Preservation by basalt of a staircase of latest Pliocene terraces of the River Murat in eastern Turkey: Evidence for rapid uplift of the eastern Anatolian Plateau |
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| Authors: | Tuncer Demir Ali Seyrek Herv Guillou Stphane Scaillet Rob Westaway David Bridgland |
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| Institution: | aDepartment of Geography, Harran University, 63300 Şanlıurfa, Turkey;bDepartment of Soil Science, Harran University, 63300 Şanlıurfa, Turkey;cLaboratoire des Sciences du Climat et de l'Environnement, Domaine du CNRS, Bâtiment 12, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France;dThe Open University, Abbots Hill, Gateshead NE8 3DF, UK;eDepartment of Geography, Durham University, Durham DH1 3LE, UK |
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| Abstract: | Unspiked K–Ar dating makes the age of the Çakmaközü basalt in eastern Turkey 1818 ± 39 ka (± 2σ). This basalt overlies a staircase of four terraces of the River Murat, a Euphrates tributary, each separated vertically by  20 m. We deduce from the relationship with the basalt that these fluvial deposits aggraded during successive 40 ka climate cycles around the Pliocene–Pleistocene boundary (probably MIS 72-66). The incision and rock uplift at 0.5 mm a− 1, thus indicated, are roughly consistent with the 500 m of entrenchment of this 1.8 Ma Murat palaeo-valley into a former lake basin since the Mid-Pliocene climatic optimum. We infer that the 130 m of incision in this locality since 1.8 Ma dramatically underestimates the associated rock uplift, estimated as 600 m. The 1100 m of rock uplift and 800 m of surface uplift thus estimated since the Mid-Pliocene indicate (assuming Airy isostatic equilibrium) 5 km of thickening of the continental crust, from 37 km to the present 42 km. Eastern Anatolia was thus at a much lower altitude in the Mid-Pliocene than at present, consistent with the low-relief lacustrine palaeo-environment. We infer that the subsequent development of topography and excess crustal thickness are being caused by coupling between surface processes and induced flow in the lower crust: climate change following the Mid-Pliocene climatic optimum resulted in faster erosion that has drawn mobile lower crust beneath the study region. |
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| Keywords: | Turkey Eastern Anatolia Pliocene Pleistocene uplift basalt K-Ar |
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