3.3.4. Extensional processes and block rotation

The Aegean-West-Anatolian region, characterized by a system of horsts and grabens, is one of the most rapidly deforming regions of the world. The NAFZ forms roughly the northern boundary of the deforming zone, the EAFZ its south-eastern boundary, whereas it’s southern and south-western boundaries are more diffuse and reach as far south as Crete and the Rhodes depression, and to the Hellenic and Pliny-Strabo trenches. The driving mechanism of this extensional regime is seen in the westward extrusion of Anatolia in response to persisting Arabia-Eurasia convergence, and in continuing subduction of the East-Mediterranean oceanic lithosphere, involving rapid SSW-ward propagation of the Hellenic arc.

TOPO-EUROPE aims at integrating detailed studies that have already been carried out on many of the extensional basins in the Aegean and West-Anatolian regions (e.g. Bozkurt et al., 2000), particularly in their on-shore parts, as well as the results of studies on the development of extensional core complexes (e.g. Jolivet and Patriat, 1999; Lips et al., 1999). Results of these studies, complemented by data from offshore basins, will be complied in an effort to define on a regional basis and in time and space the onset, progress and direction of crustal extension and of activity along associated shear systems. Where required, supplementary field studies will be carried out.

It is of particular interest that West-Anatolia provides evidence for an Early-Middle Miocene phase of E-W extension that was followed by Late Miocene and younger pulses of N-S extension, resulting in the superposition of interfering graben and horst structures. This suggests that a fundamental reorientation of the stress field and a corresponding change in the extensional driving mechanism had occurred (Yilmaz et al., 2000b). Whether an analogous sequence of events controlled the evolution of grabens in the offshore parts of the Aegean and the onshore parts of Greece needs to be assessed. Where available, access to industrial seismic and well data will be sought. Furthermore, paleo-stress analyses could contribute towards the recognition and definition of stress field changes.

Paleomagnetic studies carried out in the Western Aegean area, defining the timing and magnitude of major block rotations (Van Hinsbergen et al., 2005b), need to be extended into the Anatolian domain. It should be attempted to develop a step-wise palinspastic restoration of the Aegean-Anatolian region during its Oligocene to recent evolution.

Numerical and analogue modelling of the extensional history of the Aegean-Anatolian region, as developed during the planned compilation effort, will draw heavily on the results of lithospheric and mantle tomography, structural analyses and cross-sections, the distribution and focal depth and mechanisms of earthquakes and geodetic data.