Akademik Veri Yönetim Sistemi
CURRENT SCIENCE, cilt.84, sa.8, ss.1090-1101, 2003 (SCI-Expanded)
Western Turkey forms the eastern part of the Aegean extensional province. In the 1980s it was accepted that vertical crustal motions in this region are caused solely by this active normal faulting, with footwall localities uplifting and hanging-walls subsiding. The presence of marine sediments, interpreted as Pliocene, at altitudes in excess of 400 m in some hanging-wall localities provided-in the late 1980s-the first clear evidence of Pliocene-Quaternary regional surface uplift. However, it has since been argued that the incision of river gorges in this region has been caused instead by localized uplift in normal-fault footwalls. We review the available geomorphological and sedimentary evidence from the Denizli area, within the drainage catchment of the Buyuk Menderes river, in support of similar to400 m of Plio-Quaternary regional surface uplift We also examine the gorge reach of the Gediz river near Usak, where a staircase of four high terraces, formed of cemented fluvial gravel at similar to360, similar to330, similar to255, and similar to225 m above river level, is identified. Farther downstream, a similar terrace, similar to200 m above this river and so tentatively correlated with the similar to225 m terrace upstream, was also identified within the Quaternary volcanic field around Kula. Nearby, a slightly lower (similar to190 m) terrace gravel is capped by basalt, K-Ar dated to similar to1.2 Ma; below this, other similar terraces form a lower-level staircase. We interpret this evidence as indicating uplift rates of similar to0.1 mm a(-1) or more in the latest Pliocene, when the staircase of cemented high terraces appears to have formed, relative stability for much of the Early Pleistocene, but renewed uplift at rates approaching similar to0.2 mm a(-1) in the Middle and Late Pleistocene. The resulting uplift history resembles what is observed in other regions, and has been modelled as the isostatic response to changing rates of surface processes linked to global environmental change, with no direct relationship to the crustal extension occurring in western Turkey. 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, the local isostatic consequences of which are superimposed onto this 'background' of regional surface uplift.