## 2 Geological Setting
According to the existing models, the Ionian zone consists of three distinct stratigraphic sequences [71,72] (Figure 3): (a) a pre-rift sequence (Triassic--Early Jurassic) represented by a thick evaporitic succession overlain by shallow marine carbonates; (b) a syn-rift sequence (Early to Late Jurassic) where the basin was compartmentalized and a half-graphen geometry  
was favored, reflected in variations in sediment type (pelagic carbonates and deep water clastics) and thickness. During this stage, the evaporites started to mobilize, initiating the formation of diapirs [72]; (c) A post-rift sequence (Early Cretaceous to Eocene) marked by the deposition of pelagic limestones. However, new insights into the evolutionary structural model of the Ionian fold-and-thrust belt in central-south Albania and western Greece came to light recently, taking into account the significant amount of new seismic and fieldwork data acquired over the last decade in the context of oil and gas exploration. According to these data, various researchers [82; 83; 84] proposed an alternative model, placing the rifting stage earlier in the Triassic and presenting the clear influence of salt tectonics since the Early Jurassic. The pre-rift sequence comprises shallow water carbonates that overlie thick evaporitic deposits (\(\sim\)2000 m). Dissolution breccia overlain by dark-colored limestones (Foustapidima formation) mark the transition from the evaporitic succession to platform carbonates. The syn-rift sequence initiates with pelagic and hemipelagic limestones of the Pliensbachian age (Sinais and Louros formations). The transition from shallow marine to hemipelagic and pelagic formations is indicative of the gradual deepening of the basin. Carbonates and siliciclastics are deposited in the specific stage, characterized by lateral variations in thickness. These variations portray both the extensional tectonic regime and the mobilization of the underlying evaporites, which resulted in the segmentation of the basin into smaller sub-basins presenting a half-graben geometry [72]. The post-rift sequence is marked by pelagic limestones (Vigla limestones) which have been deposited across the whole extent of the Ionian basin. Small-scale differentiations in Vigla formation thickness suggest that halokinetic events were still active [69]. Vigla limestones are overlain by calciturbiditic limestones (Senonian Limestones). According to [85], the Ionian Basin at that time was characterized by a central shallower part, surrounded by slopes that displayed higher sedimentation rates. The Apulian and Gavrovo platforms acted as sources of carbonate clastic material, which was deposited in the Ionian basin via gravity flow processes (debris flows and turbidity currents). During the Eocene time, clastic material supply was reduced and pelagic limestones that resemble those of Vigla formation were deposited. The basic difference between the two pelagic facies is the absence of the extensive chert layers that occur in Vigla limestones. In the early to middle Eocene, carbonate sedimentation was followed by a gradual passage to clastic sedimentation, expressed by thick submarine fan deposits [67]. The transition was marked by a zone of calcareous marls, reaching a maximum thickness of 40-50 m [67]. At this stage, the basin was transformed into a typical foreland setting [67; 70; 86; 87; 88; 89] with a major bounding thrust towards the east (Findos Thrust). Inversion tectonics resulted in the re-activation of Jurassic extensional structural elements. Reverse or strike-slip faults indicate the change in the tectonic regime to a compressional configuration. As a result, minor thrusts divide the Ionian zone into the internal, middle and external Ionian zone (from east to west) [85]. A major orogenic phase occurred at the end of the early Miocene [85]. The age of Pindos foreland sediments is still a matter of debate.