The Uplift of an Early Stage Collisional Plateau Unraveled by Fluvial Network Analysis and River Longitudinal Profile Inversion: The Case of the Eastern Anatolian Plateau

Abstract

Orogenic plateaus of continental collision zones exhibit landforms and fluvial networks that retain first-order information on their topographic evolution and vertical growth. The inversion of river longitudinal profiles allows to reconstruct the base level fall history of plateaus, supporting the study of landscape evolution in the frame of geodynamic models. The Eastern Anatolian Plateau (EAP) of the Arabia-Eurasia collision zone is a plateau at an early stage of development. It stands at ∼2,000 m, presents endorheic basins, and is drained by three main river networks. Seismic data indicate a thinned lithospheric mantle that explains the late Cenozoic volcanic activity. Despite the number of studies on the EAP uplift, its history is still debated. In this study we investigated the EAP hydrography and topography, and we inverted the longitudinal profile of one of the main rivers: the Arax River. The results describe a high-standing, low-relief plateau drained by a hydrography, controlled by active tectonics. Longitudinal profiles and χ-plots illustrate rivers in disequilibrium with channel steepness increasing downstream. The elevation of marine deposits indicates a surface uplift of ∼2,000 m, ∼500 m of which are of residual topography. This upheaval occurred by two increases: the first one at 10–11 Ma with the opening of a slab window and the arrival of a mantle flow from Arabia and the second one at ∼5 Ma with the continued inflow coupled with isostasy. Our results describe the early stage of collisional plateau development, distinguishing the contribution of deep processes and isostasy to the topographic growth.