LOWER CHALK —NORFOLK. 
207 
Above tlie Totternlioe Stone there is some thickness of hard 
grey chalk, irregularly bedded in the lower part, but smoother 
and more blocky above. This passes up rapidly into white chalk, 
which becomes very hard in the northern part of the county. Be¬ 
tween Stoke Ferry and Gay ton the thickness of chalk between the 
Totternhoe Stone and the summit of the Lower Chalk is probably 
not less than 50 feet, but near Hunstanton it is only 36 feet. 
The Belemnite Beds at the top of this zone are represented in 
the southern part of the county by a layer of yellowish marly chalk 
enclosing lumps of hard white chalk. This extends as far north 
as Hillington, but then becomes a mere parting, and is not dis¬ 
tinguishable near Hunstanton, where the hard Lower Chalk and 
the Mel bourn Rock make a continuous face in the quarries. 
Stratigraphical Details. 
Zone of Ammonites varians. 
Several small quarries expose the higher part of this zone between 
Hockwold Grange and Feltwell St. Nicholas, but a complete section 
of the zone was obtained by a boring made for Mr. W. Hill and the 
author in the quarries at Stoke Ferry.* The results of this, com¬ 
bined with measurements of the beds seen in quarry, are shown in 
the diagram, Fig. 49. 
The intercalation of hard beds with the softer marly beds is here 
very conspicuous ; most of the harder courses are shelly, but that 
which commences 11 feet above the basement bed is less shellv, 
and has a special structural aspect which is different from that of 
ordinary Chalk Marl (see p. 282). 
The highest part of the zone also consists of blocky, compact, 
dull white chalk, about 24 feet thick, which is hard enough to 
resound under the hammer. This likewise is largely composed 
of fine calcareous material, the shell fragments and glauconite 
grains being all very small. This hard chalk contains Holaster 
subglobosus, which is absent from or very rare in the Chalk Mail 
of the more midland counties. 
The basement bed, still glauconitic with many small green- 
coated phosphatic nodules, is exposed in a small pit by the roadside 
south of Shouldham Church. It is here overlain by rather hard 
yellowish chalk in lumpy irregular beds, like that which was found 
in the Stoke boring from 11 to 21 feet above the basement bed ; 
lienee it would seem that the intervening 11 feet of soft marl has 
either thinned out oi* has changed laterally into a harder and more 
oalcareous chalk. 
There is no other good exposure of Chalk Marl till we come to 
Grimston, and here, at the Sow’s Head spring, the base of the Chalk 
is again seen. It consists of a very hard solid limestone, weather- 
* See Quart.- Journ. Geol. Soc., Vol. xlni., p. 556 (1887). 
