Fig. 1

Simplified geological cross sections across the Helvetic nappe system (a–c) and conceptual model of its evolution (e, f). The simplified tectonic map in d shows the location of the cross sections. a–c Cross sections across the Helvetic nappe system in Eastern, central and western Switzerland, respectively (after Pfiffner 1993; Herwegh and Pfiffner 2005; Escher et al. 1993, respectively). The Helvetic nappes are thrusted along a prominent basal shear zone (thick red line) over the Infra-Helvetic complex (b, c) and over Molasse and Flysch sediments (a). The cross sections are parallel to the displacement direction of the nappes. e Conceptual palinspastic reconstruction of the European margin in Western and Central Switzerland. f Conceptual model of nappe emplacement: sediments initially filling distal basins are displaced tens of kilometers over more proximal basement and sediment units while acquiring their typical nappe geometry (modified after Steck 1984; Bugnon 1986)