Formation of black carbon rich ‘sombric’ horizons in the subsoil – A case study from subtropical Brazil

The formation of sombric horizons (dark horizons in the subsoil) is still not understood. In order to improve our understanding of the formation of sombric horizons we studied these soils in southern Brazil from various perspectives. The lateral configuration and grain size distribution excluded the possibility that the sombric horizon is a paleosol covered by an eolian deposit or colluvium. Micromorphology showed intense biological activity,...