WOODGATE HOUSE, AYLSHAM, GEOPHYSICS PHASE 4 DETAILED MAGNETOMETER SURVEY

Transcription

1 WOODGATE HOUSE, AYLSHAM, GEOPHYSICS PHASE 4 DETAILED MAGNETOMETER SURVEY Report Number: 39 February 07

2 WOODGATE HOUSE, AYLSHAM, GEOPHYSICS PHASE 4 DETAILED MAGNETOMETER SURVEY Prepared for: Suffolk County Council Archaeology Services Bury Resource Centre Hollow Road Bury St Edmunds IP3 7AY By: Matthew J. Baker MA, BA (hons) Britannia Archaeology Ltd Unit, The Old Wool Warehouse St Andrews Street South Bury St Edmunds Suffolk IP33 3PH T: info@britannia-archaeology.com Registered in England and Wales: September 06 Site Code - Event Number - NGR Planning Ref. n/a OASIS pending Approved By: Date February 07 Britannia Archaeology Ltd 05 all rights reserved Report Number: 39

3 Project Number 67 DISCLAIMER The material contained within this report was prepared for an individual client and solely for the benefit of that client and the contents should not be relied upon by any third party. The results and interpretation of the report cannot be considered an absolute representation of the archaeological or any other remains. Britannia Archaeology Ltd will not be held liable for any error of fact resulting in loss or damage, direct, indirect or consequential, through misuse of, or actions based on the material contained within by any third party. 3

4 Project Number 67 CONTENTS.0 INTRODUCTION.0 SITE DESCRIPTION 3.0 ARCHAEOLOGICAL BACKGROUND 4.0 PROJECT AIMS 5.0 METHODOLOGY 6.0 RESULTS 7.0 CONCLUSIONS 8.0 PROJECT ARCHIVE AND DEPOSITION 9.0 ACKNOWLEDGEMENTS BIBLIOGRAPHY Figure General Location Plan :5000 Figure Grid Plan :000 Figure 3 Grayscale Data Unprocessed :000 Figure 4 Trace Plot :000 Figure 5 Grayscale Processed :000 Figure 6 Interpretation Plan :000 4

5 Project Number 67.0 INTRODUCTION From 04 to 07 Britannia Archaeology Ltd (BA) undertook four phases of geophysics, with the latest phase being run as a community project, on land at Woodgate House, Cawston Road, Aylsham, Norfolk (NGR )..0 SITE DESCRIPTION The site is located km to the south west of Aylsham town centre, between Cawston Road and Stonegate Lane. It lies within the parish boundary of Aylsham and the Broadland District of Norfolk. The site straddles the east-west orientated valley of Mary s Beck, which is a tributary of a larger stream called The Mermaid. Mary s Beck has its source 40m north of the western boundary of the site, and the size of the valley suggests it was more substantial at some point in the past. The northern half of the site slopes down to the south; the southern half slopes down to the north. The centre of the site is situated just below 30m aod and the far northern and south-western extents just touch 35m aod. The north-east corner of the site is currently used for arable farming and a large kitchen garden is present north of the main house. The site is bounded to the north and west by Cawston Road. A new housing development is under construction to the north, but the western boundary remains woodland. Stonegate (Lane) forms the eastern boundary with agricultural fields beyond, and the southern boundary comprises a chain-link fence and hedgerow with agricultural fields beyond. The underlying bedrock is described as Wroxham Crag Formation sand and gravel, sedimentary bedrock formed up to million years ago during the Quaternary Period when the local environment was dominated by swamps, estuaries and deltas periodically inundated by the sea (BGS, 06). The superficial deposits are described as mid-pleistocene glaciofluvial deposits of sand and gravel when the local environment was dominated by ice age conditions (BGS, 06). 5

