Client: Various (including Bristol and Region Archaeological Services (BaRAS), Cotswold Archaeology, Pre-Construct Archaeology, and English Heritage) The Environment Agency
Background:Over the last decade, ARCA have worked extensively in central Bristol gaining considerable experience of sampling, assessing, and modelling the stratigraphy formed by the rivers Avon and Frome and archaeological deposits associated with development of the historic city. The projects carried out by ARCA have focused on investigating and understanding changes in the landscape of central Bristol over the last seven millennia, the nature of prehistoric human activity in the area, and response of medieval and later communities to environmental change as the city was founded and grew.
Major projects undertaken by ARCA include a series of borehole investigations in the Harbourside and Canon’s Marsh area of the city, the Cabot Circus development, and a recent English Heritage funded project modelling the presence of waterlogged deposits throughout the city.
Geoarchaeological Investigations central Bristol (2004 – present)
Results: During much of the last 10,000 years the Avon and Frome valleys in the area of central Bristol were subject to intertidal conditions – i.e. the area was covered with estuarine mudflats and marshes and subject to flooding at high tide. Under many parts of central Bristol by the banks of the Avon, thick deposits of intertidal sediments (mostly clays, silts and sands) occur, overlying Pleistocene (last 2 million years) river gravels.
Investigations at a series of sites in Canon’s Marsh, situated between Bristol cathedral and the floating harbour, revealed extensive layers of peat and organic muds which developed at the margins of the estuary. At Deanery Road, and at the Harbour-side development, these peat layers were dated using 14C, which showed that peat began forming in the Early Neolithic period and into the Bronze Age. Analysis of microscopic charcoal and pollen preserved in these layers showed evidence for ancient human activity including both burning on the marsh itself and clearance of the forests on the surrounding dry land, potentially for early farming.
Deposit modelling in central Bristol has shown that the thickest waterlogged layers, mostly associated with Medieval and later revetments and other waterside structures, occur in the Redcliffe and Temple areas of Bristol, in a meander of the Avon. The highest, and possibly latest, waterlogged deposits appear to occur in the Canon’s Marsh area.
ARCA’s geoarchaeological investigations in Bristol have provided both rare glimpses of prehistoric human activity and environmental conditions in the area, as well as producing detailed models which can be used to predict the likely distribution of deposits likely to have excellent archaeological preservation. These projects highlight the value of geoarchaeology to not only provide environmental context and archaeological data for the very earliest periods of Bristol’s history, but also have the potential to inform future archaeological investigations and development in the city.
Further reading: ARCA’s work in Bristol over the years has been incorporated into a number of publications including:
Cox et al (2006) The Archaeology and History of the Former Bryan Brothers’ Garage Site, Deanery Road, Bristol: the evolution of an urban landscape. Transactions of the Bristol & Gloucestershire Archaeological Society 124, 55-71.