Zur plio-pleistozänen Entwicklung der Bären- und Karlshöhle bei Erpfingen (Schwäbische Alb) unter Berücksichtigung der Sinterchronologie

Wolfgang Ufrecht, Thekla Abel & Christof Harlacher


The Bären- and Karlshöhle (bear and Karl's cave) near the town of Erpfingen is one of the best-known caves of the Swabian Alb. Apart from its rich sinter decoration and bone deposits of Late Pleistocene cave bears, the cave also receives scientifical attention for its sediments containing iron ore concretions (Bohnerze, bean iron ore) and fossils of an earliest pleistocene mammal fauna, which contribute to the discussion on landscape and karstification development of the Kuppenalb, the hilly landscape that stretches along the northern part of the Swabian Alb.

The cave sediments and their fossil contents as well as the numerous sinter generations that are partly interbedded with the sediments allow the reconstruction of an eventful history of the Bären- and Karlshöhle. The development initiated in the Late Tertiary and continued well into the Middle Pleistocene. The phreatic phase of the cave is closely related to the fluvial history of the river Lauchert. It is possible to correlate the cave with a terrace level that corresponds to the first stagnation phase of the Urdonau (predecessor of todays river Danube) after the starting entrenchment of its V-shaped valley. This morphological position is comparable to those of other large cave systems of the central Swabian Alb. It confirms the close relationship between the incision history of the Danube and the deep karstification of the Upper Jurassic limestones of the Swabian Alb.

The age of the active river cave stadium of the Bären- and Karlshöhle can be determined by a fossilbearing sediment deposited in a small cavern next to the modern cave entrance (the so-called Urhöhle). Molluscs above the cave floor are of eopleistocene age (Tegelen). The fossil mammal fauna in the Bohnerz sediments (in the border layer Grenzhorizont) verify the sedimentation in and the sealing of the cave with weathered material at the beginning of lower pleistocene (Eburon). Other cavities and caves at similar altitudes as the Bären- and Karlshöhle have also been completely or partly filled with these Bohnerz sediments and thus imply a more widespread sealing of karst cavities. The beavers Trogontherium, Castor and also some species of the fossil mammal fauna show a high affinity to running water and verify the existence of superficial waterbodies in their habitat up to the beginning of lower pleistocene.

The mapping of the cave contents relies especially on these sediments that occur together with sinter formations. Uranium-thorium dating of these sinter secure ages for a stratigraphic structuring of the profiles and thus help reconstructing the accumulation and erosion events over the time. A flowstone, which overlayed the Bohnerz sediments, gives with ages of 444.000 (+80.200/ -46.200) and 474.000 (+33.900/-26.100) years respectively (oxygen isotope stages 12 and 13) a minimum date for the sealing and a maximum date for the following erosion. A 200.000 (± 18.000 ) year old flowstone (oxygen isotope stage 7), which is underlain by Bohnerz sediment and covered by a reddish brown clay without iron ore concretions, indicate sedimentation processes well into the Middle Pleistocene. These uranium-thorium ages were determined by thermo ionisation mass spectrometry (TIMS). In the narrow passage between the Karls- and the bear cave further 13 sinter generations could be identified between the around 500.000 year old flowstone at the bottom and the holocene stalagmites, that have been grown on top of the late pleistocene cave bear bones, at the top of the profile.

The Bären- and Karlshöhle shows a speleogenetic development of more than 5 million years, that has been broken up chronologically best possible by the here presented investigations to sedimentology, sinter chronology and palaeontology and in correspondence with the processes of the surrounding river and landscape development. The results confirm the importance of the cave for the understanding of the karstification of the Kuppenalb in the Plio-Pleistocene.