2019:323 - Portmarnock, Dublin

The site was initially identified from aerial photography in 2016 and testing was carried out in December of that year to confirm the presence of ditches indicated on the photography (excavations bulletin 2016:396). At that stage an inner and an outer ditched enclosure were confirmed and based on the similarity of the fills to two other enclosures excavated in the same field (16E0101 and 16E0613) it was thought likely to be early medieval in date.

At the request of the NMS additional testing was carried out in May 2019 to further assess the potential of the interior of the two enclosures and the area to the east of the outer enclosure in Drumnigh townland.

The site comprised a large double ditched enclosure, with the eastern side of the outer enclosure corresponding with the upstanding boundary between Portmarnock and Drumnigh townlands. It is planned to preserve this boundary in situ. The inner enclosure was slightly sub-circular or oval in plan and measured 36m north-east/south-west x 29m internally and the outer enclosure was an irregular oval measuring 105m north-east/south-west x 71m internally. The course of the outer enclosure was irregular, and the depth of both ditches was variable. The inner ditch measured up to 3.2m wide x 1.44m deep and the outer ditch averaged 1.32m wide x 0.51m deep, although a 15m-stretch of the outer ditch to the north was more substantial, measuring up to 2.6m wide x 1.1m deep.

There were very few internal features and no evidence of any structural remains within either enclosure. There was no evidence for an entrance to the internal enclosure and the outer enclosure had a shallow causewayed probable entrance feature to the south. Ditches between the inner and outer enclosures appeared to have been related to drainage.

For the most part the inner ditch contained three main layers or phases of backfilling. The basal layer generally comprised stony grey clay, representing backfill of bank material, possibly deliberate. The next main layer was pure grey clay representing a phase of standing water and probably post-dated the abandonment of the site or may have been related to the reason for the abandonment of the site. The upper fills may again represent a phase of deliberate backfilling. Around the eastern side of the enclosure, sea shell deposits overlay the basal fills and are likely to have been associated with the occupation of the site, representing food waste. A moderate quantity of animal bone was also recovered from the ditch fills. Processing of soil samples yielded charred cereals, charcoal, uncharred seeds, wood and hazelnut shells.

Radiocarbon dating has indicated that the inner and outer enclosures were contemporary, with most of the dates ranging between the mid/late 7^th – late 10^th Centuries, although there was some evidence that the beginnings of the site may have been during the late Iron Age / early medieval transition. There was also evidence for some activity at the site in the early Bronze Age, in the form of a gully truncated by the outer enclosure ditch, and a late Bronze Age copper-alloy knife blade recovered from the outer ditch represents disturbance of an earlier phase of activity, either at or in the vicinity of the site.

A wooden bucket-type vessel made of yew recovered from waterlogged basal fills of the inner ditch returned a radiocarbon date range of AD 652-763. The wooden vessel, along with two tiny bone comb fragments, an iron weaving tensioner, a small amount of iron slag and a tuyere fragment are indications of domestic and small-scale industrial activities at the site. Animal bone and sea shell recovered from the site represents food waste and charred cereals indicate cereal processing at or near the site, further indicating some level of occupation.

The site, in conjunction with two other excavated enclosure sites in the immediate vicinity (16E0101 & 16E0613), and another unexcavated enclosure to the east in Maynetown (DU015-055), has been interpreted as being part of a possible assembly landscape. This is based on the presence of a cluster of enclosures, feasting evidence, a general lack of habitation evidence, some high status and late roman imported finds, a burial and an upstanding mound also in the area.

Lynwood House, Ballinteer Road, Dublin 16