Geochemical investigation of the Upper Miocene-Lower Pliocene deposits in northern Corfu

Abstract

Upper Miocene to Lower Pliocene sediments in the NW margin of the Hellenic Fold and Thrust Belt in Corfu have been studied in terms of their geochemical characteristics. More than 50 samples were analysed using Rock Eval IV pyrolysis, and bitumen extraction, open column chromatography and gas chromatography-mass spectrometry was performed for selected samples in respect of their TOC content, thermal maturity and type of organic matter. Results of this investigation indicated units with sufficient organic material of good enough quality and quantity to be considered as potential source rocks. TOC values range from 0,1 up to ~4%, while 25% of the samples present TOC above the 0,5% threshold. A general Type III kerogen was identified, indicating organic matter of terrestrial origin, but also Type II kerogen was identified for a fair number of samples. The general trend of the results presents mainly gas prone and some mixed oil/gas prone samples. Tmax and Production Index values further indicate that the most promising parts of the succession are immature with respect to oil generation and have not experienced high temperature during burial. N-alkane distribution of the samples present dominance of the long-chain components. Immaturity of the kerogen is also evident by low Pr/Ph and 20S/(20S+20R) ratios. The terrigenous to aquatic ratio (TAR) is fairly higher in the Miocene compared to the Pliocene samples. Factor analysis of the RE IV data was integrated in this study in order to provide another important tool in analyzing and interpreting geochemical data in respect of hydrocarbon exploration. Three general groups of source rocks are identified, in respect of their potential: A poor to fair group in the Pliocene sediments, a fair group mainly in the Miocene sediments and a fair to good group in both Miocene and Pliocene samples. The study area is part of an ongoing and crucial investigation of hydrocarbon prospectivity in Western Greece, and the present study focuses on providing further insights in the understanding of a complex but promising region, in the southern edge of the Dinarides-Albanides-Hellenides continental convergent zone. Corfu lies in geotectonically complex area of collision, subduction and transform faulting activity and is mainly controlled by the collision and continued convergence of the African and Eurasian plates since the Mesozoic. The most important structural control of the broad area is contractual deformation, as suggested by the constant occurrence of evaporites throughout the thrust boundary between the Pre-Apulian and the Ionian Zone, the Ionian Thrust, a crustal-scale thrust fault which pushes the lower stratigraphic Ionian Zone over the Pre-Apulian. The Ionian Thrust and the South Salento-North Corfu transfer fault systems control the evolution of the sedimentary basin of the study area.

AAPG Datapages/Search and Discovery Article #90325 © 2018 AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin, Lisbon, Portugal, May 2-3, 2018