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Excavation

Date 8 May 2017 - 2 June 2017

Event ID 1040837

Category Recording

Type Excavation

Permalink http://canmore.org.uk/event/1040837

HU 327 848 (Grut Wells) and HU 326 902 (Beorgs of Uyea) The North Roe Felsite Project (NRFP) is a partnership involving University College Dublin, Queen’s University Belfast, Shetland Museum and Archives, National Museums of Scotland and the Implement Petrology Group with the assistance of Archaeology Shetland, building on the reconnaissance survey undertaken by Torben Ballin. The project is addressing a central research issue for the Neolithic in Shetland (and Scotland); the role of a visually distinctive stone; (reibeckite) felsite (Group XXII in the Implement Petrology Group scheme of British stone implement petrology Groups) which, during the Neolithic period, people transformed into polished axes and knives. The source is at North Roe, mainland Shetland, where there is a well preserved major quarry complex. Here, blue to grey felsite dykes stand out against red granite bedrock. The NRFP is using archaeological and geochemical/petrological survey, detailed GPS and UAV survey and targeted excavation to identify the scale, character and date of the extraction processes. A project GIS integrates data from the quarry complex with analysis and mapping of felsite artefacts from across the Shetland archipelago in museum and private collections, facilitating integrated insights into the life path and role of these objects in Neolithic Shetland.

To date there have been four field seasons at North Roe, between 2013 and 2017, collecting data at a range of scales at the quarry and beyond. In 2013 and 2014 PXRF survey was carried out across the quarry complex, and on the collections of felsite objects in the Shetland Museum and National Museums Scotland which were also recorded in detail. Associated petrographic analysis has led to the identification by the Implement Petrology Group (Mik Markham and Vin Davis) of 15 petrographic types of felsite. This report focuses on the results of the 2017 field season.

Survey in the 2017 season, 8 May 2017 – 2 June 2017, concentrated on the Beorgs of Uyea area of the North Roe quarry complex. Within the scheduled monument (SM 890) at the Beorgs of Uyea detailed survey continued, building on survey begun in 2014. This baseline survey is providing a detailed record of the surface deposits and evidence for quarrying and production processes at this key location. It is also documenting a range of features that appear to be associated with the quarrying activity, notably a series of over 60 standing stones to the SE of the zone of quarrying and a major concentration of felsite blocks further to the E, at a distance of over 300m from the exploited felsite dykes.

Dyke and debitage characterisation – Detailed description of the seven major felsite dykes (A-G, numbered from W-E) at Beorgs of Uyea, was completed. This incorporated characterization of the dykes and associated debitage. A series of transects along each dyke was recorded in detail focusing on in situ dyke blocks of felsite, quarried blocks and debitage. This was accompanied by photographic coverage. In this coverage 1 x 1m squares were photographed and the NW corner of these squares surveyed in using GPS. This photographic coverage can be explored in the project geographical information system (GIS) alongside high resolution ortho-photography produced by the UAV. The felsite types defined by the Implement Petrology Group were used to petrographically characterise the dykes and felsite debitage.

Preliminary analysis of the results indicates that there is lateral and longitudinal variation in the felsite petrographic type within the dykes. The degree of this variation is different between dykes A-G. The petrographic typology does appear to be broadly effective in characterizing the dykes with a major type represented and one or two other types, but additional features needed to be recorded, such as the occurrence of spherulites at varying sizes.

Object characterisation – To complement the dyke and debitage characterization in terms of understanding the different stages in the quarrying and production the occurrence of felsite roughouts or preforms, granite and felsite hammerstones (both local and imported, probably from the coast 2kms to the N), felsite wedges and ‘cores’ was also recorded across the main quarry area at the Beorgs of Uyea. There is significant variation in terms of the density of the objects within the area. This appears to represent variation in intensity of quarrying and production. Interestingly, there is a general denser occurrence of material across the northern part of the dykes and towards the outermost dykes on the W and E sides. At the eastern end there is a very abrupt fall off in density immediately E of the easternmost dyke. It should be noted that there is a notable lack of final stage felsite roughouts or preforms compared to Grut Wells, the other area of the North Roe quarry complex intensively studied by the NRFP.

Work is ongoing on comparison of the object characterization with the felsite dyke characterisation and debitage zones to understand how the artefact distribution matches with different zones of working that are being identified.

Block characterisation to the SE of the quarry area – In the area upslope and to the SE of the dykes A–G at the Beorgs, the occurrence of a concentration of large and very large felsite blocks (and a small number of felsite standing stones) had been recorded in 2016. These were characterised by felsite petrographic type and photographed. It is interesting that there appears to be a dominance of one type of felsite, suggesting a link with a particular dyke in the quarry area.

Standing stone survey – Survey in 2017 focused on two groups of standing stones (called Groups A (6 standing stones) and B (9 standing stones) to the N of the hilltop cairn, SE of dykes A-G. Both groups of standing stones appear to be focused around low granite outcrops. Only definite upright standing stones were included in the survey. These were recorded (including orientation), measured and photographed.

Features to the SW and W of main quarry complex – A number of features (Features 1-6) were noted during the survey. These features appear to be in a similar location in relation to topography and slope. The features appear to be distinct and different from the late 20th-century military hides that occur in a concentration immediately to the W of the quarry area.

