Climatic and tectonic effects on terrace formation during the late quaternary in the Upper Yeşilirmak Valley, northern Turkey

Abstract

This study was carried out in the upper course of the Yeşilırmak River, which is one of the biggest rivers reaching the Black Sea, northern Turkey. We distinguished two fluvial terraces and dated them using OSL technique. T2 is the young terrace and situated at ~11 m above the actual river (at 620 m asl). T1 is the youngest and situated at ~5-6 m above the actual river (at 605 m asl). From the lower dated terrace (T1) was dated 6735 ka, 5277 ka and 4226 ka, respectively. From the higher dated terrace (T2) was dated 24,139 ka, 22,008 ka, 12,694 ka and 11,307 ka, respectively. While the higher terrace aggraded during three important cold periods (Heinrich 2 event (H2), the Last Glacial Maximum (LGM) and the Younger Dries (YD), the lower terrace (the present floodplain) aggraded during the Holocene Climatic Optimum (HCO). The river incised during transition from the LGM to Holocene transition and after the HCO. the Yeşilırmak has incised its valley ~11 m during the last 24 ka. These results indicate an average incision rate of 1.25 mm/yr (1.25 m/ka).