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

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 Karacadag 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 AE 19 ka (AE2s). 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 À1 , reflecting the characteristic global increase in uplift rates observed at that time.

Climate-controlled river terrace formation in the Kızılırmak Valley, Cappadocia section, Turkey: Inferred from Ar–Ar dating of Quaternary basalts and terraces stratigraphy

“…Contrary to the proposition made for the aggradation of the Kızılırmak terraces, as part of the scheme suggested for the rivers of Turkey , especially the big rivers such as the Gediz (Westaway et al, , 2006, Ceyhan , Fırat (Euphrates) and Dicle (Tigris) (Bridgland et al, 2007), it was the cold period when aggradation took place. The terraces were assigned to the cold periods of the marine oxygen isotope stages.…”

“…For instance, the current high incision rate in the Gediz valley which started after 1250 ka started in the Kızılırmak at~1228 ka. An increase was found in the incision or uplift rates in the Rivers Gediz , Dicle (Bridgland et al, 2007) and Fırat in the early Middle Pleistocene, which was attributed to the erosional isostasy which increased with the climate deterioration~0.9 Ma. However, the fact that the incision rate in the Kızılırmak valley stayed the same from 1228 ka to the mid Middle Pleistocene shows that the river incision rate cannot be explained solely by erosional isostasy.…”

“…Recently, the basalt covers on some terraces in various Turkish rivers such as Gediz (Westaway et al , 2006Maddy et al, 2005), Dicle (Tigris) (Bridgland et al, 2007) and Ceyhan were dated using the K-Ar or Ar-Ar technique, and it was concluded that the terraces had formed under the influence of obliquity during the Early Pleistocene and under the influence of eccentricity during the Middle and Late Pleistocene. Additionally, these studies suggest that the main periods of terrace aggradations in Turkey probably occurred during cold periods or glacial maxima.…”

Late Cenozoic regional uplift and localised crustal deformation within the northern Arabian Platform in southeast Turkey: Investigation of the Euphrates terrace staircase using multidisciplinary techniques

“…1) is a significant repository for information of this type, derived from the terrace sequences of the rivers Euphrates and Tigris (e.g. Bridgland et al, 2007;Demir et al, 2007aDemir et al, ,b, 2008Westaway et al, 2009). This crustal province adjoins the southern margin of the eastern Anatolian Plateau across the suture of the former Southern Neotethys ocean (Fig.…”

Late Cenozoic uplift of the Amanos Mountains and incision of the Middle Ceyhan river gorge, southern Turkey; Ar–Ar dating of the Düziçi basalt

“…Use of dated long-timescale river terrace staircases is emerging as an important method for investigating this topic, given that fluvial incision can often serve as a proxy for surface uplift (e.g., Bridgland and Westaway, in press). K-Ar or Ar-Ar dating of basalt flows that cap fluvial terrace deposits is a robust technique for dating river terraces that has been widely used in volcanic regions worldwide, for instance, in the French Massif Central (e.g., Pastre, 2004), the Colorado Plateau of the western USA (e.g., Pederson et al, 2002), and in Turkey (e.g., Westaway et al, 2004Westaway et al, , 2006bBridgland et al, 2007) and adjoining parts of Syria . It is applied here to the terraces of the River Ceyhan within the Amanos Mountains in southern Turkey; these mountains form part of the boundary zone between the African and Arabian plates (Fig.…”