Tectonic significance of southward shear sense indicators in central and southern Menderes Massif, western Turkey

The Menderes massif of the Western Anatolia Extended Terrane in western Turkey contains four major extensional shear zones which are, from north to south, Simav, Alasehir, Buyuk Menderes and Kayabuku (Selimiye) shear zones. It has been well-established that the Simav of the northern Menderes Massif and Alasehir of the northern Margin of the Central Menderes massif contain only top to the north shear sense indicators. In recent years, we have conducted detailed structural analysis along the Buyuk Menderes shear zone of the southern margin of the central Menderes massif and the Kayabuku shear zones of the southern Menderes massif. The footwall of the Buyuk Menderes shear zone is made up of quartzite and marble intercalated micaschists. Its hangingwall contains the gneissic metamorphic rocks and the Early-Miocene sedimentary rocks, usually referred in the area as the Haskoy Formation. The footwall rocks contain both top to the North and top to the South shear sense indicators. The south-dipping Kayabuku shear zone of the southern Menderes massif also contains well-developed mesoscopic and microscopic shear sense indicators, and separates orthogneiss and augengneiss in its footwall from schist and marble rock units in its hanging wall. The shear zone contains two ductile sense of shearing; 1) top to the north and 2) top to the south. Our petrographic analysis of the shear sense indicators along the Buyuk Menderes and Kayabuku shear zones suggest that the top to north shear sense indicators are overprinted by top to the south shear sense indicators. This suggest to us that both the Buyuk Menderes and Kayabuku shear zones were developed in two stages.