South Walls mound is a chambered cairn

The outer revetment wall. (ORCA)

Archaeological excavations on a large mound in South Walls suggest that, contrary to a long-held assumption, it does not contain a broch. Instead, it is a Neolithic chambered cairn.

A two-week excavation of Outer Green Hill, adjacent to the road leading to the Cantick lighthouse, drew to a close on Saturday. Excavation supervisor was Dan Lee, from the Orkney Research Centre of Archaeology (ORCA), based at Orkney College.

He explained: “The project continues the work of the late Judith Robertson, who undertook an archaeological landscape survey of the area in 2006 and then conducted targeted geophysical surveys of the main features last year.

“Outer Green Hill was interesting as it did not display the geophysical responses typical of a broch – large outer ditches, associated settlement and circular internal walls. The geophysics results suggested a squared internal structure, perhaps more indicative of a Neolithic tomb, a period only represented by the Dwarfie Stane, in North Hoy, or a Norse stronghold, as the area is mentioned in the sagas.”

The aim of the dig was to characterize and date the site.

“A trench excavated from the top of the mound, down the southern side, revealed two internal corbelled wall faces, just over one metre apart, that appear to form an internal passage orientated east to west,” said Dan.

Picture: ORCA

The central passage. (ORCA)

“It appears to form the central passage of a Neolithic chambered tomb. Corbelled internal walls, where the walls gradually taper inwards, towards the roof, are more typical of Maeshowe-type tombs. Waterworn beach slabs have also been used in the internal wall faces, in the same way as at the Quoyness chambered tomb, in Sanday.

“The hollow visible in the top of the mound has been confirmed as resulting from previous excavations, however it seems that no record of this was made and they were probably conducted in the mid 19th century. The loose upper backfill of the passage contained several pieces of pottery dating to the Neolithic, although this awaits specialist conformation.”

These pottery sherds may have been disturbed from lower deposits during the previous excavation. Other finds included animal bone and a quartz scraper, found in the topsoil.

The structure of the external mound, to the south, consists of a solid wall-like core, with an external revetment wall that slopes inwards, and which survives to over one metre in height.

Dan said: “Although it is possible that the passage represents an internal feature of the outer wall of a broch, rather than the central passage of a Neolithic tomb, the pottery and character of the masonry clearly point to a Neolithic date.”

A second trench was opened to attempt to locate further structural stonework and place the central passage in context and perhaps locate an entranceway.

Dan concluded: “The excavations have certainly demonstrated the high significance of the mound within the rich archaeological landscape of the Cantick peninsula and indicated a probable Neolithic date. This is important for the archaeology of South Walls and the distribution of chambered tombs throughout Orkney as a whole.”

The project was funded by Orkney Islands Council. The excavation team was: Dan Lee, Naomi Woodward, Gemma Mutch, Sandra Christen and Gavin Lindsay.

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