EHG6481 - Geoarchaeological survey - proposed Edinbane Substation, Balmeonach, Skye

A geoarchaeological evaluation was carried out by AOC Archaeology Group in 2025 at the site of the New Edinbane Substation near Balmeanach, Isle of Skye. The geoarchaeological evaluation comprised the drilling of nine hand auger interventions to supplement the machine borehole samples and data. A further 3 purposive geoarchaeological boreholes were drilled to a maximum depth of c. 6.5 m BGL, cored samples were extracted and retained. The deposit sequence recorded across the site included a basal unit of tertiary bedrock. This comprised Skye Lava Group Basalt and Microgabbro, which comprised cobbles and gravel of dark grey, black, and reddish brown, speckled with white, gabbro. It was encountered only in 13 of 86 interventions, and as such the surface was thought unlikely to be well represented in the deposit models. It ranged between 71.55 to 85.39 m OD, rising in elevation towards the north of the site. Pleistocene till, comprising a stiff to firm gravelly and sandy clay which was reddish brown to bluish grey in colour, was recorded in 47 interventions providing an accurate model for the probable land surface at the beginning of the Holocene. This ranged between 66.41 and 93.99 m OD, declining from north to south. Several hollows were recorded in the surface. The till was overlain with herbaceous to woody peat in 61 interventions, with a thickness of up to 5.87 m and a surface elevation between 68.46 and 94.24 m OD. Archaeology, comprising structural remains and a clearance cairn were recorded in 3 interventions between 75.25 and 78.00 m OD among the flatter, middle elevations of the site. Redeposited peat was recorded in 4 interventions, with thickness of up to 1.90 m and surface elevation between 73.50 and 79.26 m OD. Nine interventions recorded Victorian to modern made ground deposits, with thickness of up to 1.00 m and surface elevation between 69.16 and 90.07 m OD. Topsoil was recorded in 76 interventions, with a thickness generally of up to c. 0.40 m. In the northeast of the site, thicker topsoil was recorded up to c. 1.00 m. It was considered that development impacts from the currently proposed substation may affect the in-situ Holocene sequence, which could preserve archaeological and palaeoenvironmental remains. The surface of the Pleistocene till and earlier geology also presented further potential for preservation of in situ archaeological remains associated with the prehistoric onwards, which may be disturbed or truncated by the development. It was recommended that the impact on deposits of interest may be mitigated by carrying out a programme of palaeo-environmental assessment to determine preservation potential for ecofacts such as pollen, diatoms, ostracods, and plant macrofossils. This should be paired with radiocarbon dating to determine the period of formation for peat deposits, as well as changes in the peat lithology such as changes between herbaceous and woody peat. <1> Palaeo-environmental assessment was subsequently carried out on samples obtained from the site and from those from a previous phase of palaeo-environmental coring (see EHG6298). Assessment of the peat provided a long-term record of landscape evolution, vegetation succession, and peatland succession dating from the Early Mesolithic / Early Holocene. No direct evidence of human activity was recorded. It was considered that the development impacts from the currently proposed substation may affect the in-situ Holocene sequence, which would have a high potential for preserving palaeo-environmental remains dating from the Early Mesolithic / Early Holocene. Proxies provided insight into the changing mosaic of vegetation types, including expansion and reduction of woodland, which may have directly or indirectly affected past human communities. It was recommended that the impact on deposits of interest could be further mitigated through palaeo-environmental analysis to further constrain the chronology of the accumulation and spread of peat across the site. This would provide more detail about the changes in woodland and grass wetland and may provide indirect evidence of the impacts of human activity on the site. <2>