The immediate landscape around the Loch of Yarrows is a predominantly wetland one with sedge mires found to the east and moist Atlantic heather with blanket bog to the south and west. Extensive blanket peat is to be found beyond the western margins of the loch. The area around the Loch of Yarrows is particularly rich in prehistoric sites including Mesolithic blade scatter sites, well preserved Neolithic stone rows and burial cairns, Bronze Age hut circles, an Iron Age Broch, at least one crannog, and some evidence from the Pictish period including a cist (c.300-800 AD).
Since the mid-1990s GPR equipment has improved and its applicability within Scottish wetland sites has hitherto been largely unexplored. The recognition that GPR survey works on terrestrial archaeological sites is well known but the potential of GPR to rapidly identify buried archaeological sites under peat has yet to be explored in as greater detail owing to technical problems.
The GPR survey at Loch of Yarrows environs was carried out over a single weekend to allow members of the Caithness Field Club and Yarrows Archaeological Trust to take an active part in the fieldwork. The survey was carried out at locations that were deemed the most profitable and to provide positive results within the given time frame.
Five sites were selected following a preliminary site appraisal that included depth probing with a 15mm diameter stainless steel peat probe to establish the relative depth of the basal morphology at each respective site. These were designated Olicate A and B, South Yarrows 1 and 2, and Swartiburn.
The grids Oliclate A and B were both located on a flat area of ground at c. 150m OD. The ground falls eastwards with fairly shallow gradient down to the metalled trackway leading to Oliclate Farm and was covered in swards of grass and low stands of ling heather. The site is flanked on the south side by an area of scrubby ground about 1m lower than the grid sites. The vegetation is dominated by sedges and scrubby heather typical of an area of peat that is regenerating after being cut for fuel, probably by tenants of Olicate Farm. The site has been burnt in the last ten years according to the landowner (Islay McLeod pers comm). On the north side of the site there is a small burn that runs under the track, the burn forms a boundary between the survey area and an expansive area of rough grazing land. Downslope from the study area the land is undulating and very marshy in places with small, slow water courses that drain towards the Swartigill Burn.
The area to the south of Loch of Yarrows (hearafter south Yarrows) is predominately a wetland one with sedge mires found to the east and moist Atlantic heather with blanket bog to the south and west. The local topography is very irregular and rises steeply south westwards towards Warehouse Hill. Immediately to the south of Loch of Yarrows there is a plateau below the 100m contour overlooked by a sandstone ridge that forms a distinct feature in this area. On top of the ridge there is a line of later prehistoric hutcircles that are covered in heather but still visible and are part of the Loch of Yarrows Archaeological Trail. These features lie within a Scheduled Area. The Site of South Yarrows 1 was selected because it was fairly level and free of dense heather cover. A clearance mound or possible archaelogical feature lay close to the grid site. South Yarrows 2 lay approximately 400m south-west from Yarrows Site 1 and was located in a shallow cleft between two small knolls. The topography is characterised by a small basin with gentle slopes within which lies a small channel feature that slopes down to a very wet and marshy area on the edge of a mire; the ground is covered in heather.
The site of Swartiburn lies about 1.5km to the north east of Loch of Yarrows and was selected as part of the study owing to the presence of known archaeological remains within a flat area of alluvium alongside the burn of the same name. The extent of the structural remains are not known and it was hoped that the result of the GPR survey would shed light on the extent of the remains, as well as test the effectiveness of the GPR equipment over a different soil regime. The burn drains a large area of marsh and fields associated Oliclate Farm and eventually flows into Loch Hemprigs. The survey area rested on an alluvial plateau formed between two former river terraces. The area has a history of probable medieval settlement with run-rig field systems and field banks that have been mapped during a survey carried out by members of the Yarrows Archaeological Trust. More or less in the middle of two farmsteads and exposed on the north facing side of the stream is an assortment of building remains. The principal features comprise two possible drystone walls measuring up to 0.6m in height and 11m apart, retaining between them a mass of small boulders, slabs and stones. Within the mass there is a structure resembling a small cist or culvert built of slabs and extending back into the face of the eroding bank. |
