The Scandinavian Caledonides and their relationship to the Variscan belt

The main events that mark the contraction and extension histories of the Scandinavian Caledonides and the European Variscides are summarized. It is shown that continental subduction may have developed similarly large and asymmetric thrust systems in both orogens. However, while continent-continent collision developed in the Variscides, extension began in the Scandinavian Caledonides marking the end of continental subduction. This led extensional tectonics to affect two continental crusts with contrasting rheology and therefore led to contrasting extensional modes. We argue that plate divergence, responsible for extension in the Scandinavian Caledonides, was triggered by the Variscan collision between Laurasia and Gondwana. In contrast, horizontal buoyancy forces acting on a thermally softened thickened crust are more likely to have been responsible for extension in the Variscan belt.