THE BULL RING, DOVE HOLES, Derbyshire.

Report on geophysical survey, September 2000.


 

Introduction

A geophysical survey of approximately 0.35 ha was conducted over the henge site known as The Bull Ring, Dove Holes, Derbyshire (National Monument Number: 23282) at the request of the regional Inspector of Ancient Monuments. Previous work at the site includes a period of trial excavation in 1949 by the Oxford University Archaeological Society (Alcock 1950). This helped identify the site as of the "double-entrance" class of Henge Monument and revealed the form of the ditch and bank, but failed to provide any evidence for stone settings (ibid).

The aim of the survey was to help gain a greater understanding of the monument and the activity that had occurred within it; to inform the future management of the site, particularly in relation to its repair and maintenance; and to attempt to reveal any trace of a former stone circle.

The Bull Ring (SK 078 782) lies on well drained silty soils of the Malham 2 association (Soil Survey of England and Wales 1983) developed over Carboniferous Limestone (Institute of Geological Sciences 1977). At the time of the survey the field was under grass and used as a recreation area.

 

Method

Magnetometer survey

High-resolution magnetometry was chosen as the first survey technique to utilise so as to carry out a detailed reconnaissance of the ditch and internal platform. The survey was conducted over all the numbered grid squares (Figure 1) using the standard method outlined in note 2 of Annex 1, but with a traverse interval of 0.5m. Plots of the data-set are presented as both an X-Y traceplot and a linear greyscale, at a scale of 1:500 on Plan A. The only corrections made to the measured values displayed in the plots were to zero-mean each instrument traverse to remove heading errors and to "despike" the data through the application of a 2m by 2m thresholding median filter (Scollar et al 1990) to reduce the detrimental effects produced by surface iron objects. In addition the lower and upper values have been trimmed for presentation as a traceplot.

Earth resistance survey

A resistivity survey was conducted over all the numbered grid-squares (Figure 1). However, due to the lack of time available and the information known from the previous excavation work across the bank and ditch, it was decided to concentrate efforts on the central area to try to locate any stone settings or pits. Measurements were collected with a Geoscan RM15 resistance meter, PA1 mobile probe array in the Twin-Electrode configuration. Readings were collected using the standard method outlined in note 1 of Annex 1, but with a sample interval of 0.5m x 0.5m. Plots of the data-set are presented as both an X-Y traceplot and a linear greyscale, at a scale of 1:500 in Plan B.

 

Results

Magnetometer survey

A graphical summary of the anomalies discussed in the following text is provided on Plan C1.

The magnetic response has been severely affected by modern disturbance most probably ferrous rubbish deposited in the henge ditch, such as at [1] [4]. By far the largest area of disturbance can be seen at [5]. This correlates with the position of the quarry in the north-eastern section of the ditch. Directly south of this is an area of raised magnetic readings [6], probably also related to ferrous litter, but not producing such a severe response.

There are at least four other small areas of magnetic disturbance [7], all located on the central henge area.

There are few, if any, anomalies that are not necessarily due to modern disturbance. The strongest of these, [8], gives a positive reading of ~25nT. The others at [9] [12] are more subdued at around 10nT. Due to their small size and the amount of surrounding ferrous disturbance, these anomalies are also likely to be relatively recent in origin although a tentative prehistoric origin cannot be ruled out.

Earth resistance survey

A graphical summary of the anomalies discussed in the following text is provided on Plan C2.

The resistivity survey is dominated by the high resistance responses [R1] [R4] correlating with the inner edge of the ditch where this abuts the central area. This corresponds with the excavation evidence that suggests that the inner side of the ditch was cut sharply into the limestone (Alcock, 1950; 83).

The area of reduced resistance at [R5], between [R1] and [R2], may be a reflection of where the "natural rock had been sharply cut to form a ditch and causeway" (Alcock, 1950; 85). In addition lower resistance readings [R6] interrupting the course of [R1] could well be attributed to the 1949 excavation trench number 4 (ibid 82).

Where the survey was extended to include the bank, it is possible to see additional high resistance responses [R7] reflecting the rubble construction of this feature.

The area of slightly raised resistance at [R8] is around the location of a tree and could be an effect of the root system on the water content of the soil here. The isolated high resistance anomaly at [R9] is hard to interpret due to its discrete nature, but could possibly relate to the location of a buried stone. A similar interpretation of the anomaly [R10] would be even more speculative.

 

Conclusion

The magnetic survey has unfortunately been severely affected by modern disturbance, possibly through the use of the ditch as a dumping area. There has been no discernible response to the known construction of the henge i.e. the bank and ditch, so it seems unlikely that any slighter features such as stone settings or pits would have been recorded if present.

The resistance survey has detected a difference in response between the bank, ditch and inner area. However, few other features have been detected, and the central area has generally produced low readings - with the exception of anomalies R8, R9 and R10 which could, speculatively, correspond with stones.

Overall, the survey results have been disappointing as little extra information about The Bull Ring henge has been recorded. It has not been possible to identify any specific internal features, but this does not necessarily preclude their presence. As has been shown, the geophysical response to the known earthwork features has been poor in general, and therefore the possibility of recording smaller features is limited.

 

References

Alcock, L. 1950, The Henge Monument of The Bull Ring, Dove Holes, Derbyshire. Proceedings of the Prehistoric Society, 16, 81-86.

British Geological Survey, 1977, Chapel en le Frith, England and Wales, Sheet 99, Drift Geology, 1:50,000.

Scollar, I. Tabbagh, A. Hesse, A. and Herzog, I. (eds.), 1990, Archaeological Prospecting and Remote Sensing. Cambridge.

Soil Survey of England and Wales, 1983, Soils of England and Wales, Sheet 3, Midland and Western England.

 

List of enclosed figures.

Figure 1 Location plan of survey grid squares over base OS map (1:2500).

Plan A Traceplot and linear greyscale of magnetometer data (1:500).

Plan B Traceplot and linear greyscale of resistivity data (1:500).

Plan C Graphical summary of significant geophysical anomalies (1:500).

 


Surveyed by: P Cottrell, A Payne, L Martin
Date of survey: 18-22/9/2000
Reported by: L Martin
Date of report: 7/11/2000
Centre for Archaeology report number: 14/2001