LATER TERTIARY GEOLOGY OF EAST ANGLIA. 89 



with few exceptions are now concealed) then no doubt cropped out 

 along the valley-sides. The degradation of these formed the chalky 

 clay shown under the letter a in sections V. and VI. About Lyng 

 and Elsing, however, the Chalk only comes out in the extreme 

 bottom of the valley, while the Contorted Drift, having lost much 

 of its brick-earth character, usually presents the appearance of a 

 gritty bed with but little argillaceous matter and full of grains of 

 chalk. The degradation of this, and, in a subordinate degree, of the 

 chalk floor also, seems to have furnished the material of the bed a in 

 this part of tho valley. The exposures of this bed along the Wensum 

 valley about Lyng and Elsing all occur on the narrow strip of Chalk 

 which crops out from beneath the Contorted Drift, and occupies the 

 valley between it and the edge of the sheet of alluvium and Post- 

 glacial gravel which skirts the river ; and they might be mistaken, 

 by any one not possessed of an intimate acquaintance with the 

 geological features of Norfolk, for the Contorted Drift itself ; but in 

 the many sections of it which occur in the neighbourhood, that 

 drift persistently maintains a different colour (tawny brown) and a 

 less sandy composition. 



Tho Upper Glacial does not reach north of the line of section IX., 

 in Central Norfolk, the country lying between the head of the Wen- 

 sum valley and the sea being occupied exclusively by the Contorted 

 Drift, overlain irregularly by the Middle Glacial. 



Near to the head of the Wensum valley a small stream takes its 

 rise, and runs northwards to the sea through this Contorted-Drift 

 area, its valley being excavated exclusively in that drift, which, in 

 much greater thickness than near Norwich, is cut through down to 

 the Chalk. The length of this valley is about ten miles ; and the 

 following line of section (No. X.) taken about midway of its length 

 shows its structure. 



Fig. 10. — Section X, across the Walsingham Valley. (Length 

 2 miles. Vertical scale 17| times the horizontal.) 



Railway- *; 

 cutting at ~ 

 Walsingham > 



Station. ps E. 



10. Postglacial valley-gravel and recent alluvium. 



The country round this part abounds in sections of the Contorted 

 Drift, which consists of a gritty white marl, a condition which it 

 gradually assumes westward along the coast section ; so that from 

 being a red brick-earth with included masses of marl in Central 

 Norfolk, forming rich mixed soil, it gradually changes into this 



