Historic Environment Assessment: the West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire NGR SU 1155 6812 ______
Prepared by: Ben Urmston
On behalf of: Mr N. Baldock
Document No: ACW912/1/2
Date: March 2017
AC archaeology Historic Environment Assessment: the West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire
Centred on NGR SU 1155 6812
Contents
Summary 1
1. Introduction 2
2. Assessment methodology 2
3. Archaeological investigations, historic maps and other information 3
4. Heritage assets within the broader area 6
5. Air photographs and LiDAR 9
6. Geophysical survey 10
7. Comments 11
8. References 12
APPENDIX 1: Geophysical Survey Report
APPENDIX 2: Setting Assessment Summary
This document has been prepared in support of a scheduled monument consent application relating to the Sarsen Kennels site, West Kennet. The document sets out a review of existing information for the existence of the course of the West Kennet Avenue, results from new geophysical surveys and an assessment of the current and enhanced setting of the site that may results from the SMC proposals.
There has been a long history of investigations into the archaeology of Avebury and its historic landscape, which began in the middle of the 17th century, when John Aubrey visited the area. One of the central questions has always been the relationship between the main Avebury henge complex and nearby sites like the Sanctuary, which is located approximately 2.4 km southeast of the henge site. The West Kennet Avenue is a double line of upstanding sarsen stones that is believed to link these two sites.
Although a significant amount of archaeological fieldwork has been undertaken along the northern part of the West Kennet Avenue in the vicinity of Avebury itself (e.g. Keiller in 1934-35), there has been no archaeological fieldwork in the areas closer to the Sanctuary, apart from excavations in 1930 in the area of the stone circle itself (Cunnington 1931).
We do know from the mid-18th century antiquarian writings and illustrations of William Stukeley that farmers were removing Avenue stones from near the Sanctuary, and the last ones appeared to have been removed in the 1720s, either to use as building material or to clear fields to improve agricultural efficiency. This has resulted in there being some uncertainty as to whether the Avenue linked directly with the Sanctuary and, if it did, the precise location of the route of the double line of stones. This is partly due to the removal of the stones and that the route of the Avenue may have been obscured by later activities, such as the construction of the A4 London Road, and buildings such as the Sarsen Kennels site itself. It is in fact possible that broken sarsen stones may have been used in the construction of the road and buildings within Sarsen Kennels. Two plans/ maps dating to 1812 (R. Colt- Hoare) and 1884 (A.C. Smith), however, show that a stone may have survived in the northwestern corner of the Sarsen Kennels site, together with four to the west of the site. However, by the time of the publication of the 1887 OS map, there is no stone marked within the site.
Considering how much work has been undertaken elsewhere in the Avebury landscape, it is surprising that no archaeological fieldwork has been carried out in the areas of Sarsen Kennels and the Sanctuary, to further our knowledge of the West Kennet Avenue. This current study therefore presents an opportunity to contribute to our understanding of this part of the Avenue. This initial stage of work compiles the available historic record, including early maps and other published sources, in order to assess the potential for locating evidence for the Avenue. The results of geophysical survey do not provide a confirmed alignment for the Avenue through the Sarsen Kennels site, but allows the promotion of a hypothetical route based on the best available evidence.
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 1 1. INTRODUCTION
1.1 This assessment has been prepared by AC archaeology Ltd, on behalf of Mr. N. Baldock and was carried out in June and July 2016, and updated in March 2017. The location of the site is shown on Fig. 1.
1.2 This report sets out the results of a desk-based assessment of the historic environment (archaeological and cultural heritage) issues relating to the proposed redevelopment of the Sarsen Kennels site near West Kennet, along with a review of aerial photography, LiDAR datasets and a geophysical survey.
1.3 The study has been prepared to support a Scheduled Monument Consent, as well as a future planning application to be submitted to Wiltshire Council, should the SMC be granted. The proposed development comprises the renovation and conversion of an existing building that may well be located to the south of where the Avenue stones would have been positioned. The removal of other structures on the site may also have the potential to enhance the setting of the line of the Avenue.
1.4 The aim of this report is primarily to assess all available evidence for the line of the West Kennet Avenue in the vicinity of the proposed application area, and secondly: to identify other known heritage assets within a defined study area, centred on the Sarsen Kennels site; to consider their significance; and, where possible at this level of assessment, to identify any potential impacts on those assets.
1.5 The application area occupies the site of the Sarsen Kennels located approximately 200m south east of the village of West Kennet. The site area forms a triangle of land south of the A4 and east of the road leading to East Kennet. These two roads form the western and northern boundaries of the site.
2. ASSESSMENT METHODOLOGY
2.1 The study consists of a desk-based assessment, as defined by the Chartered Institute for Archaeologists (CIfA) Standard and Guidance for Desk-Based Assessment (1994, revised 2014). Baseline data have been gathered from up to a 500m radius around the application area.
2.2 The scope of the study is based on gathering sufficient information to answer a specific question that relates to whether there is any clear evidence that the line of the West Kennet Avenue extends into the site area of Sarsen Kennels. The site is believed to be located within the projected line of the Avenue as it extends eastwards to link with the Sanctuary, which is located 300m southeast of Sarsen Kennels.
2.3 The information derived from the study has been used: • to identify and assess the significance of the currently recorded heritage assets in the study area; • to assess the potential for the discovery of additional heritage assets within the boundaries of the proposed application area; • to identify possible effects of the proposed development, whether adverse or positive, as far as is possible at this stage of assessment; and
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 2
• to recommend survey methods that may further confirm the presence of the Avenue within the study area.
2.4 The results of the assessment are discussed in Sections 3 to 7. The main heritage assets within 500m are summarised in Table 1 and shown on Fig. 1. Relevant map extracts and other plans are included as Figs 2 to 6.
2.5 This assessment has consisted of a review of archaeological and historical information including: • published archaeological studies of Avebury and its landscape; • data held by the Wiltshire Council Historic Environment Record (hereafter WCHER), acquired in June 2016; • data held by the Historic England Archive (hereafter HEA), Swindon, acquired in June 2016 and a review of oblique photographs in February 2017; • historic records and maps held by the Wiltshire Record Office in Chippenham; • online information including exploringavebury.com (a website set up by Steve Marshall); • Magic website (www.magic.gov.uk) and on the Historic England National Heritage List for England (NHLE), accessed on 11th March 2016; • a site walkover undertaken on 1st July 2016; • personal communications with Professor Tim Darvill regarding his current fieldwork in the Avebury landscape and other discussions, and; • Lidar data held by the Environment Agency;
2.6 This assessment has provided a summary of all recorded heritage assets within the study area based on a search of a range of archaeological publications and databases. The key information for this study has been the extensive range of publications based on a long history of field investigations in the Avebury area. Other sources such as early maps, air photographs have also been consulted. However, each source has its own limitations. Aerial photographs are of variable usefulness depending on geology, land-use, the particular season and weather conditions, while certain types of remains produce no cropmarks or soil marks. Documentary sources were seldom compiled for archaeological purposes, contain inherent biases, and provide a comprehensive basis of assessment only for the last two hundred years. National and county heritage databases are also limited in that they only provide a record of known archaeological data.
2.7 The geophysical surveys have comprised gradiometer and resistivity surveys and have been undertaken in accordance with a Section 42 licence issued by Historic England.
2.8 The assessment of setting has been undertaken in accordance with Historic England’s Historic Environment Good Practice Advice in Planning: 3 The Setting of Heritage Assets.
3. ARCHAEOLOGICAL INVESTIGATIONS, HISTORIC MAPS AND OTHER INFORMATION
3.1 In 1986, the prehistoric landscape of Avebury, in which the Sarsen Kennels site is located, was designated as a World Heritage Site (Stonehenge, Avebury and Associated Sites – ICOMOS 2011). Sarsen Kennels itself is part of a Scheduled Monument (ref. 1015547) due to its location within the projected line of the West Kennet Avenue (Fig. 1: 5). The West Kennet Avenue is a double line of standing stones that is believed to link the main Avebury henge (ref. 1015546), West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 3
approximately 2km northwest of Sarsen Kennels, with the Sanctuary (Fig. 1: 10), also a Scheduled Monument (ref. 1014563), which is about 300m east of the Kennels. Although the Avenue is often thought to run for approximately 2.4km between the Avebury henge and the Sanctuary, the central area has few surviving stones. Within the eastern part of the Avenue, which is closer to the Sanctuary, there is no evidence for surviving upstanding stones or evidence for stone pits that would have held any stones in their upright positions.
3.2 The evidence for the Avenue extending into the Sarsen Kennel area and then linking with the Sanctuary is based less on archaeological evidence and more on sketch plans from the 17th to the 19th centuries and speculative reinterpretation of some of this early antiquarian 'research'. Although isolated stones are found in the vicinity (Fig. 1, top and centre), Professor Darvill, who is currently undertaking large scale geophysical survey in the Avebury landscape, has suggested that “...so far we cannot see the West Kennet Avenue extending much beyond the limit of Keiller's excavations” (pers. comm. 18 July 2016). This statement reaffirms the fact that there has never been conclusive evidence that the West Kennet Avenue linked the Avebury henge with the Sanctuary. The West Kennet Avenue could quite conceivably be two or more separate monuments (see below).
3.3 The following sections assess the current archaeological research and cartographic evidence for the West Kennet Avenue and whether there is any conclusive evidence that it extended as one entity as far as the Sanctuary.
West Kennet Avenue: Archaeological Evidence
3.4 In terms of archaeological investigations, the northern section of the West Kennet Avenue was subjected to thorough excavation and restoration by Alexander Keiller in 1934-5 and 1939 (Smith 1965). This restored stretch gives us the best impression of the original form of the monument (or at least how it stood in this part of the Avebury landscape). If it did continue along the entire length, the Avenue is believed to have consisted of over 100 pairs of stones made of unmodified sarsen which, according to current thinking in 2002:
“… takes a sinuous course over undulating ground, running along the foot of Waden Hill, skirting the edge of the Kennet Valley at West Kennet, before making a steep climb to the southern spur of Overton Hill. As it approaches the Sanctuary the longitudinal and transverse intervals of the stone settings progressively decrease” (Pollard and Reynolds 2002)
3.5 Although it is easy to see the Avenue as a single entity, it has been argued that it may well have been constructed in stages, and perhaps laid out in a series of short lengths, with the middle and a short section leading from the southern entrance of the Avebury henge being the earliest phase of construction (e.g. Pollard and Reynolds 2002). Absolute dating for the Avenue has not been possible, although one part of the monument is later than an area of late 4th to early 3rd millennium BC occupation that it crosses. The section joining the Sanctuary appears to belong to the mid-3rd millennium BC, as a large sherd of Grooved Ware from the stone hole 15b looked quite fresh when it was recovered (Pollard and Reynolds 2002:101).
3.6 A geophysical survey in 1990 determined the position of further stones running in a southeast direction, but the results did not show a full avenue of stones. In more recent years, Darvill and
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 4 Leuth have carried out further geophysical survey within the Avebury landscape (Darvill pers. comm.). This has included the fields to the south of the 1990 geophysical survey as far south as Waden Hill and the northern edge of West Kennet village. The survey included a small area of land to the east of the Avebury to West Kennet road, in an area into which it is possible the Avenue extended. Darvill has stated that this work failed to located evidence beyond the area excavated by Keiller (Darvill pers. comm.).
3.7 A more recent study of Avebury and its surrounding landscape by Marshall (2016) discusses whether the West Kennet Avenue ran continuously to the Sanctuary. As a starting point for this study, he cites John Aubrey’s c. 1663 plan (see Fig. 2), which shows the avenue running due south from the Avebury henge and stopping near West Kennet. From this location, another avenue runs due east (almost at right angles) to the Sanctuary. Marshall sees a distinct gap between the two avenues, and suggests that this may be because a small river crossed this area (as shown on some maps in the area of West Kennet Farm, including some recent OS maps). Marshall argues that this river, which flows into the River Kennet, would have been a significant feature during the time of Avebury, and the River Kennet itself would have been a much wider, braided riverine feature than it is today, due in part to Medieval water management that helped drain the area more effectively. It has therefore been argued that it is possible that the Avenue was never continuous and had a gap at West Kennet to allow for this river and wet area (Marshall 2016:100). Marshall suggests that the two segments of the Avenue (from the Avebury Henge and from the Sanctuary) may have both been linked to the river and draws parallels with other henge sites such as Durrington, which also had an ‘avenue’ that terminated at a river (Marshall ibid).
3.8 A further factor to consider is that this area of West Kennet, particularly to the south of the A4 contains some large-scale Neolithic palisaded enclosures (see Section 4.7). There may well have been some form of relationship between these enclosures, which are believed to be contemporaneous in date, and the different segments of the West Kennet Avenue. This is especially the case as they appear to be located in a similar river valley setting as discussed above. Such discussions are largely outside the scope of this study, but it does emphasise that the West Kennet Avenue may be a more complex monument than previously thought.
The Sanctuary: Archaeological Evidence
3.9 The Sanctuary (Fig. 1: 10) is located at the terminus (or start?) of the West Kennet Avenue, and consisted of a complex timber and stone monument located on the southern spur of Overton Hill. The Sanctuary is set in a landscape where it commands good views along the Kennet valley to the west, where both West Kennet and East Kennet long barrows, as well as Windmill Hill, are clearly visible. The palisaded enclosures (see Section 4.7) would also have been prominent landscape features.
3.10 It is considered likely that the Sanctuary’s timber structure pre-dated the stone one, which survived as a circle of two concentric rings of stone until the 1720s, when it was destroyed by local farmers (William Stukeley recorded this event - see 3.13 below and Fig. 3). In the 1930s it was ‘rediscovered’ and excavated by Maud Cunnington (1931). Artefactual evidence including chisel arrowheads and Groove ware pottery from the post-holes suggests a construction date of c. 2500BC and, because the outer stone circle of the Sanctuary has stones from the West
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 5 Kennet Avenue ‘linking’ it, it was thought that this part of the Avenue was contemporaneous in date.
3.11 Although the Sanctuary appears to date to the mid-3rd millennium BC, there is evidence, including an extensive scatter of Peterborough ware pottery, from the 4th and early 3rd millennia, to indicate that the area was occupied prior to the construction of the monument. Cunnington’s excavations revealed stone holes for two concentric circles with an overall diameter of c. 40m. An entrance faces northwest, slightly offset to the north of the line of the West Kennet Avenue as it approaches the Sanctuary and joins the outer stone circle. In addition to the two stone circles, there is a complex of post-holes making up a series of timber circles. There has been much discussion relating to whether these timber circles represented timber buildings or roofed structures with complex phasing, and whether some formed ‘corridors’ leading to the centre of the monument (e.g. Piggott 1940, Pitts 2000, Pollard and Reynolds 2002). The detailed discussions regarding the form and function of the Sanctuary is, however, outside the scope of this study.
Historic Maps and other records
3.12 The first published record of the West Kennet Avenue was made by John Aubrey in the 17th century (c. 1663), when he included a sketch of the surviving stones in his studies of Avebury, although he originally visited the Sanctuary in 1649. His plan included an inset drawing of the Sanctuary showing a double row of eleven stones leaving the monument and heading towards the Sarsen Kennels site (see Fig. 2). Aubrey wrote that the Avenue stones were ‘four or five foot high, tho’ most of them are now fallen down’. The drawing shows the avenue running entirely south of the modern A4.
3.13 In the 18th century, William Stukeley came to see Avebury with the Beckhampton and West Kennet Avenues as resembling a serpent with its head formed by the Sanctuary. His 1723 depiction of the Sanctuary ruins shows a view looking towards Silbury Hill, West Kennet and Avebury itself on the horizon (see Fig. 3). The drawing shows fewer Avenue stones than Aubrey’s Sanctuary plan and is likely to be due to farmers removing stones, most of which has disappeared by the 1720s. A few stones are shown on the drawing, together with an earthwork that resembles a bank or a trackway of some kind, possibly aligned with the Avenue. (see Paragraph 3.17 for further information regarding the use of Stukeley’s drawings in relation to the West Kennet Avenue in the area of the Sanctuary).
3.14 A further schematic plan dating from 1812 shows Avebury with both the Beckhampton and Kennet Avenues, and marks the position of surviving stones along with a double dotted line to show the projected routes of the Avenues (Fig. 4). This plan is taken from Colt Hoare’s ‘The Ancient History of Wiltshire Vol II’ of 1812. Although it is inconclusive, it does appear that an Avenue stone may have survived in the Sarsen Kennels site area, near the junction with the road that leads to East Kennet. In addition, it would appear from the plan that two further stones were recorded on the south side of the London Road (now the A4) between the East Kennet junction and the village of West Kennet, just to the west of Sarsen Kennels.
