Miocene tectonic lithofacies paleogeography of the Tibetan Plateau

Based on a systematic analysis of the types of 50 Miocene sedimentary basins as well as their tectonic settings and lithostratigraphic sequences in the Tibetan Plateau,the authors investigated the evolution of the Miocene tectonic lithofacies paleogeography in the Tibetan Plateau.During the Miocene,marine sedimentation of the Tibetan Plateau was quitted completely,and changed into terrestrial deposition completely.At ca.23Ma,the unconformities between the plateau and the surrounding areas were widespread,that marked the overall uplift of the plateau.The main bodies of Tarim,Qaidam,Xining-Lanzhou,Qiangtang,and Hoh Xil areas were characterized by large-area tectonic compressive lacustrine basin deposits.At ca.17.2Ma,the Altun Mountains were uplifted evidently and,as a result,there was no more reef limestone in Xichagou area of Qaidam Basin.In the west of the basin,there existed short deposition disconnection.From this time,the west part of Qaidam Basin began to show lacustrine regression,but the southeast of the basin began to show lacustrine transgression quickly.At ca 17.7Ma or so,the initial sag of the Suoerkuli intermontane basin was formed.Moreover,Wudaoliang-Tuotuohe basin of the plateau hinterland was uplifted due to the compression of southern Tanggula Range.At ca.16Ma,the deposition of the Wudaoliang Formation was finished,and Hoh Xil-Suolahu sag was formed again together with the generation of Suolahu Formation,producing large compressional lacustrine basins in the plateau hinterland.At about 1310Ma,the formation of NS-trending faulted basins in south Tibet,such as the formation of Jilong basin,Musitang basin and Pulan basin,was the mark that the plateau was uplifted to its peak and began to collapse.Since about 8 Ma,in the northeast of the plateau, almost all lacustrine basins entered into the stage of regression,and there was sandy conglomerate accumulation of alluvial fan,braided river and subaqueous fan.