6 Project Number ARCHAEOLOGICAL BACKGROUND A full desk-based assessment was undertaken for the site in November 04 by Britannia Archaeology, Land at Woodgate House, Cawston Road, Aylsham, Norfolk Desk-Based Assessment, (Adams, MC. 04: R069). The summary of this investigation was as follows: The assessment has identified a very high potential for Roman remains relating to high status villa settlement activity on the site. The quantity and quality of Roman material recovered by Mr Purdy over the years, suggests the presence of a substantial, high status villa complex, probably focused in the area of the Kitchen Garden and immediate surroundings, with outlying industrial areas to the north-east and agricultural areas to the south and north. The potential for all other periods is considered to be low, however the site appears to lie on the periphery of the town s medieval field system and so the potential here is moderate. It has also been subject to significant landscaping as well as farming activity during the post-medieval period so the potential for features or finds dating to this period is considered high. The wider area shows evidence of occupation activity since the Neolithic period with significant settlement activity identified to the north-west of Aylsham in the Bronze Age (outside the search area), at Brampton to the south-east in the Roman period, and in Aylsham itself from the Anglo-Saxon period onwards. The cartographic sources suggest significant remodelling of the plots around Woodgate House between the late 8th and late 9th century AD. A system of old track ways are clearly visible in both the cartographic sources and the geophysics results in the southern half of the site. 4.0 PROJECT AIMS The aims of this phase of the Aylsham Roman Project are to undertake non-intrusive geophysical survey to expand on previous surveys, conducted in the north-east and 6

7 Project Number 67 south-east fields, to further define magnetic anomalies identified in previous geophysical surveys. To further enhance our understanding of the archaeological potential of the site; To characterise the development, phasing, spatial organisation, character, function, and the nature of social, economic and industrial activities on site; Place the evidence for Roman activity at the site in context with known remains of a similar date around Aylsham and the wider region; Undertake analysis of the survey data leading to appropriate forms of public dissemination. 5.0 METHODOLOGY The survey grid was be set out to the Ordnance Survey OSGB36 datum to an accuracy of ±0.0m using a Leica Viva Glonnass Smart Rover GS08. A Bartington Dual Grad 60- fluxgate gradiometer was used to undertake the survey, because of its high sensitivity and rapid ground coverage. The soils and underlying geology are receptive to magnetometer survey, but good results are heavily dependent on the contrast between the fills of a feature (with humic and charcoal rich deposits providing the best results) and the relative weakness of the local magnetic background field. Only minimal processing of the datasets has been undertaken, data processing allows for the correction of errors introduced during the survey and instrument errors. The survey data has been processed using TerraSurveyor software V3, where the following data processes were applied: Destripe: Removes striping effects from the raw data caused by discrepancies between different sensors and walking directions caused by alternate zig-zag traverses. Destagger: Corrects the displacement of anomalies caused by alternate zig-zag traverse. Clip: The range of the data can be set to specified maximum and minimum values in order to improve the contrast of weaker anomalies within the data. 7

8 Project Number 67 Compress: Weak anomalies were further enhanced by applying an arctangent weighing to the data. Grad. Shade: The overall appearance of the data was improved The raw and processed greyscale plots have been produced for comparison. An XY trace plot consisting of the processed data will be used in combination with raw and processed greyscale data. An interpretation plan characterising the anomalies has been produced based on the evidence collated from the greyscale and XY trace plots. 6.0 RESULTS (Figs. -6) The unprocessed data from the magnetic surveys are shown in figure. Figure is displayed as a greyscale plot with the maximum and minimum readings for each survey highlighted in red and blue. The processed data, following the application of the data processing methodology described above. The processed data has revealed a number of responses of archaeological significance, the interpretation of which is described below. 6. Interpretation Kiln Field (FIG.5) The most notable features within this field are 000 which are two discrete positive anomalies with negative responses, there is no separation between the two polarities. These two anomalies are the two kilns excavated during the 06 summer excavation, the magnetic signal produced by the two kilns has masked the presence of features in the immediate area. The majority of anomalies identified in the survey of the kiln field have been low amplitude positive linear anomalies, which are indicative of infilled ditch type features. Which possibly represent some form of field boundary. Immediately to the south of the two kilns are a series of positive linear anomalies with associated negative anomalies 00. Which could represent bank and ditch type features. Possibly relating to the ditches excavated in area (00). The kiln field data has revealed several discrete positive anomalies, ranging in size from c.-3m. The anomalies are present through the survey area, with a concentration of six 8

