峡东地区埃迪卡拉系陡山沱组碳同位素特征研究进展与国内外对比  

Research Advances and Correlations of Carbon Isotopic Compositions in the Ediacaran Doushantuo Formation,East Yangtze Gorges,South China

作　　者：陈寿铭[1] 尹崇玉[1] 刘鹏举[1] 高林志[1] 唐烽[1] 王自强[2] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质大学(北京),北京100083

出　　处：《地球学报》2009年第4期475-486,共12页Acta Geoscientica Sinica

基　　金：中国地质调查局项目(1212010611802-2);科技部基础工作专项(2006FY120300-2);中国地质科学院地质研究所中央级公益性基本业务费专项基金(J0714)资助

摘　　要：本文重点通过研究峡东地区埃迪卡拉系陡山沱组碳同位素的变化规律,来探讨其全球地层对比意义。峡东地区埃迪卡拉系陡山沱组经历了三次比较显著的碳同位素负漂移(EN1～EN3)和两次正漂移(EP1、EP2)。第一次碳同位素负漂移(EN1)发生在南沱冰期之后陡山沱组底部"盖帽碳酸盐岩"层位及其上部的白云岩,与世界其他地区Marinoan冰期之后"盖帽碳酸盐岩"的碳同位素负漂移可进行对比;第二次碳同位素负漂移(EN2)发生在陡山沱组中部;第三次负漂移(EN3)发生在陡山沱组顶部,是该地质历史时期持续时间最长的一期碳同位素负漂移,同澳大利亚、阿曼、纳米比亚、加里福尼亚、西伯利亚、苏格兰等地碳同位素异常均可进行对比。两次正漂移(EP1、EP2)分别位于第二段中部和第三段的下部,分别与陡山沱组所含的两个疑源类组合具有很好的对应关系;而EN3则与陡山沱组上部所含的宏体化石组合(庙河生物群)相对应;表明碳同位素的变化与生物演化具有一定的对应关系。研究表明,利用碳同位素变化特征进行埃迪卡拉纪地层洲际对比是行之有效的手段之一。Carbonates of the Doushantuo Formation in the East Yangtze Gorges have recorded three remarkable negative and two positive carbon isotope anomalies： 1） a negative δ^13C excursion （EN1）, whose values vary from -0.9%o to -41.166‰ in the Doushantuo cap carbonate （Member I）, is characterized by tepee-like structures, stro- matacties-like cavities, sheet cracks, cemented breccias and tube structures and can be correlated with the other carbon isotope excursion which appears in the Marinoan cap carbonates in the whole world; 2） a positive δ^13C excursion （EP1） in the lower-middle part of Member II of the Doushantuo Formation, whose values range from 0 to ＋6‰, includes the acritarchs assemblage characterized by Tianzhushania, multicellular algal and macroscopic alga; 3） a negative δ^13C excursion （EN2） in the uppermost part of Member II of the Doushantuo Formation, whose values range from 0 to -2.1‰, where Tianzhushania went into extinction; 4） a positive δ^13C excursion （EP2） occurs in lower Member III, which includes a different acritarchs assemblage characterized by the occurrence of some new taxa, e.g., Ceratosphaeridium and Tanarium. The Ediacaran acritarchs went into extinction at the end of EP2; 5） a negative δ^13C excursion （EN3） occurs from the uppermost part of Member III to Member IV with a nadir of-8.7‰, which is considered to be the largest carbon isotope trend in the geological record and can be correlated with the negative δ^13C excursion in Australia, Oman, Namibia, California, Siberian and Scotland. The Ediacaran body fossils appear in this gradation and, in addition, the macroscopic algae become abundant and diverse. Both the EN2 and EN3 are related to the oxidation events, which probably cause the eukaryote diversity in the Ediacaran oceans, so that they may serve as useful symbols for the correlation of the Ediacaran system worldwide.

关 键 词：埃迪卡拉系 陡山沱组 碳同位素 峡东地区 

分 类 号：P534.31[天文地球—古生物学与地层学] P597.2[天文地球—地质学]