1996:365 - DERRYVILLE BOG, Derryfadda/Killoran/Cooleeney, Tipperary

Introduction
The interdisciplinary archaeological project currently underway on the tailings management facility (TMF) site of the proposed Lisheen mine development commenced in July 1996, on behalf of Minorco Lisheen Ltd, in response to the anticipated requirements of the Planning Authority after consultation with the Heritage Services of the Department of Arts, Culture and the Gaeltacht. The project has completed one field season, with a second and final field season to follow in 1997.

The TMF site is located on a spit of industrially worked, Bord na Mona-owned raised bog which extends southwards from their extensive milled peat fields, forming part of the Templetuohy/Littleton bog complex. The preparation of an inventory of sites and monuments, together with the inspection of all areas in which proposed development is to take place, formed part of the baseline work for the EIS. This process involved a preliminary evaluation of the bog in 1993, followed by a detailed archaeological assessment of the proposed TMF site by the Irish Archaeological Wetland Unit (IAWU) in 1995 (Excavations 1995, 93). The results of the IAWU survey led to the academic design of the current project, which is being funded in full by Minorco Lisheen Ltd and managed by Margaret Gowen and Co. Ltd. The field team is led by Cara Murray and Paul Stevens, with the assistance of Tim Coughlan on operations and the technical set-up stages as well as excavation of the trackway 95DER18.

96E202 (Cara Murray)
During the first field season 29 sites were excavated, of which one was a fulacht fiadh, 24 were of a variety of types composed entirely of wood, and the remaining four were non-archaeological environmental sites. The sites were located in the south-eastern area of the bog, associated with two natural glacial moraines which extend westwards, below the peat, from the existing eastern dryland or upland. The majority of the sites were located within bog margins and associated with bog marginal forest.

Nine sites were excavated in the fen peat and bog marginal forest which developed over the 'middle glacial ridge'. They could be divided into two main clusters c. 90m apart, one incorporating six sites at the northern end of the ridge (95DER6, 95DER10, 96DER206, 96DER214, 96DER215, 96DER216) and the second incorporating three sites at the southern end (95DER9, 96DER203, 96DER212).

The northern cluster was composed of an irregularly shaped fulacht fiadh, 96DER216, which measured 19m east-west by 14m north-south, and the mound material was on average 0.6m deep. This was set on the fen peat to the west and on the glacial till to the east. It had two phases of use separated by a thin deposit of silt.

Phase I was represented by the construction of a timber-lined trough (2.4m by 1.75m and 06m deep) and, to its west, the deposition of a spread of burnt sandstone and limestone overlain by a spread of charcoal-rich loam.

Phase II saw the dumping of a layer of burnt sandstone and limestone in a charcoal-rich matrix across the east of the site. This layer backfilled the trough, which was recur. At the eastern end of the site a dense spread of charcoal was interpreted as a hearth. A number of stake-holes uncovered beside the site of the troughs should be identified with both phases.The fulacht fiadh was overlain by 0.2m of fen peat on which sat two sites, a platform (95DER6) and a small togher (96DER215). The former was 0.35m deep, measuring 7m by 8m; the latter was 0.3m deep, measuring 8m by 4m, and ran north off the north-western corner of 95DER6. At its southern end 95DER6 was overgrown by the alder carr forest root systems, into which was set a 0.15m-deep brushwood platform (96DER214), 5m by 3m, separated from 95DER6 and 96DER215 by between 50mm and 100mm of peat development. To the north of the main group, and at a level c. 0.5m lower down in the peat, the last site in the northern cluster, 96DER206, was a 5m by 2m by 0.25m-deep puddle togher running north-west/south-east through fen peat for c. 5m. Another site, 95DER10, containing only a few possible archaeological timbers was also associated with the alder carr root systems 10m to the west of 96DER214.

The two sites on the southern side of this ridge, a platform (95DER9) measuring 7m by 8m and 0.15m deep, and a togher (96DER203) measuring 16m by 6m and 0.2m deep, were located at the same level in the fen peat although they were 20m apart. Three artefacts were retrieved from these sites, two wooden pommel-headed shafts from 95DER9 and a wooden headed peg from 96DER203. A third site, 96DER212, had been destroyed and simply consisted of two pieces of worked brushwood lying on the field surface, located c. 5m south-east of 95DER9.