9 Project Number 67 anomalies in the eastern area of the survey 003. The shape and size of these anomalies are consistent with those resulting from infilled pit type features. Modern disturbance Three areas of increased magnetic noise can be seen in the data 00, 004 and 005. Anomaly 00 corresponds with the location of area and relates to the backfilling of this excavated area. Anomaly 004 is located to the south-west of the kiln excavation area and is the result of some brick debris on the ground close to the excavation area. The origin of disturbance 005 is currently unknown, however, due to the high amplitude of the signal it is most likely the spread is modern in origin. Around the perimeter of the survey area are several areas of increased magnetic disturbance 006, these have been produced by a fence surrounding the field. The halo effect produced by the fence has the possibility to mask magnetic anomalies. Numerous high amplitude magnetic spikes can be seen in the data 007. Each of these discrete magnetic spikes consists of a well defined dipolar response. There high amplitudes suggests the presence of ferrous debris in the topsoil. North-east field (FIG.5) The anomalies present within the survey are very weak positive linear anomalies. On the western limit of the survey three low amplitude positive trending linear anomalies 000 were identified, these anomalies run parallel to one another for c.4-4m with a northwest to south-east orientation. On the eastern edge of the survey area, two more low amplitude positive trending linear anomalies can be seen, these run parallel to one another c.4m apart, with an east to west orientation and are visible in the data for c.30-4m. A concentration of discrete low amplitude positive anomalies, the shapes of anomalies are largely irregular suggesting that these anomalies could be natural in origin, possibly tree root boles. However, the more regular oval shaped anomalies could be archaeological in origin. The low signal strength of the positive anomalies in this field suggests the features have been heavily truncated by modern ploughing. 9

10 Project Number 67 Along the eastern edge of the survey area is a negative trending linear anomaly which is c.0m in length with a north to south orientation. The anomaly follows the edge of the field and is most likely the result of modern ploughing in the field. Modern disturbance The northern-most corner a fence and trackway have produced a slight distortion to the earth s magnetic field 004. The northern half of the survey area has identified numerous discrete magnetic spikes 005, their high amplitude suggests ferrous debris in the ploughsoil. Lake field (FIG.6) South of the lake sees an increase in anomalies. Most of the anomalies appear as positive linear anomalies. Many of these anomalies have associated negative linears. These anomalies appear to form enclosures 3000, 300, 300 and Enclosure 3000, is sub-rectangular in form and c.48m in width, the anomaly is displayed in the data as a series of positive and negative linear anomalies. Multiple linears orientated north to south appear off of the main east to west linear, which could suggest multiple phases of recutting or multiple subdivisions of the main enclosed area. The enclosed area appears to have internal features 3004, which appear to be infilled pit type features. However, the larger amorphous anomalies might be natural in source. Adjoining enclosure 3000 is another enclosure 300. This anomaly appears in the data as two curvilinear positive anomalies with associated negative internal response, possibly representing a ditch with internal bank. Enclosure 300 is sub-oval in shape and c.0m in width. Immediately to the east of the aforementioned enclosure is another subrectangular enclosure 300. This enclosure is formed of positive linear anomalies with associated negative linear anomalies. The enclosure is c.4m in width, with possible internal features. It is possible that this enclosure has internal divisions, or is cutting or cut by another enclosure. Anomaly 3003 has been truncated by modern service pipe Formed of curvilinear positive anomaly it is c.8m in width and has some internal features. All the enclosures appear to be associated with a linear anomaly 3005, which consists of two positive linear trending anomalies running parallel c.6m apart from one another. Between these two positive anomalies is a weakly negative intermittent linear anomaly. 0

