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 Apulian plate was subducted beneath the European plate during Late Cretaceous-Early Tertiary closure of Tethyan ocean basin(s). Carbonate rocks of the external Hellenides are exposed in the Mt. Olympos tectonic window, overthrust by several thin (approximately 0.2-4 km thick) thrust sheets of granitic basement derived from the internal Hellenides. Field mapping and structural data from the Mt. Olympos region reported here establish the geometry, kinematics and strain history of the continental basement before, during and after continental collision and subduction. Seven deformational events document the change from ductile conditions obtained at depth in the early stages of deformation, to lower 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 marked 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 phases (D1-D3) verges toward the foreland (southwest). Oppositely-directed D5-D7 extension occurred behind the active thrust belt during continued regional shortening. Normal faults have strongly modified the original thrust-related geometry in the Mt. Olympos region and elsewhere in the internal Hellenides.