Field Visit

Date June 2013 - July 2013

Event ID 992197

Category Recording

Type Field Visit

Permalink http://canmore.org.uk/event/992197

HU 326 900 (Beorgs of Uyea) and HU 327 850 (Grut Wells) Building on previous years’ work in North Roe led by Ballin (DES 2013, 167-8) the first season of the North Roe Felsite Project; Making an Island World: Neolithic Shetland, took place in June–July 2013. There were three foci of work: the geochemical and petrological characterisation of outcrops and artifacts; the topographical survey and characterisation of production at Grut Wells; and the analysis and characterisation of axes and knives in the Shetland Museum. A multi-scalar approach to data collection and analysis is being implemented and integrated through a project GIS.

Geochemical and petrological mapping – A Thermo Scientific ‘NITON XL3T GOLDD+’ portable x-ray fluorescence analyzer (PXRF), on loan from and with thanks to Historic Scotland, was used to measure elemental compositions of a large study sample of felsite (stone axe petrological Group XXII) consisting of: rocks at outcrop; debitage from tool production episodes; and polished stone axes and knives from the collection of the Shetland Museum. Of the almost 500 implements associated with Shetland and/or described as Group XXII the project has PXRF analyses for 213. A total of 900 PXRF analyses were carried out in Shetland, at the quarry complex and on the objects in the Shetland Museum, and a further 211 in the NMS. At total of 93 field samples were collected and 26 thin sections prepared, on which initial analysis has been carried out.

Analysis of this material is ongoing but the PXRF appears to be very consistent with an estimate of less than 1% variability in results as measured from the test samples. At the quarry complex this evidence will be used to identify outcrops, archaeological sites and landscape features for further investigation during the 2014 season and beyond. It is planned to extend the PXRF survey to cover all polished felsite stone axes and knives in major Scottish museum collections.

Topographical survey and characterization of production at Grut Wells – A detailed survey of an area 250m (N–S) by 150m (E–W) provided a detailed basis for understanding the working of felsite in this area. There are two distinct groups of quarry pits on a N–S alignment (following a felsite dyke). Other pits appear to be single episode or exploratory quarry pits. On the surface there were significant numbers of large blocks of felsite. The survey demonstrated a clear spatial relationship between these large blocks of felsite (over 300mm in length) and the quarry pits. It seems clear that the blocks of felsite were quarried from the pits and were the primary source utilized for the production of rough-outs.

The survey was accompanied by a more detailed sampling strategy to try to understand the surface accumulation of felsite debitage. This demonstrated that there was a clear patterning in the occurrence of felsite. There is a strong correlation of high density areas of debitage with the quarry pits. Within the zone of the major concentration of felsite debitage a sampling grid of over 50 1m2 sample areas were utilized to characterize the surface debitage. Material was collected from five sample areas. This will be compared with the debitage produced during the experimental manufacture of axes and knives from felsite which is currently taking place in University College Dublin.

Axes and knives in the Shetland Museum – All the axeheads (126) and knives (60) in the Shetland Museum were characterized archaeologically, their geochemical signature and petrology was recorded (see above) and they were photographed.

Analysis of the axeheads demonstrated the dominance of felsite as a source. Almost 75% (94 out of 126) are made of felsite, with a significant proportion manufactured from serpentinite (13%). The dominance of felsite is even more apparent in the case of the knives with 95% (57 out of 60) being made from felsite. The detailed examination of this collection also provided quantitative support for the visual observation that felsite axeheads are less spectacular in appearance than the knives. Whereas the felsite knives in the collection are produced in almost equal numbers from non-spherulitic and spherulitic felsite, the majority (85%) of the felsite axeheads were made from non-spherulitic varieties of felsite.

Almost 80% of the Shetland knives are either intact or chipped. It should be noted that the spectacular find of 19 knives in the Stourbrough Hill hoard constitute almost a third of the total number of knives. A total of 42 (70%) of the knives were shown to be made from flake-blanks, whereas the blanks used for the remaining pieces are uncertain. In more than 50% of cases spherulitic, highly patterned forms of felsites, were used. It is possible to subdivide the knives into a number of formal types with sub-rectangular forms (54%) being most common, followed by examples of oval/pointed-oval form (17%). Other shapes may generally be the result of use wear and re-sharpening. Analysis of the axes and knives suggests that there were two distinct production lines; one for pieces that were intended for ritual use and deposition and one for general use with potential for repeated reworking.

Hoard and miniature heel-shaped cairn – Two other results from the fieldwork demonstrate the special role of felsite, and of the quarry complex in the wider context of the Shetland archipelago. A hoard of three felsite roughouts, two large axeheads and a Shetland knife, was discovered below and to the SE of the Grut Wells dyke discussed above. The material is macroscopically identical to the debitage around the quarry pits. Comparison with the Shetland Museum collection indicates that the objects in the hoard are unusually large and well produced. A small megalithic tomb which can be seen as having the characteristics of the distinctive Shetland heel-shaped cairns was discovered, c300m N of the surveyed area at Grut Wells and overlooking the line of outcrop of a felsite dyke which dips down on to lower ground. The tomb appears to be orientated to visually link this area of the complex with the Beorgs of Uyea to the N. Far from being remote it would appear that the North Roe felsite quarry complex was a central place not just for axe and knife production but also for the construction of identity in Neolithic Shetland.

Funder: The National Geographic Northern Exploration Fund

Gabriel Cooney, University College Dublin

Torben B Ballin, Lithic Research/University of Bradford

Vin Davis, Implement Petrology Group

Alison Sheridan, National Museums Scotland

Mik Markham, Implement Petrology Group

Will Megarry, University College Dublin, 2013

(Source: DES)