3.15 One of the map extracts in the Revd A. C. Smith’s 1884 publication show the same stone within the Sarsen Kennels site, near the junction with the road leading to East Kennet, as well four further stones (marked on this map as red dots) heading towards West Kennet (Fig. 5).
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 6 Although these four stones are also shown on the 1887 OS map, there is no evidence on this map for the stone surviving within the site itself (Fig. 6). There is clearly a discrepancy between the 1812 map, which shows only two stones along this part of the route near the present day A4, and the 1884 and 1887 maps, both of which show four stones.
3.16 The four stones shown on the Smith and OS maps (Figs 5 and 6) are shown as ‘existing stones’ on the map in Marshall (2016: 98), displayed as red dots (79b - 82b); a further stone in this area is shown as ‘destroyed’ (83b). A second ‘destroyed’ stone is shown within the Sarsen Kennels site area and is numbered 87. It would appear that Marshall is marking this as the stone recorded by Smith (Fig. 5) and possibly by Colt Hoare (see Fig. 4). As it is not recorded on the First Edition OS map, which was surveyed in c. 1887, it is possible that it was removed in the mid-1880s. This stone could also correspond, with a certain artistic licence, with one of the surviving stones shown in Stukeley’s 1723 depiction (see Fig. 3).
3.17 In Marshall (2016:141), on the final page of the book, there is a Google Earth aerial photograph showing the Sarsen Kennels site with a double series of ten stone positions (89a and 89b to 98a and 98b) superimposed onto the image. This indicates six double stones (or rather their stone pits) existing within the site. There is no discussion in Marshall's (2016) book regarding these stones. However, his companion website (www.exploringavebury.com) contains further information that is not addressed in the main text of the book. Book Notes pages 90 - 100 contains extracts of some of Stukeley’s maps (the so-called Main Plan and the Variant Plan). Although Marshall's Book Notes text does not discuss additional evidence for the West Kennet Avenue within the site area and extending towards the Sanctuary, there is a further web-link to a text that Marshall compiled in 2011 based on OGS Crawford's unpublished analysis of some of Stukeley’s plans and maps (see Page 99 - OGS Crawford and the West Kennet Avenue - CRAWFORD WKA). In this document, which includes Crawford's projected route of the West Kennet Avenue extending as far as the Sanctuary, it is clear that many of the positions of the stones within the site area and approaching the Sanctuary are taken from Stukeley 'estimating' the distance between the stones at 75 feet, with no physical evidence for the stones, together with Crawford then proving the approximate stone positions by looking for different colourations in the soils. Marshall's paper also includes evidence of Isobel Smith's review of the Crawford stone numbering system and the validity of the earlier work. Apart from some revisions to the earlier numbering of the stones, she states "No more known to exist between 83b and the Sanctuary"- that is, the area to the east of the road leading to East Kennet. This suggests Smith had a high level of scepticism for the Crawford work, and is probably the reason why Marshall did not discuss any of this work in his published book, aside from plotting the approximate positions of Crawford's stones on the Google Earth image. It should be concluded that this depiction of stone positions is inaccurate and not to be relied upon.
3.18 The same Google Earth image, which is the current one in the book, has been consulted and there were no cropmarks or soilmarks indicating stone pits.
4. HERITAGE ASSETS WITHIN THE BROADER AREA
4.1 In terms of other archaeological / heritage assets within Sarsen Kennels and the broader study area, data from the HEA and WCHER were collated and assessed and the results are included in this section and in included on Fig. 1 and Table 1. This provides a broader archaeological
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 7 context to the West Kennet Avenue and the Sanctuary and outlines the extent of further Neolithic and Bronze Age sites, as well as other later features.
4.2 In addition to the projected line of West Kennet Avenue, several non-designated heritage assets of probable prehistoric, Roman and Medieval origin are located within the Sarsen Kennels site and its environs. This information is summarised in Fig. 1 (Within or in close proximity to the site). Possible medieval features are described in the HER as ‘Medieval village type earthworks’ (Fig. 1: 3) and it is possible that an earthwork bank may extend into the site. A Roman road representing the route between Bath and Mildenhall is located approximately 400m north of the site area (Fig. 1: 6).
4.5 Archaeological ‘events’ in the form of watching briefs (Fig. 1: 7 and 8) in advance of laying cables in the area of Sarsen Kennels did not find any archaeological deposits. However, a geophysical survey (Fig. 1: 9), on land to the north of the site area, identified a curvilinear anomaly (a possible ploughed out barrow) and some pit-like features that may be of prehistoric date, but do not correspond to possible avenue alignments.
The Sanctuary Area
4.6 The Sanctuary is located approximately 300m east of Sarsen Kennels (Fig. 1: 10). In addition to the Sanctuary monument itself (which is described in more detail in Sections 3.9 - 3.11), there are further prehistoric burial deposits within this area. These include burials adjacent to the Sanctuary.
4.7 Barrow cemeteries of the Overton Hill and Seven Barrow Hill Groups (see Fig. 1: 13 to 37) are burial sites consisting of upstanding Early Bronze Age barrows, most of which are Scheduled Monuments.
West of the Sarsen Kennels Site
4.8 The area to the west of the site also contains further prehistoric sites (see Fig. 1). Although a significant number of these sites relate to prehistoric monuments, particularly of Neolithic and Bronze Age date and thus contemporary with the Avenue and the Sanctuary, the detail of most of these sites is not relevant to addressing the specific question regarding the potential for West Kennet Avenue stones, or any remaining stone pits, to be preserved within the site area.
4.9 West of Site contains a very large complex of Neolithic enclosures with many internal and external features (Fig. 1: 38-41) that covers an area of c. 130 hectares. These are located on land south of the A4 at West Kennet. One enclosure straddles the River Kennet, and it is possible that the water courses, where prior to medieval water management, were more extensive and were therefore an integral part of the enclosure complex, similar to that recorded at the nearby Marden henge. Although most of the available information is taken from aerial photographs, excavations by Faith Vatcher in 1971 and Whittle in 1987 have provided some detail. From the limited amount of investigation undertaken, there appear to be two main enclosures; on the southern perimeter of one of these, two concentric ditches held timber uprights that formed near continuous timber walling or palisades. These would have had diameters of 220m and 280m respectively. The second main enclosure appears to have had a single ditch and may have been oval in plan with its widest diameter being approximately 340m.
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 8 These enclosures are considered to have dated between 2500 and 2400 BC and were complex structures made from oak trunks of 80cm diameter. These posts were set into the ground to a depth of c. 2m, indicating that they may have stood 6m to 8m high, making them very significant landscape features that may have been visible from the Sanctuary.
4.10 Although there is no direct evidence that these Neolithic enclosures were associated with the West Kennet Avenue, their potential significance in a very wet area of the River Kennet, could be a future research question (see 3.7 and 3.8 above and Darvill pers. comm.), particularly as there is uncertainty as to how the Avenue straddled or crossed this same valley floor area. Indeed, their location is broadly the area where Marshall (2016: 99-100) suggests that the West Kennet Avenue is in fact two monuments juxtaposed with the small water course that flows into the River Kennet (see Sections 3.7 and 3.8)
5. AIR PHOTOGRAPHS AND LiDAR
5.1 The air photographs held by the Historic England Archive (HEA) in Swindon have been consulted. In total, there were 30 vertical photographs and a number of obliques, ranging in date from 1928 to 2008. Although many of the upstanding earthworks were clearly visible, such as the Bronze Age barrows from the Overton Hill and Seven Barrow Hill groups, there was no new evidence to assist in assessing whether the Avenue extends into the Sarsen Kennels site. To the north, some of the air photographs clearly show the upstanding stones towards the area of Avebury henge. However, only upstanding stones are visible. No ‘stone pits’ in areas where the sarsen stones had been removed are visible from the air photographs. This suggests that air photography is not an effective approach to assessing the potential for Avenue stones to survive in the site area.
5.2 The earliest photograph, taken by OGS Crawford and dated 25th June 1928 (Plate 1), shows the area prior to the excavation of The Sanctuary in 1930. The area now occupied by Sarsen Kennels is shown as in use as allotments or small market garden plots with several structures fronting onto the A4.
5.3 A further OGS Crawford photograph dated 15th May 1933 (Plate 2) shows the now excavated Sanctuary and the site of Sarsen Kennels still in use as allotments or market gardens although several these have now been amalgamated into larger plots. A Cambridge University Collection of Aerial Photography (CUCAP) oblique photograph shows slight crop marks forming a pair of parallel linear features running to the south of, and parallel to, the A4. These are interpreted as indications of the MOD pipeline constructed between Avonmouth and South-East England (CUCAP SU1168/44). Apart from these cropmarks, no other features of archaeological origin were noted within the study area and it is clear that these photographs were not related to the ground investigations undertaken by Crawford, discussed above.
5.4 Within the area of Sarsen Kennels, photographs dating to 1972 show little construction on the site, apart from the building that fronts onto the A4 road. The remaining triangle of land appears relatively empty of other buildings or structures. The next series of air photographs dates to 1996 and shows the grouping of buildings and structures in a broadly similar pattern as at present.
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 9
5.5 The 1m LiDAR dataset for the Avebury environs was acquired from the Environment Agency and analysed for any topographic features not apparent through the visual inspection of the Site and surrounding areas; this is the highest resolution dataset currently available. This is presented in Fig. 7 as a Roughness Index of the Digital Surface Model (DSM) to highlight localised variations in height, suitable for the identification of archaeological features; the Digital Terrain Model (DTM) was also consulted, although it was noted that the post-processing had effectively removed significant features such as the extant stones along the Avenue close to Avebury and it was therefore considered less suitable for these purposes than the DSM. Hillshades and pseudocolour plots were generated to confirm the product of the Roughness Index function.
5.6 No features of archaeological interest were identified within the Site nor in the immediate vicinity; however, other known archaeological features were clearly visible, such as the Bronze Age barrows on Overton Hill. The Sanctuary is barely visible, although this is not surprising given the small scale of the existing markers and the resolution of the dataset. To the west of the Site, the terrace overlooking the River Kennet is apparent, along with traces of the current and former field systems. The visibility of such small-scale features suggests that any substantial topographic features associated with the Avenue would be detectable if they were present; whilst a higher-resolution dataset would provide additional confidence, it is unlikely to reveal further features relating to the monument.
6. GEOPHYSICAL SURVEY
6.1 Following the initial Historic Environment Assessment, the results of the desk-based investigation and its recommendations were discussed with Historic England and it was determined that a geophysical survey was an appropriate technique to provide supplemental evidence for the presence or absence of in situ sarsens or their sockets along the predicted line of the Avenue.
6.2 Gradiometer and resistivity surveys were undertaken in December 2016 by Archaeological Surveys across four areas; two of these were within the Sarsen Kennels site and the others to the east and west of the proposed development area. These additional areas were chosen as the Sarsen Kennels site has clearly undergone some landscaping, with terraced lawns visible around the kennels and to the south of the existing house. Whilst ground penetrating radar (GPR) survey was considered to be an effective technique, its nature makes it less suitable for wide area prospection and is better used for targeted investigations.
6.3 The additional survey was undertaken across the land to either side in order to determine whether anomalies consistent with in situ stones or their sockets could be detected along the predicted line of the Avenue, thereby allowing the route of the Avenue to be extrapolated into the proposed development site. The full survey is contained in Appendix 1.
6.4 The results of the gradiometer survey were dominated by magnetic disturbance associated with steel pipes orientated E-W and passing to the south of the site. The field to the west was littered with isolated ferrous responses, presumably associated with agricultural practices over time. Few targets of clear archaeological interest were identified, although possible pit-like anomalies were noted, including a cluster some 50m west of the Sanctuary; two possible alignments can be seen within these anomalies but neither is consistent with the predicted line of the Avenue.
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 10
6.5 The datasets from the resistivity survey were more encouraging, as the instrument is unaffected by the strong magnetic anomalies caused by the pipelines that masked the majority of the gradiometer data, although the physical disturbance is still apparent. A number of small pit-like responses can be seen close to the Sanctuary, although these are apparently distributed in a band orientated N-S or perhaps concentrically around the Sanctuary, and little linearity corresponding with the line of the Avenue can be discerned. Several high resistance anomalies can be seen west of the site, although the nature of these is uncertain; whilst buried sarsens may cause a similar response, the spacing between them is less than half of that elsewhere along the Avenue. Several linear anomalies can be seen, particularly close to the site and to the Sanctuary, although it is difficult to ascribe a definitive interpretation to any of them.
6.6 Whilst the results of the gradiometer survey were somewhat disappointing through the extents of magnetic disturbance, the resistivity dataset was markedly clearer. There is little evidence for an alignment of in situ sarsens or their sockets to the south of the A4. It is possible that some of the pit-like anomalies close to the Sanctuary are associated with the Avenue, although evidence for the monument in the vicinity of Sarsen Kennels is unfortunately lacking, largely through previous development, landscaping and the construction of the nearby pipelines.
7. COMMENTS
7.1 The prehistoric landscape of Avebury is designated as a World Heritage site and individual elements within it are designated as Scheduled Monuments. This includes the entire projected route of the West Kennet Avenue from the Avebury henge to the Sanctuary, including areas where no avenue stones survive. This means that the site of Sarsen Kennels has scheduled status.
7.2 Although there is no conclusive archaeological evidence for Avenue stones within the site area, there is, however, pictorial evidence both from Aubrey (c. 1663) and Stukeley (1723) that Avenue stones extended westwards from the Sanctuary towards the Sarsen Kennels site on an alignment south of the modern A4. The Avebury plan from Colt Hoare dating to 1812 (Fig. 4) and Smith’s 1884 map (Fig. 5) both show a possible stone in the western corner of the site area, together with up to four in land immediately to the west of Sarsen Kennels. Although these four stones are marked on the OS First Edition 1887 map, the one within the site area is not recorded on this later map. Based on this information it is considered possible that the West Kennet Avenue did extend across the Sarsen Kennels site, although it is uncertain how much of the route of the Avenue has been truncated by the A4 road and its roadside banking. Marshall’s (2016:141), image showing stone positions superimposed on a Google Earth photo, based on the earlier, inconclusive work of Crawford, is a further reason to investigate this area. A possible alignment through the Sarsen Kennels site is shown on Fig. 7.
7.3 Based on the evidence from the 1812 and 1884 maps (and possibly Marshall’s (2016) ‘reuse’ of Crawford's work superimposed on a Google Earth air photograph), there is a distinct possibility that survey work in the form of geophysical survey or ground radar may pick up surviving stone pits in the site area.
7.4 The Wiltshire Council HER confirms that the site area may have a Medieval bank feature surviving (Fig. 1:2). However, it is unlikely that this feature would be considered important
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 11 enough to warrant preservation in situ. A programme of geophysical survey on land to the north of the A4 indicates that the area in general has the potential to contain further prehistoric deposits (Fig. 1:9), and it is conceivable that further prehistoric sites, including burial sites may extend into the site area. However, if they did survive, they would be severely damaged by building work and landscaping for gardens, etc.
8. REFERENCES
Chartered Institute for Archaeologists, 2014. Standard and Guidance for Desk-Based Assessment. Professional guidance (1994, revised 2014)
Colt-Hoare, R., 1812. The Ancient History of Wiltshire Vol II. Originally published in 1812
Cunnington, M., 1931. The ‘Sanctuary’ on Overton Hill, near Avebury. In Wiltshire Archaeological and Natural History Magazine vol xiv pp 300-335
Historic England National Heritage List for England (NHLE)
International Council on Monuments and Sites (ICOMOS, 2011)
MAGIC website (www.magic.gov.uk)
Malone, C., 1989. Avebury. English Heritage
Marshall, S., 2016. Exploring Avebury: The Essential Guide. The History Press
Marshall, S., www.exploringavebury.com (companion website to above book, visited February 2017)
Piggott, S., 1940. Timber Circles: A re-examination. In Archaeological Journal 96(2) 193-222
Pitts, M., 2000. Return to the Sanctuary. In Brit Archaeol 51 14-20
Pollard, A. and Reynolds, A., 2002. Avebury: The Biography of a Landscape (Tempus)
Pomeroy – Kellinger, M., 2005. Avebury World Heritage Site: Management Plan. English Heritage
Smith, A.C., 1884. British and Roman Antiquities of Wiltshire: A Hundred Square Miles Round Abury.
Smith, I.F., 1965. Windmill Hill and Avebury: Excavations by Alexander Keiller 1925 – 1939 Clarendon, Oxford
Stukeley, W., 1743. Abury: A Temple of the British Druids with some others described.
