The discovery and significance of the sporopollen assemblages from the Oliogene Rigongla Formation in the Lunggar region,Zhongba,Xizang

The sporopollen fossils were collected by the authors from the middle-upper part of the Oliogene Rigongla Formation during the 1:50 000 geological survey in the Lunggar region,Zhongba,Xizang. The collected sporopollen assemblages consist of the gymnospermous pollens including Abietineaepollenites sp.,Pinuspollenites sp.,Tsugaepollenites sp. and Piceapollis sp.; the angiospermous pollens including Artemesiaepollenites sp., Betulaceoipollenites sp.,Rutaceoipollenites sp.,Betulaepollenites sp. and Graminipidites sp.,and the spores of Pteridophytes including Deltoidospora sp.,Lycopodiumsporites sp. and Toroisporis sp. These assemblages belong to the Oliogene or even the Miocene in age. During these periods,the dominant Pinaceae and Artemisia represent a tectonic movement-associated palaeoenvironmental event. The discovery of the sporopollen assemblages in this region has provided helpful data for the stratigraphic division and correlation of the Rigongla Formation,and the analysis of palaeoclimatology, palaeogeography and palaeovegetation during the deposition of the Rigongla Formation,and also reflected the trajectory and characteristics, and the coupling relationship between the palaeoclimatic changes and the tectonic evolution and responses of sedimentary basins.