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Birsay-Skaill Landscape Archaeology Project

Date August 2011

Event ID 964737

Category Project

Type Project

Permalink http://canmore.org.uk/event/964737

HY 2365 1962 and HY 2460 2700 This project, which began in 2003, focuses on building landscape context for erosive coastal areas with significant windblown sand. Geophysical survey and targeted excavation have taken place at three bays and their hinterlands at Birsay, Marwick and Skaill.

The Brough of Birsay, the Point of Buckquoy, parts of Birsay Links, and areas surrounding the bay frontage at Marwick were all surveyed 2003–10. Survey and excavations in 2003–10 at the Bay of Skaill concentrated on the N bay environs. Gradiometry showed a dense concentration of magnetic anomalies on a group of five large settlement mounds on the northern margins of the Links of Skaill, immediately NE of the bay frontage. These have been tested selectively by excavation.

Excavations in 2004–10 revealed Viking and Norse period middens stratified over well preserved stone buildings on two large settlement mounds: ‘Castle of Snusgar’ and ‘East Mound’. On ‘East Mound’, a coherent complex of stone structures surrounding a longhouse 26.3m in length was revealed in 2010, with walls standing up to 1m high with clearly defined internal and external areas, stone flagged floors, yards, flights of steps, and entrances. Radiocarbon and OSL dates from samples taken in 2004–8 indicated a general chronology AD c950–1200 for occupation layers on ‘Snusgar’ and ‘East Mound’. Further refinements in 2011, from dates taken from occupation levels and metalworking hearths in 2010, and ongoing statistical analysis by Derek Hamilton of SUERC, suggest the main domestic occupation phase of the longhouse and its associated buildings on East Mound is dated to a relative narrow chronological range in the early 11th century AD.

In August 2011 a 15 x 2m trench was excavated on the sloping periphery of the settlement complex to test the mound/soil formation deposits in this area. As with other peripheral interventions on the edges of these settlement mounds, a complex build up of laminated sands and buried ground surfaces was exposed, trending towards waterlogged silts nearest to the burn edge, and showing indirect settlement influences. These layers were sampled and recorded in section and further soil, environmental and dating analyses are in process. A 2 x 2m test pit was also machine excavated on a possible smaller mound feature to the SE of ‘East Mound’ on the other side of the burn. This area had been surveyed using magnetometry in 2005, with generally negative results, and the test pit confirmed a depth of clean windblown sand to 2m, the lowest practicable excavation depth in such soft and unstable ground, eliminating the possibility that this particular ‘feature’ is archaeological in origin.

Geophysical survey was undertaken using a Bartington G601-2 gradiometer and a Geoscan RM15 twin probe resistance meter, on 20m grids taking readings at 0.25m with 1 separation, and the data was processed using Archaesurveyor™ software. In 2011, a possible mound feature 100m to the E of ‘East Mound’ at the Bay of Skaill was surveyed with both magnetometer and resistivity, having been topographically surveyed in 2010. The site was found to be badly contaminated by modern activity but some potential was highlighted at the uppermost part of the feature where a stone dyke crosses it. A surface survey and geophysics where also undertaken on the one remaining scheduled site yet to be investigated within its study area: the mound known as Saevar Howe (SAM 1373) on the southern edge of Birsay Links. This is another large sandy settlement mound, known to be of significant archaeological interest, having been excavated on two previous occasions in 1862 and 1977, producing evidence of Pictish and Norse burials and structures. Its current condition is poor, suffering weathering and deflation, and animal erosion by rabbits and cattle. A large deflation hollow occupies the centre of the mound, which partly may be due to previous excavations, and which is strewn with metallic and other debris dating from WW2 and later. The survey aimed to further characterise its remaining archaeological importance and assess its vulnerability to further degradation. A topographic model was compiled using a Leica 400 Total Station and Surfer™, which was supplemented by 0.64ha of combined magnetometer and resistivity survey. A large rectilinear feature occupies the upper area of the mound, surrounding the deflation hollow, which is of potential archaeological significance. This possibly represents a large, coherent stone feature which has probably been made visible magnetically by a build up of midden around its exterior. Elsewhere on the mound, and particularly on its northern side, are more diffuse amorphous anomalies of a type which have become familiar on several such large sandy settlement mounds already surveyed at the Bay of Skaill. These are caused by multiple layers of organic midden and windblown sand producing a combined magnetic response. Resistivity and 3D survey modelling have helped to give these some depth and topographic resolution. This summary is based only on the first stage of visualising the results: further processing and refinement is ongoing.

Archive: University of Oxford (currently). Reports: Historic Scotland, Orkney Museum and RCAHMS

Funder: Historic Scotland, Oxford University and Orkney Islands Council

University of Oxford, 2011

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