Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/333

 MIDDLE CRETACEOUS.

1st. Rhotomagian stage (Turrilites costatus, Lamk.), wanting.

2nd. Gardonian stage, with lignites 6 metres.

3rd Carentonian Stage

(a) Lower portion, with Sphoer. foliaceus and Ostrea biauriculata ("Bancs a Ostracees" de M. d'Archiac) 67

(b) Upper portion, with Inoc. labiatus and Amm. rusticus (base of the chalk marl and lower chalk) 25

4th. Angoumian stage, with Radiolites lombricalis (wanting in England) 40

5th. Provencian stage, with Hippurites organisans, Desml. (wanting in England) 37

175

UPPER CRETACEOUS.

1st. Coniacian stage (Gres de Cognac) (wanting in England) 40 metres.

2nd. Santonian stage (of Saintes) (superior Lower Chalk = chalk- marl, upper part) 65 "

3rd. Campanian stage (Champagne de Cognac = Upper Chalk) 70 "

4th. Dordonian stage (wanting in England) 15 "

190 "

These divisions, which are perfectly well marked and of considerable thickness, and possess peculiar faunas and composition, evidently differ very much from what we may observe in the basin of the Seine and in England, where we pass directly from the chalk marl (Rhotomagian stage) to the Lower Chalk, and thence to the Upper Chalk without the intervention of the Carentonian, Angoumian, Provencian, and Coniacian stages.

The coast of Provence, however, presents a still more gigantic development of the Cretaceous formation (see fig. 2), and such material differences from what is met with elsewhere, that in order perfectly to understand the connexion which exists between the system of the south and that of the north of France, an intimate knowledge of the localities is necessary, and the help of fossils is indispensable. And here I may appeal to those English geologists who have had the opportunity of examining our strata.

Without speaking of the Neocomian strata, the lower greensand, with Diceras Lonsdalii, the Speeton clay, and the gault, which do not offer any very striking peculiarities, I shall pass at once to the middle and to the upper Cretaceous beds, briefly describing their composition, and their equivalents in England.

It may perhaps be advisable, on account of its fauna and difference of position, to separate the upper from the lower part of the Carentonian stage, and to form for it another stage, which I shall propose to call the Ligerian. This will have the advantage of giving to the beds with Inoceramus labiatus an autonomy of their own, and will prevent their being confused, as they must be in the basin of the Loire and in England, with the limestones of the same colour which succeed them without the interposition of the intermediate stages which separate them in Provence, and which contain completely different faunas.