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Rousay, Knowe Of Swandro

Cellular Building (Pictish)(Possible), Chambered Cairn (Neolithic), Roundhouse(S) (Iron Age), Coin (9th Century)

Site Name Rousay, Knowe Of Swandro

Classification Cellular Building (Pictish)(Possible), Chambered Cairn (Neolithic), Roundhouse(S) (Iron Age), Coin (9th Century)

Canmore ID 2169

Site Number HY32NE 19

NGR HY 3753 2966

Datum OSGB36 - NGR

Permalink http://canmore.org.uk/site/2169

Ordnance Survey licence number 100057073. All rights reserved.
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Administrative Areas

  • Council Orkney Islands
  • Parish Rousay And Egilsay
  • Former Region Orkney Islands Area
  • Former District Orkney
  • Former County Orkney

Archaeology Notes

HY32NE 19 3753 2966

(HY 3752 2968) Knowe of Swandro (NR)

OS 6" map, Orkney, 2nd ed., (1900).

The much-disturbed remains of a stony mound. To judge from a series of large slabs set on edge over an area measuring roughly 72 ft by 24 ft, there may have been a group of graves here, possibly of Viking origin. 'This conjecture is to some extent supported by the fact that a typical Viking sword and a shield-boss (HY32NE 3) ... were ploughed up separately close to the site: on the onther hand, these Viking relics may have been intrusions in a previously existing structure.'

RCAHMS 1946.

Knowe of Swandro, a mutilated turf-covered mound 1.5 m. high, apparently containing the remains of a drystone structure. Unable to classify, but possibly associated with the nearby Viking hall (HY32NE 17).

Resurveyed at 1/2500.

Visited by OS (NKB), 8 June 1967.

The size and shape of this turf-covered mound suggests it to be the NE half of a broch, and a trench cut across it (but now filled in) revealed enough surviving walling to support this classification. Paving reaching from the nearby Viking hall for several yards towards this mound suggests that the mound provided a source of building material for the hall and farmstead.

Visited by OS (AA), 10 October 1972.

Activities

Publication Account (1946)

The much-disturbed remains of a stony mound. To judge from a series of large slabs set on edge over an area measuring roughly 72 ft by 24 ft, there may have been a group of graves here, possibly of Viking origin. 'This conjecture is to some extent supported by the fact that a typical Viking sword and a shield-boss (HY32NE 3) ... were ploughed up separately close to the site: on the onther hand, these Viking relics may have been intrusions in a previously existing structure.'

RCAHMS 1946.

Field Visit (8 June 1967)

Knowe of Swandro, a mutilated turf-covered mound 1.5 m. high, apparently containing the remains of a drystone structure. Unable to classify, but possibly associated with the nearby Viking hall (HY32NE 17).

Resurveyed at 1/2500.

Visited by OS (NKB) 8 June 1967

Field Visit (10 October 1972)

The size and shape of this turf-covered mound suggests it to be the NE half of a broch, and a trench cut across it (but now filled in) revealed enough surviving walling to support this classification. Paving reaching from the nearby Viking hall for several yards towards this mound suggests that the mound provided a source of building material for the hall and farmstead.

Visited by OS (AA) 10 October 1972.

Orkney Smr Note (September 1980)

Obscure: has been fancifully linked to Sweyn Asleifsson; more

likely from svin swine - Marwick Place Names of Rousay

Kirkwall 1947 p 90 suggests svin-trod swine-run.

===============================================================

... immense piles of stones, evidently the ruins of some

ancient structure, around which are to be seen graves formed with

stones set on edge ... the name of Swendrow which it bears...

[R1]

Semicircular turfed mound as described, open towards sea.

It seems a bit insubstantial for a broch and it would be

necessary to assume a lot of past erosion (not now active) to

account for destruction of seaward side. It is now 4m clear of

shoreline. Probably a prehistoric house, possibly wheelhouse

type.

Information from Orkney SMR (RGL) Sep 80.

Publication Account (2002)

HY32 8 KNOWE OF SWANDRO

HY/375297

Possible broch on Rousay I. a much disturbed stony mound which seems to contain the remains of a dry stone building, perhaps the north-east half of a broch [1]. A Viking hall is nearby [1] and a Viking sword and shield boss were ploughed up separately close to the site [1, 3, 4]. No doubt any nearby broch would have been robbed of stone for this hall.

Sources: 1. OS card HY 32 NE 19: 2. RCAHMS 1946, 2, no. 579, 220: 3. "Notes on relics of the Viking period", Proc Soc Antiq Scot, 10 (1872-74) 4. Brogger 1929, 131-2: 5. Lamb 1982, 22.

E W MacKie 2002

Excavation (23 June 2010 - 14 July 2010)

HY 3727 3037 (Brough), HY 3723 3036 (Ditch), HY 3753

2966 (Swandro) A team from the University of Bradford,

Orkney College (UHI) and City University New York cleaned,

recorded and sampled three sites from 23 June–14 July 2010

as part of the ‘Orkney – Gateway to the Atlantic Project’. The

project aims to investigate and record coastal sites in Rousay,

Egilsay and Wyre which are threatened by rising sea levels

and coastal erosion.

The Knowe of Swandro. This site which consists of a

mound with stone inclusions and is located behind a beach

on the Bay of Swandro, close to the Norse house site known

as Westness (HY32NE 17), is also thought to be Iron Age in

date. Visual examination prior to this season’s excavations

suggested that the mound is subject to coastal erosion.

