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19 Aug 2020

Beyond the boundary

Written by Derek Alexander, Head of Archaeological Services
Archaeologists digging a trench in a field on Iona in front of the abbey, under a blue, cloudless sky.
Excavating in the field south of the abbey
From the 20th-century remains of rusting machinery at the marble quarry to flakes of flint from Mesolithic hunter-gatherers, there’s more to Iona’s past than just the abbey.

Since Columba arrived on Iona with his followers in AD563, the site of the abbey has formed the focal point of the island. Columba’s monastic settlement would have been built of timber and earth, with a number of carved stone crosses, and it continued in use despite intermittent Viking raids from AD795 onwards. The stone church you see today was part of the Benedictine abbey of 1200. This fell into ruins after the Reformation, but was rebuilt in the first half of the 20th century as part of a major conservation project. During these rebuilding works a wide range of archaeological investigations were carried out around the abbey.

An archaeologist with geophysical equipment surveying a field on Iona in front of the abbey.
Undertaking geophysical survey around the abbey

Professor Charles Thomas carried out one of the largest programmes of investigation from 1953–63, when around 100 small trenches were excavated. The results of this work have recently been pulled together by archaeologists from Glasgow University and form an incredible overview of the site. Perhaps the most significant revelation from this work was the new radiocarbon dates from the remains of a wicker hut on Torr an Abba, which confirmed it belonged to the 6th century and could have been Columba’s cell!

An archaeologist in a hi-vis jacket recording a section of an archaeological trench with large stones sticking out of it.
Archaeologists from the University of Glasgow excavating across the monastic vallum bank.

Over the last 15 years, the National Trust for Scotland has been undertaking small-scale investigations outside the immediate confines of the abbey ruins. Using a grant from Historic Environment Scotland, we commissioned a geophysical survey of the fields to the north and south of the abbey, which revealed the lines of multiple ditches. These ditches would have formed the vallum (a ditch and bank), which would have delimited the sacred space around the monastic complex. On Trust land, an earlier trench across the vallum ditch to the west of the abbey was re-excavated by the Glasgow University team, as was a trench across a rectilinear enclosure visible on the geophysical survey results, close to the ruins of St Mary’s Chapel. The enclosure proved to be post-medieval in date and sat on the east side of the road that approached the abbey in the 18th century.

Archaeologists digging a trench in a field on Iona in front of the abbey, under a blue, cloudless sky.
Thistle Camp participants excavating in the field to the south of the abbey in advance of ground source heat system.

As part of a National Trust for Scotland Thistle Camp, volunteers and participants excavated 10 test pits in an area proposed for a community ground source heat system to evaluate it for archaeological remains. Although no structural remains were encountered, we recovered quite a large collection of artefacts including over 100 sherds of post-medieval craggan ware, highlighting that the area was occupied even when the abbey was in ruins.

Two archaeologists sieving soil to search for artefacts.
Sieving for Mesolithic and Neolithic flints close to the Village Hall

To the south of the village, we found a wide range of archaeological deposits through geophysical survey and excavation, including a concentration of flints within and below the deep ploughsoil close to the Village Hall. When examined, these flints showed at least two phases of activity: the first in the late Mesolithic around 7,000 years ago, and the second in the Early Neolithic from 5–6,000 years ago. The former is the earliest evidence for human activity on Iona and the flints would have been used by mobile hunter-gatherer groups, perhaps making seasonal use of the island’s varied resources.

Archaeologists digging a shallow rectangular trench in a field on Iona. A number of features have been uncovered in the trench.
Digging the rectangular features at Martyr’s Bay

Further south, in Martyr’s Bay, an area of disturbed ground appeared on the geophysical survey. Here, Thistle Camp participants excavated trenches and found a mixed range of artefacts including a copper-alloy coin of Charles I (1625–46), pottery and flint. An area of intercutting, rectangular spade-dug pits looked like they might have been graves but no human remains were identified. Two copper-alloy pins were also found and one dates to the 10th or 11th century AD. This is one of a number of Hiberno-Norse pins that have been found on Iona in the last few years, and evidence that the island continued to attract people even after the Viking raids of the late 8th and early 9th centuries.

The archaeological features were cut into a layer of hazel charcoal, from which a sample was submitted for radiocarbon dating, and this gave us perhaps the biggest surprise in this excavation. The results came back as AD428–600, which covers the period that Columba came to the island, and is one of the few dates from this period from outside the focus of the monastic complex.

A metal pin is displayed against a plain background. A 5cm measuring stick lies beneath the pin.
Hiberno-Norse copper alloy pin, 10th-11th century AD

In addition to targeted research, Trust archaeologists also have to respond to chance finds – like the discovery of a 3,000-year-old rubbish pit eroding out of the sandy bank of a burn on the west side of the island. Within the dark soil were lots of limpet and whelk shells, burnt and unburnt animal bones, sherds of pottery, flint and large cobble stone tools. The animal bones are mostly sheep or goat, but one large chunk appears to be a scapula of a grey seal and must either have been hunted or collected after washing up on the beach. Two pieces of red deer antler were found in the vicinity several years ago by the farmer and these display obvious signs of cutting. The results of radiocarbon dating a sample of birch charcoal confirmed that the pit dated to between 930–810 BC, in the Late Bronze Age.

Archaeologists excavating an eroding bank on Iona.
Excavating the Bronze Age midden pit on the west side of the island

Over the years, volunteers have helped to conserve and repair some of the archaeological sites on Iona, in particular helping to conserve the machinery of the marble quarry at the southern end of the island. Preservation of the iron machinery in such an exposed location close to the sea has always been difficult, but over the years maintenance has at least reduced the rate of decay. The quarry is a Scheduled Ancient Monument and detailed advice and consent had to be obtained from Historic Environment Scotland for the work on this important industrial archaeological site. Work included the cleaning of the gas generator tank, the removal of corrosion, and the application of multiple coats of zinc phosphate primer before the final painting of a black gloss paint. Although Iona marble was probably quarried in medieval times, and the Duke of Argyll also authorised work in the late 18th century, the remains on the site today date to the work undertaken by the Iona Marble Company which was in operation from 1907–13. A new interpretation panel for this site has recently been prepared by Trust ranger Emily Wilkins.

Archaeologists conserving machinery in a marble quarry on Iona.
Conserving the marble quarry machinery

The Trust’s aims are to protect, promote and provide experiences of Scotland’s cultural and natural heritage. Our archaeological work on Iona over the years has started to unravel the history of human activity on the island beyond the confines of the early monastery. While these investigations have allowed people to visit the island and participate in archaeological fieldwork, we have also involved local primary school pupils (from Iona and Bunessan). It’s through working in partnership with the local community and research institutions that we will gain a better understanding of the history and archaeology of this very special island.

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