1998 CFA resistivity survey block B

Date October 1998 - October 1998

Event ID 568821

Category Recording

Type Earth Resistance Survey

Permalink http://canmore.org.uk/event/568821

NS 6865 7525 - NS 6918 7552 The line of the Antonine Wall has been confirmed between Shirva Farm and Wester Shirva through a programme of geophysical survey and trial excavations. These works were undertaken as part of Historic Scotland's review of the Scheduling of this monument.

Sponsor: Historic Scotland

B Glendinning 1998

NS 687 752 to NS 690 755 Geophysical survey in heavily waterlogged ground designed to establish the alignment of the Wall more precisely, suggested that it lay N of the position marked on the OS sheets. The ditch was located in three separate points between the farms of Shirva and Wester Shirva. It appeared to have a width of 6m -7m. In one trench, traces of an upcast mound survived N of the Ditch. Subsequent excavation (in January 1999) in advance of possible sewerage works allowed the alignment to be further corrected. The Ditch was shown to be c.8m wide; core samples of its fill were removed for analysis.

L J F Keppie 1999.

NS 688 754 Three separate evaluations took place between 1998 and 2001 along the Antonine Wall between Wester Shirva and Shirva Farm, including the crossing point of the Board Burn.

First, in October 1998 geophysical survey and trial trenching were conducted between Wester Shirva and Shirva (NS 6865 7525-NS 6981 7552). These results had not confirmed the crossing point of the Board Burn by the frontier works, and several different alignments were possible. The geophysics depicted an anomaly representing a large ditched feature. Trenches were placed to examine these anomalies, which proved to be the Ditch. The second trial trenching evaluation was undertaken in January 1999 to confirm the line of the Ditch just to the E of the Board Burn (at NS 6885 7542). The Ditch had a surface width varying between 6m and 8m. The Ditch edges were steep sided although they became noticeably shallower towards the surface. A core was taken through the centre of the Ditch in order to characterize the nature of the deposits and to determine their palaeoenvironmental potential. The core sample was not subject to detailed palaeoenvironmental analysis. Putative remains of the Outer Mound were identified along the northern lip of the Ditch in one of the trenches. No further archaeological features of any kind were located.

Finally, during 2000 and 2001, a watching brief was undertaken on sewer construction works. As part of this exercise, a third evaluation was undertaken a Shirva. The objectives of this work were to determine the location of the Ditch and assess the degree of compression of the underlying sediments. Excavation here revealed a feature, which has been interpreted as a natural palaeochannel masked by subsequent inorganic flood deposits.

Overall, the results from this work have allowed the alignment of the frontier works to be better understood in this area. To the W of the Board Burn, the Ditch alignment was confirmed substantially on its previously extrapolated alignment. To the E of the burn, however, it appears that the frontier alignment lies to the S of its previously mapped position, either within the grounds of Shirva Farm or beneath the road. It is notable that the Ditch forms a straight alignment to either side of Board Burn, unlike the kinking route which had been proposed formerly. The presence of peat fills within the Ditch is of importance because of the potential of such deposits for the undertaking landscape and land-use reconstruction through pollen analysis.

Extrapolation of the opposed Ditch alignments confirmed to the SW and NE of the Board Burn indicates that the Ditch should have crossed the SE end of Trench 10, but it is absent. One possibility is that the Ditch had never been constructed across the alignment of the burn. However it has been argued that a lack of a Ditch may be too great of a potential weakness across the frontier line. A second possibility is the Ditch alignment is kinked southwards slightly for a short distance on both sides of the burn, to create a re-entrant angle providing additional protection to any gap the frontier works at the burn crossing.

No consistent trace of the Outer Mound was located. There was no evidence for defensive pits on the Berm, although most trenches did not extend S of the Ditch. No remains of the Rampart were identified at this location. No evidence for the proposed fortlet was recovered, though work did not cover the areas best suited to the siting of one. No evidence relating to the souterrain (see NS67NE 13) was recovered.

A Dunwell, G Bailey, A Leslie, A Smith 2002.