A SKETCH OF THE GEOLOGY OF EPPING FOREST. 163
The Lower Bagshot Beds are mainly composed of sand, with
partings of clay and loam. They cap many of the higher hills in
the Brentwood district, and may be seen at Havering-atte-Bower.
But in the Forest they are very scantily represented by the small
patch at High Beach—already mentioned—and possibly by some
sand at Coopersale Common.
There is a very considerable gap between the Eocene London
Clay and Bagshot Beds and the strata next in age—as I have
already stated when treating of the London Clay and its full
thickness. The series of outlying patches of gravel, which are next
to the Bagshot Beds in age, are found resting, sometimes on
strata of the Bagshot series, sometimes on London Clay. On the
other hand, they are evidently older than the Boulder Clay. On
the map of the Geological Survey they are coloured red, and
called "Pebble Gravel," and may be seen to occupy high ground
at High Beach, Jack's Hill, Gayne's Park, and Coopersale
Common, all places within or close to the Forest boundary. They
are classed by Professor Prestwich as "Westleton Shingle." Those
who wish to know what is implied by that name must be referred to
Professor Prestwich's important paper on the "Westleton Beds" in
the "Quart. Journ. Geol. Soc." for 1890, pp. 84-181.3 He gives
the approximate composition of the gravel at Jack's Hill, near the
"Wake Arms," as follows :
1. Flint pebbles ............ 50 percent.
2. White quartz pebbles ... ... ... 15 ,, „
3. Subangular fragments of flint ... ... 20 „ „
4. Subangular fragments of chert and ragstone 10 ,, „
5. Pebbles of Lydian stone, etc. ... ... 5 ,, ,,
100
At Coopersale Common (or Gayne's Park) as:
1. Flint pebbles ............ 56 percent.
2. White quartz pebbles ... ... ... 20 ,, ,,
3. Subangular fragments of flint ... ... 9 ,, ,,
4. Subangular fragments of chert and ragstone 12 ,, ,,
5. Pebbles of Lydian stone, etc....... 3 „ „
100
3 See brief review of this paper in Essex Nat., vol. iv., p. 100