102 
RED AND NORWICH CRAGS. 
Eed Grag here rests on an eroded surface of the lower divisionj 
as is the case at Eamsholt. (Fig. 23.) 
Fig. 23. 
Section in BallasU'pit^ Aldborough. 
(Prestwich. Quart. Journ. Geol. Soc., vol. xxvii. p. 335.) 
2. Brown Sands, with few shells and pebbles: upper division, 10 feet. 
1. Shelly Red Crag; lower division 10 feet. 
Crossing the marshes of the Hundred Eiver we find that the 
Coralline Crag has entirely disappeared, and that the lower part 
of the Eed Crag is also below the sea-level. Thus the pits around 
Thorpe are entirely in beds corresponding closely with the more 
estuarine deposits of the Norwich district, and the Crag here has 
always been considered to belong to the Norwich Crag. The 
best section is seen in the well-known Aldborough Thorpe Pit ” 
of geologists, which lies close to the southern edge of Aldringham 
Common and about three-quarters of a mile north-west of the 
village of Thorpe.* The Crag is light-coloured, like the Norwich 
Crag, and contains an assemblage of fossils identical with that 
found in the lower bed at Norwich, though in the number of 
individuals Arctic species are perhaps not quite so common. 
Prof. Prestwich gives a list of 28 species of moilusca from this 
pit, all of them occurring also at Norwich. 
In Thorpe Cliff there is now no section of the Crag, and from 
Thorpe northward to Sizewell Glacial beds extend below the sea- 
level. At Sizewell the Crag rises well above the beach and 
the inland marshes, and is exposed in several pits. One of these, 
at the northern end of Sizewell Cliff, about 200 yards inland, is 
in very shelly sand (of littoral and estuarine character) mostly 
white, but somewhat ferruginous above, and containing many 
bands and lenticular masses of limonite .... Similar Crag 
is met with in Sizewell Gap and half a mile west of it.”t Other 
* It may save confusion to point out that there are several places called Thorpe 
in Norfolk and Suffolk, and that two of the best known Norwich Crag sections are 
respectively at Thorpe near Norwich, and Thorpe near Aldborough. 
t Whitaker, Geology of Aldborough, See. (^Memoirs of the Geological Survey')^ 
p. 25. 
