A DIATOM AND POLLEN RECORD FROM CONNEMARA, WESTERN IRELAND: CONSTRAINTS ON HOLOCENE AND LATE GLACIAL SEA LEVEL

Current glacio-hydro-isostatic models for Ireland appear to contradict apparent geological and geomorphological evidence of the position of sea-level in Western Ireland, particularly in Connemara. Models predict maximum ice thickness of the British and Irish Ice sheet at the time of the Last Glacial Maximum would have been relatively thin (600m) and relative sea-level would not have risen above present after the deglaciation. Contrary to this, the interpretation of geological and geomorphological evidence suggests maximum ice thickness would have reached 2000m and late glacial relative sea-levels would have been higher than present due to substantial isostatic adjustment. Diatom and pollen analyses provided a means of dating and establishing a salinity history of sediment retrieved from Loch Fhada, a potential isolation basin in Western Ireland. The dominance of the diatom assemblage by oligohalobous species suggests that the basin was freshwater, the pollen profile confirms that this was during the late glacial. The implications of this are that regionally high sea-levels could not have been in place during the late glacial and place late glacial sea-level below 1.3m lOD. The diatom data provides a constraint on early Holocene and late glacial sea-levels which were most likely to have been in the region of 25 to 40m below present.Faculty of Scienc