Late Glacial and Holocene buried black soils in Emilia (northern Italy): genetic and paleoenvironmental insights

Purpose: The existence of black horizons (BHs) is often highlighted in European soils, and in the Po River plain of northern Italy. Nevertheless, BH chronological frameworks and genetic models are still debated. The present study investigated the genesis of BHs in the eastern Po Plain where they are buried at various depths. Materials and methods: Soil sequences were investigated with a multidisciplinary approach integrating geomorphologic, stratigraphic, pedologic, geochemical, isotopic, palynological, and radiometric analyses. Results and discussion: The formation of the studied BHs was scattered over time from the Last Glacial Maximum to at least the middle Holocene. The new data indicate that BHs developed when the landscape was dominated by coniferous forest during conditions that were totally different from the current pedoclimatic setting. The recurrent presence of black particles indicates that this vegetation cover was systematically affected by fire episodes that induced soil degradation and mineralization processes of the original organic compounds, thus contributing to darkening of the upper soil horizons. Conclusions: BH formation clearly coincided with cold time lapses. Evidence for repeated fire events (natural or human-induced?) provides insights for the controversial debate on early anthropogenic impacts on the environment.