The objectives for the 2010 season’s work were to locate

a reported earlier excavation trench and to characterise

the mound, which has been variously described as a

broch, a ‘mutilated turf-covered mound’ (OS 1967) and a

‘stony mound’ (RCAHMS 1946). The planned investigation

extended onto the beach rather than along the coastline as

it became obvious that the site extended under the storm

beach towards the tide line.

A small trench, 2.5 x 8m, was opened across the SE end

of the curving bank and hollow on the top of the mound.

The hollow centre of the mound, which had appeared to be

the result of earlier investigations, seems not to have been

disturbed; there was a fine and even layer of shillet sealing

this area which appeared to be a weathering deposit. A

Cleaning the erosion face of the South Howe mound tumble of rocks sealed the shillet and butted a stone feature which appeared to be structural and may be a partially destroyed length of wall. Two other small stone features may

also be fragments of walling but this cannot be determined

without more extensive excavation. There was an area of

paving composed of large, flat worn stones in the E of the

trench. This was sealed by a small patch of limpet midden in

the NE corner. The very top of an orthostat was visible in the

SE corner of the trench.

The area was cleaned, planned and photographed and the

contexts recorded. A number of conclusions can be drawn on

the basis of the evidence from this season’s work. There are a

number of phases to this part of the mound and the presence

of worn paving at the very top of the sequence, sealing or

butting an earlier wall, suggests that the site is composed of

more than a single structure. The presence of the undisturbed

shillet suggests that wherever the earlier investigations were

located, the hollow area is not the result of this but rather

represents a weathering layer over undisturbed contexts.

The tops of a series of orthostats had been noted among

the boulders and shingle of the storm beach and appeared to

be a previously unrecognised part of the site. Investigation of

these features completely changed the interpretation of the

mound. An area, c5 x 6m, stretching from the erosion bank at

the top of the beach down towards the sea was cleared. The

orthostats, which had appeared level with the boulders and

shingle, survived to a height of at least 0.5m and appeared

to form the backs and sides of three cells of a curving dry

stone structure, whose projected centre was somewhere

below the current high tide mark. The largest cell, to the

E of the feature, contained several phases of paving and

also had paving in front of a long dressed kerb stone which

formed the front of the cell. The two smaller cells to the W

also retained areas of paving and patches of ash rich midden

survived between and on top of the stones. This midden

produced well preserved bone and pottery which on initial

examination appears to be of Late Bronze Age or Early Iron

Age date. The structure appears to continue towards the high

tide mark and lies well within the area of the spring tides and

of storm events. The back of the structure was sealed by more

midden of a later date, which appeared to be earlier than

the features investigated at the top of the mound, although

this cannot be confirmed without further investigation. Bulk

samples were taken from the midden contexts within the

structure. The charred plant remains and animal bones will

provide palaeoeconomic information and radiocarbon dates.

The excavated beach area was consolidated with geotextile,

sandbags and boulders, whilst the area at the top of the

mound was backfilled and returfed.

Archive and reports: Orkney SMR and RCAHMS (intended) Digital

record: ADS (intended)

Funder: Orkney Islands Council, University of Bradford, Orkney

College and City University of New York

Archaeological Evaluation (22 July 2011 - 27 July 2011)

HY 3727 3037 (Brough) and HY 3753 2966 (Swandro) A team from the University of Bradford, Orkney College (UHI) and City University New York cleaned, recorded and sampled the site at Swandro, 22 June–27 July 2011, as part of the ‘Orkney Gateway to the Atlantic Project’. The project aims to investigate and record coastal sites in Rousay, Egilsay and Wyre which are threatened by rising sea levels and coastal erosion.

The Mound of Brough The man-made mound at ‘Brough’, also known as South Howe, on the SW shore of Rousay contains an eroding Iron Age broch and houses. These structures seem to be overlain by Late Norse buildings which in turn are overlain by 19th-century middens. This broch is only a few hundred metres away from the Broch of Midhowe.

The Knowe of Swandro Work on the Knowe of Swandro this year again concentrated on two areas, the mound itself (Area B) and the eroding beach deposits (Area A). An area 4 x 10m was deturfed on the mound and features defined. The structural elements noted in the 2010 season were investigated and appear to be the remains of a substantial double faced curving wall. A small area of paving close to the beach section appears to be later in date.

On the storm beach, the cleared area was extended to 4 x 10m, to assess the extent of the remaining deposits. Midden and other features were found to extend to the high tide mark and further test pitting at low tide revealed that anthropogenic deposits stretched under the storm beach and sand deposits to the low tide line. A sondage in the E corner of the excavated area showed a complex series of stony midden deposits to a depth of >1.5m below the eroded surface; at this depth, a freshwater spring made excavation difficult, but the sondage demonstrates the depth of midden deposits under the eroding beach. Finds from these middens include a worked bone pin, pottery and well preserved bone.

The remains of a prehistoric structure, first investigated last year, were further excavated and samples taken for environmental evidence and radiocarbon dating. A single radiocarbon date indicated a date in the 1st to 2nd century AD. Archaeomagnetic dates obtained from an earlier hearth indicate use in the 4th to 2nd centuries BC.

Clearance of large beach boulders on the W edge of Area A revealed large dressed stones, much battered by the storm beach, forming a substantial wall which could be shown to be the continuation of the large curving wall seen in Area B.

Stratigraphically above the structure excavated last year, and physically further up the beach, a paved area, a fragment of hearth surround and a series of cells formed from orthostats indicated the presence of a later structure. The evidence suggests that Swandro is a multi-period settlement.

This years excavations have demonstrated that the deposits at Swandro are much deeper than initially suspected and the extent of the site much greater. Marine erosion has proceeded in a stepped fashion, so that the earliest deposits survive in greatest extent below the storm beach, whilst the later deposits are fragmentary.

