STRUCTURE AND TECTONIC EVOLUTION OF THE WESTERN GEDIZ GRABEN AND THE GOLMARMARA BASIN, AEGEAN EXTENSIONAL PROVINCE, TURKEY

Extensional deformation in the Aegean region started in the late Oligocene–early Miocene and resulted in the formation of core complexes, supradetachment basins, and tectonic grabens. The main structural architecture is controlled by E-W-oriented normal fault systems and grabens, and NNE-striking oblique-slip cross faults accommodating differential extension and uplift. The Gediz graben (GG) within the central part of the Menderes core complex is one of the three major grabens in western Anatolia. My study area is in the western part of the GG where a crystalline basement high (Çaldag High) and a lacustrine depocenter (Gölmarmara basin) occupy the NW branch of the graben. The Çaldag High consists of Paleozoic metamorphic rocks, Cretaceous ophiolitic mélange units and Upper Miocene to Plio-Quaternary basinal strata, all of which are cut by WNW- and NNE-striking fault systems. The modern Gölmarmara playa lake east of the Çaldag High contains fluvial and lacustrine-palustrine sediments; its ancestral units (marl, clayey limestone, evaporites) are exposed in the footwall of a high-angle normal fault. Structural data analyses indicate that there is no evidence for a contractional phase during the extensional evolution in the late Miocene through early Pliocene in the Gediz Graben. Also, the NE branch of the Gediz Graben and the Gölmarmara Basin (a modern playa lake) are the youngest extensional structures within the broader Gediz Graben. The working hypothesis refers that the Caldag High represents an upper-plate extensional allochton (extensional raft) separated from the Central Menderes Massif to the south and propagated toward the north in time in an asymmetric fashion. In addition, exposed lacustrine limestones, which belong to paleo-lake Marmara, indicate that the paleo-lake formed synchronously with the extension in the region.