In the upper Triassic period around 210 million years ago are the Kössen layers formed from sediments in a shallow sea that was hardly deeper than 50 m. The conditions were sometimes rather hostile to life, so that no large coral reefs could form. The conditions were sometimes rather hostile, so that no large coral reefs could form. Smaller coral reefs only developed in some places. Petrified corals can be found as white regular structures in the Kössen strata.
The rocks of the Kössen strata are very diverse. The dark marls are good source rocks for soil formation. Due to the high clay content, these stones are easily weathered, they do not form peaks but flowery alpine meadows. On the other hand, dark or light-coloured limestones may be intercalated, forming steep steps or rock faces.