Abstract: Glacio-marine diamictite, discovered in Youxi and Xieba west of the Lancang River, Gyitang Town, Zhag’yab County, is Gondwana facies sedimentary rocks found for the first time east of the Bangong Co-Nujiang suture, eastern Tibet. Its basic feature is the same as those of the glacio-marine diamictite of Gondwana facies in the southern Qinghai-Tibet Plateau. The Carboniferous-Permian strata and fossils east of the Lancang River, Gyitang Town, are of typical Yangtze facies. Yangtze. The distribution of glacio-marine diamictite broadly represents the space affected by the Talchir glacier in Gondwana and may be used for age correlation. These data might suggest that the east boundary of Gondwana during the Carboniferous-Permian in eastern Tibet is the north Langcang River fault zone.