Tectonic Deformation Features And Space-time Evolution In Northeastern Margin Of The Qinghai-Tibetan Plateau Since The Late Cenozoic Time

The study on the uplift and deformation process of the Qinghai-Tibetan Plateau is the base of reconstructing the dynamics of continental lithosphere and is also a key to discuss the interaction between the earth layers. The northeastern margin of the Qinghai-Tibetan Plateau is the front position of the whole Plateau expanding to the inner of the continent, as well as the newest and under forming part of the plateau. This area developed several large scale active tectonics which are very active during the late Quaternary. There also formed many Cenozoic depression basins where continuous and integrate late Cenozoic strata deposited. The sediments preserved in the basins not only record the detail deformation history of the whole plateau, but also contain the information of high-resolution environmental change, especially the climate change. So, the northeastern margin of the Qinghai-Tibetan Plateau is always thought to be the best region to study the plateau uplift, tectonic deformation, palaeo-climate change and interaction between them.This thesis takes the follow two aspects as the research masterstrokes: the geometrical image and kinematic characteristics of the main active tectonics, and the evolutions and tectonic deformations of the main Cenozoic basins in the northeastern margin of Qinghai-Tibetan Plateau. It summarizes the spatial and temporal evolution features and processes, the dynamic models and mechanisms of the tectonic deformation since Late Cenozoic.Then it penetrates into understanding and discussing the relationships between tectonic deformation of the northeastern margin area and the stages uplift process of the whole Plateau. The main conclusions are summarized bellow:The northeastern margin area of the Qaidam basin had experienced four periods of strong tectonic deformation since late Cenozoic. The age of the first stage is about 5.1Ma.B.P.. The second stage is between the end of Pliocene and the beginning of early Pleistocene, and its age is about 3.58Ma.B.P.. During the both periods formed clear angular unconformities. The third stage of tectonic deformation is also evidenced by an angular unconformity between the middle Pleistocene(Q2) and the early Pleistocene Qigequan Formation(Q1), and its age is about 0.73Ma. The forth stage of tectonic deformation happened before the late Pleistocene, which caused folds of the Q1-Q2 strata in this area. At the same time, there developed several active folds and fault zones which strike nearly the same and link each other in offset manner in the NNW orientation. There are three ranks of reverse-fold zones, i.e. the Huaitoutala, Eboshan and Xitieshan-Amunikeshan reverse-fold zones. The total crustal shortening of these reverse-fold zones is about 18.95km, and the average shortening rate is about 3.72mm/a since 5.1Ma. The total crustal shortening is about 8.8km, and the average shortening rate is about 2.46mm/a since 3.38Ma. The northern margin active fault zone of the Bayinguole river is a newly found Holocene active thrust fault zone in the northeastern margin area of the Qaidam basin. It is 60km long, andits vertical slip rate is about 0.28+0.18mm/a since late Pleistocene. The deformation of the northeastern margin area of the Qaidam basin had formed a group of thrust faults which extends from the mountain to the basin interior area where developed a series of thrust fault-anticline zones which are younger from the mountain to the basin. They belong to the composite frontal reverse nappe structure zones.The deformation of the Elashan area since late Cenozoic is characterized by right-lateral strike-slip motion and the Cenozoic basin deformation which is controlled by the main fault zone. The Elashan fault zone is an important boundary fault zone which separates the two great Cenozoic basins, the Qaidam basin and Gonghe basin. This fault is about 207km long and consists of right-step echelon arrangement of six discontinuous secondary faults. The step distance is about 1-3.5km. The age when the fault mechanical property changed from compressio...