The purpose of the 1979 excursion of the Swiss Geological Society was to show the recent interpretations in several key areas on the cross section through the Alps of Western Switzerland. Several new results are published here for the first time in a preliminary way: for the Prealps, new data on the composition of the submediane zone (north-penninic mélange) in the Meiel area. -Description of the Middle Jurassic paleokarst of the Gummfluh (briançonnais paleogeographic domaine, nappe of the Préalpes médianes rigides).
-Progress report on the study of deformation, metamorphism and K-Ar ages along the Gummfluh thrust. Consequences for the cinematics of the préalpine nappes.