摘要
为验证碳稳定同位素特征在不同沉积环境的变化,选择了斜坡相带张家界田坪埃迪卡拉系剖面进行碳同位素的研究,系统采集了110件碳酸盐岩样品,并在中国地质调查局同位素地球化学开放研究实验室通过MAT-251质谱仪完成了碳、氧稳定同位素测试。测试结果显示,张家界田坪埃迪卡拉系剖面所记录的碳稳定同位素曲线,除了陡山沱组底部的负异常外,和任何已知的这一时期的碳同位素曲线均有较大的差异。从陡山沱组二段中下部开始,δ13 C表现为长期稳定的正漂移。大致在4.0‰附近波动,变化幅度在2.0‰-6.0‰之间,这一趋势一直延续至灯影组二段的中部,随后δ13 C逐渐减小,并在灯影组三段中部降至负值。从田坪剖面所处的古地理位置等因素的综合考虑,该剖面陡山沱组碳同位素δ13C值既受控于氧化还原界面的迁移,同时,也叠加了碳酸盐岩风化作用的影响;而灯影组的碳同位素δ13C值则更多地受控于海平面的变化。
In order to understand the variation pattern of the stable carbon isotope composition in different sedimentary environments,we systematically collected 110bulk carbonate samples and studied the characteristics of the stable carbon isotope composition at the Tianping section in Zhangjiajie City,which is located in the Ediacaran slope facies zone.The samples were tested by the MAT-251mass spectrometer in the Open Laboratory for Isotope Geochemistry,China Geological Survey.The results show that except for the negative anomaly at the base of Doushantuo Formation,theδ13 C variation curve is remarkably different from all the other reported curves during this period.The results show that theδ13 C varies in the range from 2.0‰-6.0‰ with an average of 4.0‰from the lower-middle part of the MemberⅡof the Doushantuo Formation to the middle part of MemberⅡof the Dengying Formation.Then theδ13C decreases gradually to negative values in the middle part of MemberⅢof the Dengying Formation.Considering the paleogeography of the Tianping section,we propose that theδ13C value of the Doushantuo Formation in this section was controlled not only by fluctuation of the chemocline,but also by the weathering of carbonate;however,the value ofδ13Cof the Dengying Formation was more likely controlled by the fluctuations of sea level.
出处
《地质科技情报》
CAS
CSCD
北大核心
2014年第4期1-5,11,共6页
Geological Science and Technology Information
基金
中国地质调查局项目(1212010782005
1212011121104)
