Bedrock controls on subglacial landform distribution and geomorphological processes : evidence from the Late Devensian Irish Sea Ice Stream

Ice streams play an important role as regulators of the behaviour of modern ice sheets, taking the form of corridors of fast flowing ice. Similar zones of fast moving ice have also been recognised draining the margins of the Late Devensian British and Irish Ice Sheet. Although the geomorphological and sedimentary signatures of palaeo ice streams have received significant attention, allowing the identification of these former ice streams, the influence of bedrock geology on the processes occurring beneath these palaeo ice streams is less well understood, even though subglacial geology has been shown to control the location ice streams within the West Antarctic Ice Steam. This paper highlights the role played by bedrock geology on landform distribution beneath a much older ice stream, the Late Devensian Irish Sea Ice Stream. The spatial relationships displayed between subglacial landforms and bedrock geology are described from Anglesey, northwest Wales, and the Rhins of Galloway, southwest Scotland; both sites occur close to the eastern margin of this Irish Sea Ice Stream. A link has been established between landform morphology and distribution, and the disposition of the main tectonostratigraphical units within the bedrock. Changes in landform morphology are shown to have been locally controlled by large-scale faults and/or major lithological boundaries, with less durable bedrock lithologies controlling the location and lateral extent of relatively faster flowing portions of the ice stream

Geomorphological and seismostratigraphic evidence for multidirectional polyphase glaciation of the northern Celtic Sea

High‐resolution seismic and bathymetric data offshore southeast Ireland and LIDaR data in CountyWaterford are presented that partially overlap previous studies. The observed Quaternary stratigraphic successionoffshore southeast Ireland (between Dungarvan and Kilmore Quay) records a sequence of depositional and erosionalevents that supports regional glacial models derived from nearby coastal sediment stratigraphies and landforms. Aregionally widespread, acoustically massive facies interpreted as the‘Irish Sea Till’infills an uneven, channelizedbedrock surface overlying irregular mounds and deposits in bedrock lows that are probably earlier Pleistocenediamicts. The till is truncated and overlain by a thin, stratified facies, suggesting the development of a regionalpalaeolake following ice recession of the Irish Sea Ice Stream. A north–south oriented seabed ridge to the north is interpreted as an esker, representing southward flowing subglacial drainage associated with a restricted ice sheet advance of the Irish Ice Sheet onto the Celtic Sea shelf. Onshore topographic data reveal streamlined bedforms that corroborate a southerly advance of ice onto the shelf across County Waterford. The combined evidence supports previous palaeo glaciological models. Significantly, for the first time, this study defines a southern limit for a Late Midlandian Irish Ice Sheet advance onto the Celtic Sea shelf