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 foraiing 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 j 



* There is evidence of considerable displacement between Thorpe flag- 

 staflf 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 considerable angle, 

 resting on the lower Drift. 



