A tropical sea from the Devon era has left its mark on the landscape of the Soonwald Nahe Nature Reserve up to this day and age.
The quarzites formed from the sandy sea bed and slate from clayey sea deposits. That is why you can find evidence of tropical marine life, for example corals, in both materials.
Today the hard quarzites form the mountain crests of the Soonwald while the smooth slate rock often overlays the mountain sides. Even magmata rock, risen up from molten depths, mark many places in the Nature Reserve. For example the Rotenfels, the highest steep face north of the Alps, impressive proof of the landscape forming elemental forces of the region. Even giant saurians were at home here in the fern forest.