EARLY CRETACEOUS SEDIMENTATION AND OROGENY ON THE SOUTHERN ACTIVE MARGIN OF EURASIA: CENTRAL PONTIDES, TURKEY

The Pontides in northern Turkey constituted part of the southern active margin of Eurasian continent during the Mesozoic. In the Early Cretaceous, a large submarine turbidite fan, measuring 300 km by 60 km, covered most of the Central Pontides. New U-Pb detrital zircon data show that the major source of the turbidites was the East European Craton in the north. A large river, comparable to the present Nile, was draining the East European Craton south to the Tethyan Ocean. This implies that there was no Black Sea rift between the Pontides and the East European Craton during the Early Cretaceous. The Lower Cretaceous turbidites are bounded in the south by a large metamorphic area, the Central Pontide Supercomplex, which was considered as a pre-Jurassic basement. New geological mapping, petrology, U-Pb zircon and Ar-Ar muscovite ages indicate that the northern part of the Central Pontide Supercomplex consists of Lower Cretaceous distal turbidites deformed, metamorphosed and accreted in the north-dipping subduction zone in the Albian. The rest of the Central Pontide Supercomplex is made of Middle Jurassic, Lower Cretaceous and middle Cretaceous (Albian) metamorphic belts, each constituting distinct subduction-accretion units. They represent episodes of collision of oceanic volcanic arcs and oceanic plateaus with the Eurasian margin.