We examine a number of first-order features of Pannonian basin evolution
in terms of the feedback relation between passive far-field-induced
extension and active Raleigh Taylor instable upwelling of the
asthenosphere. We show that active mantle upwelling following a phase of
passive extension are viable mechanisms explaining the Pannonian basin
formation. The dynamic interplay between far-field-driven passive
extension and active thinning of the mantle lithosphere by convective
upwelling beneath the rift zone is modeled using thermomechanical finite
element methods. Our modeling results predict a first phase of passive
lithospheric thinning which is followed by a second phase of late
synrift to postrift active mantle lithosphere thinning due to
buoyancy-induced flow beneath the rift zone. We argue that the pattern
of coeval extension in the thinning region and compression in the
flanking regions may be explained by the buoyancy forces due to
lithosphere thinning. It is demonstrated that timescales of and stresses
generated by both processes are comparable. The model appears also to
explain the occurrence of late shallow mantle-related decompression
melts in the Pannonian region and late regional doming.