Archive and reports: Orkney SMR and RCAHMS (intended). Digital record: ADS (intended)

Funder: Orkney Islands Council, University of Bradford, Orkney College and City University of New York

University of Bradford/ Orkney College, 2011

Archaeological Evaluation (20 June 2012 - 19 July 2012)

HY 3753 2966 (Swandro) A team from the University of Bradford, Orkney College (UHI), William Paterson University and City University New York cleaned, recorded and sampled the site at Swandro, 20 June – 19 July 2012, as part of the ‘Orkney – Gateway to the Atlantic Project’. The project aims to investigate and record coastal sites in Rousay, Egilsay and Wyre which are threatened by rising sea levels and coastal erosion.

The Beach The investigation of odd stones just visible among the pebbles on the beach below the eroding site has completely changed our understanding of this enigmatic mound. Initial clearance of the overlying beach material revealed the remains of an Iron Age structure. This was confirmed by an AMS radiocarbon date of 25BC-AD130 at 95% confidence for carbonised barley from a midden which sealed flagging in one of the compartments. Work in 2011 (DES 2011, 136–7) enabled the nature of the erosion to be more fully understood together with an indication of archaeological survival and potential. The sea had created terraces or steps within the archaeological mound, with each of these eroded scars being covered by redeposited beach material.

In 2011, on the NW western side of the cleared archaeological surface, the remains of a substantial outer wall forming the arc of a large circular building seemed to form the continuation of a crescent shaped ridge at the top of the mound, and it was thought to be the outer wall of a large roundhouse of broch proportions.

A Chambered Cairn? In 2012 this substantial wall was investigated more fully; clearance of the overlying beach material revealed a circular structure. This was formed by a number of concentric outer wall faces. Each arc of wall was backed by a stone and midden core. Rather than the expected broch, the structure of this monument more closely parallels the construction of a Neolithic chambered tomb. A wall running eastwards is suggestive of an outer-work leading into an entrance passage. Cutting into and sealing the top of this enigmatic monument were further Iron Age buildings represented by truncated flag floors and orthostats.

Despite aggressive erosion, shown by the worn outer faces of the walls which have been battered by the sea and the constant movement of the boulder beach, this probable chambered cairn still remains intact, and has great archaeological potential.

The excavation of the seaward outer rings proved difficult, as the sea would cover these at high tide and work had to be timed to coincide with low tides, after substantial amounts of bailing. Bone from the Iron Age middens and between the concentric walls of the cairn survives well even in areas truncated by the sea. This means that the potential for in situ human remains within the tomb is high and in consequence this is an extremely important site. Re-evaluation of existing tomb assemblages are currently challenging previously held interpretations. This site offers the rare opportunity to excavate using modern methods and techniques, a tomb which in a few years time will be completely lost to the Atlantic.

Work to the SE in 2012 saw the continuation of Late Iron Age walling on the foreshore under the boulder beach and now indicates that the Norse Hall overlies earlier settlement material.

This year’s excavations have demonstrated that the deposits at Swandro are more extensive and the deeper deposits are much earlier than initially suspected.

Archive and report: Orkney SMR and RCAHMS (intended). Digital records: ADS

Funder: Orkney Islands Council, University of Bradford, Orkney College, City University of New York and William Patterson University

SJ Dockrill, University of Bradford

JM Bond, Orkney College

J Downes,

IL Mainland,

R Maher,

2012

Archaeological Evaluation (23 June 2013 - 19 July 2013)

HY 3753 2966 A team from the University of Bradford, Orkney College (UHI), William Paterson University and City University New York cleaned, recorded and sampled the site at Swandro, 23 June – 19 July 2013, as part of the ‘Orkney – Gateway to the Atlantic Project’. The project aims to investigate and record coastal sites in Rousay, Egilsay and Wyre which are threatened by rising sea levels and coastal erosion. Work on the Knowe of Swandro this year again concentrated on two areas, the mound itself and the eroding beach deposits.

In the first season of the project, upright stones just visible among the pebbles on the beach below the eroding site were investigated and proved to be part of a series of structures and features surviving beneath the storm beach (DES 2010, 123). Subsequent investigation of this area has completely changed our understanding of this enigmatic mound.

Initial clearance of the overlying beach material revealed the remains of what appeared to be an Iron Age structure. This was confirmed by an AMS radiocarbon date of 25BC–AD130 at 95% confidence for carbonised barley from a midden that sealed flagging in one of the compartments. Work in 2012 (DES 2012, 135) enabled the nature of the erosion to be more fully understood, indicating significant archaeological survival and potential. It can now be seen that the sea has created terraces or steps within the archaeological mound, with each of these eroded scars being covered by redeposited beach material.

In 2011 on the NW side of the cleared surface, the remains of a substantial and well built outer wall forming the arc of a large circular building were revealed.Further clearance of the beach material in 2012 showed that there was a series of three substantial concentric outward facing walls, and the structure appears to be a Neolithic chambered cairn, surrounded by later settlement.

Work in 2013 concentrated on the continuation of the site to the SE of the mound, extending towards the Norse house site known as Westness. Investigation this year has demonstrated a Late Iron Age and Pictish phase of Swandro, indicated by cellular structures contained by the infilled remains of more substantial Iron Age structures. Material recovered from these structures included fragments of glass and copper alloy, hammer scale, slag, vitrified material and a small copper alloy projecting-headed pin. It can now be seen that the truncated remains of the Norse hall of Westness clearly overlie the Swandro Late Iron Age settlement.

