Last glacial dynamics of the Vale of York and North Sea lobes of the British and Irish Ice Sheet.

Abstract

During the Last Glacial Maximum, the Vale of York and North Sea lobes of the British and Irish Ice Sheet extended to within 10 km of each other, impounding a series of pro-glacial lakes. Such an interplay of ice lobes provides a useful analogue for elsewhere in the North Sea basin. This paper focusses on reconstructing the Vale of York and North Sea Ice lobes using a regional suite of 25 luminescence ages in combination with stratigraphical and geomorphic evidence. Results extend and revise the chronology of the Dimlington LGM typesite, showing that the North Sea Ice lobe advanced between 20.9–17.1 ka and 17.1–15.1 ka before present. Initially this lobe impounded a proto Lake Humber which likely covered parts of Holderness as well as the southern part of the Vale of York. Later stages of Lake Humber within the Vale of York show continued blockage of the Humber Gap by the North Sea Ice lobe. The Vale of York Ice extended briefly at ∼18.7 ± 0.63 ka across Lake Humber into South Yorkshire and North Lincolnshire before retreating to and forming the Escrick and York moraines. Both glacier lobes appear to have been short-lived, comprising relatively dynamic ice, especially when moving into areas of deformable lacustrine sediments, which allowed them to rapidly advance and over-extend their margins due to low basal shear stress. Topographic control of the extent and spatial positioning of both Ice lobes also appears to have been significant.