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Geological Characteristics of Black Sea Basin: Inferences from New Black Sea Seismic Data

Abstract

The Black Sea consists of two sub-basins, the western and eastern Black Sea basins, which opened during the Early Cretaceous (West) and the late Cretaceous and Paleocene (East). The Black Sea is located in a zone where various tectonic blocks were involved in subduction, collision, and slab edge processes related to Neotethys Ocean. It is generally accepted that both basins were opened due to back-arc extension in the Eurasian continent associated with the subduction and eventual collision of the Pontides. The major structures thought to be involved in the opening of the western Black Sea basin include two sub-parallel approximately N-S striking transform faults, the West Black Sea and West Crimean faults, along which the Istanbul Block rifted from the Moesian Platform and drifted southwards, subsequently leading to the opening of the western Black Sea Basin. The newly acquired Black Sea-SPAN data support the established view that the western Black Sea fault exists off-shore Bulgaria and extends to the western boundary of Istanbul Block in the Thrace Basin (onshore). There is no evidence for the existence of the West Crimean fault on the Black Sea SPAN data though we do seem to see evidence for NE-directed subduction of western Black Sea crust below the mid-Black Sea highs and eastern Black Sea basin. The eastern Black Sea basin opened as the mid Black-Sea highs rifted off the Shatski ridge and rotated counter clockwise about a pole located somewhere in SE Ukraine. The Ordu and Trabzon transforms at the SE margin of the eastern Black Sea Basin were previously thought to be associated with the opening of the Eastern Black Sea Basin, and this seems to be confirmed by the Black Sea Span data. At the present day, small extensional faults are seen along the southern margin of the Black Sea and the western margin is also mainly dominated by extensional structures and gravity tectonics related to the Danube Delta. Except along its western margin, the eastern Black sea is dominated by an actively developing fold-thrust belts and piggy-back structures almost parallel to the coastline (Tuapse and Sorokin troughs). Compressional structures are generally thin-skinned and constrained to a narrow band close to shore line. No major recent compressional structures were observed in the deeper parts of basin, implying that Black Sea crust is stronger than the surrounding continental blocks and behaves as a rigid block constraining deformation along its margins.