Vol. XXVII—Part V. April—Sept., 1942
THE
Essex Naturalist:
BEING THE
Journal of the Essex Field Club
THE DRIFTS OF SOUTH-WESTERN ESSEX
By S. HAZZLEDINE WARREN, F.G.S.
(Being a Presidential Address read 28th March, 1942.)
Part I.
IN choosing my subject I had two aims in view. Firstly,
to place on record certain new geological sections, and
secondly in the hope of appealing to wider interests, to place
these within the framework of the physical history of the region.
The "imperfection of the geological record" is familiar
to all, and we find that the interpretation of fragmentary, and
often isolated, patches of drift (gravel, sand, clay, etc.) leaves
much scope for differences of opinion. Limitation of space
precludes discussion of divergent interpretations ; one must
be content to give a general sketch of the inferences that seem
probable in the light of new facts.
In order to understand our limited region we must have
some grasp of its relations to a wider area. We must, as it
were, sketch—in the back-scene to our geological drama.
The foundation, or country rock, of the greater part of
Essex consists of London Clay, which passes upwards conform-
ably into the Claygate Beds, and thence to the Bagshot Sands
and Pebble Beds. This indicates a progressive shallowing of
the Eocene Sea, until the London Basin emerged as dry land.
The post-Eocene land surface is represented by a break in the
geological record and no detailed information is available.
During the great earth storm of the Miocene period, when
the Alps came into being, the anticlinal dome of the Weald
underwent elevation, while the synclinal hollow of the London
Basin suffered a compensating depression.
The Lenham Stage [Wooldridge, 1927].—The earth move-
ments referred to above broke up the old land surface, and near
the end of the Miocene period an arm of the sea rose to the
present level of about 700 O.D. This resulted in the deposition
of the Lenham Beds.