Geomorphic Surfaces And Neo-tectonic Evolution Of The Arc Area In The Northeastern Margin Of The Qinghai-Xizang Plateau

The arc area on the northeastern side of the Qinghai-Tibet plateau is characterized by newest and intensive uplift and outward expanding of the plateau, with very active neo-tectonic movements and strong earthquakes in the mainland China. In the last 20 years, geologists have done a lot of studies in this area, concerning with active faults, palaeoearthquakes, tectonic deformation and process in Quaternary, the scales and rates of active fault displacement, and interaction of various tectonic blocks on the northeastern side of the Qinghai-Tibet plateau. However, many questions about the neo-tectonic deformation of this area remain open, such as the mode of deformation, the maximum amount of deformation, the specific processes of neo-tectonic evolution, because of different view angles and research methods.The strong neo-tectonic movement and special tectonic setting produced specific Yellow River and typical landscape of tectonic geomorphology in the area. This thesis is focused on the characteristics of the developed multi-step geomorphic surfaces and dating problem of geomorphic surfaces. Systematical field investigation and studies have been made on the pattern, structure, type, number of grade, formation age and distribution feature of the main geomorphic surfaces and the important tectonic events reflected by them in the area. Based on these work, the detailed processes of late- Cenozoic tectonic deformation and evolution of this area are discussed.1. Generation of the dating method of carbonate coats on stonesThe carbonate coats on stones developed in soil on the geomorphic surfaces of coarse clastic sediments in arid-semiarid regions contain evident information of age. The thickness of coats can be used as a good age indicator for the geomorphic surfaces. meanwhile the coats themselves can be directly used as dating materials in the ESR method. Through measuring the thickness of carbonate coats on stones in soils on the alluvial terraces in the mouth of the Heishanxia gorge of the Yd ESR dating of layers separated from the carbonate coats, the average of accumulation rates of the thickness of carbonate coats on stones since 1.57 Ma was calculated to be 0.10 mm/ka in the study area, and a regression equation between carbonate coat thickness and age was derived as follows:...