1999:743 - KILLAGHINTOBER BOG, Castlearmstrong, Offaly

NMI Burial Excavation Records

County: Offaly Site name: KILLAGHINTOBER BOG, Castlearmstrong

Sites and Monuments Record No.: N/A Licence number: 99E0445

Author: Ellen O'Carroll, ADS Ltd.

Site type: Road - class 1 togher

Period/Dating: Early Medieval (AD 400-AD 1099)

ITM: E 619211m, N 720627m

Latitude, Longitude (decimal degrees): 53.235687, -7.712223

This linear plank trackway was traced across the Bord na Móna field surface for a length of 450m. Four large cuttings were placed along its length. Each cutting produced similar constructional evidence and preservation qualities.

The trackway was a substantial construction consisting of three layers of structural elements. The upper, walking surface was constructed of split oak planks laid end to end and pegged into the peat at each end through a mortice hole. These pegs were found beside the substructural transverse timbers and would have prevented the upper plank from slipping off the substructure. Owing to the weight of the overlying peat and the Bord na Móna milling machinery, the plank had sunk into the peat and was found at the same level as the substructural timbers. The planks were also broken in several places along their length and had fallen off the underlying transverses.

The upper plank walkway was supported at regular intervals by a two-layered substructure. This substructure was composed of roundwood transverse timbers underlain by longitudinal plank runners. These planks were radial split oaks c. 2m long.

A dressed rod was found on the north-western side of the trackway. It was driven vertically into the peat. It was 20mm in diameter and 1.2m long. The top end of the rod was slightly bent, while the bottom end was stepped and then pointed. There were areas of poorly decomposed sphagnum peat with inclusions of Menyanthes trifoliata (bog bean), which suggests that these were very wet areas, probably pools, at certain locations beside the track. There were also areas of Eriophorum (bog cotton) above and around the trackway, which suggest drier conditions.

The construction methods of this trackway can be clearly demonstrated from the excavations along its the length. The substructural transverses; which consisted of a layer of roundwood and plank transverses underlain by longitudinal plank runners, supported the plank walkway and elevated it off the wet peat.

This trackway has been dendrochronologically dated by The Queen's University of Belfast to AD 596–7. The track can be traced from the dryland at Killaghintober to an island in the centre of the bog and appears to link up with a trackway of similar date and construction excavated by the IAWU in 1998 on the opposite side of the island (Excavations 1998, 176, 98E0464). The site then runs towards Lemanaghan Island, which houses the remains of St Mella's cell (a small Early Christian rectangular oratory), St Manchan's church and Early Christian grave slabs. Although this work is only at a preliminary stage, it is probably true to say that this trackway was associated with the construction of the monastery on the island, as it was founded sometime before St Manchan's death in AD 665.

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