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Southwest Scotland crannog survey

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Jon Henderson, Underwater Archaeology Research Centre; Graeme Cavers, Underwater Archaeology Research Centre and Anne Crone, AOC Archaeology Group

 

 

Introduction

In 1989 AOC Archaeology, on behalf of Historic Scotland, carried out an assessment of the crannog resource in South West. The assumption of the survey was that the submerged crannogs in the area were relatively stable while their counterparts on drained land were rapidly decaying. While, as may have been expected, clear indications of the accelerated organic decay of sites on drained land were obtained, rather more surprisingly, it was suggested that submerged sites were also subject to decay. It was assumed that this was as a result of the infestation of underwater plant and animal life accelerating the biodegradation of organic deposits and was caused, primarily, by increased levels of nitrate run-off in affected lochs.

 

 

Surveying crannogs in their landscape setting.

 Surveying crannogs in their landscape setting 

In 2002, Phase 2 of the South West Scotland Crannog Survey was set up as part of the Scottish Wetland Archaeology Programme (SWAP) initiative funded by Historic Scotland.

The aims of this second phase of survey are:

  • to identify crannog sites that are being subject to active biological decay
  • accurately survey threatened sites
  • establish effective systems of monitoring the rate of organic degradation taking place on sites located in different environments (submerged and on land).

 

 
Diver survey of crannogs.

  Diver survey of crannogs

Ultimately through a long-term monitoring programme we hope to identify the mechanisms and causes of organic decay on crannogs throughout the South West so that effective preservation and management strategies can be implemented.

 

The Crannogs of South West Scotland

The crannogs of South West Scotland are usually envisaged as 'packwerk' mounds - made up of layers of peat, timber and brushwood to provide an artificial island for a timber superstructure - and are traditionally thought to contrast as a constructional type with the stone and boulder mounds found in the Highland regions north of the Clyde (Henderson 1998, 236). However, the systematic surveys carried out during the SWCS have revealed that there is a far greater diversity of constructional forms present in the South West than has previously been recognised (Henderson et al. 2003).

Rough Island in Loch Urr.

 Rough Island in Loch Urr 

While 'packwerk' mounds of peat, brushwood and timber undoubtedly exist (such as at Buiston, Barlockhart, Milton Loch 1 and the Black Loch of Sanqhuar) there are also sites which feature a substantial stone element in their construction (for example at Dorman's Island in Whitefield Loch, Heron Isle in Black Loch, Cults Loch 1 and the crannog in Barean Loch) or that appear to be completely constructed out of stone with a stone superstructure on top (Rough Island in Loch Urr).

The artificial island in Loch Arthur (see Loch Arthur project) consists of two mounds of different material, the upper mound (the island) being built primarily of large boulders within a well developed soil, and the lower submerged mound of timber, brushwood and some smaller stones (Henderson et al. 2003; 2006; Henderson 2007).

Potential free-standing pile forms also exist. Survey of the submerged crannog in Barhapple Loch revealed a sub-rectangular plan of 144 vertical piles and 31 horizontal timbers (mainly oak with some alder) sitting directly in soft loch silts in a water depth of c.0.5 metres. The lack of any mound structure or boulder element to the site coupled with the dense distribution of vertical timbers may indicate that Barhapple was initially a free-standing structure that was later subject to the apparently in-situ occupation levels recorded by Munro in 1882.

At the White Loch of Myrton the crannog appears as a stone and timber mound with a dense concentration of over 100 vertical piles in an area some 20 metres by 40 metres occurring around the north-eastern margins of the site (Henderson et al. 2003, fig. 7, 93-94). The piles varied greatly in diameter from 0.1 metres to 0.4 metres and appeared to be regularly spaced about 1 metre apart. Most of the piles have decayed down to loch bed level although some still sit proud of the loch bed by about 0.2 metres. Soft silts surrounding the site and zero visibility conditions underwater made further examination of this site difficult but two piles, both with axe sharpened points, were sampled and identified as ash.

Although only traceable around the north-eastern margins of the main mound because the western and southern sides are shallower and choked with thick reeds, the location and spacing of the traceable piles suggest they were originally inserted into the loch bed in a concentric halo around the stone mound. They may therefore reflect the remains of either a site pre-dating the stone mound or of a free-standing timber superstructure contemporary with activity on the main mound.

