Location of the River Euphrates in the Late Miocene; dating of terrace gravel at Shireen, Syria

International audienceWe report gravel of the River Euphrates, capped by basalt that is Ar-Ar dated to ~9 Ma, at Shireen in northern Syria. This gravel, preserved by the erosion-resistant basalt, allows us for the first time to reconstruct the history of this major river during the Late Miocene. In response to progressive regional surface uplift, the Euphrates extended SE by ~800 km between the early Middle Miocene, when the coast was near Kahramanmara? in southern Turkey, and the Pliocene, when it lay in western Iraq, east of the Arabian Platform uplands

First report of citrus viroid v in Turkey

[No abstract available

Assessing the applicability of transcript conformation polymorphism for differentiation among Prunus necrotic ringspot virus isolates

The applicability of single and double-stranded transcript conformation polymorphism (TCP) for differentiation among Prunus necrotic ringspot virus (PNRSV) isolates was evaluated and compared with other molecular differentiation procedures. Single-stranded TCP was found to be suitable to differentiate closely related virus isolates. However, due to its high variability, it was not suitable for grouping virus isolates. Double-stranded TCP, on the other hand, enabled the division of virus isolates into major groups. Restriction fragment length polymorphism (RFLP) of the PCR products confirmed the grouping of the virus isolates but this technique was limited in its ability to detect a wide range of nucleotide modifications. Nucleotide sequence analysis was essential for the detection of strain-specific sequences but did not clearly identify most other minor modifications that are necessary for virus classification. The combination of all methods is therefore sometimes required for complete analysis

Timing of the quaternary Elazig volcanism, eastern Turkey, and its significance for constraining landscape evolution and surface uplift

The eastern part of the Anatolian plateau in eastern Turkey has experienced dramatic landscape evolution in the Late Cenozoic, surface uplift having been associated with the disruption of former lake basins and the development of the modern high-relief landscape, incised by the upper reaches of the River Euphrates and its major tributary, the Murat. Overall, the altitude of the plateau decreases gradually westward, and it has been assumed that uplift on any given timescale has varied regionally in a similar manner. However, using the Ar-Ar method, we have dated an episode of basaltic volcanism around the city of Elazig to -1.8-1.9 Ma (two alternative calculation procedures give ages of 1885±16 ka and 1839±16 ka; both ±2?. The disposition of this basalt indicates no more than -100 m of incision by the River Murat on this timescale in this area, in marked contrast to neighbouring localities where much more incision on similar timescales is indicated by the geomorphology. We interpret these variations as consequences of flow in the lower continental crust induced by surface processes, the flow being vigorous because the lower crust in this region is highly mobile due to the high Moho temperature. We thus suggest that the -1.8-1.9 Ma Elaz?g volcanism was triggered by outflow of lower crust following the emptying at -2 Ma of the adjacent Malatya lake basin; the resulting local removal of part of this lower-crustal layer can also account for the limited amount of subsequent net crustal thickening and surface uplift that has occurred locally. Local patterns such as this are superimposed onto the regional westward tilting of the surface of the Anatolian Plateau, which has facilitated the disruption of former lake basins such as this. Copyright © TÜBİTAK

Timing of the Quaternary Elazig volcanism, eastern Turkey, and its significance for constraining landscape evolution and surface uplift

The eastern part of the Anatolian plateau in eastern Turkey has experienced dramatic landscape evolution in the Late Cenozoic, surface uplift having been associated with the disruption of former lake basins and the development of the modern high-relief landscape, incised by the upper reaches of the River Euphrates and its major tributary, the Murat. Overall, the altitude of the plateau decreases gradually westward, and it has been assumed that uplift on any given timescale has varied regionally in a similar manner. However, using the Ar-Ar method, we have dated an episode of basaltic volcanism around the city of Elazığ to ~1.8-1.9 Ma (two alternative calculation procedures give ages of 1885±16 ka and 1839±16 ka; both ±2s). The disposition of this basalt indicates no more than ~100 m of incision by the River Murat on this timescale in this area, in marked contrast to neighbouring localities where much more incision on similar timescales is indicated by the geomorphology. We interpret these variations as consequences of flow in the lower continental crust induced by surface processes, the flow being vigorous because the lower crust in this region is highly mobile due to the high Moho temperature. We thus suggest that the ~1.8-1.9 Ma Elazığ volcanism was triggered by outflow of lower crust following the emptying at ~2 Ma of the adjacent Malatya lake basin; the resulting local removal of part of this lower-crustal layer can also account for the limited amount of subsequent net crustal thickening and surface uplift that has occurred locally. Local patterns such as this are superimposed onto the regional westward tilting of the surface of the Anatolian Plateau, which has facilitated the disruption of former lake basins such as this

