Deri′angma-Xiala section in the Xainza area, Tibet, China:A bridge for the stratigraphic and paleontological correlation between Gondwana and Tethys during the Late Carboniferous and Early Permian

The fossiliferous Middle Carboniferous and Permian are well developed in the Deri′angma-Xiala section in the Yunzhug area, Xainza County, northern Tibet. The strata between the carbonate rocks of the Chaguoluoma Formation (Devonian-Early Carboniferous) and carbonate rocks of the Xiala Formation (Middle Permian) consist mainly of clastic rocks with limestone, which are marked by glaciomarine deposits in terms of sedimentation and mixing of Gondwanan and Tethyan faunas in terms of fossils. The mixing of faunas establishes a bridge for the stratigraphic and paleontological correlation between the Carboniferous-Permian Gondwana and Tethys realms. Conodonts and brachiopods occur together in the middle and upper parts of the Yunzhug Formation. However, study of conodonts suggests that the middle and upper parts of the Yunzhug Formation are Late Carboniferous Moscovian in age, while study of brachiopods suggests an Early Permian Sakmarian age. This contradiction implies that the view that the upper part of the Upper Carboniferous is missing in regions of Gondwanic affinity including Tibet and western Yunnan should be reconsidered.