Dating Quaternary volcanism and incision by the River Tigris at Diyarbakır, southeast Turkey

Abstract

Abstract New high‐precision Ar‐Ar dating of basalt underlying the city of Diyarbakır, southeast Turkey, constrains the Quaternary incision history of the River Tigris, strengthening the pre‐existing chronology based on magnetostratigraphy and K‐Ar dates. The basalt, which overlies Tigris terrace gravel 70 m above the river, is part of the Karacadağ shield volcano complex centred ca. 60 km to the southwest. The reverse‐magnetised Diyarbakır basalt, one of relatively few flow units to reach the Tigris valley axis, has been dated to 1196 ± 19 ka (±2 σ ). Two lower terraces have been recognised in the Diyarbakır area, 46 and 32 m above the present river, with at least one other further downstream. From this evidence the rate of Middle‐Late Pleistocene incision by the Tigris can be estimated; it probably reached ca. 0.07 mm a −1 , reflecting the characteristic global increase in uplift rates observed at that time. Copyright © 2007 John Wiley & Sons, Ltd.