Late Cenozoic Tectonic And Sedimentary Evolution Of The NE Pamir

Debates about the kinematics of the Pamir salient exist as the first-order structural and sedimentary features of the NE Pamir is rarely understood. Three end-member models are proposed and discussed in this dissertation:radial-thrusting model, dextral strike-slip model and tear fault model. We analysis different structural sytles responded to the three models, combining with the structural and sedimentary characteristics of the NE Pamir. Following conclusions can be made by the research of this dissertation:1. Field mapping combining with seismic interpretation contours the basic strcutrual frame of the region, which is dominated by transpressoinal stress and dextral strike-slip. Dextral Kashi-Ycheng Transfer System, Yangdaman Fault affect the formation of several en-echolon folds systems, such as Yingjisha Anticline, Qibei nose structure, etc. The Qimugen and Puxi area are featured by strike-slip-related half flower structure.2. Sedimentary works, including stratigraphic section description at Oytage and Tongyouluke Section, and comprisons among sedimentary columns throughout the region, establish the basic sedimentary characteristics of the NE Pamir. The Bashibulake Formation, Artux Formation and Xiyu Formation don’t change much along the strike of the orogen. However, the Anjuan Formation in the Wuqia Group, shows strong lithofacies variations. Along the Heshilafu-Aertashi belt, the Anjuan Formation is characterized by alluvial conglomarates. While in other region, the Anjuan Formation is featured by lacustrine mudstone. Heavy mineral analysis reconfirm this lithofacies variations. Along the Heshilafu Section and nearby regions, unstable heavy minerals appears in the Anjuan Formation. However, the unstable heavy minerals commonly appear after the deposition of the Artux Formation, which may indicate the intense northward-indention into the Tarim Basin since the Pleiocene. The variety and the contents of the havy minerals also indicate the along-strike changes of the provenance lithology, where the Pamir is dominated by igneous rocks, but the West Kunlun is mostly metamorphic rocks.3.The Wupoer Piggyback Basin lies close to the collision zone between the Pamir and the Tian Shan, thus archives the progressively process of the collision. Geomorphological, drainage system, seismic interpretation and isopach maps are analysised to understand the collision process. The depocenter loci are controlled by the relative motion of the Main Pamir Thrust, Pamir Frontal Thrust, and Wupoer Blind Thrust between them. Additionally, a west-to-east trend of deformation is proposed as the depocenter and balanced cross-section indicated the chonological order difference between the Alai Basin and the Wupoer Piggyback Basin.4. We consider three end-member types both exist in the evolution of the NE Pamir, but they developed in different stages:a) In the Oligocene, radial-thrusting exist both along the west and the east flank of the Pamir, clockwise rotation took place in the NE Pamir which is indicated by paleomagnetic datas. b) In the Miocene, cextral transfer faults KYTS accommodate the variant displacements of the NE Pamir salient, which is supportted by our structural and sedimentary analysis, c) From the Pleiocene to the present, deformation along the MPT and the KYTS is inactive and frontal structures indented northward into the Tarim Basin. Tear faults systems exist between fold-and-thrust belts to accommodate the different displaments of these zones. Swithes in the three models indicate tectonic activities or stress field changes in the Early Miocene and the Early Pleiocene. We interpret these changes are related to the onset and weaken of the KTYS, and the fully collision between the Pamir and Tian Shan.