GRAVITATIONAL OROGENIC COLLAPSE VS PLATE BOUNDARY STRESSES - A NUMERICAL MODELING APPROACH TO THE PERMO-CARBONIFEROUS EVOLUTION OF CENTRAL-EUROPE

A two-dimensional thermo-mechanical finite element model is used to st udy the Permo-Carboniferous evolution of Central Europe along a litho- sphere-scale transect from the Variscan Internides to the undeformed f oreland. The study concentrates on a quantitative evaluation of the pr ocesses controlling late-orogenic extension and destruction of the Var iscides, particularly the gravitational instability of thickened crust . Modelling results suggest that gravitational forces along cannot rep roduce the observed timing and amount of Permo-Carboniferous crustal t hinning. Tensile plate-boundary forces are required in addition to gra vitation to restore a crustal thickness of approximately 30 km in the Variscan Internides. Stresses as little as 10 MPa result in up to 28% extension and a good fit between observed data and model predictions. It is concluded that the Stephanian to Rotliegend evolution in the vic inity of the modelled traverse resulted not from gravitational forces inherited from Variscan crustal thickening, but was related to a chang e in orientation of the plate-boundary stresses at the end of the West phalian.