Structural Development of Western Greece

Abstract

The study area comprises the province of Aitoloakarnania and associated islands in western Greece, and lies within the western sector of the Hellenide geosynclinal belt. It includes the miogeosyncline and western foreland. The sedimentary sequence consists of Permo-Triassic evaporites, a predominantly carbonate section of Late Triassic to Eocene age, and Mio-Pliocene terrigenous clastics, including a thick section of lower Miocene flysch. Sedimentation within the miogeosyncline occurred in two distinct depositional environments--a western mobile trough which underwent five cycles of subsidence, uplift, and erosion, and an eastern shelf on which deposition occurred at a shallow depth prior to marked subsidence in Miocene time. The foreland on the west remained as a shelf throughout the depositional period. The regional structural trend is NNW-SSE, parallel with the depositional belt. Thrust faulting dominates the structural pattern and reflects transverse compression of the geosyncline. The eugeosynclinal sequence continues westward across the miogeanticlinal ridge in central Greece, on a low-angle dislocation which is interpreted as the sole fault of a major gravitational slide. Orogenic deformation of the miogeosyncline commenced during the early Miocene and failure occurred along thrust faults which, in the mobile trough, flatten at depth to form a decollement at the contact with the evaporites. However, the westerly dipping glide planes required for gravity sliding cannot be reconstructed, and the faults are considered to extend into basement. Continued compression and uplift caused complex faulting and folding within the thrust sheets and above an incompetent substratum. Evaporites crop out in a fault-controlled intrusive belt about 70 km in length along the western margin of the flysch trough and are ascribed to halotectonic breakthrough initiated during the early stages of thrusting. Structural trend directions in the western part of Aitoloakarnania and the offshore islands vary abruptly and are interpreted as a dextrally coupled orocline, possibly with minor diapirism.