Original paper

Lithological Discontinuous Soils Archives for the Pedo-Geochemical Genesis of the Soil-Regolith-Complex?

Lorz, Carsten


Lithologically discontinuous soils (LDS) have developed in originally layered parent materials (soil-regolith-complex) and are a rather common than exceptional phenomenon. If LDS are used to reconstruct soil genesis - especial the pedo-geochemical evolution - an allochthonistic approach combining pedogenesis and geogenesis is needed to "read" these archives.The depth functions of acidification parameters (pH, base saturation) in profiles with contrasting layers are used as archives. It is shown that a strong original contrast will cause a distinct effect of stratification on present soil properties. The contrast is intensified between upper layer and underlying material as a secondary pedogenic effect due to physical restrictions of the rooting depth and consequent cation uptake by trees and export from the system. No contrast occurred if the geochemical differences between layers are too weak. From the additional comparison with anthropogenic cover beds it is concluded that the intensity of acidification is often not strong enough to blur stratification.The dispersal of heavy metals in LDS is analyzed using the depth functions of mobile and lithogenic fractions. For the lithogenic fraction contrasts reflecting stratification are common, since each layer must be seen as metal-stratigraphic unit with its own metal amount and spectrum. However, if clay is enriched by illuviation this effect can be blurred. In addition, the depth functions of mobile fractions (atmospheric or pedogenic origin) are often influenced by secondary effects of stratification, since the element mobility can be restricted by contrasting physical properties of LDS.In conclusion it is shown from the example profiles, that the use of LDS and their depth functions as archives for pedo-geochemical evolution is only possible if an allochthonistic approach is used which takes layered parent materials into account.