GEOMETRY AND KINEMATICS OF CONTINENTAL BASEMENT DEFORMATION DURING THE ALPINE OROGENY, MT OLYMPOS REGION, GREECE

In the Hellenic Alps, continental crust of the leading edge of the Apu lian plate was subducted beneath the European plate during Late Cretac eous-Early Tertiary closure of Tethyan ocean basin(s). Carbonate rocks of the external Hellenides are exposed in the Mt. Olympos tectonic wi ndow, overthrust by several thin (approximately 0.2-4 km thick) thrust sheets of granitic basement derived from the internal Hellenides. Fie ld mapping and structural data from the Mt. Olympos region reported he re establish the geometry, kinematics and strain history of the contin ental basement before, during and after continental collision and subd uction. Seven deformational events document the change from ductile co nditions obtained at depth in the early stages of deformation, to lowe r temperature ductile and semi-ductile shortening-related fabrics, to brittle extensional features related to exhumation of the metamorphic rocks. DI-D4 occurred during subduction of basement nappes and are mar ked by thrust faulting and folding under blueschist facies conditions; D5-D7 are related to unroofing of blueschist facies metamorphic rocks and are associated with extension. Each of the major shortening phase s (D1-D3) verges toward the foreland (southwest). Oppositely-directed D5-D7 extension occurred behind the active thrust belt during continue d regional shortening. Normal faults have strongly modified the origin al thrust-related geometry in the Mt. Olympos region and elsewhere in the internal Hellenides.