On the beach close to the chambered cairn, the truncated remains of the earliest Iron Age building (Structure 1) were further investigated and found to contain an orthostat and stone construction interpreted as an oven. This feature has a close parallel with the 1st century BC oven excavated by the authors in Structure 8 at Old Scatness, Shetland.

Excavation of the shoreward part of the Swandro mound continued in 2013 and indicated that stone from the upper parts of the Neolithic chambered cairn had been robbed in antiquity. Excavation identified shillet and midden deposits in this area of disturbance, though the date of this activity has not yet been established.

Archive and report: Orkney HER and RCAHMS (intended). Digital records: ADS

Funder: Orkney Islands Council, University of Bradford, Orkney College, City University of New York and William Patterson University

SJ Dockrill and JM Bond, University of Bradford and R Maher, Orkney College, 2013

(Source: DES)

Archaeological Evaluation (16 June 2014 - 26 July 2014)

HY 3753 2966 A team from the University of Bradford, Orkney College (UHI), William Paterson University and City University New York cleaned, recorded and sampled the site at Swandro, 16 June – 26 July 2014, as part of the Orkney Gateway to the Atlantic Project. The project aims to investigate and record coastal sites in Rousay, Egilsay and Wyre which are threatened by rising sea levels and coastal erosion.

Work in 2014 focused on the beach where investigation of set orthostatic stones just visible among the pebbles on the beach indicated archaeological survival below the eroding site. Investigation of these features has completely changed our understanding of this enigmatic mound. Initial clearance of the overlying beach material revealed the remains of an Iron Age structure. This was confirmed by an AMS radiocarbon date of 25BC-AD130 at 95% confidence for carbonized barley from a midden which sealed flagging in one of the compartments.

Work in 2012 enabled the nature of the erosion to be more fully understood, indicating significant archaeological survival and potential. The sea had created terraces or steps within the archaeological mound, with each of these eroded scars being covered by redeposited beach material. In 2012 on the NW side of the cleared archaeological surface the remains of a substantial outer wall forming the arc of a large circular

building seemed to be the continuation of a crescent shaped ridge at the top of the mound. It was thought at first that this was the outer wall of a large roundhouse of broch proportions. However, the presence of a series of stepped concentric outer wall-faces with a mixed midden and rubble core suggests that the core of the mound is a Neolithic chambered cairn.

Work in 2013 concentrated on the continuation of the site SE of the mound. Investigation demonstrated that a Pictish phase, indicated by cellular structures contained within the infilled remains of more substantial Iron Age structures, show a continuation of the site on the foreshore and under

the boulder beach. The truncated remains of the ‘Norse Hall’ of Westness, previously excavated by Kaland (1993), clearly overlies the Late Iron Age settlement.

Excavation of the centre of the Swandro mound continued in 2014 and this now clearly indicates that the mound forming the Neolithic chambered cairn had been partially robbed in the Iron Age and infilled with Late Iron Age (Pictish) midden. On the seaward area of the beach under the mound, the truncated building (Structure 1) was further investigated and midden was found to continue seaward, but was clearly affected by the tidal action.

Work was concentrated on the excavation of the later Iron Age (Pictish) elements of the site. Here buildings were found to be nested in larger structures which had been truncated by the sea. The truncations were cleaned as sections, sampled and recorded. The excavation of one of these later truncated buildings (Structure 2) saw the sampling of floor surfaces down to the primary flag floor. The continued excavation and

sampling of the infill of a third building (Structure 3), close to the Westness houses, but partly within the eroding beach area, confirmed its form as a Pictish style multi-cellular building and revealed the presence of slag and crucible material suggesting copper alloy working in the deliberately deposited infill.

One of the larger structures into which the later structures are nested became clearer during this season’s excavation, with a substantial wall in the erosion section and a series of paved surfaces butting the wall on the outside face of the curve. A feature consisting of a set of paving slabs which had cracked and tipped downwards appears to be related to this

structure. When the flags were removed what appears to be a well was revealed, with dry stone walls, a flagged area around the top and a set of steps inside. When some of the rubble was removed it was found that the well was still active, refilling to the base of the steps with spring water.

Archive and report: Orkney SMR and RCAHMS. Digital records: ADS

Funder: Orkney Islands Council, University of Bradford, Orkney College, City University of New York and William Patterson University

SJ Dockrill, JM Bond and R Maher – University of Bradford (SJD/JMB) and Orkney College (RM)

(Source: DES)

Excavation (16 June 2015 - 26 July 2015)

HY 3753 2966 A team from the University of Bradford, Orkney College (UHI), William Paterson University and City University New York cleaned, recorded and sampled the site at Swandro, 16 June – 26 July 2015, as part of the Orkney Gateway to the Atlantic Project. The team included students,

freelance archaeologists and academics. The project aims to investigate and record coastal sites in Rousay, Egilsay and Wyre which are threatened by rising sea levels and coastal erosion.

Excavations at Swandro in 2015 saw a continuation of the work on the terraced beach with the further examination of the eroded Iron Age buildings investigated in the previous year. Structure 3, a Pictish building at the top of the series of eroded terraces, continued to be excavated with further signs of metalworking debris consisting of slag, furnace lining and crucible fragments being found. These infilling deposits were sampled and have high potential for botanical remains in the light fraction recovered from flotation. It now appears that the construction of the main Norse house excavated by Sigrid Kaland (1993) destroyed the eastern part of this structure, though the infill deposits may be earlier than this. To the W there seems to be a short passage leading out of the structure, with two possible steps. Further definition of other structural remains took place all along the upper terrace.

