G E O P H Y S I C S I N A R C H A E O L O G Y REPORT Boekweitakker 28 3773 BX Barneveld The Netherlands Tel: 0342 422338 Internet: www.dwconsulting.nl Geophysical Survey Report Preliminary Draft For Customer Approval Author(s): D. Wilbourn () Report Ref Nbr: 2003/04 Client: AWN Zeeland Client Ref Nbr: AWN-2003-2 Report Date: 11-03-2003 Copyright 2003 All rights reserved 14-04-2003
Table of Contents SUMMARY OF RESULTS:...1 INTRODUCTION:...1 Site location...1 Site description/history...1 Survey objectives...1 Survey methods used...1 METHODS:...2 Fieldwork...2 Grid location...2 Section A...2 Section B...2 Section C...2 Section D...2 Geophysical instruments used...2 Method(s) of data presentation...2 RESULTS:...2 Description...2 Section A...3 Section B, C & D...3 Interpretation...3 Section A...3 Section B, C & D...3 CONCLUSIONS:...3 STATEMENT OF INDEMNITY...3 APPENDICES:...4 Plans/Plots...4 General plan of Resistivity survey results...5 General plan of Magnetometer survey results...6 Section A Resistivity. Greyscale plot of processed data...7 Section A Magnetometry. Greyscale plot of processed data...8 Section B Resistivity. Greyscale plot of processed data...9 Section B Magnetometry. Greyscale plot of processed data...10 Section C Resistivity. Greyscale plot of processed data...11 Section C Magnetometry. Greyscale plot of processed data...12 Section D Resistivity. Greyscale plot of processed data...13 Section D Magnetometry. Greyscale plot of processed data...14 List of Figures FIGURE 1...5 FIGURE 2...6 FIGURE 3...7 FIGURE 4...8 FIGURE 5...9 FIGURE 6...10 FIGURE 7...11 FIGURE 8...12 FIGURE 9...13 FIGURE 10...14
Summary of Results: At the request of the AWN Zeeland, A range of surveys, both Magnetometer and Resistivity, were carried out within the moated farm Dunno near Oostkapelle. Archival evidence indicates that the site has been occupied since the 13 th century and was far more substantial and important than the current, simple farm complex.. Archival evidence indicated the presence of a castle of some form. The purpose of the surveys was to try to determine the size and extent of former buildings within the moated area. Resistivity results seem to have produced the best results. They confirm the presence of foundations in one corner of the site and the position of what could possibly be the original edge of the island prior to it s expansion into a rectangular shape. Introduction: Thanks to the enthusiasm of the current land owner, Mr. Lantsheer, the AWN Zeeland group have been investigating the farm known as Dunno near Oostkapelle for some time. Though the current buildings, consisting of a small farmhouse and a single large barn are not particularly special, it is obvious from the large rectangular moat surrounding the farm complex and the imposing drive, gate and bridge leading to the farm that the site once was much more important than it now is. Archival data shows that it has been in existence since at least the mid 13 th century and was an important outpost of the Abbey of Middleburg, being substantial enough to receive Counts as guests. References throughout the middle-ages indicate the continuing importance of the site. In the mid 18 th century, the Hattinga map shows the site to be in much the same form as is now seen. However there is a third structure indicated on this map in the northeast corner of the moated area. It was this building that was the primary focus of the surveys but all suitable open areas of the farm were examined. Site location The farm is located just north of Oostkapelle, Gemeente Veere, Zeeland at approx. Grid 0281, 4001. Topographic map 65AN. Site description/history The area within the moat is roughly rectangular, about 150m wide at the front (north) and stretching back 110m on the eastern side and 80m on the west. The farm is reached by means of a bridge at the middle of the north side. The farmhouse is to the west of the bridge and the barn centred on the island directly opposite the bridge. Much of the ground surrounding the farm buildings is in use for storage of hay or farm implements. The area to the rear of the farmhouse all the way to the western side of the moat is covered in a range of small sheds. The area behind the barn has also been extended in the recent past with cow sheds and some horse stables. Some of the remaining land is also an orchard. It is know that the farm has been in use in more-or-less it s current configuration since at least 1750. Survey objectives The primary objective of the survey was to determine if any traces of the suspected castle and it s associated structures could be found. Secondarily, it was hoped that other aspects of the site s history could be explained, such as the possible shape of the island prior to it being squared off. Survey methods used Because of the patchwork nature of the site, each small section that could be surveyed has been given a code letter. This letter is used throughout this report and the collected data. More than one survey method was used in each section when possible. Thanks to the manpower available from the AWN group, it was possible to use Resistivity for all of the sections close to the buildings and even larger fields when adjacent results indicated that it was worthwhile. Magnetometer surveys were carried out on all the larger sections, and even some of those close to buildings. The latter provided useful experience and reference data to enable the 2 sets of results (Magnetometer and Resistivity) to be compared.
