260 
CRETACEOUS SYSTEM IN ENGLAND AND FRANCE. 
Wealden. This deposit, feebly represented in France, but clearly recognizable in 
Hanover', is not traceable throughout Eastern Germany; and has no representa- 
tive in Poland or Russia. In reference to our subject, therefore, it is unnecessary 
to enter upon the discussion which at present occupies geologists, as to the precise 
marine equivalents of these estuary and freshw r ater beds in other parts of the Eu- 
ropean basin. The Wealden group of the British Isles is surmounted by a thick 
Cretaceous system, divided, in ascending order, into the following formations : 
— 1. Lower Greensand. 2. Gault. 3. Upper Greensand ; and 4. Chalk. As the 
lowermost of these masses, of considerable dimensions and of varied structure 
has been recently found to contain in England many fossils characteristic of the 
“ Terrain Neocomien ” of Swiss and French authors, it is clear that the latter 
formation, which extends through the south of France, is simply a largely developed 
inferior member of the Cretaceous system, under a certain mineral type, and with 
some peculiar fossils. With this deposit we have, however, a little more concern 
than with the Wealden, for although its lower and peculiar part does not, as far as 
we know, exist in Eastern Germany or Poland, it appears in the Crimsea and 
southern limits of Russia 2 . But putting aside the lowest greensand of English 
geologists, which with its continental equivalent the Neocomian must be consi- 
dered the true base of the Cretaceous system, it may be stated, that even within 
the kingdom of France it has been ascertained, that the cretaceous subdivisions in 
the south of that country are essentially distinct from those of the north. In the 
latter, as in England, the white chalk is underlaid by bands which respectively 
represent the Upper Greensand and Gault, with some development of a Lcwer 
Greensand ; whilst in the southern provinces the last-mentioned deposit, contain- 
ing much calcareous matter, is at once surmounted by white limestone, which 
passes under tufaceous marlstone, the whole series terminating upwards in yel- 
lowish-white and gray chalk. And yet, notwithstanding this great discrepancy in 
1 See Roemer’s Versteinerungen des N. Deutsch. Oolith. Geb. 1836. 
2 It is right to observe, that some Neocomian shells, similar to those which occur in the lowest beds of 
the greensand of the Isle of Wight, have been found near Kislavodsk, at the northern foot of the Cau- 
casus. We state this on the authority of our colleague Count Keyserling, with whom we examined 
the coast-section at Atherfield in the Isle of Wight in the spring of 1S42, and thence suggested that it 
would prove to be the equivalent of the Neocomian strata of foreign geologists. (See Proc. Geol. Soc., 
vol. iv. p. 112, and the memoirs of Mr. Austen and Dr. Fitton, Proc. Geol. Soc. vol. iv. pp. 170 and 198.) 
M. Dubois de Montpereux had previously ascertained the presence of Neocomian strata in the Crimsea. 
His detailed sections of the whole cretaceous series, as exhibited in the cliffs of this country, are most 
instructive. (See Voyage au Caucase, &c., Fifth Ser. pi. 10. f. 13.) 