The Neolithic chambered cairn on the western boundary of the Iron Age site was uncovered to assess the tidal damage to the remains. This area was originally uncovered in 2012 and the structure of the cairn determined before being carefully recovered. However, observations last year suggested that

the large boulders had again shifted and that the outer of the casement walls was eroding. Excavation of the overlying beach and removal of the membrane laid down in 2012 showed an alarming amount of attrition to the monument. The stones forming the seaward part of the outer casement had been

rounded by the sea and much of the retained material had been washed out. The other casement walls also seem to be tipping seawards. This summer saw a lot of rainfall and a spring developed at the foot of the cairn draining towards the sea which may be hastening the erosion. The monument was

fully scanned using a 3D scanner by Dr A Wilson (University of Bradford), and aerial photos were taken (using a drone) by Robert Friel and Lindsey Kemp.

The passage entranceway on the E side of the tomb was located this season; two parallel wall faces lead through the cairn wall and are continued by a further wall which butts the outer casement walls of the cairn. It seems likely that this passage originally continued to the E but whether it was destroyed by Iron Age activity or continues in fragmentary form under the Iron Age structures which surround this side of the cairn is not yet known. This passageway has been deliberately filled with rubble and fine earth; a fragment of copper alloy and bone fragments, human and animal, were found in the top of the fill, but no further excavation took place on these deposits. Further investigation is needed to elucidate this relationship. Further excavation is planned for 2016.

Archive and report: ADS, National Record of the Historic Environment and Orkney SMR

Funder: Orkney Islands Council, Orkney Archaeological Society, University of Bradford, Orkney College, City University of New York and William Patterson University

SJ Dockrill, JM Bond, R Maher and R Friel – University of Bradford and Orkney College

(Source: DES, Volume 16)

Excavation (July 2016)

HY 3753 2966 (HY32NE 19) Evaluative excavation continued in July 2016. The archaeology is suffering from erosion from the sea which has cut into a settlement mound (Iron Age to Norse) developed upon the eastern flank of a Neolithic chambered cairn. 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 midden material having been washed away and the larger structural stones having been smoothed by the movement of water and beach material.

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 redeposited, implying the movement of large ‘storm thrown’ rocks. These sealed a dark yellow sand and a black compacted sand

containing decayed seaweed with no surviving evidence of any anthropogenic deposits or an in situ old ground surface.

Despite this sequence of redeposited material in the scoured area seawards of the cairn wall, the remains of a reddish ashy midden deposit was found to be sealed by the secondary retaining wall.

The entrance passage leading into the chambered cairn was also 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 bones appeared to reflect late activity. This was confirmed by the finding in post-excavation of a coin of EANRED, King of Northumbria AD810–840, together with the near complete skeleton of a cat. This disturbance and infilling might 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 of several sheep displaying metal butchery marks. This deposit sealed large angular rubble which appears to be the infill of the passage.

Structure 1: A truncated Mid Iron Age roundhouse – This roundhouse is represented by just one segment of its circumferential cells, the interior and southern portion having been lost to the sea. The circumference of the building is formed by orthostats; the floor of the northern radial cell was

formed by a single flag, which had been made to fit the cell.

Several notches had been cut into the flag, which appear to be post settings. It seems likely that this would have supported a mezzanine level around the circumference of the structure.

The presence of such mezzanine structures is paralleled by Middle Iron Age remains at Old Scatness, Shetland.

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 found to be 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. A floor level was formed by large flags with evidence of orthostatic radial divisions. Entering this

structure via the threshold stone, one of these radial orthostats blocks any turn to the left (north/landward side), confining movement to the centre or to the right. This phenomenon of barring entry to the left has also been observed within other Iron Age roundhouse structures in the Northern Isles at Old Scatness (Shetland). 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.

Structure 3 – 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. 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 was found to lead from the N (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 and the central area of the structure.

Archive: NRHE

Funder: Orkney Islands Council, University of Bradford, and Rousay Development Trust

JM Bond, SJ Dockrill and J Downes – University of Bradford and

Archaeology Institute, UHI

(Source: DES, Volume 17)

Excavation (July 2017)

HY 3753 2966 (HY32NE 19) Evaluative excavation continued upon the eroding beach at Swandro for a four week season in July 2017. The archaeology is suffering from erosion from the sea which has cut into a settlement mound (Mid Iron Age to Norse) developed upon the eastern flank of a Neolithic chambered cairn. 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 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 SE 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 redeposited, 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 predating 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 chambered cairn.

The entrance passage leading into the chambered cairn 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 AD810–840, 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.

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 AD348–350, was found.

Structure 3 – 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 metalworking 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 N (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 metalworking including part of a fired clay tuyère. 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.

Archive: NRHE

Funder: Orkney Islands Council, University of Bradford, Rousay Development Trust, Rousay Heritage Trust, Swandro Orkney Coastal Archaeology Trust, and Orkney Archaeological Society

JM Bond and SJ Dockrill – University of Bradford/Archaeology Institute, UHI

(Source: DES, Volume 18)

Geophysical Survey (16 April 2018 - 26 April 2018)

HY 37051 30722 (North Howe), HY 37274 30377 (South Howe), HY 37352 29774 (Knowe of Rowiegar), HY 37531 29661 (Knowe of Swandro), HY 37626 29296 (Westness Viking Houses), HY 4398 3224 (Rinyo) and HY 40065 27452 (Burrian)

The RGK undertook a survey campaign on Rousay, 16 – 26 April 2018, as part of the Boyne to Brodgar Project. It aimed to provide a landscape perspective of two Neolithic core areas on the island – Westside and Rinyo. Moreover, the diachronic development in both areas will be researched, concentrating on the processes of formation and degradation of land use over time.

