Tertiary and quaternary tectonics in Aegean area

Abstract

Abstract The Hellenic orogen is a composite one, consisting of three orogenic belts. 1 st the Cimmerian internal belt was created in pre-Late Jurassic times as the result of the northward drift of Cimmerian continental fragments from Gondwana towards Eurasia. 2 nd the Alpine orogenic belt was created in Cretaceous-Tertiary times after the Neotethyan subduction beneath the unique Cimmerian-Eurasian plate and the collision of the Apulia to the great plate. 3 rd the Mesogean orogenic belt along External Hellenic arc, due to the Mesogean-African underplate beneath the unique Alpine-Cimmerican-Eurasian plate in Miocene-Pliocene times and the exhumation of the Cretan-Southern Peloponesus tectonic windows. There is a clear deformation overprint of the Alpine deformation the Cimmerian belt and of the Mesogean one the Alpine belt. During Alpine and Mesogean orogenic processes in Tertiary a SW-ard migration of successive compressional and extensional tectonic events took place, producing nappe stacking and extensional exhumation of underplate rocks, successively in Rhodope (Eocene-Oligocene), Olympos-Ossa-Cyclades belt (Early Miocene) and Crete-Southern Peloponesus (Middle Miocene). Four deformation events based on numerous structural analysis and microscopic studies have been recognized in the broader Aegean region. The D1 extensional event in Late Eocene-Early Oligocene contemporaneous with the greenschist metamorphism, the D2 compressional event in Late Oligocene-Early Miocene contemporaneous with the 25 Ma HP/LT metamorphism in Crete and Southern Peloponesus, which produced the imbrication and the nappe stacking, the D3 extensional event in Early to Middle Miocene which produced low-angle shear zones, thinning of the crust, uplift and exhumation of the HP/LT metamorphic rocks as core-complexes and tectonic windows. The D4 tectonic event is the final deformation in Pliocene to recent times and it is the normal continuation of the extensional process in the broader Aegean region with brittle conditions, producing normal and strike-slip faults. In recent times the direction of the extension is generally N-S producing normal faults trending E-W and reactivated previous faults of other trends as strike-slip faults.