Sedimentary facies of the Lower Permian Ngangze Formation in the Coqen Basin,Xizang

The sedimentary facies analysis is an important basic research in the petroleum exploration and assessment.The present paper presents a description of lithology,sedimentary fades,vertical evolution and regional deposition on the basis of the data obtained from the Lajiadang section in Gyungcang,Nyima,Xizang.The formation is dominated by a suite of dark clastic rock series consisting of sandstones and mudstones which are ascribed to the Carboniferous-Permian glacial marginal sea sediments on Gondwana land,and characteristic of both continental stable sediments and littoral low-energy sediments.The depositional environments are related to short-period small-scale nearshore glacial activity.