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

Abstract

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 with 40Ar/39Ar laser-probe experiments on two syn-kinematic white mica populations, which, respectively, predate and overprint documented Early Miocene deformational fabrics. Our results indicate that the regional extension had initiated by Eocene–Oligocene times. A 36±2 Ma 40Ar/39Ar age derived from white mica which formed during a regionally observed, northward-directed tectonic transport suggests that the extension was contemporaneous with the tectonic emplacement of mid-crustal continental basement. Alternatively, the age may relate to the regional cooling of the basement sequence, and thus postdates the tectonic emplacement. In the latter scenario, the analysis fails to solve the present ambiguity on the Pan-African or Alpine affinity of the northward-directed transport. Further exhumation of basement rocks is characterized by a dominant displacement along the north-dipping Gediz Detachment at the northern margin of the massif, which developed under ductile conditions in the Early Miocene by partial exploitation of older zones of weakness, which originated from an earlier phase of basement emplacement. Youngest (semi)ductile activity along the Gediz Detachment has been recorded as having a 7±1 Ma 40Ar/39Ar age derived from syn-kinematic white mica in the top of the detachment. Following the initiation of the ductile Gediz Detachment, an antithetic, semibrittle, and south-dipping Buyuk Menderes Detachment had developed in the center of the massif, which, together with the Gediz Detachment, accommodated further doming of the central part of the Menderes Massif and controlled the architecture of the surrounding supradetachment basins.