Patterned fen development in northern Scotland: developing a hypothesis from palaeoecological data

The recent discovery and description of patterned fens in Scotland has raised questions about their origins and development. A series of possible developmental models has been derived which are tested using data from a well‐developed site in Sutherland, northern Scotland. The site morphology indicates that the fen has developed over a more complex subpeat topography and that the present‐day features are unrelated to the original mineral surface. Stratigraphical information together with radiocarbon dates and pollen age estimates suggest that the mire developed initially in one, perhaps two, narrow gullies as poor fen peats from the early tenth millenium BP. The mire then spread on to surrounding slopes with the onset of ombrotrophic peat accumulation, where the most recent basal age estimate is ca. 3500 yr BP. Poor fen peats extending to the surface began growth at ca. 2850 yr BP, once this ombrotrophic peat cover was complete. A reconstruction of mire conditions based on macrofossil, pollen and other microfossils shows the nature and timing of these changes in more detail. The findings show that the existing models of patterned fen development are not applicable to the Scottish systems. Instead, the poor fen systems are recent developments, which may overlie extensive earlier peat deposits of ombrotrophic character, and are unrelated to earlier peat development. The site has probably developed as a result of localised hydrological changes within the underlying peat body and mineral base, resulting in increased volume and quality of the water supply. It is suggested that this may be by the development and emergence of sub‐peat pipes at the head of a suitable slope.