PEBBLE GRAVELS. 
199 
belong either to the Weybourn Crag, or to the Forest-bed, 
(see p. 137). 
A considerable area occupied by similar pebbly gravel has 
been mapped on the low land between Hickling and Barton 
Broads, and in the adjoining portion of the valley of the Bure. 
There is little doubt that these overlie the Chillesford Clay, but 
this is all that can be said about them. In the upper part of 
the Bure Valley the pebbly gravels are quite inseparable from 
the Norwich Crag, and have already been described with that , 
formation. 
Around Norwich pebbly gravel with seams of laminated clay 
commonly overlies the undoubted Norwich Crag. As a rule 
these strata are unfossiliferous, but at one or two points seams of 
ironstone contain casts of shells. This appears to show that the 
absence of fossils at other localities is merely due to the complete 
decalcification of the gravels. No evidence has yet been obtained 
that will justify the correlation of the pebble gravels near 
Norwich, with one rather than another of the divisions noticed 
on the coast. The strata can be well seen at the Bishop’s Bridge, 
or Lollard’s Pit, in Norwich. Here Prof Prestwich describees 
them as “ white sands, and flint shingle (Westleton beds),” and 
gives the thickness at 20 feet.* At the pit at Thorpe Kiln, casts 
of shells occur in a seam of ironstone above the Chillesford Clay. 
The species recorded by Mr. H. B. Woodward! are:— 
Littorina littorea. 
Purpura lapillus. 
Oardium edule. 
Modiola (large sp.). 
Mya arenaria. 
Mytilus edulis. 
Nucula Oobboldiae. 
Tellina balthica ? 
--obliqua. 
There is nothing in this list to fix the age of the deposit, as 
Tellina balthica, the only species of importance from this point of 
view, is a doubtful determination. 
Near Keedham the shingle so conspicuous in the railway cut¬ 
tings, forms a mass of 25 feet or more in thickness, and seems to 
lie between the lower Boulder Clay and the Chillesford Clay. 
In composition it consists mainly of flint, pebbly and subangular, 
and quartz pebbles. The sections of it, fully described by Mr. 
Blake in the Norwich Memoir, throw no light on the question of 
the age of the gravels. Around Beccles the deposits are more 
sandy, though otherwise similar. The pebble gravels are often 
cut out or overlapped by newer strata between Beccles and 
Bungay, and seldom rise to any great height above the marsh 
level. 
In the tributary valley that extends from Ditchingham west¬ 
ward to Bedingham, the gravels become of greater interest, for 
though still unfossiliferous, their lithological character is sin¬ 
gularly like that of the Forest-bed gravels at Bacton(seep. 170). 
* Quart. Journ. Geol. Soc., vol. xxvii., p. 462. (1871.) 
t Geology of the Country around Norwich {Mem. Geol. Purvey), p. 75. 
