231
IX.
Notes on the London Clay and Bagshot Beds at "Oakhill
Quarry," Epping Forest.
By N. F. Robarts, F.G.S.
[Read November 25th, 1882.]
The section exposed of the upper beds of the London Clay
and Lower Bagshot at "Oakhill" Quarry and Brick-field on
the south of the road running from Theydon Bois Railway
Station to the "Wake Arms" public-house, and about one
mile west of the station, has not, I believe, been yet described.
Before dwelling upon the few details of this section which
I have to bring forward, I propose to give a short general
description of the main geological features of the country
lying between Hainault Forest and Waltham Cross. In doing
this I must disclaim making any attempt at originality, my
only purpose being to arouse some interest in our local
Geology, and to induce others to study it for themselves.
The prevailing formation of both hills and valleys in this
part of Essex is the London Clay, which has almost every-
where been extensively denuded, and in consequence of its
great thickness forms not only the hills and slopes, but also
the bottoms of the valleys, although the Clay is sometimes
covered up and hidden by recent gravels and alluvium.
The valleys of the rivers Boding and Lea are good examples.
Chigwell Bow stands about 170 feet above the River Roding,
and is formed almost entirely of London Clay, which rises to
a still greater height at the Wake Arms and High Beach,
whilst the eastern slope of the Lea Valley is similar to both
slopes of the Boding Valley. The thickness of the London
Clay in places where the Bagshot Beds overlie it—showing
that in these places no denudation of the Clay has taken
place since the Bagshot Beds were deposited—is about 300
to 400 feet. As a rule the upper beds of the Clay are wanting,