1990:032 - ST HELEN'S, Booterstown, Dublin

In May-June 1990 Archaeological Development Services Ltd excavated a site at St Helen's, Booterstown, Co. Dublin (townland and parish of Booterstown, barony of Rathdown). The site came to light in aerial photography and is listed in the Sites and Monuments Record for Co. Dublin. The field in which it lies, part of the old St Helen's estate, is open pasture and slopes gently from south to north towards the sea, some 1100m to the north; the site itself is located between the 34m and 35.5m contours. The purpose of the present trial excavation, undertaken in advance of housing development, was to assess the nature of the site.

On the aerial photograph the site showed up as slightly less than half of a circular crop mark, c. 50m in diameter. It was located by means of machine-dug trenches, each c. 2m wide, c. 1.2m deep and c. 12-15m long, intersecting the line of the crop mark on the north, south, east and west. In each case a backfilled ditch was noted in the trench sections, confirming that the crop mark represented a circular ditched enclosure. The excavation concentrated on examining the stratigraphy of the ditch profiles in the trenches and investigating the interior of the enclosure by means of two further cuttings, 25m long and 2m wide, extending from the north and west trenches towards the centre, and a 6m square cutting in the centre of the enclosure. The internal cuttings were all excavated by hand, as was one section of the ditch, at the outer end of the west cutting.

The ditch was substantial, measuring approximately 51.5m in overall (external) diameter, 2.2m in width and 1.7m in depth and varying between U-shaped and truncated V-shaped in section. On the aerial photograph it appears almost perfectly circular in outline, but it was not feasible to excavate sufficient of the ditch to confirm this. Stratigraphy was examined in detail in the south and east trenches, but examination of the base of the ditch was hampered by the water table. A spread of relatively large stones near the base of the ditch suggests that it was intended to function as a form of French drain. This is borne out by an extremely sticky silty clay layer immediately above the stones, which was almost certainly water-deposited. The remainder of the ditch was filled with a deep, homogeneous deposit of light brown silt loam, which seems to reflect a deliberate episode of backfilling. Many sherds of modern pottery and glass were found in the upper levels of this layer, although these seemed to die out near its base. The ditch was sealed by a dark brown ploughsoil layer which covered the entire site to an average depth of 0.25-0.3m. It would appear that the ditch was largely backfilled in a single, deliberate operation. No evidence was found for an accompanying bank.

136 square metres were excavated in the interior of the enclosure. A uniform stratigraphy was found throughout, with the deep plough soil giving way directly onto the light brown silt loam B horizon, which in turn directly overlay the C horizon boulder clay. No archaeological features were noted in the ploughsoil or B horizon, which was excavated to a depth of some 0.15m - 0.2m. Modern pottery, glass and metal fragments were noted; nothing of earlier date occurred. The only possible exception to this was a short linear pit or trench with a fill of marine mollusc shells, found at the south end of the north trench. This midden deposit was laid down and buried in two separate episodes in a specially dug pit or trench. Unfortunately no artefacts or other datable material were found in excavating it.

No other features were found within the enclosure. Indeed the stratigraphy observed was entirely natural, with no trace of archaeological deposits. No datable material was found in the lowest ditch fill layers or in the shell midden, but the pottery and glass found in the upper ditch fill, B horizon and ploughsoil were uniformly of modern date. The concentration of stones and accumulation of silt near the base of the ditch is evidence for its functioning as a French drain. All of this suggests that the ditched enclosure is of modern date and is best classified as a tree-ring, even though no evidence for tree root activity was found.

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