The structures at The Cairns

The 2018 digging season is upon us and The Cairns excavation is now being prepared for the new season – an exciting time as the covers are removed and the groundwork begins. Especially as this year the spoil heap has been moved and a new trench is to be opened. 

It is a measure of the interest generated in this site that the University of the Highlands and Islands Archaeology Institute team now have a veritable army of volunteers from all over the world ready to start work.

However before the daily dig diary begins, perhaps it might be an idea to talk you through some of the structures that have been discovered at the site, to help you locate the finds that Martin and his team discover over the next few weeks of excavation. 

Here is everything you have ever wanted to know about The Cairns, but were too afraid to ask. Well, almost…

Structure A: the broch

Structure A is a broch, sometimes known as an Atlantic Roundhouse, a massive sub-circular structure around 22m in overall diameter. The walls of the broch are 5m thick, and the structure has an internal diameter of over 11m. It is well-preserved with the remains reaching over 2m in height at some points.

The thick outer walls contain at least 4 intramural chambers and the remains of a staircase indicating that this was a truly monumental multi-storey building.

So far, from the investigations of the interior, the well-preserved internal fixtures and fittings of the layout of space have been uncovered as well as a series of floor deposits of laid clay and flagstones. These floors are rich in artefacts, and environmental evidence for the use of the broch.

The Cairns project is a very rare opportunity to explore the entire suite of floors (from the very earliest to the last) from inside a broch, as this has very seldom happened in the modern era. At The Cairns we seem to have very good preservation of these important deposits and this is a real boon to the project. The work here should contribute a great deal to the study of the Iron Age in Scotland.

The ditch

Evidence that a great ditch surrounded the broch and formed a substantial enclosure some 70 metres in diameter has been acquired in both geophysical surveys and in trial excavation.

Last season, when the main trench was extended on the southern corner, we were treated to a view of the inner edge of this feature and we were able to excavate a few deposits from the fills. The ditch fills were very rich in animal bone, and in artefacts, including several bronze objects and a substantial quantity of pottery.

This year we will extend the edge of the trench further and hope to gain even more information on this important Iron Age boundary. What deposits and materials will we encounter?

Structure B Area: A Late Iron Age/Pictish Settlement

In the north and north-west part of the main trench, lies a substantial belt of building remains and features that we have called the Structure B Complex.

This partly overlies the top of the remains of the broch (Structure A), as well as spreading beyond it.

There are two main rectilinear and buildings present, with many well-preserved hearths, stone fixtures and fittings, small cells or chambers, thresholds, wall piers and floors. Often these various elements can be seen to relate to each other in a complex manner, with successive features cutting and partly demolishing earlier elements.

It brings to the fore the rich story of social change that almost certainly lies behind the fairly frenetic changes that have taken place across the Structure B area.

The area has yielded numerous small finds including substantial amounts of pottery, stone tools, an extensive animal bone assemblage, gaming counters, as well as a number of striking metal items, including numerous knife blades.

Perhaps most bizarrely, a carved stone object in the form of a human head came from the infill of Structure B2.

We now know that this post-broch settlement began at some point between the mid-3rd and 4th Centuries AD. How long it lasted into the Late Iron Age/Pictish period is not clear as yet.

One of the most remarkable aspects of the Structure B1 building was its very large, formal and complex central hearth, which was over 3 metres in length in its fully developed form.

This hearth and the central location of the building directly juxtaposed with the infilled interior of the abandoned broch make us suspect that the occupants of the B complex were keen to bask in the afterglow of the monumental broch, placing themselves directly over the core of its remains as if to co-opt its former position and grandeur.

This has always made us wonder if it was one of the key buildings in the immediate post-broch period at The Cairns, quite possibly the highest status building on site at that time. It may be the successor to the central broch in socio-political terms.

It is intriguing therefore that Structure B1 was contemporary with whoever was managing the wealth required to sponsor an episode of lavish jewellery-making on site (see Structure K).

Structure C “The Workshop/Smithy” and another possible workshop:Structure E

Structures C and E lie toward the east and south-east of the main trench respectively. They are similar in construction and both directly overlie, and intervene in, the remains of the walls of the Structure A broch.

They represent fairly substantial buildings built with a combination of stone uprights and coursed masonry, a style that has been seen as typically later Iron Age or even Pictish in the past.

Structure C appears to have been sub-oval or circular in plan in its original form, while Structure E was more straight-sided with a rounded gable end.

Both structures have yielded evidence for formal hearths in their interiors and, in the case of Structure C, a set of stone-settings and laid clay features indicate the remains of a grain dryer. In addition, there seem to be high temperature hearth stones present and a large quantity of heat affected materials. This, and the presence of moulds, bog ore, and fragments of tuyeres (nozzles or sockets used as the interface between furnace features and the bellows), indicate that the building had an industrial or craft-working role, at least during one stage in its life.

