Cenozoic tectonics and evolution of the Euphrates valley in Syria

Abstract

Abstract Late Cenozoic tectonics affected the evolution of the Euphrates river valley in northern Syria. Data on the height and composition of terraces and new K–Ar dating of overlying basalts are presented for the area between the Assad Reservoir and the town of Abou Kamal. The presence of the Late Cenozoic Euphrates Fault, longitudinal with respect to the valley, is established by the lower height of the terraces on the NE side of the valley compared with the same terraces on the SW side. Geophysical profiling (dipole axial sounding; correlation refraction method and georadar) across the southern side of the valley (opposite the town of Ar Raqqa) confirms the offset on the fault as >25 m. Movements along the transverse Rasafeh–El Faid fault zone and the Halabiyeh–Zalabiyeh deformation zone have resulted in local uplift and the splitting of river terraces. During the Pliocene–Early Pleistocene, uplift and strong incision of the Euphrates valley propagated from near the Syrian–Turkish border to near the Iraq–Syrian border. The Euphrates began to deposit alluvium onto the pre-existing low-lying Mesopotamian Foredeep at c. 3.5 Ma. Intense incision began by late Late-Pliocene time to form terrace IV. Comparable incision further downstream began during the Early Pleistocene to form terrace III.