Asymmetric uplift in the NW Iranian Plateau: An insight from the dynamic divide migration of Ardebil Basin

Abstract

<p>Drainage divides, the elevated terrain that separates neighboring drainage basins are dynamic features of a landscape that regularly migrate over time due to the development of river networks. Tectonic uplift may considerably influence such a migration by making some basins aggressors with respect to the adjacent ones. In this study, we focus on the effects of tectonic uplift on the Ardebil Basin drainage divide located adjacent to the central Talesh Mountains in the NW sector of Iranian Plateau. Talesh Mountains are prominent tectonic features of the landscape associated with the compressional stresses transferred from the Arabia-Eurasia continental collision. The structural evolution of this range is delineated by several deformation phases in the Late Cenozoic. The regional uplift associated with the right-lateral strike-slip kinematics with a reverse component of the N-NW-trending Talesh Fault, which bounds the Talesh Mountains to the east, has an important role in the tectonic activity of the region. The effects of these tectonic uplift and deformation phases on the landscape and their footprints on the geomorphological architecture of the study area are not fully described to date. Therefore, we used the tools for quantifying drainage divide stability (χ and Gilbert metrics) in order to outline the spatial pattern of uplift in this area. Since, a single divide may be heterogeneous in channel elevation, relief, and gradient values in its different portions, we segmented the Ardebil Basin main divide into 14 sections to calculate the Gilbert metrics and χ. Considering the uniformity of the cross-divide precipitation and rock erodibility, we can infer that divide migration is occurring in the study area in response to the asymmetric uplift and erosion patterns. The results of Gilbert metrics show that the NW and SE sectors of the Ardebil Basin divide are stable, suggesting a quasi-steady state condition. However, based on the χ index, these segments have the potential to move towards the interior of the plateau. Conversely, the NE segments of the main divide are dynamic and currently moving towards the SW, as suggested also by the χ index map. Therefore, we infer that the NE sectors of the Ardebil Basin are in an uplift-driven migration status as a result of an asymmetric uplift controlled by the activity of the Talesh Fault.</p>