Palaeoglaciology of the Welsh sector of the British–Irish Ice Sheet

Abstract

This palaeoglaciological reconstruction, based on the distribution of glacial lineations interpreted from satellite imagery, considers the extent, thickness and dynamics of the Welsh Ice Cap and its interaction with the British-Irish Ice Sheet. Two major ice-flow events were identified. The oldest phase of ice flow (Event I) is characterized by ice flowing from an ice dispersal centre situated over the higher terrain in northcentral Wales and by ice thick enough to cover the mountain summits. At this time the interior of the ice cap is inferred to have been dominated by cold-based ice. During the growth of the Welsh Ice Cap it became confluent with the British-Irish Ice Sheet. The Welsh Ice Cap at this time was again sufficiently thick to submerge the highest mountain summits. The youngest detected phase of ice flow (Event II) was marked by an abrupt change in the dynamics of the Welsh Ice Cap. During Event II the Welsh Ice Cap was drained by at least four ice streams, which followed major troughs in northern and eastern Wales.

Extent and timing of the Last Glacial Maximum (LGM) in Britain and Ireland: a review

“…Further south the LGM limit is poorly constrained morphologically but, based on Geological Survey drift mapping of till distribution, it runs south from Stoke through Stafford, then curves south and west around Wolverhampton to cross the River Severn south of Bridgnorth (Wills, 1924). From here the limit runs northwest towards Shrewsbury, where complex ice-marginal landforms and sediments reflect interaction between the western margin of the Irish Sea ice lobe and the expansion of Welsh ice eastwards into the margin of the Cheshire-Shropshire lowlands along the Severn and Four Crosses ice streams (Thomas, 1985(Thomas, , 1989(Thomas, , 2005Worsley, 1991Worsley, , 2005Jansson and Glasser, 2005). The precise relationship between these two ice masses is unclear but the stratigraphy (Thomas, 2005) and moraine pattern suggest that Welsh ice, held back during maximum penetration of the Irish Sea ice, advanced out into the lowlands as a series of piedmont glaciers on retreat of the Irish Sea ice.…”

Extent and deglacial chronology of the last British–Irish Ice Sheet: implications of exposure dating using cosmogenic isotopes

“…Additionally, if the trimline data represent the approximate altitude of an englacial boundary between sliding ice at melting point on low ground and cold-based ice frozen on to summits and plateaux, they offer the possibility of constraining the thermal regime of the last BIIS and the location of frozen-bed zones within the ice sheet (Hall and Glasser, 2003;Jansson and Glasser, 2005;Kleman and Glasser, 2007), and for selection of appropriate climatic parameters for constraining numerical models of ice sheet growth (Boulton and Hagdorn, 2006). Ongoing research is focusing on testing the englacial model for trimlines in northwestern Scotland using paired cosmogenic isotopes ( 10 Be and 26 Al) to establish whether above-trimline areas experienced cover by the last ice sheet (cf.…”

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

“…1a): e.g. eastern Scottish Highlands (Merritt et al, 1995;Golledge and Stoker, 2006); northwest Scotland and the Minch (Bradwell et al, 2007); western Shetland (Davidson and Stoker, 2007); northern England (Everest et al, 2005;Evans et al, 2009); south and northeast Wales (Jansson and Glasser, 2005); northern and central Ireland (Knight et al, 1999); and Irish Sea (Ó Cofaigh and Evans, 2001;Scourse and Furze, 2001;Evans and Ó Cofaigh, 2003;Roberts et al, 2007). The geomorphological signature of palaeo ice streams, in particular, has received significant attention (Dyke and Morris, 1988;Hodgson, 1994;Patterson, 1997Patterson, , 1998Stokes, 2001, 2003) allowing the establishment of a set of criteria for identifying the existence/former existence of ice streams (Stokes and Clark, 1999).…”