11 Project Number 67 The negative response given by anomaly 3005 may represent a metalled surface. Therefore 3005 could be a form of trackway that enclosures are aligned off of. Running north-east to south-west is another anomaly 3006 which is similar in appearance to anomaly This may be the remnants of another trackway. To the north of the lake another survey area has discovered more positive and negative linear anomalies 3007, these anomalies have a similar form and orientation to the anomalies south of the lake. These anomalies have been truncated by the construction of the lake. Modern disturbance A strong magnetic liner anomaly 3008 has been identified running north-west to southeast in the southern survey area. This anomaly is a buried fence. This anomaly has masked part of enclosure An area of increased magnetic noise has been identified in the southern survey area. This area has been interpreted as an area of disturbed ground 3009, possibly relating to the construction of the lake. Several areas of magnetic disturbance can be seen on the edges of the southern survey area, these have been caused by a metal fence which has produces a distortion in the local magnetic field. The most numerous anomaly in the southern most survey area were discrete magnetic spikes. These consist of a high amplitude magnetic spike in the data which most likely represent buried ferrous debris within the topsoil. Conclusion The geophysical surveys have so far identified numerous anomalies which appear to be of archaeological origin. The majority of anomalies present within the survey areas have been positive linear anomalies, which are synonymous with infilled ditch type features. A large quantity of these anomalies have associated negative linears, which may indicate the presence of remnant bank material, possibly indicating bank and ditch type features. The varying signal strengths of some of these anomalies, particularly in the two northern fields, is suggestive of the features being intermittently truncated or disturbed at the source. The survey area south of the lake has revealed numerous anomalies which appear to form enclosures. These enclosures appear as positive responses with associated low

12 Project Number 67 amplitude negative responses, which is indicative of ditches and banks. These enclosures appear to be related to a linear anomaly formed of a low amplitude negative response between two low amplitude positive linear anomalies suggesting that this anomaly could be a trackway with a metalled surface. The magnetic contrasts seen in the data indicates the underlying geology was suited to magnetic geophysical survey. However, the magnetic contrast is clearer in the southernmost survey areas where the land has not been subjected to modern ploughing. 8.0 PROJECT ARCHIVE AND DEPOSITION A full archive will be prepared for all work undertaken in accordance with guidance from the Selection, Retention and Dispersion of Archaeological Collections, Archaeological Society for Museum Archaeologists, 993. Arrangements will be made for the archive to be deposited with the relevant museum/her Office, in this case will be the Norwich Castle Museum. 9.0 ACKNOWLEDGEMENTS Britannia Archaeology Ltd would like to thank Mr Peter Purdy for commissioning the work and for allowing access to the land. Britannia Archaeology would also like to thank the volunteers of the Aylsham Roman Project for their help in conducting the surveys. The survey was undertaken by volunteers of the Alysham Roman Project and Britannia Archaeology.

13 Project Number 67 Bibliography Ayala. G. et al Geoarchaeology; Using Earth Sciences to Understand the Archaeological Record. English Heritage. Chartered Institute for Archaeologists. 04. Standard and Guidance for Geophysical Survey Clark. A. J Seeing Beneath the Soil, Prospecting Methods in Archaeology. BT Batsford Ltd, London. David. A Geophysical Survey in Archaeological Field Evaluation: Research and Professional Services Guidelines. No.. English Heritage. David. A. et al Geophysical Survey In Archaeological Field Evaluation, Second Edition. English Heritage. Department for Communities and Local Government, 0.National Planning Policy Framework (NPPF) English Heritage, 008. Geophysical Survey in Archaeological Field Evaluation. Research and Professional Service Guideline No, nd edition. Gaffney. C, Gater. J. and Ovenden. S. 00. The Use of Geophysical Techniques in Archaeological Evaluations. IFA Technical Paper No. 6. Gaffney. C. and Gater. J Revealing the Buried Past, Geophysics for Archaeologists. Tempus Publishing Ltd. Gurney, D Standards for Archaeology in the East of England, East Anglian Archaeology Occasional Paper 4. Institute for Archaeologists. 0. Standard and Guidance for Archaeological Geophysical Survey. Linford. N Notes from an English Heritage Seminar. Schmidt. A. 00. Geophysical Data in Archaeology: A Guide to Good Practice. Archaeology Data Service. Oxbow Books. Whitten. D.G.A The Penguin Dictionary of Geology. Penguin Books Ltd. London. Witten. A.J Handbook of Geophysics and Archaeology. Equinox Publishing Ltd. London. 3

