1997:180 - LAMBAY ISLAND, Dublin

Previous work on the site had demonstrated evidence for two related activities dating from the Neolithic period: firstly the working of the porphyritic andesite outcrop which forms the sides of a small valley for stone axe production, and secondly the occurrence of a number of related features on the valley floor under and partially truncated by a cultivation soil which was the result of intensive 19th-century spade cultivation.

The objectives of the 1997 season were to expand the area of excavation in the valley floor area to evaluate the extent and nature of the archaeological features, to continue and complete the excavation of the working area out from the rock face in Cutting 1/1W and Cutting 4, and to examine spatial variability in the working of the porphyritic andesite.

The valley floor
The excavation area was enlarged by extending Cutting 5, consolidating the Test-pit 2/Cutting 3 area and by opening new areas of excavation to the east (Cutting 7) and south-east (Cutting 8) of the areas opened previously. This extended the excavation towards the west-facing outcrop that forms one of the sides of the valley. Both Cuttings 7 and 8 were 4.5m x 2m in size. Struck flint, occasional hammerstones and rubbers and a small number of Neolithic pottery sherds were found in the cultivation soil.

A distinct difference can be seen in the stratigraphic sequence beneath the cultivation soil within the enlarged excavation area. In the western part of the area it was possible to recognise a very thin interface between the cultivation soil and the underlying subsoil. It appears that this interface represents the base of disturbance/truncation of the original palaeosol. Here some additional truncated features of Neolithic date cut into the subsoil were found which can be compared with those previously recognised. In the eastern part of the area underlying the cultivation soil is a brown to dark brown sandy loam (C707) of variable depth, over subsoil. This would appear to be the surviving portion of the palaeosol which further west has been almost completely removed through disturbance by cultivation. C707 should potentially have greater preservation of Neolithic features and a number have been identified to date. There is a considerable quantity of stones in and on the surface of C707 and it seems likely that some of these possibly represent other features.

The additional features are important in defining the nature of Neolithic activity on the floor of the valley. It appears that there are now at least seven large pits (F1, F7–9, F11, F14–15) filled with porphyry debitage and other cultural material. F11 has several characteristics prior to excavation that suggest a similarity with the larger, excavated pit, F1, including a focus on deposition around a large stone in the pit. The stone spreads to the north of F8 and F15 may represent further stone-filled pit features.

Along with the pits, a number of shallow trenches cut into the subsoil or C707 can now be recognised. Of these the most significant is F10, which can now be identified as being cut by F7 and running to the east/south-east before turning to the north, where it is cut by rabbit burrow activity. It would appear likely that these trenches may represent a number of different structures.

Cutting 1/1W and Cutting 4
This is the excavation area to the south of the main valley floor area discussed above. The primary purpose of this area of excavation was to examine the nature of the build-up against the rock face and its extension across the valley floor. Excavation of Cutting 1/1W was completed in 1997. This work included the excavation of the 1m-wide baulk between them, giving an area of 7m x 1.5m. Cutting 4 (4.3m x 1.5m) is separated from Cutting 1W by a 0.5m-wide baulk.

The stratigraphic sequence is complex. The dominant feature seen is the build-up of different layers of porphyritic andesite debitage with lithic material associated with the working of the rock (cobbles, hammerstones and rubbers) and with other activities (flint). In these layers the debitage occurs in consistent shape categories but the proportions of these vary in different layers. This build-up has been truncated as the result of 19th-century cultivation, as shown by the presence of a field ditch and associated cultivation furrows. Rabbit burrow activity is present down to the subsoil. Cultural material is concentrated in contexts C107, C108 and C111. On the other hand, struck flint was found in situ down to the surface of the palaeosol (here referred to as C115; this is equivalent to C707 in the valley floor area of excavation). Porphyritic andesite with ground surfaces was found in a number of contexts, including a partially ground and polished rough-out in C111. A couple of possible anvil stones with settings to stabilise them were also identified in plan and section at different levels in the stratigraphic sequence.

This stratigraphic sequence can be recognised as continuing into Cutting 4. Excavation in Cutting 4 revealed that the major basal layer of the porphyritic andesite material, C408, is the stratigraphic equivalent of C111, overlying the palaeosol, which has some smaller porphyritic andesite pieces impressed in the surface. The basal slabs in C408 are quite large and appear to have been deliberately placed to level up the ground surface. Again the build-up includes non-porphyritic andesite lithic material, including hammerstones, rubbers and struck flint. Close to the southern baulk of the cutting there was a small cut feature in the palaeosol and subsoil and in this were a number of flint blades and flakes, part of a cache as a large number were also found in a rabbit burrow immediately to the north and on the surface of the palaeosol in the immediate vicinity. This cache was sealed by C408.

A number of samples for pollen analysis were taken from the palaeosol in Cuttings 1W and 4 by Tom Cooney (Botany Department, Trinity College Dublin). Preliminary analytical results suggest open conditions with some shrub/tree cover. This palaeoenvironmental scenario is supported by the species identification of the charcoal samples by Ellen O'Carroll (Irish Archaeological Wetland Unit), indicating scrub but also woodland cover.

Cuttings 9 and 10
To obtain a cross-section in plan and section of the sequence of archaeological deposits across the valley two new cuttings were opened on the same axis as Cuttings 1/1W and 4. Cutting 9 (3m x 1.5m) is separated by a 1m-wide baulk from the west end of Cutting 4, and Cutting 10 (3m x 1.5m) is separated by a 1m-wide baulk from the west end of Cutting 9. In Cutting 9 the current excavation surface is within the cultivation soil. The west end of Cutting 10 adjoins the east-facing side of the valley and a small modern (19th-century) clearance cairn. In Cutting 10 a complete polished porphyritic andesite axe was found lying in the topsoil immediately under the sod.

Test-pits 6-9
To test the stratigraphy in the small valley immediately to the west of the valley which is the focus of the excavation project a series of 1m x 1m test-pits were excavated. The most interesting results were from TP7. Here the test-pit exposed the western edge of a build-up of porphyritic andesite against rock outcrop over the subsoil with apparently little later disturbance. The material contained a high proportion of ground and polished pieces and a large portion of a pecked and partially ground rough-out. A sandstone rubber was also found. The results of the excavation of this test-pit indicate what appears to be an undisturbed porphyritic andesite axe quarrying and production area.

Comment
The results of the 1997 season confirm the importance and potential of the site, both from the point of view of axe production using porphyritic andesite and the associated Neolithic activity on the valley floor. The results of the excavation of TP7 are important in indicating that the quarrying activity and the working of the porphyritic andesite for axe production certainly extended beyond and to the west of the valley that has been the focus of work to date. The find of a complete polished porphyritic andesite axe in Cutting 10 emphasises the unusual character of the Lambay site in having all stages of axe production represented.

Excavation in 1997 was grant-assisted by funding from Dúchas The Heritage Service, Department of Arts, Heritage, Gaeltacht and the Islands, on the recommendation of the National Committee for Archaeology of the Royal Irish Academy.