Methods: Fieldwork The survey was carried out during 2 weekends in March, 2003. The weather was generally cool (±5 ), dry but overcast. The ground conditions varied depending on the section but were generally meadow and pasture fields with some mud. Grid location Because of the complexity and built-up nature of the site, each section had to be individually located. The sides and corners of the barn were found most suitable for this purpose. Section A This section was located in the SE corner of the island at the point indicated as being the location of the third, unidentified building in the Hattinga map. It is basically the area within a small field used for exercising ponies. The base point was placed on a line extended from the eastern side of the barn 8m from it s corner. The baseline was set up on this point, at right-angles to the end wall of the barn. Section B This section was located to the NW of the barn. As with Section A, the baseline was established relative to the corner of the barn. The base point was placed on a line extended 11,7m from the western corner of the barn inline with the end wall of the barn. The baseline was set up from this point and at right-angles to the end wall of the barn. Section C Continuing on round from Section A, Section C covered most of the field to the rear of the barn. It s baseline is related to that of Section A, using the same NW SE origin, but leaves an 8m gap in the NE SW axis (i.e. the grid is the same across the length of the barn but starts 48m back from the Section A baseline) Section D Continues the grid established for Section B to the NW into the adjacent field. Geophysical instruments used A Bartington Grad 601-1 was used for the Magnetometer portions of the surveys. Grid size was 20m x 20m with a 1m traverse interval and 0.25m sample interval. Sensitivity was set to 0.1nT. The data was downloaded using Bartington software and processed in GeoPlot 3.0. A TR/CIA Resistivity meter was used for the Resistivity portions of the surveys. Grid size was 20m x 20m with a 1m traverse interval and 1m sample interval. Automatic logging was used. The data was downloaded and combined into composite datafiles using TR/CIA software. Further processing was done in GeoPlot 3.0. Method(s) of data presentation The data is presented in the Plans/Plots section of this report. An overview of the site with the sections marked is presented as Figure 1. Each section is then shown individually with location data, survey results for each survey method and any features seen in the data. Finally a plot of just the data for each section is shown. Results: Description Although nearly a hectare was surveyed using both Resistivity and Magnetometry, the results remain fragmented. The magnetometer in particular had difficulty in detecting features beneath the high level of background noise inevitable in close proximity to a working farm that has been occupied for perhaps 1000 years. Good results were obtained from the resistivity meter although it is difficult to determine exactly how the features seen in each area should be joined together.
Section A The main features visible in section A are the 2 linear high resistance areas running parallel to the waters edge and heading towards the corner. There is also a high resistance feature close to the corner of the barn. The magnetometer results for this area do not reveal anything significant though there is a slight correlation between the linear high resistance features and some magnetometer noise. Section B, C & D Sections B, C & D all show parts of similar features so will be described together. The main theme of these sections is an apparent long curving linear feature running behind the barn and curving up towards the corner of the current island behind the house. This feature is seen in both the resistivity data as a high resistance area and to an extent in the magnetometer data. Overall, the magnetometer data would not be considered definitive on it s own, but does contain features that correlate well with the resistivity data. Section D s magnetometer data shows a very strong signal close to the stables and along the small ditch. Also it s resistivity data also shows a number of clear, low resistance linear features. Interpretation Section A As mentioned above, Section A covers most of the area indicated in the archival data as being the site of another building. It is clear from the resistivity results that 2 sides of some form of foundation structure can be seen in the corner of the area. It is also possible that the high resistance feature close to the corner of the barn forms part of a third side to the structure. However this is very speculative as that area is also the entrance to the field and the signal so could be the result of more modern disturbance. Section B, C & D The resistance surveys of the three areas are dominated by the strong high resistance feature (Fig 1, purple line). Though there is no definite evidence for it, it is believed that this feature could be the remains of the original ditch around the island, prior to it being squared off perhaps in the 18 th century. Normally a naturally filled-in ditch would be expected to have a low resistance, However the high resistance could be the result of the ditch being filled deliberately, using rubble and other materials. This hypothesis is supported by the magnetometer results for the same area which show noisy readings, usually indicative of building rubble. Section D also contains another high resistance feature (Fig 1, dark blue line) which is unexplained and a number of low resistance features (Fig 1, light blue lines) that correlate with sunken troughs visible on the surface, probably indicating that these are relatively recently filled ditches. The strong positive readings on the magnetometer near the stables are almost certainly caused by adjacent fences and buildings. The noisy streak beside the small ditch could well be the result of cleaning the ditch out. Section C has a large high resistance area that seems to split off from the main linear feature. This is also unexplained but does correlate with the entrance to the field. This may therefore be caused by land use rather than archaeology. Conclusions: In general it can be concluded that two significant features have been located: the foundations of the third building shown on early maps and the possible boundary of the original island. Statement of indemnity is not responsible for any costs or damages incurred by the customer resulting from actions taken on the basis of the data and/or conclusions contained in this report.
