ENVIRONMENTAL CHANGES AND ITS RESPONDING TO TECTONIC UPLIFT OF TIBETAN PLATEAU DURING THE LAST 2.8 Ma RECORDED BY LAKE SEDIMENTS

According to the studies of lake sediments' lithological property, grain size, pollen and magnetic susceptibility of the Cuoe lake in the central Tibetan Plateau, and combining the achievement of RH-core of Zoige basin in eastern Tibetan Plateau, we discuss the process of environmental changes and its responding to the tectonic uplift of Tibetan Plateau during the last 2.8Ma. The sedimentary records from the outcrop indicate that the Cuoe Basin was first formed by fault activity at about 2.8MaBP and a strong uplift movement occurred at about 2.6MaBP and a relatively leveling epoch under the background of the uplift from 2.6 to 0.8MaBP. Three tectonic uplift movements have been revealed by the sedimentary records in core of Zoige basin since 0.9MaBP,showing three stages of environmental evolution of the plateau. There was no strong dry climate event near 2.6MaBP, corresponding to the bottom age of Loess in the Loess Plateau. The sedimentary records of lake sediments in the plateau show a wet climate during the prosperous periods of loess accumulation such as L₁₅、L₉、L₆.