ABSTRACT
The Muschelkalk formation of the Germanic basin can be separated into three different lithlogical units. These are the Lower, Middle and Upper Muschelkalk. The upper and lower unit consist mainly of limestones which are separated by shales, whereas the Middle Muschelkalk consists of evaporite deposits.
The dissolution of evaporites causes an irregular subsidence of the overlying unit, accompanied by additional fracturing and increasing karstification. The process is apparently selfperpetuating because fresh water gaining easy access to the salt through the collapsed and fractured overlying layers. In this area we find all phenomenons of a mature karst terrain, e. g. sinkholes, areas with no surface flow and caves. Due to the alternating layers of limestones and shales in the Upper Muschelkalk the karstification is often parallel to the bedding of the layers.
We can find three different states of regional karstification. These states depend on the thickness of the overlying Keuper sediments, which retreats stepwise from the north-west to the south-east. The spatial and temporal geological and hydrogeological evolution of the karst system began in the oligocene.
More than 70 tracer tests have been carried out in the last 30 years - most of them by the Geological Survey of Baden-Württemberg. The results show a significant correlation between the lithology and the evolution of the karst system. One of the most interesting tests with two different tracers (uranine, polystyrene microspheres) is dicussed here in detail.
