Fig. 2

Main route of the Valais glacier and possible transfluence passes across the Bernese Alps. Facies zones of Alpine metamorphism in the western Swiss Alps are coloured (facies zones according to Stampfli 2001): no colour indicates the area of very low-grade Alpine metamorphism. The facies zones evidence an increase in temperature from north to south. In the nappes north of the greenschist facies zone metamorphism reached uppermost anchizonal conditions (less than 300 °C). Only rocks in the catchment area of the Rhône river and its southern tributaries experienced more than 300 °C