Evolution of Tectonic Lithofacies Paleogeography of Cenozoic of Qinghai-Tibet Plateau and Its Response to Uplift of the Plateau

By doing an integrated research on the types of 98 remnant basins,tectonic setting and lithostratigraphic sequence,we studied the evolution of tectonic lithofacies paleogeography of the Paleocene—Eocene,Oligocene,Miocene and Pliocene of Qinghai-Tibet plateau,dividing it into four stages:(1) The Paleocene to Eocene characterized by an uplift and erosional area in Songpan-Garze and Gangdise,depressed basins (lakes and pluvial plain) in eastern Tarim,Qaidam,Qiangtang and Hoh Xil,and Neo-Tethys sea in western and southern Qinghai-Tibet plateau;(2) The Oligocene characterized by an uplift area in Gangdise-Himalaya and Karakorum (marked by the absence of the sediments),rivers (originated from east and flew to west) in Yarlung Zangbo Jiang (marked by the deposition of Dazhuka conglomerate),an uplift and erosional area in western Kunlun and Songpan-Garze,and depressed basins (lakes) in Tarim,Qaidam,Qiangtang and Hoh Xil.Besides,it is also featured with a depressed littoral and neritic basin in southwestern Tarim and the termination of marine-facies deposition at the end of the Oligocene;(3) The Miocene characterized with the widespread of regional unconformity in the plateau,the overall uplift of the plateau in its adjacent area ca.23 Ma,depressed basins (lakes) in Tarim,Qaidam,Xining-Nanzhou,Qiangtang,Hoh Xil,lacustrine-facies deposition expanding to its peak in the plateau and its adjacent area ca.18-13 Ma,and the formation of south-north fault basins in southern Tibet ca.13-10 Ma,all indicating that the plateau uplifted to its peak and began to collapse;(4) The Pliocene characterized by an uplift and erosional area in most part of the plateau except in Hoh Xil-Qiangtang,Tarim and Qaidam.The continuing uplift and intensive fault in plateau elevated and divided the original large basin into small basins.The lacustrine-facies deposition prominently shrank and boulderstones accumulated,indicating a response to the overall uplift of the plateau.The plateau,which was higher in east and lower in west in physiognomy in the Paleogene,experienced a process of uneven uplift and sag in the Neogene and finally became higher in west and lower in east in physiognomy.This process indicates that a great physiognomy-reverse event happened in the Qinghai-Tibet plateau.