Periglacial cover beds and soils in landslide areas of SW-Germany

At the slopes of the Jurassic cuesta scarp in SW-Germany, pedological and mineralogical investigations were carried out in landslide areas. So far, it is possible to distinguish two well-defined landslide areas, one of them belonging to the Pleistocene, the other one characterised by Holocene movements. In general, the distribution of soils and sediments is strongly linked to the age of landslide deposits. In Pleistocene landslide areas, the parent material of the studied soils is formed by periglacial cover beds of Late Pleistocene age, consisting of Jurassic, aeolian and volcanic components. The Upper Periglacial Cover Bed was recognised as the most important marker horizon in the studied slope areas. There, the existence of minerals originating from the eruption of the Laacher See volcano, dated to 12,900 yr BP, could be demonstrated for the first time. Most of the Pleistocene landforms are characterised by well-developed soils, like Clayic and Vertic Cambisols, whereas relic soils exclusively occur in the oldest parts of landslide deposits. Landslide areas affected by Holocene slope processes do not exhibit periglacial layers, as mass movements removed periglacial sediments and former soils extensively. As a consequence, the parent material is different from those of Pleistocene landslide areas. Therefore, sediments in these areas are characterised by Jurassic components and only initial soils are present.