Archaeomagnetic dates obtained from these heat-affected features, which themselves seem to represent later activities in the building, indicate that it was abandoned some time before c.AD600.

The story of the very final acts inside this building is a very intriguing one. It seems there was a substantial episode of burning within the building. Currently this is interpreted as a deliberate act of decommissioning, which may have involved setting light to the building roof.

Several iron items (surviving to us as rusted, corroded objects) were apparently left on the floor of the building as it was nearing the end. Recent assessment of these indicates that they are several knife blades, one of which appears clad in mineralised organics which is probably a sheath.

Also, in the closing stages of the building a remarkable cache of twelve long-handled decorated combs, six of them carefully decorated with incised lines, were deposited in a pot and placed close to the entrance of the building. These combs were themselves caught up in the burning episode, as their fire-cracked, warped and fragmented state reveals.

Structure K: Even more metalworking evidence

Located in the northern part of the site, in the area we call Trench M, Structure K is an important part of the story of the site. There are the impressive remains of an episode of metalworking that include furnaces; bronze waste, bronze splashes and droplets, crucibles, and very significantly: moulds for casting fine bronze jewellery items.

Over sixty moulds and mould fragments have been recovered. These were used to cast a variety of objects, ranging from simple bronze rings, to distinctive decorated dress pins, called “projecting ring-headed pins”, and penannular brooches, which are the lovely open-ring, cloak brooches that are sometimes referred to as “Celtic” brooches.

The volume and nature of the items being produced suggests that this was a socially significant collection of prestigious items aimed at denoting the identity, and status of those who were to wear the items; badges of their belonging and importance within the community.

Importantly, it is the entire suite of materials found together, their condition and their precise distribution pattern within the trench, that indicates strongly that this material relates to an in situ metalworking event, rather than a secondary event, such as merely the refuse disposal of old moulds, or even their ritual deposition. This is important because the closer we can get to the actual context of the metalworking events the clearer and more direct our picture of the process becomes.

The moulds for casting the bronze jewellery were found in an area several metres in diameter, scattered within and across the remains of an Iron Age building (Structure K) that was already ruinous and unroofed by the time the metalworking was happening. That building was itself found to overlay the partially in-filled remains of a large enclosure ditch that had originally surrounded the broch period settlement.

Radiocarbon dates show that the jewellery-making occurred sometime between the AD240s and the mid AD300s. This places the metalworking very definitively after the end of the broch.

In radiocarbon terms, this makes the jewellery-making directly contemporary with the large post-broch house complex B on the southwestern part of the site. Perhaps it was the important and powerful household resident in Structure B1 who instigated and organised the production of the jewellery, and the feasting, with all the capacity that those remarkable objects and events had for the creation and maintenance of the later Iron Age community at The Cairns.

The understanding of the chronological and structural context of the metalworking allows us to consider the social context of this episode of metalworking. It is happening at a period of quite dramatic change in the material circumstances of Northern Iron Age communities in Scotland, at the end of the conventional Middle Iron Age and the beginning of the Later Iron Age periods, and contemporary with the mid to later Roman period further South.

It is very interesting that this episode therefore occurred after the culmination of the monumental phase of the site; after the demise of the massive broch at the heart of the community.

One prominent British Iron Age scholar, Professor Niall Sharples, from Cardiff University, has previously suggested that across Atlantic Scotland a pattern can be observed in which, around the time of the end of the brochs, when monumental domestic architecture is on the wane, there is a very substantial rise in the volume of items that reflect the presentation of the individual through personal adornment. This phenomenon seems to be reflected at The Cairns also.

Structure F: The souterrain or “earthhouse”

Structure F represents the very well-preserved remains of an underground building or passageway. This souterrain or “earthhouse” was constructed after the broch was disused and filled in with rubble, but it appears to make use of the five-metre-long entrance passage of the old broch for its chamber.

The discovery of the Structure F souterrain at The Cairns is very good news for us as it allows us to examine another example of a souterrain that is (mostly) undisturbed. One of the aims of the project is to explore and investigate these underground buildings in more detail and to try to offer a firmer basis for their interpretation.

At Structure F a remarkable feature had been set up on the roof lintels of the building which was composed of two deliberately broken rotary querns (grinding stones), one on top of the other poised over a gap in the lintels. Was the aperture this provided through the roof of the souterrain intended to allow communication to be uttered between above and below, or were substances or libations poured in? This year the complete excavation of the occupation deposits inside the structure may provide answers.

While we were assessing the interior of the souterrain for future full excavation a shaped whale tooth was found, which may originally have been a pommel for an item like a sword. The souterrain will be one of the principal areas for excavation attention this season, and we wait with anticipation to see what further exciting discoveries are made!