Crannog

The National Monuments Service's description

This crannog is shown on the 1838 and 1922 OS 6-inch maps as an island located roughly in the centre of Rathroeen Lough. The lake was drained in the 1960’s and reverted to marshy scrubland. A Mayo County Council landfill site covers an extensive area immediately to S of the crannog. Two possible crannogs (MA022-080001-; MA022-080002-), shown as islands on the 1929 OS 6-inch map, are located c. 100m to N.
This crannog is evident as a roughly circular, flat-topped platform (diam. c. 18–19m; H 1.5m), with relatively regular sides which slope quite steeply into the surrounding scrub and reed beds. Test trenching (02E0867) was carried out in 2002 to assess the significance of the site which was under threat from a planned expansion of the County Council Landfill (Gillespie, 2002). Two perpendicular trenches (Wth 1m) were opened, extending N–S and E–W across the site. When an upper layer of sod, clay and modern rubbish was removed, a layer of mid-red/brown clay layer, up to 0.8m thick was revealed. This layer rested on, and around, a deposit of limestone boulders, mostly rounded, with weathered surfaces. The boulders overlay a layer of mottled, yellow/mid-brown clay. A small deposit of poorly preserved cockle shells was identified on the surface of this layer. Lenses of ash, charcoal-stained silt and animal bones were also found at this level. Around the perimeter of the platform an encircling accumulation/bank (Wth 5-6m) of stones and boulders was exposed, but not excavated. It may be an enclosing element or may have acted as a solid outer face to the crannog.
A corroded iron object, possibly a pin, was retrieved from the upper levels. A dugout canoe (Nat. Mus. Reg. no. 1A 153/62) was discovered in 1962 c. 80-100m NE of the crannog; It produced a radiocarbon date of 410±30 BP. This may be an indication of the date of the crannog. (Gillespie, 2002).

Compiled by: Jane O’Shaughnessy

Date of upload: 3 May 2019

References

Gillespie, R. 2002 Rathroeen Lough, Rosserk Crannog. 1407. In. I. Bennett (ed.), Excavations 2002: summary accounts of archaeological excavations in Ireland. Bray. Wordwell.