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Lookup NU author(s): Dr Rob Westaway
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We document the staircase of terraces of the River Tigris in the Diyarbakir area of SE Turkey, in the northern Arabian Platform, and improve control on the ages of these terrace deposits by dating of overlying basalt flows using the unspiked K-Ar technique. These fluvial terraces are formed of polymict gravel, including clasts derived from the Anatolian metamorphic terrane farther north as well as of local basalt. At least 9 Tigris terraces have been recognised so far, the highest of which, ∼200 m above present river level, marks the local transition from stacked deposition to fluvial incision, the timing of which is bounded between the mid Late Miocene and the Middle Pliocene. Our K-Ar dating indicates a hiatus in fluvial incision in the late Early Pleistocene, as basalts dated to 1.22 ± 0.02 and 1.07 ± 0.03 Ma overlie Tigris gravels at very similar levels, ∼60-70 m above the present river. The lower terraces record the subsequent entrenchment of the modern Tigris valley following an increase in incision rates in the early Middle Pleistocene, evident from the disposition of younger basalt, dated to 0.43 ± 0.02 Ma, capping fluvial gravel only ∼21-22 m above the present river level. Numerical modelling can account for the observed uplift history, as the response to coupling between surface processes and induced flow in the lower crust, with the mobile lower-crust thin (∼5-7 km thick), consistent with the known presence of a thick layer of mafic underplating at the base of the crust beneath the Arabian Platform. © Springer-Verlag 2007.
Author(s): Westaway R, Guillou H, Seyrek A, Demir T, Bridgland D, Scaillet S, Beck A
Publication type: Article
Publication status: Published
Journal: International Journal of Earth Sciences
Year: 2009
Volume: 98
Issue: 3
Pages: 601-625
ISSN (print): 1437-3254
ISSN (electronic): 1437-3262
Publisher: Springer
URL: http://dx.doi.org/10.1007/s00531-007-0266-z
DOI: 10.1007/s00531-007-0266-z
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