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

The Linton-Stutton gravels occur outside the Escrick moraine between Tadcaster and Wetherby and form
an extensive but discontinuous spread of ice-contact gravel mounds with subdued relief. Sections show
extensive deformation and they are thought to have formed at an earlier stage of the last glaciation than the
York–Escrick moraines (Edwards et al., 1950). These deposits were interpreted as a kame by Edwards et al.
(1950) but as an esker north of Bramham by Straw (1979). Straw (1979) suggested a submarginal (or
interlobate?) origin for this “esker” associated with the Nidderdale Glacier, which was deflected over
Harrogate by the Vale of York lobe during a pre-Escrick phase [Early Main Dales Glaciation of Edwards
(1938)]. Lateral meltwater channels along the former western margin of the Vale of York lobe were mapped
by Kendall and Wroot (1924) and Melmore and Harrison (1934). Where these lay outside the York–Escrick
limits and in association with the Linton-Stutton gravels, they were regarded as pre-LGM. The diversion of
the River Wharfe was associated with the construction of the Escrick moraine because it now occupies a
course that follows the distal side of the moraine and does not follow its preglacial course. Gaunt (1981)
suggested that the Vale of York lobe initially advanced as a surge into Glacial Lake Humber all the way to
Wroot in Lincolnshire based on one main line of evidence, the “Wroot Thorne Gravels”. The margin later
stabilized at the York and Escrick moraines when the level of Glacial Lake Humber dropped. Straw (1979)
had previously proposed that the till to the south of the York and Escrick moraines was “older”, probably
early Devensian in age. There has however been continued debate regarding the existence of this surge and in
a recent review of the possible evidence for such an event, Straw (2002) rejects this sequence of events and
argued that the stratigraphic record south of the Escrick moraine is pre-Devensian and that the last ice sheet
limit in the Vale of York is at Escrick. A lower stage Lake Humber is recorded by interdigitation of lake
sediments (the “25 foot drift”) and the till and gravels of the Escrick Moraine, demonstrating that the moraine
was deposited at an ice-contact lake margin (Gaunt, 1970).
A prominent hummocky moraine on Flamborough Head was identified by Farrington and Mitchell (1951)
who regarded it as an end moraine. This moraine assemblage widens and stretches northwards to Speeton and
then to Cayton where it has been called the Speeton moraine by Valentin (1957), who allocated it to a
“second readvance” on Holderness. Specifically, the prominent morainic relief was the result of the
compression of ridges against the chalk scarp and the overriding of “first readvance” deposits. This was later
termed the “Cayton-Speeton Stage” by Straw (1979). The Flamborough Moraine to the south was allocated
to the “Seamer-Flamborough Stage” by Penny and Rawson (1969) who referred to the linearity in the
moraine at Reighton as possible drumlins. Further south on Holderness, Valentin (1957) traced a line
connecting the outcrops of the Kelsey Hill Gravels at Burton Agnes, Brandesburton, Bilton and Patrington
out to the North Sea, which he regarded as a product of the “second readvance”; this line also encloses the
extent of the Withernsea (Purple) Till (see Section 2.3). Outside this limit the margins of the “first readvance”
are marked by subdued morainic ridges at Routh, Wawne and Sutton (Straw, 1979). The high land at
22