6533b828fe1ef96bd1288e67

RESEARCH PRODUCT

Miocene NNE-directed extensional unroofing in the Menderes Massif, southwestern Turkey

subject

description

Structural investigations in the central part of the Menderes Massif (Odemis-Kiraz submassif) reveal the presence of a large-scale, low-angle extensional shear zone with a top-to-the-N-NE shear sense. Regional ductile deformation was accompanied by the intrusion of two syntectonic granodiorites that have been dated with the Ar-40/Ar-39 method. One hornblende isochron age of 19.5 +/- 1.4 Ma and two biotite plateau ages of 13.1 +/- 0.2 and 12.2 +/- 0.4 Ma, respectively, constrain that extension was already active in the early Miocene. Successive tectonic denudation of the Odemis-Kiraz submassif resulted in the formation of a N-dipping detachment fault, in which ductile fabrics were severely reworked by cataclasis under decreasing temperature. Syntectonic Neogene sediments, currently exposed along the southern margin of the Gediz Graben, were deposited in the hanging wall of the extensional fault system and were tectonically emplaced onto the cataclasites during progressive exhumation. Minor rotation (<15 degrees) of the detachment fault to its present gentle dip of c. 15 degrees caused southward tilting of the sediments. Ongoing NNE-directed extension created a steep normal fault that truncates the detachment fault and constitutes the southern boundary fault of the Gediz Graben.