Discovery of SPICE and carbon isotope stratigraphic correlation of the Cambrian Furongian Series in Tarim Craton, NW China

• Published in: Science China. Earth sciences 2020-09, Vol.63 (9), p.1330-1338
• Main Authors: Chen, Yongquan, Zhang, Yanqiu, Wu, Yasheng, Zhou, Peng, Li, Kaikai, Wang, Xiaoxue
• Format: Article
• Language: English
• Subjects: Boreholes; Cambrian; Carbon; Carbon isotopes; Correlation; Cratons; Drilling; Earth and Environmental Science; Earth Sciences; Fossils; Isotopes; Limestone; Natural gas exploration; Oil and gas exploration; Oil exploration; Ordovician; Research Paper; Sedimentary facies; Stratigraphic correlation; Stratigraphy
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/s11430-019-9623-2

The Furongian Series of the Cambrian in the Tarim Craton (NW China) is mainly composed of crystalline dolostones, and is an important target for oil and gas exploration. The chronostratigraphic framework of the Furongian Series in the Tarim Craton has not yet been established due to the scarcity of fossils and the absence of the Steptoean Positive Carbon Isotope Excursion (SPICE), which is the primary global carbon isotope excursion of the Furongian Series. In this study, the SPICE was discovered by examining the carbon isotopes of the representative drilling wells in the West Platform and East Basin. A positive carbon isotope anomaly with δ 13 C values ranging from 1.5‰ to 1.9‰ (PDB), were found in the middle of the Xiaqiulitag Formation of the three drilling wells in the West Platform, and a positive excursion with δ 13 C values up to 4.0‰ (PDB), which is correlated with the SPICE, was found in the lower limestone of the Tuershaketag Formation in the East Basin. Based on the carbon isotopic data and chemostratigraphic correlation, the chronostratigraphic framework of the Furongian Series across different facies in the Tarim Craton is preliminarily established. The basal boundary of the Furongian Series was preliminarily defined by the occurrence of the SPICE. A weak positive anomaly of δ 13 C was observed at the base of the Penglaiba Formation of the three boreholes in the West Platform and the top of the Tuershaketag Formation of Tadong-2 well. We propose that the positive anomaly of the carbon isotope above the weak negative anomaly at the base of the Penglaiba Formation and the top of the Tuershaketag Formation can be used to define the Cambrian-Ordovician boundary in the Tarim Craton.