"Usselo soils" - the Late Glacial marker horizon identified in the Labe River region (Central Bohemia, Czech Republic)
Abstract
The Late Glacial (LG; ~16-11.7 ka BP) is characterized by rapid and pronounced climatic oscillations and distinct environmental changes throughout the former periglacial zones. Although the effects of these climatic events have been well documented using paleobiological methods (especially in lacustrine and organic sediments), our knowledge of the simultaneous soil formation processes or overall physical landscape transformation and dynamics along the climatic transition is still very fragmentary.
As the loess accumulation in Central Europe terminated by the end of the Last Pleniglacial (~18 ka BP), the most of information on the pedogenesis dynamics comes from the sandy aeolian sequences and from related sediments. In Europe, the aeolian deposits are the most continuous in the northern and north-western part of the continent (the so-called European Aeolian Sand Belt - EASB, Fig. 1).
They are occasionally separated by paleosol horizons, from which the so-called Usselo and Finow soils are the best preserved. The Usselo soils are mostly classified as the Albic Arenosols; they typically consist of greyish Ahb and Eb horizons, and frequently bear charcoal indicating widespread and repeated fires of still unknown origin (natural ignition and/or human burning?).
The recent claim that the Usselo soil is an event layer from rapid aeolian sedimentation through an extra-terrestrial impact was not confirmed. The Usselo soils, broadly correlated with Alleröd interstadial, represent an identifiable pedological marker horizon stretching over a large area of the northern Europe.
However, since the knowledge of the LG pedogenesis dynamics of the sandy aeolian environments out of EASB is still very poor, the comparison of the northern regions with the rest of past periglacial zones remains problematic. In this paper we present results on stratigraphy, sedimentology, pedology and paleobotany from the sandy aeolian sequence situated in Central Bohemia (Czech Republic), (49.9°N, 15.5°E; ~ 300 a.s.l.).
In this sequence, the soil buried by 2m thick aeolian sand was found. The paleosol was analyzed in order to evaluate its regional pedostratigraphical and paleoenvironmental potential.
Paleosol (classified as the Podsol) consists of dark greyish Ahb and Eb horizons. Humic horizon is extremely rich in macroscopic charcoal fragments, which were determined as Pinus sylvestris, Salix sp. and Populus tremula.
Radiocarbon age 13,797-13,528 cal yr BP revealed from the charcoal (Table 1, Fig. 3) suggests the paleosol to have developed during the Alleröd interstadial. Stratigraphical and sedimentological context, paleobotanical record as well as micromorphological features (Table 2, Fig. 5) allow us to correlate the paleosol with the Usselo soils.
Such doing, this provides the first evidence on the typical Usselo soil out of the EASB. Nevertheless, the studied paleosol differs from the typical Usselo soils of the EASB by higher intensity of eluviation, which could be a result of the site-specific hydrological condition or differences in regional climatic conditions.