2019 Knowe of Swandro Excavation

Excavation in 2019 concentrated on the remains of the large Iron Age roundhouse (Structure 6) and the adjacent area to the south-east containing Structure 4, a Pictish building, and Structure 1. The monumentality of the roundhouse and its focal position within the settlement parallels the positioning of many Orcadian broch sites such as the near-by broch of Midhowe. However the construction of Structure 6, although monumental in proportion, did not provide evidence of standard broch architecture

Drone photograph of the Late Bronze Age/Early Iron Age roundhouse and associated structures at the Knowe of Swandro, Rousay, Orkney.

Drone photograph of the Late Bronze Age/Early Iron Age roundhouse and associated structures. The red-and-white photographic scales (top left and middle bottom) are 1 metre long. The sea is at the top of the picture just out of shot.

Investigation of the passageway into Structure 6 showed at least two structural phases. A cladding wall thickening the wall base of the original wall seems to have been added and associated with this second phase of construction. Material contained in the core infill between this secondary wall and an earlier wall face, forming the cladding on the seaward arc of the roundhouse, returned an AMS radiocarbon date of 732–401cal BC at 95.4% probability (SUERC-88535 (GU52307)). Material stratigraphically later than this cladding and sealed by a wall butting the cladding returned an Early Iron Age AMS radiocarbon date of 760–430 cal BC at 95.4% probability (SUERC-88540 (GU52309)). A third date was obtained from the material butting the later wall and stratigraphically above SUERC-88540. This returned a date of 788–541cal BC at 95.4% probability (SUERC-88536 (GU52308)). These dates indicate that this building represents a monumental Early Iron Age roundhouse with evidence of continuity into the 1st millennium AD.

The southern area of the roundhouse under the boulder beach had been severely affected by the sea. Here much of the finer grained material forming the depositional sequence had been removed by tidal action. Survival was better on the landward side. However in the central zone of the building a major collapse event was evident from the position of slumped or fallen structural orthostats. The structure of this collapse was three-dimensionally recorded by photogrammetry and laser imaging. Evidence for several truncated hearth forms were identified and sampled for archaeomagnetic dating.

White-tailed sea eagle skull recovered along with skull and bones of a Great Auk from the Middle Iron Age phase of the Swandro roundhouse, Orkney.

White-tailed sea eagle skull recovered along with skull and bones of a Great Auk from the Middle Iron Age phase of the Swandro roundhouse.

The northern circuit of the building provided a better insight into the archaeological complexity and potential of the site as it has not yet been exposed to the sea and the effects of tidal action. Part of the northern arc of the roundhouse (Structure 6) had been partitioned off from the seaward side by the construction of a medial wall in alignment with the northern wall of the entrance passage to form a smaller structure (Structure 5). An entrance led into this space which was formed between the north-eastern arc of the inner wall of Structure 6 and the medial wall which bisected the centre of the roundhouse. An upper floor surface was found within Structure 5 containing evidence for several hearths. A long-handled weaving comb and two Roman glass bottle fragments, whose forms suggest a 1st to early 2nd century AD date, were found at this level.

The Iron Age long-handled weaving comb from the Knowe of Swando, Rousay, Orkney

The Iron Age long handled weaving comb

The doorway had subsequently been blocked and the space formed by Structure 5 was infilled with a complex sequence of midden material rich in bone, some articulated, and burnt stone. A short passage to the north-east of the entrance had been constructed against the outer wall face of the large roundhouse (Structure 6). A wall had been constructed against the outer roundhouse wall to form a scarcement-like ledge to support lintels for the roof. The lintels, several of which were still in situ, spanned the roof to an opposing wall constructed against a large orthostat. This opposing wall incorporated a cell whose back was formed by the orthostat. The entrance to this passage had been blocked with a later wall continuing the alignment of the entrance passage. Excavation in 2018 demonstrated that there had been an upper passage using the lintels as a floor.

Structure 1, an Iron Age building dating to the 1st centuries BC/AD, was re-investigated in 2019. This building contained evidence for a stone-built oven constructed against the circumferential wall of the building and an adjacent hearth. The hearth was sampled in 2019 for archaeomagnetic dating.

Structure 1 had been badly truncated by the sea and the severity of erosion of the deposits on the area to the seaward side of this structure, indicated the need to sample the surviving stratigraphic sequence which pre-dated Structure 1 while these deposits remained in situ. The deposits were excavated stratigraphically and fully sampled for environmental remains and for dating material. The sequence produced Early Iron Age pottery containing temper-rich rim sherds with a flat splayed rim form, and a perforated seal tooth interpreted as a pendant.

The Iron Age seal tooth pendant from the Knowe of Swandro, Rousay, Orkney

The Iron Age seal tooth pendant

 

The entrance to Structure 1 to the north-west appeared to lead into a corridor that would have linked this building to the main entrance of the large roundhouse, Structure 6. This passage was in part overlain by the southern walling of the Pictish building, Structure 4.

Structure 4 appears to be a Late Iron Age agricultural building, stratigraphically post-dating Structure 1. The building was characterised by a stone-flagged floor and a hearth constructed within the northern wall, suggestive of a threshing or processing floor and corn dryer. Archaeomagnetic dating samples and samples of carbon-rich ash were taken from the bowl of the hearth.

An area to the north-east of this building was investigated and remains of midden material with bands of winkle shell not seen elsewhere within the Iron Age deposits at the site was discovered. A decorated spindle whorl made from the femoral head sawn from a cattle femur and part of a decorated bone needle case were recovered from the midden. This midden and its characteristics suggest a Late Pictish / Viking date. The midden sealed the rubble fill of another building, Structure 7. The building, as with other structural elements within this north-eastern section of the site, showed evidence of structural collapse. The collapse appears to have taken place in a short period of time and might be associated with human action rather than natural abandonment processes. The rubble infill contained some structural integrity, again suggestive of an anthropogenic origin. The walls containing this rubble infill strongly suggested that corbelling was present and that the surviving building was potentially of some height.