600 STRATIGRAPHICAL GEOLOGY 



authors that what has been called Chillesford Crag or Aldeby 

 Beds is in most localities indistinguishable from Norwich Crag, 

 but lie differs from them in regard to the sand below the clay at 

 Chillesford, which he regards as belonging to the Chillesford Beds, 

 believing it to be an exceptional bed without a parallel elsewhere. 



The Chillesford Beds consist of finely laminated clay and sand, 

 always micaceous, lying horizontally, and often in alternating layers 

 of clay and sand. They are often from 18 to 20 feet thick ; they 

 rest indifferently on the Coralline, the Eed, and the Norwich Crags, 

 and have been traced from Walton-on-Naze to Mundesley in 

 Norfolk, a distance of about 90 miles. Mr. Harmer has pointed 

 out that when the exposures of these beds are plotted on a map 

 they arrange themselves in the form of a sinuous band of gradually 

 increasing width as it is traced northward, a form which suggests 

 that they were formed in the estuarine portion of a large river 

 flowing from south to north, and if this was so, the river was 

 probably a continuation of the Rhine. 19 



Weybourn Crag This is only found in the north of 

 Norfolk, and takes its name from Weybourn on the coast near 

 Cromer, where it consists of from 1 to 12 feet of loam and sand with 

 a band of blue clay in the lower part and a basement bed of unworn 

 flints resting on the Chalk. Its characteristic shell is Tellina 

 balthica, which is very abundant and is a northern species that does 

 not occur in the older crags. Out of fifty-three species of Mollusca 

 only five are extinct, and all the rest are such as now live in the 

 North Sea, nine being regarded as Arctic forms, which is a larger 

 proportion than occur in the Norwich Crag. The fauna, therefore, 

 seems to indicate that the Weybourn Crag is newer than the 

 Norwich Crag, and Mr. Harmer believes it to be newer than the 

 Chillesford Beds. 



Cromer Beds. These beds are exposed at intervals along the 

 Norfolk coast from Happisburgh to Weybourn. They have been 

 described by many writers, and were carefully explored for the 

 Geological Survey by Mr. C. Reid, who found the general 

 succession in these cliffs to be as follows : 20 



Feet. 



Pleistocene ( Glacial de P osits 



\Lcda myalls Bed . . . . . . 4 to 15 



/"Upper freshwater bed 'I 



pi. | Forest bed (estuarine) > Cromer Forest Bed . 10 to 20 

 1 Lower freshwater bed] 

 V Weybourn Crag 1 to 12 



The Lower freshwater bed is a local and discontinuous deposit, 

 its relation to the central estuarine portion resembling that of more 

 recent "submerged forests" to the mud of modern estuaries. The 



