Excavation
Date 16 October 2015 - 31 October 2015
Event ID 1027210
Category Recording
Type Excavation
Permalink http://canmore.org.uk/event/1027210
NO 44450 98930 This work was carried out, 16–31 October 2015, as part of a wider project investigating crannogs in NE Scotland and forms a large part of the author’s PhD research. Excavation aimed to establish the nature of Castle Island and to identify contexts that might provide well contextualised material for radiocarbon dating. A previous submerged survey of Castle Island had indicated an artificial origin below the waterline for the island.
Excavation was preceded by three days (16–18 October 2015) of submerged survey which again revealed the artificial appearance of the submerged portions of Castle Island. Nine timbers and six vertical driven piles were identified in the water around the island in 1.5–2.5m of water. These features were surveyed using DGPS.
A topographical survey was conducted over the whole of the island (both above and below the waterline) using a DGPS to take individual points with height data. This was then used to create a digital elevation model of the island. Two stone-built features were also identified and surveyed. The first is a possible boat naust, of which a maximum of two courses of stone work are visible on the surface. It is oval in shape and measures 3 x 5m. The other is also of dry stone construction, is more rectangular in shape, measures 3 x 7m, and can be presumed to be later as it appears to reuse stone and sits on top of consolidated material.
Five trial trenches were opened on the island. The first, a 1 x 1m trench, targeted the lower reaches of the mound, at the approximate location of the former shoreline of Loch Kinord (it was lowered in successive phases in the 19th century by a total of c1m). This trench recorded c1m of apparently eroded material, which had moved downslope. Below this was a compact layer of dark sediment with frequent charcoal inclusions, which overlay a sterile fine sand. The layer of dark sediment is probably a midden layer at the edge of the former island. Crucially, it reveals the height of the probably scarped sides of the island.
Two other 1 x 1m trenches were placed in the central flat area of the island. These trenches revealed that the topsoil consistently contains charcoal. Both trenches came down onto natural sands, gravel and cobbles after c0.2m of topsoil and subsoil. These trenches clearly established the natural origin of the island.
A fourth trench, measuring 3 x 2m with a 1 x 1m annexe, was opened over the break of slope from the central flat area to the side of the island. This trench revealed substantial deposits and negative cut features including a 1.45m deep pit. These contexts were half-sectioned and bulk samples were taken for flotation. A 10 x 30mm fragment of a crucible was recovered from this trench. It is thin walled and its fabric is porous with the surfaces appearing to have been subject to vitrification.
A final 0.5 x 0.5m trench was opened in a third location on the central flat area of the island. This trench revealed an anomalous slope to the underlying natural which appeared to slope inwards towards the centre of the island.
The excavation results demonstrated that Castle Island is not a crannog in the classic sense, as initially thought. Rather it appears that large amounts of natural deposits have been reworked and moved downslope giving the appearance of an artificial island below the waterline. The site is probably best classified as an insular island motte.
Archive: Aberdeenshire SMR and National Record of the Historic Environment (NRHE) intended
Funder: Society of Antiquaries of Scotland
Michael J Stratigos – University of Aberdeen
(Source: DES, Volume 16)
