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Figure 7. The Dalong Formation of the Upper Permian is typical of the deep-water trough facies. Its lithologies are dark siliceous shale and limestones with siliceous radiolarians and microforaminifers; ranges from 6.1 to 50 m in thickness. The characteristics of the Dalong Formation indicate that it is the condensed section of the maximum flooding surface in deep-water starved basin and an important source rock of the Upper Permian with an average TOC of 3.88% in the north Sichuan Basin.