Bective excavations Blog


Results of Geophysical Survey 2010
September 15, 2010, 1:19 pm
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GEOPHYSICAL SURVEY SUMMARY SHEET: BECTIVE ABBEY, CO. MEATH

Summary of Results

The geophysical survey was extended from the work completed in 2009. Detailed resistance survey to the west of the abbey remains has identified numerous high resistance responses that may represent archaeological features. The probable wall to the west of the abbey appears to continue for a short distance where linear high resistance responses form a rectilinear pattern. It is possible that an entranceway with an associated structure was located here. North of this, are numerous high resistance responses. An archaeological pattern is unclear and it is possible that natural geological features are represented. However, it is equally possible that a spread of structural material, perhaps representing demolition debris has been identified. Survey to the east of the abbey boundary wall has identified several rectilinear series of high resistance responses and trends, suggestive of archaeological features. It is most likely that structural remains associated with the site of the choir have been identified. The results suggest the remains of the abbey extend beyond the current boundary wall of the ruins, into the adjacent pasture field.

Report Author Joanna Leigh Report Date 07/09/2010, J. M. Leigh Surveys, 11 Our Ladys Road, Maryland, Dublin 8, Tel: 01 521 0385, Mobile: 0879062729, www.jmlsurveys.com

1 Introduction

1.1 A geophysical survey has been conducted by J. M. Leigh Surveys at Bective Abbey, County Meath. The survey has been undertaken for the Office of Public Works and The Irish Archaeological Field School as part of a research and teaching exercise. Fieldwork consisted of a continuation of the resistance survey conducted in 2009 (licence 09-R-149). The survey results presented in this report are a culmination of the work conducted in 2009 and the current geophysical survey. The current survey was conducted under licence number 10-R-118, issued by the Department of the Environment, Heritage & Local Government.

2 Aims & Objectives

2.1 The current geophysical survey was undertaken to identify responses that may suggest unknown structural features associated with the abbey. Survey was extended from the 2009 survey work, and was positioned along the eastern and western sides of the boundary wall of the abbey ruins.

2.2 The location of the 2009 resistance survey and the current survey area are presented in Figure 1, at a scale of 1:625. The main objective of the survey was to expand upon the previous years work and further investigate the possibility of structural remains to the east and west of the current abbey ruins. By extending the 2009 survey grid, the survey results can be presented as a whole, allowing a more comprehensive interpretation of the results.

2.3 Limited extant remains of the abbey are present in the north of the ruins, and it is possible that further buried structural features are located outside of the current boundary wall. In particular, it is possible that the buried remains of structures representing the locations of the nave and choir are undetected. A total of 0.27 hectares of resistance survey was conducted to the east and west of the abbey ruins to investigate.

3 Survey Methodology

3.1 Survey work was undertaken on a uniform 20m x 20m grid. The site grid from the 2009 survey was resurrected and extended using a total station instrument. The tie in information is available upon request.

3.2 Data was downloaded and then processed with Geoplot v.3 software. All data processing was kept to a minimum, and adheres to the instrument manufacturer’s guidelines.

Results of Detailed Resistance Survey (Figure 6)

Western survey area (2009 & 2010 survey)

5.1 The survey areas were expanded to the north of the 2009 survey (Figure 1). The results present numerous high resistance responses that may be of archaeological interest. The 2009 survey data is also presented and the results are discussed as a whole.

Fig. 1

5.2 A high resistance linear response (1) is evident in the data set and is orientated north-east to south-west. The response most likely represents the buried remains of a wall, and may continue to the south outside the survey area. The probable wall remains appear to stop and form a ‘T’ shape in the north (2). This suggests a possible entranceway or opening.

5.3 High resistance responses (3) to the north appear to form a rectilinear pattern with (2) and may represent structural remains. It is speculated that an entranceway, with some structural element, is represented here.

5.4 Multiple isolated high resistance responses (4) are evident, and particularly prominent to the north of (3). The archaeological potential of these responses is unclear. Although it is possible that structural remains are evident, it is equally possible that natural variations are represented. Nevertheless, an archaeological interpretation of the responses to the north of (3) may represent a spread of material and may represent the remains of a demolished structure. This is speculative.

5.5 A broad low resistance response (5) is evident and may be of interest. The response could represent a broad enclosing feature. High resistance responses (6) are located to the immediate east of (5) and are immediately adjacent to the current boundary wall. It is possible that structural remains extend beyond the current boundary wall and are located here. The low resistance response (5) may represent a broad ditch type feature. The responses are of potential archaeological interest.

5.6 A broad low resistance response (7) is surrounded by high resistance responses (4). It is possible that an archaeological feature is represented here; however, it is equally possible that natural variations resulting from shallow geological formations have been identified. An archaeological interpretation is cautious.

5.7 A series of rectilinear high resistance responses (8) are of clear archaeological potential. The remains of the Choir are believed to extend outside the current boundary wall, and it is speculated that some of the responses identified represent this. Several linear trends to the north of (8) have also been identified and may represent more deeply buried structural remains. These responses are considered to be of clear archaeological potential.

5.8 A rectilinear high resistance response (9) to the immediate south of (8) is also considered to be of archaeological potential and suggests further structural remains. The response appears to be in alignment with (8) and is most likely associated.

