2016:396 - Portmarnock, Dublin

A sub-surface ditched enclosure (DU015-014001) was excavated (pre-planning) to the east of a permitted housing development to the south of Station Road, Portmarnock, but not within that development area. The excavation followed the rescue excavation of another ditched enclosure identified during monitoring of topsoil removal within the permitted development area under licence no. 16E0101. The work was carried out for Sherman Oaks Ltd. The site was located on the east side of the railway line at Portmarnock and fronting onto the south side of Station Road and is known as Phase 1B.

Targeted test excavation of the possible sub-surface enclosure which was indicated on aerial photography took place during the Phase 1A investigations in August 2016 (16E0101) and confirmed the presence of a sub-surface ditched enclosure. The enclosure was bisected by a previously archaeologically monitored pipeline/haul road (McLoughlin 2016, Licence No. 16E0101, elsewhere on this site), and its northern extent is contained within the conservation area devised for the mound at Portmarnock (DU0015-014). Two features were identified during monitoring for the pipeline / haul road and resolved (Area 3a) but no ditch was apparent. Further to consultation with the National Monuments Service of the DAHRRGA, it was agreed that the ditched enclosure (except the northern portion within the constraint area for the mound) could be excavated.

Excavation of this site took place from 9 January 2017 over a 14-week period. The enclosure was slightly elliptical or sub-circular in plan and measured a maximum external diameter of 77m east-west x 70m (68m east-west x 60m internal diameter), with an entrance to the east (within the pipeline/haul route). The ditch cut was substantial, measuring up to 5.5m wide and 1.65 deep. During the test excavation, a wooden hoop was recovered from close to the bottom of the ditch and this has been dated to 1348±27 BP (calibrated to AD 641-763, 2 sigma) firmly placing the ditched enclosure in the early medieval period and suggesting that this enclosure and the previously excavated enclosure (Licence No. 16E0101) are contemporary.

Finds and dating evidence places the site in the late Iron Age and early medieval period. Finds recovered from the ditch during the excavation include early medieval imported pottery (LRA 1 and E ware), wooden artefacts from the base of the ditch, stone tools and worked antler artefacts. A huge volume of animal bone was recovered from the ditch including cetacean bones, and similar to the Phase 1A enclosure the proportion of cattle was very high and suggestive of feasting. Cereal drying (kilns) and metalworking activity were evident on site and there was one adult male inhumation in the interior of the enclosure (radiocarbon dated to AD 410-607). The excavated portion of this site has now been built on and the northern part of the enclosure is preserved within a 20m buffer zone around the Portmarnock mound (DU015-014).

Under this licence another enclosure, which was also identified from aerial photograph,y was tested c.200m south of the enclosure detailed above. This was carried out in December 2016 and confirmed the presence of a large double ditched enclosure, from which no dateable artefacts were recovered. The inner enclosure measures 39m north-south x 30m and the outer enclosure 106m north-south x 87m. Animal bone and shell recovered from the test sections indicate that the enclosure is similar to the other enclosures identified so far in the same field (the enclosure excavated under licence 16E0101 and site DU015-014001 excavated under licence 16E0613). Based on the similarity of this site to the other enclosures it is likely to date to the early medieval period.

Courtney Deery Heritage Consultancy, Lynwood House, Ballinteer Road, Dublin 16