Ucko, P. et al 1991. Avebury Reconsidered: From the 1660s to the 1990s. Unwin Hyman
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 12 Other maps not in above texts:
Aubrey, J., c. 1663 map
OS 1887 First Edition map
West Kennet Avenue in the vicinity of Sarsen Kennels, near Avebury, Wiltshire Report no. ACW912/1/2 Page 13 Site No. LEN/HEA/HER Ref: Grid Ref Description 1 MWI 13451 SU11666811 Ring ditch, Overton Hill 2 MWI14394 SU11306814 Village with medieval origins. Includes a single earthwork bank. 3 MWI14407 SU11576811 Medieval village earthworks, SE of Sarsen Kennels 4 MWI14543 SU11556803 Possible undated enclosure visible as faint cropmark 5 LEN 1015547 SU11046887 West Kennet Avenue (see main text for more detail) 6 MWI14345 SU08636802 Roman Road- Bath to Mildenhall 7 EWI14860 SU11566814 Watching brief for a cable junction pit. Nothing of archaeological significance found 8 EWI6011 SU11806821 Watching brief for Project 654. A series of cable trenches. Nothing of archaeological significance found. 9 EWI6755 SU11786808 Geophysical survey at Overton Hill for proposed route of electricity cables. A curvilinear feature may relate to nearby Bronze Age barrows and possible pit-like features. 10 LEN 1014563 SU11826802 The Sanctuary. Two Neolithic stone circles (see main text for more detail) 11 MWI14329 SU11846802 The Sanctuary. Bronze Age Beaker burial 12 MWI14432 SU11846802 Undated inhumation cemetery near the Sanctuary. 13 LEN 1008461 SU11986831 Three Roman burial mounds, a Bronze Age bowl barrow, a pagan Saxon inhumation cemetery and a HER MWI14299 short length of Roman road on Overton Hill HER MWI14330 HER MWI14373 HER MWI14374 HER MWI14375 HER MWI14376 HER MWI14454 HER MWI14551 HER MWI14553 HER MWI14554 HER MWI14555 14 MWI14433 SU11846834 Overton hill, undated stone circle 15 MWI14441 SU11876835 A site of a dubious stone circle 16 LEN 1008102 SU11526855 Group of six round barrows forming part of a Bronze Age cemetery 400m NE of West Kennett Farm HER MWI14448 HER MWI14449 HER MWI14450 HER MWI14554 HER MWI14455 17 LEN 1008463 SU11916850 Bowl Barrow, Overton Hill, forms part of the Overton Hill Bronze Age cemetery HER MWI14497
Table 1: Recorded heritage assets 18 LEN 1007489 SU11836793 Bowl Barrow, Seven Barrow Hill, 50m south of The Sanctuary forming part of the Seven Barrow Hill MWI14457 round barrow cemetery 19 MWI14458 SU11856808 Barrow, Seven Barrow Hill. Levelled earthwork 20 MWI14459 SU11816815 Barrow, Seven Barrow Hill. Levelled earthwork 21 LEN 1008459 SU11896797 Bowl Barrow, Seven Barrow Hill. SE of Sanctuary. Excavated in 19 century MWI14504 22 MWI14505 SU11896803 Site of Bowl Barrow, Seven Barrow Hill. Possibly excavated by Stukeley in 1720 23 LEN 1008464 SU11976818 Group of five round barrows NE of the Sanctuary: part of the Overton Hill round barrow cemetery HER MWI14506 HER MWI14507 HER MWI14508 HER MWI14509 HER MWI14510 24 LEN 1015157 SU11086784 West Kennett Farm palisaded enclosures. HER MWI13424 Late Neolithic sub-circular enclosure and Neolithic settlement site (see main text for more detail) HER MWI14307 25 MWI14558 SU11276802 Undated enclosure (see main text for more detail) 26 MWI14306 SU11196810 Neolithic settlement site (see main text for more detail) 27 MWI14362 SU11256800 Sherd of Roman pottery 28 MWI72766 SU1176802 Bronze Age ring ditch or feature of no archaeological origin. 29 MWI14540 SU18567254 The Ridgeway 30 MWI 13412 SU1150 6847 Linear features, undated concentric rings. Neolithic or geological
Table 1: Recorded heritage assets 169000
29
16
17 30
6 15 2 14 13 6
24 2 23 Sarsen Kennels 7 9 8 20 24 5 1 26 19 3 10 11 25 22 12 168000 28 27 4 21
24 18
29
411000 412000
Key AC archaeology PROJECT Scheduled monument N Sarsen Kennels, West Kennet 500 m Non designated heritage asset 0 TITLE
Event Fig. 1: Location of recorded heritage assets AC archaeology PROJECT Sarsen Kennels, West Kennet
TITLE Fig. 2: John Aubrey’s schematic map c.1663 AC archaeology PROJECT Sarsen Kennels, West Kennet
TITLE Fig. 3: William Stukeley, 1723, showing the Sanctuary in relation to the surrounding landscape AC archaeology PROJECT Sarsen Kennels, West Kennet
TITLE Fig. 4: Sir Richard Colt-Hoare plate showing the Avebury complex Extracted from Guide to British and Roman Antiquities of the North Wiltshire Downs in a Hundred Square Miles round Abury
?Stone
AC archaeology PROJECT Sarsen Kennels, West Kennet
TITLE Fig. 5: Plan by Rev A.C. Smith, 1884 AC archaeology PROJECT Sarsen Kennels, West Kennet
TITLE Fig 6: Extract from 1st edition Ordnance Survey map, 1887 N © Environment Agency
0 200m
Roughness index: white =low, dark = high) AC archaeology PROJECT Sarsen Kennels, West Kennet
TITLE Fig 7: LiDAR data: roughness index
Plate 1: Vertical air photograph taken in 1928 showing the site of Sarsen Kennels in use as allotments or market garden plots with buildings flanking the A4. (North to top. NMR SU119681)
Plate 2. Vertical air photograph showing the site of Sarsen Kennels and The Sanctuary taken in 1933 (north to bottom). The allotments or market garden plots and buildings are still present but a number of the plots appear to have been amalgamated to form a series of larger paddocks. (NMR SU1168/62 CCC 5206/3554)
AC archaeology
APPENDIX 1: GEOPHYSICAL SURVEY REPORT
Archaeological Surveys Ltd
Sarsen Kennels West Kennett Avebury Wiltshire
MAGNETOMETER AND EARTH RESISTANCE SURVEY REPORT
for
AC Archaeology Ltd
David Sabin and Kerry Donaldson December 2016
Ref. no. J688 ARCHAEOLOGICAL SURVEYS LTD
Sarsen Kennels West Kennett Avebury Wiltshire
Magnetometer and Earth Resistance Survey
for
AC Archaeology Ltd
Fieldwork by David Sabin (Hons) MCIfA and Kerry Donaldson BSc (Hons) Report by Kerry Donaldson BSc (Hons) Report checked by David Sabin Primary archive location - Archaeological Surveys Ltd, Yatesbury, Wiltshire
Survey dates – 16th, 19th, 22nd, 23rd & 29th November 2016 Ordnance Survey Grid Reference – SU 11592 68094
Archaeological Surveys Ltd 1 West Nolands, Nolands Road, Yatesbury, Calne, Wiltshire, SN11 8YD Tel: 01249 814231 Fax: 0871 661 8804 Email: [email protected] Web: www.archaeological-surveys.co.uk
Archaeological Surveys Ltd is a company registered in England and Wales under registration number 6090102, Vat Reg no. 850 4641 37. Registered office address, Griffon House, Seagry Heath, Great Somerford, Chippenham, SN15 5EN. It is a Registered Organisation with the Chartered Institute for Archaeologists. Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
CONTENTS SUMMARY...... 1
1 INTRODUCTION...... 2
1.1 Survey background...... 2
1.2 Survey objectives and techniques...... 2
1.3 Site location, description and survey conditions...... 4
1.4 Site history and archaeological potential...... 6
1.5 Geology and soils...... 7
2 METHODOLOGY...... 7
2.1 Technical synopsis...... 7
2.2 Equipment configuration, data collection and survey detail...... 8
2.3 Data processing and presentation...... 9
3 RESULTS...... 11
3.1 General assessment of survey results - magnetometry...... 11
3.2 Statement of data quality - magnetometry...... 11
3.3 Data interpretation - magnetometry...... 11
3.4 General assessment of survey results - resistivity...... 12
3.5 Statement of data quality - resistivity...... 12
3.6 Data interpretation - resistivity...... 13
3.7 List of anomalies – magnetometry Area 1...... 13
3.8 List of anomalies – magnetometry Area 2...... 14
3.9 List of anomalies – magnetometry Area 3...... 14
3.10 List of anomalies – magnetometry Area 4...... 14
3.11 List of anomalies – resistivity Area 1...... 15
i Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
3.12 List of anomalies – resistivity Area 2...... 15
3.13 List of anomalies – resistivity Area 3...... 16
3.14 List of anomalies – resistivity Area 4...... 17
4 DISCUSSION...... 17
5 CONCLUSION...... 19
6 REFERENCES...... 20
Appendix A – basic principles of magnetic survey...... 22
Appendix B – data processing notes...... 23
Appendix C – survey and data information...... 23
Appendix D – digital archive...... 25
Appendix E – copyright and intellectual property...... 26
Appendix F – Historic England Geophysical Survey Database Questionnaire...... 27
LIST OF FIGURES
Fig 01 Map of survey area (1:25 000)
Fig 02 Referencing information (1:2000)
Fig 03 Greyscale plot of processed magnetometer data (1:1500)
Fig 04 Abstraction and interpretation of magnetic anomalies (1:1500)
Fig 05 Greyscale plot of raw earth resistance data (1:1500)
Fig 06 Greyscale plot of processed earth resistance data (1:1500)
Fig 07 Abstraction and interpretation of earth resistance anomalies (1:1500)
Fig 08 Abstraction and interpretation of resistivity & magnetic anomalies (1:1500)
Fig 09 Greyscale plot of processed magnetometer data & abstraction & interpretation of magnetometer anomalies - east (1:1000)
Fig 10 Greyscale plot of processed magnetometer data & abstraction & interpretation of magnetometer anomalies - west (1:1000)
ii Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
Fig 11 Greyscale plot of processed earth resistance data & abstraction & interpretation of resistance anomalies - east (1:1000)
Fig 12 Greyscale plot of processed earth resistance data & abstraction & interpretation of resistance anomalies - west (1:1000)
LIST OF PLATES
Plate 1: Area 1 looking west...... 4
Plate 2: Area 3 looking west towards Sarsen Kennels...... 5
Plate 3: Area 4 looking west...... 5
LIST OF TABLES
Table 1: List and description of magnetometry interpretation categories...... 12
Table 2: List and description of resistivity interpretation categories...... 13
iii
Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
SUMMARY A geophysical survey was carried out by Archaeological Surveys Ltd on land within and to the east and west of Sarsen Kennels, West Kennett near Avebury in Wiltshire. The site lies within the scheduled monument of the West Kennet Avenue, which is believed to extend from Avebury to the north west to the Sanctuary immediately east of the site on Overton Hill. Much of the extent of the West Kennet Avenue comes from antiquarian sketch plans by Aubrey in the 17th century and Stukeley in the 18th century with further investigations by OGS Crawford in 1922 and Isobel Smith in 1965. Four stones have been mapped within the field margin on the southern edge of the A4 to the west of Sarsen Kennels from 1885 onwards. Although the line is purported to extend within the Sarsen Kennels property and beyond to the east, based on Stukeley's sketches and OGS Crawford's observations, no intrusive investigation has been carried out to determine this.
An earth resistance survey, supplemented by magnetometry, was carried out within two areas of the Sarsen Kennels garden (Areas 1 & 2) and to the east (Area 3) and to the west (Area 4). The results show a small number of high resistance anomalies within the Sarsen Kennels lawns; however, the site is highly disturbed with dumped material, trees, hedges and modern infrastructure including a septic tank and so while such high resistance responses can relate to buried stones, their archaeological potential cannot be determined due to the widespread modern contamination within the site.
Within Area 4 to the west, a high resistance response adjacent to the hedge appears to relate to stone 86b outlined in Crawford's and Smith's observations. To the south west of this are other high resistance anomalies, forming a line of two and a line of three, parallel with the A4, and also the Avenue. While they may relate to buried stones, it is not possible to determine if they are associated with the Avenue.
Within Area 3 a number of discrete low resistance responses correspond to discrete positive magnetic anomalies which indicate the presence of pit-like features. While such features can be naturally formed, the elongated shape of several could indicate intercut pits, similar to those identified through excavation within the Sanctuary immediately to the east and an archaeological origin should be considered. The line of at least three pipelines can be seen to extend through the northern part of Area 3, and it is possible that these have clipped the northern edge of the Sanctuary.
The results of the survey have not provided conclusive evidence or clarification of the line of the West Kennett Avenue within or immediately adjacent to the Sarsen Kennels.
1 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
1 INTRODUCTION
1.1 Survey background 1.1.1 Archaeological Surveys Ltd was commissioned by AC Archaeology Ltd, on behalf of Mr N Baldock, to undertake a magnetometer and earth resistance survey (resistivity) of an area of land at Sarsen Kennels, West Kennett, Avebury, Wiltshire. The site has been outlined for a proposed development and the survey forms part of an archaeological assessment of the site.
1.1.2 The site lies within the World Heritage Site of Stonehenge, Avebury and Associated Sites and has been designated as a part of the scheduled monument (No. 1015547) West Kennet Avenue and an earthwork bank east of West Kennett Farm . In order to carry out the geophysical survey within the scheduled area, a licence, under Section 42 of the 1979 Ancient Monuments and Archaeological Areas Act (as amended by the National Heritage Act 1983), was granted by Phil McMahon, Inspector of Ancient Monuments for Historic England, prior to commencing the fieldwork.
1.1.3 The owner of Sarsen Kennels is considering a future planning application with proposals that include renovation, conversion and extension of two of the existing buildings that may well be located in the vicinity of where the West Kennet Avenue stones may have been positioned. It is also proposed that other structures are to be removed which may have the potential to enhance the setting of the line of the West Kennet Avenue.
1.1.4 The actual position of the stones within the West Kennet Avenue has been subject to much speculation. It is considered likely that many stones have been destroyed and used within local buildings. As there is the potential for the site to contain stones or stone sockets related to the Avenue, it was proposed that the geophysical survey was undertaken within accessible and suitable parts of the Sarsen Kennels property and also within land immediately to the east and west of the site in order to try to establish the line of the avenue. As the land either side belongs to the National Trust, an Archaeological Research Agreement was granted by the National Trust Archaeologist, Dr Nicola Snashall.
1.1.5 The geophysical survey was carried out in accordance with a Written Scheme of Investigation (WSI) produced by Archaeological Surveys (2016). This was issued to Historic England as part of the Section 42 licence application and to the National Trust as part of the application for the Archaeological Research Agreement.
1.2 Survey objectives and techniques 1.2.1 The objectives of the survey are to use non-intrusive geophysical techniques to establish the presence/absence, extent, condition, character, quality and date of specifically any stones or stone settings and in general any archaeological deposits within the surveyable area.
2 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
1.2.2 Both magnetometry and resistivity were considered potentially useful techniques. Previous resistivity surveys carried out within the World Heritage Site and targeted on buried sarsen stones, or the location of former stones, have demonstrated useful results, with both high and low resistance anomalies located.
1.2.3 Prior to the survey, magnetic susceptibility tests were conducted using a Bartington MS2 meter on both burnt and unburnt sarsen fragments (approximately 300mm across) collected from land to the east of Swindon. It is known that large sarsens in the vicinity of the site were broken up by the use of fire. The unburnt fragments demonstrate a diamagnetic response with a very slightly enhanced magnetic susceptibility for burnt pieces. The latter were subject to intense heat and were slightly reddened in colour suggesting the presence of a very small amount of ferrous mineral within the rock. However, it is considered very unlikely that burnt or unburnt sarsens could be located by magnetometry. It may be possible to locate soil subject to intense burning where sarsens have been destroyed as its magnetic susceptibility is likely to be considerably higher. Magnetic survey may also locate other former cut features such as ditches and pits. A geophysical survey within the line of the Beckhampton Avenue located weakly positive magnetic responses interpreted as possible burnt sarsens associated with a pit (David et al, 1999) with resistivity indicating buried stones. Subsequent excavation revealed several pits containing buried sarsens and pits with removed sarsens (Gillings et al, 2000).
