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

1991). This ice cap coalesced with mainland ice to the east of the Uists and deflected it southwestwards
across the Sea of the Hebrides (Davies et al., 1984; Selby, 1989; Peacock et al., 1992). Some controversy
surrounds the reconstruction of ice flow directions within the independent ice cap that formed over the
Shetland Islands (Peach and Horne, 1879, 1881b,c;
Hoppe, 1974; Flinn, 1977, 1978a,b), although striae and erratic distributions appear to support
reconstructions of an ice divide centred on the long axis of the islands (Chapelhowe, 1965; Mykura and
Phemister, 1976; Flinn, 1978a,b, 1983). In Caithness and Orkney, striae and ice-moulded bedrock (Peach and
Horne, 1881a; Wilson et al., 1935) support the northwesterly
flowing ice suggested by the distribution of shelly tills and indicator erratics (Peach and Horne, 1880, 1881a;
Rae, 1976; see above and Gordon, 1993a).
2.1.3. Subglacially streamlined land forms
The most characteristic landforms associated with the last glaciation in northern England are the widespread
streamlined landforms, particularly drumlins. As in many other areas of former ice sheet cover, drumlins
occur as fields with thousands of individual bedforms and occur in distinct areas of the former ice sheet beds
either associated with the existence of fast ice streams (Clark, 1997; Clark and Stokes, 2003) or glacier lobes
towards the ice margin (cf. Benn and Evans, 1998). Their origin is associated with subglacial bed
deformation and/or erosion, with drumlin long axes orientated parallel to ice flow direction. Various drumlin
morphologies have been identified with the more complex forms being associated with superimposed flow
patterns (cf. Rose and Letzer, 1977a,b; Benn and Evans, 1998). Records of drumlins are found in the early
literature for the northern England, particularly in the Geological Survey memoirs (e.g. Aveline and Hughes,
1888; Dakyns et al., 1890, 1891). However, no attempt was made to reconstruct ice flow patterns from the
landforms at this time because attention was focused on striae and the distribution of erratics that identified a
local ice centre over Baugh Fell. Detailed field mapping has allowed the reconstruction of a much more
extensive ice divide across the western Pennines and Lake District that defined flow convergence southwest
down the Lune, north down the Vale of Eden and eastwards towards Stainmore (Letzer, 1978, 1987; Mitchell,
1991b, 1994; Mitchell and Clark, 1994). One of the major problems in reconstructions of the palaeoflow
patterns is that in many areas drumlins are associated with conflicting flow directions, indicating that the
drumlins were not formed at one time but diachronously in association with different ice flow phases. There
has also been no attempt until the production of the Glacial Map of Britain (Clark et al., 2004) to compile an
overall map of these landforms so that the quality of information available for drumlins varies from written
observations to detailed field mapping. For some areas high quality data are available based on field mapping
at scales of 1:25,000 and 10,000, which allows the recording of all drumlins and areas of superimposed
drumlins. Published maps of these areas, however, necessarily lose resolution because of reduced scale (cf
Mitchell, 1991a,b). In other areas drumlins have been reported on maps at a more general level. Some
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