328
THE ESSEX NATURALIST
(c) That they represent a single ice advance and retreat.
Boulton (1967) has demonstrated from a study of
the Sorbreen glacier, Vestspitsbergen, that complex
sequences of tills and bedded sediments may result
from the melting out of englacial and supraglacial
debris at the ice margin during a single retreat
phase. This is especially true (ibid p. 734) where, as
in the case of Vestpitsbergen, glaciers traverse an
area of relatively soft sedimentary rocks. The west
Essex glacial environment may well have been
analogous.
It is simpler therefore to regard the intercalated sands/gra-
vels/silts as intra-glacial (i.e. involving either minor advances and
retreats or one retreat phase of the Chalky Boulder clay ice
margin) than to adopt a multiglacial hypothesis.
Finally, in this section, Clayton's "Maldon Till" may be con-
sidered although the deposit itself is unrepresented in the cross-
section. Maldon Till is found at Maldon, Chelmsford and Harlow
underlying Chelmsford Gravels which in turn underlie Springfield
Till (Clayton, 1957). Hence, it is assigned a chronological position
intermediate between the Hanningfield and Springfield Tills, and
separated from those deposits by interglacial/interstadial periods
—a "long period of erosion" and the Chelmsford Gravels respect-
ively. It is a thin, highly localised and impersistent boulder clay,
and one which has strong lithological affinities with the main
(Springfield) chalky boulder clay above.
Notwithstanding the difficulties encountered in mapping this
deposit (1958, p. 47), clearly Maldon Till does not maintain con-
sistent stratigraphic relations, for north-east of Harlow it is partly
enclosed by Chelmsford Gravels, and patches west of Maldon are
wholly enclosed by them (1964 p. 124).
At Harold Hill (TQ 540930) it immediately adjoins Springfield
Till with no intervening gravels, while at Harlow (in the cross-
section already mentioned) it is seen to grade into Springfield
Till as it rises up towards Epping Long Green. In other words, it
constitutes a locally intercalated layer within Chelmsford Gravel,
having been deposited during, as well as prior to, the main Chalky
Boulder clay outwash phase. As such—and here it is analogous
to the intra-glacial sediments—its individual stratigraphic signifi-
cance should not be overemphasised. This point was made by
Whitaker as long ago as 1878 when he stated that the glacial sands
and gravels contain "layers of Boulder clay .... not to be distin-
guished from the thick mass of such clay that comes on above"
(p. 33).
The initial rationale of Clayton's subdivision (1957, 1958) was
consistent with this view in so far as it regarded the "tripartite
sequence" (Maldon Till—Chelmsford Gravels—Springfield Till) as
a continuous depositional sequence. But subsequent attempts to
fit the Hoxnian Interglacial into the Maldon-Springfield interval