库车前陆褶皱-冲断带盐构造差异变形和分段性特征探讨

通过野外地质调查、GIS分析、三维可视化分析、盐相关构造变形样式的探讨、平衡剖面分析以及缩短量和缩短率的估算,表明库车前陆褶皱—冲断带盐构造具有明显的差异变形和分段性特征。差异变形主要表现为纵向上不同层次变形的差异性以及平面上构造变形的分带性与分段性。段与段的分界一般为走滑断层,在野外可见大量断层三角面、擦痕、阶步、错断的山脊和河谷等现象,地貌GIS分析可以揭示一些构造分段的细节特征,三维可视化反映了隐伏的残留盐枕的分段性。不同的段具有迥然不同的构造变形样式,平衡剖面分析可以估算出不同段落缩短量和缩短率的明显差异。盐构造差异变形和分段性的形成一方面受控于天山造山带的分段性活动过程,还和盐岩层本身的沉积学特征及盐体展布格局有关,同时还明显受到基底构造的控制,与基底古隆起、基底断裂及古构造断坡的发育密切相关。

Differential Salt Tectonic Deformation and Segmentation of the Kuqa Foreland Fold-Thrust Belt, Tarim Basin, Northwest China

The differential salt tectonic deformation and segmentation in the Kuqa foreland fold-thrust belt have been observed by field observation, geographic information system(GIS) analysis, 3D visualization, salt-related structural styles, balanced cross section, and estimation of shortening strains and rates. The differential salt tectonic deformation is mainly represented by structural differentiation at different levels, and structural zonation and segmentation in transverse and longitudinal sections. The boundaries between the structural segments are mainly strike-slip faults or tear faults revealed by terminal facets, scratches, steps, misplaced hills and river valleys. The GIS analysis maybe indicates some characteristic details of structural segmentation. Several segments of buried residual salt pillows are revealed by 3D visualization. Distinct structural styles occur in different segments. The analysis of balanced cross section may estimate differential amounts and rates of shortening in different segments. The origin of differential salt tectonic deformation and segmentation may be, on one hand, controlled by the segmentation of the Tianshan mountains, and, on the other, are related to the differential sedimentation and distribution of the salt beds, pre-exist faults and basement uplifts as well as paleotectonic ramps.