Temporal constraints on the kinematics of the destabilization of an orogen : syn- to post-orogenic extensional collapse of the Northern Aegean region

Abstract

The Mediterranean region is situated at the interface of the African and Eurasian plates and has been shaped by the Alpine Orogeny and the subsequent post-orogenic extension during the convergence and collision of the African and Eurasian plates. Numerous tectonic studies have focussed on the role ofthe African - Eurasian interaction and its effect on the development of the Mediterranean region. One of the prime areas where this interaction has been investigated is the Aegean region in the Eastern Mediterranean. The study which is reported in this thesis has investigated the tectonic development ofthe ductile Aegean crust which was involved in the Alpine Orogeny and in its post-orogenic history. The aims of this thesis are to obtain a detailed record of the Alpine kinematic history in the Pelagonian Zone in the northern Aegean region, focussing on the timing of, and the interaction between, compressional and extensional tectonics and on their effect on the development of the Aegean region and to temporally constrain the correlation between the Alpine Orogeny and the post-orogenic extension. The study will help to understand the geodynamic controls of the extensional processes that have characterized the development of the Aegean orogenic wedge. The aims have been achieved by combined field, microstructural and 4°Ar/39Ar laserprobes studies of terrains of exposed Aegean basement, which have been metamorphosed and ductily deformed during the Alpine Orogeny. The research has mainly focussed on the Pelagonian Zone in the northwestern Aegean with additional field based studies in the Rhodope Zone (northern Aegean) and Kazdag and Menderes Massifs (eastern Aegean). The field based studies and 4°Ar/39Ar laserprobe dating of deformational fabrics from selected samples have resulted in temporal constraints on the deformational and kinematic events which affected the basement, when it was still positioned at ductile levels within the crust. The wealth of published data from the Cyclades area and from Crete, in the central and southern Aegean respectively, has been integrated with the results from this study to characterize the Alpine tectonic development of the Aegean region, as a whole.