Sedimentary facies and litho-paleogeographic evolution of the Upper Triassic Xujiahe Formation in West Sichuan foreland basin

Based on the new stratigraphic division draft and large quantities of drilling,outcrop and core data,the authors have studied in detail sedimentary facies,paleogeographic characteristics and evolution of the Upper Triassic Xujiahe Formation in West Sichuan foreland basin.The conclusions show that Xujiahe Formation mainly deposited on alluvial fans,lacustrine deltas,lacustrine facies,marine deltas facies,shoreline facies and bay facies.According to studied in detail sedimentary facies and the characteristics of the tectonic evolution in the Xujiahe period,the authors think that the paleogeography evolved from marine environment,paralic environment to continental environment in the studied zone.Furthermore,with Anxian Movement influencing,Longmenshan uplifted and became a mountain which made the studied zone isolated with Ganzi sea and became a forland basin.