County: Offaly Site name: LEMANAGHAN
Sites and Monuments Record No.: N/A Licence number: 96E0151
Author: Ellen O'Carroll, Irish Archaeological Wetland Unit, University College Dublin
Site type: Road - class 1 togher
Period/Dating: Multi-period
ITM: E 617927m, N 726455m
Latitude, Longitude (decimal degrees): 53.288101, -7.731138
A short excavation was carried out on a multiphase togher in Bord na Mona's Derrynagun bog, Co. Offaly, in July 1996. Extensive milling and drainage in that bog had exposed a substantial togher constructed from gravel, large flagstones, split timbers, roundwood and brushwood. The excavation was carried out to establish a chronological framework for the site and to understand the nature and the sequence of construction; its relationship to an ecclesiastical settlement on a nearby dryland island at Lemanaghan was also addressed.
The togher ran for 750m from the island at Lemanaghan across the bog. A cutting 10m wide and 2m long was established over part of the site in which all known construction layers were present. The excavation revealed five phases of construction. The earliest phase was a longitudinal plank walkway of three split oak planks, measuring 1m wide and 0.52m deep. This phase was dendrochronologically dated to AD 653 ± 9 (Q9281).
Phase 2 consisted of a layer of redeposited boulder clay directly on top of the planks. It was 3.4m wide and measured 0.4m at its deepest point. The boulder clay layer was very compact and was composed of coarse sand, pebbles and round stones. It had a cobbled surface, with larger cobbles flanking the edges to form a kerb. Outwashes of gravel and clay into the peat were also associated with this phase.
Phase 3 was constructed of three layers of wood forming a substructure and a superstructure. The substructure was of brushwood and roundwoods. This was overlain by a superstructure of horizontally laid split oak planks, with large amounts of brushwood and a small amount of roundwood intertwined over and under them. Two heavy roundwoods and an associated double row of posts defined the edges. The total width of this structure was 4.2m and the depth varied from 0.25m to 0.3m. This phase has been dendrochronologically dated to AD 1158 ± 9 (Q9282).
Directly above Phase 3 was a layer of Sphagnum peat up to 0.17m in depth. The development of this peat may indicate the abandonment of the site for a period of time, although heather noted in the peat indicates that the surface of the site might have been relatively dry. Phase 4, which lay on top of this, consisted of another layer of redeposited boulder clay. It was up to 2.6m wide and 0. 12m deep. It consisted of sticky clay, coarse sand, pebbles, stones and some very degraded brushwood.
The final phase of construction, Phase 5, consisted of a layer of large, flat sandstone flags up to 2.16m wide and 0.2m deep.
This togher was in use for over 600 years, as indicated by the dendrochronological dates. The first phase of construction, the plank walkway, is broadly contemporary with the establishment of the monastery by St Manchan on the island in AD 645. The earliest phase of the togher may have been associated with the monastic establishment, but as the site developed and expanded it probably became part of a network of routeways across the large expanses of bog in the midlands.
Analysis of the pear, wood and boulder clay is currently being undertaken and will be published in the full excavation report.
