and on the Drift of the Eastern Counties. 193 
clay-beds, it is not improbable that they were formed in the 
small interval between the close of the fifth-stage Crag and the 
commencement of the deposit of the Drift sands, their sediment 
being furnished by the discharge of the streams to the north- 
ward, which, during the time when the Red Crag was accumu- 
lating, deposited the Fluvio-marine Crag, but which streams, at 
this subsequent period, under the effect of the recession at this 
point of the coast-line, had ceased to produce fluvio-marine con- 
ditions over this portion of the area. The base of the Drift sands, 
where it rests on the Red Crag, is often much mixed with loam, 
producing the flaky dark-red beds that immediately rest upon 
the eroded Crag, and furnishing, where the denudation has 
reached down to them, very rich lands. It appears, therefore, 
to me that in these we may have the equivalents of at least the 
laminated clays forming the upper portion of the Chillesford 
beds. 
Crossing the ridge of Coralline Crag never covered by Red, 
we reach, at Thorpe, two miles north of Aldbro’, the true 
Fluvio-marine or Norwich Crag. So far as I could learn, this 
solitary pit at Thorpe constitutes the only exposure of Fluvio- 
marine Crag south of Southwold Cliffs, a distance of eight miles 
further north. This exposure seems to be due to a fault bring- 
ing up the Fluvio-marine beds at this point through the over- 
lying Drift sands which form the surrounding country *. The 
pit is now nearly overgrown with grass; but the beds appear to 
have been brought to the surface and denuded at the period of 
the formation of the valley-system; so that there are no means 
afforded of testing their position relatively to the Chillesford 
beds. The upper part of these Chillesford beds, composed of 
the laminated grey clays, occurs at a brick-field between Thorpe 
and Aldbro’,—at which: place they are pierced in the well 
down to a Crag which the workmen described as the yellow 
Coralline Crag of the pit just below, about a furlong distant, 
and nearer Aldbro’. The latter pit occurs at a lower level than 
the brick-field, and is composed of Coralline Crag ; but the valley- 
denudation has swept the top of the pit clear of all the overlying 
Drift sands and of everything that may have occupied the in- 
terval between it and these sands, with the exception of two or 
three very minute traces of a Crag that resembles the Red, but 
which is so comminuted as to be incapable of identification ; 
* There is evidence of considerable displacement between Thorpe flag- 
staff and Sizewell Gap; and at the latter place the displacement has been 
great enough to bring down the upper Drift, that is otherwise quite denuded 
over this area, by a sharp pitch into the midst of the lower-Drift sands. 
(See Section B.) A pit there shows it inclined at a considerabie angle, 
resting on the lower Drift. 