Appendices: Plans/Plots Figure Coverage Processing 1 General plan of Resistivity survey Base layer (cadastrale map), Survey layer & annotation layer. results 2 General plan of Magnetometer survey Base layer (cadastrale map), Survey layer & annotation layer. results 3 Section A Resistivity Greyscale plot of processed data: Composite created in TR/CIA Resistivity app, Interpolated in both X & Y axes in Geoplot to double resolution 4 Section A Magnetometer Greyscale plot of processed data: Clip at 100 & 100 nt Absolute (I +/- 3SD), Zero Mean Traverse, Despike at default settings. Re-clip at 20 & 20 nt 5 Section B Resistivity Greyscale plot of processed data: Composite created in TR/CIA Resistivity app, Interpolated in both X & Y axes in Geoplot to double resolution Rotate 180º 6 Section B Magnetometer Greyscale plot of processed data: Clip at 300 & 300 nt Absolute (I +/- 3SD), Zero Mean Traverse, Despike at default settings. Re-clip at 36 & 36 nt Rotate 90º 7 Section C Resistivity Greyscale plot of processed data: Composite created in TR/CIA Resistivity app, Interpolated in both X & Y axes in Geoplot to double resolution 8 Section C Magnetometer Greyscale plot of processed data: Clip at 200 & 200 nt Absolute (I +/- 3SD), Zero Mean Traverse, Despike at default settings. Re-clip at 20 & 20 nt Rotate 270º 9 Section D Resistivity Greyscale plot of processed data: Composite created in TR/CIA Resistivity app, Interpolated in both X & Y axes in Geoplot to double resolution 10 Section D Magnetometer Greyscale plot of processed data: Clip at 300 & 300 nt Absolute (I +/- 3SD), Zero Mean Traverse, Despike at default settings. Re-clip at 12 & 12 nt All processing carried out using Geoplot 3.0 at default values unless otherwise stated.
General plan of Resistivity survey results Figure 1
Notes: Map oriented to survey to minimise distortion Blue: Survey grids Green arrowed lines: distances from barn Yellow dotted: possible position of third building Purple dotted: possible path of original island boundary Dark blue dotted: Unaccounted ditch Light blue dotted: Probable modern filled ditches Purple blocks: Rubble areas found during Bore survey. The values listed in the section detail tables (in Ohm - M) are arbitrary values and only relate to the grid squares within a section. They are entirely dependant in the conditions of the day of measurement and local ground conditions at the remote probes. The greyscale values of each section cannot therefore be related to those in other sections.
General plan of Magnetometer survey results Figure 2 Notes: Map oriented to survey to minimise distortion Blue: Survey grids Green arrowed lines: distances from barn Yellow dotted: possible position of third building Purple dotted: possible path of original island boundary Dark blue dotted: Unaccounted ditch Light blue dotted: Probable modern filled ditches Purple blocks: Rubble areas found during Bore survey. The values listed in the section detail tables (in nanoteslas - nt) are arbitrary values and only relate to the grid squares within a section. Each section has been processed to best enhance it s data without reference to other sections. The greyscale values of each section cannot therefore be related to those in other sections.
Section A Resistivity. Greyscale plot of processed data 21.03 20.13 19.23 18.32 17.42 16.52 15.62 14.72 13.82 12.91 12.01 11.11 10.21-3SD Mean 3SD Grid size: 20m x 20m Figure 3
Section A Magnetometry. Greyscale plot of processed data 26.23 nt 21.89 17.55 13.22 8.88 4.55 0.21-4.12 8.46 12.80 17.13 21.47 25.80 nt -3SD Mean 3SD Grid size: 20m x 20m Figure 4
Section B Resistivity. Greyscale plot of processed data 24.89 23.81 22.74 21.66 20.58 19.51 18.43 17.35 16.28 15.20 14.12 13.05 11.97-3SD Mean 3SD Grid size: 20m x 20m Figure 5
Section B Magnetometry. Greyscale plot of processed data 19.50 nt 16.34 13.18 10.02 6.86 3.70 0.54 2.62 5.78 8.94 12.10 15.26 18.42 nt -3SD Mean 3SD Grid size: 20m x 20m Figure 6
Section C Resistivity. Greyscale plot of processed data 23.42 22.45 21.49 20.53 19.56 18.60 17.63 16.67 15.71 14.74 13.78 12.82 11.85-3SD Mean 3SD Grid size: 20m x 20m Figure 7
Section C Magnetometry. Greyscale plot of processed data 14.19 nt 11.83 8.48 7.13 4.77 2.42 0.07 2.29 4.64 6.99 9.34 11.70 14.05 nt -3SD Mean 3SD Grid size: 20m x 20m Figure 8
Section D Resistivity. Greyscale plot of processed data 22.68 21.53 20.39 19.24 18.10 16.95 15.81 14.67 13.52 12.38 11.23 10.09 8.94-3SD Mean 3SD Grid size: 20m x 20m Figure 9
Section D Magnetometry. Greyscale plot of processed data 11.73 nt 9.80 7.86 5.97 3.98 2.05 0.11 1.83 3.77 5.70 7.64 9.58 11.51 nt -3SD Mean 3SD Grid size: 20m x 20m Figure 10