摘要
本文对三峡地区秭归庙河陡山沱组第一段至第三段、宜昌棺材崖陡山沱组第三段上部至灯影组底部以及四溪灯影组石板滩段和白马沱段碳酸盐岩碳氧同位素组成特点的研究结果表明,三峡地区震旦系碳同位素组成与全球新元古代广布的后Marinoan冰期地层δ^(13)C的分布模式基本一致。本文还讨论了地层中碳同位素组成与生物演化和地层层序发展的关系,指出陡山沱组一段白云岩中δ^(13)C的负异常可以作为震旦系底界划分的标志,最晚Varanger冰期在三峡地区由陡山沱组三段上部出现的三级层序界面所替代,震旦系内部陡山沱组一段和三段可能形成于Marinoan冰期之后,伊迪卡拉生物分异发展之前,而陡山沱组四段及上覆灯影峡组则大致与国外伊迪卡拉期地层对比。
Systemic δ 13C and δ 18O analyses of the carbonate in the Sinian Doushantuo Formation at Miaohe of Zigui, the uppermost Doushantuo Formation and the lowermost Dengying Formation at Guancaiya and the Dengying Formation at Sixi in Yichang indicate that the carbon-isotopic compositions of the Sinian carbonate varies strati-graphically in a pattern comparable to the distribution of δ 13C values of the widespread Neoproterozoic post-Marinoan strata in the glacial period in the world. The paper also discusses the relationships between carbon-isotopic compositions, biological evolution and stratigraphical successions, and points out that the negative δ 13C anomalies found in the first member of the Doushantuo Formation can be the important standard for defining the basal boundary of the Sinian. The depositional age of the Doushantuo Formation is younger than the Marinoan glacial age and older than the diverse Ediacara, and the overlying Dengying Formation basically corresponds with the strata of the Ediacara Period.
出处
《地质论评》
CAS
CSCD
北大核心
2003年第1期66-73,共8页
Geological Review
基金
中国地质调查局地质调查项目"中国震旦纪及显生宙年代地层单位的划分及其时限研究"(编号J1.2.6)
国家自然科学基金(编号49872D16)
