1999:741 - CASTLETOWN BOG, Castlearmstrong, Offaly

The site was a linear plank trackway traced for 350m across the western extent of Castletown Bog. It has been dated to AD 684–9. Three cuttings measuring 10m x 2.5m were excavated, one at either end and one in the centre of the trackway.

Cutting 1 was opened at the northern end of the trackway to reveal the superstructural planks and roundwoods, which ran in a north-east/south-west direction. The superstructural layer in this cutting comprised three split planks and two roundwoods. The planks were laid end to end and were quite narrow, only 0.17m in maximum width. The planks were tangentially and radially split oak timbers, and their upper surfaces had been milled by Bord na Móna operations. The central portion of the cutting contained two roundwoods running parallel to the planks in a north-east/south-west direction. The planks ran under a peat pool at the southern end of the cutting. The upper plank was visible at the southernmost end of the cutting, where it emerged from the pool.

After the superstructural planks were lifted two substructural layers of wood were exposed. The first layer comprised five substructural transverses, the second a scattering of planks, wood chips, bark, brushwood and roundwoods. The five transverses (Layer 1) were exposed along the length of the cutting; they held the upper plank in place and prevented the walkway from sinking into the peat. Layer 2 was an irregular arrangement of densely compacted timbers found mainly in the middle and southern section of this cutting under the pool area. This second layer of wood was probably thrown down into the cutting, where it was exceptionally wet and where the upper plank walkway needed extra support. Hazelnut shells were found throughout the cutting.

Cutting 2 was placed at the central portion of the trackway c. 90m south of Cutting 1. The disturbed super- and substructural layers of the single plank walkway were revealed in this cutting. The superstructural layer, which was mainly confined to the southern half of the cutting, had been disturbed, possibly in antiquity. It was composed of a degraded roundwood and oak fragments at the northern end and a longitudinal plank and roundwood at the southern end. The plank and roundwood at the southern end of the cutting had slid off the substructural runners; they were lying to the west of the substructure, at an angle of 45º. The roundwood at the northern end of the cutting had also slipped away from the main body of the trackway.

The substructural layer of the trackway in this cutting was composed of approximately eight timbers with a lot of wood chips, parts of planks and brushwood rods. This array of wood was laid down in a haphazard fashion and probably functioned as infilling providing extra support to the superstructural walkway. The substructural timbers were closely spaced and were composed of planks, roundwoods and a single brushwood. The transverses were all found at the southern half of the cutting, alongside the eastern edge of the baulk. Five of the transverses extended beyond the eastern baulk. Four squared oak pegs were found in the central area of this cutting. These pegs would have also provided support to the superstructural walkway.

A leather ankle shoe was found beside the area of densely compacted wood in the central part of the cutting. It was front-laced, at the heel and the toe, and the sole was worn through, probably through walking. A 7th-century pedestrian who walked along the plank trackway may have lost this shoe.

Cutting 3 was c. 100m south of Cutting 2. The trackway lay c. 0.5m below the field surface. This cutting exposed the classic linear plank trackway composed of a superstructure of oak planks supported by a lower layer of two transverses. The superstructural layer was composed of two longitudinal planks laid end to end, converging at the northern transverse. A number of pegs were found on the western side of the cutting. These pegs did not provide any form of physical support to the togher as they were found c. 0.6m away from the main trackway elements. The pegs may have been laid down to mark out the routeway of the track before its construction.

This trackway will be studied in association with the adjacent dryland monuments, which include St Manchan's church and a number of ringforts and cashels.

Windsor House, 11 Fairview Strand, Fairview, Dublin 3.