J Wetland Archaeol 6

The paper discusses the link between decisions about the treatment and conservation of waterlogged wood, and the intended final outcome of treatment (research purposes, permanent museum acquisition, or display). Treatment may involve study, recording, sampling and re-burial with no other form of intervention, or might require stabilisation using chemicals, followed by drying. When interventive treatment is necessary, performance standards exist which will allow for objective evaluation of the outcome. The paper summarises these parameters, and includes a brief description of the methods employed at the Canadian Conservation Institute to determine and evaluate a treatment regime. The focus is on the use of polyethylene glycol (PEG) as a non-toxic and effective treatment of waterlogged wood.

A desk assessment was carried out to identify archaeological sites and findspots in peatland locations in Northern Ireland, in order to estimate the potential for further archaeological fieldwork. Sites in or under blanket, raised, fen and marsh peat were considered. The majority of sites were identified from information contained in the Northern Ireland Sites and Monuments Record (NISMR). In addition, all NISMR site locations were examined in relation to areas of extant peatland, enabling additional sites to be recognised. The Ordnance Survey Memoirs provided further details about sites and finds known from peatlands in the early-nineteenth century. Museum and published catalogues were also examined to estimate the quantity of finds recovered from peatlands. The combined sources suggest that there are more than 1,000 archaeological sites and 763 findspots currently known from Northern Ireland's peatlands. The majority of the sites are associated with blanket peat, reflecting the greater extent of this peat type and the prevalence of stone monuments there. Sites in raised bogs are less well known, tending to be of timber, and are possibly under-represented in the record. Other lowland peat types probably preserve a range of archaeological sites but survey has not yet been conducted in these environments in Northern Ireland.

Compared to conventional electrical conductivity surveys the spectral induced polarisation (SIP) method measures the frequency dependence of conductivity amplitude and the phase shift between injected current and the resulting voltage signal. The phase shift is related to polarisation effects of materials. Laboratory investigations of peat, wood and soil samples show a considerable variation in the spectra of conductivity amplitude and phase shift. From the results of laboratory investigations it could be concluded that characteristic features of the phase spectra can be used to detect wooden relics of trackways or pile dwellings in the wetland's subsurface. Field surveys in Germany prove that the method of spectral induced polarisation can be considered as a prospecting tool for archaeological surveying in wetlands. A shallow trackway could be clearly identified by higher phase values measured at a frequency of 3Hz. The weak phase signal of a somewhat deeper plankway only became visible after data processing.