 
Plan of Barhapple Crannog.

 Plan of Barhapple Crannog 

The SWCS has also revealed the first Scottish example of a potential lake-side settlement. At Cults Loch 16 vertical piles and one horizontal timber were found encircling a promontory which although it did not appear artificial from surface inspection produced charcoal on coring. These remains could indicate the presence of a crannog, though no other typical structural features were present. The site is considered more likely to be a lake-side site perhaps related in some way to the crannog in Cults Loch.

 

Although a worked oak stake was sampled from the site and produced a radiocarbon date of 2340 ± 50 BP (GU-12138), calibrating at 2 sigma to 550 to 200 BC, which is somewhat earlier than the date of 1790 ± 50 BP (GU-10919), calibrating to AD 120 to 390, obtained from the crannog out in the loch. Lake-side sites were previously only known from Ireland and the discovery of the site suggests that the systematic survey of lake margins may be a fruitful avenue of future research in Scotland.

Sampling timbers at Cults Loch Promontory.

 Sampling timbers at Cults Loch Promontory 

The findings of the SWCS challenge simplistic definitions of crannog form and question the relevance of previously held type boundaries. Many of the sites in the South West which feature substantial stone elements are difficult to separate on constructional grounds from the boulder mound sites of the Scottish Highlands.

The perceived differences between the Highland and South West sites may be more attributable to the lack of underwater survey carried out nationally as many of the key identifiable characteristics of sites noted during the SWCS can only be seen underwater.

Previous surveys in the South West have been land based and have focused on the examination of drained sites. As a result the impression has been created in the literature that South Western sites are mounds of peat, timber and brushwood. In fact the occurrence of peat on sites may simply be due to the circumstances of preservation as brushwood and plant matter will survive intact in submerged contexts but such deposits are more likely to decay leading to the formation of peat on drained and periodically flooded sites.

The perceived differences between Highland and South Western sites may have more to do with the widespread drainage and improvement operations in the latter area than any significant cultural structural or chronological variation. Equally the more widespread occurrence of exposed organics and structural timber on submerged sites in the South West may be attributable to the smaller size and less active tidal regimes of those lochs compared to the much larger and more turbulent Highland lochs.

 
Timber subject to advanced organic decay at Loch Arthur (scale 20 cm).

Image: Timber subject to advanced organic decay at Loch Arthur (scale 20 cm) Clear tool facets on ash piles recovered from the White Loch of Myrton crannog (scale 10 cm)

Clear tool facets on ash piles recovered from the White Loch of Myrton crannog (scale 10 cm).

Image: The project is grant aided by Historic Scotland and is being conducted by UARC and AOC Archaeology as part of the Scottish Wetland Archaeology Programme (SWAP).

 

 

 

Publications

HENDERSON, J.C., 2007. Recognising complexity and realizing the potential of Scottish Crannogs. In: BARBER, J., CLARKE, C., CRONE, A., HALE, A., HENDERSON, J., HOUSLEY, R., SANDS, R., SHERIDAN, A., eds. Archaeology From The Wetlands: Recent Perspectives. Edinburgh: Society of Antiquaries of Scotland. pp. 231-241.

HENDERSON, J.C., 2004. The Scottish Wetland Archaeology Programme: Assessing and Monitoring the Resource. Journal of Wetland Archaeology, 4, 169-182.

HENDERSON, J. C. 1998. Islets through time: the definition, dating and distribution of Scottish crannogs. Oxford Journal of Archaeology, 17:2, 227-244.

HENDERSON, J.C., CAVERS, M. G., AND CRONE, B. A., 2006. The South West Crannog Survey: Recent work on the lake dwellings of Dumfries and Galloway. Transactions of the Dumfriesshire and Galloway Natural History and Antiquarian Society, 80, pp. 29-52.

HENDERSON, J.C., CRONE, B.A., AND CAVERS, M.G., 2003. A condition survey of selected crannogs in south west Scotland. Transactions of the Dumfriesshire and Galloway Natural History and Antiquarian Society, 77, 79-102.

 

 

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