Divide migration in response to asymmetric uplift: Insights from the Wula Shan horst, North China

Drainage divides play significant roles in shaping landscapes. Nevertheless, they are not static through space and time. Previous numerical models have demonstrated divide motions in response to asymmetric tectonic uplift. However, natural examples that have nicely recorded these processes and hence could verify the results of numerical simulations are still lacking. In this contribution, we integrate the results of digital elevation models (DEMs)-based morphotectonic analysis with the tectonic landforms observed during field surveys to investigate the status of topography and probable drainage evolution history of the Wula Shan (Shan means ‘Mountain(s)’ in Chinese), a roughly west-east trending horst block bounded by normal faults in the Hetao Graben, North China. The results demonstrate that the differences of obtained geomorphic indices are significant between the southern and northern drainage basins; higher hypsometric integral (HI) and normalized channel steepness (ksn) values, and lower ratios of valley floor width to valley height (VF) indicate higher tectonic uplift rate at the southern flank. The main divide of the Wula Shan had migrated northward, which was probably caused by the decrease of asymmetry in vertical uplift associated with the margin faults. We suggest the results of this study may shed new light on divide mobility as well as landscape evolution in actively extending regions.