Multistage exhumation of the Menderes Massif, western Anatolia (Turkey)

Structural analyses along selected transects across the Menderes Massif and incorporation of existing data have resulted in a synthetic cross section across southwestern Turkey. The tectonic interpretation has been combined w ith Ar-40/Ar-39 laser-probe experiments on two syn-kinematic white mica pop ulations, which, respectively, predate and overprint documented Early Mioce ne deformational fabrics. Our results indicate that the regional extension had initiated by Eocene-Oligocene times. A 36 +/-2 Ma Ar-40/Ar-39 age deriv ed from white mica which formed during a regionally observed, northward-dir ected tectonic transport suggests that the extension was contemporaneous wi th the tectonic emplacement of mid-crustal continental basement. Alternativ ely, the age may relate to the regional cooling of the basement sequence, a nd thus postdates the tectonic emplacement, In the latter scenario, the ana lysis fails to solve the present ambiguity on the Pan-African or Alpine aff inity of the northward-directed transport. Further exhumation of basement r ocks is characterized by a dominant displacement along the north-dipping Ge diz Detachment at the northern margin of the massif, which developed under ductile conditions in the Early Miocene by partial exploitation of older zo nes of weakness, which originated from an earlier phase of basement emplace ment. Youngest (semi)ductile activity along the Gediz Detachment has been r ecorded as having a 7 +/-1 Ma Ar-40/Ar-39 age derived from syn-kinematic wh ite mica in the top of the detachment. Following the initiation of the duct ile Gediz Detachment, an antithetic, semibrittle, and south-dipping Buyuk M enderes Detachment had developed in the center of the massif, which, togeth er with the Gediz Detachment, accommodated further doming of the central pa rt of the Menderes Massif and controlled the architecture of the surroundin g supradetachment basins.