14 Project Number 67 Websites The British Geological Survey, 06, (Natural Environment Research Council) Geology of Britain Viewer - 4

15 N Cromer 5 SITE Marrio tt's W ay Norfolk Tra PUMPHREY WAY ck Kings Lynn Nelson Close NORWICH 3 4 ston Caw 5 7 d Roa 9 ESS PEABODY ROAD 4 0 HOBART Thetford 8 LANE Woodgate Cottages 0 ATE G WOOD Suffolk The The Lodge Lodge 8 W AY 33.3m 33.3m Nursery Ppg Sta Tra ck STONEGATE Essex Nursery The Round Path (um) Water 30.m FB Track 45 B Site Boundary Drain Woodgate House NGR: REF: P67 PROJECT: 30.6m Path (um) WOODGATE HOUSE, AYLSHAM, GEOPHYSICS PHASE 4 DESCRIPTION: GENERAL LOCATION AND GRID PLAN CLIENT: AYLESHAM ROMAN PROJECT BRITANNIA ARCHAEOLOGY LTD UNIT THE OLD WOOL WAREHOUSE ST ANDREWS STREET SOUTH BURY ST EDMUNDS SUFFOLK IP33 3PH SITE T: E: info@britannia-archaeology.com W: Reproduced on plans supplied by the client from the Ordnance Survey map with the permission of the controller of Her Majesty s Stationery Office. Licence number: CROWN COPYRIGHT 07. :500 0 :500 00m Copyright Britannia Archaeology Ltd 07 DATE: AUTHOR: APPROVED: FEB 07 MJB DPM PLOT: A3 VERSION: FIGURE:

16 Drain 4 0 STONEGATE N 4 Close ESS Cawston Road PEABODY ROAD 9 0 HOBART LANE 8 +00nT oodgate Cottages WOODGATE The TheLodge Lodge 8 WAY 33.3m Ppg Sta 33.3m Nursery Track Nursery The Round -00nT 30.m Water FB Track B 45 Site Boundary Woodgate House NGR: REF: P67 PROJECT: WOODGATE HOUSE, AYLSHAM, GEOPHYSICS PHASE m DESCRIPTION: NON-PROCESSED DATA PLAN CLIENT: AYLSHAM ROMAN PROJECT BRITANNIA ARCHAEOLOGY LTD UNIT THE OLD WOOL WAREHOUSE ST ANDREWS STREET SOUTH BURY ST EDMUNDS SUFFOLK IP33 3PH : m :000 T: E: info@britannia-archaeology.com W: Copyright Britannia Archaeology Ltd 06 DATE: PLOT: VERSION: NOV 06 A3 Reproduced on plans supplied by the client from the Ordnance Survey map with the permission of the controller of Her Majesty s Stationery Office. Licence number: CROWN COPYRIGHT 06. AUTHOR: APPROVED: MJB DPM FIGURE:

17 N Nelson Close ston 5 7 Caw d Roa + nt 9 ESS PEABODY ROAD HOBART LANE Woodgate Cottages 0 GATE WOOD 36.5m The The Lodge Lodge 8 W AY 33.3m 33.3m Nursery Ppg Sta STONEGATE Tra ck - nt Nursery The Round Water 30.m Track Site Boundary 4 5 B FB Drain Woodgate House NGR: REF: P67 PROJECT: WOODGATE HOUSE, AYLSHAM, GEOPHYSICS PHASE 4 DESCRIPTION: PROCESSED DATA PLAN 30.6m CLIENT: AYLSHAM ROMAN PROJECT BRITANNIA ARCHAEOLOGY LTD UNIT THE OLD WOOL WAREHOUSE ST ANDREWS STREET SOUTH BURY ST EDMUNDS SUFFOLK IP33 3PH T: E: info@britannia-archaeology.com W: 0 :000 Reproduced on plans supplied by the client from the Ordnance Survey map with the permission of the controller of Her Majesty s Stationery Office. Licence number: CROWN COPYRIGHT 07. :000 00m Copyright Britannia Archaeology Ltd 07 DATE: AUTHOR: APPROVED: FEB 07 MJB DPM PLOT: A3 VERSION: FIGURE: 3

