Early and Middle Permian strata in the area south of Xungma-Comai in south-central Tibet and their significance

Fossils were collected from the strata assigned previously to the Mid-Late Jurassic Xungma Group in the area south of Xungma-Comai in south-central Tibet.Now the age of the strata has been determined to be Early-Mid Permian.The early Early Permian Laga Formation contains olistostromes and glacial boulders;clastic rocks in the late Early Permian Angji Formation contains large amounts of volcanic rocks;the Middle Permian Xiala Forma tion contains large amounts of fragments of volcanic rocks.In comparison with the Early-Mid Permian strata exposed widely in the Gangdise-Tengchong,there are ap-preciable differences in features of the lithologic association,sediment type,fossil concentration and generic and species components,as well as the geological setting.The determination of this sequence of strata has great significance for the study of the sedimentary facies of the Early-Mid Permian strata and reconstruc-tion of the paleogeographic environment in Tibet and the study of the stratigraphic evolution in the Tethyan tectonic development stage and tectonic setting of the basin in the Qinghai-Tibet Plateau and its adjacent areas.