The magnetometer survey was undertaken using four Bartington Grad601 sensors mounted at 1m intervals (1m traverse interval) onto a rigid carrying frame. The system was programmed to take readings at a frequency of 10Hz (allowing for a 10-15cm sample interval) on roaming traverses (swaths) 4m apart. These readings were stored on an external weatherproof laptop and later downloaded for processing and interpretation. The system was linked to a Trimble R12 Real Time Kinetic (RTK) differential Global Positioning System (dGPS) outputting in NMEA mode to ensure a high positional accuracy for each data point, in accordance with EAC guidelines (EAC 2016). The GPR survey was undertaken using a SIR (Subsurface Interface Radar) System-4000 manufactured by Geophysical Survey Systems Inc. The serial no. of the equipment used was system 1: SIR serial number 1814 and antenna 2584, and system 2: SIR serial number 1791 and antenna 2457. The layout of the geophysical survey is shown in Figure 3. The GPR survey was conducted by collecting data long a series of closely spaced parallel survey lines at 0.5m spacing across the whole area as access allowed. The location of each survey lines and measurement points was surveyed using a Leica SmartRover, providing accurate location data referenced to the Ordnance Survey OSGB36 National Grid system. The main findings of the surveys include a spread of magnetic disturbance at the centre of the Geophysical Survey Area (GSA) which corresponds to the outline of a linear earthwork recorded on historic mapping associated with an old marl pit. No evidence of the earthwork is visible on the ground today, though is recorded as a very faint linear feature in LiDAR data. There is little evidence of a definable feature in this location in any of the GPR depth slices suggesting the magnetic responses are either very shallow close to the ground surface or buried beyond the detection of the 400MHz GPR antenna. A further spread of magnetic disturbance and high amplitude responses at the western limit of the GSA are likely caused by a modern temporary track. Two former boundaries identified as very faint linear trends in the magnetometer data and a possible site of burning are the only other findings from the magnetometer survey. One of these former boundaries is identifiable as a faint high amplitude trend anomaly in the GPR data. The only other anomalies of note in the GPR data include two linear high amplitude trends of uncertain origin and two further amorphous spreads of high amplitude responses in the eastern half of the GSA in the 0.75m-1m depth slices possibly identifying areas of sediment compaction or changes in sub-surface horizons associated with possible former sites of extraction. Continuous high amplitude and hyperbolic features, predominantly aligned east-west and south-west/north-east, have been interpreted as resulting from agricultural cultivation and/or field drains. To conclude, no anomalies of possible or probable archaeological origin have been recorded by the surveys, including in proximity to a prehistoric burial mound (HER MST851) approximately 80m to the north of the survey area. Based solely on the results of the geophysical surveys the archaeological potential of the GSA is assessed as low.
Matt Berry (Sun,) studied this question.