The Drübel is a ridge dominated by limestone beech forests with rocks up to 8 m high. The rocks consist of a gray limestone, the so-called Massenkalk. As a typical basin sediment, the mass limestone was deposited at the bottom of a shallow sea at the turn of the Middle Devonian and Upper Devonian periods (about 382 million years ago). The climate was warm and dry worldwide, which favored the formation of mighty coral reefs. A rich fossil fauna testifies to this time. The rocks in the Drübel Nature Reserve are composed 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 solution from carbonic acid naturally present in water. The resulting solution weathering leads to characteristic cavities such as crevices and caves. The process of this rock solution is called karstification. There are numerous caves around Brilon, but they are not freely accessible. Such a 12 m long cave can also be found in the nature reserve Drübel.
Age of the rocks: Mass limestone: Givet stage, Middle Devonian (about 382 million years before today).