M3 Clonee-North of Kells Motorway Scheme

Lismullin National Monument (A042 & E3074)

Director’s Excavation Progress Report 1

Aidan O’Connell

Archaeological Consultancy Services

24 August 2007

Introduction

Site works commenced on 7 August 2007, following approval to commence from the Minister’s

Advisory Committee on 2 August.

As per standard procedure all works on site are recorded by reference to a grid which divides the

site into 10m2 areas. In addition the site has been divided into four separate areas or quadrants:

Quadrant A at NE, Quadrant B at SE, Quadrant C at NW and Quadrant D at SW (Fig 11).

The initial site clean-back and supplementary pre-excavation plan was carried out from 7–13

August in Quadrant A. Following additional geophysical survey and soil sampling for

geoarchaeological study, as described below, excavation of the planned features in Quadrant A

commenced on 15 August.

The excavation is being carried out by twenty-eight archaeologists divided into four teams, each

led by a senior supervisor. Supervisory staff attend weekly site meetings to review the ongoing

works.

Geophysical Survey

A magnetic susceptibility survey of Quadrant A was undertaken by Earthsound on 13 August.

This detected a number of discreet zones which appear to relate to natural geology (Fig 22). At

the northeastern corner the high readings appear to relate to an area of underlying boulder clay, at

the northwestern corner and along the eastern side of Quadrant A the low readings refer to

underlying gravels and sand respectively. At the southwestern corner, the high reading may be

due to the presence of the palaeosoil that is located around the inner enclosure. This soil has been

left in situ to be excavated and recorded as part of the ‘key area’ identified around the inner

enclosure.

Geoarchaeological sampling

Geochemical sampling

On completion of the clean-back and geophysical survey in Quadrant A and in advance of the

commencement of excavation, geoarchaeological samples of approximately 200g (1 small bag)

were collected from the subsoil at 5m grid intervals, on 14-15 August. Approximately 100

samples were collected from Quadrant A. The grid samples are registered in a separate

geoarchaeological sample register and are being retained on site for future assessment and

analysis.

Dr Steven Lancaster (Headland Archaeology Ltd) visited the site on 21 August to review the

sampling methodology. A supervisor has been assigned to specifically coordinate sampling on

site in accordance with the methodology agreed with Dr Lancaster, to ensure consistency of

approach. In addition to grid samples, small sub-samples of all excavated archaeological deposits

are being retained for geo-chemical analysis. The sampling strategy was reviewed to ensure that

sufficient and appropriate samples were being retained for each requirement.

During this visit the excavated features in Quadrant A were examined. This included a box

section excavated through two enclosure postholes, described below. This section had revealed a

thin deposit layer between the postholes which was interpreted as a thin layer of palaeosoil and

subsoil which had survived in a natural hollow. It was proposed that this palaeosoil would be

sampled using a kubiena tin.

Additionally, a proportion of half-sectioned enclosure postholes were examined in order to

establish their formation process. It was proposed that post-hole F3323 would be box-sectioned

and sampled using a kubiena tin to include subsoil, primary and secondary posthole fills for geochemical

analysis.

The potential buried soil within the interior is located around the inner enclosure and has not been

cleaned back yet although a small portion of it extends into the quadrant currently under

excavation. This soil will be sampled at a smaller grid interval of 2m. Some additional localized

patches or areas of darker soil were noted in Quadrant A and it was agreed on site that these

would be planned and sampled for geo-chemical analysis.

Palaeonenvironmental sampling

In accordance with the method statement, a sample of all deposits and 100% of the fill material

from each cut feature in Quadrant A is being retained for dating and palaeoenvironmental

purposes. These samples will be processed through a flotation tank and sieves to extract suitable

material for analysis.

Due to the large quantity of material being generated as a result of this extensive sampling

exercise, a supervisor has been appointed, in addition to two assistants, to supervise the archiving

of samples and finds.

Excavation

Excavation is being carried out in Quadrant A. Part of this quadrant corresponds with ‘the

northwestern segment of the outer enclosure’ which was identified as one of three key excavation

areas in the Supplemental Method Statement for Lismullin National Monument (02 August

2007).

In the northwestern segment key area, the pattern of postholes is more complex and there

are a number of additional features clustered around the outer enclosure. However,

excavation has not yet extended to the areas of more complex patterns of postholes.

One of the additional features identified in this key area included a pit from the surface of

which numerous sherds of later Bronze Age coarse ware pottery have been collected.

This pit did not appear to be stratigraphically related to the outer enclosure. Considering

the early Iron Age C14 date received for the stakeholes, it was considered important to

verify this and attempt to establish the relationship between this pit and the site as a

whole. Excavation of the pit has commenced and these questions will be addressed in the

forthcoming days.

The main features recorded to date are the outer enclosure postholes in Grid 11 and the east-west

aligned linear ditch in Grids 2, 3, 6, 7 and 11.

Enclosure Postholes

Excavation of the enclosure postholes is currently concentrated in Grid 11. To date, 2 postholes

have been box sectioned, 2 postholes fully excavated and a further 17 postholes half sectioned.

The postholes have dimensions ranging between 15-23cm in diameter and between 15-23cm in

depth. The box section aided the identification of post-pipes surrounded by a second fill within

the postholes. The post-pipe consists of a dark organic fill with charcoal flecking, surrounded by

a thin pale largely sterile clay.

Preliminary examination of the half sectioned postholes on site by Dr Steven Lancaster, as

described above, concurs with the excavator’s interpretation that the posts were most likely

driven into the ground (rather than being placed into a prepared posthole) and that the clay fill

surrounding the postpipe has resulted from half driven posts being manually moved to gain more

purchase in the ground before being driven further. As described above, a thin section sample

from a specific posthole has been proposed in order to investigate this theory further.

A thin clay layer c. 2cm deep was recorded in the box section, between the two postholes. Three

possible interpretations were initially considered for this deposit:

• That it is the remains of an earthen bank, revetted by the two concentric outer rings of

posts – this might imply that there was a timber facing between the posts.

• That it is a trampled ground surface - this might imply that the outer concentric rings

delineated a processional routeway.

• That it is a localized concentration of buried topsoil/palaeosoil similar to the layer

recorded around the inner enclosure.

However, preliminary examination of this deposit on site by Dr Steven Lancaster, as detailed

above, suggests that it is unlikely to be a trampled surface or bank material. A thin section

sample of both this deposit and the underlying subsoil is to be taken for further analysis.

Linear Ditch (F3611)

The linear ditch was recorded in the first phase of excavation. It extends east-west across the site

for c.128m. Within Quadrant A of the enclosure it is 33m long by 0.95m wide by 0.4m deep and

contains between 2 and 4 fills. The basal fills appear to have silted up over time. This feature

may therefore have functioned as a drain. It appears to be later than the post enclosure (there are

no postholes cut through it) and is in turn cut by a figure-of-eight cereal drying kiln. A date range

of late Iron Age to early medieval is therefore suggested.

A range of dispersed small features including pits postholes and stakeholes have also been

recorded. While a number of additional possible features were recorded in the supplementary

pre-excavation plan subsequent excavation has discounted many of these, and the overall

distribution of features remains similar to that understood from preliminary recording.

Site Conditions

In general, conditions on site have been good since works recommenced. The sandbag cordon

has assisted in keeping excessive silt from accumulating on the enclosure during heavy rainfall

and this has been monitored and supplemented where necessary. A water bowser and hoses have

also been provided on site and have been used to maintain optimum moisture levels in dry sunny

conditions.

Lismullin National Monument, Director’s Progress Report 1 Aidan O’Connell 24 August 2007 5