Abstract: Structural
, Sequence
Stratigraphic
and Geodynamic
Modelling of the Western Black Sea: Early Mesozoic to
Recent
ROBB, NICHOLAS, Dept. of Earth Sciences, Keele University, Staffordshire, UK; STUART EGAN and GRAHAM WILLIAMS, Dept. of Earth Sciences, Keele University, Staffordshire, UK.
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