The uplift of the Eastern Anatolian Plateau unraveled by river network analysis.

Continental collisional zone may include high-standing plateaus, both internally and externally drained. When endorheic basins are integrated into external drainage networks, the rivers could retain first order information on the capture as well as the interplay between climate and tectonic processes. The Eastern Anatolian Plateau (EAP) of the Arabia-Eurasia collision zone is one of the most representative examples of collisional plateau. It has a mean elevation of ~2000 m, presents three main endorheic basins (Van, Sevan and Urmia lakes), and is mostly drained by three river networks: the Kura-Arax drainage system to the NE, the Ҫoruh to the NW, and the Euphrates-Tigris to the SW. Seismic data indicate the presence of a thinned or totally removed lithospheric mantle beneath the plateau explaining the high heat flow and the late Cenozoic volcanic activity in the area. Despite the great number of studies on the EAP, its uplift history is still debated.

In this study we quantitatively investigated the drainage systems (river longitudinal profiles and chi-plots) and the general topographic features (swath profiles, slope, local relief, filtered topography) of the EAP. The results describe a topographic configuration characterized by a high-standing, low-relief plateau centered in the area of Lake Van, but strongly disrupted by tectonic structures with the formation of local topographic highs and lows that include endorheic basins. The fluvial network pattern is strongly disorganized and controlled by active tectonic structures. The irregular longitudinal profiles indicate that rivers are in a transient state of disequilibrium because of regional uplift, capture events or local tectonic activity. The presence of an uppermost fluvial segment characterized by low channel steepness suggests that the plateau interior has not been reached yet by the erosive wave produced by uplift. The chi-plots of the rivers draining the EAP suggest a complex uplift history, evidencing differences between the northern and the southern portions of the plateau in terms of uplift history and drainage system evolution. This uplift pattern is partially confirmed by the stratigraphic record documenting a southward younging transition from a marine to a continental depositional environment. In conclusion, the EAP is a high-standing plateau where the integration of hydrography into it is ruled by regional differential uplift and active tectonic structures.