MIOCENE SILICICLASTIC DEPOSITS OF NAXOS ISLAND: GEODYNAMIC AND ENVIRONMENTAL IMPLICATIONS FOR THE EVOLUTION OF THE SOUTHERN AEGEAN SEA (GREECE)

Early to mid-Miocene siliciclastic deposits on Naxos island in the southern Aegean Sea have been shed from an uplifting mountainous realm in the south, which included a patchwork of at least 4 litho-terrains of different thermal history. The petrography of conglomerate components suggests that the source rock units were mainly composed of a passive continental margin succession of external Pelagonian origin, and an oceanic succession mainly of deep water cherts and limestones deposited on basalt substratum, probably belonging to the Pindos realm. The passive continental margin contributed rounded zircon crystals of Early Cretaceous and broadly scattering Paleozoic fission track cooling ages. A distal assemblage of Paleogene shallow-water carbonates passing into flysch-like mixed calcarenitic and siliciclastic components with volcanic arc contribution is subordinatly present. Input from an upper greenschist to lower amphibolite facies Barrovian-type metamorphic source is restricted to a basin relic at the eastern extremity of Naxos. This basin relic also received higher contributions from the Paleogene volcanic arc and granitic slices with Early Cretaceous zircon FT cooling ages, as compared to the western basin relics. Components from the nearby metamorphic core complex are not present.

The depositional evolution of the basin relics reflects increasing relief in the source region and, in some parts of a fluvial succession, rhythmic channel deposition, possibly due to runoff variability forced by orbital cyclicity. Upsection, the depositional trend indicates increasing seasonality and decreasing humidity in the source region.

The Miocene deposits cover an ophiolite nappe, which was emplaced as an extensional allochthon during large-scale extension in the Aegean region on top of an exhuming metamorphic core complex, after latest Middle Miocene intrusion of a granodiorite body.