Carbon and strontium isotopes and global correlation of Cambrian Series 2-Series 3 carbonate rocks in the Keping area of the northwestern Tarim Basin, NW China

摘要

One hundred and ten carbon and nineteen strontium isotopic values of outcropping Cambrian Series 2 and Series 3 carbonate rocks in the Penglaiba section of the Keping area were analyzed. Effective isotopic data with little influence of diagenesis were used to address the global correlation. The δ~(13)C values exhibit two major positive excursions (peaking at 3.1 and 3.3) and three major negative excursions (peaking at -3.0X, -4.2 and -3.2). The carbon isotope excursions (peaking at -3.0%,, and -4.2‰) across the Cambrian Series 2-Series 3 boundary show good correlations with similar variations reported in Siberia, Laurentia, North China and South China. In contrast, the other three carbon isotope excursions (peaking at 3.1, 3.3‰ and -3.2‰) do not have a fairly good global correlation because of the lack of biostratigraphic data. With respect to the ~(87)Sr/~(86)Sr ratios, they show good correlation with those reported for Laurentia, and further support the global δ~(13)C comparison. On the basis of these new data, it is showed that the combination of δ~(13)C curves and ~(87)Sr/~(86)Sr variations serves as a powerful tool for correlation and subdivision of Cambrian strata in the Tarim Basin of northwest China, and provides new data for global correlation.