Akademik Veri Yönetim Sistemi
COLLISION AND COLLAPSE AT THE AFRICA-ARABIA-EURASIA SUBDUCTION ZONE, cilt.311, ss.321-342, 2009 (SCI-Expanded)
In western Turkey, the Alasehir and Buyuk Menderes grabens form east-west trending major tectonic structures. Their sedimentary fill is important for regional tectonic models for the late Cenozoic evolution of the Aegean region. These deposits are divided into four units dated between the early Miocene and Quaternary. We studied the magnetostratigraphy of two sections in the Alasehir graben and one in the Buyuk Menderes, partly covering the first and second sedimentary units. Detailed palaeomagnetic analysis allowed us to determine ChRM component for these rocks. The Zeytincayi river and road sections (Alasehir graben) record several polarity reversals, which are tentatively correlated to the interval C5Cn.3n-C5ADr (approximately between 14.6-16.6 Ma) of the ATNTS2004. This correlation is also supported by palaeontology and radiometric dating of syn-extensional intrusions. In the Eycelli section (Buyuk Menderes graben) only three polarity zones are recorded, and their tentative correlation with the interval of C5Bn.1r-C5Br (14.88-15.97 Ma) is in overall in agreement with the record of Eskihisar sporomorph association in this formation. These results place the initiation of the Alasehir and Buyuk Menderes grabens in the early Miocene. The palaeomagnetic declinations from the Alasehir graben indicate about 25 degrees anticlockwise rotation, whereas that of the Buyuk Menderes graben indicate a clockwise rotation of about 30-40 degrees. These contradictory vertical-axis rotations might be explained by detachment faults in the region. In Tertiary formations of western Turkey, contradictory block rotations are common and likely reflect thin-skinned deformation in the area rather than rigid crustal movements. Therefore, average anticlockwise rotations in western Turkey cannot be used as evidence for the model of back-arc spreading in the Aegean region.