Tracking textural, mineralogical and geochemical signatures in soils developed from basalt-derived materials covered with loess sediments (SW Poland)

This study investigates the scale of inheritance of signatures typical of loess- and basalt-derived substrates in soils having both components present as parent material due to past periglacial processes. Based on field description, particle size distribution, mineralogy (heavy minerals and clay minerals) as well as geochemistry we track the signal of both materials (local basalt-derived and loess-derived), estimate the maximum thickness of loess mantles and mixed zones (having both loess and basaltic components), and note the presence or absence of basal layers without allochtonous additions. The results show that geochemistry and heavy minerals are the most reliable proxies for a verification of aeolian silt contributions and to define individual layers in complex soil parent materials. Soil formation in the studied landscape depends on the type of slope sediments. Typical fine-grained weathering of basalt without input from aeolian silt would promote rather vertic development. However, in thick loess deposits as well as in thin silt-textured materials superimposed on clay loam beds, clay illuviation dominates. Development of argic horizons, however, results in decreasing permeability, promoting water stagnation and enhanced degradation processes in clay-rich subsoil. Instead of Luvisols, Stagnosols and Retisols developed in the study regions. Basaltic block covers mixed with loess host cambic horizons. Based on our findings it seems that at the edge of thin loess deposits no soils exist that developed exclusively from basaltic parent materials.