The last British Ice Sheet: A review of the evidence utilised in the ...

3.4. Palaeo-icestreams
Compared to other glaciated regions, very little research has been undertaken on the identification of ice
stream imprints in the British glacial record, despite the availability of geomorphic criteria for the
identification of palaeo-ice streams (e.g. Stokes and Clark, 1999, 2001; Clark and Stokes, 2003). Based upon
the evidence compiled in the Glacial Map of Britain we suggest that the most compelling evidence available
so far for palaeo-ice streams occurs in the Vale of York, Vale of Eden, the Yorkshire Dales and the Tweed
Valley, where subglacial lineations document the impact of former trunk flow. Elsewhere, such as the Irish
Sea basin and Moray Firth, ice stream activity has been proposed based upon topographic constraints and
sedimentological evidence (e.g. Merritt et al., 1995; Evans and O´ Cofaigh, 2003). Although it is becoming
clear that several generations of ice flow lineations exist and demonstrably cross-cut each other (e.g. Salt,
2001; Smith, 2003), reconstructions of British Ice Sheet palaeo-ice flow dynamics are in their infancy
compared to other regions (e.g. Dyke and Morris, 1988; Dyke et al., 1992; Boulton and Clark, 1990a,b). We
suggest that a systematic subglacial lineation mapping programme is urgently required for Britain in order to
assess the dynamics of the former British Ice Sheet through the last glacial cycle.
3.5. Surging activity
Attainment of the maximum limits of the British Ice Sheet has been variously ascribed to surging activity.
Eyles et al. (1994) employed the evidence of the Holderness hummocky moraine and the feather edge of
Withernsea Till in conjunction with Kelsey Hill gravels to support their reconstruction of a surging ice sheet
margin in East Yorkshire. The surging concept was first entertained by Lamplugh (1911) and later supported
by Boulton et al. (1977). Additionally, the low ice profile of 1:750, as represented by the east coast drift limit
from North Norfolk to the North Yorkshire Moors, was regarded as possible evidence of a surging lobe by
Straw (1979). Some corroboration for surging in the North Sea comes from Carr’s (personal communication)
suggestion that the piercing of the western edge of the Dogger Bank-Jutland mega-moraine during the
Dimlington Stadial was due to a surge. The Irish Sea Till on the southern Irish coast and the Scilly Till on the
north coast of St Martins in the Scilly Isles (Scourse, 1986, 1987, 1991a,b; O´ Cofaigh and Evans, 2002a,b;
Evans and O´ Cofaigh, 2003; Hiemstra et al., in press) have been equated with a short-lived onshore flow of
the Irish Sea ice stream/ lobe, although the possibility of palaeo-surging is restricted to evidence of glacier
marginal thrusting and hydrofracture fills produced by elevated groundwater pressures.
Suggestions have also been made that surges characterized some margins of the ice sheet during its
recession. Evans and O´ Cofaigh (2003) cite evidence of thrust moraines on the eastern Irish and north Welsh
coast as possible surge landforms. Long flutings terminating in glacitectonically thrust masses in Loch Ryan,
SW Scotland, are cited by Salt (2001) as evidence of a late stage surge by Scottish ice.
Despite these proposals from various regions, no unequivocal geomorphic and sedimentary evidence for
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