Dynamic ice stream retreat in the central sector of the last British-Irish Ice Sheet

Bethan Davies, Stephen J. Livingstone, David H. Roberts, David J A Evans, Delia Gheorgiu, Colm Ó Cofaigh

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During the Last Glacial Maximum (LGM), ice streams of the last British-Irish Ice Sheet (BIIS) controlled the discharge of ice and sediment from various dispersal centres. Deglaciation was characterised by shifts in ice-divide location and changes in internal ice-sheet dynamics, resulting in flow switches and ice-stream reconfiguration, and hence significant modification of their landform signatures. We present new geomorphological mapping and 11 10Be cosmogenic nuclide ages from the Stainmore Gap, Eden Valley and Vale of York, constraining regional dynamic ice-stream retreat following the LGM. We identify complex decoupling of competing ice lobes, characterised by early retreat of the North Sea Lobe and a minor re-advance of Stainmore ice prior to ~20 ka. This was followed by rapid recession of the central Stainmore Gap, which was ice-free by 19.8 ± 0.7 to 18.0 ± 0.5 ka, indicating contemporaneous recession with the Tyne Gap Ice Stream. In the southern Vale of Eden, Crossby Ravensworth Fell became exposed between 19.2 and 20.3 ka. The northwards ice-flow reversal in the Vale of Eden occurred while the Stainmore and the Tyne Gap ice streams were still active, but must have been associated with the development of ice domes across the northern Pennines, Howgill Fells and the Lake District. This shift in dispersal centres and ice divide migration likely triggered the rapid collapse of eastward ice stream corridors. These new age constraints suggest that the central sector of the BIIS rapidly collapsed back up into upland dispersal centres between 20 - 17.5 ka.
Original languageEnglish
Article number105989
Pages (from-to)1-21
Number of pages21
JournalQuaternary Science Reviews
Early online date12 Oct 2019
Publication statusPublished - 1 Dec 2019

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