Characteristics And Evolution Of Tectonic Deformation In Esima,Qiangtang Basin

Qiangtang Basin is located in the central part of the Tibet Plateau between the Hoh Xil-Jinsha River tectonic belt and Bangong-Nu River tectonic belt.The Qiangtang Basin had experienced multiple episodes such as the closure of the Paleo-Tethys Ocean,the collision between the Lhasa and Qiangtang Blocks and the collision between the India and Eurasia continents,which shaped the Qiangtang Basin with complicated structures.This thesis managed with the field structures,2-D seismic profiles and balanced cross-section restoration,and analysised the basin framework and structural characteristics.The research aimed at the whole tectonic framework of South Qiangtang Basin and different tectonic events,and constrained their lationship between the basin deformation and thee volution of the plateau.With the surface structures and the deep seismic characteristics,the South Qiangtang Basin was subdivided into several tectonic units.The structures of Esima region are generally thin-skinned structure,and the top interface of the base was performed as a detachment fault.In the seismic profile,the reflections of the basement are shown.In the South Qiangtang terrane,the basement developed obvious two layers texture and the structures are complex in south Qiangtang.However,due to the relatively poor quality of seismic profiles,the determination of deep structures in the basin remains to be further improved.The balanced cross-section was performed with the shortening in the South Qiangtang Basin.In the South Qiangtang Basin,the shortening of the Jurassic is65-70% and Cretaceous is 50-60%.In addition,there are two major tectonic events in the South Qiangtang Basin.The first event corresponded to Lhasa-Qiangtang collision with ~100 km upper crust shortening,while the second event was controlled by the India-Eurasia collision with ~150 km upper crust shortening.The two phases can be related with the formation of the proto-Tibet plateau,and the Lhasa-Qiangtang and India-Eurasiacollisionboth played the key role for the uplift of plateau.