Lateral variations in lithosphere strength in the Romanian Carpathians: Constraints on basin evolution

Lithospheric strength profiles constructed through extrapolation of rock mechanics data and constrained by crustal geophysics data, demonstrate the existence of important spatial variations of thermomechanical properties in different domains of the Romanian Carpathians, the Pannonian basin and the Transylvanian depression. These models show important lateral variations in lithospheric rigidity along the Southern and Eastern Carpathian foreland, compatible with inferences from flexural modelling studies. The modelling predicts an absence of mantle strength and the presence of weak lithosphere in the Pannonian and Transylvanian basins. A NW-SE-trending rheological transect is presented, connecting 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 properties of the Romanian lithosphere with observed patterns in large-scale gravity anomalies and with tectonic units. A notable feature of the rheological models is the presence of an intra-Carpathian weak zone. The combination of a strong foreland lithosphere with a weak lithosphere 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 models indicate that the crustal lithosphere is detached from the mantle part of the lithosphere in the Carpathian foreland.