By Fran Houston
Very few crannogs exist outside Scotland and Ireland and there is still much to be discovered about these lake dwellings. An initial survey of the crannogs of Loch Tay was carried out by the Scottish Trust for Underwater Archaeology in 1979. Its aims included examining each site in order to establish its form and structural elements.
Loch Tay boasts 18 crannogs. One of these, Oakbank, is near the village of Fearnan (National Grid Reference: NN 72284425; PKHER: MPK484) and it was selected for further study. It is an important site for several reasons. Firstly it was fully-submerged and excavated using modern archaeological techniques. Secondly, it amounted to over 1000 cubic metres in volume of almost entirely organic material, with an excellent level of preservation of plant remains, structural timbers, and artefacts, due to the cold loch water and anaerobic conditions. Thirdly, the finds are fully accessible at the Scottish Crannog Centre and afford the potential for in-depth and rewarding research.
Initial examinations in 1980 and 1982 revealed a mound, ranging between c.1.5m high to c.3m high, on a sandy loch bed which sloped gently away from shore. A top layer of large boulders was removed and two areas of the site were excavated. Subsequent excavations were carried out at annual field seasons until 1992, followed by more in 2002, 2003 and 2005.
The large mound was joined to a smaller mound of stones by a narrow neck of boulders. The smaller mound was initially described as an egg-shaped extension and suggestions for its use included a landing stage or jetty. A slight ridge of stony gravel was also discovered which had 40 oak pile stumps projecting out of it. These were the remains of a gangway which connected the crannog to the shore.
Oakbank Crannog was discovered to be a freestanding timber framework of foundation piles driven into the loch bed, supporting a platform which held a 15m diameter roundhouse and walkway surround, with a gangway to the shore. A separate row of foundation piles ran at right angles to the gangway and this feature is thought to be a shielding fence.
The site comprised several context layers including the loch bed itself into which foundation piles were driven. A 1.5m thick deposit of organic material included upright stakes and foundation piles, longitudinal timbers, compacted bracken, ferns, twigs, leaves, insect remains, dung, seeds and nuts. This layer was very well preserved as it was in a fully submerged and anaerobic environment. Other factors, including high levels of oak and bracken tannin, also helped inhibit decay. Waterborne deposits in the form of grit and silt sat on top of this deep organic layer, to a depth of 1-3cm. On top of these deposits was a layer of small stones, thought to be a base for a cap of larger boulders covering the entire mound.
It is not entirely clear why a layer of boulders covered the crannog but, interestingly, all the crannogs in Loch Tay and Loch Awe have this feature. There was also a band or ring of stones, c.3m wide, around the edge of Oakbank Crannog, which appears to have protected it from water movement and erosion, thus preserving the upright foundation piles. This ring was put in at a later building phase.
Construction had begun during the Early Iron Age. The earliest structural activity relates to two timbers. One, from the surrounding walkway, was dated to 775-510 cal BC (95.4% probability). Another, from the ‘extension’ feature, was subject to three-point wiggle-match dating, which indicated felling of the tree occurred 550-490 cal BC (67.4% probability). One fascinating body of research has examined the tool marks left on timbers. This has shown that the latter of these two timbers was produced by an axe – probably iron and socketed – which had a gently curving blade 66.5mm wide.
A later phase of building activity seems to have occurred in the 5th century BC. One timber from this phase is dated 525-435 cal BC (95.4% probability); another appears to have been felled 540-405 cal BC (95.4% probability); and another was dated to 550-400 cal BC (78.1% probability). A fourth timber was subject to three-point wiggle-match dating which indicated felling 500-400 cal BC (79.4% probability).
A final stage of recognised building activity is associated with two areas of the crannog. Timbers in these areas were felled 405-390 cal BC (95.4% probability).
Excavations of the construction features and research on, amongst other subjects, plant remains, all suggest that Oakbank Crannog was a dwelling house and that the occupants were farmers. The interior was divided into separate areas including a stall for livestock, a crop processing area, and a general-purpose living space. The floor timbers were covered with bracken and rushes and substantial deposits of charcoal, burnt bone and ash are evidence of a hearth.
Barley was the principal crop grown on the crannog dwellers’ farm but emmer wheat and spelt wheat were also found during plant macrofossil analysis. The people may have spread their labour by planting emmer and spelt in autumn and barley in spring. This would guarantee a yield from at least one crop. Other plant remains suggest that flax and opium poppy were also cultivated on a minor scale.
Cloudberry seeds were a significant find. Cloudberry is very rare in fossil records and the finds at Oakbank Crannog are some of the earliest in British pre-history. They had been gathered from a montane location some distance away. Although good arable land would have been relevant to the choice of a crannog site, it may not have been the only criterion. Habitats several hours’ walk away from Oakbank had clearly been exploited.
The excavated artefacts and organic remains are displayed at the Scottish Crannog Centre. Some of these are of international significance, adding to the unique nature of the site. The collections include a dairying dish plus the residue of a dairy product; a copper alloy swan neck pin, believed to be one of Scotland’s finest examples; a small iron dagger; and a dogrose shepherding or hunting whistle.
Objects including a fruitwood stave from a small coopered vessel and an alder plate suggest fine craftsmanship and included in this group is one object of particular significance. Small, 67mm long but clearly broken along its length, it was hand-crafted and precisely notched. Believed to be the bridge of a lyre, its importance cannot be underestimated. Remains of stringed musical instruments are rare from this time period. Furthermore, although they are evidence in themselves of music-making, they also give us clues about the type of songs that were accompanied by plucked strings. Ultimately, this tiny artefact is indicative of cultural life on Oakbank Crannog.
Another significant discovery is a woollen textile fragment which is highly important due to its secure excavation context and its unusual weave pattern of a 2/1 twill. The two yarn systems – the weft and the warp – have distinct tones and examination has revealed that the fibres are a semi-fine wool, consistent with that expected of a fine Iron Age sheep fleece, possibly from an animal within the Oakbank Crannog dwellers’ own herd of livestock. The textile has been radiocarbon dated to 480-390 cal BC (95.4% probability).
The excavations of Oakbank Crannog have captured a moment in time. The finds have revealed a wealth of information about the lives of the crannog dwellers and research so far implies that this unique site and its collections are important at an international level. The collections are fully accessible for research at the Scottish Crannog Centre www.crannog.co.uk
- The Recording and Archaeological Potential of Tool Marks on Prehistoric Worked Wood with Special Reference to Oakbank Crannog, Loch Tay, Scotland. Robert J. S. Sands, PhD, University of Edinburgh, 1994.
- Scottish Crannogs. Underwater excavation of artificial islands with special reference to Oakbank Crannog, Loch Tay. Thomas Nicholas Dixon, MA (Edinburgh) PhD. University of Edinburgh, 1984.
- Summary of the chronological results of the Living on Water project up to December 2019.
- An Archaeobotanical Investigation of Oakbank Crannog, a Prehistoric Lake Dwelling in Loch Tay, the Scottish Highlands. Jennifer Jane Miller, Thesis submitted to the University of Glasgow for the degree of PhD. Division of Environmental and Evolutionary Biology, August 1997.