Initial topography matters in drainage divide migration analysis: Insights from numerical simulations and natural examples

The stability of drainage divides is widely used for tectonic reconstruction. A drainage divide migrating from the high-uplift side towards the geometric center is usually thought to indicate a decrease of uplift asymmetry in a mountain belt. However, counterexamples exist. To explore this, we firstly use numerical simulation to reveal a phenomenon of drainage divide migration, in which the main drainage divide of a mountain belt migrates from the edge of the high-uplift side towards the geometric center in response to the initiation of asymmetric uplift. We then take the Xizhou Shan horst in North China as a natural example to show the pattern of divide migration found in the numerical simulation. We use three methods to measure the stability of the main drainage divide in the Xizhou Shan based on the ALOS digital elevation model. Results show that most segments of the divide are migrating southeastward. We further analyze the stable location of the main drainage divide in response to the tilt of the horst. Results reveal that the main drainage divide is migrating from the edge of the high-uplift side towards the geometric center to achieve a new steady state in response to the Late-Cenozoic asymmetric uplift. We conclude that not all drainage divides migrating towards the geometric center indicate a decrease of uplift asymmetry. Moreover, we proposed two different patterns of divide migration in response to the asymmetric uplift, which indicate that the migration of a drainage divide is controlled by both the initial position and the final stable position.