Lewisham Hospital (phase 3), Lewisham (LHP04)

Clients: RTKL-UK/Mowlem plc Major & Special Projects

Authors: Graham Spurr and Jane Corcoran

Site supervisors: Julian Bowsher (evaluation) and Graham Spurr (geoarchaeological boreholes)

Wetland areas such as river valleys can have archaeological potential, even when no tangible archaeological remains exist or are likely to exist. The indirect archaeological evidence for human activity and past environmental change preserved in certain wetland areas, which does not survive on standard archaeological sites, is an archaeological resource in its own right and can itself be targeted for archaeological mitigation.

Archaeo-environmental analysis can appear at first sight relatively expensive: the remains of plants, insects, snails and pollen (etc), unlike artefacts, are not intrinsically datable and do not often provide immediately recognisable information and, as a result, the sequence studied will generally require a series of radiocarbon dates and detailed off-site examination to reconstruct past environments. But, apart from the archaeological value of such work, which provides a context and landscape setting for people's activities in the past and can very often help to make sense of archaeological distributions and enrich our understanding of the archaeology itself, archaeo-environmental mitigation can ultimately prove cost-effective to the developer. Such projects tend to involve minimal on-site work and a much larger proportion of time examining samples off-site. Thus the obstacle of archaeological excavation is rapidly dispensed with and the archaeological condition tends to have little adverse impact on the groundworks and construction programme.

This was the case at Lewisham Hospital, in the valley of the Ravensbourne, where the archaeological resource comprised the natural deposit sequence, which had potential for reconstructing the past environment and for linking it to episodes of Iron Age to Saxon activity. Two Terrier Rig ‘windowless sample’ auger holes were sunk on the site (which took just one day) and the continuous metre-long cores obtained were subsequently examined off-site, when sub-samples were taken for radiocarbon dating, and pollen and diatom analysis. Pollen analysis was able to demonstrate indirect evidence for anthropogenic activity in the form of cereal pollen and weeds of cultivation, and historic changes in the river regime were also recorded in the sediments sampled.

In addition, an extremely old radiocarbon date (from about 31,000 years ago) was obtained from organic lenses within the gravels; this provides evidence for the preservation of deposits pre-dating the Last Glacial Maximum within the Ravensbourne valley. Such evidence very rarely survives, as it has generally been eroded during the large-scale remoulding of the landscape that took place at the end of the last cold stage (15,000–10,000 years ago). The dated deposit is associated with a part of the last cold stage known as Oxygen Isotope Stage (OIS) 3. This OIS lasted from 60,000 to 25,000 years ago and was basically cold and dry. However, it was typified by a sharply oscillating climate with short cool episodes interspersed with milder spells — during one of which the sampled organic sediments probably accumulated. As OIS 3 lies at the transition from the Neanderthals to anatomically modern humans, the deposits recorded within the gravels on the site are of some interest archaeologically, although Palaeolithic finds of this date would not be expected, as they are very rarely found in Britain.

This site report is extracted from MoLAS 2004: annual review