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Excavation

Date 26 August 2011 - 17 September 2011

Event ID 963747

Category Recording

Type Excavation

Permalink http://canmore.org.uk/event/963747

NC 26243 11189 Loch Borralan East Chambered Cairn was excavated by volunteers led by AOC’s John Barber between 29 August–17 September 2011. The chamber had previously been cleared by Alexander Curle in 1909; Audrey Henshall (1963) categorises it as being in the Orkney-Cromarty group, and suggests that it may have had horns protruding on the SE and SW sides. This monument had been selected for investigation as it is a type site for the area and because we believed that its soft deposits had been removed by Curle, allowing us to concentrate on its architecture and engineering.

Our excavations revealed that the polygonal chamber had been built onto the top of a small crag and tail bedrock feature. The top of the crag had been quarried roughly level and the tail, to the W of the chamber had been quarried away to allow for a roughly symmetrical sweep of the cairn around this side of the monument. The extension westwards is what Ms Henshall, and this writer, had imagined might be evidence for a hornwork. Entrance was from the E with a passageway believed to extend somewhat to the SE.

No archaeological deposits were found within the chamber and it seems probable that these were removed by Curle's excavations. The chamber itself had been constructed from large quarried slabs of Syenite, a granite-like rock type (but with no quartz) and a pink to red appearance (from the Feldspar) when fresh. The surfaces of these large slabs had been dressed to rough planarity and flake scars can be seen on three in particular. Examination of the spoil tips revealed the presence of quartzite or a crypto crystalline quartz-like stone of great density and hardness. A simple on site experiment showed that this was easily capable of working the surface of Syenite blocks. Some of this material was found in pencil-shaped prismatic fragments, one end of which had been brought to a rough point and the tips of which were broken.

The entrance area was stripped of peat and small stones in and over the peat, the latter being attributed to Curle’s excavation work in 1909. Under these lay an entanglement of very large stones, weighing 300–500kg. These could not be removed by hand without damaging the monument, and were left in place. It was nonetheless clear that this monument has an antechamber, a possibility recognised by Henshall.

Excavations into the cairn material beyond the ante chamber revealed the slightly concave, frontal façade of this D-shaped cairn. A low extension beyond the main façade wall was divided by a narrow entrance passage, which terminates at two low but relatively massive entrance portals of Salterella gritstone. Between them the entrance to the antechamber is choked with densely packed stones in a soil matrix which is peat-free. It is clear that Neolithic deposits survive within the antechamber. It is possible, indeed probable that some of the very large slabs now choking the ante-chamber formed part of an ornate, polycope façade and the others are roofing slabs of the antechamber.

Two long cuttings were dug from the chamber out past the cairn edge on the S and W sides of the monument. These revealed the expected polycope walls, three full walls and a plinth wall on the outermost circuit. The innermost wall face is in fact the outer face of the core cairn within which the chamber was built; it is 1.6m wide at the revealed height, near the top of the chamber.

Archive: RCAHMS (intended)

Funder: Historic Scotland; Highland Leader+ and Heritage Lottery Fund

AOC Archaeology Group, 2011

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References