Allgau limestone came into being over 150 million years ago in the depths of an ocean.
At that time an ocean arose between Europe and Africa, called the Tethys Ocean. Its shores were not very stable. Sometimes underwater mudflows carried material to the depths of the ocean.
The lighter layers are rich in limestone that was layed down in calm waters and over a long time.
The darker, clayey layers however, were deposited in a very short time - in a matter of hours. They would have resulted from an underwater landslide which would have churned up a lot of mud that later settled on the sea floor, forming a new layer.
These clayey limestones dominate the slopes of the Trupchun valley. Rocks rich in clay provide fertile ground, which in part explains the presence of large numbers of red deer and ibex in the Trupchun valley.