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

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 delta C-13 values exhibit two major positive excursions (peaking at 3.1 parts per thousand and 3.3 parts per thousand) and three major negative excursions (peaking at -3.0 parts per thousand, -4.2 parts per thousand and -3.2 parts per thousand). The carbon isotope excursions (peaking at -3.0 parts per thousand and -4.2 parts per thousand) 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 parts per thousand, 3.3 parts per thousand and -3.2 parts per thousand) do not have a fairly good global correlation because of the lack of biostratigraphic data. With respect to the Sr-87/Sr-86 ratios, they show good correlation with those reported for Laurentia, and further support the global delta C-13 comparison. On the basis of these new data, it is showed that the combination of delta C-13 curves and Sr-87/Sr-86 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. (C) 2011 Elsevier Ltd. All rights reserved.