At Westside the survey area stretched from Westness Farm in the S to the rugged area N of North Howe, where the rocky surface and shrubbery prevented further activity (c56ha). The survey focused on the lower fields close to the coast and to the known Neolithic chambered cairns of Knowe of Swandro, Knowe of Rowiegar and Mid Howe. Some fields had to be omitted because the device could not drive across their steep slopes and rocky ground. Several new anthropogenic anomalies and structures can be observed in the imagery. In the SE field of the surveyed area a possible new mound is most striking. A circular structure, 9.5m in diameter, of high magnetic susceptibility was evident about 250m NW of the mound. In the N further settlement structures surrounding North Howe Broch have been revealed. Track-like linear structures follow downhill from the N towards the SW, and E of these, and NW of North Howe several possible settlement structures are evident. Three circular roundhouse structures are located 20m N of the broch, their diameter is between 8.5 and 11m. Immediately W of North Howe a concentration of stone might result from broch related debris, but could also reveal remains of further building activity in this location. Further investigations will hopefully reveal details about the chronology and function of some of the anomaly clusters.

The Neolithic settlement of Rinyo is positioned in a valley between Faraclet Head and Kierfea Hill in the N of Rousay. During the survey, 50.5ha of gradiometer data were captured from fields surrounding Bigland and Houseby Farms in the S of the valley. The NW area of the survey showed traces of ploughing and some field boundaries. Apart from the interior structuring of Rinyo settlement site several new features have been identified in the adjacent fields to the N and S. A circular to oval structure of 20 – 22m in diameter is positioned about 40m NW of Rinyo’s extent. Inside the settlement, internal details can be identified, and the magnetic susceptibility of the structure is relatively high with values up to 18.0 nT. In the field SE of Rinyo, a cluster of several structures is evident. Several circular and semi-circular features with diameters between 12 – 22m, as well as linear anomalies, signify a focus of settlement activity. About 100m SE of the modern Bigland Farm a further nucleus of settlement or burial activity of uncertain date and type was found. A linear structure in the SW of the surveyed area could result from an igneous dyke. Several anthropogenic anomalies can be found around the dyke.

Two fields were surveyed N of Burrian Broch on the S coast of Rousay. Part of the broch has eroded into the sea and the part facing the coast was not accessible with the 3m rig. The N part of the cavity wall and the possible outer boundary ditch are visible in the magnetometry data. The fields contain dipole anomalies, probably resulting from modern metal waste. Some faint traces of rig and furrow-like features can be detected in the areas close to the coast. Several linear features of higher magnetic susceptibility may also be of modern origin (heavily burnt material was visible on the ground surface).

This report highlights some of the larger structures brought to light with the surveys. Many further features, visible of in the imagery, are still undergoing analysis, and more complementary work is needed to further identify their function and chronology, and their meaning in the composite usage of the land.

Gradiometer survey was predominantly conducted with a GPS-supported 14-sensor fluxgate GM650B gradiometer device mounted on a quad-drawn 3m wide rig. At Westside, the fields close to the sea were not accessible with the large rig. These were surveyed with a 2m rig mounted with five sensors with a similar technical configuration to the larger one.

The works were carried out in collaboration with the University of the Highlands and Islands Archaeology Institute, Orkney College, County Archaeologist Julie Gibson, Orkney Islands Council, the National Museum of Scotland and University College Dublin.

All survey results are reported to Historic Environment Scotland and the Rousay Community

Funder: RGK

Ruth Beusing and Knut Rassmann – Römisch-Germanische Kommission, Frankfurt (RGK) of the German Archaeological Institut (Deutsches Archäologisches Institut)

(Source DES Volume 19)

Excavation (25 June 2018 - 3 August 2018)

HY 37531 29661 The 25 June – 3 August 2018 season saw the completion of the excavation of the Pictish Building (Structure 3) and the start of a new phase of the project with the excavation of the suspected chambered cairn forming the Knowe of Swandro.

The Pictish building floor had been identified in 2017 and revealed significant metalworking debris suggesting both iron and copper working, with spheroidal slag and hammer scale suggestive of sophisticated blacksmithing including fire welding. The presence of a number of crucible fragments strongly pointed to the structure having been used for copper alloy working. Subsequent analysis of the crucible fragments by Dr Gerry McDonnell using X-Ray Fluorescence (XRF) indicated that the crucible fragments were used to cast an alloy with a high zinc composition forming a brass rather than a bronze (with a higher tin content in the alloy). In the summer of 2018 Dr McDonnell supervised the excavation and sampling of the floor of the Pictish building. The floor was carbon rich and the hearth demonstrated two phases of use. In between the upper hearth fragment and the lower primary hearth a further fragment of crucible was found. The excavation revealed further evidence of metalworking, with crucible fragments and the remains of several fragments of fired clay from a tuyère, which would have protected the snout of the bellows. Magnetic susceptibility and XRF survey of the floor, together with the in situ remains of the furnishings of the building, have provided a unique understanding of the use of space within the structure.

