88 GEOLOGICAL NOTES IN THE NEIGHBOURHOOD OF ONGAR.
far as Kelvedon Hatch, and this little slipped patch alone remains
protected by the sides of the valley and the Boulder Clay.
I shall return soon to the gravels of the Roding Valley, but I
must first say a word or two about the high level gravels, and I will
first take the hills on the west which are a part of the Epping Ridge
and are capped with gravel at Coopersale Common and Gaynes
Park Wood. It has been described as Pebble Gravel by Mr. S. V.
Wood and the Geological Survey2 and as Westleton Shingle by
Prof. Prestwich,3 who is scarcely correct in speaking of Coopersale
Common as a range of hills distinct from the Epping hills. It is all
part of one crescent-shaped ridge as I have already pointed out.4
I noted the following section at Coopersale Common :—
1. Clay, in places very like London Clay, but sometimes
mottled, and always containing many small stones
and fragments of flint, thickness up to 4 feet.
2. A mass of pebbles and small quartz grit and sand
usually of a greyish colour, but sometimes mottled
red and grey, 5 feet.
Bed 2 consists mainly of flint pebbles, but subangular flints and
pebbles of quartz of 1/2 inch or more in diameter are found without
difficulty. I found some small bits of white cherty stone, some
fragments of ironstone, and a very small red pebble, probably a
quartzite. I consider this gravel to be a good example of the
pre-glacial pebble gravel of this district, and it seems to have been
very little disturbed during glacial times.
On the opposite side of the River Roding is the plateau of
Kelvedon Common, and it is capped in places by patches of gravel.
They have been described as Bagshot Pebble Beds by Mr. S. V.
Wood,5 and are to some extent mapped as such by the Geological
Survey.
I noted the following sections:—
Gravel Pit one furlong N. W. of Dudbrook House. Level
308 feet O.D. Gravel (not mapped) 5 feet or more
thick, not stratified, of a reddish colour or mottled
yellow and red; in some places a little clayey sand.
Mainly flint pebbles, but there are a good many sub-
angular flints and a few quartz pebbles up to inch
diameter.
2 Quart. Journ. Geol. Soc. (1868), vol. xxiv., p. 467; Whitaker's "Geology of London
(1889), vol. i., p. 294.
3 Quart. Journ. Geol. Soc. (1890), vol. xlvi., p. 136.
4 Essex Nat. (1890) vol. iv., p. 200; Proc. Geol. Assoc. (1891), vol. xii., p. 110.
5 Quart. Journ, Geol, Soc. (1868), vol. xxiv.. p. 466.