LOWER CHALK—ISLE OF WIGHT. 
79 
CHAPTER VII. 
THE LOWER CHALK IN THE ISLE OE WIGHT. 
General Description. 
The Lower Chalk of the Isle of Wight is comparable in its main 
features with that of Kent and Sussex, and many fossils have been 
obtained from its lower beds by various collectors, but no one has 
yet made a detailed study of their distribution, with a view of ascer¬ 
taining whether it is divisible into definite beds or bands charac¬ 
terised by the prevalence of certain species, as in the case of the 
Folkestone Chalk. 
By the older geologists the greater part of the Lower Chalk of 
the island was called Chalk Marl, and their Lower Chalk included 
the zone of Holaster subglobosus, together with the whole of the 
Middle Chalk, which is here without flints. 
The first attempt to divide the Chalk of the Isle of Wight into 
zones was by Professor C. Barrois,* who recognised the equivalent 
of the zone of Ammonites various , and of the division which he and 
M. Cheillonneix had termed the zone of Am. cenomanensis in the 
Pas de Calais, but he makes no mention of the highest part of the 
stage, nor of the Belemnite Marl, giving the total thickness as only 
35 metres (about 115 feet), which is much under the mark. 
Until the publication of the second edition of the Survey Memoir 
on the Isle of Wight,f no correct measurement of the beds that 
make up the Lower Chalk had ever been made. This was done by 
Mr. Strahan, who measured the component beds in the cliffs west 
of Culver Point, and found them to be about 205 feet thick, without 
including the Chloritic Marl at the base or the Belenmite Marls at 
the top. He divided this mass of Chalk into three parts, with 
relative thicknesses of 70, 50, and 86 feet, audit is undoubtedly true 
that the Lower Chalk is capable of such lithological subdivision at 
that locality, as it is at Folkestone and near Wissant on the French 
coast, but we do not think it comprises more than two zones at any 
locality. We do not find a sufficient difference in the faunas of the 
lower and middle parts to warrant their recognition as separate 
zones, and the collections made for this Memoir have proved that 
Ammonites [Schloenback ia] various ranges up through fully 100 
ieet from the base. 
* Craie de l’lle de Wight. Bibl. des Hautes Etudes, tom. xiii., 1875. 
t Briatow “Geology of' the Isle of Wight,” Ed. %■ by U Reid ami A’ 
Strahan. 1889. ' ' ‘ : 
