Using soils as indicators of past slope instability in forested terrain, Kamienne Mts., SW Poland

The Kamienne Mts. in SW Poland abound in geomorphic evidence for past landslides developed at the rhyolite/sedimentary rock contact, but it remains unknown when the displacements occurred. The slopes generally have been stable in the last 200 years or so, covered by historical records. In this paper we use the presence of periglacial solifluction layers (cover-beds) and soil characteristics as indicators of the status of hillslopes and relative age of landslides. We follow an assumption that if landslides predate the Holocene, then solifluction layers should be present and soils within and outside landslide-affected slopes should have similar characteristics, allowing for differences caused by local factors. Cover-beds are not expected to be associated with Holocene landslides. Differences in the degree of soil development may be used to argue for different ages of some landslides within the Holocene. The absence of solifluction layers cannot always be regarded as the evidence of post-Pleistocene landsliding since such a layer is unlikely to have ever formed on densely jointed, but otherwise strong, rhyolite. Soil morphological properties, particularly horizonation, helped to establish the relative chronology of mass movement and to recognize both early to mid-Holocene and late Holocene landslides. Soils are good relative-dating tools and their usage does not necessarily require adherence to any particular soil classification system. This is because morphological features of entire profiles provide more information than diagnostic properties used in these systems.