The Foula Report Single Pages
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The Foula Landscape Project Geophysical Survey at Harrier 4th – 11th May 2006 Conducted by The Bath and Camerton Archaeological Society for Foula Heritage The Da Heights landscape on the Shetland island of Foula. (FLP06) SEASON 3 (4/05/06 – 11/05/06) The Foula Landscape Project Geophysical Survey at Harrier 4th – 11th May 2006 Conducted by The Bath and Camerton Archaeological Society for Foula Heritage This report was prepared by Dr John Oswin MA PhD CSci, Jayne Lawes MA MIFA, Keith Turner and Bridget Hetzel MA Geophysics images prepared by Keith Turner. Editor: Bridget Hetzel (FLP06) SEASON 3 (4/05/06 – 11/05/06) i ii Summary At the instigation of Foula Heritage, the Bath and Camerton Archaeological Society undertook an eight day geophysical survey in the region of Harrier, on the Shetland island of Foula, during May 2006. The survey was carried out using a magnetometer and a twin-probe resistance meter, with ancillary measurements of relief obtained by an EDM and a hand held GPS meter. The survey was centred on the North Harrier area with a smaller survey conducted on Da Heights, a few hundred metres to the north. In addition a survey was also carried out at Springs on the northern foreshore, a site threatened by coastal erosion. The main survey at North Harrier confirmed the presence of buried structures in the yard behind Old North Harrier House and burnt mounds in the places stated in earlier work. In addition the survey also indicated probable prehistoric settlements both on the hill slope to the north of Old North Harrier House and near the burnt mounds to the west of the Harrier Burn. The flat grass fields below Old North Harrier House were found to conceal a very extensive area of earlier activity. The hilltop on Da Heights yielded a probable stone ring, possibly with an outer ring and both aligned to the winter solstice. There are also indications of a building beneath the existing planticrub. The coastal survey at Springs was inconclusive. In all, an area of approximately seven acres (3 hectares) was covered. iii List of Figures Figure Page No. The Da Heights landscape, Foula Bridget Hetzel.............................................Cover 1 Location map of Foula Reproduced by permission of Ordnance Survey on behalf of HMSO Crown copyright. All rights reserved 1 2 Map of Foula John Holbourn................................................................................. 2 3 Map of Harrier and Da Nort Touns BH.......................................................... 2 4 The Harrier survey area BH.......................................................................... 3 5 The Magnetometer in use BH.............................................................................. 4 6 The Resistance survey equipment in use BH............................................... 5 7 The Electronic Distancing Meter in use BH.................................................. 6 8 Magnetometer survey results of Harrier with annotated landmarks BACAS. 8 9 Magnetometer survey results of Harrier with anomalies highlighted BACAS.. 10 10 Magnetometer survey results of Harrier – raw data BACAS............................ 12 11 Resistance survey results of Harrier with anomalies highlighted BACAS........ 14 12 Resistance survey results of Harrier – raw data BACAS................................. 16 13 Composite geophysical survey results of Harrier BACAS................................ 18 14 Magnetometer survey results of Da Heights – raw data BACAS..................... 20 15 Magnetometer survey results of Da Heights with anomalies highlighted BACAS 20 16 Resistance survey results of Da Heights – raw data BACAS.......................... 22 17 Resistance survey results of Da Heights with anomalies highlighted BACAS. 22 18 EDM survey results of Da Heights – raw data BACAS.................................... 24 19 EDM and magnetometer survey results of Da Heights BACAS....................... 25 20 John Wood’s construction of the Borrowstone Rig John Wood......................... 26 21 BACAS simplified construction of Borrowstone Rig egg shape BACAS.......... 26 22 Method of construction of above BACAS......................................................... 27 23 The Da Heights stones with the Borrowstone egg shape superimposed BACAS 27 24 The Da Heights stones with alignments BACAS............................................. 28 25 Best Fit diagram of egg shape on Da Heights stones BACAS........................ 29 26 Geometric Fit diagram of egg shape on Da Heights stones BACAS............... 30 27 Construction of concentric ringed egg shape for Geometric Fit option BACAS 31 28 The stone ring location at Springs BH........................................................... 34 29 The survey site at Springs BH....................................................................... 34 30 Magnetometer survey results of Springs – raw data BACAS.......................... 