青海贵德盆地3.75~1.77 Ma的构造与环境演化

Tectonic and environmental evolution during 3.75-1.77 Ma in the Guide Basin,Qinghai Province

青海贵德盆地阿密岗剖面高分辨率古地磁测年结果表明该剖面极性年代约为3.75~1.77 Ma.结合剖面沉积岩相组合和地层接触关系等特征,把贵德盆地3.75~1.77 Ma的构造环境演化过程大致分为3.75~2.58 Ma的强烈隆升期、2.58~2.48 Ma的相对稳定期,2.48~2.12 Ma的小幅度隆升期和2.12~1.77 Ma的又一次相对稳定期4个阶段.平均磁偏角研究显示贵德盆地2.58 Ma以来发生了一次明显的顺时针旋转变形作用,这与盆地沉积环境指示的高原在此阶段强烈隆升的结论相一致,二者都是3.6 Ma以来青藏运动的结果.

High-resolution paleomagnetic dating of the Amigang section in the Guide Basin,Qinghai Province showed that the polar age of the section was about 3.75-1.77 Ma.Combined with a study of the sedimentary facies and stratigraphic contact relationship,the evolution process of the tectonic environment in Guide Basin during 3.75-1.77 Ma was roughly divided into four stages:a strong uplift period of 3.75-2.58 Ma,a relative stable period of 2.58-2.48 Ma,a small amplitude uplift period of2.48-2.12 Ma and a relative stable period of 2.12-1.77 Ma.A clockwise rotation,revealed by average magnetic declination research,occurred since 2.58 Ma and was consistent with the conclusion that a strong uplift of the Tibetan Plateau happened at this stage,and both were the results of the QinghaiTibetan movement since 3.6 Ma.