The building was clearly semi-subterranean in nature, with a shallow set of steps leading into a passage flanked on the left hand side by the wall of the structure and by a large orthostatic slab on the opposing side. A door would have opened into Structure 3, the doorway being defined by an in situ threshold stone and door pivot. Anyone entering the building would have to enter to the left (clockwise) of the hearth and its back-slab that would have protected the hearth from drafts. The strongest signatures of copper working determined by the detailed XRF analysis of the floor surface indicated the working position of the smith would have been on the left hand side of hearth, facing the doorway and hearth back-slab and in front of two beach cobbles set into the floor. These cobbles, one an elongated block and the other smaller and squarer in shape, had clear percussion damage indicating their use as anvils. Whilst preparing to illustrate the larger cobble, archaeological illustrator Mr Alan Braby noted carbon staining appearing to represent the finger or hand marks of the smith. McDonnell's survey of the floor and the presence of the tuyère fragments suggest the bellows were located on the opposite (right hand) side of the hearth. A cupboard or aumbry constructed within the wall of building would have been to the left of the smith and may have been used either as storage or the location of a lamp. The layout and sophisticated design of the building strongly suggests that this was a purpose-built smithy. The hearth furnishings seem to have been constructed as part of the building’s primary usage. The semi-subterranean nature of the building and the location of the doorway formed an effective means of reducing natural light. Added to this, the doorway presented clear evidence of two means of barring the door, one from the inside, further reducing any light incursion. The observation of flame colour by the smith would have been critical to enable them to gauge metal temperature. It is worth noting that a second bar hole was present, indicating that the door could also be secured from the outside.

This metalworking building (Structure 3) had been constructed within two parallel single-faced stone walls that had in previous years suggested the presence of an earlier building. Further investigation in 2018 suggested that this earlier stonework actually represented the stone revetments of a ditch. The fill of this suspected ditch below the ash and carbon-rich floors of the Pictish smithy had been compromised by the tidal action of the sea, consisting of vacuous rubble with lenses of beach sand. A small fragment of plastic was observed within this material, but the layers of floor above this fill were intact and undamaged. The pressure of the sea from tidal and storm surges appears to have horizontally penetrated the archaeology below Structure 3, removing finer archaeological sediments. This erosive action has affected the walling of Structure 3 (the Pictish smithy) on the seaward side and seems to be responsible for the subsidence of the wall into the top of the infilled ditch.

This year, excavation commenced on a new area encompassing the central zone of the Neolithic chambered cairn. The cairn was revealed in previous investigations in 2012 and 2015 as a series of casement walls and packed core under the boulder beach around the high tide line. The new area included the entrance first identified in 2016 and further defined in 2017; it also took in a new area on the landward side of the entrance. Excavation revealed a complex sequence in contrast to the eroded sequence investigated under the boulder beach in 2012 and 2015. Excavation in 2018 within this landward zone indicated a structural sequence that was secondary to the monumental structure interpreted as being the Neolithic Passage Grave. This structural sequence consisted of a roundhouse form (Structure 6) which had been inserted into the monumental structure, re-using and extending the original entrance passage. The structure was represented by an inner-faced wall with a difference in alignment to the earlier casement walling. This roundhouse appears to have had a complicated History of collapse, rebuilding and use, being subdivided by later structural elements characteristic of the late Iron Age or Pictish period. This late phase was represented by a dividing wall and orthostatic alignment forming a large inner cell on the landward side of the passage (Structure 5) with a doorway that had later been blocked by stone walling. The preservation in this area suggested a complex sequence of modification, with a deep stratigraphic sequence surviving. An infill of mixed midden material, rich in animal bone and pottery, was recorded inside this cell whilst outside the wall and blocked doorway there was evidence of more than one structural collapse of the roundhouse, the latest involving the fall of very large orthostats, one of which lay against the blocked doorway. Several of these elements suggested the collapse of corbelled roofing structures. This new exposure of the inner end of the passage provided evidence of structural collapse. Two long and substantial stone slabs just under 2m in length were found lying along the axis of the passage and partly inside the roundhouse. These stones might represent either a pair of fallen orthostats or uprights, or possibly lintels associated with the roofing of the passage. If these stones were set upright they would coincide with a change in width and orientation of the passage at the point where the secondary Iron Age roundhouse was inserted.

The removal of the boulder beach overburden of the area of cairn previously assessed was deeper than expected and indicated that the archaeology here had been badly truncated by the sea. The area at the top of the boulder beach which had been exposed in 2015 had suffered greatly in the intervening years despite the archaeology being covered; much of the finer sediments had been washed out, the survival of archaeological sediment-based deposits was poor and in contrast to the material on the landward side. The suction of the finer deposits caused by the receding tide seems to be the main cause of this. This effect seems consistent with the evidence for Structure 3 discussed above. Very little of the tertiary Pictish deposits survived the aggressive action of the sea in this zone.

Within this eroded zone of the cairn a stone cist was identified. The fill of the cist had been completely scoured out by wave action and entirely replaced by beach deposit. However, a fragment of steatite vessel was found on the surface of the archaeological deposits just below the cist. This fragment appears to be Bronze Age rather than Norse in character and suggests the possibility of a Bronze Age use of the cairn. Adjacent to this cist the top of a corbelled cell was identified, possibly representing part of a side chamber to the cairn. This feature was recorded and carefully packed and will be fully investigated next year.

Outside the wall of the cairn, a corridor-like structure had been identified in 2017. This structure was built against the outer wall face with several in situ lintels set upon two scarcement-like ledges. The extended excavation area allowed more of this structure to be investigated. The excavation revealed further parts of this corridor, which appears to have at least two major phases of construction with its secondary and latest use dating to the Pictish period. A poorly-constructed single-faced wall formed the end of this secondary passage. This single-faced wall stratigraphically sealed an earlier and better-constructed corbelled wall associated with the ledges and lintels. The backing material to both of these end walls was composed of midden, including a layer rich in limpets and pottery. Two sequences of backing material corresponding to the two phases were identified. The lower fill sealed the top of the corbelled end to the lintelled corridor. A series of slabs at a 60-70° angle appeared to represent structural elements consistent with the collapse of a corbelled roof; they sealed the material backing the secondary and poorly-constructed single-faced wall.

