Na Clachan Aoraidh

Geophysical surveys were conducted at Na Clachan Aoraidh stone circle near Blair Atholl, Perth and Kinross. The works comprised high resolution geomagnetic and earth electrical surveys of the stone circle and its immediate vicinity. The works were commissioned by AOC Archaeology Group and conducted by Archaeological Services Durham University.

Information from Oasis (archaeol3-115344) 10 September 2012

Geophysical surveys were conducted at Na Clachan Aoraidh stone circle near Blair Atholl, Perth and Kinross. The works comprised high resolution geomagnetic and earth electrical surveys of the stone circle and its immediate vicinity. The works were commissioned by AOC Archaeology Group and conducted by Archaeological Services Durham University.

Information from Oasis (archaeol3-115344) 10 September 2012

A laser scan survey and geophysical investigation was undertaken at Na Clachan Aoraidh stone circle near Blair Atholl, Perth and Kinross. A detailed 3D view of the site was produced, integrated with the results of the geophysical survey, as well as 2D topographic plans and profiles and a condition statement.

Information from Oasis (aocarcha1-118614) 10 April 2012

NN 83861 62018 (NN86SW 3) The site is referred to as Na Carraigean Edintian or Na Clachan Aoraidh ‘the stones of worship’ (Burl 1988, 187). The standing stones comprise four boulders of quartziferous schist forming a quadrilateral c3.2 x 3.6m; the stones are graded with the tallest occurring in the SW corner and these are set on the circumference of a

circle which is c4.3m in diameter, although all but one of the stones are now leaning. The stones are set on a low mound or platform formed from cairn material and which is c16.5 x 8.85m in diameter. The platform appears to be kerbed by smaller stones. There is a slight hollow in the centre of the mound, thought to be the result of undocumented activities of earlier antiquarians. In recent years a bonfire within the hollow may have caused further damage to the monument.

The site was subject to topographical and a geophysical survey, including magnetometry and resistivity (Archaeological Services Durham University) and laser scanning (AOC Archaeology), the results of which were used to produce a 3D visualization of all elements of the site. A stone kerb or revetment was detected encircling the standing stones and outside of which was an arc of low resistance consistent with a ditch; this feature appears to resemble the ditch which encircled the natural mound of the four-poster at Lundin Farm South-East (Stewart 1967). Within the platform

two negative magnetic anomalies were interpreted as voids, possible caused by cists or stoneholes. Within the slightly sunken centre was a positive magnetic anomaly which could be detecting the backfill of an antiquarian excavation. On the S side of the platform another curvilinear positive magnetic anomaly was thought to be the fill of another ditch and

which may well be the remains of a ring ditch. Also on the S side of the platform a possible stone wall/dyke was detected and an equally stony rectangular feature was recorded on the E side of the four-poster platform.

A sample excavation was undertaken, 24 October – 11 November 2016, in order to:

• Evaluate the damage upon the archaeological deposits caused by an illegal fire pit

• Ascertain the extent and nature of surviving archaeological deposits

• Ensure the continued protection of surviving features

• Enhance the historic environmental record

The excavation of three trenches over and adjacent to the monument revealed:

• The four standing stones occurred within and at least one was contemporary with the stone platform which was roughly 0.50m thick.

• The platform was edged by a kerb of larger cobbles.

• There was no ditch outside the kerb.

• One of the internal magnetic anomalies was shown to be a void within the stone platform, no archaeological material was observed within this; it is unclear whether this is an empty cist or a fortuitous void.

• The central hollow was not caused by antiquarian digging but it was the location of a probable tree throw that had been modified and into which a central pit containing cremated bone (human?) and ashes had been dug.

• There was no ring ditch on the S side of the monument.

• There was no stone wall or dyke on the S side of the monument.

• There was no stony rectangular feature on the E side of the monument.

• There was no entrance into the monument.

• The heat effects of the central bonfire had not penetrated below the turf and had not caused any damage to the archaeological horizons.

