Excavation and survey at Loch Bhorgastail, Isle of Lewis, Outer Hebrides (July 2023): Interim report

Abstract

Following on from previous surveys carried out in 2016 and 2017 and more substantial excavation in 2021, a final season of work was undertaken on and around the crannog in Loch Bhorgastail (Figure 1) during July 2023. This involved terrestrial and underwater excavation, coring of the loch bed and photogrammetric Uncrewed Aerial Vehicle (UAV) surveys.

On the surface of the island, following initial clearance of a larger quadrant, a 2.50 x 1.00 m trench was excavated at the centre of the stone islet exposed above water. This trench revealed further evidence for Middle Bronze Age activity and well-preserved Early Neolithic timber architecture (including wattling and glimpses of the site’s primary basal timber ‘platform’). A small amount of Early Iron Age activity (previously unseen on the islet) was also identified. Excavation of the terrestrial trench had to end, due to water ingress, at c. 0.60 m below loch level.

Adjacent to the stone islet, our 2021 underwater trench had revealed an extensive spread of laid timbers; in 2023, this trench was extended both horizontally and vertically. Close to the above-water stone islet, it was extended further to the NW (i.e. in towards the islet), allowing us to join up the ‘underwater’ and ‘terrestrial’ stratigraphy as a whole. A small sondage was also excavated close by, through the uppermost laid timber layer, revealing further timbers (2-3 logs thick) below it; these had ultimately been placed directly on top of loch bed silts, demonstrating that the timber platform had been constructed in a wet, lacustrine environment. At the other end of the trench, furthest from the stone islet, the trench was extended to the SE, revealing the full spatial extent of the laid timbers, which ultimately extended 7.5 m out from the stone islet edge.

Alongside this excavation work, coring of the loch bed was undertaken in order to assess further the site’s potential for sedaDNA and to enhance understanding of the extent of the timber platform around the stone islet. Multiple UAV surveys were also undertaken to build a topographic model of the site and to record successive stages of excavation.

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Identifiers

ORCID for Stephanie Blankshein: orcid.org/0000-0002-4622-9180

ORCID for Fraser Sturt: orcid.org/0000-0002-3010-990X

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