River capture and divide migration of the Zhuozishan area in the northwestern margin of the Ordos Block

Divide is a dynamic feature of a landscape that routinely migrates, either through progressive or discrete river capture, in some cases even leading to the complete reorganization of river networks. Most of the existing geomorphological or drainage evolution studies focus on the single river capture, and few report on the overall movement and the geomorphologic adjustment of divide.Recently, it was proposed in a digital study of fluvial geomorphology that the chi (χ) value difference on both sides of the drainage divide could be used to explain the large-scale river capture and demonstrate the reorganization of drainage when describing the dynamic migration process of divide. In this paper, the chi (χ) values were calculated using the 12.5 m DEM data. The chi (χ) values were higher in the east and lower in the west, indicating an eastward migration. The lithological erosion resistance is the main factor controlling the eastward migration of the divides in Zhuozishan under the condition that there are no obvious differences in the tectonic uplift and precipitation conditions on the east and west sides. When the Cambrian and Ordovician limestones with stronger erosion resistance lie in the west wing of the Zhuozishan anticline, the other weak sedimentary clastic rocks located in its lower part, the river in the west wing would be through the core of the anticline, laterally capturing the rivers on the east of the anticline.