County: Mayo Site name: RATHROEEN LOUGH, Rosserk
Sites and Monuments Record No.: SMR 22:80 Licence number: 02E0867
Author: Richard Gillespie
Site type: Crannóg
Period/Dating: Early Medieval (AD 400-AD 1099)
ITM: E 523238m, N 824069m
Latitude, Longitude (decimal degrees): 54.159863, -9.175329
The Ballina Landfill is encroaching on the southernmost one of three possible crannogs that coincide with the three small islands in Rathroeen Lough. Testing established that it is a crannog, and measures for its preservation are being discussed with the relevant bodies.
The site consists of a raised area, which had been an island at the centre of Rathroeen Lough before it was drained in the early 1960s. The surface of the site consists of a flat platform, almost circular, with a diameter of 18–19m. The sides slope quite steeply to marsh/scrub and reed beds and appear to be regular.
Two 1m-wide trenches were opened across the site, running north–south and east–west, and were excavated until definite archaeological material was encountered. The upper layer was very rooty, with a large amount of modern rubbish. It rested on a sterile, mid-red/brown, plastic clay layer, up to 0.8m thick, within the crannóg and on an accumulation of stones at its perimeter. This layer rested on and around a deposit of limestone boulders, mostly rounded and with weathered surfaces. These boulders overlay a mottled, yellow/mid-brown clay that was exposed but left intact. A small deposit of poorly preserved cockle shells was identified on the surface of this layer and was probably archaeological. Lenses of ash, charcoal-stained silt and some bone were also identified at this level.
The perimeter stony layer was identified in the outer 5–6m of the crannóg in the north, east and west of the site. It is likely to occur to the south, but the test-trench did not extend that far. It consisted of an outer dump or bank of boulders and loose cobbles. This may be an enclosing element or may have acted as a solid outer face to the crannóg, which continued to its base, giving it a height of 1.5m. This feature was exposed but not excavated. A corroded iron object, possibly a pin, was retrieved from the upper levels.
In addition, a dugout canoe discovered in the lake in 1962 was radiocarbon dated in 1991 by the National Museum of Ireland, producing a date of 410±30 BP. This may be an indication of the date of the crannog.
Westport Road, Castlebar, Co. Mayo
