Zur Tal- und Reliefgeschichte des Churfirsten-Alvier-Gebietes (Kanton St. Gallen)
Abstract. The valley and relief history of the Churfirsten-Alvier ränge (Ct. St. Gallen):
Valley formation in the Churfirsten-Alvier range, between the Linth and Rhine rivers. began at the end of the Miocene with the tectonic history of the Helvetic nappes. In early stages. the Cretaceaous sequences became independent of their Jurassic substratums and these from their Verrucano-Tnassic basement. The valley of Lake Walenstadt in the south was initiated between this basement and north-moving younger sequences. The Thur valley, north of the Churfirsten range, which follows a syncline in the highest Helvetic nappe. was filled with early Tertiary Sediments and Pennine Flysch. The Valleys in the Alvier area are formed along synclmes and faults in the Cretaceous sequence; these structures dip towards the Rhme valley.
The Churfirsten range forms a limestone shield in the Helvetic nappe. It broke up foUowing ±N/S-onented joints. There inbetween, excavation of kars (cirques) began already during pre-Ouaternary glaciation; they are still intact at the ends of the ränge, but in the middle the kar-walls broke down along the steeper southern slope.
During the Mindel and Riss glaciations. no Rhine ice flowed through the saddles between the Churfirsten peaks into the Thur valley; however, this could have been possible in pre- Mindelian cold periods at high ice levels and still lower moun¬ tain relief.