Formation and transformation of Pleistocene periglacial slope deposits in the Spessart Mountains (Hesse, Germany)

Abstract

The bedrock of the Spessart Mountains is covered by Pleistocene periglacial slope deposits (PPS- Ds). These slope deposits are supposed to have formed in a periglacial environment by a variety of processes. For this study soil profiles in the Spessart Mountains were analyzed with respect to features elucidating processes forming and transforming PPSDs. Field and laboratory analyses were complemented by micro- morphological investigations to gain more detailed information. The results verify aeolian sedimentation, solifluction and cryoturbation as most important formation processes. Furthermore, several findings sug- gest the influence of additional genetically active processes. PPSDs provide the parent material for Holocene soil formation. In addition, they experience alteration by bioturbation and anthropogenic influence on relief and soil. Pedogenic transformation is dependent on the PPSDs material composition. Particularly the content of silt-sized allochthonous material controls the efficacy of silicate weathering and depth of soil development. The coincidence of pedogenic boundaries and layers often reported in the literature is partly falsified: Eluviation and illuviation of clay is not separated at the boundary between upper and intermediate layer. PPSDs experience strong alteration by bioturbation: This process may transform characteristics that could point to formation processes. Furthermore, thin sec- tion analyses support the distinction of Holocene colluvium and PPSDs.