82 
RED CRAG. 
1886'^ and 1887t the rest of the Geological Survey Memoirs 
referring to that region appeared. 
From the foregoing historical account of the literature relating to 
the Eed Crag it will be understood that there is no definite division 
between Ked Crag and JS^orwich Crag, and that if we here keep 
them separate it is more as a matter of convenience in describing 
different areas than as indicating any leaning to the opinion that 
they represent distinct periods. What appears to happen is, that 
successive stages of the upper Crag overlap each other as they 
are followed northward. At the southern extremity of the area, 
at Walton, we find the oldest Ked Crag, a deposit'yielding a 
fauna closely allied to the Coralline Crag. A few miles north¬ 
ward this is -lost, and the Red Crag of Sutton and Butley, with 
many arctic mollusca, rests directly on the Coralline Crag. 
Above the typical Red Crag near Butley comes a higher and 
lighter coloured division, the Scrobicularia Crag of S. Y. 
Wood, which seems to correspond very closely with the Norwich 
Crag. Proceeding northward we pass an area where the strata 
maybe called either Red Crag or Norwich Crag; but in the 
Waveney Valley the upper division has overlapped the lower 
ones and rests directly on Eocene or Chalk, the strata belonging 
undoubtedly to the Norwich Crag type. A corresponding overlap 
to the northward of still newer beds causes the Weybourn Crag, 
which in the Bure Valley overlies the Norwich Crag, to rest 
directly on the Chalk near Cromer. 
For the purpose of this Memoir it will scarcely be necessary to 
describe all the sections in the Red Crag, especially as the details 
will be found in the Geological Survey Memoirs relating to the 
different areas. Instead of going over the same ground again we 
will select the sections of interest, and those illustrating the changes 
the deposits undergo as they are traced northward. We shall by 
this means avoid overloading the Chapter with detail, for Crag 
pits are found in hundreds, and are constantly becoming over¬ 
grown, or are ploughed over, while others are opened. 
A glance at the Map which forms the frontispiece to this 
volume will show better than any description the area over which 
the Red Crag extends. But it should not be forgotten that the 
present extent of the strata does not necessarily correspond with 
their original importance, and that, to the southward at any rate. 
Red Crag must once have covered a wider area, for outliers cap 
several of the hills. An outlier at Sudbury shows that it must 
also have extended further to the west. 
Commencing with the southernmost of these outliers—that on 
the low hill at Walton Naze—we find a thin stratum of Crag, 
occasionally shelly, lying between the London Clay and some 
newer clays apparently belonging to the Chillesford Series. If it 
were not for the interesting fauna found in this sand, little notice 
* The Geology of the country around Aldhorough, Framlingham, Orford, and 
Woodbridge. (^Memoirs of the Geological Survey'), pp. 12-19. 
I The Geology of Southwold, and the Suffolk Coast from Dunwich to Covehithe. 
Ibid., pp. 6-15. 
