EVOLUTION AND PETROLEUM POTENTIAL OF WESTERN GREECE

Abstract

This paper reviews previous data on the geological evolution of Western Greece, with special emphasis on the petroleum potential of the Pre‐Apulian zone (including new data) and the Ionian zone, the two most external portions of the Hellenide fold‐and‐thrust belt. From the Triassic to the Late Cretaceous, Western Greece constituted part of the southern passive margin of Tethys, and siliceous facies are widely associated with organic‐carbon rich deposits. Pelagic Late Jurassic units rich in marine organic matter constitute important hydrocarbon source rocks in the pelagic‐neritic Pre‐Apulian zone succession. Oil‐oil correlation with an Apulian zone oil sample (from Aquila, Italy) indicates similar geochemical characteristics. Thus, the significant volumes of oil generated by the rich and mature source rock intervals identified in the Pre‐Apulian zone are likewise expected to be of good quality. In the Ionian zone, four organic‐carbon rich intervals with hydrocarbon potential have been recorded.The tectonic history of the Pre‐Apulian zone, which is characterised by the presence of large anticlines, is favourable for the formation of structural traps. By contrast, locations suitable for the entrapment of hydrocarbons in the Ionian zone are restricted to small anticlines within largerscale synclinal structures. Hydrocarbon traps may potentially be present at the tectonic contacts between the Ionian zone and both the Pre‐Apulian and Gavrovo zones. Major traps may also have been formed between the pre‐evaporitic basement and the evaporite‐dominated units at the base of both the Pre‐Apulian and the Ionian zone successions. The degree of participation of the subevaporitic basement in the deformation of the Pre‐Apulian and Ionian sedimentary cover will determine the location and size of these traps.Various scenarios regarding the deformation of the sub‐evaporitic succession are examined in order to determine the hydrocarbon trapping possibilities of each model. The hypothesis of continental subduction (Early to Late Miocene) of the shared pre‐evaporitic basement of the Pre‐Apulian and Ionian zone eastwards of the Ionian zone is regarded favourably, as it appears to be compatible with the presence of a Phyllite ‐ Quartzite ‐ dominated (HP/LT) metamorphic unit beneath the Gavrovo‐Tripolis zone carbonates in Peloponnesus and Crete.