In conclusion, the four poster stone circle is a simply constructed monument comprising an oval stone platform cairn and four stone orthostats arranged around a central pit which contains burnt bone mixed with ash and redeposited soil. The monument appears to have been centred on a hollow which was created by a collapsed or dead tree. The

site was backfilled and a layer of gravel placed upon terram but under the turf in the centre of the monument to protect the underlying deposits from damage in the event of further illegal bonfires.

Archive: HES and NRHE (intended)

Funder: Forestry Commission Scotland

Clare Ellis – Argyll Archaeology

(Source: DES, Volume 17)

NN 83861 62018 (NN86SW 3) Resistivity survey.

Archive: HES and NRHE (intended)

Funder: Forestry Commission Scotland

Clare Ellis – Argyll Archaeology

(Source: DES, Volume 17)

NN 83861 62018 (NN86SW 3) Magnetometry survey.

Archive: HES and NRHE (intended)

Funder: Forestry Commission Scotland

Clare Ellis – Argyll Archaeology

(Source: DES, Volume 17)

Archaeological importance

The stone circle of Na Clachan Aoraidh – the ‘Stones of Worship’ – is set high on the limestone ridge of Cnoc na Craoibhe above Loch Tummel. The site is an unusual ‘four poster’ stone circle – a square arrangement of four large stones on a low stone-built circular platform. It is an early Bronze Age site and was probably built about 4000 years ago.

Writing of Na Clachan Aoraidh in 1908, the archaeologist Fred Coles noted that the “site, scenery, megalithic remains and surroundings all combine to render the investigation of this group especially interesting”. It is a place with real character, with spectacular views over the surrounding landscape and towards Schielhallion and Ben Vrackie. Although likely ceremonial, the few excavated examples often also display activities associated with funeral pyres and cremation burials. There is a particularly dense concentration of such sites in northern Perthshire, with examples scattered through the Tay, Earn and Tummel valleys.

In 2012, an archaeological measured survey was undertaken of Na Clachan Aoraidh by terrestrial laser scanning, providing an accurate baseline record of the site. This quickly proved to be very useful: in 2016, following an unauthorised bonfire, archaeologists were required to investigate the site further and record the damage. Particular care was taken to explore the soil itself, taking samples to compare heat-damaged deposits with undamaged areas and sieving the soil for microscopic flakes of charcoal and cremated bone. The centre of the site has now been protected under the turf with a sacrificial layer of gravel.

Na Clachan Aoraidh is a site of significant archaeological importance: it contains important buried archaeological deposits, it has great architectural character and it commands a distinct setting within the wider landscape. It is a worthy cover star of the new FCS Outdoor Archaeological Learning resource and a great example of the ‘power of place’, whereby a visit to an archaeological site can inspire discussion, learning, creativity and reflection.

Ecological importance

But it is also a site of significant ecological importance, as the open summit of the limestone ridge of Cnoc na Craoibhe comprises about 22 ha of upland calcareous grassland. This is a relatively rare and species-rich habitat and is one of the habitats identified within the category of ‘conservation action needed’ within the Scottish Biodiversity Strategy. Maintaining and achieving the good condition of significant existing open priority habitat is a key environmental objective on Scotland’s National Forest Estate.

Species-rich grasslands are early successional habitats. The main threat to this habitat is under-grazing, with low grazing levels or a lack of grazing resulting in the accumulation of vegetation litter and soil nutrients. Over time, this creates a rank species-poor sward made up of relatively common palatable tall herbs. Although these more fertile grasslands provide better grazing, they are more common and don’t support as many species of plants and insects. Grazing animals tend to eat the lusher plant species, allowing the finer plants and flowers to thrive; and, by doing so, prevent the nutrients from being recycled into the soil again. The more aggressive plants cannot invade and displace the rare plants which thrive in low nutrient conditions.

So grazing often has a vital role to play in improving, maintaining or enhancing significant open habitats and archaeological sites. The open summit of Cnoc na Craoibhe was fenced, the regenerating conifers were felled and removed and conservation grazing was introduced at this important upland calcareous grassland habitat. Including the conservation management (and condition monitoring) of the ‘four poster’ stone circle as part of the conservation grazing demonstrates Forestry Commission Scotland’s ecosystem approach to integrated land management.

Matthew Ritchie - Archaeologist, Forestry Commission Scotland