2017 Knowe of Swandro Excavation
Evaluative excavation continued upon the eroding beach at Swandro, Rousay, Orkney for a 4 week season in July 2017. The archaeology is suffering from erosion from the sea which has cut into a settlement mound (containing a Mid Iron Age to Norse sequence of settlement) that had developed upon the eastern flank of a Neolithic Chambered Cairn (or Passage Grave). Previous seasons have established the presence of a sequence of structures which has been exposed by the sea cutting into the archaeology, forming a series of terraces. The erosion has provided an opportunity to examine and sample this archaeological sequence. Unfortunately the deposits surviving at the lowest terrace have suffered from extensive erosion, with much of the archaeological matrix having been washed away, leaving the larger structural stones which have been smoothed by the movement of water and beach material. In 2017, work concentrated on the later deposits within the passage of the Chambered Cairn, the eroding area south east of the outer casement wall of the Cairn, and investigation also continued within two of the Iron Age buildings (Structure 2 and Structure 3).
The Chambered Cairn
The outer casement wall of the Neolithic Chambered Cairn is butted by a single faced alignment of stones, suggestive of a retaining wall. This was first observed in the 2012 season and again in 2015, when a much greater degree of erosion was noted. In 2016 this feature was investigated further in order to determine whether an old ground surface or underlying archaeology had survived the effects of the erosion by the sea. A number of large water worn boulders were found to be re-deposited, implying the movement of large 'storm thrown' rocks. There is no surviving evidence of any anthropogenic deposits or an in situ old ground surface on the seaward arc of the outer casement wall of the cairn. A sequence of deposits was found to be retained by a second wall butting the outer casement wall and was investigated in 2017. These deposits have been subject to some tidal scouring but appear to be a sequence pre-dating the mid Iron Age roundhouse Structure 1. Investigation in 2017 provided strong evidence to suggest that there are also stratigraphic elements (structural and depositional) in this area that predate the construction of the outer casement wall of the Passage Grave.
Passageway into the chambered tomb showing later the structure built across and blocking the entrance
The entrance passage leading into the Passage Grave was defined in 2015, upon the uppermost (landward) erosion terrace. The passage walls are single faced and the upper infill formed by a layer of small angular stone (shillet) containing copper alloy fragments, large fish and mammal bone appeared to reflect late activity. This was confirmed by the finding in post excavation of a coin of EANRED, King of Northumbria 810-840 AD, together with the bones of several cats. This disturbance and infilling may represent Viking period activity. Work in 2016 continued to define the top of the passage and to assess the nature of this later activity. The further excavation of the passage revealed more faunal remains, including bones of sheep displaying metal butchery marks. The remnants of these later deposits were excavated in 2017 and the large angular rubble which appears to be the infill of the passage was defined along the length of the passage. The area outside of the passage was also investigated in 2017 and evidence of in situ lintels of a cell-like feature was found on the landward side of the passage entrance outside the casement wall.
The later building built against the entrance of the chambered tomb (at the right of the picture). The red-and-white scale is 1 metre and is laying across the lintelled entrance to the later building, just behind one of the broken lintels.
Structure 2: A Late Iron Age Roundhouse
Definition of the upper eroded terrace of the beach identified the remains of what appeared to be half of a cell-like circular structure. In 2016, investigation indicated that an orthostatic divide with flagging either side (which had been identified in 2015), were clearly later elements forming a modification to the building. These were removed to reveal the original form of the building, the curved line of orthostats together with a door sill (threshold stone) indicating a western entrance. The seaward section demonstrated a greater degree of erosion and did not survive. In 2016 a floor level defined by large flags was identified. The flag floor and the hearth are clearly part of a sequence of floors representing several modifications to the building as the remains of part of a rectangular stone tank could be clearly identified under the flags. In 2017 these flags were lifted and the sequence of ash, mixed “midden like” material and stone packing were investigated. The rubble infill of the tank was excavated and the lower infill sampled. During the excavation a coin, a Nummus of Constans dating to 348 - 350 AD, was found.
The Late Iron Age roundhouse Structure 2
Structure 3 The Pictish Smithy
Structure 3 is a cellular structure with features suggesting a Pictish date, mostly still sealed by the northern (landward) section. The southern wall was identified and excavated first and revealed evidence of an intramural cupboard, adjacent to a complete in situ cupboard. In 2016 the contexts in the lower sequence under the rubble infill were found to contain some evidence of metal working with finds of slag, small crucibles and mould fragments together with evidence of fragments of copper alloy. A series of steps were found to lead from the north (landward) section into the building, in a curved passageway whose stones demonstrated wear consistent with rubbing caused by the passage of the past occupants. The presence of a threshold stone in the narrow passage, together with a bolt hole clearly indicates that there would have been a physical door dividing the passage from the central area of the structure.
Investigation in 2017 (aided by the archaeometallurgist Dr Gerry McDonnell) identified more evidence of metal working including part of a fired clay tuyére. Evidence of a hearth which had two phases of use and an associated ash rich surface was investigated and sampled. Further archaeological evidence for both copper alloy working and iron working was recovered in the 2017 season. A fallen, large elongated beach cobble appeared to have been once set upright adjacent to the hearth. The end of this stone had damage which was suggestive of its use as an anvil. Earlier wall elements representing a larger building, in which this Pictish cellular structure was constructed, were further defined in 2017.