THE DRIFTS OF SOUTH-WESTERN ESSEX. 175
Sturry that rafts of older deposits, enclosing contemporary
implements, have been transported bodily into gravels of late
date, and this process may also have occurred here.
The Ilford Brickearths (10-40 O.D.) [Hinton 1900].—These
classical deposits fit appropriately, alike in fauna and position,
between the Furze Platt and the Crayford stages.
The Northfleet Stage (30-40 O.D.).—The river erosion
platform stands at about 30 O.D., and appears to represent a
pause in the down-cutting between the 50-foot platform and
the Crayford stage. This floor is occupied by an Early Levallois
industry, and it is covered, not by river deposits, but by a sludge
stream of Coombe rock, or chalky rubble, which indicates
sub-glacial conditions.
The name site of the Taplow Terrace appears to be of this
stage.
The Crayford Stage (— 10? to +50).—This was preceded
by emergence with down-cutting by the rivers so that the
erosion floor, or river-bed, appears to descend below O.D. The
river fore-shore at 0 to 30 O.D. was occupied as a working site
of the Mid Levallois industry [Spurrell 1880, Chandler, 1912,
1914]. Similar flints are also found in the lower part of the
brickearths, which are banked against a buried river cliff. The
Crayford deposits consist, in ascending order, of :—L Basement
gravel ; 2. Lower brickearths ; 3, sandy shell-bed with Corbicula
fluminalis ; small mammals, etc. ; 4, upper water-laid brick-
earths up to about 50 O.D. ; 5, Trail.
The shells of No. 3 indicate a warm temperate climate, but
the small mammals (Spermophilus, etc.) indicate a cold fauna.
It was probably a time of changing climate, and there may have
been a land surface above the shell bed from which the small
bones were introduced by burrowing animals. Two years ago I
described to you the way in which large numbers of small
bones were introduced by badgers into the glacial sands at
Nettleswell Cross.
On our side of the Thames, at West Thurrock, a similar section
is revealed in a tramway-cutting to a chalk pit. There is the
Mid Levallois working site on the old foreshore, which is inclined
from the foot of the buried river cliff towards the bed of the
river, and this is similarly covered by the loamy and sandy river
deposits that are aggraded up to about 50 O.D.
The alternate emergence and submergence of the Clacton
stage is repeated, and at Crayford there is again evidence from
the shell fauna of brackish water conditions up to about 30 or
40 O.D., thus leaving deposits belonging to different stages
over the same range of levels.