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Cairn Merk

Broch (Iron Age)

Site Name Cairn Merk

Classification Broch (Iron Age)

Alternative Name(s) Carn Na Mairg; Westerdale

Canmore ID 8358

Site Number ND15SW 22

NGR ND 1331 5103

Datum OSGB36 - NGR


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Administrative Areas

  • Council Highland
  • Parish Halkirk
  • Former Region Highland
  • Former District Caithness
  • Former County Caithness

Archaeology Notes

ND15SW 22 1331 5103.

(ND 1331 5103) Cairn Mairg' (Brough) (NR) Fosse (NR)

OS 6" map, Caithness, 2nd ed., (1908)

A broch known as 'Carn na Mairg' is situated on the E bank of the River Thurso about half a mile S of Westerdale. It is a conspicuous, grass-covered mound rising from the water's edge and cut off from the moorland by a well-defined ditch opening on the river bank, wet in the bottom and filling when the river is in flood. This ditch measures some 22ft in width on the SE and about 15ft on the NE. From the top of the parapet which crowns the scarp it is from 8 to 10ft deep, but its depth from the top of the outer bank is only 2 to 3ft. Towards the E the continuity of the ditch is broken by the approach to the broch which crosses on the solid and is 6ft wide where it passes through the enceinte. On either side of this approach as it crosses the ditch, the foundations of a wall are visible beneath the turf, and beyond it on the moorland two parallel mounds or ruined walls exist for a distance of some 50ft, 24ft a part and measuring 17ft across at base, indicating the direction of the road, inclining obliquely towards the entrance. Between the ends of these flanking mounds and the ditch, an old road now interposes. The parapet wall on the top of the scarp has been some 4 to 5ft in thickness, and has been carried entirely round the broch. Between it and the base of the tower has been a level space some 30ft in width over which numerous flagstones set on end protrude from the turf. The outer end of the entrance passage of the broch has been exposed to a height of 2ft 3ins, as also the inner end, while in one or two places on the exterior small portions of wall are visible. The entrance has been from the E through a passage 10ft 6ins in length, 3ft 4ins wide at the exterior, and 2ft 4ins wide at the interior extremity. The outer lintel has gone, but the succeeding four remain in situ, roofing the passage for 8ft of its length. No guard chamber or door jambs are exposed. The overall diameter is about 52ft. The greatest height of the mound is 8ft above the level of the passage floor. A depression in the top marks the court.

Visited by OS (E G C) 11 April 1962.

The remains of the broch are generally as described by the RCAHMS. Attempts at excavating have taken place on the E side, and here the outer wall of the broch is exposed for a distance of 3.5m and a height of 2.4m. Above the wall and to the W, a chamber is exposed; it is 2.0 by 0.9m and 0.6m deep at present. To the NE of the wall another short section of wall is now visible, probably part of the parapet wall which extended round the top of the scarp of the ditch; this wall is 1.1m high.

There are two modern causeways over the ditch on the NE side, both similar to the entrance causeway, but varying in width, being 1.7 and 1.5m wide respectively. On the SE side of the ditch and in line with the entrance to the broch are the remains of the entrance causway, now 0.3m high above the base of the ditch.

Only one of the flanking mounds indicating the approach road is now evident, the second mound no doubt having been destroyed when the new road which now skirts the site was constructed.

The broch's surrounding ditch has been largely destroyed on the SE and S sides by modern drainage.

Resurveyed at 1:2500.

Visited by OS (E G C) 11 April 1962.

(ND 1331 5103) Cairn Merk (NR)

OS 6" map, (1963)

Cairn Merk or Carn na Mairg: a broch generally as described. The 'chamber' noted in the previous field report is a section of mural gallery. The two later causeways are of neatly coursed slabs and upstanding whereas the original causeway is low and turf-covered, only the line of the W edge being clear. The walls flanking the approach from the causeway to the broch entrance are checked 3.5m distant from the broch. There is no evidence of a flanked approach beyond the causeway; the mound or mounds mentioned are natural or in part spoil.

Visited by OS (J M) 11 November 1981.

'Broch', Carn na Mairg. Subcircular grass-covered mound, the outer wall exposed on the E flank. Above it a section of the mural gallery 2 x 0.9 x 0.6m is evident. It is surrounded by a ditch crossed by three causeways, two of which are modern.

