Neotectonics in the eastern North Anatolian fault region (Turkey) advocates crustal extension: mapping from SAR ERS imagery and Digital Elevation Model

Abstract

This paper concerns the neotectonics of the eastern part of the Anatolian block bounded, respectively, to the north and the east by the North Anatolian (NAF) and the East Anatolian faults (EAF), meeting at Karlıova. The study is based on imagery of Synthetic Aperture Radar (SAR), scenes acquired by the European Remote Sensing (ERS) satellite and on views of a Digital Elevation Model (DEM), complemented with fault analysis in the field. We show that extensional tectonics associated with transcurrent displacements prevail in the Karlıova triangle and beyond. New local releasing bends or pull-apart basins and push-up structures along the NAF have been demonstrated. More importantly, Anatolia is composed of blocks less than 50 km in width, that are tilted and move relative to each other. They are compatible with a detachment within the crust of Anatolia. We argue that an escape wedge has migrated through time from west to east, with successive jumps to form the present-day Karlıova triangle. At each stage, the escape wedge was easterly bounded by a NE–SW-striking fault zone similar to the EAF. In each escape wedge, clockwise block rotations predate strike-slip tectonics along the N110°E-striking NAF. This is the case for instance for the Erzincan Basin where the first movements were parallel to the SW-striking Ovacık Fault, an early equivalent of the EAF, and turned later to the west. The detached crustal blocks moved southwestward, then westward and extended at the same time in order to occupy the increasing surface within the successive escape wedges. This is not the behaviour of simple lateral extrusion of the Anatolian lithospheric block induced by forces applied at its boundaries by the adjacent plates, but rather that of detached crustal blocks submitted to extension as a consequence of backward retreat of the Hellenic slab and buoyancy forces arising from crustal thickness differences.