Mine Howe Geophysical Survey and Excavation

Date 1999

Event ID 1167913

Category Project

Type Project

Permalink http://canmore.org.uk/event/1167913

HY 5105 0603 In the late summer of 1999, local farmer Douglas Paterson rediscovered an underground structure which had originally been found in 1946. Since its initial discovery the site had almost been forgotten apart from a brief mention in the SMR.

The chamber comprises a series of steps that descend to an intermediary landing that has two side chambers off to one side. A further flight of steps lead down to a chamber c 1.5m in diameter with a corbelled stone roof rising to c 4m above the flagged stone floor. The floor of this chamber is c 7m below the top of the glacial moraine into which it was built. Most of the structure is lined with drystone masonry. The Royal Commission surveyed the site in November 1999, resulting in a plan, a section through the chamber, and a contour survey (see this volume, p 106).

GSB Prospection was commissioned to do a geophysical survey, utilising magnetometry, resistivity and ground-probing radar (GPR). The results of this showed that a large ditch, c 7m wide, 50m in diameter, and with a clear break/entrance on the NW side, surrounded the mound. Concentric to this ditch was a series of what appeared to be subsidiary gullies and ditches at intermittent points around the mound. Evidence for settlement-type activity occurred both in and around the entrance across the main ditch. GPR indicated the possibility of other chambers existing within the mound.

Due to a series of agricultural threats, the uniqueness of the structure, and the need for a better understanding of the site prior to Scheduling, excavation was started in the early summer of 2000. The main aims of the project were to evaluate the nature and date of the features revealed by geophysics and to look at the relationships between these various elements and the underground chamber. Four main trenches were opened.

Trench A was located across the main ditch opposite the entrance to look at the relationship of this ditch to two of the subsidiary outer gullies/ditches. Excavation revealed that the ditch here was c 5m wide by 2.5m deep with a sharp U-shaped profile. The ditch had been deliberately infilled with a series of midden and rubble fills that probably represent several different phases. Finds from these fills include Roman glass, a fibula brooch and Middle to Late Iron Age pottery. Within, and probably contemporary with the ditch was a paved area, c 2m wide, which may have extended around the mound. This paving was set on a platform cut into the mound and had a revetting wall along the back of it against the mound. Once the ditch had been infilled the paving was extended to partially cover the ditch. In an extension to this trench, to the SW, the paving and revetting had been extended to form a semi-circular platform/'alcove' cut into the mound. The gullies suggested by geophysics outside the main ditch proved to be illusory. These features were created by a series of anthropogenic soils built up against the sides of the mound. A 1m wide slit trench was extended from the NW end of this trench up to the opening of the underground chamber, to examine the relationship of the ditch to the chamber and to determine the presence of any structure on top of the mound. Glacial boulder clay was encountered directly under the topsoil. This may have been partially redeposited to enhance the height of the mound, but concerns over destabilising the underground structure prevented further investigation.

Trench B was located over one of the main ditch terminals. This revealed a ditch up to 7m wide and 4m deep with a flat-bottomed U-shaped profile. The earlier phases of the ditch were associated with at least three different phases of revetting of the terminal. The later phases of revetting included a widening of the entrance causeway and a partial infilling of the ditch with rubble. The upper ditch fills contained much more midden material. This contained a large element of metalworking debris which probably originated from some ephemeral structures at the NW end of this trench and those uncovered in Trench E. Latterly these midden deposits were partially paved over before the ditch was totally infilled. As in Trench A, a 1m wide slit trench was extended from the SE end of the trench over the mound towards the present entrance to the underground chamber. This revealed a shallow linear feature and the edge of a small cist-like structure. This trench was further extended to totally uncover the cist, which was filled with a dark, charcoal-rich fill and a small amount of cremated bone.

Trench C was located over two anomalies revealed by geophysics; an apparent circular enclosure cut by or cutting one of the subsidiary gullies/ditches. On excavation neither feature was detected. Instead, 1m of anthropogenic midden-rich soils overlay a series of gleyed clay deposits over 1m thick. The interpretation of these deposits awaits the analysis of soil samples.

Trench E was located over the apparent settlement area outside of the causeway across the main ditch. Under a series of rubble and midden spreads a lobate Late Iron Age structure was uncovered in association with some very ephemeral features. This structure overlay an earlier, larger structure, probably a roundhouse. These structures were separated from midden-enriched soils to the N by the remains of a field boundary stone dyke. Middens associated with these structures produced a large range of industrial waste including moulds, slag, furnace linings and evidence for bone and antler working. In the SE corner of the trench a section of bank was revealed composed of redeposited natural. This may be an external bank to the main ditch that surrounds the mound.

Trench F was dug by machine in an area identified as being clear of archaeology and was intended for the disposal of the waste from the chemical toilet. However, at a depth of c 1.3m beneath a series of anthropogenic soils, a deposit of cremated bone and charcoal was revealed. It is at present not clear whether the bone is human or if the horizon in which it was found is a soil or deposit. Under this were clay deposits similar to those at the bottom of Trench C.

Although the underground structure had been extensively emptied in 1946, in situ deposits were identified in the middle chamber. This ashy midden was sampled and was also found to contain both native Iron Age pottery and a sherd of coarse Roman ware.

Sponsors: Historic Scotland, Orkney Islands Council, Orkney Enterprise, Orkney College, Time Team, Orkney Archaeological Trust.

N Card, J Downes and J Gibson 2000