关键词: 中条山北麓断裂, 河流地貌, 构造演化

Abstract:

As an important part of the land geomorphic unit, river is one of the main geological forces to shape the surface morphology. The fluvial geomorphic development characteristics are extremely sensitive to tectonic activities and record rich tectonic deformation information in geological history. Therefore, through the information extraction and quantitative analysis of bedrock river, we can reverse the relevant information about the tectonic evolution history. By extracting topographic information, comprehensively analyzing the spatial differences of fluvial geomorphological parameters, sieving the influencing factors such as tectonic, climatic and lithological characteristics, and quantifying the intensity of tectonic activity have become an important research tool for the segmental differences of active faults.

The Northern Zhongtiao Mountains Fault is an active fault that controls the uplift of the Zhongtiao Mountains and subsidence of the Yuncheng Basin, and can be divided into the Hanyang, Yongji, Yanhu and Xiaxian sections from south to north. The activity of each section of the fault is closely related to the shaping of the present-day topography of the Zhongtiao Mountains, and it is a typical area for applying quantitative analysis of fluvial landform to the study of the segmentation differences along the fault. So we can effectively study the distribution characteristics of tectonic activity in the fault zone through the river geomorphological features of Zhongtiao Mountains. In this paper, by extracting information on the river topography of the bedrock mountain watershed system on the northern slopes of the Zhongtiao Mountains, parameters such as the normalized steepness index k_sn, slope S, geometric features of the stream longitudinal profile of the drainage system, the location of the knickpoints and the amount of variant incision between upstream and downstream of the knickpoints are obtained. The results show that the bedrock channels on the northern slopes of the Zhongtiao Mountains has experienced accelerated incision in the longitudinal direction, and that the spatial variation of geomorphological parameters such as the normalized steepness index k_sn, slope S and fluvial incision in the lateral direction is dominated by tectonic uplift, with high values in the Hangyang-Yongji section and decreasing in a segmental manner towards the west, which is consistent with the topographic relief of the Zhongtiao Mountains, but contradicts the high slip rate area and the Cenozoic subsidence centre(the Salt Lake).

The geomorphic response to the slip rate is inconsistent with the topographic relief of the Zhongtiao Mountains, which is high in the west and low in the east. The high value area of geomorphic parameters reveals that the present active tectonic area of the Northern Zhongtiao Mountains Fault is located in the Hanyang-Yongji segment in the south, rather than the salt lake segment with high activity rate. The reason may be related to the migration of part of the activity of Huashan piedmont fault along the NE-trending hidden fault of Huayin Shouyang to the Hanyang Yongji segment of Zhongtiao Mountains. It suggests that the tectonic activity center of the Northern Zhongtiao Mountains Fault moves westward. Compared with the structural deformation caused by the change of sedimentary center, the time scale of river geomorphology response to structural deformation is shorter, and the landform is transformed most rapidly, which leads to the inconsistency between the geomorphological parameters and structural activities of the fault at the Northern Zhongtiao Mountains Fault.

Key words: the Northern Zhongtiao Mountains Fault, fluvial landform, tectonic evolution