Postcollisional contractional and extensional deformation in the Aegean region
Published:January 01, 2006
Sotirios Kokkalas, Paraskevas Xypolias, Ioannis Koukouvelas, Theodor Doutsos, 2006. "Postcollisional contractional and extensional deformation in the Aegean region", Postcollisional Tectonics and Magmatism in the Mediterranean Region and Asia, Yildirim Dilek, Spyros Pavlides
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In the Aegean area, distinct fault patterns with their associated stress regimes are evidenced along a curved convergent plate boundary. In this article, we analyze and review late collisional and extensional structures in five structural regions along the External Hellenides orogenic belt in order to define, primarily, the evolution of onshore basins and, secondarily, the evolution of off-shore basins and the role of the inherited structures within the present geotectonic framework. We also evaluate how these structures act on seismicity as well as present-day motion and magmatism in the Aegean area.
Northwestern Greece, which corresponds to our Region I, represents an area of active continental collision in which a previously overthickened crust collapsed mainly parallel to the structural grain of the orogen. At present, the most active structures in this region are the northwest-trending thrusts and the northeast-trending normal faults. Strong coupling and the transmission of horizontal forces from the collision front appear to explain the deformation within this region.
Central Greece (Region II) displays a mixed type of contractional-extensional deformation. Mesozoic inherited transverse structures are reactivated as WNW-trending faults and appear to accommodate most of the active north-south-trending present-day extension. Deformation in this area appears to be controlled both by rollback of the subducting slab and by the lateral extrusion of the Anatolia plate.
The areas that spread along the more curved parts of the Hellenic arc (Regions III and V) well emphasize the control exerted by pre-existing northeast-trending structures as well as their long-lived activity during the evolution of the arc. Present deformation within these regions possibly reflects the oblique convergence process, which is occurring in both areas in different degrees.
Finally, analysis of deformation patterns in the central part of the Hellenic arc and the Aegean Sea (Region IV) suggests that almost all pre-existing structures have remained active until the present and accommodate extensional deformation and rapid motion through a nonorthogonal fault system that crosscuts a thin and thermally weakened continental crust. Deformation north of our Region IV is accommodated primarily by the North Aegean trough. Basin-bounding faults within the North Aegean trough are dominantly characterized by apparently normal components as well as strike-slip components.
Plate boundary conditions, as well as pre-existing structures with a favorable orientation relative to the current crustal motion, control and variably affect the present-day deformation along the Hellenic arc and trench system.