I 
lower chalk —Yorkshire: 227 
Above this limestone are beds of hard grey shelly stone (lnocera- 
mus Bed), succeeded by some thickness of rough greyish nodular 
or lumpy chalk, which weathers into thin platy pieces. 
Along the escarpment the thickness of this zone does not vary 
much, being apparently from 25 to 31 feet, but at Speeton it 
presents quite a different aspect, and one which recalls in some 
respects the more marly facies of the southern counties. Its thick¬ 
ness is at the same time increased to 77 feet, and some of the 
material is coloured pink. 
The zone of Offaster sphcericus also presents the same aspect 
as in Lincolnshire. At its base is a bed of grey shelly chalk, which 
is the continuation of the “ grey bed ” or Totternhoe Stone, and 
this is recognisable throughout Yorkshire. 
Above the Totternhoe Stone there is generally 3 or 4 feet of hard 
chalk, and then softer chalk with much marly matter either in 
thin seams or around lumps of harder chalk. Part of these beds is 
often coloured red or pink, but is not always so coloured. The higher 
beds consist of hard whitish chalk in regular beds, weathering into 
platy or flattish lenticular pieces. 
The thickness of the zone of Offaster sphcericus is about 40 feet 
at South Cave, and is probably rather thinner to the northward, 
but no complete section has yet been recorded near Leavening or 
Wharram. At Speeton its thickness is 44 feet, so that this portion 
of the Lower Chalk maintains a much more regular thickness 
than the lower part. 
At the summit there is everywhere a thin representative of the 
Belemnite marl. Along the course of the main escarpment this 
seems to consist of two layers—a band of yellowish marly 
chalk, and a layer of soft grey marl below, often variegated in grey 
buff, and black. Although there can be no doubt about the corre¬ 
lation of these marls, no specimen of Actinocamax plenus has yet 
been found in Yorkshire. 
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42 10 . 
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