Evolution and Structural Styles of the Sichuan Foreland Basin

摘要

The Formation of the Sichuan foreland basin was the result of rifling and accretion in the border and interior of Yangtze block. The development of the foreland basin can be divided into two stages: (1) the early stage (O2-S), the formation of collision-type foreland basins; (2) the late stage (T3-K.z), the development of subduction-intracontinenl-type foreland basins, These different types of foreland basin were superimposed and formed a compos i te foreland basin. The collision-type foreland basin was formed by subduction and closure of oceanic crust, and accompanied with ophiolite, melange and arc. Flysch was deposited in the early and molasse deposited in the late, and composed of the two-layer filling structure. The intracontinental subduction-type foreland basin was not developed in the convergent plate boundary but in intraplatform, not accompanied with ophiolite, melange and are, and related with intraeontinenlal subduction. Molasse was deposited in the basin and formed one-layer filling structure. The main structural styles were controlled by the thrust and fold belts in the foreland basin. The structural deformation clearly showed the plane mid vertical zonation. The main structural styles were developed in the forekuid basin. They are thrust-nappe structure of basement, imbricated thrust system, nappe structure, duplex, pop up, triangular /one, detachment fold, fmill-bcnd fold and fault-propagation fold.