This page describes the excavations on Iona undertaken by archaeologists at the University of Glasgow in collaboration with Historic Environment Scotland and the National Trust for Scotland in May 2017. The overall aim of this campaign was to re-excavate and partially extend two trenches first opened under the direction of Charles Thomas in 1956 and 1957, in order to clarify their findings and obtain new dating evidence.

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While combing through the archives from Charles Thomas’ unpublished excavations on Iona, we realised that there were a few unanswered (and rather unanswerable) questions which were raised by the available material. One was the presence of a massive drystone wall which appeared in Cutting 11d, just south of the medieval nave of the abbey church. Thomas’ notes do not make much mention of this feature, and only a single drawing and photograph survive in the archive. This was designated Site B (trench 2)

Iona 1958 006
The mysterious wall as glimpsed by Charles Thomas’ team in 1957

Another serious issue was the section of vallum excavated in 1956, in the crags west of the abbey. This section of vallum bank and ditch are still upstanding today. In 1956, torrential rain meant the ditch flooded and they were not able to bottom it out. Further, a nearby section of the vallum excavated in 1988 obtained radiocarbon dates suggesting the ramparts were possibly pre-Christian (McCormick 1993). It was imperative that this trench be fully excavated and dated to test that hypothesis. This was our Site A (trench 1).

A third area in the field south of the monastery was briefly investigated due to the presence of a broken field drain which needed repair. This was our Site C (trenches 3a and 3b).

Preliminary results

Download the data structure report here (PDF).

Re-excavated section through the western vallum (Site A).

The vallum ditch (Site A), previously only partially excavated, revealed waterlogged organic-rich deposits at its base and evidence of two possible periods of infill. We also found a bit of our own archaeological heritage – a cache of empty wine bottles left at the bottom of the trench before it was backfilled in 1956! We have even been able to identify some of the bottles – see our data structure report for more detail.

Cache of empty wine bottles from 1956 found at the bottom of Trench 1 (Site A).

At Site B, immediately south of the Benedictine abbey church, extending Thomas’ trench revealed the character of the massive drystone wall to be a revetment for a possible clay-bonded building with a curved end-wall which dated to the pre-Benedictine phase of the site, possibly an apsed church (see header image). Disarticulated human bone was found within and outwith the walled structure.

At Site C initial attempts to locate and repair a broken field drain were abandoned due to flooding, but indications of occupation in the post-medieval period were recovered, along with possible prehistoric ard-marks, in an area with no previous archaeological investigations.

We have now obtained a first round of radiocarbon dates from this excavation campaign, of which these are the main highlights:

  • The lowest fill of the western vallum ditch dates to AD 580-660 – making it one of the earliest features of the site
  • The massive stone wall in Site B is also very early in the sequence – built before a C14 date of AD 665-770
  • Occupation layers above the wall in Site B shows that it was abandoned and robbed out before the Benedictine period, AD 10-12th centuries
  • Human burials outside and within the wall are also pre-Benedictine, 11/12th centuries

Implications and new questions

We are only beginning to explore the implications of these results. Firstly, we have been able to show that the western vallum bank and ditch is not an Iron Age, pre-Christian construction, but one of the earliest features of Columba’s monastery, dated to within his lifetime or within a few generations. It means that the site was monumentalised very soon after its foundation, certainly before Adomnán’s famous Life of St Columba (AD 697) made Iona famous on an international scale.

The early date for the drystone wall of Site B comes from a slag-rich occupation layer which is stratigraphically later than the wall, meaning that this too was a surprisingly early feature of the site. Scheduled monument consent conditions meant that we could only partially excavate this structure, and so while the shape as revealed looks tantalisingly like an apse-ended stone church, we cannot prove it unequivocally without revealing more of the structure.

Future work

While we now have strong evidence that the monastic vallum was an early feature of Iona’s layout, we know from geophysical survey that the enclosure is complex, with many overlapping ditch systems cut and re-cut over the centuries. We are experimenting with ways of sampling various parts of the ditch to see whether we can establish a chronology of enclosure on Iona.

But the main target for any future work must now be to sort out the extent and function of the clay-bonded structure with massive stone foundations at Site B. However, this is also one of the most sensitive areas of the property in care, with potential for articulated burials and other early material. With close collaboration with our partners in HES and NTS, we will have to weigh up the risks and opportunities of doing more excavation in the heart of the early monastery.

Works cited

McCormick, F 1993, Excavations at Iona, 1988, Ulster Journal of Archaeology 56: pp. 78-108, available at http://www.jstor.org/stable/20568189

Suggested citation for this page:

Iona Research Group 2017, Excavations on Iona 2017. Retrieved from http://ionaresearchgroup.arts.gla.ac.uk/index.php/projects/excavations-2017/‎, accessed ___.