Ar-Ar dating of late Cenozoic basaltic volcanism in northern Syria: Implications for the history of incision by the River Euphrates and uplift of the northern Arabian Platform

Ar-Ar dating of basalt flows capping terrace deposits of the River Euphrates in northern Syria has provided a new quantitative chronology for the late Cenozoic evolution of this important river system and for the associated history of surface uplift of the northern Arabian Platform through which it flows, a region of relatively strong crust that has experienced only slow deformation. Notably, fluvial deposits ~65 m above the Euphrates are overlain by basalt dated to 2717 ± 20 ka, those ~45 m above the river are overlain by basalt dated to 2116 ± 39 ka, and those 8-9 m above the river are overlain by basalt dated to 402 ± 11 ka. These new dates require the previous dating scheme, based on Paleolithic archaeology, to be revised; the Euphrates terrace deposits and the associated incised valley are much older than was previously thought. Rates of incision by the Euphrates, providing a proxy for regional surface uplift that is inferred to be the isostatic response to regional erosion, have varied significantly over the past ~3 Ma, with indications that between ~1.2 and ~0.9 Ma, there was regional subsidence, which gave rise to fluvial aggradation. This unusual pattern, involving reversals in the sense of vertical crustal motions, is interpreted to be a consequence of a relatively cold and thin mobile lower crustal layer, no more than ~5 km thick, evidently due to the presence of a much thicker underlying layer of mafic underplating at the base of the crust. This study thus indicates previously unsuspected complexity in the isostatic response to regional erosion in an area of high crustal stability. Copyright 2007 by the American Geophysical Union

Pliocene and Quaternary regional uplift in western Turkey: The Gediz River terrace staircase and the volcanism at Kula

Along the upper reaches of the Gediz River in western Turkey, in the eastern part of the Aegean extensional province, the land surface has uplifted by ~400 m since the Middle Pliocene. This uplift is revealed by progressive gorge incision, and its rate can be established because river terraces are capped by basalt flows that have been K-Ar and Ar-Ar dated. At present, the local uplift rate is ~0.2 mm a-1. Uplift at this rate began around the start of the Middle Pleistocene, following a span of time when the uplift was much slower. This was itself preceded by an earlier uplift phase, apparently in the late Late Pliocene and early Early Pleistocene, when the uplift rate was comparable to the present. The resulting regional uplift history resembles what is observed in other regions and is analogously interpreted as the isostatic response to changing rates of surface processes linked to global environmental change. We suggest that this present phase of surface uplift, amounting so far to ~150 m, is being caused by the nonsteady-state thermal and isostatic response of the crust to erosion, following an increase in erosion rates in the late Early Pleistocene, most likely as a result of the first large northern-hemisphere glaciation during oxygen isotope stage 22 at 870 ka. We suggest that the earlier uplift phase, responsible for the initial ~250 m of uplift, resulted from a similar increase in erosion rates caused by the deterioration in local climate at ~3.1 Ma. This uplift thus has no direct relationship to the crustal extension occurring in western Turkey, the rate and sense of which are thought not to have changed significantly on this time scale. Our results thus suggest that the present, often deeply incised, landscape of western Turkey has largely developed from the Middle Pleistocene onwards, for reasons not directly related to the active normal faulting that is also occurring. The local isostatic consequences of this active faulting are instead superimposed onto this "background" of regional surface uplift. Modelling of this surface uplift indicates that the effective viscosity of the lower continental crust beneath this part of Turkey is of the order of ~1019 Pa s, similar to a recent estimate for beneath central Greece. The lower uplift rates observed in western Turkey, compared with central Greece, result from the longer typical distances of fluvial sediment transport, which cause weaker coupling by lower-crustal flow between offshore depocentres and eroding onshore regions that provide the sediment source. © 2004 Elsevier B.V. All rigths reserved