[On opposite river bank from ND15SW 22]: Structure (ND 1321 5102). Dimensions: 6 x 5.2m. Rectangular structure in ruinous condition. ['Remains of fosse'is marked at this location on the first edition of the OS 6-inch map (Caithness 1876, sheet xxii), but nothing is marked on the current edition of the OS 1:10,560 map (1963) except for a nearby modern drain. - Information from RCAHMS (FO) 21 August 1996]

R J Mercer, NMRS MS/828/19, 1995


Publication Account (2007)

ND15 9 CARN NA MAIRG ('Cairn Merk', 'Westerdale 1')

ND/1331 5103 (visited 14/7/63, 12/7/85 and 4/8/02)

Partially excavated broch, probably solid-based, on flat moorland in Halkirk, Caithness, and next to the river Thurso; it stands on a flat artificial platform and is surrounded by a damp ditch which seems originally to have been connected with the river at each end, forming a moat. The site is a conspicuous mound and has been explored by a long trench on the south-east side which runs from the outer end of the entrance to the inner face of the outer wall. From about 3.30 to 5 o’clock the outer wallface has been cleared of debris and exposed, and a section of the upper intra-mural gallery above this has also been cleared out for about half of this length. This was all done after the Commission’s visit in 1910 and the author was told in 1963 that Mr Murray Threipland, the then landowner, did the work about six years earlier (the remains of the neatly cut trenches indicate some familiarity with modern archaeological techniques). Spoil heaps from his clearances are marked on Swanson's plan beyond the ditch [3].

The broch stands a few feet above the surrounding flat moorland on what seems to be a raised artificial platform; this has a masonry wall running round its perimeter so that there is a flat terrace between the broch and the edge of the platform. A ditch 6.7m (22ft) wide surrounds the mound, ending at the river bank; it was probably originally a moat filled by the river, and – even though obviously nearly full with silt – is still apparently flooded when the river is high. Swanson reports modern drainage ditches leading from each end of the old ditch to the river [3]. There are no signs of an outer bank.

Three narrow stone causeways cross the moat – a feature not known elsewhere. One of them is in line with the entrance on the south-east and seems to be older than the rest, being low and turf-covered; if it is of Iron Age date it should have an opening in its lower part to let the water of the moat through. The other two causeways have vertical sides of drystone masonry and are on the north-east side. They are usually described as modern and Swanson suggests that they were built by Murray Threipland to help remove excavated stone from the site [3]. This seems highly probable.

The main entrance is on the south-east and the outer and inner ends were already partly exposed in 1910 so that its lintels could be seen [2]. Although the Commission stated that the outer one had gone [2] they all seem to be in position now so the front one may have been replaced. The Commission gives the entrance a length of 3.20m (10ft 6in) but the wall nearby is now more exposed because of the trench dug in the 1950s and can be seen to be nearer 3.6m (12ft) thick, taking into account the visible batter on the outer face. The width of the passage is 1.0m (3ft 4in) at the outside, and there are no visible signs of door-checks or of a guard cell. Rubble fills the passage now, apparently blocking it to a greater extent than in 1910 when 2.4m (8ft) of lintelled roof was visible [2]. No guard chamber or door-checks were exposed then and none are now. Also exposed by the recent excavations was a secondary outward extension of the entrance in the form of a passage containing door-checks.

Another recent, and wider, trench has been dug some distance anti-clockwise from the entrance, running from the outer rampart – exposing its inner face – up to the broch wall – where the battered outer face is exposed – and over the wallhead itself. There it has exposed a short length of a mural gallery 60cm (2ft) deep. This latter must be the first tier of what was once a series of raised galleries on top of a solid wall base. There is no sign of its floor being of lintels, which would be the case if there was a ground level gallery below.

The space between the outer wall and the mound is about 9.0m (30ft) across and there are signs of outbuildings under the turf [3, plan].

The whole site is an exceptionally interesting one in that it provides a typical example of a Caithness broch on its own mound surrounded by wall and ditch and with a presumably secondary settlement clustered around it, the whole now in complete isolation and relatively un-disturbed. It also shows how easily a true hollow-walled broch can be detected in this area with a trench over the wallhead. The height of the base of this gallery must be at about the level of the roof of the entrance – that is about 2.0m above the Iron Age floor; this is a lot less than the wallhead at Crosskirk (ND07 2) where no Level 2 gallery was found. The surrounding waterlogged ditch should offer an unusual opportunity for recovering organic remains and the peat-covered flat land round about might conceal an Iron Age field system. The site is one of the most promising in Caithness and well worthy of a full-scale excavation.

Sources: 1. NMRS site no. ND 15 SW 22: 2. RCAHMS 1911b, 33, no. 105: 3. Swanson (ms) 1985, 672-75 and plan.

E W MacKie 2007

Photogrammetric Survey (31 October 2018 - 1 November 2018)

ND 1332 5103 A detailed survey was carried out of Carn Ma Mairg broch (Canmore ID: 8358), also referred to as Cairn Merk, as part of the planning condition for the Achlaclan Wind Farm, Caithness, and took place on 31 October to 1 November 2018.

The broch is built on a slightly elevated platform on the east bank of the river Thurso and is enclosed by a ditch that runs into the river at both ends. It has an outer courtyard that appears to run around the entire broch and an external passage leading up to the entrance to the SE. The surveyed profile indicates that the walls survive to a height of some 4m above the original ground surface.

Archive: NRHE (intended)

Funder: Achlachlan Wind Farm LLP

Magnar Dalland - Headland Archaeology (UK) Ltd

(Source: DES Vol 20)


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