Cenozoic environmental evolution of the Qaidam Basin and its implications for the uplift of the Tibetan Plateau and the drying of central Asia

A complete Cenozoic pollen sequence of the Qaidam Basin has been constructed with absolute age control. The Cenozoic environmental evolution of the Qaidam Basin, and its implications for the uplift of the Tibetan Plateau and the drying of central Asia during the Cenozoic Era is discussed, based on the interpretation of the pollen sequence, the commencement of eolian deposition in central China and the change of climatic distribution pattern of China. The results suggest that in the Qaidam Basin relatively dry climates prevailed in the Eocene-Oligocene and Pliocene-Pleistocene. These dry periods resulted from the effects of a Subtropical High Pressure Zone, and the uplift of the surrounding mountains and the Tibetan Plateau, respectively. About a 600 km northward drift of western China has probably occurred during the late Cenozoic, resulting in the Eocene-Oligocene Arid Climate Belt twisting about six degrees of latitude. The Tibetan Plateau reached probably 1500 m elevation by the latest Miocene (8-5 Ma), not as high as it was thought previously. The Cenozoic environmental evolution of northwest China does not support the idea that the retreat of the Paratethys Sea played an important role in the late Cenozoic drying of central Asia, at least not in northwest China. (C) 1999 Elsevier Science B.V. All rights reserved.