Landscape evolution in orogenic plateaus: Insights from quantitative morphotectonic analysis of the Turkish-Iranian Plateau and Caucasus regions

To investigate the recent landscape evolution of the orogenic Turkish-Iranian Plateau (TIP) and the Lesser/Greater Caucasus ranges, we perform a quantitative analysis of topography and drainage networks at a regional scale. This analysis focuses on climatic-topographic swath profiles, local relief distribution, longitudinal river profiles, normalized channel steepness index (k(sn)), paleo-river profile, and chi analysis (chi). In general, we find that the evolution of topographic relief and river networks are locally controlled by Late Cenozoic volcanism, contrasts in rock strength, and neotectonic activity along regional tectonic structures. However, our results show that the influence of these factors on the landscape evolution of the Greater Caucasus is significantly different from the Lesser Caucasus and TIP. This study shows that a combination of enhanced aridity, rapid uplift of orographic barriers along the TIP margins, and exposure of resistant rock types associated with the regional volcanic activity resulted in low-relief plateau and the Lesser Caucasus surfaces that are preserved in the upper/middle Kura-Arax and Qezel-Owzan river catchments. High local relief in the flanks of the Greater Caucasus and west Alborz, downstream increase in channel steepness, and perturbations in the chi plots of the three main rivers indicate that the topography is in a transient state.We reconstruct the paleo-river profiles from the relict section of the upper Kura-Arax and Qezel-Owzan rivers and show that the last drastic fall of the Caspian base-level, which occurred during the Late Miocene-Early Pliocene, can explain the incision of similar to 500-1000 m gorges (i.e., Amardos) below major knickpoints. Furthermore, local cross-divide differences of the chi parameter reveal that disequilibrium in the plan-form geometry of the drainage networks, attributed to the upstream migration of the regional knickpoints towards the plateau interior and integration of plateau areas into the external fluvial system.