New C isotope stratigraphy form southwest China: Implications for the placement of the Precambrian-Cambrian boundary on the Yangtze Platform and Global correlations

摘要

A high-resolution C isotope profile from a fossiliferous section spanning the Precambrian=Cambrian (PC-C) boundary on the Yangtze Platform, southwest China, is used to constrain C isotope chemostratigraphy and its global correlation. The discovery of a strong negative C isotopic anomaly just below the China marker A indicates that this negative anomaly can be correlated globally, and demonstrates that the PC-C boundary of the Chinese successions should be close to marker A. On the basis of C isotope chemostratigraphic constraints and biostratigraphic data, we find that C isotopic peak S2, also first reported here from the Chinese successions, can be correlated with C isotopic peak I in northern Siberia and C isotope feature D in southwest Mongolia. By integrating the data from archaeocyaeothan fauna, the C isotopic peak S3 in the middle Dahai carbonates may be correlative with feature G in the Mongolian section.