基于高密度地震反射和砂箱实验的准噶尔盆地南缘霍尔果斯背斜深层构造解析

利用霍尔果斯背斜高密度三维地震反射资料和砂箱模拟实验,并根据构造几何学的分析方法,获得准噶尔盆地南缘霍尔果斯背斜的深部地质结构及运动学演化过程。结果表明:霍尔果斯背斜高密度三维地震反射揭示安集海河组(E2-3a)滑脱层冲出地表、上盘形成单斜构造;下侏罗统滑脱层与安集海河组(E2-3a)滑脱层构成深部构造楔,构造楔缩短量为2306 m,平均缩短率为2 mm/a;下侏罗统深部下凹的地震反射特征揭示深层可能发育早期断陷。先存断陷和同构造沉积控制下的双层滑脱构造物理模拟实验结果与霍尔果斯背斜高密度三维地震反射形态相近,并且其运动学特征也一致。获得的霍尔果斯深层构造楔变形速率明显低于前人通过其他方式获得的相邻区域浅层变形速率,可能是由于北天山山前发育多套塑性滑脱层,并在挤压过程中塑性地层内部层间剪切作用造成的;另外,研究区下侏罗统及以下地层可能发育早期的断陷,并对晚期构造变形有一定的控制作用。
High-density seismic reflection data and sandbox physical modeling method were used to obtain the deep structure and evolution history of the Huoerguosi Anticline at the southern margin of Junggar Basin. E2-3a detachment fault thrusts northward and outcrops at the ground surface, and the hanging wall layers dip southward to form monoclonal structure. The lower Jurassic detachment is combined with the E2-3a detachment fault, forming a structural wedge in the deep with shorting up to 2306 m and at a rate of 2 mm/a. The layers below lower Jurassic may develop earlier fault depression. In the sandbox modeling which were controlled by the early fault depression and syn-tectonic sediment, the similar structure style as seen in the seismic profile was obtained, and the kinematic features are consistent between the sandbox modeling and the geological structure obtain from seismic reflection. The shorting rate calculated in this paper is much smaller than that from previous studies of shallow layers or at ground surface, which may result from the velocity difference between layers in multiple detachment layers in this area. The early fault depression structure may exert great influence on the subsequent structural evolution in the region