Preliminary results of a thermal maturity modelling study as a tool for understanding a structural setting – the case of the Fold and Thrust Belt of Western Greece.

Abstract

<p>The Hellenides Fold and Thrust Belt (HFTB) is an arcuate shaped belt whose rocks were deposited in a series of platforms and basins that formed the southern rifted margin of the Apulian microcontinent. Despite a renew interest in the last years due to an international licensing round for the exploration and production of hydrocarbons in Greece, still little is published about its geometry, thermal maturity and hydrocarbon generation timing of the main source rocks hosted in the Mesozoic section. The External-most exposed part of the HFTB consists of the pre-Apulian and the Ionian geotectonic zones from West to East. Being part of the southern passive margin of Tethys from Triassic to Late Cretaceous, the Ionian zone represents a sedimentary basin which was differentiated from the adjacent platforms during the Jurassic rifting and consists of Triassic evaporites, Triassic-Eocene carbonates, and Oligocene-Early Miocene turbidites. The Pre-Apulian zone, as part of the slope of the Apulian platform to the Ionian basin, is made up of Triassic evaporites and up to Miocene carbonates. Organic rich layers are found across the Pre-Apulian and Ionian zones, and chiefly within Mesozoic. Present-day geometries have resulted from the mainly thin-skinned Miocene compressional deformation developed after the collision of the Apulian and Eurasian continental paleomargins. To understand the amount of overburden thickness across the chain, we performed Rock-Eval 6 pyrolysis, Gas Chromatography-Mass Spectrometry, MicroRaman spectroscopy and transmitted light petrography on Mesozoic-Cenozoic source rocks across an ENE-WSW transect in Western Greece where westward migrating intra-Ionian imbricate thrusts are evident. Overall, the data suggest that Cenozoic samples are immature, while Lower Cretaceous and Mid-Upper Jurassic thermal maturity reaches the onset of the oil window and further increases in Lower Jurassic and Triassic successions. Maturity data were used as input parameters to 1D thermal maturity modelling of wells and pseudo-wells across this transect. Model calibration by using present-day heat flow values and a Mesozoic rifting model, suggests that the eroded thickness at each studied location exceeds 1.5km. These erosion estimates better constrain our understanding of the geometry of the belt and the timing of maximum burial.</p>