Analysis on sedimentary facies of Changxing Formation reefs profile of Panlongdong in Xuanhan, Northeastern Sichuan Basin

Based on the background information about the regional tectonics, stratigraphic profiles, paleogeographic, detailed description about reefs stratigraphic profile was made on the Upper Permian Changxing Formation. Meanwhile, combining with the rock slice appraisal analysis under the microscope indoor, main rock types were identified, such as limestone reef, dolomite reef, bioclastic limestone, granular limestone and dolomite. According to the outcrop observation, indoor rock slice identification analysis and the study of sedimentary facies marks through the perspective of petrology and paleontology, three types of sedimentary facies develop, there are open platform, platform margin reefs and platform edge shallow facies. In which, platform margin reefs is the mast developed facies, and we could further identify the reef base, reef core and fore-reef subfacies. Reef core mainly consists of framework reef and barrier reef, and platform edge shoals facies could be further divided to grain beach and oolitic beach subfacies. Sedimentary facies pattern of this profile are summarized preliminarily, and finally the sedimentary evolution sequence and their identification marks are discussed.