Buried geomorphic features in the North-western Irish Sea: markers of the last glaciation and deglaciation episodes

To understand the advance and retreat of the British and Irish Ice Sheet (BIIS), geomorphic features have been extensively characterised onshore. The extent of these features in the Irish Sea has been poorly constrained, even though the Irish Sea Ice Stream (ISIS) was the largest drainage system of the BIIS and had a strong impact in shaping the present-day seafloor. Previous studies have highlighted the occurrence of till surfaces, glacio-marine and transitional stratigraphic units to marine environments. Constraining the extension of these units and characterising the associated geomorphic features is important to any attempt to reconstruct the history of the BIIS evolution since the Last Glacial Maximum.

This study presents new information produced by interrogating large geophysical datasets of sub-bottom profiler, single-channel Sparker, and multibeam echosounder bathymetry in the North-Western Irish Sea, from Dundalk Bay to Lambay Deep. These data spatially map the complex sub-surface stratigraphy, comprising different glacial and post-glacial units and the geomorphic features they form, including grounding-zone wedges, channels, and iceberg scouring. Initial interpretation of these features has been performed with regard to established stratigraphic frameworks and regional glacial and postglacial geodynamic models. This presentation will focus on the results of the geomorphic feature interpretation, with the aim of constraining the ISIS advance and retreat in the North-western Irish Sea, filling a critical gap in our understanding of the demise of the BIIS.