1.2.4 Much of the land within the Sarsen Kennels property has been developed with buildings, fences, vegetation and terraced gardens. The actual development area was considered unsuitable for survey. However, work was carried out in accessible and suitable areas; the lawn to the east of the property and the two fields to the east and west of the property, based on the purported positions of the stone settings of the West Kennet Avenue. The outlined survey area therefore covered the two lawned areas within the Sarsen Kennels gardens (Areas 1 & 2) and a zone to the east (Area 3) and to the west (Area 4), based on the line of the Avenue as indicate by OGS Crawford from Stukeley's sketch plans and his own observations of discoloured soils in 1922. However, the survey was extended towards the Sanctuary at the eastern edge of the site in order to be able to determine if any stone settings extended away from the monument.
1.2.5 The survey and report generally follow the recommendations set out by: English Heritage (2008) Geophysical survey in archaeological field evaluation; European Archaeological Council (2015) Guidelines for the Use of Geophysics in Archaeology; Institute for Archaeologists (2002) The use of Geophysical Techniques in Archaeological Evaluations . The work has been carried out to the Chartered Institute for Archaeologists (2014) Standard and Guidance for Archaeological Geophysical Survey.
3 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
1.3 Site location, description and survey conditions 1.3.1 The site is located at Sarsen Kennels, West Kennett, Avebury, Wiltshire. It is centred on Ordnance Survey National Grid Reference (OS NGR) SU 11592 68094, see Figs 01 and 02.For the purposes of this report, the site includes four separate survey areas which are described below.
1.3.2 Survey Areas 1 and 2 cover two small lawns amounting to 0.1ha immediately east of the proposed development. Both magnetometry and resistivity were carried out across the areas. The ground cover was short grass, Area 1 slopes down gently towards the west and Area 2 is generally flat. The former is bounded by buildings, sheds and fencing adjacent to the A4 along the northern side. To the west is a drive and parking area with fencing separating it from Area 3 to the south. Area 2 contains several inspection chambers possibly associated with a buried septic tank in the south western part of the lawn. There are trees and shrubs to the west and east with the house to the north and a drive to the south. The northern part of the lawn contains a large tree. The eastern side of the lawn is edged by sarsen stones.
Plate 1: Area 1 looking west
1.3.3 Area 3 is located within the field to the south and east of the Sarsen Kennels property on land owned by the National Trust. It is a zone that runs from the southern boundary of the Sarsen Kennels to the western boundary of the Sanctuary. Ground cover was long grass that was uneven and thick, a mown footpath crosses the area from east to west. Land slopes down from an elevated flat area at the Sanctuary to the lane to East Kennett. Approximately 1.35ha was covered using magnetometry and 0.8ha with resistivity. The survey area was extended from that proposed in the WSI due to widespread magnetic disturbance relating to buried pipelines obscuring much of the originally proposed survey zone. Although the resistivity survey was generally unaffected by the pipelines, the extension of this technique also was useful in clarifying the nature and extent of some anomalies.
4 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
Plate 2: Area 3 looking west towards Sarsen Kennels
1.3.4 Area 4 is a 30m wide strip within the field to the west of the lane to East Kennett located to the west of Sarsens Kennels. It lies immediately south of the hedgerow bounding the A4. Both magnetometry and resistivity were carried out over 0.4ha. The ground cover consisted of long grass and the hedgerow had spread into the field in places. A mown strip running from south east to north west crosses the western part of the area and defines the course of a footpath. An area of thick nettles appeared slightly raised possibly indicating recent deposition of soil or manure. Three large sarsen stones were visible within the boundary with the A4; one placed on top of another near the western end of the survey area and one to the north west of the central part of the survey. A distinct mound extending from the hedge into the field, close to the central part of the survey area, was considered a likely candidate for a buried sarsen.
Plate 3: Area 4 looking west
5 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
1.3.5 The ground conditions across the site were variable with challenging conditions within Areas 3 and 4 due to the presence of thick and tall ground cover impeding both magnetometry and resistivity.
1.3.6 Weather conditions during the survey were variable with survey abandoned on 2 days due to heavy rainfall. However, ground moisture at deeper levels was considered likely to be low for the time of year due to extended periods of dry weather through the Summer and Autumn.
1.4 Site history and archaeological potential 1.4.1 A desk-based assessment of evidence for the West Kennet Avenue in the vicinity of Sarsen Kennels has been carried out by AC Archaeology (2016). The site lies within the World Heritage Site of Stonehenge, Avebury and Associated Sites and is part of the scheduled area (No. 1015547) West Kennet Avenue and an earthwork bank east of West Kennett Farm . The West Kennet Avenue is a double line of standing stones that is believed to link Avebury henge (2km to the north west) with the Sanctuary (150m to the east); however, there are few surviving stones. Much of the inferred position of the stones is based on antiquarian drawings by Aubrey and Stukeley in the 17th and 18th centuries, but also on the work of OGS Crawford in the 1920s in which he derived the positions from measurement of Stukeley's drawings and based on his own observations of the soil. This has been transposed onto Google Earth by Steve Marshall (2016a & 2016b) and the positions are indicated in Fig 2. Isobel Smith also recorded the line of the stones to the west of Sarsen Kennels in the 1960s and the position of four stones has been recorded in the western field since the first edition Ordnance Survey map in 1885.
1.4.2 The Sanctuary lies to the east of the survey area, on Overton Hill, first described as Millfield circle on Seven Barrow Hill by Aubury in the 17th century, named the Sanctuary by Stukeley in the 18th century. It was excavated in 1930 by Maud Cunnington where it was discovered to consist of two stone circles and six concentric circles of post-holes, with one containing an adolescent burial (Cunnington, 1931). Part of the site was re-excavated in 1999, which revealed that several of the pits were "doubles" or had several re- cuts and therefore appear more oval in shape, rather than circular. It appears that there were large timber posts erected, removed and replaced in what could be a short timescale (Pitts, 2001).
1.4.3 The eastern part of the site also contains an oil pipeline that was part of the Government Pipelines and Storage System, known as the CLH Pipeline System from 30th April 2015 when it was sold to a Spanish company. The pipeline extends from Avonmouth, eastwards to Aldermaston and eventually links up to the Isle of Grain in Kent. The network of pipelines were constructed at night during the Second World War, under statutory powers
6 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
relating to the Defence Regulations Act 1939, to supply aviation fuel to airfields across the country (MOD, 2011). They are now part of the commercial aviation fuel supply. A previous geophysical survey within the field established that there was more than one highly magnetic pipeline (Archaeological Surveys, 2008). The presence of the buried pipelines and the resulting widespread and strongly magnetic disturbance indicate that further magnetometer survey would be disturbed, with weaker anomalies obscured. The survey has been carried out using earth resistance measurements, supplemented by magnetometry, to establish the location of the pipelines and also mainly within less disturbed areas, weaker anomalies are likely to be visible.
1.5 Geology and soils 1.5.1 The underlying solid geology across the site from the Holywell Nodular Chalk Formation and New Pit Chalk Formation with overlying deposits of river terrace sands and gravels to the west (BGS, 2016).
1.5.2 The overlying soil across the survey area is on the cusp of the Andover 1 association, which is a brown rendzina and consists of a shallow, well drained, calcareous, silty soil over chalk with soil patterns locally, and the Frome association which is a calcareous alluvial gley soil consisting of shallow, calcareous and non-calcareous loams over flint gravel associated with a river terrace (Soil Survey of England and Wales, 1983).
1.5.3 Magnetometry survey carried out across similar soils has produced good results. However, magnetic susceptibility may be very low and as a consequence soil filled features may lack magnetic contrast and not produce anomalies.
2 METHODOLOGY
2.1 Technical synopsis 2.1.1 Magnetometry survey records localised magnetic fields that can be associated with features formed by human activity. Magnetic susceptibility and magnetic thermoremnance are factors associated with the formation of localised fields. Additional details are set out below and within Appendix A.
2.1.2 Iron minerals within the soil may become altered by burning and the break down of biological material; effectively the magnetic susceptibility of the soil is increased, and the iron minerals become magnetic in the presence of the Earth's magnetic field. Accumulations of magnetically enhanced soils within features, such as pits and ditches, may produce magnetic anomalies that can be mapped by magnetic prospection.
2.1.3 Magnetic thermoremnance can occur when ferrous minerals have been heated to
7 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
high temperatures such as in a kiln, hearth, oven etc. On cooling, a permanent magnetisation may be acquired due to the presence of the Earth's magnetic field. Certain natural processes associated with the formation of some igneous and metamorphic rock may also result in magnetic thermoremnance.
2.1.4 The localised variations in magnetism are measured as sub-units of the Tesla, which is a SI unit of magnetic flux density. These sub-units are nano Teslas (nT), which are equivalent to 10 -9 Tesla (T).
2.1.5 The electrical resistance or resistivity of the soil depends upon the moisture content and distribution within the soil. Buried features such as walls can affect the moisture distribution and are usually more moisture resistant than other features such as the infill of a ditch. A stone wall will generally give a high resistance response and the moisture retentive content of a ditch can give a low resistance response. Localised variations in resistance are measured in ohms ( Ω) which is the SI unit for electrical impedance or resistance.
2.1.6 The Twin Probe configuration used in this survey is favoured for archaeological prospection and can give a response to features up to 1m in depth with a mobile probe separation of 0.5m.
2.2 Equipment configuration, data collection and survey detail 2.2.1 The detailed magnetic survey was carried out using a SENSYS MAGNETO®MXPDA 5 channel cart-based system. The instrument has 5 fluxgate gradiometers (FGM650) spaced 0.5m apart with readings recorded at 20 Hz. The cart is pushed at walking speed and not towed. Each sensor is not zeroed in the field as the vertical axis alignment is precisely fixed leaving sensor offsets that are removed during data processing. The fixing of the vertical alignment ensures the sensors are not unduly influenced by localised magnetic fields and that the vertical component of a magnetic anomaly is measured. The gradiometers have a range of recording data between ±0.1nT and ±10,000nT. They are linked to a Leica GS10 RTK GPS with data recorded by SENSYS MAGNETO®MXPDA software on a rugged PDA computer system.
2.2.2 Due to the fixed offsets within the fluxgate sensors, as a result of the manufacturing and tensioning process, the survey data do not provide a visually useful dataset until a zero median traverse algorithm is applied. It is recognised that this has the potential to affect some anomalies detrimentally by removing linear features orientated parallel to survey transects. However, this has not been noted as a particular problem with the system due to the high resolution data collection, generally long length of traverses and variability within the magnetic characteristics of a linear anomaly.
2.2.3 Data are collected along a series of parallel survey transects to achieve 100% coverage of the surveyable land. The length of each transect is variable and relates to the size of the survey area and other factors including ground conditions. A visual display allows accurate placing of transects and helps maintain the correct
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separation between adjacent traverses. Data are not collected within fixed grids and data points are considered to be random even though the data are collected in a systematic manner covering all accessible areas (Aspinall, Gaffney and Schmidt, 2009).
2.2.4 Fluxgate sensors are highly sensitive to temperature change and this is manifest as drift during the course of a survey. This can be particularly noticeable during the morning as temperatures rise and the equipment warms or cools. Sensor drift within the course of a traverse will appear as a line trending from negative to positive after processing with a zero median traverse algorithm. To remove the potential for temperature drift data were collected after a 20 minute stabilisation period and traverses were limited to a time of generally <100s.
2.2.5 The earth resistance survey was carried out using Geoscan Research Ltd RM85 resistance meter using a mobile parallel twin probe array with a 0.5m electrode separation. Data were recorded at 0.5m intervals along traverses separated by 0.5m. The instrument was set to filter stray earth currents which can cause errors within the resistance measurements. The survey was carried out in a zig-zag fashion over grids 30m in size.
2.2.6 The earth resistance survey grids were set out to the Ordnance Survey OSGB36 datum using a Leica GS10 RTK GPS. The GPS is used in conjunction with Leica's SmartNet service, where positional corrections are sent via a mobile telephone link. Positional accuracy of around 10 – 20mm is possible using the system. The instrument is regularly checked against the ETRS89 reference framework using Ordnance Survey ground marker C1ST7784 (Horton).
2.3 Data processing and presentation 2.3.1 Magnetic data collected by the MAGNETO®MXPDA cart-based system are initially prepared using SENSYS MAGNETO®DLMGPS software. The software effectively allocates a geographic position for each data point and can compensate for fixed offsets present within the FGM650 sensors. The offsets are positive or negative values present on all fluxgate gradiometer sensors. Some systems use manual or electronic balancing to effectively zero the sensors; however, this is a short term measure that is prone to drift through temperature changes and vibration and can easily be incorrectly set due to localised magnetic fields. The FGM650 sensors are very accurately aligned to the vertical magnetic gradient and are highly stable showing negligible drift on long traverses. The offset values are removed using TerraSurveyor software.
2.3.2 Survey tracks are analysed and georeferenced raw data (UTM Z30N) are then exported in ASCII format for further analysis and display within TerraSurveyor. The removal of offset values (compensation) of the sensors is also carried out in TerraSurveyor using a zero median traverse function. Data are then considered to be minimally processed. Note: without the zero median traverse
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function it is not possible to create a meaningful data plot as all sensors have a different offset value. Although a zero median traverse algorithm can remove anomalies aligned with the survey tracks, in practice this rarely occurs due to the use of long traverses, high resolution measurement and variability within the magnetic susceptibility of long linear features.
2.3.3 The minimally processed data are collected between limits of ±10000nT and clipped for display at ±5nT. Data are interpolated to a resolution of effectively 0.5m between tracks and 0.15m along each survey track. Additional data processing has been carried out for Areas 1 and 3 in the form of high pass filtering (Fig 11). This effectively removes low frequency variation along a traverse that has been caused by large magnetic bodies, cultivation, rapid temperature change. Data treated to additional processing has been compared to unprocessed data to ensure that no significant anomalies have been removed.
2.3.4 Appendix C contains metadata concerning the survey and data attributes and is derived directly from TerraSurveyor. Reference should be made to Appendix B for further information on processing.
2.3.5 A TIF file is produced by TerraSurveyor software along with an associated world file (.TFW) that allows automatic georeferencing (OSGB36 datum) when using GIS or CAD software. The main form of data display used in the report is the minimally processed greyscale plot. With regard to the Sensys MXPDA, minimally processed data is considered by the manufacturer to be data that is compensated by SENSYS MAGNETO DLMGPS software, see 2.3.1 and 2.3.2. Note: traceplots are not considered to be appropriate as they do not provide an accurate or useful assessment of the magnetic anomalies due to very high density of data collection.
2.3.6 Data logged by the resistance meter are downloaded and processed within TerraSurveyor Geoplot 4 software. Raw data are analysed and displayed within the report as well as processed data. Appendix C outlines the processing sequence with further information on processing set out within Appendix B. TIF files are prepared in TerraSurveyor Geoplot 4 for the earth resistance data. The main form of resistivity data display used in the report is the minimally processed greyscale plot.
2.3.7 The raster images are combined with base mapping using ProgeCAD Professional 2014 creating DWG (2010) file formats. All images are externally referenced to the CAD drawing in order to maintain good graphical quality. The CAD plots are effectively georeferenced facilitating relocation of features using GPS, resection method, etc.
2.3.8 An abstraction and interpretation is also drawn and plotted for all geophysical anomalies located by the survey. Anomalies are abstracted using colour coded points, lines and polygons. All plots are scaled to landscape A3 for paper printing.
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2.3.9 A brief summary of each anomaly, with an appropriate reference number, is set out in list form within the results (Section 3) to allow a rapid and objective assessment of features within each survey area. Where further interpretation is possible, or where a number of possible origins should be considered, more subjective discussion is set out in Section 4.
2.3.10 A digital archive is produced with this report, see Appendix D below. The main archive is held at the offices of Archaeological Surveys Ltd.
3 RESULTS
3.1 General assessment of survey results - magnetometry 3.1.1 The detailed magnetic survey was carried out over a total of four survey areas covering approximately 1.85ha.
3.1.2 Magnetic anomalies located can be generally classified as positive and negative anomalies of an uncertain origin, areas of magnetic disturbance, strong discrete dipolar anomalies relating to ferrous objects and strong multiple dipolar linear anomalies relating to buried services or pipelines.
3.1.3 Anomalies located within each survey area have been numbered and are described below with subsequent discussion in Section 4.
3.2 Statement of data quality - magnetometry 3.2.1 Data are considered representative of the magnetic anomalies present within the site. However, widespread magnetic disturbance within Areas 1 - 3 has the potential to obscure anomalies of archaeological potential. In addition, the magnetic contrast of a possible ditch-like feature in Area 4 is very poor, and the soil in this area may not be conducive to the formation of enhanced magnetic susceptibility limiting confidence in the location of features of archaeological potential.
