Carbonate sediment is widely developed above Lower Permain Angjie Formation in Coqin basin,which was disintegrated by previous research to establish several formations. Five conodont zones of Lower Permian-Lower Triassic were identified in the carbonate rocks through conodont studies, namely Mesogondolella siciliensis -Sweetognathodus subsymmetricu zone, Mesogondolella idahoensis zone, Jingondolella aserrata zone, Clarkina meishanensis zone, Neospathodus dieneri zone, and the stratigraphic age of the Xiala Formation was constrained at Lower Permian Kungurian-the later of Middle Permian.