18 Drain STONEGATE N 4 Close ESS Cawston Road PEABODY ROAD 9 0 HOBART LANE Positive Anomaly Woodgate Cottages Negative Anomaly The TheLodge Lodge Kiln 36.5m WOODGATE WAY m Strong magnetic noise Ppg Sta 33.3m Nursery Magnetic disturbance Service pipe Discrete magnetic spike Track Nursery The Round 30.m Water Track B 45 Site Boundary FB Woodgate House NGR: REF: P67 PROJECT: WOODGATE HOUSE, AYLSHAM, GEOPHYSICS, PHASE m DESCRIPTION: INTERPRETATION PLOT CLIENT: AYLSHAM ROMAN PROJECT BRITANNIA ARCHAEOLOGY LTD UNIT THE OLD WOOL WAREHOUSE ST ANDREWS STREET SOUTH BURY ST EDMUNDS SUFFOLK IP33 3PH : m :000 T: E: info@britannia-archaeology.com W: Copyright Britannia Archaeology Ltd 07 DATE: PLOT: VERSION: FEB 07 A3 Reproduced on plans supplied by the client from the Ordnance Survey map with the permission of the controller of Her Majesty s Stationery Office. Licence number: CROWN COPYRIGHT 07. AUTHOR: APPROVED: MJB DPM FIGURE: 4

19 STONEGATE N Cawston Road Positive Anomaly Negative Anomaly Kiln Strong magnetic noise Magnetic disturbance 007 Discrete magnetic spike ry Site Boundary Nursery 005 NGR: REF: P67 The Round PROJECT: WOODGATE HOUSE, AYLSHAM, GEOPHYSICS, PHASE 4 DESCRIPTION: INTERPRETATION PLOT CLIENT: AYLSHAM ROMAN PROJECT BRITANNIA ARCHAEOLOGY LTD UNIT THE OLD WOOL WAREHOUSE ST ANDREWS STREET SOUTH BURY ST EDMUNDS SUFFOLK IP33 3PH T: E: info@britannia-archaeology.com W: : m :000 Copyright Britannia Archaeology Ltd 06 DATE: PLOT: VERSION: FEB 07 A3 Reproduced on plans supplied by the client from the Ordnance Survey map with the permission of the controller of Her Majesty s Stationery Office. Licence number: CROWN COPYRIGHT 06. AUTHOR: APPROVED: MJB DPM FIGURE: 5

20 N Positive Anomaly Negative Anomaly 3007 Strong magnetic noise Magnetic disturbance Service pipe Discrete magnetic spike 3008 Site Boundary m NGR: PROJECT: REF: P67 WOODGATE HOUSE, AYLSHAM, GEOPHYSICS, PHASE 4 DESCRIPTION: INTERPRETATION PLOT 3000 CLIENT: AYLSHAM ROMAN PROJECT BRITANNIA ARCHAEOLOGY LTD UNIT THE OLD WOOL WAREHOUSE ST ANDREWS STREET SOUTH BURY ST EDMUNDS SUFFOLK IP33 3PH T: E: info@britannia-archaeology.com W: : m :000 Copyright Britannia Archaeology Ltd 07 DATE: PLOT: VERSION: FEB 07 A3 Reproduced on plans supplied by the client from the Ordnance Survey map with the permission of the controller of Her Majesty s Stationery Office. Licence number: CROWN COPYRIGHT 07. AUTHOR: APPROVED: MJB DPM FIGURE: 6