On the southern glacial ridge a complex cluster of seventeen sites occurred at three discrete levels (described in detail below). Most of the sites were located on the central and southern side of this glacial ridge and within rapidly developing fen peat of an alder carr forest (W. Casparie, pers. comm.). Owing to the rapid nature of the peat development in relation to the natural glacial ridge, the stratigraphic relationship of these sites will only be fully understood when the dating evidence returns. Three sites cannot yet be securely linked to these three levels; these include two puddle toghers (96DER204 and 96DER207) on the western side of the glacial ridge, c. 1m below the level of 95DER209, and a single-plank trackway (95DER23) approximately 40m to the west of this main cluster of sites. This last-mentioned site has yielded a Bronze Age date of 1590±9 BC (Q9370) and is, to date, the earliest known site within this bog. The track, which was located at a much lower level on highly humified sphagnum peat, ran east-west for a total length of 34m.

Within the main cluster of sites, Level 1 is associated with the interrelated sites of 95DER90, 91 and 218 (see below). Level 2 is associated with more extensive activity in the alder cart forest associated with the platform 96DER213, which measured 3.8m x 4m, and possibly the small puddle togher 96DER211, OD range 124.641–12429m. Level 3 sites were all located in an area roughly 50m east-west and 40m north-south, and were situated on the centre of the gravel ridge and in the developed alder carr to the south. Eight sites, which have an OD range of 125.426–124.726m, were excavated at this level (95DER13, 95DER92, 96DER201, 96DER205, 96DER208, 96DER209 and 96DER210) within an area approximately 50m north-south x 50m east-west.

Level 1
On the southern side of the ridge an extensive area of archaeological wood forms a platform-like structure, 96DER218, which is associated with 95DER90 and 91. The site was not fully excavated this season and will be completed in 1997.

The archaeological wood within it runs for a total length of 17.48m north-south along one of the Bord na Mona drain faces and varies in depth from 0.3m to 0.6m. Within the section face the site was seen as a series of irregularly set horizontal elements and some uprights which ranged from 20mm to 180mm in diameter. The greatest concentration of material was located at the southern end of the exposed section, where a 0.4m-deep deposit of interwoven brushwood occurred. Two pieces of prehistoric pottery were removed from this part of the section face of the Bord na Mona drain.

Level 2
This is associated with the puddle togher 96DER2 13 and a large area of worked wood in situ. Located on top of the ridge, 0.15m below 96DER210 (see Level 3 below), is a small togher, 96DER21 1, which measures 5m north-south, 2.5m east-west and varied in depth from 0.3m to 0.4m. Levels 2 and 3 on the southern side of the ridge are separated by only c. 0.2m of peat in the drain face and 95DER213 was linked with 95DER218, 95DER90 and 95DER91. To date these sites have been only partially excavated.

Level 3
Running from east to west, 96DER201 was a small brushwood togher, 6.4m x 5.4m, associated with the natural wood and a small number of worked timbers (95DER92). Located 15m south-west of these sites was a trackway, 95DERl3, which ran for a minimum length of 13.5m from the glacial till of the ridge where it was a max. 10.8m wide, decreasing to 3m wide at its western limit. This site had a max. depth of c. 0.4m and was composed of irregularly set large roundwoods and some brushwood with a substructure of densely packed brush-wood at its eastern limit (as excavated). 96DER210 was a togher, located immediately west of 95DER13, and measured 6m east-west and 5m north-south. It had a roundwood superstructure and a fragmented brushwood substructure with an overall depth of 0.3–0.4m. Part of a wooden artefact was found associated with this site.

All of these sites were delimited on their western side by a stake row, 96DER209, where a total of 40 stakes, set roughly 0.7m apart with an average diameter of 0.55m, were traced for 39m north-south. In addition to these sites, 96DER208 and 96DER205, located approx. 7m south of 95DER13 on the southern side of the ridge, show evidence of the in situ use of the predominantly alder carr forest. This was seen as singular axe-marked timbers found in association with the natural root systems. Three sites were also excavated which proved to consist of naturally-felled wood and root systems, with no worked wood in association. These were 95DER7, 8, 14 and 95DER94.

