The loess deposits of the Bohemian Massif: silt provenance, palaeometeorology and loessification processes

Abstract

Abstract The Central European loess bodies in hilly regions, with their high accumulation rates, frequently provide relatively high-resolution “floating” stratigraphies containing both climatic signals common to Europe, and minor peaks arising from local factors such as slope processes, discontinuity events or their palaeometeorological location in the former ice age landscape. The loess–palaeosol series are often viewed from the point of view of palaeoclimate reconstruction, but macroscopic features such as lamination of loess strata corresponding to individual dust storms are better explained by palaeometeorological factors. The study of heavy minerals from different loess localities in the Czech Republic suggests that the North Atlantic Oscillation wind pattern functioned even during the last glacial cycle. The rapid consolidation of “dust accumulation” by cementation bonds represents the key factor in loessification. Calcite and “allophane” impregnations of clay bridges between individual silt grains can be observed. The very nature of “loessification” is associated with rapid evolution of cementation bonds. Experiments reported here demonstrate that significant quantities of white chalky and powdery loess calcite and Si–Al hydroxides are released during repeated freeze and thaw cycles.