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

south of 51820V prompted Wingfield (1994) to suggest that the Scilly Till probably represents a short-lived
advance by the Dimlington Stadial ice stream.
2.3.10. Irish coast
On the southern Irish coast the distribution, origin and age of the Irish Sea Drifts, particularly the enclosed
Irish Sea Till have been at the centre of controversies over the extent of the last glaciation for almost a century
(e.g. Wright and Muff, 1904; Synge, 1981; Warren, 1985). Although the Irish Sea Drifts have been
traditionally interpreted as terrestrial glacigenic deposits (e.g. Wright and Muff, 1904; Synge, 1978, 1981;
van der Meer et al., 1994), an alternative glacimarine origin has been proposed by Eyles and McCabe (1989).
Moreover, proposed ages for the deposits range from Midlandian/Devensian (Warren, 1985; Gallagher and
Thorp, 1997; McCabe, 1999) to pre-Devensian (Mitchell et al., 1973; Synge, 1981; McCabe, 1987). Recent
sedimentological analysis of the Irish Sea Till by O´ Cofaigh and Evans (2002a,b) and Evans and O´ Cofaigh
(2003) has confirmed a terrestrial depositional origin, implying the onshore movement of an Irish Sea glacier
lobe between Cork Harbour and Kilmore Quay during the last glaciation. The raised beach that
stratigraphically underlies the Irish Sea Till has been dated 162–129 ka BP by infrared luminescence
(Gallagher and Thorp, 1997), placing it firmly in the age range of the last interglacial. Previous
interpretations depicted an ice margin moving offshore at Kilmore Quay and then trending eastwards across
the north Celtic Sea. Recession by the Irish Sea glacier resulted in the damming of the local drainage along
the south coast and the deposition of glacilacustrine sediments in ice-dammed lakes. Glacitectonic
disturbance of the lake sediments by ice of inland origin documents the Midlandian glaciation of inland areas
of southern Ireland previously thought to be covered by pre-Midlandian tills. The bouldery ridge of St
Patricks Bridge and other arcuate ridges located to the east are ice marginal accumulations deposited by the
Irish Sea glacier as it retreated from the southeast Irish coast. O´ Cofaigh and Evans (2002a,b) and Evans and
O´ Cofaigh (2003) suggest that the Irish Sea Till on the southern Irish coast is the onshore record of the
short-lived (rapid or surge) advance of the Irish Sea lobe recorded in the Celtic Sea and on the Scilly Isles.
Scottish Highland ice advance into Northern Ireland is recorded by a lower till sheet in County Down that
contains Ailsa Craig microgranite erratics and shells radiocarbon dated at 24,050±650 BP (I-3268). If the
date is correct it provides a maximum age on the advance of glacier ice onto Northern Ireland. An upper till of
local derivation records the later expansion of Irish ice to exclude Scottish Highland ice from County Down
and the coast of County Antrim (Hill and Prior, 1968).
3. Summary and discussion of the evidence for the last (Dimlington Stadial) British Ice Sheet
3.1. The vertical limits of the ice sheet
Recent developments in the cosmogenic isotope dating of mountain summit blockfields in upland Britain (e.g.
Ballantyne et al., 1998a,b) has given Quaternary researchers confidence in identifying LGM nunataks and
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