New advances in the study of Carboniferous-Permian paleontology in Guoganjianianshan-Rongma area of Qiangtang region, Tibetan Plateau

A coral fossil Chatetes(Boswellia) heritschi Sokolov was discovered for the first time in the Zhanjin Group along the geological section between Dashahe and Guoganjianianshan in middle Qiangtang region. This discovery provides evidence of the Late Carboniferous biological age for the Zhanjin Group. However, this fossil is from the Tethyan type biota in a warm water environment and does not belong to the Gondwana cold water biota. Plenty of Middle Permian fusulinid fossils were also discovered for the first time in the Heishishan geological section, which belongs to both Gondwana cold-water biota, as represented by Wannerophyllam and Monodiexodina, and the warm-water Tethyan type biota, as evidenced by Chusenella tieni Chen, Schwagerina sanerduoensis Nieet Song and Pseudofusulina pseudosuni Sheng. The fossils are characterized by a mixed biota type of Gondwana and Tethyan types. It is suggested that the middle Qiangtang tectonic zone of Karakorum-Longmucuo-Shuanghu is biologically a mixed zone of Gondwana and Tethys biota in Carboniferous and Permian period, and there exists no obvious boundary of the biological region. It is thus inferred that the ocean basin represented by the Longmucuo-Shuanghu ophiolitic zone was a small marginal basin in southern Tethyan archipelago.