Preliminary petrographic data on the Early Cretaceous Boeothian flysch (External Hellenides, central Greece); provenance and palaeogeographic implications

This paper defines the petrographic features of the Boeothian Flysch, an Early Cretaceous turbiditic deposit, which marks the boundary between the External/Internal Hellenides in central-southern Greece (south of the Kopais plain). The results from this study represent a preliminary contribution in reconstructing the Early Cretaceous palaeogeography of a limited segment of the Alpine Tethys (i.e. the Pindos Ocean), mainly supported by provenance changes of the detrital modes of arenites and related tectonic events. The Boeothian Flysch, whose stratigraphic succession is made up of basal conglomerates grading upwards to sandstones and pelites, interlayered with calpionellid micrite limestones, is here supposed to belong to the Early Cretaceous flysch family, cropping out along all the western and central Europe Alpine Chains for more than 7,000 km, from the Gibraltar Arc to the Balkans. This flysch commonly marks the contact between the internal and external areas and usually shows a provenance linked to internal areas, mainly made up of crystalline sources and, locally, by ophiolitic complexes. Representative samples of sandstones were analyzed for petrographic compositions in order to detect the source areas. The data obtained suggest that the provenance of the Boeothian Flysch is closely related to sediment sources belonging to internal domains and formed by a Jurassic carbonate platform and metamorphic basements, connected to the Pelagonian Terranes (Auct.), and by ophiolitic complexes. Thus, it is also possible to hypothesize that Early Cretaceous uplift and rejuvenation processes affected these internal domains with the production of a detrital supply, filling the innermost sector of the Pindos Ocean, whose external margin was bounded by the Parnassos microcontinent. This uplift process may probably represent the beginning of the Late Cretaceous tectogenesis, widely recorded in almost all the central-western Alpine Tethys.