Thanks to funding from the North Isles Landscape Partnership (NILPS), a team from ORCA (UHI Archaeology Institute) undertook geophysical surveys at three suspected Neolithic chambered cairn sites in Orkney for the Tombs of the Isles project.
These took place in Rousay, Shapinsay and Stronsay in late April and early May and followed the survey of two sites in Sanday in 2022.
The aim was to establish more about the sites’ character, form and landscape context. Geophysical survey is non-intrusive and we had consent from Historical Environment Scotland (HES) to work at these important, protected sites.
Two techniques were used at all sites, providing contrasting data sets allowing for better interpretation:
- Magnetometer survey: good for identifying magnetically enhanced material from burning and settlement activity.
- Earth-resistance survey: good for locating walls and structures.
Note that the data processing is provisional and full digitised drawings will be produced for the report in due course.
Knowe of Lingro, Rousay
The Knowe of Lingro is visible as a large, rectangular, turf-covered mound, with a slightly concave top. There is no record of it being excavated but it appears to be an intact stalled Neolithic tomb. Orthostats visible protruding from the top are suspected to be dividers within a central chamber.
The resistivity data shows the stone construction of the tomb (black, which is high resistivity). The shape is consistent with a stalled cairn, even showing some of the orthostatic dividers. The interior is lower resistance and could indicate a less stoney, more soil-like fill.
The structure appears to be a bit wider at the eastern end, which might suggest this is the location of the entrance.
The magnetometer data is fairly quiet on and around the tomb, showing that it is not very enhanced – a typical response from funerary monuments. There are possible rig and furrow and drainage-type features around the outside, suggesting that it was cultivated more recently right up to the edge of the tomb.
Castle Bloody, Shapinsay
Castle Bloody is a heather-covered mound with a modern cairn on top.
Due to the visible complex of stone slabs and wall faces, it has been suggested the site was an Iron Age souterrain (perhaps dug into an older structure) rather than Neolithic tomb.
Several holes have been dug into it and large stones are exposed.
The soil around the mound is very thin, with bedrock visible in several places. Despite the challenges of surveying around three wire fences (which impact on the collection of sensitive magnetic data), there were low magnetic responses from the centre of the mound (which might otherwise suggest the presence of burning, hearths, dumps of midden), suggesting that the mound is not a domestic site, or somewhere that has been intensively occupied.
The resistivity data has revealed a square-shaped structure c.15m in length inside the mound, the interior of which is of a higher resistance, maybe indicating rubble fill and voids.
On the western side a possible stone revetment or external wall could be present.
Combined, these results suggest the site is not a settlement and rather than a souterrain is more likely to be a Neolithic tomb built on an outcrop.
Cutter’s Tooer, Stronsay
The site, which is also recorded as Cutter’s Tuo, consists of a rounded, grassy mound with numerous stones protruding from the surface.
It is visible as a distinctive monument on the headland at Griceness. From a distance the mound appears to sit upon a platform. On closer inspection, large horizontally set stones are visible at several points around the perimeter, forming an outer kerb.
The resistivity data show the mound to be of very high resistance indicating that it is very stony with possible voids.
No structure is immediately visible within the mound, although a ring of slightly higher resistance (black) circling the mound corresponds to the stones visible around the edge of the platform.
A ring of low resistance could be a surrounding ditch but is more likely to result from the presence of a soily platform.
The magnetometer data show a magnetic anomaly around the centre of the mound.
A curvilinear anomaly is also clearly visible on the east of the mound. This could represent enhanced material which has accumulated within or been added to the inside of the outer kerb of stones.
The addition of such material is likely to have occurred when a Neolithic tomb was reused and remodelled in the Bronze Age, with the possible insertion of a cist.
The enhanced material possibly derives from the incorporation of cremation or cremation pyre material.
Anomalies to the south of the mound could be more recent kelp pits, which were observed in the area. There are kelp-drying dykes to the north of the site.
Around 300 metres to the east a second site was surveyed. This low earthwork tops a natural rise in the field.
The eastern section was in the form of a round enclosure, evident in the resistivity data. Higher responses in the magnetometer data suggest it could represent a prehistoric occupation site.