Post-excavation work on this project is ongoing, and at the time of writing these results are at a preliminary stage. Excavations of site 95DER2 18 and other sites in this southeastern area will continue during the 1997 season.

96E203 and 96E298 (Tim Coughlan and Paul Stevens)
95DER18
Excavation of the trackway 95DER18 commenced under Tim Coughlan in July 1996 (96E203) and continued until September 1996, at which point a second phase of excavation commenced under the direction of Paul Stevens (96E298). In November 1996, owing to increasing demand in other areas of the project, an extension to the terms of reference of the second licence was sought and agreed by the OPW. A second site (95DER75) at the far west of the TMF was excavated, together with an extensive resurvey of the western area of the TMF.

Trackway 95DER18 was identified in the IAWU assessment (1995) as a stone, soil and timber trackway orientated east-west and running right across the centre of the bog peninsula for at least 520m. A sample of oak plank recovered from a Bord na Mona drain face in 1995 produced a dendro date of 1542±9 BC. The trackway appeared to be running through fen and transitional peats. It lay on very highly humified amorphous peat, possibly the result of a short dry phase, and very soon after its construction was inundated by very wet raised bog conditions. Excavation of this trackway consisted of eight cuttings under 96E203 and one cutting under 96E298, largely concentrated at the western extent of the track. These excavations identified four construction phases:

Phase I: This was the primary phase of construction and took the form of two roughly parallel stake rows no more than 1.4m apart. The stakes in each row averaged 60mm in diameter and were c. 0.4m apart. The stake rows were observed in all but two cuttings at the western landfall. No evidence of stake-holes was observed in the mineral soil at that point, but areas of charcoal observed at this stratigraphic level possibly represented a deliberate burning episode.

Phase II: This phase was noted in the four cuttings to the west. It appears to represent a foundation layer, possibly the result of localised wetness within the peat. It consisted of longitudinal bunched brushwood, roundwoods and sand laid in short stretches, c. 1.4m wide, c. 90mm deep and no more than 1.1 m long. It was largely contained within the two rows of stakes, sealing them in places.

Phase III: This represents the largest component of the track and consisted of part or all of the following: sandstone flags, sandstone boulders and cobbles, limestone stones, gravel, sand and silty clay. The constituent parts were laid down to form a walking surface 1.2–1.4m wide. At the eastern end, lying on mineral soil, a maximum width of 2.2m of tightly packed small flags/cobbles formed a metalled roadway. Further west into the bog the stones and soil form a rough stepping-stone arrangement.

Phase IV: This was perhaps the most complicated phase and was represented in three cuttings. It contained timber planks, roundwoods and/or piles of sandstone which were used to repair the sunken stone phase, possibly occasioned by areas of localised wetness and an increasingly wet environment.

95DER75
The trackway or togher 95DER75 was identified in the IAWU assessment as a brushwood and roundwood togher. It was visible for at least 45m and was orientated east-west. It appeared to be lying in fen peat above a layer of forest peat or carr and sealed by fen peat. Two cuttings were opened towards the end of the season and two phases of construction were identified within this structure.

Phase I: This phase was only represented in one cutting. It consisted of diagonal and transverse roundwoods with an average diameter of 0.4m, occasionally pegged down and interspersed with large felled tree-trunks averaging 0.3m in diameter.

Phase II: This phase represented a superstructure. It consisted of tightly bunched brushwoods, 1.2m in width, laid longitudinally, occasionally with intertwined transverse roundwoods for stability, and pegged down on either side by stakes, roughly 60mm in diameter, driven in at an angle towards the structure. The structure was c. 2m.wide and 0.15m deep.

Monitoring
Monitoring of drainage operations (deepening of the Bord na Mona drains) resulted in the discovery and recording of 43 potential new sites in the western and north-western TMF area. These sites have been incorporated into the schedule for the second season of excavation which will commence in the spring of 1997.

Rath House, Ferndale Rd, Rathmichael, Co. Dublin