Geomorphological evidence for a changing tectonic regime, Pasinler Basin, Turkey

Abstract

The Pasinler Basin, in the ‘East Anatolian Contractional Province’, features a suite of geomorphological zones, visible in the field, air photographs and Landsat and Shuttle Radar Topography Mission (SRTM) digital elevation model imagery. These zones reflect past and current tectonically influenced processes. Relicts of the Erzurum–Kars Plateau representing Mio-Pliocene volcanism, associated with transtensional tectonics, have been modified by two stages of drainage development: an earlier, shallow valley network, which was modified following uplift and tilting to form the present system characterized by deep narrow valleys that supply alluvial fan complexes. These fans discharge onto the present, aggradation-dominated basin floor. Initial normal faulting induced massive slope failures on the basin's northern margin. This extensional phase within the basin was reversed by the Late Pleistocene, with thrust faults modifying and producing landforms, and affecting sediment sequences, along both its northern and southern margins. The shift from a transtensional regime, and the associated volcanism, to normal faulting in the Pliocene to Early Pleistocene, and then to the present regime of compression-induced thrusting appears to correspond to a regional tectonic shift resulting from the collision of the Eurasian and Arabian plates and the subsequent westwards movement of the Anatolian microplate.