Palaeopedology and magnetic susceptibility of a loess–palaeosol sequence in southwest Germany

Abstract

Abstract A loess–palaeosol sequence that formed during the last and the penultimate glacial–interglacial cycle was studied by pedological, geochemical and rock magnetic methods. Particular emphasis was placed on magnetic susceptibility in order to derive a climatic signal. Problems of separating the influence of palaeo-relief, hydrological influence and climate complicate the interpretation, but the results show that minimal levels of soil formation cause a distinct enhancement of the magnetic properties. Higher magnetic susceptibility signals characterise the more oxidized parts of the palaeosols. Alternatively, hydromorphic processes operating on the ferrimagnetic minerals cause a decrease in magnetic susceptibility, reflecting both past climate and changes in the palaeoenvironment. Extremely low-susceptibility values characterise the reduced greyish zones of the interglacial Bt horizons. Additional complications are introduced because magnetic susceptibility may change along the horizons of one soil profile. Eluvial horizons tend to have lower concentrations of ferrimagnetic minerals than the loess parent material, whereas the corresponding illuvial horizons show an increase. It is considered that palaeoclimatic interpretation based solely on magnetic susceptibility must be treated with great caution.