Diversions

I have been branching out of prehistory lately and following a number of temporary diversions from my research, so I thought I’d tell you about them. As part of my placement with the Yorkshire Dales National Park Authority I have been able to get out and about and help with geophysical surveys done by some of the local archaeological groups.

 

Members of Ingleborough Archaeology Group use a magnetometer to survey the site at Selside.

Fig. 1 Members of Ingleborough Archaeology Group use a magnetometer to survey the site at Selside.

A section of the Selside magnetometer data (approx. 20m x 18m). The strong black and white anomaly towards the bottom left corner marks the position of a suspected hearth. The data is displayed at +/-2.75nT, black is high.

Fig. 2 A section of the Selside magnetometer data (approx. 20m x 18m). The strong black and white anomaly towards the bottom left corner marks the position of a suspected hearth. The data is displayed at +/-2.75nT, black is positive.

The first of these was Ingleborough Archaeology Group, who have been investigating a site on the hillside above Selside, Ribblesdale, which consists of the remains of several stone walled structures. The geophysical survey was used to give an indication of what might be there and, alongside other considerations, guide excavation strategy. Although the remains of the walls were visible on the ground as earthworks and rocks, they don’t show up in the magnetometer data (fig. 2) – they are made of the local limestone and, aided and abetted by the thin soils, have next to no magnetic contrast with their surroundings. The magnetometer did, however, detect several magnetic anomalies that I interpreted as being caused by hearths or similar burning, so it was encouraging to hear that subsequent excavation has revealed possible hearths. Excavation turned up very few finds, although this in itself, along with an early medieval knife, means that current thinking places the structures in the Pre-Conquest period.

 

I have also been involved with Swaledale and Arkengarthdale Archaeology Group and their geophysical survey of Ellerton Abbey, a scheduled site near Marrick, in Swaledale. The site contains the remains of a small Cistercian nunnery, probably founded around 1200. Only the ruined church survives above ground now, and this was the focus of architectural, earthwork and geophysical surveys in 1997, which investigated evidence for the surrounding priory complex – you can read the report here. Adjacent to the nunnery lies an area of earthworks believed to reflect a deserted medieval village, while the gill and hillside above the abbey are suspected of being the location of a mill and water management system; these (the DMV and mill/watersource) have been the subject of the latest magnetometer survey. The data is now at a processing stage and it will be interesting to see how interpretation of this complex site unfolds.

 

The site of Bainbridge 'univallate hillfort'.

Fig. 3 The site of Bainbridge ‘univallate hillfort’.

Resistivity data from Bainbridge, covering an area 20 x 40m. Data is displayed at +/-1 standard deviation, so black shows areas of high resistance and white represents low resistance i.e. ditches.

Fig. 4 Resistivity data from Bainbridge, covering an area 20 x 40m. Data is displayed at +/-1 standard deviation, so black shows areas of high resistance and white represents low resistance i.e. ditches.

The third expedition came about as part of a geophysics training day that I ran at the YDNPA office for interested local archaeology groups. After a session in the classroom, we carted the magnetometer and earth resistance kit up a small, nearby hillock (fig. 3). This hillock, overlooking Bainbridge’s well-known and conspicuous Roman fort, has a wonderful view over Wensleydale, a convenient position beside the River Bain and a pronounced ditch and slight bank encircling the plateau on the top. Unfortunately for the purposes of geophysical survey, this plateau is bisected by a large dry-stone wall topped with wire fencing, and several mature trees. The site is referred to in the HER as a probable ‘univallate hillfort’, although it seems this is purely on the strength of the earthworks, so besides being convenient, the site was also of potential archaeological interest. The participants did a great job of surveying half the internal area of the enclosure… and found the encircling ditch showing up well in the earth resistance data (fig. 4), with nothing in the way of internal features in the magnetometer data. With any luck, the other half will be surveyed shortly, but in the meantime it looks like the best interpretation might be as a stock enclosure!

 

Part of the magnetometer data from Giggleswick. The suspected training trenches show up clearly as the pale zigzag (though there also appear to be some positive anomalies associated with the structure). Strong, discrete black and white anomalies indicate responses to ferrous sources. Data displayed at +/-5nT, black positive; area approx. 40 x 20m.

Fig. 5 Part of the magnetometer data from Giggleswick. The suspected training trenches show up clearly as the pale zigzag (though there also appear to be some positive anomalies associated with the structure). Strong, discrete black and white anomalies indicate responses to ferrous sources. Data displayed at +/-5nT, black positive; area approx. 40 x 20m.

Most recently, as part of the YDNPA Training and Trenches project, a survey of 2 suspected WWI training trenches was undertaken. The trenches, on the hillside overlooking Giggleswick School, Craven, may have been dug and used by the school’s Officer Training Corps. Alongside building survey of the Drill Hall at Settle, and earthwork survey of the firing range at Attermire Scar, the trench site was previously subjected to plane table survey by eager volunteers. Poor site conditions mean that the magnetometer data (fig. 5) isn’t as good as it could be, but it is certainly good enough to locate the suspected trenches – the well defined white zig-zags! It is interesting as, rather than having been backfilled with magnetically noisy rubble, they have been detected as less magnetic than the surrounding soil – perhaps containing wooden shoring or voids? Whereas in most archaeological geophysical surveys the strong ferrous signals (the discrete, black and white blobs!) would be considered as modern debris and therefore interference, in this situation they may well represent bits of the relevant archaeology that we are looking for. As part of the project, the trenches are being excavated in late June 2014, which will provide a great opportunity to compare the archaeological record with the geophysical results…DSC_1042 copy 2

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