Abstract
The Aegean plate is a complex geodynamic system characterized since Miocene by the interaction between the Hellenic trench retreat and the onset of the Anatolian extrusion. In Plio-Quaternary times, the deformation of the slab in the western part of the Aegean domain and the propagation toward the west of the North Anatolian Fault further complicate the system. The interactions between these phenomena and their deformations presents shadowy areas. There is, in particular, a large NE-SW fault system whose role and characteristics are not studied yet and that are not included in the Aegean geodynamic system. The PhD aims to understand the role of these NE-SW strike-slip faults in the Aegean tectonics since 15 Myr and, in particular, in the Evvia/Attica region. Multi-scale characterization of the deformation of this region was carried out through the acquisition of new field data, apatite fission-track ages, receiver functions, and 3D lithospheric numerical modeling of the deformation. These new field data characterize a dextral strike-slip kinematic on the NE-SW Pelagonian fault. It controls, together with NW-SE normal faults, the deposit of Miocene basins, suggesting a coeval activity of both normal and strike-slip faults during this period. We propose that the Pelagonian fault accommodates the block rotation in Miocene times. The strain inversion from slickenline data on faults indicates the compatibility of normal and strike-slip faults, associated with an extension evolving from N-S to NE-SW (during the rotation of blocks) and an E-W compression. During Plio-quaternary times, a change in stretching direction induces the formation of new E-W normal faults developing within the pre-existing NE-SW fault zones that became sinistral. These fault systems formed oblique rifts and are associated with a radial N-S extension incompatible with the NE-SW fault’s activity. We suppose that this change is due to the evolution of the west slab deformation. Apatite fission-track ages show a difference in ages of exhumation between Central Greece and the Cyclades. Thus, we suggest that the Pelagonian fault accommodates a differential extension during Miocene between the Cyclades and Central Greece, respectively strongly and poorly stretched at this period. Miocene low-temperature ages from NW-SE normal faults hanging-walls seems to confirm their activity in Miocene times, coeval with the strike-slip Pelagonian fault activity. Our new receiver function data also quantify a differential extension by characterizing a deeper Moho underneath Central Greece (26.5 km) than underneath the Cyclades (25 km) and Sporades (24.3 km). An analysis of the dip and the seismic signal perturbation suggests that the transition between Central Greece and the Cyclades occurs in a narrow zone, delimited by dextral NE-SW Pelagonian and South-Evvia faults. In between Central Greece and the Sporades, this Moho step is accommodated by a high-angle normal fault. Thus, the differential extension is laterally accommodated by these crustal faults as well as by the internal deformation of blocks they delimit. These new data point out the significance of strike-slip faults in the Aegean geodynamic since the Miocene. They accommodate the E-W shortening and define different blocks that rotate during the back-arc extension. Finally, our 3D models indicate that horizontal and orthogonal extension and compression at equivalent rates induce the formation of strike-slip faults within a hot continental lithosphere. These models suggest that the coeval activity of the extension due to the Hellenic trench retreat and the compression associated with the Anatolian extrusion can explain the formation of these strike-slips faults in Aegean.