*2.1. Tectonostratigraphic Evolution of Ionian Basin*

Western Greece is dominated by the external zones of the Hellenides fold-and-thrust belt, namely the pre-Apulian, Ionian and Gavrovo-Tripolis zones. At a regional scale (hundreds of kilometers), this Alpine belt records the initiation, development and final destruction of the southeastern margin of the Tethys Ocean and the consequent continent-continent collision between the Apulian and Pelagonia micro-continents to the east [34,58–63]. On a smaller scale (tens of kilometers), the various sub-basins of the Hellenic Tethyan margin have been inverted to produce the main Hellenic thrust sheets or folded zones [58,59,64]. The Ionian zone, which is bounded westwards by the Ionian thrust and eastwards by the Gavrovo thrust, extends from Albania to the north, forms most of the Epirus region and parts of the Ionian islands and continues southwards to central Greece, Crete and the Dodecanese. According to [65,66], the Ionian basin was subdivided into the internal, central and external Ionian sub-basins (Figure 1).

The tectonostratigraphic evolution of the Ionian zone is reflected on the deposition of three distinct sequences indicative of different tectonic regimes [34,58]: (1) a pre-rift sequence is represented by the Early Jurassic platform Pantokrator Limestones, which overly Early to Mid-Triassic evaporites through Foustapidima Limestones of Ladinian-Rhetian age, (2) a syn-rift sequence (Pliensbachian-Tithonian) deposited during extensional faulting and halokinesis of the Triassic evaporites, which caused the formation of the Ionian basin and its internal synrift differentiation into smaller sub-basins characterized by asymetric half-graben geometry and different carbonate thickness accumulation [42,58]. Complete Toarcian-Tithonian syn-rift pelagic sequences (Siniais and lateral equivalent Louros Limestones, Ammonitico Rosso or lower Posidonia beds, Limestone with filaments, Upper Posidonia beds) are located in the deeper part of the half-grabens, while unconformities interrupt these sequences in the rift shoulders, (3) a post-rift sequence (Early Cretaceous-Eocene) deposited after the cessation of extensional faulting, is defined by a synchronous throughout the basin Early Berriassian break-up, which is marked by an unconformity at the base of the pelagic Vigla Limestones. The Mesozoic to Eocene carbonate succession passes upwards to the flysch synorogenic sedimentation (siliciclastic turbidites), which began at the Eocene–Oligocene boundary and revealed progressively diminishing thicknesses from the internal to the external areas. Until the Early Miocene, the basin was filled with submarine fan deposits, in response to movement of Pindos thrust, compressional structures, deformation of the external Hellenides which migrated westwards, uplift of the entire Hellenides orogenic belt, and development of a foreland basin at the edge of the Apulian microcontinent [67–71].
