Coexistence of thin- and thick-skinned tectonics in Zakynthos area (western Greece): Insights from seismic sections and regional seismicity

The structural style of the fold-and-thrust belt in the western part of the Hellenic foreland in an area offshore the Zakynthos Island is assessed on the basis of two lithoseismic profiles, earthquake data and field data in the broader area. The compressional deformation in the area is due to the late phases of subduction and collision between Aegean and African plates. Shortening is affecting a ~ 6–7 km thick sedimentary succession of Mesozoic carbonate rocks and evaporites, as well as Miocene to Pleistocene foredeep clastic deposits. Structures accommodating shortening in the Pre-Apulian and Ionian zones comprise a blind imbricate thrust system and fault-propagation folds that formed over a 10–11 km deep detachment. The thrust system comprises an array of forward-verging thrust faults, which sole out in a low-angle hinterland dipping décollement, separating the Mesozoic cover from the pre-Mesozoic basement. In this tectonic context, the Triassic evaporitic layers seem to play an important role in the vertical partitioning of the deformation style acting as either detachment horizons or lining the imbricate thrust surfaces. The concentration of recent seismic activity at a depth between 6 and 16 km implies that the pre-Mesozoic basement is also involved in the deformation in the form of upthrust basement slices, suggesting a combination of thick and thin-skinned deformation across this domain of the External Hellenides fold-and-thrust belt. The frontal part of the belt shows higher seismic activity along a low-angle blind thrust, as well as also in the areas where the individual thrust planes branch at depth to the basal décollement.

► Seismic sections offshore Zakynthos Island revealed a west-propagating thrust system.
► Evaporitic décollement causes vertical partitioning of deformation.
► Seismicity concentrates in the upper crust along low-angle thrusts.
► The Hellenic foreland involves interaction of thin and thick-skinned deformation.