A trip through the Wildhorn Nappe from Cretaceous to Neogene time (Helvetic Nappes, Switzerland): Tectonic Studies Group of the Swiss Geological Society - Summer excursion, 2015

Abstract

A field trip across the Wildhorn Nappe (SW Switzerland), forming part of the Helvetic nappes, is presented here. The field trip, which took place on the 8-9th August 2015, was the annual excursion of the Tectonic Studies Group of the Swiss Geological Society. It has been organized as a 2-day itinerary along the southern slopes of the Helvetic Alps between Kanton Bern and Valais (Fig. 1). This guide contains a brief structural and stratigraphic overview followed by Stop descriptions along a main geological cross-section that, from south to north, shows both the Neogene and the Cretaceous faults and their different structural characteristics. Neogene faults are associated with veins and ductile to brittle structures. Cretaceous faults are comparatively dry, discrete and related to palaeo-escarpments associated with stratigraphic unconformities, fault-growth geometries, slumps and sedimentary dykes. The temporal evolution of the Cretaceous syn-sedimentary fault system is also documented by spectacular panoramas and briefly discussed in relation to nappe-stack development and subsequent Neogene orogen-parallel extension.