The opposing long wall of the secondary use of this corridor was formed by several large orthostats. These orthostats were backed by a mixed midden-like infill, which was contained by a much earlier well-constructed wall of a distinctly different build. This earlier wall had been truncated by the construction of Structure 4, a Pictish building partly excavated in 2015 during the evaluation of the eroded beach section. Excavation of Structures 5 and 6 and the primary cairn will continue in 2019.

Archive and report: Orkney HER and NRHE (intended). Digital records: ADS (intended)

Funder: Historic Environment Scotland, Swandro Orkney Coastal Archaeology Trust, Orkney Islands Council, University of Bradford and Orkney Archaeological Society

JM Bond and SJ Dockrill – University of Bradford

(Source DES Volume 19)

Excavation (June 2019 - August 2019)

HY 37531 29661 Excavation, in June to August 2019, concentrated on the remains of the large Iron Age roundhouse (Structure 6; Canmore ID: 2169) and the adjacent area to the SE 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.

Investigation of the passageway into Structure 6 showed at least two structural phases. A cladding wall thickening the 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.

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 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 NE 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 entrance to Structure 1 to the NW 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 NE 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.

Archive: Orkney HER, NRHE, Digital records will be deposited with ADS. Artefacts to be deposited with the Orkney Museum (if agreed by the Treasure Trove Unit)

Funder: HES, Swandro-Orkney Coastal Archaeology Trust, Orkney Islands Council, University of Bradford, Orkney Archaeological Society

JM Bond and SJ Dockrill ̶ School of Archaeological and Forensic Sciences, University of Bradford

(Source: DES Vol 20)

Geophysical Survey (June 2019)

HY 37531 29661 A geophysical survey around the Knowe of Swandro (Canmore ID: 2169) was carried out to assist and help with the interpretation of the on-going excavations at the site. The surveys were carried out at the start of the 2019 excavation season and build upon previous surveys carried out in the area (DES 2010, 123–4; DES 2011, 136–7; DES 2012, 135–6; DES 2013, 141–2; DES 2014, 149; DES 2015, 131–2; DES 2016, 131–2; DES 2017, 146–7; Full excavation: DES 2018, 149¬-51). The current surveys took place June to August 2019, and were carried out on the landward side of the site, which currently is not affected by the effects of erosion as is the rest of the site, but the proximity to the sea has meant the salinity of the soil has impacted the depth at which some techniques used could ‘see’. Aware of this potential problem from the start, fieldwork was carried out using a number of integrated geophysical survey techniques including detailed earth resistance survey (Geoscan Research Twin-Probe), electromagnetic survey (GF Instruments CMD-Mini-Explorer), Ground Penetrating Radar (Mala X3M) and Electrical Tomography (ZZGeo FlashRES64). These techniques allow data to be collected at multiple depths to allow for a better understanding of this multi-phase/multi period site.

The earth resistance data was collected using the twin probe array, and collected data using Geoscan Research's RM-85 electrical resistance meter. Data was collected over the same grid as used for all the other surveys. Within the 20 x 20m data grids data were collected at 1 x 0.5m intervals and at three different depths (0.5, 1.0 and 1.5m separation).

Electrical Resistivity Tomography (ERT) was collected on the Knowe of Swandro in parallel traverses with their positions, where recorded, in x,y and height to allow the data to be topographically corrected. ERT is a technique that allows a vertical section through the ground to be investigated. The instrument used was a multi-channel, free-configuration system. The FlashRes64 system is not constrained by any one electrode array and undertakes a resistivity imaging survey by recording as many combinations of potential measurements as possible simultaneously, from a set pair of current electrodes which change position at each measurement station.

The ERT was used to build pseudo-sections (PS) along lines with a probe distance of 0.25m. These PS are then converted from ‘measured’ to ‘model’ resistivity via an inversion system which produces interpretable sections.

The Electromagnetic data was collected using CMD Mini-Explorer produced by GF Instruments. The instrument generates an EM signal which in turn generates new signals from the subsurface which are then measured.

The ground penetrating radar (GPR) was collected using a wheeled cart with an encoder wheel to position the GPR data along the traverses, the data was collected using a 250MHz antenna.

All the geophysical survey grids and the control used for the excavation have been located onto the Ordinance Survey Grid (OS) using OSTN15 via Trimble’s VRS Now network using Trimble R10 GPS and Lecia Total Station.

The data collected from the GPR proved to be ambiguous. Although showing archaeology concentrated around the physical mound of the Knowe of Swandro, a true reflection of depth at present is difficult to determine due to the problems associated with saline water.

The traverses using the ERT were extremely successful, indicating the depth and extent of the archaeology, and confirming the focus of settlement on the coastal strip. More importantly, in terms of future management and understanding, it indicated the presence of water within the lower archaeological contexts.

The detailed earth resistance survey indicated that the large roundhouse forming the main component of the Knowe of Swandro was surrounded by subsidiary buildings suggesting a nucleated village.

Archive: NRHE and Orkney HER (intended)

Funder: Historic Environment Scotland, Swandro-Orkney Coastal Archaeology Trust, Orkney Islands Council, University of Bradford, Orkney Archaeological Society

C Gaffney and T Sparrow - School of Archaeological and Forensic Sciences, University of Bradford

(Source: DES Vol 20)

References

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