青藏高原2.8Ma来的环境演化及其对构造事件响应

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

本文根据青藏高原中部错鄂湖深钻研究的最新成果 ,结合东部若尔盖盆地湖泊沉积物记录 ,探讨了青藏高原 2 8Ma以来的环境演化过程和高原构造隆升运动对环境演化的影响。初步研究显示 :大约 2 8MaBP错鄂湖构造成盆 ;2 6MaBP左右孢粉组合、粒度特征、岩性变化等均记录了一次强烈的构造隆升运动 ;2 6Ma～0 8Ma时段 ,高原可能处于一种整体隆升过程中的相对夷平阶段 ;若尔盖古湖揭示了 0 9MaBP来的 3次构造隆升运动 ,反映了高原环境演变的三个阶段 ;和黄土底界相当的错鄂湖沉积记录显示并未干旱的特征 ;黄土旺盛堆积时期 (L15、L9、L6)高原湖泊记录的气候特征为偏湿气候。

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 L 15、L 9、L 6.