Geometry and Tectonic Significance of Buyuk Menderes Detachment, in the Bascayir Area, Buyuk Menderes Graben, Western Turkey

Abstract

The main purpose of this thesis is to better understand the structural evolution of the Buyuk Menderes detachment surface, exposed along the southern margin of Buyuk Menderes graben, in western Turkey extended terrain .Approximately, 40 km2 area, in the Bascayir region where detachment surface is particularly well exposed, is mapped in detail during the summers of 2002 and 2003. Over 50 Rock samples were collected for petrographic and microstructural analysis. The Buyuk Menderes detachment shows typical characteristics of a low- angle detachment surface. Gneiss sequence and Early-Miocene age sedimentary rocks are the hangingwall rocks. Marble intercalated mylonitized schists are the footwall rocks of this detachment. In structurally lower levels fault rocks of Buyuk Menderes detachment grade into a ductilely deformed zone referred as the Buyuk Menderes shear zone. Deformation features in the shear zone range from ductile to brittle. Ductile features are S-C and S-C` asymmetric structures, schistosity, asymmetric mica fish, small-scale folds and asymmetric porphyroclasts. Continuous fractures and reidel shears define brittle deformation. Shear sense indicators suggest ductile top to the north structures were overprinted by ductile top to the south structures. These features were, in turn, overprinted by brittle top to the south kinematic indicators. These findings suggest that the Buyuk Menderes detachment may have developed in multiple stages.