Upper Pleistocene Facies Sequences and Relative Sea-level Trends Along the South Coast of Ireland

Abstract

Upper Pleistocene sequences, deposited around 20 ka provide a record of sedimentation during the last glacial/deglacial cycle along the south coast of Ireland. A stratigraphy based on eight lithofacies associations is recognized. Typically, the facies sequences overlie a glaciated shore platform furrowed by subglacial meltwaters. Elements within the stratigraphy comprise: (1) ice advance southwards onto the continental shelf; (2) stagnation-zone retreat triggered by rising sea level related to isostatic depression coupled with subglacial meltwater events that furrowed the platform; (3) progressive rise in relative sea level recorded by a submergent facies sequence on an isostatically depressed slope (beach gravels -->2 subaqueous jet afflux sediments -->2 wave-influenced sands -->2 glaciomarine mud drape); ice-marginal oscillation is recorded by glaciotectonically deformed gravels, sands, and foliated diamict; (4) terrestrial emergence is marked by angular breccias derived from local slopes by periglacial weathering. There is a clear facies transition between the breccias and underlying wave-influenced sands. Facies sequences suggest that the local deglacial cycle was out of phase with the global eustatic cycle along the south coast of Ireland. Stagnation-zone retreat was largely dependent on magnitudes of isostatic depression, high relative sea level, and meltwater events, and not on climatic forcing.