Station 12 Geologiepfad Malbun: Die Schichtfolge der Trias

The north face from the rocks below Alp Turna up to the summit of the Augstenberg shows the sequence of all the rock layers of the Triassic period that occur in the Malbun. Here they lie on top of each other in the order in which they were deposited in the sea. Below are the oldest layers, above the youngest. Depending on the type of rock, the layers weather differently. Limestone shows up in steep rock faces. Clayey rocks, such as marl and slate, weather into gently sloping meadows. Dolomite is formed by steep walls similar to limestone, but with abundant scree slopes.

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Different deposits due to different environmental conditions

Why were such different rocks formed in one and the same sea? The lowest limestones were deposited 240 million years ago. The dolomite of the summit was deposited about 200 million years ago. From our location to the summit, we overlook 40 million years of continuous rock deposit. During this long time, the water depth and the climate have changed. The limestone at the bottom and the shale clays above it were formed in deeper water than the limestones further up and the gypsum and dolomites above. In general, the north face shows a development from a deeper to a less deep sea and an increasing influence of evaporation. The seabed slowly rose and the climate became warmer and drier.