西昆仑山前冲断带晚新生代构造地貌特征

在卫片解译、DEM数据处理、地形图分析与剖面制作的基础上,结合野外构造地貌考察与观测,对西昆仑山前冲断带的构造地貌特征进行了定量、半定量的研究。沿山前发育系统的水系变化、冲积扇变化、不对称背斜、大规模正断裂、不对称河流阶地等典型的构造地貌,表明这条由南向北逆冲的冲断带在扩展过程中存在着由西向东迁移的特征。冲断带的东西分段以桑株河为界,以西发育固满背斜,其构造样式为向北的逆冲伴随向南的反冲;以东发育一系列不对称的背斜,表现出明显的由南向北逆冲的特征,地表无明显的反冲构造出现。利用生长地层和河流阶地估算了西昆仑山的隆升速率:晚上新世—早更新世以来的最低隆升速率为0.21～0.25mm/a,100ka以来的隆升速率为1.5mm/a。

Late Cenozoic morphotectonic features of the thrust belt in the front of the West Kunlun Mountains

Based on the interpretation of Landsat ETM satellite images, processing of DEM data, analysis of topographic maps and construction of profiles, combined with field morphotectonic investigations and observations, the authors conducted quantitative and semi-quantitative studies of the morphotectonic features of the West Kunlun piedmont belt. Typical morphotectonic features such as the change of drainage systems, change of alluvial fans, asymmetric anticlines, large-scale normal faults and asymmetric river terraces along the piedmont indicate that this north-vergent thrust belt migrated from west to east in the process of its propagation. The thrust belt is separated into the east and west segments by the Sanju River. In the west segment there occurs the Guman anticline, whose structural style is characterized by north-vergent thrusting, accompanied by south-vergent back thrusting;whereas in the east segment there occur a number of asymmetric anticlines, which show distinct features of north-vergent thrusting, and no distinct back thrust is found at the surface. Uplift rates of the West Kunlun Mountains have been estimated based on the growth strata and river terraces:the minimum uplift rates were 0.21-0.25 mm/a from the late Pliocene-early Pleistocene and 1.5 mm/a since 100 ka BP.