关于南华系底界年龄780Ma数值的讨论

COMMENT ON THE AGE 780 Ma AT THE LOWER BOUNDARY OF THE NANHUAN PERIOD

南华系(成冰系)底界年龄近年来受到国内外的广泛关注。2013版《中国地层表》(试用稿)上采用的是780Ma。本文根据国内外关于南华系(成冰系)底界年龄的最新研究成果和进展,同时结合780Ma数值的依据进一步做了一些分析和讨论并指出这个数据的问题和不足。南华系(成冰系)底界年龄应该是～720Ma。

The age at the lower boundary of the Nanhuan（Cryogenian）Period is a hot topic all over the world.Last year a＂Stratigraphic Chart in China（trial version）＂was issued,in which an age of 780 Ma is adopted for the lower boundary of the Nanhuan（Cryogenian）Period.This age value is obviously not acceptable either domestically or internationally.This paper briefly introduces recent achievement of the topic in China as well as abroad.Further,the basis of the age 780 Ma are discussed and finally they are shown that they were likely based on inherited zircons,therefore,recently the preferred age of the lower boundary of the Nanhuan（Cryogenian）Period is～720 Ma.