242 
THE CRETACfiOTTS ROCKS OF BRITAIN. 
Professor Barrois does not mention any sections in the Aube, 
but the Lower Chalk of that department has been described by 
M. Peron,* * who makes the thickness about 150 feet and the suc¬ 
cession as follows :—- 
3. Dry whitish chalk, with Scaphites oequalis. 
2. Massive chalk, with Holaster nodulosus. 
1. Marly chalk in regular beds, with Am. varians , Am. rotomagensis , 
A. Mantelli , and Turr. costatus. 
Passing into the Marne, we find from Professor Barrois’ account 
that the above succession is continued to Yitry. The only note¬ 
worthy change is that the highest part of the white chalk becomes 
somewhat clayey, and contains many small G-asteropods and Bra- 
chiopods ; at Mont Moret Turrilites costatus and T. tuberculatus 
were also found in it. He estimates the total thickness at 70 to 
80 feet. 
The Cenomanian facies above described is maintained by Vavray 
and Changy to Possesse and Charmont, but Cephalopoda become 
rare. Near Charmont another change begins to show itself; the 
lower grey marl becomes glauconitic, and contains also scattered 
phosphatic nodules ; moreover, it passes downwards into a dark 
green argillaceous sand without fossils. This greensand is referred 
by Professor Barrois to his zone of Pecten asper, and is regarded 
as the continuation of his “ Sables de la Hardoye ” (to be mentioned 
presently), but Professor de Lapparent speaks of it as replacing 
the marly chalk with Am. varians (craie ammonitifere).*|* The 
total thickness here appears to have diminished to between 50 and 
60 feet, and the sand rests directly on the Gaize de l’Argonne, which 
is the equivalent of our Upper Gault (zone of Am. rostratus). 
A similar succession is found near Monthois and Vouziers in the 
Ardennes, and is given by Professor Barrois as follows : — 
• - . ft. 
White marl, with Holaster trecensis , Ostrea canaliculata , 
Vermicularia umbonata , etc. - - - - - - 33 
White marl with small grains of glauconite - - - - 10 i 
Glauconitic marl, with black phosphate nodules in the middle 10 
Drak green argillaceous sand- -.20 
73 
Between Vouziers and Bethel another stratigraphical change 
"takes place, a greyish-white argillaceous marl coming in below 
the green Sables de la Hardoye. This is called the Marne de Givron 
by Professor Barrois, and is referred by him to the zone of Pecten 
asper , while M.M. Peron and de Lapparent consider it as an expan¬ 
sion of the upper part of the Gaize. It rapidly thickens northward 
till near Givron itself it is about 100 feet thick, the deposit being 
thickest where the Gaize is thinnest. The fauna of this marl will 
be discussed in the sequel. 
. _ _ _—-- 
* Notes pour l’histoire du Terrain de Craie (1887), p. 53. 
t Traite de Geologie, fourth edition (1900). 
