Dimensions and chronology of the last ice sheet in Western Ireland

On the mountains of Western Ireland, the upper limit of glacial evidence descends from 730 in in the Connemara Mountains to 400 111 on Achill Island. This limit is interpreted as a trimline marking the upper limit of erosive, warm-based ice, implying that higher summits remained above a former ice sheet as nunataks or supported a cover of cold-based ice. Significantly greater representation of gibbsite in soils above the trimline indicates that it relates to the last glacial stage. Be-10 exposure ages for bedrock samples above the trimline fall within the range (>) 36.0 +/- 2.3ka to (>) 61.6 +/- 4.0 ka, whereas ice-scoured bedrock below the trimline yielded Be-10 exposure ages <= 24.0 +/- 1.6 ka (and in all but two cases <= 17.2 +/- 1.1 ka), consistent with deglaciation after the LGM. Reconstruction of the minimum altitude of the LGM ice surface implies that inland ice was diverted northwestwards by an ice dome on the Connemara Mountains and extended at least 25 kin offshore. This evidence conflicts with previous accounts that place the LGM ice limit onshore and implies that recent models underestimate LGM ice thickness in Western Ireland. (C) 2007 Elsevier Ltd. All rights reserved.