Extension to New Denham Quarry (Phase 5) Denham, Buckinghamshire: Geoarchaeological Mitigation and Updated Deposit Model

Wessex Archaeology was commissioned by Summerleaze Ltd ('the client') to produce a report outlining the results of geoarchaeological mitigation on land adjacent to New Denham Quarry, Denham, Buckinghamshire (the 'Site'), centred on NGR 504400 184800 (TQ 04400 84800). The proposed development comprises the expansion of the existing New Denham Quarry to the east, between the existing quarry and Knighton-Way. As, the Site is located in the Colne Valley, which contains one of the most important concentrations of Terminal Upper Palaeolithic and Mesolithic archaeology in Britain, often in association with deposits of a high palaeoenvironmental potential a programme of geoarchaeological mitigation was recommended. The evaluation comprised the excavation, sampling and recording of a 50 m long stepped trench targeting a palaeochannel identified during a previous borehole survey and deposit modelling exercise. The principal aim of the geoarchaeological trench was to evaluate fills of the palaeochannel and understand the relationship between the channel edge and presence of flint artefacts. The current geoarchaeological evaluation confirmed presence of an approximately 2 m deep channel filled with minerogenic fluvial deposits sealed by gravels with an organic matrix containing charcoal fragments, with their occurrence mainly restricted to the gravel ridge next to the palaeochannel. The fill of the palaeochannel is considered to be of a Holocene date. A change in climatic condition at the Pleistocene-Holocene transition is marked by deposition of fine-grained alluvium followed by the formation of a peaty soil buried. The preservation of a peaty soil seems to be localised to the near vicinity of the channel. Archaeological test pitting adjacent to the palaeochannel produced a small quantity of worked flints derived predominately from the buried soil and alluvium. The archaeological material indicates the location of a possible campsite near the palaeochannel, though the assemblage appears partially reworked by a fluvial action. Alluvium sealed the Buried Soil, and a further layer of alluvium in areas where the buried soil was absent. A characteristic band of black clay demarked the formation of the upper alluvium. Based on research at Three Ways Warf the top of the sediment sequence would be equate to the Late Mesolithic period. No archaeological material was recovered from the basal alluvium, but the black clay has high potential to contain material suitable for radiocarbon dating and palaeoenvironmental remains which may shed light on human-environment relationships. The uppermost deposit recorded at the Site was thick Made Ground deposit suggesting truncation of the Holocene sequence. As the key Holocene layers are located within 1.0m below the ground surface, the proposed extension of the quarry will affect the sequence and any archaeological remains within it. The proposed quarry expansion will impact on Pleistocene and Early Holocene deposits with a high geoarchaeological and archaeological potential. Consequently, programme of targeted paleoenvironmental assessment and scientific dating is recommended on samples retained from Trench 1 from the fills of the palaeochannel and overlying alluvium and buried soil containing struck flints, to establish the date of the deposits, preservation and concentration of key palaeoenvironmental indicators and potential of these remains to contribute to our understanding of human-environment relationships at the site and Colne Valley.