Differentiation of fen bedrock in the Mrągowo Lakeland (NE Poland) in relation to Pleistocene terrain morphogenesis

Abstract

Abstract The Mrągowo Lake District (NE Poland) with the area of 182 800 hectares was formed in 1/3 during the Poznań phase (POZ) of the Vistulian glaciation, and in 2/3 in the Pomeranian phase (POM) of that glaciation. A number of fens in the Mrągowo Lake District is 1164, and they occupy 5.9% of its total area. Majority of fens (1018) with an area of 8620 ha is located in the zone of POM phase, and the remaining fens (146) occupying 2157 ha occur within the zone of POZ phase. Peatlands cover 3.5% of area of POZ phase and 7% of area of POM phase. The mean size of fens in the Mrągowo Lake District is 9.3 ha (mean size in POZ phase zone is 14.8 ha and in POM zone – 8.5 ha). Limnic deposits predominate in the bedrock of fens (92.5% of the total number of fens). Originally, lakes occupied 11% of the Mrągowo Lake District, of which 1/2 was transformed into fens. More than 50% of peatlands developed on organic gyttja, 27% on calcareous gyttja, and almost 14% on mineral gyttja. About 7.5% of fens formed as a result of paludification.