For more than one century, the textural B-horizon of the last interglacial soil and its cover deposits have been standing out in Europe as an important pedostratigraphic marker. The complexity of this horizon was well illustrated since the seventies, though its pedological and stratigraphic significance remained doubtful. Macro-, meso- and micromorphological data gathered by the authors at various key-sites in Europe and the sequential correlation principle have resulted in a better understanding of the high complexity of the pedosedimentary and stratigraphical evolution of the last interglacial and early glacial loess succession. The present study identifies four megacyclic pedosedimentary intervals that show a general trend towards dry and continental climatic conditions.

A consistent correlation exists between pedosedimentary evolution and vegetation, as recorded in the Grande Pile pollen record. The picture obtained in the present study is similar for both the Western and the Eastern European loess palaeosol successions. The so-called ‘last interglacial soil’, with three major soil-forming processes, belongs to the Eemian and Saint-Germain I (MIS substages 5e and 5c), whereas the humiferous sediments and soils on top are linked to Melisey II, Saint-Germain II and Ognon I (MIS substages 5b and 5a).The overlying loess, colluvial sediments and humiferous soils that end the palaeosol succession belong to the Ognon II and III interstadials; they record the onset of the early Pleniglacial (MIS stage 4) characterized by a significant increase in aeolian sedimentation.

In an area east of Leuven (central Belgium), a buried sandy estuarine deposit of Oligocene age contains a dark colored organic layer of about 4 m thick. Our results suggests that the organic matter is an illuvial horizon, therefore warranting the hypothesis that the layer may qualify for a giant buried spodic horizon rather than a remainder of a Tertiary oil seepage as suggested by Van Riessen and Vandenberghe (1996). Of particular importance is the micro-morphological evidence, which reveals that the mainly monomorphous organic matter is present as ubiquitous coatings and concentrations around the quartz grains. These coatings show the for Podzols very typical polygonal cracked patterns. The geochemical signature (stable carbon isotope analysis) also gives strong indications for a continental origin of the organic carbon and therefore support the pedogenetic origin of the horizon. The paleopedological scene into which this soil has developed is inferred from the data.