The carbon and oxygen isotopic compositions and their evolution of the Xixiangchi Group carbonate rocks in Sichuan Basin and their geological implications

Carbon and oxygen isotope analysis of Xixiangchi Group shows that the bottom boundary of the Upper Cambrian is defined for the first time. The Xixiangchi Group formed in a high salinity on shore marine sedimentary environment with a warm to dry climate and underwent a slow regression after a rapid transgression in the early and middle stages, In the late stage it entered a rapid regression after a slow transgression.