444 Mr PHEAR, ON THE GEOLOGY OF SOME PARTS OF SUFFOLK, &c. 



its absence may be ascribed to denudation, and probably it would be instructive to trace its 

 edge closely. 



I imagine that there is moreover another sand and gravel superior to this. There 

 certainly exists an extensive platform of these materials, resting against the chalk towards 

 Holkham, Wighton, Wells, &c, passing inland by Holt, &c, and terminating in singularly 

 abrupt escarpments towards the coast, as at Cley, Wey bourne, Sherringham, &c. These 

 escarpments strongly resemble the sand-cliffs of the Gipping valley in form, and like them 

 generally rest upon a chalk shelf: no doubt a great difference in the powers of resisting 

 denudation between two contiguous strata produces this appearance : they also resemble the 

 Gipping sand-hills in the regularity of their stratification, and in the fact of their being 

 capped by a large coarse gravel. As a feature in the landscape they contribute very much 

 to the beauty of the Glandford valley, as well as of the neighbourhood of Sherringham and 

 Cromer. 



RECAPITULATION. 



A N. E. and S. W. line of chalk bounds the drift-clay on one side of the county. On 

 the S. E. of this the clay almost immediately manifests an average thickness of about 100 feet. 



The clay gradually thins off on approaching a line, which passes through the heads of the 

 estuaries and approximately forms a boundary to both the London clay and the Crag. 



The sand underlying the drift-clay passes out over the London clay and Crag. 



The phenomena of Norfolk, though they do not readily range themselves side by side 

 with those of Suffolk, very probably accord with a southerly denudation. 



Valleys of denudation expose a ridge of. chalk along a certain well-defined line, passing 

 it approximately at right angles, and exhibit evidence of having been due to elevatory 

 transverse fracture. 



Evidence of disturbance at a date posterior to the crag is afforded by the coast-sections. 



The just-mentioned ridge of chalk bounds the London clay towards the north, but does 

 not stop the drift-clay, as patches of the latter appear south of it. 



A distinct line of sand-cliffs of uncertain geological date exists along the Gipping valley, 

 marking a period when the sea remained permanently at that level. 



