From syn- to post-orogenic Tertiary extension in the north Aegean region: Constraints on the kinematics in the eastern Rhodope–Thrace, Bulgaria–Greece and the Biga Peninsula, NW Turkey
N. Bonev, L. Beccaletto, 2007. "From syn- to post-orogenic Tertiary extension in the north Aegean region: Constraints on the kinematics in the eastern Rhodope–Thrace, Bulgaria–Greece and the Biga Peninsula, NW Turkey", The Geodynamics of the Aegean and Anatolia, T. Taymaz, Y. Yilmaz, Y. Dilek
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The Aegean region experienced back-are extension related to the Hellenic subduction system at least from the latest Oligocene to the present. We document Tertiary extension-related kinematics in the north Aegean, in the eastern Rhodope–Thrace of Bulgaria–Greece and the Biga Peninsula of NW Turkey. A regionally consistent NNE–SSW- to NE–SW-oriented kinematic direction, delineated in both areas by stretching lineations and associated ductile–brittle shear fabrics in exhumed metamorphic domes beneath detachments, suggests that they were kinematically coupled during the Tertiary extension. This kinematic framework, combined with regional geochronological data and the stratigraphic record in hanging-wall supradetachment basins, defines an extensional history that includes syn- and post-orogenic episodes from Paleocene to Miocene times. Paleocene–early Eocene synorogenic extension in the Kemer micaschists of the northern Biga Peninsula and in the Kesebir–Kardamos dome in Rhodope–Thrace accommodated gravitationally induced hinterland-directed exhumation of the orogenic stack, coeval with the closure of the Vardar Ocean. Then, following collision within the region, it was succeeded by latest Oligocene–Early Miocene extension as recorded in the Kazdaǧ Massif in the southern Biga Peninsula, which overlaps the Aegean back-arc post-orogenic extension, widely recognized in the central Aegean and southern Greek Rhodope. The protracted record of extension is interpreted to reflect progressive exhumation of the orogenic wedge along the Eurasian plate margin. Southward migration of extension and magmatism across the study areas accounts for sequential shift and roll-back of the subduction boundary at that margin, from the latest Cretaceous in the Rhodope to its present position at the Hellenic trench. The results allow recognition of the investigated areas as an important extensional domain in the north Aegean region, which underwent Tertiary syn- and post-orogenic extension.
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The complexity of plate interactions and associated crustal deformation in the Eastern Mediterranean region is reflected by the numerous destructive earthquakes that have occurred throughout its history. Many of these have been well documented and studied. In addition, the Aegean region provides examples of core-complex formation, synchronous basin evolution and subsequent graben formation and continental extensional deformation following orogenic contraction. It is therefore considered to be a perfect natural laboratory for the study of these mechanisms. The region has been the subject of intensive research for several decades. This book contains current results and ideas regarding the geodynamics of the Aegean and Anatolia. It will be essential reading for all geoscientists with an interest in the structural evolution of the Eastern Mediterranean.