Research Information System
GEOMORPHOLOGY, vol.357, 2020 (SCI-Expanded)
The timing and geomorphological consequences of high-angle normal faulting in the Buyuk Menderes Graben (W Anatolia) is an essential yet poorly studied issue that has been evaluated mostly regarding detachment faulting in the Central Menderes Core Complex. However, this subject has direct concerns related to ongoing debates regarding the level of seismic risk and the response of surface process to active tectonics in the most rapidly extending region in the world. To approach this problem, an integrated scheme was followed that involves the study of late Quaternary stratigraphy, terraces, and ancient and modern civic structures in the Karacasu Graben located on the southern uplifted block of the Buyuk Menderes Graben. Our stratigraphic observations coupled with the existing micro-mammalian fossils demonstrate the widespread occurrence of terrestrial coarse red clastics (Karacasu Formation) before the appearance of the narrow-faulted corridor. The onset of high-angle normal faulting started with gradual denudation through the axial Dandalas Creek and its confluences southward while alluvial sedimentation remained active in the more southern areas of the Karacasu Graben. Ages from surface dating techniques (mainly OSL and cosmogenic radionuclides) show that previous knickpoints determined by the incision/accumulation threshold reached the vicinity of the antique Greek city of Aphrodisias, 30 km from the Buyuk Menderes Valley with a headward erosion rate of 75mky(-1) by the end of Last Glacial Maximum (LGM). Incision rates derived from terraces and Roman aqueducts in the middle and upper reaches of the basin increased from 1 mmy(-1) (background average geological rate for the last 65 ka) to 3 mmy(-1) in the last 2.3 ka, presumably due to increased population pressure in and around the vicinity of the city of Aphrodisias at the centre of the graben. Modern civic structures such as aqueducts and bridges constructed after the 1970's demonstrate the second wave of incision increased to as much as 10 mmy-1, likely due to increasing human pressure and the mechanisation of farming. On the other hand, inverse extrapolation of the knickpoint progression rate yields a surprisingly younger age of 400 ka for the birth of the new narrow tectonic corridor. This morphotectonic transformation exposed large depositional areas such as Karacasu and Bozdogan grabens to erosion and should have resulted in a significant increase in the sediment supply to BuyukMenderes River. However, seismic investigations in the Aegean Sea have yet to identify the sedimentary record of this tectonic transformation. (C) 2020 Elsevier B.V. All rights reserved.