Ice-flow stages and glacial bedforms in north central Ireland: a record of rapid environmental change during the last glacial termination

Satellite imagery is a useful tool to assess large-scale (>103km2) geological patterns. Satellite imagery of north central Ireland shows cross-cut and overprinted subglacial bedform patterns. Bedform lineations, supported by sedimentary evidence, are used to reconstruct four ice-flow stages (named A-D) during the termination of the last (Devensian) glaciation (22 000–13 000 radiocarbon (14C) years BP). Flow stage A relates to southwesterly flow of Scottish ice across eastern Ireland. Flow stage B, during the last glacial maximum (c. 25 000–22 000 14C years BP), records southeasterly ice-flow from dispersal centres in northern parts of Ireland. Transverse subglacial ridges (Rogen moraines) formed during stage B are the largest area of this ridge type in western Europe. Flow stage C records erosional headcutting in the Rogen moraine field and sediment streamlining (drumlinization) by ice streams drawn into the Irish Sea Basin. This flow stage is constrained by AMS radiocarbon dates from marine microfaunas to around 14 500 14C years BP. Flow stage D records drumlinization from an inland centre in the Lough Neagh Basin. Overall bedform patterns can be used to reconstruct ice mass history and evaluate controls on ice activity, including millennial-scale changes in amphi-North Atlantic climate. Field evidence of bedform relationships also casts doubt on current concepts of drumlinization and the role of pervasive sediment deformation in glacial systems.