River terrace sequences in Turkey: sources of evidence for lateral variations in regional uplift

This paper reviews river terrace staircases in Turkey and examines their relation to regional uplift. Turkish fluvial records are shown to be similar to their counterparts in Europe, with aggradation concentrated in cold climatic stages, despite differences in present-day climate between these two regions. Furthermore, as in Europe, these Turkish river terrace sequences provide evidence for increases in regional uplift rates in the Late Pliocene and Middle Pleistocene. In both regions, this effect is unrelated to senses and rates of plate motion, being instead the result of crustal thickening caused by lower-crustal flow induced by surface processes. From the fluvial evidence, estimated amounts of regional uplift since the Miocene are typically c. 400 m in western Turkey and in the area of the border with Syria. However, they increase northward and eastward to c. 1 km or more in northeastern Turkey on this time-scale, reflecting the regional variations in mean altitude of the land surface. Estimated typical uplift rates during the Middle and Late Pleistocene have been c. 0.1 mm a−1 in the Arabian Platform and c. 0.2–0.3 mm a−1 in western and northern Turkey. These variations are interpreted as the isostatic response to lateral variations in erosion rates.