CENOZOIC EXHUMATION AND SEDIMENTARY BASIN FORMATION IN THE MENDERES MASSIF, WESTERN TURKEY

New studies of the Menderes massif, western Turkey, improve our knowledge on the Cenozoic extension of Aegean region and contribute to understanding of the tectonic exhumation of mid-crustal rocks of the Tauride-Anatolide platform. Yet sedimentary basin formation in western Turkey during the exhumation of the Menderes massif provides important clues about the process; especially, lithological compositions of the boulder and cobble conglomerates indicate geological position of the source rock area. Basically, exhumation of the Menderes massif is controlled by normal faultings along the Datca-Kale main breakaway fault, Simav, Alasehir and Buyuk Menderes detachment faults. These faults juxtapose non-metamorphosed or metamorphosed from low-grade rocks to high-grade metamorphic and intrusive rocks.

The earlier period of crustal extension in western Turkey and exhumation of the Menderes massif have been handled by the Datca-Kale main breakaway fault and its northern continuation Simav detachment fault. In the hanging wall of the main breakaway fault, Oligocene Kale basin fill contains basal conglomerates originated mainly from rocks of the Lycian nappes. The upper sections of the basin fill, however, include fragments of the metamorphites (mainly marble) from Menderes massif. The footwall of the Simav detachment fault consists of high- and medium-grade meta-sedimentary and meta-igneous rocks (e.g. paragneiss, orthogneiss, schist, amphibolite, quartzite and marble) and granitoids with variably mylonitic and cataclastic in nature. Top-to-the N-NE shear sense indicators in the Datca-Kale main breakaway fault and Simav detachment fault suggest that exhumation of the Menderes core complex was initiated as an asymmetric core complex. Furthermore, this indicates that the Menderes massif was exhumed to be a source rock area for Kale basin during Oligocene.

Normal faulting would follow in the Early Miocene. Opposite-dipping two detachment faults, named the Alasehir and the Buyuk Menderes detachments, led to further uplifting the core complex and contributing to exhumation of the central Menderes massif and forming of approximately E-W-trending half-grabens. Early Miocene deposits of these half-grabens and coeval N-trending basins include boulders and cobbles with mylonitic textures representing rocks of the core complex. This shows that the Menderes massif has already been exhumed along Datca-Kale Main breakaway fault and Simav detachment fault and reached up to the erosion level. Post-Miocene basins, therefore, can not be related to the first exhumation stage, even if some of them are located on the corrugations of the Simav detachment.