Deep seismic reflection data from offshore western Greece: a new crustal model for the Ionian sea

Summarization: Contractional structures recognised in a recent SW-NE oriented seismic profile offshore western Greece, between the islands of Zakynthos and Kefallinia (Cephalonia), indicate that this part of the Pre-Apulian geotectonic zone was involved in Quaternary shortening related to the westward propagation of the Hellenic fold-and-thrust system. Deep reflector horizons including the Moho and the top of the crystalline basement were identified on the profile. Shallower reflectors include those corresponding to the contacts between the Mesozoic/Miocene, Upper Miocene/Lower Pliocene, and Pliocene/Pleistocene sedimentary sequences. The Upper Cenozoic to Quaternary sequence rests unconformably upon Mesozoic carbonates. Triassic evaporites wedge-out in the Paxos geotectonic zone, where the Palaeozoic passes up into Mesozoic deposits. We have identified contractional structures which were reactivated during the Plio-Quaternary on pre-existing high-angle normal faults, and which gave rise to significant topographic anomalies. West-dipping normal faults were also recognised both within the Palaeozoic and Cenozoic successions, and are related to regional extension during sedimentation. East-dipping thrust faults which root in the evaporites were also identified on the seismic profile. Due to right-lateral strike-slip activity on the Kefallinia Transform Fault, east-dipping normal faults were formed within the lonion abyssal plain. This abyssal plain together with the Hellenic Trench, an accretionary prism, and a forearc basin can be recognised on the seismic profile. A “triple junction” between the Apulian (African) Platform, the oceanic crust of the Ionian Abyssal Plain and the Eurasian Plate in the west of the line is related to the Kefallinia Transform Fault. Neotectonic structural deformation (i.e. Quaternary-Holocene) is superimposed on the above-mentioned structures. Finally, diapiric movement of Triassic evaporites has affected both the Alpine and the late Cenozoic to Holocene sedimentary sequences. Diapiric activity continues at the present day in the eastern part of the profile, in the lonian geotectonic zone. The forearc basin may be prospective for hydrocarbons. Target areas include the lonian channel where a play has already been located, and its extension to the south (the Kyparisiakos Gulf area). Here, thick late Cenozoic to Quaternary deposits may act as a top-seal above a reservoir consisting of eroded Mesozoic to Eocene carbonates, as at the recent Katakolon discovery.Presented on: Journal of Petroleum Geolog