Abstract: Lithospheric Deformation and Basin Formation in the Black Sea Area: New Constraints from Basin Modelling

G. Spadini, A. Robinson, S. Cloetingh

Lithospheric deformation has a direct control on the formation of sedimentary basins and on their evolution trough time. The definition of the parameters controlling the large scale extension of a deforming plate, is needed in order to make any paleoreconstruction on subsidence, thermal history and kinematic evolution of a basin. Our modelling results suggest that there was a consistent and substantial difference in the nature of the lithosphere which rifted to form the Western Black Sea in the Middle Cretaceous and that which rifted to form the Eastern Black Sea in the Palaeocene. The Western Black Sea was initiated on cold, thick lithosphere (200 km), the Eastern Black Sea on a warm, thin lithosphere (80 km). Besides this difference in the implied lithospheric thickness the extension in the Western Black Sea appears to be controlled by a deep crustal level of necking (25 km) whereas in the Eastern Black Sea, the inferred level of necking is shallow (15 km). This controls the state of flexure of the deformed lithosphere and explains the differences in the gravity field over the studied area.

The Black Sea basin is a clear example of how important the knowledge of the lithospheric phenomena can be, even for surface processes. Our approach shed light on paleotectonic and paleogeographic reconstruction, location of subsiding areas and erosional surfaces. The modelling supports the existence of important thermo-mechanical differences between the Western and the Eastern Black Sea basin leading to distinct evolutionary paths: the western and the eastern portions are two distinct basins rather than parts of a unique one. The model reproduces and provides explanations for several features of the stratigraphy of the Black Sea: the apparent near absence of syn-rift strata (other than in the Western Pontides): thin to condensed early post-rift sequences in both basins; a thick Upper Eocene in the Eastern Black Sea: a relatively thin Oligocene to Miocene and very thick Quaternary. It also predicts the geometry and depth of the lake that developed in the centre of the Black Sea when sea level was lowered by 1500 m during the Late Miocene.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France