Buried Podzols as a pedostratigraphic marker for the Medieval Climatic Optimum: Grębociny soil in the dune deposits of the European Sand Belt

The paleopedological record documented in aeolian dunes of the eastern European Sand Belt comprises predominantly Arenosols and only occasionally well-developed Podzols. There are several Late Pleistocene pedostratigraphic marker horizons of varied soil types designated in the European dune and loess deposits, but none falls within the range of the Holocene. Buried Podzol occurrences found recently in 10 inland dune sites dispersed throughout Central and Eastern Poland share similar pedological properties, geomorphological setting, and age in the 5th–15th century AD range of the historical Middle Ages. Therefore, they meet the criteria for distinction as a pedostratigraphic marker under the name Grębociny soil, after a locality with the most advanced podzolization of the paleosol dated to the High Middle Ages (1000–1300 AD). Preservation of the soils was enabled by burial during anthropogenically induced dune remobilization. At least some of the investigated dunes were used as pasture during soil development, as evidenced by tetrapod hoofprints recorded in and above the buried Podzols. Prevalent podzolization during the Middle Ages, in contrast to preceding and later times, could be facilitated by not only an impact of agriculture and forestry, but also relative warmth and humidity of the Medieval Climatic Optimum (ca. 900–1400 AD).