STRUCTURAL STYLES AND CHARACTERISTICS OF FOLD-THRUST BELTS IN SICHUAN FORELAND BASIN

The progressive thrusting and napping of Sichuan fold-thrust belts controlled the distribution and development of the main structural styles in the Sichuan foreland basin. In plane it can be divided into (1) ejective folded deformation belt in Chuandongnan area; (2) low and gentle anticlinal structural area in Chuanzhong uplift;and (3) low and steep-low and gentle folded belt of Chuanxibei and Chuandongbei. While it shows a zonality in plane, vertically the structural deformation appears in different levels, which can then be divided into (1) deepseated level; (2) middle-seated level; and (3) upper-seated level. On the whole, it is in a sandwich-like structure. The main structural types consist of basement thrust and nappe, imbricate thrust system, klippe, duplex,pop-up, triangle zone, fault-propagation fault-bend and gentle fold, etc.