| Abstract: |
The gradiometer survey follows the general guidance as outlined in: EAC Guidelines for the use of geophysics in Archaeology: Questions to Ask and Points to Consider (Europae Archaeologiae Consilium/European Archaeological Council 2016) and Standard and Guidance for Archaeological Geophysical Survey (CIfA 2014b). The survey was carried out using a twin-sensor fluxgate gradiometer (Bartington Grad601). These machines are sensitive to depths of up to 1.50m. The survey parameters were: sample intervals of 0.25m, traverse intervals of 1m, a zigzag traverse pattern, traverse orientation was circumstantial, grid squares of 30×30m. The gradiometer was adjusted (‘zeroed’) every 0.5-1ha. The survey grid
was tied into the Ordnance Survey National Grid- and set out using a Leica CS15 GNSS Rover GPS. The data was downloaded onto Grad601 Version 3.16 and processed using TerraSurveyor Version 3.0.36.0. The primary data plots and analytical tools used in this analysis were Shade and Metadata. The details of the data processing are as follows:
Processes: Clip +/- 1SD; removes extreme data point values. DeStripe all traverses, median; used to equalise underlying differences between grids (potentially caused by instrument drift or orientation, directional effects inherent in magnetic instrument, or differences in instrument set up during survey e.g. using two gradiometers). DeStagger selected grids, all traverses out- and inbound by 0.25m to 0.50m reduces staggering effects within data derived from zig-zag collection method. The survey identified 37 groups of anomalies across the seven fields. These were predominantly linear ditch and/or bank boundary features associated with phases of the existing and historic fieldsystem, drainage features, and possible pits and/or tree-throws; anomalies associated with agricultural activity, metallic debris and ground disturbance were also apparent. The degree of preservation of the identified features appears to be mixed, with some moderate to strong and others appearing poor. The majority of the anomaly responses are moderate to strong, indicating possible ceramic drainage features; whilst others are intermittent and barely discernible from the background geology. This suggests that these features only survive to a shallow depth, their intermittent nature suggesting only partial survival. However, it is possible that additional, even more ephemeral features, are masked by the background geology and modern disturbances. The results of the geophysical survey would suggest that the archaeological potential for much of the site is low. The majority of the identified features relate to historic phases of field-system which are tentatively suggested as being medieval and post-medieval in date, with multiple episodes of land drainage features; though the presence of possible prehistoric activity in the surrounding area means that a prehistoric or Romano-British date cannot be ruled out. Any development of the site is likely to encounter and destroy the buried archaeological resource (should it be present), further targeted evaluation trenching would validate and clarify the results of the geophysical survey, though may not produce any new evidence. |
