Geomorphic Response to Rapid Uplift in a Folded Structure: The Upper Tigris Case

Abstract

The River Tigris is one of the most significant rivers in the Middle East. All the landscapes drained by the river from Hazar Lake and neighbouring mountains down to the Iraqi–Syrian border in the Cizre region are mainly characterized by folded structures, often faulted, widely affecting limestone series. In this structural context, the incision of rivers shaped Jura-type and Appalachian-type morphologies. Meanwhile, tectonics has also generated rapid changes in the river network. The rapidity of post-Mio-Pliocene uplift caused deep incision of canyons into rising and thrusting folds, and preservation of a few remarkable Mio-Pliocene and Pliocene topographies. The chapter presents a geomorphological survey of the headwaters of the River Tigris, which is formed of two branches. The meeting of these branches (Maden and Birkleyin streams) downstream Egil city forms the proper River Tigris. The paper examines the landscapes in the Euphrates–Tigris divide area where Hazar Lake is located. Landscapes in both the Maden and Birkleyin basins record the Eastern Anatolian Fault Zone activity during the Pleistocene, with epigenic canyons and meanders, dry valleys resulting from captures, and karstic systems deepening during uplift. Dams (constructed or under construction) have a profound impact in the Tigris and tributary valleys. The end of this programme will provoke the drowning of almost half the main river valley floor down to the Turkish–Syrian/Iraqi border (from Bismil to Cizre) and the loss of ancient settlements, towns and historic heritage that are located along the Tigris floodplain.