A programme of archaeological work was conducted by SLR Consulting and Gerry Martin Associates in advance of and during construction of the Assel Valley wind farm, to the south-east of Girvan. This work comprised a number of elements, including survey and fencing, to ensure that features were not damaged by the development, and monitoring of ground disturbance associated with construction activity.
During the course of this work, a field system was identified in the area adjacent to one of the proposed turbines. This survived as a series of low earthworks, measuring between 1.5m and 5m in width. A rapid survey was undertaken to provide information on the location, size and nature of these earthworks, which suggested that the extant features were only part of a partially-surviving field system that appeared to have developed over time, with incremental additions as and when required, rather than one that was laid out in a single phase.
At one point, one of the banks that comprised this field system was to be truncated by construction of a turning area. As a result, a section was cut across this feature to record its composition. This demonstrated the presence of a shallow gully feature, apparently representing the source for the material used to construct the earliest phase of the bank. The width of the bank had subsequently been increased using material from elsewhere, with the widened embankment covering the original quarry gully. An environmental sample was taken from the fill of this gully for a date via Optical Stimulated Luminescence (OSL). OSL provides a measure of when sediment was last exposed to sunlight, and returned a date of AD 846 to 1206 (990 +/- 180 years BP, where present is 2016; Laboratory Code X6991). This suggests that these boundaries formed part of the enclosure system that originated from the early medieval period. This is significant, as on surface inspection alone it is possible that they may have been assessed to be of more recent date. It also demonstrates the potential for OSL to be used in relation to sites of this type.
Elsewhere on the site, a second boundary earthwork was also affected by construction of a section of new access track. Again, a section across this feature was recorded, which demonstarted that the bank measured 1.85m in height and 5.75m wide, but had no associated quarry ditch. Two archaeological layers were identified, the first being the imported sediment of the bank, which overlay a possible buried ground surface. Radiocarbon dates were obtained from two fragments alder/hazel charcoal taken from a soil sample of the possible ground surface underlying the bank. These were found to date to 2029-1887 cal BC (3596 +/- 30 BP, SUERC-66695) and cal AD 545-644 (1472 +/- 29 BP, SUERC-66450). These late Neolithic / early Bronze Age and early medieval dates suggest that from more than one period is present in the layer. The inclusion of material dating to around the 7th century indicates that the bank may be of an early medieval at the earliest, but equally may date to a later period in history. It is quite feasible, given the nature of the earthwork, that it is contemporary with the enclosure system dated using OSL.