Main Structural Styles and Deformation Mechanisms in the Northern Sichuan Basin, Southern China

Abstract

Abstract: The Triassic Jialingjiang Formation and Leikoupo Formation are characterized by thick salt layers. Three tectono‐stratigraphic sequences can be identified according to detachment layers of Lower‐Middle Triassic salt beds in the northern Sichuan Basin, i.e. the sub‐salt sequence composed of Sinian to the Lower Triassic Feixianguan Formation, the salt sequence of the Lower Triassic Jialingjiang Formation and Mid‐Triassic Leikoupou Formation, and the supra‐salt sequence composed of continental clastics of the Upper‐Triassic Xujiahe Formation, Jurassic and Cretaceous. A series of specific structural styles, such as intensively deformed belt of basement‐involved imbricated thrust belt, basement‐involved and salt‐detached superimposed deformed belt, buried salt‐related detached belt, duplex, piling triangle zone and pop‐up, developed in the northern Sichuan Basin. The relatively thin salt beds, associated with the structural deformation of the northern Sichuan Basin, might act as a large decollement layer. The deformation mechanisms in the northern Sichuan Basin included regional compression and shortening, plastic flow and detachment, tectonic upwelling and erosion, gravitational sliding and spreading. The source rocks in the northern Sichuan Basin are strata underlying the salt layer, such as the Cambrian, Silurian and Permian. The structural deformation related to the Triassic salt controlled the styles of traps for hydrocarbon. The formation and development of hydrocarbon traps in the northern Sichuan Basin might have a bearing upon the Lower‐Middle Triassic salt sequences which were favorable to the hydrocarbon accumulation and preservation. The salt layers in the Lower‐Middle Triassic formed the main cap rocks and are favorable for the accumulation and preservation of hydrocarbon.