GLACIAL STRATIGRAPHY OF WEST ESSEX 317
A Contribution to the Glacial Stratigraphy of West
Essex
Colin A. Baker
Introduction
A satisfactory explanation of the glacial deposits of west
Essex has long been hindered by a paucity of drift exposures
and rarely any clear indications of the order of superposition.
Apart from the widespread occurrence of glacial sands and
gravels which are known persistently to underlie the main Chalky
Boulder clay of the area there has been no unanimity of opinion
regarding other, more localised stratigraphic sequences. In parti-
cular the Hornchurch boulder clay-terrace gravel relationship
(Holmes, 1892) and the Harlow lower boulder clay (Whitaker et
al. 1878 p. 41) have occasioned much debate concerning the age
and subdivision of the local glacial drifts. In addition, patches
of high-level stony clays have been regarded by some workers
as remnants of weathered till of pre-Chalky Boulder clay age
although this interpretation, up to now, has never been con-
firmed by a single instance where Chalky Boulder clay lies on
the weathered till. Several successions have been proposed, but
no firm local stratigraphic evidence in the form of unequivocal
superposition, buried soil horizons or interglacial organic sedi-
ments has ever been adduced in their favour.
Consequently, the glacial chronology of the area is still very
much in a state of flux. Various methods of till differentiation
have been applied to the local drifts (including studies of mor-
phology, depth of weathering, matrix lithology, erratic content,
stone orientation and heavy mineral analysis) but these criteria
have not by any means yielded an internally-consistent glacial
succession. Five distinct boulder clay types and at least two
periods of periglacial activity have been claimed as follows:—