The development and impact of an ice-contact proglacial lake during the Last Glacial Termination, Palaeolake Riada, central Ireland

Abstract

The retreat of the last Irish Ice Sheet across the Irish midlands resulted in the formation of an ice-contact lake, Palaeolake Riada, along its eastern margin during recession. However, the full extent and characteristics of the lake and its impact on ice dynamics are unknown, as glacigenic landforms and deposits relating to the lake have not been mapped in sufficient detail to allow reconstruction of ice-marginal behaviour. This paper presents new mapping of subglacial, ice-marginal and glaciolacustrine landforms and deposits in the Irish midlands. Glacial landforms and landform associations across this wide area have been identified using aerial photographs and high-resolution digital elevation models derived from LiDAR and radar data. Reconstructions of successive ice-margin retreat positions are combined with glacio-isostatically adjusted digital elevation models to identify the probable position of lake outflows and reconstruct the development of the proglacial Palaeolake Riada through time. These reconstructions indicate that at its largest, Palaeolake Riada had an ice-contact margin of 113 km, and covered an area of over 2300 km2. Initially, ice recession was concentrated around meltwater discharge outlets, but these became less important as the lake expanded and thermo-mechanical erosion occurred along the entire subaqueous margin.