Deformation Feature and Genesis Simulation of Fold-and-Thrust Belts in the Southern Margin,Junggar Basin

The fold-and-thrust belts is situated in the southern margin of the Junggar Basin and the northern part of Tianshan and Bogeda Mountains,which can be divided into two structure segmentation from the west to the east. The main factors controlling the fold-and-thrust belts are attributed to the different direction of compressed stresses and thickness of decollement beds. The four fold-and-thrust belts developed in the western segment from declinate compression stress included the basement-involved and the decollement structure styles. Deformation evolution was related to Jurassic coal beds and Cretaceous and Eogene clay beds. The thickness of ductile beds controlled the deformation intensity and transmission distance. The more thickness is,the more intensive deformation is. The basement-involved fold-and-thrust belts developed at the eastern segment in the southern margin of the Junggar Basin,lack of decollement structure,generated from stress coming from the Bogeda Mountain wedge thrusting vertically. Based on deformation characteristics and theory of similarity,several plain and profile sand-box experiments were devised to simulate deformation compressed from different directions. Simulation results illustrate that the vertical compression and the declinate compression with 15°angle between stress and boundary were responsible for the deformation differenciation between the western segment and the eastern segment. The evolution of four fold-and-thrust belts was simulated and reappeared by a double decollement model.