Geophysics at Castle Cary The Castle Site Authors John Oswin Bath and Camerton Archaeological Society and Matthew Charlton June 2011 Geophysics at Castle Cary The Castle Site © Bath and Camerton Archaeological Society April 2011 Abstract A geophysical survey was undertaken by the Bath and Camerton Archaeological Society during March and April 2011, which encompassed the castle site at Castle Cary, Somerset. This report concentrates on the castle site. Others will describe work at Manor Farm and Dimmer. The site was surveyed using fluxgate gradiometry and twin-probe resistance. Resistivity profiling and ground-penetrating radar also augmented the survey. The inner and outer baileys were surveyed on separate grids, but these could be related to each other to a good approximation. Areas of Manor Farm which came within the scheduled area, were also on separate grids. Twin-probe resistance was the more successful method, and this revealed massive masonry structures within the inner bailey. The outer bailey appeared to contain a rectangular structure contained within a curtain wall which did not correspond to the standing earthen ramparts. i Acknowledgements Sincere thanks go to Mr John Churchouse of Manor Farm for all his support and in providing permission and access to his land. Special thanks go to Somerset County Archaeologist Bob Croft and Rob Iles of English Heritage for their continued support as well as the granting of a Section 42 license to undertake the geophysical survey. Thanks also go to the Bath and Camerton Archaeological Society volunteers led by Dr John Oswin and Owen Dicker, as well as those members of the Castle Cary Museum and the local community who took part in the survey over the three day period. Graphics were kindly produced by Keith Turner and Google Earth. This project was made possible by funding from the Heritage Lottery Fund. ii Table of Contents Abstract 1. Introduction 1 2. Equipment used 4 3. Survey results 8 4. Discussion 16 Appendix A 19 Bibliography 21 Additional observation by Mark Corney iii List of Figures 1.1 Showing the location of the town centred at ST640322 1.2 Showing the scheduled area 2.1 Bartington 601-2 twin fluxgate gradiometer 2.2 Twin-probe resistance meter 2.3 The TR/CIA resistance meter 2.4 Ground-penetrating radar 3.1 Magnetometer results - survey of the inner and outer bailey 3.2 Resitivity Results- survey of the inner and outer bailey 3.3 Resitivity Results Manor Farm 3.4 Placing of these profiles with respect to the resistance grids and features. 3.5 Profile 1 3.6 Profiled 2 and 3 3.7 Profile 45 3.8 Profile 67 3.9. Start of grid - GPR 3.10 End of grid - GPR 3.11 Between Manor Farm (left) and inner bailey (right) 4.1 Resistance plots and radar strip laid out. 4.2 Showing the plan marked up. Appendix A Grid and survey data A.1 Grid data for the castle site magnetometer survey A.2 Grid data for the manor farm magnetometer survey A.3 Castle site twin-probe resistance grid A.4 Shows the Manor Farm site twin-probe resistance grid iv 1 Introductory 1.1 Location and topography Location Castle Cary is a small town in south-east Somerset, lying within the Jurassic belt of geology, approximately at the junction of the upper lias and the inferior and upper oolites. Building stone is plentiful, and is orange to yellow in colour. This is the source of the River Cary, which now runs to the Bristol Channel via King’s Sedgemoor Drain and the River Parrett, but prior to 1793 petered out within Sedgemoor. The town is centred at ST640322. A location map is shown in figure 1.1. Figure 1.1 showing the location of the town centred at ST640322 Topography The site occupies a natural spur formed by two conjoining irregularly shaped mounds extending from the north east to the south west. The ground gradually rises to the north and, more steeply, to the east, and falls away to the south. The outer bailey is situated on the larger mound which is located on the north side of the inner bailey. The outer bailey is defined on the north side by a low broad bank with a shallow external ditch. The east side is enclosed by a central ditch flanked on both sides by 1 parallel banks between 2.5m and 7m high above the base of the ditch, with an overall width of approximately 42m. The banks form a curve at the south east corner of the outer bailey at its junction with the north east corner of the inner bailey. The east side of the inner bailey is enclosed by a ditch with an inner bank approximately 12m wide and an outer bank approximately 5m wide. The south side of the inner bailey drops steeply down to Park Pond, a wide marshy area which is fed by springs and is the source of the River Cary. Modern development now defines the western side of the castle site and an evaluation in 1998, prior to its construction, revealed a continuous ditch of between 10m and 12m wide, which enclosed the inner and outer baileys. 