Sporopollen records in the Guge section of the Zanda basin, Tibet, and paleoenvironmental information reflected by it

Abstract：The palynological records of the Pliocene Guge section in the Zanda basin, Tibet, show that the Guge section registers the process of vegetational and environmental variation in the study area from 4.40 to 2.74 Ma. During 4.40-3.75 Ma the climate was cool and dry and there appeared the landscape of needleleaf and broadleaf veld vegetation; during 3.75-3.47 Ma the vegetation belonged to mountainous, warm-temperate, mixed needleleaf and broadleaf forest and the climate changed from cool-dry to warm-moist; during 3.47-3.20 Ma the vegetation grew well, belonging to the mixed needleleaf and broadleaf forest, and the climate was mainly wet-warm; during 3.20-2.96 Ma the vegetation was characterized by alternation of mountainous, warm-temperate, mixed needleleaf and broadleaf forest and cool-temperate needleleaf forest and the climate began to become dry-cold; during 2.96-2.74 Ma the vegetation was characterized by mountainous, cool-temperate, dark needleleaf forest and the climate kept dry and cold.