Interplay between tectonics and surface processes in the evolution of mountain ranges: Insights from landscape dynamics, uplift, and active deformation of Talesh Mountains (NW Iranian Plateau margin)

Abstract

Drainage divides are dynamic features of a landscape that migrate over time during the development of river networks. In this study, we focused on the geomorphic response of a landscape to the interaction among tectonics, climate, and lithology in the Talesh Mts. along the northwest of the Iranian Plateau. The footprints of these competing forces have been analyzed by divide stability analysis and applying χ, χQ, and Gilbert metrics. Additionally, we examined the effects of bedrock erodibility on landscape evolution processes by measuring the mechanical rock strength of the lithological units in different sectors of the mountain range. The distribution of the χ values suggests a disequilibrium of the drainage networks across the whole main divide and its tendency to migrate towards the interior of the plateau. In contrast, Gilbert metrics, which focuses on a narrow topographic zone across the divide, suggest that the uppermost divide in the northern and southern Talesh Mts. is stable. Moreover, asymmetry in Gilbert metrics across the central part of the range suggests that the divide might be migrating towards the plateau interior. The possible scenario for the whole divide's behavior is associated with the contrasting erosion rates across the divide. In the northern and southern sectors of the Talesh Mts. range, the erosional wave related to the most recent uplift pulses has not reached the divide yet. Mechanism of topographic rejuvenation is controlled by heterogeneous uplift of strong bedrock units in the northern and southern sectors, and weak bedrock units outcropping in the central sector, initiated topographic rejuvenation largely in the central Talesh Mts. Parallelly, the precipitation has a limited effect in assisting and magnifying the divide mobility, reorganization, and landscape transience. In general, we can infer that divide is in a transient state due to the spatially varying rock uplift and bedrock erodibility.