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The Cretaceous (Aptian-Cenomanian) Carbonates of the Parnassus Mt. (External Hellenides, Central Greece): An Outcrop Analogue of Rudist-Bearing Margin Deposits of the Mediterranean Region


The recent Zohr discovery made by Eni in the East Mediterranean has revitalised the exploration interest on carbonate themes of the Mediterranean Region. The available data show that the best reservoir interval is Cretaceous in age and it is characterized by the presence of rudists, coral fragments and molluscs (Bertello et al., 2016). The hydrocarbon potential and the facies distribution of Cretaceous reservoirs are frequently hard to predict in a reliable way through seismic data only, due to the complex porosity system usually characterizing carbonates and the resulting high reservoir heterogeneity associated with variable facies mosaics. This work illustrates the stratigraphic architecture and the depositional facies model of the Cretaceous (Aptian-Cenomanian) carbonates of the Parnassus Carbonate Platform (PCP), which may represent potential surface analogues of Cretaceous reservoirs of the Mediterranean Region, including those located on top of Zohr-type isolated carbonate platforms. The PCP is a large isolated carbonate platform unit that is presently sandwiched between the Pindos-Olonos Zone and the Sub-Pelagonian Zone. Its evolution as an isolated carbonate platform was initiated during the Late Jurassic. Between the end of the Early Cretaceous and the beginning of the Late Cretaceous, the central sector of the Parnassus platform emerged, and the depocentre was confined along the outer flanks of the platform, where rudist-bearing margin facies dominated. The Aptian-Cenomanian margin succession is particularly well exposed on the eastern platform margin. Here, the stratigraphic architectures and facies heterogeneities can be appreciated through the detailed mapping and clear stratigraphic and geometric relationships of the margin-to-basin transition. The Aptian- Cenomanian succession has been subdivided into five main superposed stratigraphic units, showing a dynamic depositional architecture defined by the stacking of prograding and retrograding geobodies. These are dominated by different rudist associations and variable amount of debris- and mud-dominated facies. The results of this study indicate that the margin architecture, the geometry of geobodies, the facies distribution and the amount of produced sediment depend mainly on the interplay between relative sea level changes and the rudist type (family, mineralogy and growth mode), their abundance and their association with other building organisms.