关键词: 构造地貌, 地貌结构, 活动断裂, 河流阶地, 冲洪积扇

Abstract: The geomorphic features. especially the changeable structure of alluvial-pluvial fan and the offset difference of river terraces along the North Qinling Piedmont fault zone, show that there are three characteristics of the fault zone activity between Baoji and Lantian: (1)The main moving type is vertical along the fault since Quaternary Period. its active nature and level are different in space and time. The western and eastern segments in the northern-wall(basin side) of the fault slightly subside and the middle segment greatly goes down relative to the southern-wall (mountain side) in the early Pleistocene. the western and eastern parts inversely rise. but the middle part continues to sink violently in the middle Pleistocene. the western and eastern segments intensely uplift, and the middle segment rises slightly in the late Pleistocene. The characteristics of vertical displacement and average moving rate of North Qinling Piedmont fault zone agree with the active feature of fault segmentation based on the analysis of the first and second terraces which are well preserved and dated by the method of thermoluminescence. (2) The river terraces across the Piedmont fault in the uplift-wall is higher at the exits of the mountain than the parts at the upper reaches of rivers, which reflect that the block of Qinling mountain continues to tilt from north to south since Quaternary Period. (3) The characteristics of alluvial-pluvial fan structure and altitude of deposit bed crossed by fault on both walls of the fault zone show there are a lot of listric faults along the Piedmont.The characterisctics above provide a very important scientific basis for further understanding the forming mechanism of the Weihe fault basin and the Qinling fault block rnountain.

Key words: tectonic, landform, geomorphic, structure, active, fault, river, terrace, alluvial-pluvial, fan