Neogene sporopollen assemblages and paleogeography in the Gyirong basin, Tibet

Abstract：The sporopollen assemblages discovered in the Woma Formation in the Gyirong basin, Tibet, provide evidence for continuous and stable uplift of the Qinghai-Tibet Plateau during the Pliocene. Six assemblage zones may be distinguished in the Woma Formation in the Gyirong basin. The paleovegetation of the Woma Formation is characterized by subtropical, mountainous, needleleaf and broadleaf forest with Pinus and Abies as the constructive species, reflecting a warm-moist paleoclimatic environment. During the period, there occurred several pronounced climatic cold-warm fluctuations. Analysis of the lithofacies and paleogeography of the Woma Formation indicates that the depositional environment of the Woma Formation was mainly the fluvial and lacustrine one and locally the alluvial fan and swampy one. The evolution of the paleogeographic environment of the Woma Formation progressed through three stages, namely, the early formation stage, semi-open lake basin stage and enclosed lake basin stage.