Tlie Pencplai)!. — Davis. 231 
dissected plateau region of to-day was a lowland of denudation 
in Tertiary time. 
The highlands of the Ardennes along tlie border of France 
and Belgium is another part of the ancient Hercynian range, 
greatly denuded. It descends southward, where it is over- 
lapped by Alesozoic formations, among which the Cretaceous 
strata are of special interest in the present connection. A belt 
of coal measures extends from the Ardennes southwestward 
under the Cretaceous ; shafts have been sunk through the Cre- 
taceous to the coal measures at many points, and thus the form 
of the buried denuded surface has been determined with much 
accuracy. Gosselet's elaborate "Memoire sur I'Ardenne"* 
(Paris. 1888) gives much information concerning both the bur- 
ied and the unburied portions of the denuded mountains. The 
frontispiece shows the valley of the Meuse incised in the plat- 
eau, "'everywhere leveled to the same altitude." Many sections 
in the text show the INIesozoic strata lying on the deformed 
and denuded Paleozoic rocks, but the basal deposits beneath 
the Cretaceous are usually not marine. Even under the Ju- 
rassic, there is a ferruginous clay with limonite concretions, 
thought to be of terrestrial origin ( 1. c.,p. 802). Under the Cre- 
taceous strata, the most general deposit is a layer of black pv- 
ritous clay with vegetal remains, taken to represent the soil of a 
pre-Cretaceous land surface. Fluviatile and lacustrine deposits 
are also recognized. The Carboniferous limestone is often pitted, 
and the pits contain non-marine materials and fossils. Where 
the intermediate deposits are wanting, the ancient rocks are 
perforated by boring mollusks and strewn with shells of ovs- 
ters and serpuls (p. 808, 810). On the uplands at a consider- 
able altitude, and far beyond the main overlap of the Mesozoic 
cover, there are scattered remnants of Cretaceous andTertiarv 
deposits, and these are all regarded as of earlier date than the 
elevation and dissection of the plateau (p. 831). Fuller details 
as to the composition and distribution of these deposits are 
given in other papers by Gosselet (Ann. Soc. geol. du Nord, 
vii, 1879, 100) and Barrels (Ibid., vi, 1879, 340). Bertrand 
says that the buried pre-Cretaceous surface is a denuded plain, 
and that its existing irregularities are due, at least in great 
*Ardenne is the name of a department of France; Ardennes, of the 
Highlands themselves. 
