Christopher Paul Green

Holocene environmental changes in the Lower Thames Valley, London, UK: Implications for understanding the history of Taxus woodland

A radiocarbon-dated multiproxy palaeoenvironmental record from the Lower Thames Valley at Hornchurch Marshes has provided a reconstruction of the timing and nature of vegetation succession against a background of Holocene climate change, relative sea level movement and human activities. The investigation recorded widespread peat formation between c. 6300 and 3900 cal. yr BP (marine ‘regression’), succeeded by evidence for marine incursion. The multiproxy analyses of these sediments, comprising pollen, Coleoptera, diatoms, and plant and wood macrofossils, have indicated significant changes in both the wetland and dryland environment, including the establishment of Alnus (Alder) carr woodland, and the decline of both Ulmus (Elm; c. 5740 cal. yr BP) and Tilia (Lime; c. 5600 cal. yr BP, and 4160–3710 cal. yr BP). The beetle faunas from the peat also suggest a thermal climate similar to that of the present day. At c. 4900 cal. yr BP, Taxus (L.; Yew) woodland colonised the peatland forming a plant community that has no known modern analogue in the UK. The precise reason, or reasons, for this event remain unclear, although changes in peatland hydrology seem most likely. The growth of Taxus on peatland not only has considerable importance for our knowledge of the vegetation history of southeast England, and NW Europe generally, but also has wider implications for the interpretation of Holocene palaeobotanical records. At c. 3900 cal. yr BP, Taxus declined on the peatland surface during a period of major hydrological change (marine incursion), an event also strongly associated with the decline of dryland woodland taxa, including Tilia and Quercus, and the appearance of anthropogenic indicators.

The timing and causes of the Neolithic elm decline: New evidence from the Lower Thames Valley (London, UK)

Abstract Two new multi-proxy records of environmental change are provided from Horton Kirby Paper Mill and Old Seager Distillery in the Lower Thames Valley. Each site has evidence for a decline in elm woodland, which at Horton Kirby Paper Mill is recorded earlier than any other published record from the British Isles: sometime between 7320 and 7240 cal BP. Scolytus scolytus/S. multistriatus (the vectors for Dutch elm disease) are recorded after the decline in both sequences, adding to the number of sites with such evidence in the British Isles. Evidence of paludification and human activity are also recorded at the time of the elm decline reinforcing the multi-causal hypothesis. Integration of these results with 21 palaeoenvironmental records has produced a large number of well-dated, multiproxy records of the elm decline in this part of the UK. On the basis of this dataset, a classification system for categorising the relationships between the causal factors of the elm decline is proposed and recommended for future studies.

Holocene palaeoenvironmental change and the impact of prehistoric salt production in the Seille Valley, eastern France

The Seille Valley in eastern France was home to one of Europe’s largest Iron Age salt industries. Sedimentology, palynology and geochronology have been integrated within ongoing archaeological investigations to reconstruct the Holocene palaeoenvironmental history of the Seille Valley and to elucidate the human–environment relationship of salt production. A sedimentary model of the valley has been constructed from a borehole survey of the floodplain and pollen analyses have been undertaken to reconstruct the vegetation history. Alluvial records have been successfully dated using optically stimulated luminescence and radiocarbon techniques, thereby providing a robust chronological framework. The results have provided an insight into the development of favourable conditions for salt production and there is evidence in the sedimentary record to suggest that salt production may have taken place during the mid-to-late Bronze Age. The latter has yet to be identified in the archaeological record and targeted excavation is therefore underway to test this finding. The development of the Iron Age industry had a major impact on the hydrological regime of the valley and its sedimentological history, with evidence for accelerated alluviation arising from floodplain erosion at salt production sites and modification of the local fluvial regime due to briquetage accumulation on the floodplain. This research provides an important insight into the environmental implications of early industrial activities, in addition to advancing knowledge about the Holocene palaeoenvironmental and social history of this previously poorly studied region of France.

Environmental setting: geoarchaeological investigations and environmental analysis

The site of Blick Mead has attracted an unusual degree of interest. In addition to its intrinsic importance as a Mesolithic site, its location less than two kilometres east of Stonehenge and its temporal overlap with the massive Mesolithic posts in the Stonehenge carpark mean that it is the earliest settlement site in the region of the monument (e.g. Parker-Pearson et al. 2015). The site has provided an animal bone sample of modest size but great importance. Faunal remains reveal much about the socio-economic basis and cultural practices of their time. Very few Mesolithic faunal assemblages are known from Britain, so any new discovery greatly advances our understanding of the period. In the following report we do two things. First, we present a zooarchaeological analysis of the material; the most remarkable aspect of this is the high proportion of aurochs (Bos primigenius), so far unequalled at any other Mesolithic site in Britain and the near continent. Second, we present a stable isotopic analysis of aurochs teeth. We thus aim not only to get a better understanding of the site and its inhabitants, but also of the life of the extinct ancestor of modern domestic cattle, by focusing on their diet and migratory habits. The current excavations at Blick Mead began in 2005. Mesolithic remains have been discovered in Trenches 19, 22 and 23. The assemblages of struck flint and burnt stone are considerably larger than those at most other Mesolithic sites in Britain (Jacques, this volume), and indicate a substantial Mesolithic occupation at the site. The quantity of flint suggests that this was a home-base used over many years. The radiocarbon dates from six animal bone and tooth enamel fragments, which span the period between 7596-7542 cal BC and 4846-4695 cal BC, reinforce the suggestion that the site marks a ’persistent place’ in the landscape (Jacques, this volume). Parts of this assemblage were initially examined, and its importance understood, by the late Tony Legge. We dedicate this study to his memory.