2000:0822 - DERRYNAGUN BOG, Lemanaghan, Offaly

Excavations were carried out in Derrynagun Bog, Co. Offaly, as part of the Bord na Móna Archaeological Mitigation Project. These excavations were undertaken to resolve known archaeological sites so that Bord na Móna could resume peat production in areas that had been cleared of archaeology. Derrynagun Bog is to the north-east of Lemanaghan dryland island, where the site of the monastic establishment of St Manchan of Liath is reputed to have been founded in the middle of the 7th century. This 17m x 2m cutting revealed the remains of five brushwood sites located close to each other, within an area of small brushwood and roundwood platforms that were excavated alongside a Bord na Móna drain (see Excavations 2000, Nos 819–21, 823–6.)

Site E lay at the north-western end of the cutting. It was excavated in its entirety and was 1.5m long, 1.5m wide and 0.2m deep. It was composed of a dense arrangement of brushwood (65%), averaging 0.02m in diameter. The spaces between the brushwood were infilled with twigs (35%). Most of the brushwood rods were orientated longitudinally and were quite short, averaging 0.4m. The wood was hard and quite gnarly, and there was some bark present. There were some larger brushwood rods excavated from around the edge of the site. There were no pegs excavated within this structure. There were some worked ends recorded from this site. Most of the worked ends recorded were chisel-pointed and single-faceted. The facets appear to have been cut with a metal axe.

Site D was located c. 6m to the south-east of Site E and was similar in structure and type. The site was composed of a linear arrangement of brushwood (80%) and twigs (20%), 1.5m long, 1.3m wide and 0.2m deep, which had been truncated on its northern end by the Bord na Móna drain. The brushwood averaged 15mm in diameter and 0.4m in length, and there was bark present on nearly all of the wood. The brushwood and twigs were three layers deep in places and had been compacted together to form a substantial though small wooden platform. There were some flat metal toolmarks on some of the brushwood.

Site C was located 1.8m from Site D, in pasty, brown, well-humified sphagnum peat. It comprised a narrow spread of longitudinally placed brushwood, one to two layers deep. Outlier wood was spread along the drain face to the north-west of the site. This outlier wood was probably dislodged from the main site during Bord na Móna ditching. The site was 0.6m wide, 1.2m long and 0.2m deep. The brushwood averaged 25mm in diameter, and all the brushwood had bark present. There were some pegs and a small amount of twigs scattered around the structure. A few of the brushwoods had worked ends.

Site B lay 3.5m from the main concentration of wood at Site C and was composed of heavy brushwood distributed over an area measuring 2m x 1m. The brushwoods were between 0.01m and 0.05m in diameter, averaging 0.03m. The length of the brushwoods ranged from 0.1m to 1m. Some of the brushwoods were forked and branched, and the majority had bark still intact. Outlier wood was spread along the drain face to the north-west of the site. There was no specific orientation or structured arrangement to the wood.

Site A was the north-easternmost of the five sites excavated. It was located beside the drain edge and had been cut by the drain; as a result its length on its northern side could not be determined. The site was 1.6m by 1.95m in total area and 0.05m deep, although some pegs were measured to a depth of 0.6m. It was composed of approximately twenty widely spread brushwood rods, between 15mm and 20mm in diameter. The brushwoods ran longitudinally along the line of the site and were flanked on either side by a line of pegs. The pegs, which were up to 0.6m long, were all identified as hazel and were worked to a chisel-point.

Three of these structures may represent small, distinct wooden platforms (Sites B, D and E), which were probably short-lived structures. The two remaining structures, the function of which remains enigmatic, were quite small and constructed of loosely laid brushwood. The platform structures may have been used for hunting or may have been associated with the collection of organic-type material from the surrounding peat.

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