3.3 Data interpretation - magnetometry 3.3.1 The list of sub-headings below attempts to define a number of separate categories that reflect the range and type of features located during the survey. A basic explanation of the characteristics of the magnetic anomalies is set out for each category in order to justify interpretation, a basic key is indicated to allow cross referencing to the abstraction and interpretation plot. CAD layer names are included to aid reference to associated digital files (.dwg/.dxf). Sub-headings are then used to group anomalies with similar characteristics for each survey area.
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Report sub-heading Description and origin of anomalies CAD layer names and plot colour Anomalies with an uncertain origin The category applies to a range of anomalies where there is not enough evidence to confidently suggest an origin . Anomalies in AS-ABST MAG POS LINEAR UNCERTAIN this category may well be related to archaeologically significant AS-ABST MAG NEG LINEAR UNCERTAIN AS-ABST MAG POS DISCRETE UNCERTAIN features, but equally relatively modern features, geological/pedological features and agricultural features should be considered . Positive anomalies are indicative of magnetically enhanced soils that may form the fill of 'cut' features or may be produced by accumulation within layers or 'earthwork' features; soils subject to burning may also produce positive anomalies. Negative anomalies are produced by material of comparatively low magnetic susceptibility such as stone and subsoil. Anomalies associated with magnetic debris Strong discrete dipolar anomalies are responses to ferrous objects within the topsoil.
AS-ABST MAG STRONG DIPOLAR Anomalies with a modern origin The magnetic response is often strong and dipolar indicative of ferrous material and may be associated with extant above surface features such as wire fencing, cables, pylons etc.. Often AS-ABST MAG DISTURBANCE a significant area around such features has a strong magnetic AS-ABST MAG SERVICE flux which may create magnetic disturbance; such disturbance can effectively obscure low magnitude anomalies if they are present. Fluxgate sensors may respond erratically and with hysteresis adjacent to strong magnetic sources. Buried services may produce characteristic multiple dipolar anomalies dependant upon their construction.
Table 1: List and description of magnetometry interpretation categories
3.4 General assessment of survey results - resistivity 3.4.1 The earth resistance survey was carried out over a total of four survey areas covering approximately 1.35ha.
3.4.2 Resistive anomalies located can be generally classified as high resistance anomalies associated with possible buried stones, high and low resistance anomalies of uncertain origin, high resistance anomalies associated with land management, high and low resistance anomalies associated with ground disturbance/dumping and anomalies with a modern origin. Anomalies located within each survey area have been numbered and will be outlined below with subsequent discussion in Section 4.
3.5 Statement of data quality - resistivity 3.5.1 Data are considered representative of the resistive anomalies present within the site. Resistive contrast appears useful with the location of both high and low resistance anomalies of anthropogenic origin. However, the underlying geology and soil has created a variable response that may complicate the abstraction and interpretation of features.
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3.6 Data interpretation - resistivity 3.6.1 The listing of sub-headings below attempts to define a number of separate categories that reflect the range and type of features located during the earth resistance survey. A basic explanation of the characteristics of the anomalies is set out for each category in order to justify interpretation, a basic key is indicated to allow cross reference to the abstraction and interpretation plot. Sub-headings are then used to group anomalies with similar characteristics for each survey area.
Report sub-heading Description and origin of anomalies CAD layer names and plot colour High resistance may indicate structural material (e.g. stone); low Anomalies with archaeological potential resistance may relate to the moisture retentive fill of cut features.
AS-ABST RES HIGH DISCRETE ARCHAEOLOGY Anomalies with an uncertain origin The category applies to a range of anomalies where there is not enough evidence to confidently suggest an origin . Anomalies in AS-ABST RES HIGH LINEAR UNCERTAIN this category may well be related to archaeologically significant AS-ABST RES LOW LINEAR UNCERTAIN AS-ABST RES HIGH DISCRETE UNCERTAIN features, but equally relatively modern features, AS-ABST RES LOW DISCRETE UNCERTAIN geological/pedological features and agricultural features should AS-ABST RES HIGH AREA UNCERTAIN be considered . High resistance anomalies are indicative of AS-ABST RES LOW AREA UNCERTAIN comparatively low moisture and may indicate stone, compacted soil, changes in drainage, etc. Low resistance anomalies are indicative of comparatively high moisture and may relate to the fill of cut features, organic material within the soil, damp areas etc.. Anomalies relating to land management Anomalies are mainly linear and may relate to low resistance cut features (i.e. ditches) or high resistance features such as banks. AS-ABST HIGH RES BANK/BOUNDARY The anomalies may be long and/or form rectilinear elements and they may relate to topographic features or be visible on early mapping. Associated agricultural anomalies (e.g. headlands, plough marks and former ridge and furrow) may support the interpretation. Anomalies associated with ground disturbance Anomalies associated with quarrying and infilled depressions may be a low resistance response. It may also have associated AS-ABST HIGH RES DISURBANCE/TREE ROOTS high resistance anomalies, possibly indicating bands of rock near AS-ABST LOW RES DISTURBANC/DUMPING the surface. High resistance responses can be associated with dumped material and also tree roots. Low resistance responses may also indicate dumped material with a high moisture content. Anomalies with a natural origin The anomalies may be high, low or variable. Low resistance linear anomalies may relate to the infilled cut of a service trench, AS-ABST RES SERVICE or to the highly conductive properties of the service. Anomalies AS-ABST RES PATH relating to existing paths and tracks can be high or low resistance anomalies and relate to visible or mapped paths.
Table 2: List and description of resistivity interpretation categories
3.7 List of anomalies – magnetometry Area 1
Area centred on OS NGR 411623 168092, see Figs 03, 04, 08 & 09.
3.7.1 Area 1 contains magnetic disturbance and strong discrete dipolar responses which relate to ferrous and other magnetically thermoremnant objects. No weaker anomalies are visible.
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3.8 List of anomalies – magnetometry Area 2
Area centred on OS NGR 411580168103, see Figs 03, 04, 08 & 09.
3.8.1 Area 2 is a very small patch of lawn which is surrounded to the north and west by trees and contains a septic tank. Although a number of discrete positive responses can be seen, they are generally over 30nT and lie within a zone of magnetic disturbance and strong discrete dipolar anomalies; a modern origin is likely.
3.9 List of anomalies – magnetometry Area 3
Area centred on OS NGR 411670 168045, see Figs 03, 04, 08 & 09.
Anomalies with an uncertain origin
(1) - A number of discrete positive responses are located at the eastern end of the survey area. They are situated on the higher ground, but close to the Sanctuary. Some are circular, but most are elongated or more amorphous. Several correspond to low resistance discrete responses. It is possible that they relate to naturally formed pit-like features within the underlying chalk; however, they may relate to single, conjoined or recut pits with an archaeological origin.
(2 & 3) - Towards the western end of the survey area are two groups with positive and negative linear anomalies and several discrete responses. They are very weak and poorly defined and they lack a coherent morphology preventing interpretation.
Anomalies with a modern origin
(4) - The northern part of the survey area contains three buried pipelines with a short section of a fourth appearing to link between two of them. Unless they diverge abruptly at the eastern edge of the site, it appears that they enter the scheduled area of the Sanctuary. The strength of the responses is so strong, that there is widespread magnetic disturbance along the northern part of the survey area which may have obscured weaker anomalies. At least one oil pipeline was constructed during 1942, but it appears that at least two others have also been constructed.
(5) - Magnetic disturbance and strong dipolar responses are associated with the metal ties of a former electricity pole.
3.10 List of anomalies – magnetometry Area 4
Area centred on OS NGR 411447 168186, see Figs 03, 04, 08 & 10.
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Anomalies with an uncertain origin
(6) - A small number of, discrete, positive responses are located in the survey area. There are also widespread strong discrete dipolar responses, and it is difficult to determine if these relate to cut, pit-like features, or if they also relate to magnetically thermoremnant material.
(7) - Very weakly positive linear anomalies can be seen, but they are so indistinct that their origin cannot be determined.
3.11 List of ano malies – resistivity Area 1
Area centred on OS NGR 411623 168092, see Figs 05 - 08 & 11.
Anomalies with an uncertain origin
(8) - A low resistance linear anomaly extends through the survey area. It is not clear if it continues into Area 3 to the south east, but it may have an association with anomaly (20) and possibly (21). There is no corresponding magnetometer anomaly, and it is not clear if it relates to a ditch-like feature or possibly a service.
(9 & 10) - Low resistance linear responses of uncertain origin that may indicate ditch-like features.
(11) - Discrete high resistance response is located close to the edge of the survey area. Its origin is uncertain.
(12) - Along the margins of the survey area are zones of high resistance. These relate to ground make up and tree roots or drier areas at the edge of the garden.
3.12 List of ano malies – resistivity Area 2
Area centred on OS NGR 411580 168103, see Figs 05 - 08 & 11.
Anomalies with an uncertain origin
(13) - A discrete high resistance response can be seen in the survey area. While this type of response could relate to a buried stone, it lies adjacent to a garden border bounded by sarsen stones and may be or relatively recent origin.
(14) - A high resistance anomaly in the north western corner of the lawn has been caused by dry ground adjacent to a tree.
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3.13 List of ano malies – resistivity Area 3
Area centred on OS NGR 411670 168045 see Figs 05 - 08 & 11.
Anomalies with an uncertain origin
(15) - The far eastern part of the survey area contains a number of discrete low resistance responses. Many of them correspond to discrete positive responses seen in the magnetometer data and they appear to relate to pit-like features.
(16) - Several discrete high resistance responses can also be seen in the eastern part of the survey area. It is not possible to determine their origin.
(17) - A low resistance curvilinear response is located in the south eastern corner of the survey area. The response could suggest a curvilinear ditch-like feature, but this not certain.
(18) - A high resistance response, with an adjacent low resistance response, appears to be truncated by at least one pipeline (23).
(19) - High resistance linear and curvilinear responses are situated to the west of anomaly (18). It is possible that there has been some truncation by pipeline (24), but the origin of the anomaly or anomalies is uncertain.
(20) - Low resistance responses that appear to have some association with pipeline (24) but also possibly anomalies (8) and (10) in Area 1.
(21) - A low resistance linear anomaly does not extend along the line of a pipeline response as seen in the magnetometer results; however, it could still relate to a service that is not visible magnetically. The west north west to east south east orientation of the first part of (21) could be a continuation of anomalies (8) or (10), although it then appears to extend abruptly towards the north east.
(22) - Low resistance linear response is located just to the south of the highly magnetic response to a buried pipeline. The response is likely to be associated, with (24).
Anomalies with a modern origin
(23 & 24) - Low resistance linear anomalies relate to buried pipelines with corresponding responses in the magnetometer data.
(25) - A low resistance linear anomaly is a response to the footpath that extends through the survey area. The response is very similar to those associated with the pipelines, but no corresponding response can be seen in the magnetometry.
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3.14 List of ano malies – resistivity Area 4
Area centred on OS NGR 411447 168186 see Figs 05 - 08 & 12.
Anomalies with an archaeological origin
(26) - A discrete high resistance anomaly at the northern edge of the field appears to relate to a buried stone. It is in the approximate position of stone 86b, outlined by OGS Crawford and as a 'fallen stone not visible' by Isobel Smith.
Anomalies with an uncertain origin
(27) - To the south of anomaly (26) are five discrete high resistance responses, formed by two responses parallel with the A4 and a line of three responses further to the south west. The responses may relate to buried stones.
(28) - A zone of low resistance corresponds to a nettle covered low mound within the field. It probably relates to dumped material, possibly manure or soil, and there is no corresponding magnetic response to indicate that ferrous or magnetically thermoremnant material is incorporated. Immediately to the east is the position of a fallen sarsen stone, indicated on Ordnance Survey mapping.
Anomalies associated with land management
(29) - Two high resistance linear anomalies correspond to low banks within the field and so are likely to relate to former land boundary features.
Anomalies with a modern origin
(30) - A low resistance linear anomaly relates to a mown footpath that extends within the western part of the survey area.
4 DISCUSSION
4.1.1 The survey areas within the garden of Sarsen Kennels (Areas 1 & 2) did not reveal anything that can be confidently interpreted as archaeological within the magnetometer data. This is mainly due to magnetic debris and disturbance. The earth resistance survey did reveal a number of low resistance linear anomalies within Area 1, one of which appears to relate to a linear mark seen on Google Earth aerial photographs. The origin of the responses is uncertain as although they may extend eastwards, the morphology of the response is not clear in Area 3. A ditch-like feature is possible, and it is parallel with the A4 18m to the north; however, a pipe or service is also possible. Discrete high resistance responses have been located, that would be typically expected for buried stones, but these are within areas that have been subject to modern
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disturbance, and it is not possible to offer a confident interpretation. There is no clear corresponding response in the geophysical survey results to the positions of the stones indicated by OGS Crawford either within the gardens or within Area 3, see below for further discussion.
4.1.2 Any comparison of the stone positions indicated by Crawford and transposed by Steve Marshall (see 1.4.1) is likely to be very misleading for a number of reasons. Archaeological Surveys Ltd has no indication of map accuracy or potential errors in position related to scaling and ground measurement. In addition, Crawford's marked up OS map presumably relates to a pre OSGB36 datum that has been manipulated onto the WGS84 datum used by Google Earth. Archaeological Surveys has then reprojected this back to OSGB36 using MapInfo Professional GIS. The potential errors involved could be very significant. Additionally, Crawford's notes indicate that the former position of stones in the vicinity of Sarsen Kennels and the Sanctuary was recognised by discoloured soil which may also be very misleading. The position of stones has, therefore, not been combined with the geophysical data due to the very low level of confidence in both their recognition in the field and the subsequent mapping.
4.1.3 Area 3 lies on land to the east and south of Sarsen Kennels and extends towards the Sanctuary. Both techniques revealed a number of corresponding pit-like responses towards the eastern end, on the higher ground of Overton Hill. Although some appear circular, others are elongated or oval in shape, possibly suggesting conjoined pits, with dimensions of 2.5m by 1.8m and up to 4.5m by 3m. A number of similar pit-like responses have also been recorded during a previous geophysical survey on land immediately to the north of the A4 (Archaeological Surveys, 2008). It is possible that the responses relate to naturally formed pits or pits that formerly contained naturally occurring sarsens. Cunnington (1931) did locate sarsen fragments with evidence of burning in the post holes, and suggested that the hill was covered with sarsens that had been broken up with fire and cleared. A small number of discrete high resistance responses have also been located.
4.1.4 It is of note that a geophysical survey carried out by Archaeological Surveys (2014) on similar geology a short distance to the south, on a chalk spur immediately east of East Kennett long barrow, did not locate similar discrete anomalies in either the magnetometry or resistivity data. Small sarsen fragments were also noted on this site. It seems unlikely that the underlying geological conditions adjacent to the Sanctuary would vary significantly, the inference being, therefore, that the discrete responses located are potentially of archaeological significance.
4.1.5 Although OGS Crawford indicates that the line of the West Kennet Avenue extends well into Area 3, Cunnington's plan indicates lines of stone attributed to the Avenue extending from the north west quadrant of the outer stone circle, in a north westerly direction, rather than further south into the field. A sketch map by Aubury, does show pairs of stones extending to the north west, but then extending in a more westerly direction (Cunnington, 1931, Plate IV).
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4.1.6 Both techniques have located anomalies associated with at least three pipelines in the northern part of Area 3, with the magnetometry indicating that they are constructed of steel, and that they may extend into the northern part of the Sanctuary. The resistivity results are less clear, with the responses less straight, which may indicate that there are other non-magnetic services or pipes also within the survey area. An electricity cable was buried in 2008, but there is no definite response to this.
4.1.7 Area 4 contains a high resistance response (26), within the vicinity of a buried stone, indicated on Isobel Smith's map as 'stone fallen, not visible' and Crawford's map as 86b, stone inferred from soil. The response does indicate a buried stone and an association with the Avenue is likely. Located to the south west of this are five discrete high resistance responses, formed by two responses 11.5m apart, with the westernmost anomaly 5m south west of anomaly (26) and also a line of three responses 11.8m further south and spaced 2m apart. The responses range from 2m by 1.5m to 2.5m by 2m, and they may relate to buried stones, although it is not possible to determine if they have any association with anomaly (26) or the line of the West Kennet Avenue as they are much more closely spaced than any stones recorded in the Avenue. High resistance linear anomalies relate to extant banks within the field, and although no field boundary is indicated on any Ordnance Survey mapping, a field boundary is indicated in Stukeley's sketch map of 1724. There are no magnetic anomalies that correspond to any of the resistivity responses within Area 4.