35 31 Magnetometer survey results of Springs with anomalies highlighted BACAS. 35 32 Resistance survey results of Springs – raw data BACAS................................ 36 33 Resistance survey results of Springs with anomalies highlighted BACAS...... 36 iv Table of Contents Page No Introduction ........................................................................ 1 Background 1 Location 1 Scope of report 3 Survey Methodology .......................................................... 4 Equipment 4 Magnetometer 4 Resistance meter 5 Electronic Distance Meter 6 Global Positioning System 6 Grid layout 7 Software 7 The Harrier site ................................................................... 9 Magnetometer survey – results and analysis 9 Resistance survey – results and analysis 15 Assessment of Harrier survey results 19 The Da Heights site ............................................................ 21 Magnetometer survey – results and analysis 21 Resistance survey – results and analysis 23 EDM survey – results and analysis 25 Interpretation of possible stone ring 29 Assessment of the Da Heights survey results 33 The Springs site .................................................................. 34 Magnetometer survey – results and interpretation 35 Resistance survey – results and interpretation 36 Assessment of the Springs survey results 37 Report conclusions and recommendations ..................... 38 Bibliography ........................................................................ 41 Glossary ............................................................................... 42 v Preface and acknowledgments A geophysical survey of certain areas of the Shetland island of Foula had been recommended by Helen Bradley, of Sheffield University, in her recent landscape study but the Foula Heritage funds were too limited to finance a commercial team. However in one of those happy coincidences, a former resident of Foula, now living in Wiltshire, met a member of the Bath and Camerton Archaeological Society (BACAS), one keen to extend the archaeological knowledge of his home, the other with access to geophysical surveying. From this, a chain of events ensued which led to the island hosting the BACAS Geophysical Survey Team in May 2006. BACAS is a society of volunteers led by a core of archaeologists and other experts in their speciality, in particular Jayne Lawes – Director of Excavations, Dr John Oswin – Director of Geophysical Survey and Keith Turner our IT expert. The geophysical survey team, led by Dr John Oswin, has conducted a number of large area surveys and has gained a high reputation for their work. The BACAS Geophysical Survey Team use a Magnetometer and a Twin-probe Resistance Meter. The first detects buried hearths, pits and ditches, whereas the second detects buried stones and walls. These methods are complementary. The survey team also use an Electronic Distance Meter (EDM) which enables detailed contour and positional survey, and a hand held Ground Positioning System Meter (GPS) for rapid relief surveying. The BACAS survey team that worked on Foula consisted of six members, the minimum necessary to operate two instruments simultaneously. The survey team members were: Owen Dicker, Bridget Hetzel, Jayne Lawes, Margaret Nuth, John Oswin and Keith Turner. The team would like to thank everyone on Foula who provided so warm a welcome and assistance. In particular Isobel Holbourn for her wonderful hospitality and access to her land, Sheila Gear for the support she gave to the resistance survey team and Penny Gear for allowing us access to her land. In addition we would like to thank John Holbourn who not only instigated the commission but also transported the survey equipment many hundred miles to and from Foula. vi Introduction Background There had been significant archaeological field work in Shetland, in the years leading up to the millennium, but this had mostly excluded Foula. However, this was rectified by Helen Bradley who undertook a detailed field survey of the island’s archaeology as part of her MA studies at Sheffield University in 2004. Her Foula Landscape Project (FLP) report 2005 and its supplement, recommended a geophysical survey of some sites on the island, as the next stage of investigation. Foula Heritage was keen to procure such a survey and this resulted in the commission of an eight day geophysical survey by the Bath and Camerton Archaeological Society Survey Team. Location The island of Foula lies some 25 km (15 miles) southwest of the centre of mainland Shetland, at approximately 2o 5' west, 60o 4' north. The island covers an area approximately