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

and Sutherland. Although this limit has been assigned previously to either the Aberdeen–Lammermuir
Readvance (Sissons, 1967a) or the maximum limit of the last glaciation (Sutherland, 1984), there is no firm
evidence to suggest that the local tills and shelly tills are not coeval and therefore record the junction of
Caithness/Sutherland and Moray Firth ice at the LGM (Peach and Horne, 1881b; Hall and Whittington, 1989;
Hall et al., 2002).
The erratic content of the tills in eastern and northeastern England has been used to distinguish different ice
source areas but without reference to any one specific glaciation (cf. Harmer, 1928; Raistrick, 1931a,b).
Scandinavian erratics found in Devensian tills are thought to have been reworked from older till units (Catt,
1991a). Within Devensian tills along the east coast, erratics have been recorded from two distinct geographic
areas. In the lower till (Skipsea Till), erratics indicate a northern source from the Southern Uplands and the
Cheviots, whilst the upper (Withernsea Till) has erratics from the Lake District and Pennines suggesting
changing dominance of ice source areas during the course of the last glaciation (Catt, 1991b).
A prominent marker erratic in northern England is Shap granite which has a small outcrop in the eastern
Lake District, but has a widespread distribution having been reported both around Kendal to the south and in
the Vale of Eden to the north (Howarth, 1908a,b,c,d,e; Letzer, 1978). However, it is the far travelled easterly
distribution through Stainmore to the east coast and down the Vale of York that is most significant, revealing
a breaching of the Pennines by ice from Scotland and the Lake District (Raistrick, 1931b; Letzer, 1978; Catt,
1991a,b). Another distinctive erratic train is found at Norber, near Settle where conspicuous blocks of
Silurian gritstone have been emplaced on Carboniferous limestone by upward glacial transportation in a
southwesterly direction (cf. Huddart, 2002a and references therein).
2.1.2 Erosional features
Roches moutonnées and striae may provide clear indicators of local and regional ice flow (e.g. Gemmell et al.,
1986; Sharp et al., 1989; Sugden et al., 1992; Lawson, 1996; Viellette et al., 1999), although multiple
ice-flow directions driven by complexities in bedrock topography need to be taken into account (e.g. Rea et
al., 2000). On the Lleyn Peninsula, North Wales, striae measured by McCarroll (1991) and Gibbons and
McCarroll (1993) reveal ice flow from NE to SW on the northern shore of the west coast, veering to
north–south along the hills in the westernmost tip of the peninsula. Welsh ice produced SW to WSW
orientated striae on the inland part of St Tudwals with striae aligned east–west at the east end of Porth Neigwl.
Striae record an onshore flow owards the west to northwest on the south tip of St Tudwals.
Reconstructions of an ice divide for an independent Outer Hebrides Ice Cap lying immediately over the
west coast of the Uists at the LGM are based upon the transport of erratics and erosional ice-directional
indicators (von Weymarn, 1979; Coward, 1977; Flinn, 1978a,b; Peacock and Ross, 1978; Peacock, 1984,
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