5.9 A linear trend and high resistance responses (10) appear to extend from (9), to the east. Although they are of archaeological potential, they correlate with the location of a former field division marked on the early ordnance survey mapping.

5.10 To the south of (10) another rectilinear high resistance response (11) appears immediately adjacent to the current abbey boundary wall. It must be noted that a tree is located immediately adjacent and may produce high resistance reading during dry spells of weather. However, an archaeological interpretation must be considered. The response appears to be rectilinear in form and may represent further structural remains, perhaps extending from the south range of the abbey. This is speculative but must be considered.

5.11 Linear trends to the north east of (11) may also be of interest. They are parallel and perpendicular to the probable field boundary responses (10) and may represent further field divisions relating to activities within the abbey.

5.12 There are a cluster of responses (12) in the south of the eastern survey area and correlate with a topographical bank located in this area. The archaeological potential of these responses is unclear, however an archaeological interpretation must be considered. The natural topography slopes down to meet the River Boyne, to the east, and the responses may represent drainage features associated with the abbey.

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

6 Conclusion & Discussion

6.1 The geophysical survey has identified several responses of clear archaeological potential surrounding the extant abbey remains. The results suggest structural features extending beyond the current boundary wall of Bective abbey.

6.2 An interpretation of the results from the current survey, and the survey conducted in 2009 (Leigh 2009) suggest the probable extent of the southern range, extending c.6m south of the extant ruins. Further high resistance responses to the south of this, immediately adjacent to the current boundary wall, may represent further structural remains. However, it is possible that natural shallow geological features are represented here.

6.3 A series of rectilinear trends which correlate with the previous gradiometer survey (Leigh2009) suggest a ditched rectilinear enclosure to the south of the abbey. It is speculated that a garden or agricultural area was located here

6.4 To the east of the current abbey boundary wall several rectilinear high resistance responses are evident in the data. The responses are indicative of structural remains, and it is speculated that the site of the choir has been identified, in addition to further structural features of the abbey.

6.5 To the immediate west of the current boundary wall, further high resistance responses have been identified, suggesting further structural remains. A low resistance response to the immediate west of this may represent a broad ditched feature, although this is speculative.

6.6 A linear response in the west of the data most likely represents the remains of a wall. It appears to terminate, forming a ‘T’ shape, and several other responses form a rectilinear pattern here. It is speculated that an entrance way with some structural form is represented here. To the north of this are several high resistance responses but no clear archaeological pattern is evident. Although it is possible that a spread of material from a demolished structure is represented here, it is equally possible that the responses originate from shallow natural geological features.

7 Recommendations for further work

7.1 The resistance survey has identified clear areas of archaeological potential warranting further investigation. The resistance survey presented here was conducted with a probe separation of 0.5m. It is possible that further structural features remain undetected if they lie at a depth below 0.5m. Further resistance survey with a broader probe separation of 1.0m may prove beneficial in identifying more deeply buried structural remains.

7.2 Further geophysical survey is recommended to investigate the possible remains at Bective Abbey. In addition to further resistance survey, detailed gradiometer survey would allow detection of ditch features and any burnt or fired features.

7.3 Excavation trenches targeting some of the geophysical responses would prove beneficial in identifying their true nature and origin. This would facilitate a clear interpretation of the results of this and future surveys conducted at Bective Abbey.

7.1 A linear response (13) is located to the south of the abbey ruins and is suggestive of walled or structural remains. It correlates with the speculated extent of the south range of the abbey. The response is interpreted as representing the structural remains of this part of the abbey.

7.2 To the south of this, on the southern side of the current boundary wall, are a series of high resistance responses (14) at the edge of the survey grid. The responses appear fragmented but are of archaeological potential, and run parallel with (13). It is possible that further structural remains are represented here. This is speculative as the extent of the responses is ill-defined, and natural shallow geological features may be represented here. The archaeological potential of these responses is unclear.

7.3 A curving high resistance trend (15) and associated responses most likely represents a track way leading to the abbey. This may be more recent in origin, and it is the current access route to the abbey.

7.4 High resistance response (16) was interpreted as of possible structural origin (Leigh 2009). A test trench was positioned here and the origin of the responses was identified as natural shallow geology. A similar high resistance response (17) to the south of (16) is most likely natural in origin.

7.5 A linear high resistance response (18) with linear positive and negative trends was identified as a ditched feature in the excavation trench. A gradiometer survey was also conducted in this area (Leigh 2009) and identified positive responses suggesting a rectilinear ditched feature. It is likely that a small ditched enclosure, possibly enclosing a garden, is represented here.

Bibliography

English Heritage (2008) ‘Geophysical guidelines: Geophysical Survey in Archaeological Field Evaluation.’ Second Edition.

Gaffney, C & Gater, J (2003). ‘Revealing the buried past: Geophysics for Archaeologists.’ Tempus Publishing Limited.

Gaffney, C. Gater, J. & Ovenden, S. (2006) ‘The use of Geophysical Techniques in Archaeological Evaluations.’ IFA Paper No. 6’

National Soil Survey of Ireland (1980) General soil map second edition (1:575,000). An Foras Taluntais

Leigh, J. M. (2009) ‘Geophysical Survey Report: Bective Abbey, Co. Meath’ unpublished survey report J. M. Leigh Surveys.

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