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

Evidence for extensive glacier ice during the LGM has been uncovered during surveys of the offshore
areas of northern Scotland. Submarine moraines have been located at the edge of the continental shelf to the
north of Lewis and west of Orkney and Shetland (Stoker, 1988). Additionally, a large submarine moraine is
located off the northeast coast of Shetland (Stoker et al., 1993; see below for dating evidence). A series of
prominent submarine end moraine ridges (Wee Bankie Moraine) mark the eastern edge of the glacial
sediments of the Wee Bankie Formation off the east coast of Scotland (Thomson and Eden, 1977; Stoker et
al., 1985). Beyond the Wee Bankie moraine the Marr Bank Formation contains glacimarine sediments. These
features and sediments can be traced to the outer Moray Firth where tills extend up to the Bosies Bank
moraine (Hall and Bent, 1990). The apparent lack of till beyond the Wee Bankie and Bosies Bank moraines
has been used previously to support their interpretation as the Late Devensian ice limit but recent research on
cores from the North Sea indicates a more extensive ice coverage (see below). In the central North Sea
approximately between latitudes 588 and 598N, Jansen (1976) reported ice marginal deposits associated with
the Fennoscandinavian Ice Sheet, named the Hills Deposits. They include morainic terrain separated from
coeval glacimarine sediments by a 30 m high, single end moraine ridge. The glacimarine sediments are the
lateral equivalent of the Marr Bank Formation.
In addition to the prominent deglacial moraines offshore like the Wee Bankie and Bosies Bank moraines,
ice-marginal landforms and sediment accumulations are widespread on land. Glacier recession is also clearly
marked by meltwater channels in many drainage basins. Several readvances of Scottishcentred ice have been
proposed based upon extensive and substantial moraine systems. The Aberdeen–Lammermuir Readvance
(Synge, 1956; Sissons,1967a, 1981) was proposed to account for almost continuous assemblages of
glacifluvial sands and gravels. In the Aberdeen area this is typified by a 3 km wide belt of ice-marginal
deposits stretching across the lower Dee valley (Brown, 1993). Linear accumulations of glacifluvial deposits
were mapped in the Aberdeen area by Synge (1963b) and associated with glacier margins during readvances
(e.g. Dinnet Readvance and Aberdeen Readvance). Such features were previously assigned to a Dinnet
Readvance by Bremner (1931a) and Synge (1956) and then reinterpreted as stagnation deposits by
Clapperton and Sugden (1972, 1977), Sugden and Clapperton (1975) and Murdoch (1975). The most recent
assessment of the ice-marginal deposits in the Dee Valley by Brown (1993) proposes a marginal supraglacial
origin similar to the evolution of moraines on sub-polar glaciers. This explains their linearity and diverse
sedimentology and indicates a series of glacier recessional stages. Additionally, the meltwater channels of the
area are subdivided by Brown into discordant (subglacial) and concordant (ice-marginal) types.
The marginal recession of the Forth glacier is well documented by a series of spectacular meltwater
channels and glacilacustrine sediments on the southern margin of the Ochil Hills (Russell, 1995). Two lake
levels at 269 m and 233 m are recorded for an ice-dammed lake in Glen Devon. Further meltwater channels
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