摘要
塔里木盆地柯坪地区蓬莱坝剖面是研究寒武系地层的典型剖面,而迄今未有第二统-第三统界线处碳同位素演化研究。本研究对该剖面第二统吾松格尔组-第三统沙依里克组过渡区碳酸盐岩进行系统取样,分析了18件样品的碳、氧同位素组成。结果表明,δ13C(V-PDB)和δ18O(V-PDB)值分别分布于-4.2‰～0.8‰之间和-7.4‰～-3.8‰之间,二者之间相关性不明显,并且δ13C值在第二统与第三统界线处呈现明显的负漂移,可达-4.2‰。因此,δ13C值负漂移未受成岩作用影响,真实反映了原始海水碳同位素组成特征,可与北美、西伯利亚、华南以及华北地区的ROECE地质事件对比,具有全球意义。鉴于ROECE(Redlichiid-Olenellid Extinction Carbonisotope Excursion)事件约发生在509Ma,所以本研究为区域地层研究提供了一个较为可靠的绝对年龄数据,弥补了传统年代学研究方面的不足。此外,这是ROECE事件在塔里木盆地的首次报道,对寒武系地层划分以及全球对比具有重要科学意义。
Penglaiba section of the Kalpin area,Tarim Basin,serves as a typical section for Cambrian research,whereas no detailed carbon isotopic research on the Cambrian Series 2—Series 3 boundary has been documented up to date. Carbon isotope analyses were carried out on the carbonate rocks of Cambrian Series 2 （Wusongger Formation）—Series 3 （Shayilik Formation） transition in the Penglaiba section. The δ^13C values （V-PDB） vary between-4.2‰ and 0.8‰,while the δ^18O values （V-PDB） vary between-7.4‰ and-3.8‰. Moreover,there is no obvious correlation between the δ^13C and δ^18O values,indicating the δ^13C values recorded a memory of ancient seawater chemistry. A large negative δ^13C excursion up to-4.2‰ at the boundary between the Wusongger and Shayilik formations characterize the Cambrian Series 2—Series 3 boundary. This negative δ^13C excursion could be correlated with the ROECE events reported for Laurentia,Siberia,North China and South China. As ROECE happened at approximately 509 Ma,our report offers a reliable age for the Cambrian strata in the Tarim Basin. This work is also the first report of ROECE excursion in the Tarim Basin,and highlights the great potential of δ^13C variation in Cambrian subdivision and global correlation.
出处
《地质论评》
CAS
CSCD
北大核心
2011年第1期16-23,共8页
Geological Review
基金
国家科技重大专项(编号2008ZX05005-002-007HZ)的成果
