Uplift Of The North Of Qinghai-Tibet Plateau And Record In Basins And Geomorphy

Qinghai-Tibet Plateau with 5000m in average altitude has the distinct south boundary-Himalaya Mountain. However, there are different characters from east to west in the north of the Plateau. Divided by Altyn Fault, Tarim Basin is separated from the Qinghai-Tibet Plateau by West Kunlun Mountain to the west, and a series of basin-ridge geomophical systems exist to the east, which cross over six latitude zone and respectively are Hoh Xil Basin, Kunlun Mountains, Kumkool and Qaidam Basin, Qilian Mountains and Jiuquan Basin (Hexi Corridor Basin) from south to north. This unique basin-ridge geomophy in the north-east of the Qinghai-Tibet Plateau is the result of tectonic action during forming of the Qinghai-Tibet Plateau.There are different tectonic character of Jiuquan Basin in Cenozoic and Mesozoic: it was a foreland basin in Cenozoic and was a downfaulted basin in Mesozoic. So it is a superimposed basin and there are two tectonic units from Mesozoic to Cenozoic. The evolution of Jiuquan Basin in Cenozoic can be divided into the following four stages: l)subsiding and depressing stage in Paleocene (~37.7Ma). Boundary of the basin of this stage was not controlled by fault and movement of the basin was mainly vertical subsiding; 2) strike-slip and pull-apart stage in Oligocene (37.7-30.3Ma). The basin was controlled by the Alytn sinistral strike-slip Fault; 3) foreland stage from Oligocene to middle Pleistocene (29.5-0.13Ma). The basin was controlled by piedmont fault of Qilan Mountain; 4) intramontane basin stage from latter Pleistocene to present (0.13Ma~). Uplift of Kuantai Mountain and Heshan Mountain lead to the basin surrounded by mountains.Based on the research of tectonics-strata relationship, contrast and analysis of seismic data, infilling history and relationship between basins and mountains, we can find that Qaidam Basin had an important change of tectonic background between Mesozoic and Cenozoic. In Cenozoic, Qaidam Basin experienced three stages of tectonic and sedimentary evolution: 1) stretched basin stage (65-46 Ma). In this stage, east-westward stretch structure was the essential control-basin structure; 2) foreland basin stage (46-2.45Ma). Approximate south-northward extruding and orogenic zone thrusting was the main control-basin tectonic background. The tectonic evolution sequence was: Kunlun Mountain thrusted northward from 46 to 30Ma; Kunlun Mountain and Qilian Mountain thrusted against Qaidam Bsain after 30Ma; 3) piedmont basin stage (2.45-0Ma). Near the Altyn fault, the west part of basin folded and lift up, and sedimentary centre removes to the east of the basin. Thrusting of piedmont fault of Kunlun Mountain and Qilian Mountain decreased or stopped.Mesozoic strata in Hoh Xil basin only have Triassic sediments, which are mainly about flysch sediments, but are lack of Jurassic-Cretaceous sediments. Hoh Xil basin experienced three stages of tectonics-sediment evolution in Cenozoic: 1) strike-slip and pull-apart basin stage (56-53Ma). The basin was in the Jinsha River suture zone, and Jinsha River suture zone expericed a sinistral strike-slipmovement; 2) foreland basin stage (53-30.0Ma), The basin had a character of northward phasic extension. The south of Jinsha River suture zone firstly folded and thrust northward, then thrust faults propelled northward progressivly. north of Fenghuoshan depression (53-38.2Ma), Wudaoliang depression (38.2-31.0Ma), Zhuonaihu depression (31.0- 30.0 Ma). Hoh Xil basin experienced about 7Ma (30-23Ma) sedimentary discontinuity; 4) post-foreland basin stage (23Ma-). Northward thrust of basin ended up, and carbonate rock deposited broadly on the planation surface. Since 20Ma, intense volcanicity took place in the west of Hoh Xil Basin-Bayan Har plate and depressing occurred in the east, which led to depositing of clastic rock of Quguo Formation.Cenozoic sedimentary basins in the north of the Qinghai-Tibet Plateau have similar evolution process, and foreland basins formed on the north-south extrusing background are very important in the evolution history of enti...