5 CONCLUSION
5.1.1 The geophysical survey comprised earth resistance and magnetometry within four survey areas, Areas 1 and 2 in the garden of Sarsen Kennels, Area 3 in the field to the south and east and Area 4 in the field to the west. The results of the earth resistance survey indicate the presence of a buried stone in Area 4 which is likely to be related to a stone previously mapped as number 86b within the West Kennet Avenue. Also within this field, parallel to the line of the A4 and the Avenue are a further five high resistance responses in a line of two and a line of three. It is not possible to determine if they are associated with the Avenue; however, an archaeological origin is possible.
5.1.2 Within Area 3 in the eastern part of the site a number of discrete low resistance responses correspond to discrete positive responses and indicate the presence of pit-like features. They are often oval or elongated, possibly indicating conjoined pits. Although a natural origin is possible, the archaeological potential of these pits, immediately west of the Sanctuary should be considered. In the northern part of the survey area, widespread magnetic disturbance from at least three buried pipelines may have obscured weaker magnetic anomalies, and the earth resistance results may indicate
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that there is some complexity to the trench cuts of the pipelines. The results also indicate that unless the pipelines veer abruptly northwards to the east of the survey area, it is highly likely that they pass through the northern edge of the Sanctuary.
5.1.3 Within the garden of Sarsen Kennels, modern disturbance in the form of buildings, ground make up and vegetation have all produced responses in both the magnetic and resistivity data. A discrete high resistance response in a small area of lawn could be inferred to be close to the position of one of OGS Crawford's stones/pits; however, a modern origin cannot be discounted. Within a larger area of lawn, low resistance responses could indicate ditch-like features, although garden features or possible services could also produce such responses and it is not possible to determine the origin of any of the anomalies within the garden.
6 REFERENCES
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Archaeological Surveys, 2008. Overton Hill, Avebury, Wiltshire, Magnetometer Survey Report. Ref 250. Unpublished typescript document.
Archaeological Surveys, 2014. East Kennett Manor Farm, East Kennett, Wiltshire, Magnetometer Survey Report. Ref 536. Unpublished typescript document.
Archaeological Surveys, 2016. Sarsen Kennels, West Kennett, Avebury, Wiltshire, Geophysical Survey Written Scheme of Investigation. Unpublished typescript document.
Aspinall, A., Gaffney, C. and Schmidt, A., 2009. Magnetometry for Archaeologists . Lanham (US), AltaMira Press.
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Cunnington, M. E., 1931. The 'Sanctuary' on Overton Hill, near Avebury. Wiltshire Archaeological & Natural History Magazine, vol. 45, pp 300-335.
David, A., Martin, L., and Payne, A., 1999. Beckhampton, nr. Avebury, Wilts,
20 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
Draft Report on Geophysical Survey May 1999. Unpublished typescript report. Ancient Monuments Laboratory, English Heritage.
English Heritage, 2008. Geophysical survey in archaeological field evaluation. Research and Professional Service Guideline No.1. 2nd ed. Swindon: English Heritage.
European Archaeological Council, 2015. EAC Guidelines for the Use of Geophysics in Archaeology: Questions to Ask and Points to Consider. Europae Archaeologia Consilium and Association Internationale sans But Lucratif, Belgium.
Gillings, M., Pollard, J. and Wheatley, D., 2000. The Beckhampton Avenue and a 'new' Neolithis enclosure near Avebury: an interim report on the 1999 excavations. Wiltshire Archaeological & Natural History Magazine, vol. 93, pp 1-8.
Institute for Archaeologists, 2002. The use of Geophysical Techniques in Archaeological Evaluations . IfA Paper No. 6. IfA, University of Reading.
Marshall, S., 2016a. Exploring Avebury: The Essential Guide. The History Press.
Marshall, S., 2016b. Exploring Avebury: The Essential Guide [online] available from http://exploringavebury.com/book-notes-91-100 [accessed 9/9/2016].
MOD, 2011. Legislation to enable the sale of the Government Pipeline Storage System. Ministry of Defence UK.
Pitts, M., 2001. Excavating the Sanctuary: New Investigations on Overton Hill, Avebury. Wiltshire Archaeological & Natural History Magazine, vol. 94, pp 1- 23.
Soil Survey of England and Wales, 1983. Soils of England and Wales, Sheet 5 South West England.
21 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
Appendix A – basic principles of magnetic survey
Iron minerals are always present to some degree within the topsoil and enhancement associated with human activity is related to increases in the level of magnetic susceptibility and thermoremnant material.
Magnetic susceptibility is an induced magnetism within a material when it is in the presence of a magnetic field. This can be thought of as effectively permanent due to the presence of the Earth's magnetic field.
Thermoremnant magnetism occurs when ferrous material is heated beyond a specific temperature known as the Curie Point. Demagnetisation occurs at this temperature with re-magnetisation by the Earth's magnetic field upon cooling.
Enhancement of magnetic susceptibility can occur in areas subject to burning and complex fermentation processes on biological material; these are frequently associated with human settlement. Thermoremnant features include ovens, hearths, and kilns. In addition thermoremnant material such as tile and brick may also be associated with human activity and settlement.
Silting and deliberate infilling of ditches and pits with magnetically enhanced soil can create an area of enhancement compared with surrounding soils and subsoils into which the feature is cut. Mapping enhanced areas will produce linear and discrete anomalies allowing an assessment and characterisation of hidden subsurface features.
It should be noted that areas of negative enhancement can be produced from material having lower magnetic properties compared to the topsoil. This is common for many sedimentary bedrocks and subsoils which were often used in the construction of banks and walls etc. Mapping these 'negative' anomalies may also reveal archaeological features.
Magnetic survey or magnetometry can be carried out using a fluxgate gradiometer and may be referred to as gradiometry. The gradiometer is a passive instrument consisting of two fluxgate sensors mounted vertically 1m apart. The instrument is carried about 30cm above the ground surface and the upper sensor measures the Earth's magnetic field as does the lower sensor but this is influenced to a greater degree by any localised buried field. The difference between the two sensors will relate to the strength the magnetic field created by the buried feature. If no enhanced feature is present the field measured by both sensors will be similar and the difference close to zero.
There are a number of factors that may affect the magnetic survey and these include soil type, local geology and previous human activity. Situations arise where magnetic disturbance associated with modern services, metal fencing, dumped waste material etc., obscures low magnitude fields associated with archaeological features.
22 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
Appendix B – data processing notes Clipping Minimum and maximum values are set and replace data outside of the range with those values. Extreme values are removed improving colour or greyscale contrast associated with data values that may be archaeologically significant. It has been found that clipping data to ranges between ±15nT and ±10nT often improves the appearance of features associated with archaeology. Different ranges are applied to data in order to determine the most suitable for anomaly abstraction and display. Zero Median/Mean Traverse The median (or mean) of each traverse is calculated ignoring data outside a threshold value, the median (or mean) is then subtracted from the traverse. The process is used to equalise slight differences between the set-up and stability of gradiometer sensors and can remove striping. The process can remove archaeological features that run along a traverse so data analysis is also carried out prior its application. High Pass Filtering A mathematical process used to remove low frequency anomalies relating to survey tracks and modern agricultural features.
Appendix C – survey and data information
Area 1 raw resistance Instrument Type: Resist. (RM85P) Sensors: 4 Filename: J688-res-Area1.xcp Units: ohm Dummy Value: 2047.5 Description: Imported as Composite from Comments: Source Timestamp: 16/11/2016 Dimensions GeoPlot : J688-res-Area1 19:17:38 Composite Size (readings): 480 x 240 Instrument Type: Resist. (RM85P) Collection Method: Zig-zag Survey Size (meters): 240 m x 120 m Units: ohm Sensors: 4 Grid Size: 30 m x 30 m Comments: Source Timestamp: 16/11/2016 Dummy Value: 2047.5 X Interval: 0.5 m 19:15:22 Dimensions Y Interval: 0.5 m Collection Method: Zig-zag Composite Size (readings): 60 x 60 Stats Sensors: 4 Survey Size (meters): 30 m x 30 m Max: 204.70 Dummy Value: 2047.5 Grid Size: 30 m x 30 m Min: -32.65 Dimensions X Interval: 0.5 m Std Dev: 11.23 Composite Size (readings): 120 x 120 Y Interval: 0.5 m Mean: 34.28 Survey Size (meters): 60 m x 60 m Stats Median: 29.45 Grid Size: 30 m x 30 m Max: 51.00 Composite Area: 2.88 ha X Interval: 0.5 m Min: 18.20 Surveyed Area: 0.79523 ha Y Interval: 0.5 m Std Dev: 4.83 Processes: 1 Stats Mean: 27.92 1 Base Layer Max: 73.10 Median: 27.23 Min: 9.10 Composite Area: 0.09 ha Area 3 processed resistance Std Dev: 6.34 Surveyed Area: 0.02315 ha Mean: 27.40 Processes: 1 Filename: J688-res-Area3-proc.xcp Median: 26.00 1 Base Layer Description: Imported as Composite from Composite Area: 0.36 ha GeoPlot : J688-res-Area3 Surveyed Area: 0.1024 ha Area 2 processed resistance Instrument Type: Resist. (RM85P) Processes: 1 Units: ohm 1 Base Layer Filename: J688-res-Area2-proc.xcp Comments: Source Timestamp: 29/11/2016 Description: Imported as Composite from 17:11:40 Area 1 processed resistance GeoPlot : J688-res-Area2 Collection Method: Zig-zag Instrument Type: Resist. (RM85P) Sensors: 4 Filename: J688-res-Area1-proc.xcp Units: ohm Dummy Value: 2047.5 Description: Imported as Composite from Comments: Source Timestamp: 16/11/2016 Dimensions GeoPlot : J688-res-Area1 19:17:38 Composite Size (readings): 480 x 240 Instrument Type: Resist. (RM85P) Collection Method: Zig-zag Survey Size (meters): 240 m x 120 m Units: ohm Sensors: 4 Grid Size: 30 m x 30 m Comments: Source Timestamp: 16/11/2016 Dummy Value: 2047.5 X Interval: 0.5 m 19:15:22 Y Interval: 0.5 m Collection Method: Zig-zag Dimensions Stats Sensors: 4 Composite Size (readings): 60 x 60 Max: 64.00 Dummy Value: 2047.5 Survey Size (meters): 30 m x 30 m Min: 20.00 Dimensions Grid Size: 30 m x 30 m Std Dev: 10.04 Composite Size (readings): 120 x 120 X Interval: 0.5 m Mean: 33.92 Survey Size (meters): 60 m x 60 m Y Interval: 0.5 m Median: 29.25 Grid Size: 30 m x 30 m Stats Composite Area: 2.88 ha X Interval: 0.5 m Max: 51.00 Surveyed Area: 0.79523 ha Y Interval: 0.5 m Min: 18.20 Processes: 3 Stats Std Dev: 4.83 1 Base Layer Max: 33.00 Mean: 27.92 2 Clip from 20.00 to 64.00 ohm Min: 19.00 Median: 27.23 3 Despike Threshold: 1 Window size: 5x5 Std Dev: 3.91 Composite Area: 0.09 ha Mean: 26.47 Surveyed Area: 0.02315 ha Area 3 filtered resistance Median: 26.00 Processes: 1 Composite Area: 0.36 ha 1 Base Layer Filename: J688-res-Area3-proc-despike-hpf.xcp Surveyed Area: 0.1024 ha Description: Imported as Composite from Processes: 2 Area 3 raw resistance GeoPlot : J688-res-Area3 1 Base Layer Instrument Type: Resist. (RM85P) 2 Clip from 19.00 to 33.00 ohm Filename: J688-res-Area3.xcp Units: ohm Description: Imported as Composite from Comments: Source Timestamp: 29/11/2016 GeoPlot : J688-res-Area3 17:11:40 Area 2 raw resistance Instrument Type: Resist. (RM85P) Collection Method: Zig-zag Units: ohm Sensors: 4 Filename: J688-res-Area2.xcp Comments: Source Timestamp: 29/11/2016 Dummy Value: 2047.5 Description: Imported as Composite from 17:11:40 Dimensions GeoPlot : J688-res-Area2 Collection Method: Zig-zag Composite Size (readings): 480 x 240
23 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
Survey Size (meters): 240 m x 120 m Area 1 magnetometry Area 3 magnetometry Grid Size: 30 m x 30 m X Interval: 0.5 m Filename: J688-mag-Area1-proc.xcp Filename: J688-mag-Area3-proc-hpf.xcp Y Interval: 0.5 m Description: Imported as Composite from: J688- Description: Imported as Composite from: J688- Stats mag-Area1.asc mag-Area3.asc Max: 8.00 Instrument Type: Sensys DLMGPS Instrument Type: Sensys DLMGPS Min: -6.00 Units: nT Units: nT Std Dev: 2.02 UTM Zone: 30U UTM Zone: 30U Mean: 0.04 Survey corner coordinates (X/Y):OSGB36 Survey corner coordinates (X/Y):OSGB36 Median: 0.09 Northwest corner: 411589.768928711, Northwest corner: 411520.72853882, Composite Area: 2.88 ha 168102.673733769 m 168078.963444038 m Surveyed Area: 0.79523 ha Southeast corner: 411657.418928711, Southeast corner: 411815.32853882, Processes: 4 168080.773733769 m 168000.213444038 m 1 Base Layer Collection Method: Randomised Collection Method: Randomised 2 Despike Threshold: 1 Window size: 5x5 Sensors: 1 Sensors: 1 3 High pass Uniform (mean) filter: Window: 31 x 31 Dummy Value: 32702 Dummy Value: 32702 4 Clip from -6.00 to 8.00 ohm Source GPS Points: 29600 Source GPS Points: 526700 Dimensions Dimensions Area 4 raw resistance Composite Size (readings): 451 x 146 Composite Size (readings): 1964 x 525 Survey Size (meters): 67.7 m x 21.9 m Survey Size (meters): 295 m x 78.8 m Filename: J688-res-Area4.xcp Grid Size: 67.7 m x 21.9 m Grid Size: 295 m x 78.8 m Description: Imported as Composite from X Interval: 0.15 m X Interval: 0.15 m GeoPlot : J688-res-Area4 Y Interval: 0.15 m Y Interval: 0.15 m Instrument Type: Resist. (RM85P) Stats Stats Units: ohm Max: 5.53 Max: 5.53 Comments: Source Timestamp: 23/11/2016 Min: -5.50 Min: -5.50 13:22:38 Std Dev: 3.02 Std Dev: 3.10 Collection Method: Zig-zag Mean: -0.05 Mean: 0.08 Sensors: 4 Median: -0.05 Median: 0.01 Dummy Value: 2047.5 Composite Area: 0.14815 ha Composite Area: 2.32 ha Dimensions Surveyed Area: 0.097803 ha Surveyed Area: 1.3506 ha Composite Size (readings): 300 x 60 Processes: 1 Processes: 1 Survey Size (meters): 150 m x 30 m 1 Base Layer 1 Base Layer Grid Size: 30 m x 30 m GPS based Proce5 GPS based Proce5 X Interval: 0.5 m 1 Base Layer. 1 Base Layer. Y Interval: 0.5 m 2 Unit Conversion Layer (Lat/Long to OSGB36). 2 Unit Conversion Layer (Lat/Long to OSGB36). Stats 3 DeStripe Median Traverse: 3 DeStripe Median Traverse: Max: 35.05 4 High pass Uniform (median) filter: Window dia: 200 4 High pass Uniform (median) filter: Window dia: 300 Min: 8.79 5 Clip from -5.00 to 5.00 nT 5 Clip from -5.00 to 5.00 nT Std Dev: 2.95 Mean: 21.82 Area 2 magnetometry Area 4 magnetometry Median: 21.85 Composite Area: 0.45 ha Filename: J688-mag-Area2-proc.xcp Filename: J688-mag-Area4-proc.xcp Surveyed Area: 0.3489 ha Description: Imported as Composite from: J688- Description: Imported as Composite from: J688- Processes: 2 mag-Area2.asc mag-Area4.asc 1 Base Layer Instrument Type: Sensys DLMGPS Instrument Type: Sensys DLMGPS 2 Clip at 3.00 SD Units: nT Units: nT UTM Zone: 30U UTM Zone: 30U Area 4 processed resistance Survey corner coordinates (X/Y):OSGB36 Survey corner coordinates (X/Y): OSGB36 Northwest corner: 411573.091952407, Northwest corner: 411386.717458497, Filename: J688-res-Area4-proc.xcp 168113.662152442 m 168254.563584898 m Description: Imported as Composite from Southeast corner: 411590.791952407, Southeast corner: 411510.167458497, GeoPlot : J688-res-Area4 168092.362152442 m 168123.013584898 m Instrument Type: Resist. (RM85P) Collection Method: Randomised Collection Method: Randomised Units: ohm Sensors: 1 Sensors: 1 Comments: Source Timestamp: 23/11/2016 Dummy Value: 32702 Dummy Value: 32702 13:22:38 Source GPS Points: 7100 Source GPS Points: 118700 Collection Method: Zig-Zag Dimensions Dimensions Sensors: 4 Composite Size (readings): 118 x 142 Composite Size (readings): 823 x 877 Dummy Value: 2047.5 Survey Size (meters): 17.7 m x 21.3 m Survey Size (meters): 123 m x 132 m Dimensions Grid Size: 17.7 m x 21.3 m Grid Size: 123 m x 132 m Composite Size (readings): 300 x 60 X Interval: 0.15 m X Interval: 0.15 m Survey Size (meters): 150 m x 30 m Y Interval: 0.15 m Y Interval: 0.15 m Grid Size: 30 m x 30 m Stats Stats X Interval: 0.5 m Max: 11.05 Max: 5.53 Y Interval: 0.5 m Min: -11.00 Min: -5.50 Stats Std Dev: 7.13 Std Dev: 1.91 Max: 29.00 Mean: 0.67 Mean: 0.01 Min: 15.00 Median: 0.40 Median: 0.01 Std Dev: 2.71 Composite Area: 0.037701 ha Composite Area: 1.624 ha Mean: 21.75 Surveyed Area: 0.020916 ha Surveyed Area: 0.39683 ha Median: 21.83 Processes: 1 Processes: 1 Composite Area: 0.45 ha 1 Base Layer 1 Base Layer Surveyed Area: 0.3489 ha GPS based Proce4 GPS based Proce4 Processes: 3 1 Base Layer. 1 Base Layer. 1 Base Layer 2 Unit Conversion Layer (Lat/Long to OSGB36). 2 Unit Conversion Layer (Lat/Long to OSGB36). 2 Clip from 15.00 to 29.00 ohm 3 DeStripe Median Traverse: 3 DeStripe Median Traverse: 3 Despike Threshold: 1 Window size: 3x3 4 Clip from -10.00 to 10.00 nT 4 Clip from -5.00 to 5.00 nT
24 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
Appendix D – digital archive
Archaeological Surveys Ltd hold the primary digital archive at their offices in Wiltshire. Data are backed-up onto an on-site data storage drive and at the earliest opportunity data are copied to CD ROM for storage on-site and off-site. .
