湖北峡东地区牛坪剖面埃迪卡拉系碳同位素组成及地质意义

Carbon isotope composition and geological significance of Ediacaran in Niuping section of Yangtze Gorges,Hubei

对湖北宜昌埃迪卡拉系牛坪剖面碳酸盐岩进行了高精度的碳、氧同位素分析,微量元素测定。碳同位素演化趋势研究表明,牛坪剖面陡山沱组与灯影组下部存在2次碳同位素负漂移和3次显著的碳同位素正漂移。负漂移分别位于陡山沱组底部(EN1)和陡山沱组中部(EN2),δ13C值分别降低到-3.6‰、-2‰。正漂移分别位于陡山沱组下部(EP1)、上部(EP2)以及陡山沱组和灯影组界线处(EP3),δ13C分别上升到6.7‰、7.1‰、8.2‰。牛坪剖面埃迪卡拉系δ13C的演化趋势可与黄陵背斜周缘埃迪卡拉系碳同位素演化趋势对比,表明至少区域上碳同位素化学地层学在埃迪卡拉系划分和对比中具有重要意义。

The authors analyzed the C and O isotopes and determined the trace elements from the carbonate rocks of Eidacaran in Niuping section of Yangtze Gorges, Hubei Province. The C isotope evolvement trend showed two negative and three positive excursions in Doushantuo Formation and Dengying Formation of the Niuping section. The negative δ^13C excursions located at the lowermost of Doushantuo Formaiton （EN1） with a nadir at -3.6%o, and the middle Doushantuo Formation （EN2） with a nadir at -2‰. The positive δ^13C excursions located at lower Doushantuo Formaiton （ EP1 ）, upper Doushantuo Formaiton （EP2） and the boundary of Doushantuo Formaiton and Dengying Formation （EP2） , while the δ^13C increared to 6.7‰, 7. 1‰ and 8.2‰, respectively. The results indicate that the carbon isotopic chemostratigraphy in Niuping section can be campared with Huangling anticline, which is useful for regional correlation of the Ediacaran system in South China.