2000:0818 - DERRYNAGUN BOG, LEABEG, Offaly

This excavation was carried out in Derrynagun Bog, Co. Offaly, as part of the 2000 Bord na Móna Archaeological Mitigation Project. It was located at the north-eastern extent of Derrynagun Bog close to the adjoining reclaimed farmland. The site was sampled and dated, after the field survey in 1998, to 1547 BC (QUB-9255). The site was in the process of being destroyed. Very little substantial in situ remains survived, but from this material it was possible to trace the site for a length of over 224m.

A single 2m x 2m cutting was recommended in the mitigation strategy document laid down by Dúchas The Heritage Service and the National Museum. It was established that the only surviving in situ remains of the site were where the site was exposed in section in the drain face. A single plank was visible, in both sides of the drain, 0.31m below the field surface. The cutting was extended to 4m x 2m along the length of the site to facilitate the investigation of the presence or absence of substructural elements.

The peat directly overlying the site was very dark in colour, and, while it was physically very wet, it was crumbly in texture. This crumbly texture is indicative of redeposited or disturbed peats. Prior to commercial development this part of Derrynagun Bog contained turbary plots that were subsequently levelled out. This side of the bog has not been as extensively milled as has the south-western extent. The sighting chosen for excavation, as mentioned above, was the only in situ remains of the site. The other four sightings were fragmentary, dried out and disturbed planks, all of which were located on the field surface.

Although the cutting size was extended to 4m x 2m, only a single plank placed north-east/south-west was revealed. This plank was a squared, radial split, known as a secondary conversion radial split. It measured 0.16m in width and between 70mm and 100mm in depth. The area beyond the north-eastern cutting edge was probed to establish the extent of the plank, which would appear to have been at least 5.5m long. The plank visible in the opposing drain face was very similar in size and conversion and was most likely to have been the same timber. It was in moderate to poor condition, splitting and disintegrating when sampled. The peat onto which that plank had been placed was mainly sphagnum-rich, bright orange in colour when first trowelled and turning darker as it oxidised. There were patches of eriophorum, mainly along the northern cutting edge and directly along the sides of the plank itself. There was no evidence for substructural supports of any sort. It may be the case that there never were any supporting timbers. The excavation of a Bronze Age plank trackway in the neighbouring bog of Killaghintober by Ellen OCarroll in 1999 (Excavations 1999, 263, 99E0447) also revealed an apparent lack of substructure. In both cases the underlying ground conditions of sphagnum-rich peats would appear to indicate that the sites were constructed across particularly wet stretches of bogland. The lack of substructure may indicate that the planks were actually placed across the driest parts of these very wet areas. It is hoped that this may be resolved by specialist analysis of the environmental remains.