四川盆地西南部多期叠加变形构造解析:以自流井背斜为例

    Structural analysis of multi-stage superimposed deformation in the southwestern Sichuan Basin: An example from the Ziliujing anticline

    • 摘要: 四川盆地西南部地区由于受到周缘造山带构造隆升及变形扩展作用的影响,构造变形样式复杂,演化期次缺乏准确的时间约束。为了进一步探究该地区的构造演化过程,本次研究选取构造变形幅度相对较小的自流井背斜为研究对象,基于高品质地震反射资料,依据断层相关褶皱理论,精细解析其构造几何样式和运动学特征。研究结果表明,区内构造变形分层特征明显,深部以寒武系膏盐层为滑脱层,发育断层传播褶皱和滑脱褶皱,中部逆冲褶皱变形主要限制在志留系泥页岩顶界不整合面和下三叠统膏盐岩滑脱层之间,而浅部主要在上三叠统及以上地层发育宽缓褶皱和局部小位移断层。其中,深部寒武系滑脱层对区域构造样式控制起到关键作用。识别出的生长地层及构造平衡恢复结果揭示,自流井背斜带主要经历了加里东期、印支期,以及燕山期—喜马拉雅期3期主要挤压构造变形。而上三叠统中发育的北西向断裂指示后期在不同方向构造应力场下发生了叠加变形,可能是受到青藏高原东缘往东向四川盆地扩展作用的影响。

       

      Abstract: Due to the tectonic uplift and deformation propagation of adjacent orogens, complex structural styles have developed in the southwestern Sichuan Basin. However, there is still a lack of precise age constraints on their evolution history. Based on high−quality seismic reflection data, we conduct a structural analysis on the structural geometry and kinematic features of the low−amplitude Ziliujing anticline as an example using fault−related folding theory for exploring the history of structural evolution in the study area. The results demonstrate distinct stratified tectonic deformation. In the deep, fault− propagation folds and detachment folds develop above the Cambrian salt. Folds and thrusts in the intermediate are primarily confined between the top of the Silurian shales and soils and the lower Triassic salt layer. In the shallow, it is primarily characterized by gentle folds and minor faults. Significantly, the regional structural styles in this area are controlled by the deep Cambrian detachment. The identified growth strata, in conjunction with the results of balanced structural restorations, indicate that the study area has undergone three main stages of tectonic compression; late Caledonian, Indosinian, and Yanshanian and Himalayan epochs. Furthermore, the development of NW−directed faults in the upper Triassic strata implies a structural imposition likely resulting from the propagation of deformation due to eastward movement of the eastern margin of the Tibetan Plateau.

       

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