LOWER CHALK —NORTH-EAST OF FRANCE. 
243 
The Marne de Givron forms the hills between Chaumont 
Porcien, Bocquigny, Draize, and St. Jean du Bois. It passes up 
into the Sables de la Hardoye without any break, the marl becoming 
sandy, and this changing to a sand composed of quartz grains and 
large grains of dark green glauconite. The marl contains a fair 
number of fossils, but the sands very few ; neither the one nor the 
other contains phosphatio nodules. The overlying bed of glau¬ 
conitic marl does contain such nodules, black, and apparently 
derived, and this bed Prof. Barrois regards as the equivalent of the 
zone of Ammonites latidavius . 
In the north of the Ardennes the “ marne de Givron ” becopies 
very thin, and in the Aisne it thins out entirely, allowing the “ sables 
de la Hardoye ” to rest directly on the Gaize de Marlemont. All 
the beds become thinner, and green grains appear even in the white 
marls (zone of Bel. plenus). In the north of the Aisne the succession 
is as follows : — 
ft. 
White marls with green grains, Bel. plenus - about 12 
Glauconitic marl with phosphate nodules - - - 20 
Bright green glauconitic sand. 
32 
Department du Nord.— The succession described as occurring 
in the north of Aisne (Hirson and Mondrepuits) appears to be con¬ 
tinued in the Department du Nord, but on crossing the boundary 
between these Departments we enter the country where the Ceno¬ 
manian rests on the Palaeozoic rocks, and where all such deposits 
are locally known as Tourtia. Professor Barrois believes that the 
“ glauconie de la Hardoye ” runs on through the arondissement 
of Avesnes, but he prefers to call it here the “ Greensand of Avesnes.” 
One of the most celebrated localities for Tourtia is that of Sas- 
segnies, about seven miles north-west of Avesnes, and here the 
Cenomanian basement bed is a yellowish sandy marl with limonite 
and pebbles and many fossils, its thickness being about 3 feet 
Above it is a marly glauconitic sand with fewer fossils, but con¬ 
taining Pecten asper, Exogyra conica , Ostrea phyllidiana , and 0. 
vesiculosa , all of which occur in the bed below. 
Professor Barrois is inclined to regard the lower bed as a repre¬ 
sentative of the marne de Givron , and the higher as the greensand 
of Avesnes , but he expressly says that he has some hesitation in 
suggesting such a correlation. We would remark that the marne 
de Givron, having once thinned out against the Palaeozoic shore, 
is not likely to set in again on the south side of the axis of Artois ; 
hence w T e think that the two beds at Sassegnies are merely littoral 
representatives of the central part of the Cenomanien. The 
fauna they contain is of a generalised shallow water Cenomanian 
type like that of the Gres du Maine in the west of France, and 
includes the following species, 
4219. 
R 