1.2 Background The site is a Medieval Motte and Bailey castle occupying a natural spur overlooking the source of the River Cary. It has been suggest that the first phase of the castle was an earlier ringwork which was built not long after the Norman Conquest (Leach & Ellis 2010). The positioning of the castle may also have tied into an existing Romano- British or Saxon site, as a common location for the building of these castles was to utilise earlier phases of defence (Creighton and Higham 2003). Excavations by Leach and Ellis on Manor farm between 1999-2001 discovered a primary phase of Roman-British activity and the discovery of a lime-burning kiln, 150 sherds of Romano-British pottery, as well as a finely modelled bronze figurine of a lar which may have come from a nearby villa site (Leach 2010). It was thought that after the second siege in 1153, the castle was demolished as a result of the destruction on baronial strongholds following the uprising, and some of the stone used in the construction of the new manorial centre immediately to the west, overlaying the former castle ditch. The new practicable position of the manorial site may also have been more accessible and easily integrated with the new urban development (Prior 2004). The foundations of the Norman keep were excavated in the 1890’s, and it was suggested that the lower mound had been built up after the construction of the Keep in the late 11th or early 12th century, and remained in use until around 1153. The castle was besieged by King Stephen in 1138, and again in 1153. The earliest visible remains at Castle Cary are those of the Castle and its constituent earthworks (SMR 53640), sited to the east of the town. Excavations in the area of Manor Farm (SMR 11632, 11639, 11640) located further baileys of the castle suggesting that the inner and outer baileys were of one phase. A section of the ditches showed evidence of what appeared to have been deliberate backfilling, possibly as early as the 12th century. One of these ditches was later re-dug to provide one side of a moat around the later Manor House (SMR 11641). It was thought that after the 2 second siege in 1153, the castle was possibly demolished as a result of the destruction of baronial strongholds following the uprising, and some of the stone was used in the construction of the new manorial centre immediately to the west, overlaying the former castle ditch. In March 2011 a license was obtained from English Heritage to undertake a geophysical survey on the scheduled monument (no. 33722) at Castle Cary in South Somerset (see figure 1.2). The survey was carried out under licence from English Heritage (case no. SL00001078) and with permission from the local landowner, Mr John Churchouse. The survey was carried out on behalf of Castle Cary museum by the Bath & Camerton Archaeological Society under the nominated representatives Dr John Oswin and Matthew Charlton and took place over a three day period with participation from Castle Cary museum, as well as members of the local community. The geophysical survey formed part of a wider project concerned with improving interpretation of historic sites in and around Castle Cary. 1.3 Dates of Survey The survey was conducted in two sessions. The first was three days, Monday to Wednesday 28th to 30th March 2011. The second session was on Monday and Tuesday, 11th and 12th of April. 1.4 Personnel The project was organised by Matthew Charlton of Enthuseit Ltd on behalf of Castle Cary Museum. The Geophysical survey was undertaken by BACAS volunteers led by John Oswin and Owen Dicker. Assistance was given by members of the Castle Cary Museum including, Anne Brittain (Chairperson), Annette Bedford (Secretary), Anne Webster (Treasurer) and Paul Clothier (Collections). Members of the local community also contributed towards the survey. Graphics were kindly produced by BACAS member Keith Turner. 1.5 Scope of this report This report concentrates on survey work within the scheduled area of the castle site. Details from the survey at Manor Farm within the scheduled area will be included, 3 and any information from the unscheduled area will be mentioned if it is relevant to understanding the site. The education activities planned within the survey will not be included in this document. This document will not report on work at Manor Farm beyond the scheduled area or on work at Dimmer.