The Archaeological Significance of Patterns of Anomalous Vegetation on a Raised Mire in the Solway Estuary and the Processes Involved in their Formation

Abstract

While the location and identification of archaeological features from vegetative responses on “dry-sites” is well understood in a British context, its application to wet sites is less well explored. Following the recovery of Glasson Moss, Cumbria, from a major fire in 1976, and a programme of hydrological restoration, a pattern of circular and linear features was observed during a field survey in the mid-1990s. Assessment of the archaeological significance of these features was undertaken in 1996 and 1997 using aerial photography, fieldwork and historical research. The results suggest that during the Early Mediaeval period, natural pools within the moss were used for hemp retting. It appears that water levels within the pools were controlled by the construction of narrow ditches with possible simple sluice systems. One pool was examined in detail; it was used for retting from c.7th century ad until it dried out during the late 12th to mid-13th centuries. Disruption to the mire hydrology, possibly combined with trampling activity around the pool and ditch, appears to have instigated vegetation succession, which resulted ultimately in the colonization of the edges of both pool and ditch by swathes ofCalluna vulgaris (heather). The time scale involved in these changes is unknown, although similar responses were noted as beginning to occur at the site of nearby tithe apportionment boundaries (narrow ditches) dating from 1816. This process of vegetation change is examined.