石分带、绝对年龄数值和磁性反向等)来确定系级界线的精确位置。自从国际地层委员会所属志留—泥盆纪界线工作组首先于1972年向第23届国际地质大会提交确定志留—泥盆纪分界的报告以来,其它多数系间的界线工作组亦在不同程度上大致如同他们的做法,来解决各自的界线问题。其方法是:先择
The issue of the boundary between geologists in various geologic historical periods (such as generation and discipline) has become a major issue in the field of geological research. Stratigraphy and palaeontologists use various means (such as fossil zoning, absolute age values, and magnetic reversals) to determine the precise location of the line-level boundaries. Since the Seismological-Devonian Boundary Line Working Group of the International Commission on Stratigraphy first submitted its report on identifying the Silurian-Devonian boundary to the 23rd International Geological Congress in 1972, the boundary working groups of other major departments also varied in varying degrees On the roughly the same as their approach to solve their own boundaries. The method is: first choice