【摘要】 西藏定结盆地叶如藏布东岸剖面为一套灰与灰白色黏土质砂、粉砂、细砂与粗砂层所组成的湖相沉积地层，厚约41.3 m, ESR和U系测年数据显示该地层沉积时间介于距今551.6～202.4 ka的中更新世时期。该套地层的孢粉化石丰富，依据孢粉化石类型与丰度变化，自下而上可分为5个孢粉带。结合测年结果、孢粉和介形类记录，定结盆地中更新世的古环境变化阶段为：551.6～448.4 ka,气候温暖湿润，适宜植物生长；448.4～375.2 ka,气候向冷干转化；375.2～291.2 ka,气候波动频繁，呈现冷湿—冷干—冷湿的变化过程；291.2～261.0 ka,气候进一步趋于干冷；261.0～202.4 ka,气候波动频繁，表现为冷干—暖湿—冷干的变化过程。更多还原

【Abstract】 Objective:In order to understand the climate and environment changes during the middle Pleistocene in the southern Xizang(Tibetan) Plateau, we studied the section located in eastern bank of Yeru River in the Dingjie Basin, southern Xizang(Tibetan) Plateau, which is lacustrine, deposited in middle Pleistocene, is consisted of a sequence of gray and white clay sand, silt, fine sand and coarse sand, with a thickness about 41. 3 m. Methods:The pollen samples are treated by hydrofluoric acid. The pollen are separated from the samples by conventional acid treatment and heavy liquid method. The age of lacustrine deposits determined by ESR and Useries dating. Results:The results show that the average pollen content of herbaceous plant, woody plant and ferns is 57. 6%, 38. 8% and 3. 5%, respectively. The vegetation types represented by pollen assemblages are grassland or forest grassland environment. According to the genus type and abundance of pollen fossils, the pollen fossils can be divided into five pollen zones from bottom to top. ESR and U-series dating data indicate that the deposition of the section is between 551. 6 and 202. 4 ka belong to the middle Pleistocene. Conclusion:The climate changes during the Middle Pleistocene in the dingjie basin are as follows: During the period of 551. 6 ～ 448. 4 ka, the climate was warm and humid, suitable for plant growth; during the period of 448. 4 ～ 375. 2 ka, the climate turned to cold and dry; during the period of 375. 2 ～ 291. 2 ka, the climate fluctuated frequently, showing a process from cold—humidity to cold—dry to cold—humidity;during the period of 291. 2 ～ 261. 0 ka, the climate turned to more dry and more cold; during the period of 261. 0 ～ 202. 4 ka, the climate fluctuated frequently, showing a process from cold—dry to warm—humidity to cold—dry.更多还原