A printed copy of the report and a PDF copy will be supplied to the Wiltshire Historic Environment Record. Copies of the report with the data will also be sent to Dr Nicola Snashall, National Trust archaeologist and reports issued to Historic England southwest team in Bristol and Paul Linford at Fort Cumberland. The report will also be uploaded to the Online AccesS to the Index of archaeological investigationS (OASIS).
Geophysical data magnetometry - path: J688\Sarsen Kennels\Data\
Path and Filename Software Description Date Creator
Mag\sarsen1\MX\.prm,.dgb,.disp Sensys MXPDA Proprietary data formats representing magnetometer survey D.J.Sabin Mag\sarsen2\MX\.prm,.dgb,.disp traverses logged to a PDA. Mag\sarsen2\MX\.prm,.dgb,.disp Mag\sarsen2\MX\.prm,.dgb,.disp
Mag\sarsen1\MX\J688-mag-Area3.asc Sensys DLMGPS ASCII CSV (tab) file representing survey area in eastings, 28/11/16 D.J.Sabin Mag\sarsen2\MX\J688-mag-Area4.asc northings (UTM Z30N), magnetic measurement, traverse file and 24/11/16 Mag\sarsen3\MX\J688-mag-Area2.asc sensor number. 24/11/16 Mag\sarsen4\MX\J688-mag-Area1.asc 28/11/16
Mag\Area1\comps\J688-mag-Area1.xcp TerraSurveyor Composite data file derived from ASCII CSV. 28/11/16 D.J.Sabin Mag\Area2\comps\J688-mag-Area2.xcp 3.0.23.0 24/11/16 Mag\Area3\comps\J688-mag-Area3.xcp 24/11/16 Mag\Area4\comps\J688-mag-Area4.xcp 28/11/16
Mag\Area1\comps\J688-mag-Area1-proc.xcp TerraSurveyor Processed composite data file (zmt and clipping to ±5nT for Areas 28/11/16 D.J.Sabin Mag\Area2\comps\J688-mag-Area2-proc.xcp 3.0.23.0 1, 3 & 4 and ±10nT for Area 2). 24/11/16 Mag\Area3\comps\J688-mag-Area3-proc.xcp 24/11/16 Mag\Area3\comps\J688-mag-Area3-proc-hpf.xcp 28/11/16 Mag\Area4\comps\J688-mag-Area4-proc.xcp
Geophysical data resistivity - path: J688\Sarsen Kennels\Data\
Res\Area1\comps\J688-res-Area1.xcp TerraSurveyor Composite data file 16/11/16 D.J.Sabin Res\Area2\comps\J688-res-Area2.xcp 3.0.23.0 16/11/16 Res\Area3\comps\J688-res-Area3.xcp 29/11/16 Res\Area4\comps\J688-res-Area4.xcp
Res\Area1\comps\J688-res-Area1-proc.xcp TerraSurveyor Processed composite data file 20/11/16 D.J.Sabin Res\Area2\comps\J688-res-Area2-proc.xcp 3.0.23.0 20/11/16 Res\Area3\comps\J688-res-Area3-proc.xcp 29/11/16 Res\Area3\comps\J688-res-Area3-proc-despike- 29/11/16 hpf.xcp 24/11/16 Res\Area4\comps\J688-res-Area4-proc.xcp
Graphic data - path: J688\Sarsen Kennels\Data\
Mag\Area1\graphics\J688-mag-Area1-proc.tif TerraSurveyor TIF file showing a minimally processed greyscale plot clipped to 28/11/16 K.T.Donaldson Mag\Area1\graphics\J688-mag-Area1-proc-hpf.tif 3.0.23.0 ±5nT. 28/11/16 Mag\Area2\graphics\J688-mag-Area2-proc.tif 24/11/16 Mag\Area3\graphics\J688-mag-Area3-proc-5nT.tif 28/11/16 Mag\Area3\graphics\J688-mag-Area3-proc-hpf-5nT.tif 28/11/16 Mag\Area4\graphics\J688-mag-Area4-proc.tif 24/11/16
Mag\Area1\graphics\J688-mag-Area1-proc.tfw TerraSurveyor World file for georeferencing TIF to OSGB36. 28/11/16 K.T.Donaldson Mag\Area1\graphics\J688-mag-Area1-proc-hpf.tfw 3.0.23.0 28/11/16 Mag\Area2\graphics\J688-mag-Area2-proc.tfw 24/11/16 Mag\Area3\graphics\J688-mag-Area3-proc-5nT.tfw 28/11/16 Mag\Area3\graphics\J688-mag-Area3-proc-hpf-5nT.tfw 28/11/16 Mag\Area4\graphics\J688-mag-Area4-proc.tfw 24/11/16
Res\Area1\graphics\J688-res-Area1-raw.tif TerraSurveyor TIF file showing a raw greyscale plot of survey area 20/11/16 K.T.Donaldson Res\Area2\graphics\J688-res-Area2-raw.tif 3.0.23.0 13/12/16 Res\Area3\graphics\J688-res-Area3-raw.tif 13/12/16 Res\Area4\graphics\J688-res-Area4-raw.tif 13/12/16
Res\Area1\graphics\J688-res-Area1-proc.tif TerraSurveyor TIF file showing a processed greyscale plot of survey area. 20/11/16 K.T.Donaldson Res\Area2\graphics\J688-res-Area2-proc.tif 3.0.23.0 20/11/16 Res\Area3\graphics\J688-res-Area3-proc.tif 20/11/16 Res\Area3\graphics\J688-res-Area3-proc-hpf.tif 29/11/16 Res\Area4\graphics\J688-res-Area4-proc.tif 24/11/16
CAD data - path: J688\Sarsen Kennels CAD\
J688 version 1.dwg ProgeCAD 2014 CAD file for creating plots of greyscales, abstraction, interpretation 29/09/16 K.T.Donaldson and mapping. Grid coordinates as OSGB. AutoCAD 2010 format.
Text data - path: J688\Sarsen Kennels\Documentation\
J688 report.odt OpenOffice.org Report text as an Open Office document. 04/12/16 K.T.Donaldson 3.0.1 Writer
25 Archaeological Surveys Ltd Sarsen Kennels, West Kennett, Avebury, Wiltshire Magnetometry and Resistivity Survey
Appendix E – copyright and intellectual property
This report may contain material that is non-Archaeological Surveys Ltd copyright (eg Ordnance Survey, Crown Copyright) or the intellectual property of third parties, which we are able to provide for limited reproduction under the terms of our own copyright licences, but for which copyright itself is non-transferable by Archaeological Surveys Ltd. Users remain bound by the conditions of the Copyright, Design and Patents Act 1988 with regard to multiple copying and electronic dissemination of this report.
Archaeological Surveys Ltd shall retain intellectual property rights for the materials and records created as part of this project. A non-exclusive, transferable, sub- licensable, perpetual and royalty-free licence shall be granted to the client on full payment of works in order for them to use, reproduce and enhance the reports, documentation, graphics and illustrations produced as part of this project for the purpose for which they were commissioned. Copyright licence will also be granted to the local authority for planning use and within in the Historic Environment Record for public dissemination upon payment by the client. Any document produced to meet planning requirements may be freely copied for planning, development control, research and outreach purposes without recourse to the originator, subject to all due and appropriate acknowledgements being provided and to the terms of the original contract with the client. Archaeological Surveys Ltd shall retain the right to be identified as the author and originator of the material.
The report, data and any associated material produced by Archaeological surveys Ltd cannot be freely used for any commercial activity other than those set out above. Any unauthorised use will be considered to be in breach of copyright.
Late payment may jeopardise any planning decision as there will be no transfer of title, licensing or any other right of copy or use of this report. Archaeological Surveys Ltd do not give permission for use of the report and associated data in cases of late payment. Any such use will be considered to be in breach of copyright. Late payment may also incur interest at 8% over the Bank of England base rate. Non-payment will be pursued by legal action.
26 Historic England Geophysical Survey Database Questionnaire
Survey Details
Name of Site: Sarsen Kennels, West Kennett, Avebury
County: Wiltshire
NGR Grid Reference (Centre of survey to nearest 100m):SU 11592 68094
Start Date: 16th November 2016 End Date: 29th November 2016
Geology at site (Drift and Solid): Chalk (Holywell Nodular Chalk Formation & New Pit Chalk Formation)
Known archaeological Sites/Monuments covered by the survey (Scheduled Monument No. or National Archaeological Record No. if known) West Kennet Avenue and an earthwork bank east of West Kennett Farm . List entry number 1015547.
Archaeological Sites/Monument types detected by survey (Type and Period if known. "?" where any doubt). Stone - Neolithic Pits - uncertain
Surveyor (Organisation, if applicable, otherwise individual responsible for the survey):David Sabin & Kerry Donaldson, Archaeological Surveys Ltd Name of Client, if any: AC Archaeology on behalf of Mr N Baldock
Purpose of Survey: To establish the presence, layout and extent of any buried sarsens or stone settings associated with the West Kennet Avenue with the gardens of Sarsen Kennels and within National Trust land to the east and west.
Location of: a) Primary archive, i.e. raw data, electronic archive etc: Archaeological Surveys Ltd, 1 West Nolands, Nolands Road, Yatesbury, Calne, SN11 8YD b) Full Report: As above with copy to OASIS and HER Technical Details
(Please fill out a separate sheet for each survey technique used)
Type of Survey (Use term from attached list or specify other): Magnetometry
Area Surveyed, if applicable (In hectares to one decimal place): 1.85ha
Traverse Separation, if regular: 0.5m Reading/Sample Interval: 20Hz
Type, Make and model of Instrumentation:
Sensys Magneto MXPDA (multiple fluxgate gradiometers)
Land use at the time of the survey (Use term/terms from the attached list or specify other): Garden - Area 1 & 2 Grassland - Areas 3 & 4 Technical Details
(Please fill out a separate sheet for each survey technique used)
Type of Survey (Use term from attached list or specify other): Earth resistance
Area Surveyed, if applicable (In hectares to one decimal place): 1.35ha
Traverse Separation, if regular: 0.5m Reading/Sample Interval: 0.5
Type, Make and model of Instrumentation:
Geoscan RM85 resistance meter with mobile twin probe array configuration
Land use at the time of the survey (Use term/terms from the attached list or specify other):
Grassland - Areas 1-3 Arable - Area 4 Archaeological Surveys Ltd
N Geophysical Survey Sarsen Kennels West Kennett Wiltshire
Map of survey area
Reproduced from OS Explorer map no.157 1:25 000 by permission of Ordnance Survey on behalf of The Controller of Her Majesty's Stationery Office. © Crown copyright. All rights reserved. Licence number 100043739.
West Kennet Avenue Scheduled Monument boundary
Survey location
Survey location Site centred on OS NGR SU 11592 68094
SCALE 1:25 000
0m 500m 1000m
S CA LE TRUE AT A3
FIG 01 Archaeological Surveys Ltd 411389,17
5
168222,74
4 N Geophysical Survey Sarsen Kennels 3 West Kennett Wiltshire Area 4 2
1 Referencing information 168127,1
S a rs en Kennels 411589,76 168109,66 Area 1 Resistivity survey grid size = 30m S c hedul ed monument boundary 1 411591,52 411504,73
168090,74 2 168088,93 4 Area 2 411650,89 Survey start and traverse direction 1 168080,28 3 168077,4 5 4 6 Grid reference number and filename 411580,6 2 1
411644,67 3 13 12 Position of buried sarsen / pit derived from 11 7 OGS Crawford by Steve Marshall 1 10
9 T h e Sanctuary Survey carried out at 0.5m centres along 0.5m traverses. Survey start at 0.5m in from 411777,47 8 Area 3 168007,7 baseline Grid coordinates based on Ordnance Survey OSGB36 datum. Grids set out using RTK GPS with Leica SmartNet correction data RTCMv2 format OSTN02 transformation 411750 411600 411650 411700 411800 411850 168250 411350 411400 411450 411500 411550 168250
168200 168200 Magnetometry referencing grid to OSGB36 datum at 50m intervals
Data collected at 20Hz and georeferenced to Area 4 ETRS89 zone 30 with conversion to OSGB36 using OSTN02 168150 168150
S a rs en Kennels
Area 1 168100 S c hedul ed monument boundary 168100
Area 2 SCALE 1:2000
0m 20 40 60 80 100m
168050 168050
S CA LE TRUE AT A3
T h e Sanctuary
Ordnanc e Survey © Crown c opyright. 2015. A l l ri ghts res erved. Licence number 100022432. Area 3 168000 168000 FIG 02 411350 411400 411500 411550 411600 411650 411700 411750 411800 411850 411450 Archaeological Surveys Ltd
N Geophysical Survey Sarsen Kennels West Kennett Wiltshire
Greyscale plot of minimally processed magnetometer data
+5nT Area 4 2008 survey area
Sarsen Kennels -5nTArea 1 +5nT -5nT
Area 1 Scheduled monument boundary
Area 2
-5nTArea 3 +5nT -5nTArea 4 +5nT
+10nT
The Sanctuary
Area 3 -10nTArea 2 +10nT -10nT
SCALE 1:1500
0m 10 20 30 40 50m Barrow
S CA LE TRUE AT A3
Ordnanc e Survey © Crown c opyright. 2015. A l l ri ghts res erved. Licence number 100022432.
FIG 03 Archaeological Surveys Ltd
N Geophysical Survey Sarsen Kennels West Kennett Wiltshire
Abstraction and interpretation of 6 magnetometer anomalies 7
Area 4 Positive linear anomaly - possible ditch-like 2008 survey area feature
Negative linear anomaly - material of low magnetic susceptibility
Sarsen Kennels Discrete positive response - possible pit-like feature
Area 1 Magnetic disturbance from ferrous material Scheduled monument boundary
Strong multiple dipolar linear anomaly - Area 2 pipeline / cable / service Strong dipolar anomaly - ferrous object
4
3 2
5 The Sanctuary 1 Area 3
SCALE 1:1500
0m 10 20 30 40 50m Barrow
SCALE TRUE AT A3
Ordnance Survey © Crown copyright. 2015. All rights reserved. Licence number 100022432.
