喜马拉雅多期运动下库车坳陷构造变形响应特征

    Characteristics of structural deformation under Himalayan multi-periods movements in the Kuqa Depression

    • 摘要: 喜马拉雅期构造运动对中国西部地质地貌具有决定性影响,库车坳陷内的构造变形特征对其多期运动存在何种响应尚待解决。在库车坳陷克拉苏构造带地震剖面解译的基础上,采用离散元数值模拟、构造物理模拟等手段,探讨挤压背景下,喜马拉雅期构造活动造成的多期运动、垂向抬升、同构造沉积等因素对库车坳陷克拉苏构造带的构造变形响应特征与变形演化过程。克拉苏构造带对喜马拉雅多期运动的响应主要体现在,控制盐上层滑脱褶皱向前陆方向传播,挤压端褶皱隆升强度变弱;盐下层挤压端前展式叠瓦状逆冲断裂系统的倾角呈规律性变化,靠近挤压端的断裂倾角较大,远离挤压端断裂的倾角较小,但其逆冲的位移量大;同时,同构造沉积控制盐上层滑脱褶皱变形范围,垂向抬升主要控制盐下层叠瓦状逆冲断裂向前陆方向传播范围。构造变形过程研究显示,喜马拉雅多期运动导致克拉苏构造带构造分层的差异变形,盐上层滑脱褶皱变形范围更广,褶皱相关断层更发育,盐下层在发育前展式叠瓦状逆冲断层后会加强反冲构造的形成。研究结果揭示了喜马拉雅多期运动对克拉苏构造带动力学演化过程的影响,深化了对库车坳陷克拉苏构造带构造变形机理和演化过程的认识。

       

      Abstract: The Himalayan movement has a decisive impact on the geology and geomorphology of western China. The response of the structural deformation characteristics in Kuqa Depression to its multi−periods movement remains unsolved. Based on the interpretation of the seismic section of Kelasu structural belt in Kuqa Depression, by means of discrete element numerical simulation and structural physical simulation, this paper discusses the response characteristics and deformation evolution process of the structural deformation of Kelasu structural belt caused by multi−periods movements, vertical uplift and syntectonic sedimentation caused by Himalayan multi−periods movement under the background of compressive stress. The results show that the response of Kelasu structural belt to multi−periods movements is mainly reflected in controlling the propagation of detachment folds in the upper salt layer in the foreland direction, and the uplift intensity of folds at the compression end becomes weaker; The dip angle of the pre−spreading imbricate thrust fault system at the extrusion end of the lower salt layer changes regularly. The dip angle of the fault near the extrusion end is large, and the dip angle away from the extrusion end is small, but its thrust displacement is large. At the same time, syntectonic sedimentation controls the deformation range of detachment fold in the upper salt layer, and vertical uplift mainly controls the forward land propagation range of laminated tile thrust fault under salt. The study of tectonic deformation process shows that the multi−periods movement of Himalaya leads to the differential deformation of structural stratification in Kelasu structural belt. The deformation range of detachment folds in the upper salt layer is wider, and fold related faults are more developed. After the development of forward spreading imbricate thrust faults in the lower salt layer, the formation of recoil structures will be strengthened. The results reveal the influence of Himalayan multi−periods movement on the dynamic evolution process of Kelasu structural belt, and deepen the understanding of structural deformation mechanism and evolution process of Kelasu structural belt in the Kuqa Depression.

       

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