四川盆地东北部前陆褶皱-冲断带盐相关构造

以中、下三叠统嘉陵江组(T1j)和雷口坡组(T2l)含膏盐碳酸盐岩层系为界,可以将川东北地区划分为3个构造-层序组合,盐下构造-层序组合由震旦系-下三叠统飞仙关组组成,属于一套海相碳酸盐岩层系为主的沉积;盐层构造-层序组合由下三叠统嘉陵江组和中三叠统雷口坡组组成,属于一套含厚层膏盐的海相碳酸盐岩层系;盐上构造-层序组合由上三叠统须家河组和侏罗系、白垩系组成,属于一套陆相碎屑岩沉积。川东北地区发育了一套独特的构造变形样式,主要有基底卷入叠瓦冲断强变形带、基底卷入与盐层滑脱叠合变形带、隐伏盐相关构造滑脱变形带、双重构造、堆垛式三角带构造和背冲断块构造等。由于该区盐岩层厚度相对较薄,盐岩层系总体作为一个大型滑脱层系,控制川东北地区的构造变形。川东北地区主要构造变形机制包括区域挤压缩短作用、盐岩层塑性流动和滑脱作用、构造隆升和剥蚀作用、重力滑动和重力扩展作用等。川东北地区与三叠系盐岩层系有关的构造变形控制该区油气圈闭样式,有利于油气聚集和保存。

Salt-Related Structures in the Foreland Fold-Thrust Belt of the Northeastern Sichuan Basin, South China

Three tectono-stratigraphic sequences can be divided in the northeaster Sichuan basin according to the Mid-and Lower-Triassic salty and gypsum beds.The sub-salt tectono-stratigraphic sequence,dominated by a marine-facies sedimentary carbonate sequence,is composed of the Sinian and Lower-Triassic Feixianguan Formation.Assemblage of the salt sequence and structure includes the Upper-Triassic Jialingjiang Formation and Mid-Triassic Leikoupou Formation and is characterized by saliniferous marine carbonate measures.The supra-salt sequence is composed of continental clastic rocks belonging to the Upper-Triassic Xujiahe Formation,Jurassic and Cretaceous.A series of specific structural styles,such as intense deformed belt of basement-revolved imbricated thrusts,superimposed deformed belt associated with the basement-revolved and salt detachment,buried salt-related detachment zone,duplex,triangle pile structure and pop-up,are developed in the northeastern Sichuan basin.Relatively thin salt beds in this area may act as a large-scale decollement zone which controls the structural deformation of northeastern Sichuan basin.The deformation mechanisms of northeastern Sichuan basin have a bearing upon the regional compression and shortening,plastic flow and detachment,tectonic upwelling and erosion,gravitational sliding and spreading.The tectonic deformation related to the Triassic in the northeastern Sichuan basin may control the pattern of oil/gas traps,which are favorable to the accumulation and reservation of hydrocarbon.