FIG 04 Archaeological Surveys Ltd
N Geophysical Survey Sarsen Kennels West Kennett Wiltshire
Greyscale plot of raw resistance data
73.1 Area 4
9.1 Area 1 73.1 9.1 51 Sarsen Kennels
Area 1 Scheduled monument boundary
Area 2 18.2 Area 2 51 18.2 75
0 Area 3 75 0 35. 05
The Sanctuary
Area 3
8.79 Area 4 35. 05 8. 79 3SD 3SD
SCALE 1:1500
0m 10 20 30 40 50m Barrow
S CA LE TRUE AT A3
Ordnanc e Survey © Crown c opyright. 2015. A l l ri ghts res erved. Licence number 100022432.
FIG 05 Archaeological Surveys Ltd
N Geophysical Survey Sarsen Kennels West Kennett Wiltshire
Greyscale plot of processed resistance data
33 Area 4
19 Area 1 33 19 51 Sarsen Kennels
Area 1 Scheduled monument boundary
Area 2 18.2 Area 2 51 18.2 8
6 Area 3 8 6 29
The Sanctuary
Area 3
15 Area 4 29 15
SCALE 1:1500
0m 10 20 30 40 50m Barrow
S CA LE TRUE AT A3
Ordnanc e Survey © Crown c opyright. 2015. A l l ri ghts res erved. Licence number 100022432.
FIG 06 Archaeological Surveys Ltd
N Geophysical Survey Sarsen Kennels West Kennett
30 Wiltshire
28 26 Abstraction and interpretation of resistance anomalies
27
29 High resistance linear anomaly - of Area 4 uncertain origin Low resistance linear anomaly - of uncertain origin
Low resistance anomaly - pipeline/service
High resistance linear anomaly - extant Sarsen Kennels bank/boundary feature
14 Area 1 Discrete high resistance response - Scheduled monument boundary possible buried sarsen 13 11 12 Discrete high resistance response - of 9 uncertain origin Area 2 8 10 Discrete low resistance response - pit-like 24 20 feature of uncertain origin
19 18 21 22 Area of high resistance - of uncertain origin 23 25 Area of low resistance - of uncertain origin
Area of high resistance - possible made ground/tree roots 16 The Sanctuary 17 15 Area of low resistance - area of dumped material Area 3 Area of low resistance - footpath
SCALE 1:1500
0m 10 20 30 40 50m Barrow
SCALE TRUE AT A3
FIG 07 Archaeological Surveys Ltd
N Geophysical Survey Sarsen Kennels West Kennett Wiltshire
Abstraction and interpretation of resistivity & magnetometer anomalies
High resistance linear anomaly - of uncertain origin
Low resistance linear anomaly - of Area 4 uncertain origin
2008 survey area Low resistance anomaly - pipeline/service
Discrete high resistance response - possible buried sarsen
Sarsen Kennels Discrete high resistance response - of uncertain origin
Area 1 Discrete low resistance response - pit-like Scheduled monument boundary feature of uncertain origin
Area 2 Area of high resistance - of uncertain origin
Area of low resistance - of uncertain origin
Area of high resistance - possible made ground/tree roots
Area of low resistance - area of dumped material
Area of low resistance - footpath The Sanctuary
Positive linear anomaly - possible ditch-like Area 3 feature Negative linear anomaly - material of low magnetic susceptibility
Discrete positive response - possible pit-like feature
Strong multiple dipolar linear anomaly - pipeline / cable / service
Strong dipolar anomaly - ferrous object
SCALE 1:1500 Barrow 0m 10 20 30 40 50m
SCALE TRUE AT A3
Ordnance Survey © Crown copyright. 2015. All rights reserved. Licence number 100022432.
FIG 08 Archaeological Surveys Ltd Sarsen Kennels
Area 1 N Geophysical Survey Sarsen Kennels West Kennett Area 2 Wiltshire
Greyscale plot of filtered magnetometer data - east +5nT
-5nTArea 1 +5nT
-5nT +10nT The Sanctuary -5nTArea 3 +5nT
Area 3
-10nTArea 2 +10nT -10nT
Abstraction and interpretation of
Sarsen Kennels magnetometer anomalies - east
Positive linear anomaly - possible ditch-like feature Area 1 Negative linear anomaly - material of low magnetic susceptibility
Discrete positive response - possible pit-like feature
Area 2 Magnetic disturbance from ferrous material
Strong multiple dipolar linear anomaly - pipeline / cable / service
Strong dipolar anomaly - ferrous object
4
SCALE 1:1000 3 2 0m 10 20 30 40 50m
The Sanctuary 5 SCALE TRUE AT A3 1
Ordnance Survey © Crown copyright. 2015. Area 3 All rights reserved. Licence number 100022432. FIG 09 Archaeological Surveys Ltd Greyscale plot of processed magnetometer data
N Geophysical Survey Sarsen Kennels West Kennett Wiltshire
Greyscale plot of processed magnetometer data - east
+5nT
6
7 -5nT Area 4 +5nT -5nT
Area 4 Area 4
Abstraction and interpretation of magnetometer anomalies - east
Positive linear anomaly - possible ditch-like feature Sarsen Kennels Sarsen Kennels Discrete positive response - possible pit-like feature
Strong dipolar anomaly - ferrous object
Scheduled monument boundary Scheduled monument boundary
SCALE 1:1000
0m 10 20 30 40 50m
SCALE TRUE AT A3 3
Ordnance Survey © Crown copyright. 2015. All rights reserved. Licence number 100022432.
FIG 10 Archaeological Surveys Ltd Sarsen Kennels
Area 1 N Geophysical Survey Sarsen Kennels West Kennett Area 2 Wiltshire
Greyscale plot of processed resistivity data - east
33
19 19 Area 1 33
51
The Sanctuary 18.2 18.2 Area 2 51 8 Area 3
6 Area 3 8 6
Abstraction and interpretation of resistance anomalies - east Sarsen Kennels High resistance linear anomaly of uncertain origin 14 Low resistance linear anomaly of Area 1 uncertain origin Low resistance anomaly pipeline/service 13 11 Discrete high resistance response of 12 uncertain origin 9 Area 2 8 10 Discrete low resistance response pit like feature of uncertain origin
Area of high resistance of uncertain origin 24 20 Area of low resistance of uncertain origin 19 18 Area of high resistance possible made 21 22 ground/tree roots Area of low resistance footpath 23 25 SCALE 1:1000
0m 10 20 30 40 50m
16 The Sanctuary 15 17 SCALE TRUE AT A3
Ordnance Survey © Crown copyright. 2015. Area 3 All rights reserved. Licence number 100022432. FIG 11 Archaeological Surveys Ltd
N Geophysical Survey Sarsen Kennels West Kennett Wiltshire
Greyscale plot of processed resistivity data - west 30 29
28 26
15 Area 4 29 16 27
29 Area 4 Area 4
Abstraction and interpretation of resistance anomalies - west
High resistance linear anomaly extant bank/boundary feature Sarsen Kennels Sarsen Kennels Discrete high resistance response possible buried sarsen
Discrete high resistance response of Scheduled monument boundary Scheduled monument boundary uncertain origin
Discrete low resistance response pit like feature of uncertain origin
Area of low resistance area of dumped material
Area of low resistance footpath
SCALE 1:1000
0m 10 20 30 40 50m
SCALE TRUE AT A3
Ordnance Survey © Crown copyright. 2015. All rights reserved. Licence number 100022432.
FIG 12 APPENDIX 2: SETTING ASSESSMENT SETTING ASSESSMENT
1. INTRODUCTION
1.1 This section considers the current setting of the principal monuments and the potential effects on the setting from the proposed development at the Sarsen Kennels site. The sites individually and together are part of the World Heritage Site and are of the highest historic environment significance in England.
1.2 Reference should be made to the attached photograph that shows the existing setting of the avenue looking west from the Sanctuary.
2. WEST KENNET AVENUE AND AN EARTHWORK BANK EAST OF WEST KENNET FARM
Scheduled Monument (List Entry No. 1015547)
2.1 The significance of the asset is principally derived from its evidential value and it is one of the principal monuments on which the designation of the World Heritage Site was made. Although it does not survive intact, its sinuous path between Avebury henge and the Sanctuary to the southeast can be surmised from the known or surviving elements.
2.2 The current setting of the monument comprises its location within a wider landscape of significant Neolithic and Bronze Age monuments and appears to form a ceremonial link between Avebury henge and the Sanctuary. The group of monuments within the Avebury environs creates a very important ritual and ceremonial landscape. Although little is now known of the nature of the rituals or uses of the monuments, there is no doubt that they are contemporaneous and had functional and associative relationships. The monuments have been protected and an open agricultural landscape largely preserved so these relationships can still be experienced and, to some extent, understood. The topography of the area also allows long views that can incorporate a number of assets in a single vista. In places where the stones survive in situ, the monument is generally fenced off from the agricultural landscape beyond and its route can be easily traced. Footpaths and roads allow easy public access to much of the best-surviving parts of the asset. This openness and accessibility enhances the ability to experience the asset itself and its setting within the wider complex of monuments. Although there are modern intrusions into parts of the landscape, it is considered that there are places where a tranquillity and a sense of remoteness can be achieved.
2.3 The exact nature and function of the Avenue and its associated assets is not fully understood and the level of inter-visibility or designed/intended views is unclear. However, while it is unlikely that there was intended visibility between the stone circles or the barrows, it is considered likely that views along Avenue could have formed part of its ceremonial function. The defining of the Avenue with sarsens would have marked it out as prominent route and it is possible that the ability to view a procession may have formed part of the design. The many artistic representations of the asset have highlighted this aspect, although all are of relatively recent date, drawn when even folk memory of the use of the asset had been lost. Overall, the setting of the Avenue makes a moderate to high contribution to the significance of the asset.
2.4 The existing archaeological and documentary evidence has been examined alongside the results of a geophysical survey undertaken as part of this assessment to try to establish the presence, route and survival of the Avenue within and around the application area. A map of 1884 shows a stone within the application area (not believed to be present now) and further stones (also shown on the 1887 Ordnance Survey map) alongside the current A4 to the north west of the application area. The geophysical survey to the east and west of the application area (Archaeological Surveys, 2016) did not identify conclusive evidence for the presence, or former presence, of stones to the south of the A4. However, recent geophysical surveys undertaken to the north of the road (Archaeological Surveys, 2008 and 2016) found no evidence for the presence of the Avenue in this field either. The location of the Sanctuary, the extant and recorded stones on the south of the A4, and the artistic depictions of the remains of the asset (particularly Stukeley’s in 1723), strongly suggest that the Avenue lies to the south of the road and that the surviving stones represent the northern row. The southern row of stones would therefore lie (based on the spacing between the two lines of stones elsewhere) c. 15m south of that, and pass through the application area.
2.5 Based on this, although the Sarsen Kennels site may not be detrimental to the setting of the asset as a whole, it could be said that its presence on the Avenue restricts the ability to fully appreciate the asset’s route. The proposed redevelopment of the site would include the removal of some existing structures and vegetation which currently restrict views through the site and to the landscape beyond. The vegetation clearance would open up views along and through the current conjectural route of the Avenue allowing, for the first time in many years, an unhindered view along this part of the Avenue from the Sanctuary. It would also allow a clearer view toward the Sanctuary from the northwest as one drives east along the A4.
2.6 It is considered that restoring this visual aspect of the setting would allow a better appreciation of the length and route of the asset and a better understanding of the contribution it makes to the monumental landscape of which it forms a part. This would constitute an enhancement of the setting of the Avenue. The implementation of this HMP and Written Scheme of Investigation could provide additional information which would add to the evidential value of the asset, which could increase its significance.
3. THE SANCTUARY, OVERTON HILL
Scheduled Monument (List Entry No. 1014563)
3.1 The significance of the asset is principally derived from its evidential value. It comprised an early timber circle with two concentric stone circles constructed later. This later phase of the monument appears to be contemporaneous with the Avenue.
3.2 The current setting of the monument comprises its location within the wider landscape of contemporaneous monuments. Little is known of the ceremonial nature or use of the asset but there is no doubt it would have had functional and associative relationships with these other monuments. The asset is in a location which affords good panoramic views across the Kennet valley which include West Kennet long barrow and Windmill Hill. It is uncertain whether inter-visibility between monuments was part of their design but it is likely that the inclusion of other monuments in views from the Sanctuary may have been of some importance in the coherence of the landscape to the society that constructed and used it.
3.3 The asset is publicly accessible and information panels are provided to enhance one’s understanding and experience of it. Although the original circles have not survived, the placing of concrete blocks to mark their locations also enhances the experience of the site. A footpath on the west side allows the visitor to leave the Sanctuary and step into the Avenue, allowing some understanding of the relationship between the two assets. Although the location of the asset can be seen from other points in the landscape, its present condition (with low marking blocks) means it cannot be fully appreciated from a distance. The Sanctuary derives much of its significance from its evidential value but its setting is considered to make a moderate to high contribution to its significance.
3.4 The steeply sloping topography means that it is not possible to see the application area from within the Sanctuary and therefore there are no shared views through the asset and the proposed development. The point at which the Sanctuary ‘joins’ the Avenue is close to the break of slope and from this point there is a clear view down to the application area (see photo). However, from most parts of the asset, the proposed development would not be visible. The removal of selected vegetation and existing structures, which currently obstruct the presumed line of the Avenue in the view from the western edge of the Sanctuary, would restore a view which could enable greater understanding of position of the monuments within the landscape. While this may not increase the significance of the Sanctuary it would have a beneficial effect on its setting.
4. THE STONEHENGE, AVEBURY AND ASSOCIATED SITES
World Heritage Site
4.1 The Stonehenge, Avebury and Associated Sites World Heritage Site WHS is a landscape of international importance and is therefore of Very High Significance. The asset comprises a large landscape, within which lie two areas of Neolithic and Bronze Age ceremonial and funerary monuments. At Avebury, these include the henge itself, the West Kennet and Beckhampton Avenues, the Sanctuary, Silbury Hill, West Kennet Long Barrow and numerous other important barrows. Together these individual assets, and their physical and functional relationships with each other, and the ability to experience many of them in a largely unspoilt landscape, form the setting of the World Heritage Site. The significance of the asset is principally derived from the evidential value of these assets, the potential they have to contribute to international research into the organisation and economy of the prehistoric societies that constructed the monumental landscape. The current setting is considered to make a high contribution to that significance.
4.2 The application area lies within the boundary of the World Heritage Site and is considered to form part of it. The application area covers a very small part of the asset, although it is part of the landscape and visible in views of archaeological components of that landscape. The proposed removal of vegetation and existing structures would open up the probable line of the Avenue, a principal component of the World Heritage Site, allowing a clear view along it which is currently not possible. It is considered that this would constitute a minor enhancement to the setting of the asset.
5. LOCAL BARROWS
Bowl barrow 50m southeast of the Sanctuary forming part of the Seven Barrow Hill round barrow cemetery Scheduled Monument (List Entry No. 1007489)
Bowl barrow 50m southeast of the Sanctuary forming part of the Overton Hill round barrow cemetery Scheduled Monument (List Entry No. 1008459)
Group of five round barrows northeast of the Sanctuary: part of the Overton Hill round barrow cemetery Scheduled Monument (List Entry No. 1008464)
5.1 These assets comprise Bronze Age round barrows, part of a large group located along the Ridgeway on Overton Hill, immediately north of the Sanctuary. The assets survive well and will contain archaeological and environmental remains relating to their cemetery and the landscape in which it was constructed. The Bronze Age barrows are less well known features of the Avebury landscape but form an important part of this ceremonial and ritual landscape.
5.2 These barrows, like many others, stand in a prominent hill top location and are visible from across the landscape. There may have been intervisibility between other barrow groups and any contemporaneous settlements which lay in the vicinity. While the inter- visibility was not part of the asset’s functional relationship with other monuments, it is believed that it was important that the communities had this visual link to their ancestors or former leaders. The barrows still lie within an open agricultural landscape (although the A4 road runs between them).
5.3 There are no views of the application area from or through the barrow groups and due to topography and vegetation there are no shared views of the asset and the application area. The proposed development does not obstruct any views between these assets or associated contemporaneous assets within the wider landscape.
5.4 It is not considered that proposed development within the application area could have an adverse effect on the setting or significance of these assets. Silbury Hill
West Kennet palisaded enclosures ?route of Avenue
Cattery Existing shop
View from the centre of the Avenue immediately west of the Sanctuary looking towards Sarsen Kennels
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