蒙古戈壁天山断裂带晚新生代构造变形与构造地貌研究

跨越中蒙边境线的戈壁天山断裂带是一条大型左旋走滑断裂带,东西展布约700 km。通过解译分析Landsat ETM卫星遥感影像和SRTM数字高程模型(DEM)数据,对戈壁天山断裂带晚新生代构造活动及其地貌特征进行了研究。结果表明,沿戈壁天山断裂带发育了一系列断层陡坎、系统的水系错位、挤压脊等典型的走滑构造地貌类型。遥感影像解译结果还显示3处系统水系错位,均受戈壁天山断裂左旋走滑运动的影响,表现出系统的左旋水平位错。结合历史地震数据、先存的基底构造和断层系统,本区地震活动性呈现出不可预测性和复杂性。此外,发育在断裂带上的3个大型挤压脊构造中:Karlik Tagh和Gurvan Sayhan就位于走滑断裂的终端,其走滑分量减弱并逐渐转为以逆冲分量为主的构造特征。Nemegt Uul位于2条不连续的走滑断裂的汇合和叠置部位。走滑断层均穿过了挤压脊构造,同时伴随有逆冲作用分量,造成了挤压脊沿走向和垂直走向上的构造地貌生长,显示了是陆内造山带演化的重要过程。

Late Cenozoic structural deformation and tectono-geomorphic features along the Gobi-Tianshan Fault System

Abstract: The Gobi-Tianshan Fault System (GTFS) extending over 700 km long is one of the largest strike-slip faults in the Central Asia Orogenic Belt (CAOB), which was considered to accommodate the eastward extrusion of Tibet. On the basis of tectono-geomorphic interpretation of satellite remote sensing images along GTFS, this study aims to document the Late Cenozoic structural deformation and geomorphic features. Geomorphic features, such as fault scarps, displaced rivers and varied restraining bends, are well developed around the GTFS. Visible fault scarps cutting across Late Cenozoic alluvial sediments, whereas low mountain-front sinuosities and deeply incised narrow canyons in the range front can indicate Late Cenozoic fault activity. The authors identified a ca. 2000 m-long lateral offsets of rivers, which are related to prolonged geomorphic growth of the GTFS. Historical earthquake data are consistent with deforming continental interior region, with tectonic loading shared amongst a network of faults, which indicates a complex earthquake prediction. Meanwhile, three restraining bends were identified in the study area: Karlik Tagh, Gurvan Sayhan and Nemgt Uul, of which the first two restraining bends are located in the two termination zones of the strike-slip fault, whereas the last one occurs in the converging and overlapping position of two separate strike-slip fault segments. Strike-slip fault cutting through the regions of restraining bend mountain ranges might have been an important mountain-building process in the CAOB.