During the Late Triassic, the area now occupied by the Northern Calcareous Alps was instead a long, passive coastline at the western tip of the Neotethys Ocean.
The environment was initially dominated by a wide and shallow carbonate platform within a lagoon between the shore and a string of reefs.
This carbonate platform is nowadays preserved as the Carnian to Norian-age Hauptdolomit and Dachstein Formation.
The Kössen Formation represents a period of increased siliciclastic clay input into the lagoon, covering up the carbonate platform with marls and marly limestones instead of pure limestone or dolomite.
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