Excavation – Grut Wells – A further excavation trench (Trench 3) was opened at Grut Wells following the excavation of Trenches 1 and Trench 2 in 2014/2016. The purpose of this trench was to reveal another area of the quarried dyke (composed of fine-grained felsite with dispersed pink feldspar phenocrysts) which had been identified in Trench 2. Trench 2 had also contained granitic sand and sandy silt/clay deposits that appeared to have potential for OSL dating. Trench 1 across Pit 8 had revealed what appeared to be the upper area of the deposits on the western side of the dyke. This was probably upcast/fill covering the quarried dyke surface, which was not exposed during the excavation of Trench 1.

Trench 3 was positioned immediately E of the E end of Trench 1. Its long axis was placed on the same E/W alignment as Trench 1 and the S side of Trench 3 was on line with the S side of Trench 1. Trench 3 measured 6m E/W and 2m N/S. In the SW corner of the trench there appeared to be a small area exposed of the in situ dyke, this influenced the placement of the trench. The ground surface sloped very gently to the E with the surface composed of tufty areas of vegetation and exposed felsite debitage and granite generally less than 200mm in maximum dimension, with occasional larger blocks.

Removal of the vegetation revealed that the felsite debitage and granite extended E/W across the trench. However, it was interrupted by a distinct peat-filled depression trending NW/ SE across the trench. The central point of the depression was c2.4m from the W end of the trench and it measured 2.2 x 1.2m in extent. The surface deposits immediately to the E and W of this depression had peaty lenses. As excavation proceeded it was clear that as well as marking the latest event in the trench, a deliberate cut into earlier deposits, this peat-filled depression also marked a distinction between the deposits to the E of it and the deposits to the west.

Dealing with the deposits to the W firstly, these represent a series of fills of a quarry pit which had been dug on the eastern side of the dyke. This quarry pit had a maximum E/W width of 2.8m and the felsite had been quarried to a depth of at least 1.6m. It would appear that the dyke extended at least 0.8m further E than the current quarried face exposed in the E-facing section of Trench 3 and that beyond this the granite/ felsite margin was removed, as well as up to 1.0m width of granite. The lowest part of the pit was only 0.5m wide and was focused on the removal of felsite and the granite/ felsite margin. The restricted nature of the trench made it impossible to fully excavate the base of the pit.

The deposits filling the quarry pit appear to represent backfill into a quarry pit as active quarrying moved to the N or S of the area exposed in Trench 3. These fills consisted largely of granitic sands/sandy silts/clays containing felsite debitage and associated artefacts: hammerstones, wedges and axe roughouts or preforms. Two distinct deposits were placed on the stepped side of the wider, upper part of the pit dug into the granite/sand at a depth of 0.8m from the surface. At a depth of 0.6–1.0m a deposit of several large granite blocks appears to have been deliberately placed to level up the backfill of the pit.

To the E of the cut discussed above, and below the surface deposit of a general spread of felsite debitage and granite, there appeared to be a slight mounding of material immediately E of the quarry pit. This seems to represent upcast from a quarry pit, but not necessarily from the area within the trench. More importantly the character of the deposits in this eastern area of the trench (measuring 2m E/W at the southern edge of the trench and 4m E/W at the northern edge) represent in situ activity areas. The character of the deposits and the felsite debitage indicates that what is represented are the initial stage where large quarried blocks were reduced to convenient size for tool production and the subsequent various stages of lithic reduction where these blocks were reduced into preforms or roughouts, down to final stage roughouts. These are the first in situ working areas identified in any of the excavation areas to date at the quarry complex. Alongside the debitage from different stages of production and reduction there were appropriately sized hammerstones and also the wedges associated with quarrying. Recognising the significance of these deposits, and that they had not been the primary focus of the excavation, this eastern area was only excavated to a depth of 0.4m.

It would appear that the cut, which became filled with peat, was cut into both these in situ workshop deposits to the E and the top of the fill of the quarry pit to the west. One plausible explanation for this cut is that it represents late stage felsite quarrying activity where previously quarried felsite blocks in the fill of the quarry pit were re-utilized.

Samples were taken for OSL dating from three profiles in the sections of the trench (David Sanderson, SUERC). Importantly, charcoal was identified in several of the contexts in the trench, both in the fill of the quarry pit and from the workshop area to the east. The charcoal is dominated by birch (charcoal identification by Lorna O’Donnell). Birch would appear to have been a major component in the shrubby woodland cover prior to Neolithic clearance. To date three radiocarbon dates have been obtained (14Chrono Centre, QUB). These are the first dates for the quarrying activity at the North Roe quarry complex. These indicate activity in the Early to Middle Neolithic in Shetland broadly between 3600–3300 BC. It is planned to date more samples from Trench 3.

Archive: UCD School of Archaeology (currently) and National Museums Scotland/Shetland Museum and Archives (intended)

Funder: National Geographic Society, University College Dublin, National Museums Scotland and Queens University Belfast

Gabriel Cooney and William Megarry – UCD School of Archaeology, University College Dublin, and School of Natural and Built Environment, Queen’s University Belfast

(Source: DES, Volume 18)

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