The Drübel is a mountain ridge dominated by limestone beech forests with rocks up to 8 m high. The rocks consist of a gray limestone, the so-called mass limestone. As a typical basin sediment, the mass limestone was deposited at the bottom of a shallow sea at the Wenden of the Middle Devonian and Upper Devonian periods (around 382 million years ago). The climate was warm and dry worldwide, which favored the formation of mighty coral reefs. A rich fossil fauna bears witness to this period. The rock in the Drübel nature reserve is made up of calcareous skeletons of reef dwellers such as corals and stromatopores (sponge-like animals). If you look closely, you can even see fossil remains in the limestone with the naked eye.
Limestone is very sensitive to carbonic acid naturally contained in water. The resulting solution weathering leads to characteristic cavities such as fissures and caves. The process of this rock dissolution is called karstification. There are numerous caves around Brilon, although they are not freely accessible. One such 12 m long cave can also be found in the Drübel nature reserve.
Age of the rocks: Mass limestone: Givet stage, Middle Devonian (around 382 million years before today)