INTERACTIONS BETWEEN TECTONIC ACTIVITY AND EUSTATIC SEA-LEVEL CHANGES IN THE PINDOS AND MESOHELLENIC BASINS, NW GREECE: BASIN EVOLUTION AND HYDROCARBON POTENTIAL

P. Avramidis^*, A. Zelilidis^{* +}, I. Vakalas^* and N. Kontopoulos^*

^* University of Patras, Department of Geology, 26500 Patras, Greece.

⁺ author for correspondence: A.Zelilidis@upatras.gr

This paper investigates the sedimentological response of the Tertiary Pindos and Mesohellenic Basins to localized tectonic and eustatic sea-level changes in a submarine setting dominated by turbidite deposition. Five composite stratigraphic cross-sections were compiled from field data, three in the Pindos Basin and two in the Mesohellenic Basin; 45 samples were dated by means of nannofossil biostratigraphy. On the basis of these field studies, we relate observed changes in depositional environment to eustatic sea-level changes and to activity on local thrusts. Between the early Eocene and the late Miocene, tectonically-driven subsidence in both basins was generally more significant than eustatic variations in controlling depositional patterns. However, depositional conditions can be related to eustatic changes at four specific times:

1. late Eocene submarine fans and deltaic or fan-delta deposits in the Mesohellenic Basin can be related to a sea-level rise (NP17) and subsequent fall (NP18-19), respectively;
2. the development of submarine fans in both basins during the early to middle Oligocene (NP22-23) can be related to a sea-level rise;
3. a late Oligocene (NP24-25) sea-level fall can be related to more restricted depositional conditions, accompanied by intra-basinal thrusting in the Pindos Basin and the presence of two indentors in the Mesohellenic Basin;
4. a change from deep-water (submarine fan) to shallow-marine deposition during the late Miocene in the Mesohellenic Basin can be related to a eustatic fall in sea-level.

Standard organic geochemical analyses were carried out on 93 samples from both basins, including Rock-Eval pyrolysis and column and gas chromatography. Preliminary results indicate that the sedimentary sequences in both the Pindos and Mesohellenic Basins may have the potential to generate natural gas.

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