Summary

An integrated geological and geodynamic study of the western Black Sea has been developed using outcrop and marine seismic data. Techniques used within this study include seismic interpretation and well log analysis, burial history modelling, sequence stratigraphy, structural section restoration and numeric tectonic modelling. Case studies over the Bulgarian, Ukrainian and Turkish Black Sea regions all provide detailed information of the processes involved in the structural and stratigraphic evolution of the western Black Sea since the early Mesozoic.

Detailed seismic interpretation reveals that compression within the Balkanides (Hauterivian to middle Oligocene), Crimea (Senonian to base Miocene) and the Pontides (Senonian to middle Oligocene) gave rise to varying structural styles. The Balkanides exhibit a complex interplay of Cretaceous inversion with subsequent thin skinned compression that shows hinterland migration during the upper Eocene and Oligocene. This compression has also reactivated basement faults within the Moesian Platform foreland to the northeast, during the Eocene. The platform was previously considered to be tectonically inactive throughout the Tertiary. The Northwestern Shelf of the Ukrainian Black Sea shows separate late Cretaceous-base Neogene phases of inversion of middle Cretaceous extensional faults. Compression over the offshore Turkish Pontides produced a small Palaeogene foreland basin that was subsequently buried beneath the Neogene fill of the Black Sea basin.

Sequence stratigraphic analysis of the Neogene sedimentary fill has identified 8 seismic sequences around the margins of the western Black Sea. A major sequence boundary exists within the Messinian stage (late Miocene) that may correspond to the well established massive sea level fall in the Mediterranean at this time. Sea level curves constructed from this sequence stratigraphic interpretation do not match previous sea level curves for the Black Sea but are similar to global schemes.

The results of lithospheric modelling suggest that simple Albian-Aptian extension (Beta value slightly >1) within the western Black Sea basin does not account for the massive Tertiary sedimentary fill (15 km) observed on seismic data. Increased sediment loading and flexural adjustments accounts for some of the subsidence, but other processes such as compression at the margins, enhanced extension in the mantle and phase changes in the lower crust have been tested as possible explanations for the observed sediment thicknesses within the basin.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah