The Donnerkuhle quarry in Hagen is known for its long history of mining dolomitic limestone, which has been in operation since the beginning of the 20th century. This limestone comes from an extensive mass limestone deposit, which is characterized by a thickness of up to 600 meters and is around 370 million years old, from the Upper Middle Devonian period. Over time, the original limestone was partially transformed into dolomite stone through the action of water containing magnesium. This process of dolomitization makes the Donnerkuhle a unique raw material deposit in Germany.
The area surrounding the quarry is home to a rich geological heritage, including a reef body approximately 600 to 800 meters thick, formed around 370 million years ago in the Upper Middle Devonian. Over the course of its history, this reef body was partially dolomitized into dolomite stone and is overlain by mudstone in which fold patterns have developed locally. The formation of these reef structures occurred in a shallow marginal sea, making the area a fascinating study object for geologists and paleontologists. The rock formations there and the fossils they contain provide insights into the history of the earth and the evolution of life on our planet.
The quarry is also important for the local flora and fauna. Despite the interference with nature caused by the quarry operation, the area has proven to be a refuge for many animal and plant species. Particularly noteworthy here is the eagle owl, the largest owl in Europe, for which the steep rock faces of the quarry offer ideal breeding grounds. In addition, the lime-rich, poor raw soils contribute to the development of rare flowering plants and orchids, which in turn provide habitat for a variety of insect species. Reptiles, such as the smooth snake, also find a suitable habitat here.
The long-term planning for the area after the quarrying has ended includes the creation of an approximately 80 meter deep groundwater lake and the recultivation of the dump areas. These measures are intended to ensure that the area continues to be a valuable habitat for plants and animals in the future.