LATERAL VARIATIONS IN LITHOSPHERE STRENGTH IN THE ROMANIAN CARPATHIANS - CONSTRAINTS ON BASIN EVOLUTION

Lithospheric strength profiles constructed through extrapolation of ro ck mechanics data and constrained by crustal geophysics data, demonstr ate the existence of important spatial variations of thermomechanical properties in different domains of the Romanian Carpathians, the Panno nian basin and the Transylvanian depression. These models show importa nt lateral variations in lithospheric rigidity along the Southern anti Eastern Carpathian foreland, compatible with inferences from flexural modelling studies. The modelling predicts an absence of mantle streng th and the presence of weak lithosphere in the Pannonian and Transylva nian basins. A NW-SE-trending rheological transect is presented, conne cting the Moesian platform, the Vrancea region of the Carpathians, the Transylvanian basin and the Apuseni Mountains with the Romanian part of the Pannonian basin. This transect demonstrates the existence of a close correlation of the inferred spatial variations in mechanical pro perties of the Romanian lithosphere with observed patterns in large-sc ale gravity anomalies and with tectonic units. A notable feature of th e rheological models is the presence of an intra-Carpathian weak zone. The combination of a strong foreland lithosphere with a weak lithosph ere in the inner part of the Carpathian/Transylvanian/Pannonian system sheds light on a number of key features observed in the evolution of sedimentary basins in these areas. Remarkable differences in rheology predictions between flexural models and depth-dependent rheology model s indicate that the crustal lithosphere is detached from the mantle pa rt of the lithosphere in the Carpathian foreland.