华南峡东地区埃迪卡拉（震旦）纪年代地层划分初探

华南峡东地区埃迪卡拉纪地层连续,出露完整,化石丰富,顶、底界线清楚,是世界上同时代地层最具代表性的序列之一,也是解决埃迪卡拉纪年代地层划分、竞争相关界线层型剖面的最理想地区之一。根据近年来峡东地区埃迪卡拉系的同位素年代学、生物地层学和化学地层学等方面的研究积累,本文以生物地层序列(生物演化阶段)为基础标志,以碳稳定同位素组成的重要变化界面为辅助标志,对峡东地区埃迪卡拉纪地层进行年代地层的划分,提出2统5阶方案。下统名称建议用峡东统,下分九龙湾阶和陈家园子阶;上统名称建议用扬子统,下分吊崖坡阶、第四阶和第五阶。在此基础上,根据生物地层和碳稳定同位素地层学的特征,初步探讨了与其他地区埃迪卡拉系的对比关系。这一划分和对比方案只是目前研究的阶段性认识,更完整的划分对比意见还有待今后的进一步完善。

A preliminary discussion of the chronostratigraphic subdivision of the Sinian (Ediacaran) in the Yangtze Gorges, South China

The Ediacaran stratum in the Yangtze Gorges area,South China is well-known as it represents the most complete and continuous succession with bundant micro-and macrofossils in China,and is considered as one of the most ideal areas for resolving problem of the chronostratigraphic subdivision and establishing the series and stage boundary-stratotypes of the Ediacaran.According to several accurate isotopic ages,great progresses of the chemostratigraphy and biostratigraphy in recent years,we suggest that the Ediacaran should be subdivided as two series and five stages based on biostratigraphic data and δ13C excursion.The lower series named as the Xiadongian which consists of two stages(separately as Jiulongwanian Stage and Chenjiayuanzian Stage),upper series named as Yangtzean which consists of three stages(separately as Diaoyapoan stage,Fourth Stage and Fifth Stage).According to the bio-stratigraphy and characteristics of stable carbon isotope stratigraphy,a preliminary correlation of the Ediacaran succession between the Yangtze Gorges and other typical areas has been discussed.However,the current Ediacaran chronostratigraphic subdivision is a preliminary scheme,which needs more work in the future.