188 
CROMER FOREST-BED. 
Unworn Chalk flints 
Greenish chert - - O 
Cherty sandstone with fossils - j 
Ruhbly limestone with Pecten de-~\ 
missus - - - J 
Well-worn pebbles of white or”^ 
cream-coloured fine-grained | 
quartzite, vein-quartz, black or 
purple grit, hard coarse sand- | 
stone, fee. - - «J 
Angular fragments of a fine-^ 
grained green or bluish slaty 
rock - - - - y 
Carboniferous Limestone chert - | 
Fragments of Hyalonema - J 
Felstone. 
Granite. 
Upper Chalk. 
Greensand or 
Neocomian. 
Oolite. 
Pebble-beds of 
unknown age. 
Carboniferous. 
In these Pre-glacial beds few igneous rocks occur. With the 
exception of the single large granite boulder already mentioned 
and one of felstone, none were met with. The liver-coloured 
quartzites so characteristic of the Triassic conglomerates in the 
Midland Counties are also missing; so that, even if the pebble-bed 
is of Triassic or Permian age, it cannot have been derived from 
those rocks in the Midland Counties. In fact, if the river had 
flowed from the south, west, or north, it must have brought a 
quite diflerent collection of^ stones. From the north-east it 
would probably flow entirely over Chalk. It therefore seems 
that only from the south-east and east could the stones be 
derived. The evidence appears to point to a river flowing 
(tracing it towards its source) first over the Lower Tertiary basin 
which we know exists east of Yarmouth, then over Chalk, 
Greensand, and Oolite, and a conglomerate perhaps of Cretaceous 
or Neocomian age, which may have overlapped against the Palaeo¬ 
zoic rocks, as beds of that age are known to do near Harwich. 
The Palaeozoic rocks probably came to the surface as part of the 
old ridge which Mr. Godwin-Austen has described. From them 
the angular pieces of slate and carboniferous-limestone chert 
may have been derived. 
That the river must have been large is shown by the 
uniformity of the composition of the gravels at considerable 
distances apart; the gravel of a small stream will generally be 
of local origin. From the size and angularity of many of the 
stones it is evident that they must have been brought down by 
river-ice. This would not necessarily point to a more arctic 
climate than that of Norfolk at the present day, for during 
severe winters the ice-floes on the Thames are quite capable of 
transporting the largest of the boulders. Prof. Prestwich 
remarks* that on the table-land above the Meuse, in Belgium, 
Quart. Journ. Geol. Soc., vol. xxvii., p. 477. (1871.) 
