Coring Exercise at Christchurch Castle

Christchurch Castle is part of a Scheduled Ancient Monument in the guardianship of English Heritage. It is a Norman motte and bailey castle, originally owned by the powerful de Redvers family. The Castle was reactivated in the time of the English Civil War by Parliamentarian forces who recut the Castle ditches and demolished houses in the town to provide a clear field of fire for artillery. With the permission of English Heritage, THE CHRISTCHURCH ANTIQUARIANS have since 2003 been carrying out a geophysical and historical survey of the Castle site, in order to understand more of its origins and development. In particular we wish to confirm the presence and the course of the medieval ditches which are mentioned in historical sources. These ditches are now infilled and buried under modern topsoil. Interpretation of the geophysical data has led us to identify the possible route of the ditch but this can only be confirmed by more intrusive archaeological techniques such as excavation and/or coring. With the permission of English Heritage, on 15 September 2005, we conducted a limited coring exercise in the area around the base of the motte which we believe to be the site of a section of the ditch. The coring was carried out for us by Dr Martin Bates,lecturer in Environmental Archaeology, Lampeter College, University of Wales. Coring involves driving a hollow drill bit into the ground to a maximum depth of some 3 metres, depending on the level of the water table. The drill bit, 50mm in diameter, is withdrawn in sections and the soil sample which it contains is recovered and taken away for later analysis. Alternatively, 0.5m sections can be brought to the surface and examined on site, or bagged up for later analysis. Three such cores were drilled so that a profile across the width of the ditch can be estimated. After we finished the coring work the small holes left by the extracted cores were filled with gravel and the turf reinstated. By analysing the soil in each core according to its depth, we can construct a profile of the under-surface soil layers. Changes in colour and texture will provide clues to the historical surface profile of the ground and hopefully provide proof of the presence of the infilled ditch. Further expert analysis could also be carried out on such samples to detect, for example, pollen grains and the presence of small snails, both of which could give clues to the conditions prevailing during the period when the surface was exposed.