The Sedimentary Records Of Tectonic Uplift Of The East Northern Qaidam Basin In The Cenozoic

The Qaidam basin is an important tectonic unit in the northeast Tibetan Plateau.It experienced complex tectonic evolution under the influence of plate collision in the Cenozoic.How did the collision influenced the original tectonic pattern of Qaidam basin? What evolution did the basin go through in the Cenozoic? The solution of these problems is of great significance to clarify the basin-range coupling history and the growth mechanism of the Tibetan Plateau.Aimed to clarify the uplift process of east northern Qaidam orogenic belt,we reconstructed the range uplift history based on the stratographic correlation,basin sediments,clastic data,heavy mineral data,and detrital zircon geochronology,discuss the basin-range coupling history and provide insights for understanding the mechanism of intracontinental deformation caused by the remote effects of continental collision.The Lulehe area in the northern Qaidam crop out the full Cenozoic strata and the Huaitoutala missed some strata.The sedimentary environments are alluvial fan,braided river and lake.The sedimentary systems changed several times in Huaitoutala and this may indicate the sources changes considering the paleocurrrent and gravel composition changes.The clastic components and heavy minerals show that the deposition is characterized with high content of feldspar and lithlic,low content of unstable heavy mineral,and low ZTR index.The Cenozoic sediments in east northern Qaidam are typical near source and rapidly deposited.Base on the clastic composition and heavy mineral assemblage,the relevant strata in the nearby orogenic belt can be traced.The sandstone ternary diagrams show that the source areas are mainly polycyclic orogenic belts and collision-fold orogenic belts.The detrital zircon U-Pb datas show that the ages are mainly concentrated in the Permian to Triassic,Ordovician to Silurian,Neoproterozoic and Paleoproterozoic.This indicated that the sediments are from the near mountain Zongwulong,Olongbuluke,and Aimunike.The two obvious changes of clastic composition and heavy minerals in top Lulehe Formation and top upper Ganchaigou Formation are recognized,indicates the uplift of mountain Saishiteng and mountain Turgendaban.Also the two obvious changes in lower Youshashan Formation(~11Ma and~8Ma)are recognized,indicates the uplift of mountain Aimunike and Zongwu,respectively.The clastic components and heavy mineral content fluctuated in the middle Shizigou Formation(~5.1Ma)and some dolomite appearanced,this may indicated the uplift of mountain Oulongbuluke.The basin-range pattern in the northeast Qaidam basin was formed in the late Miocene to Pliocene.The uplift of mountain Aimunike in the late Miocene separated the original Qaidam basin and the Delingha depression formed.The uplift of mountain Oulongbuluke in Piocene separated the northeast Qaidam basin into Delingha depression and Ounan depression.The present basin-range geomorphic pattern gradually formed.The Cenozoic uplift in the east northern Qaidamu margin can be divided into Paleocene-Eocene and Miocene-Pliocene.The first stage in Paleocene-Eocene is the uplift of mountain Saishiteng and Tuergendaban.This may be the long-range effection of the Indian-Asian plates collision.The second stage in Miocene-Pliocene is the sequential uplift of Moutain Zongwulong,Aimunike,and Oulongbuluke in Huaitoutala area.It is related to the crust shorten and thicken under the strong compressive stress in the NS direction,and controlled by the collision of the Eurasian plate and the Indian plate to the northeast of the plateau.Based on the studies above,the Cenozoic sedimentary evolution history of the east northern margin of Qaidam basin is clarified through the changes of sedimentary facies,clastic components,and heavy minerals.The uplift time of mountain Aimunike and Oulongbuluke was limited also the basin-range evolution process in east Qaidam was reconstructed,this provide insights for the Tibetan Plateau uplift effection on Qaidam basin.