802 STRATIGRAPHICAL GEOLOGY. — [Boox VI. 
differences than the Cretaceous system of Hurope. These differences 
are the records of an increasing diversity of geographical conditions 
in the history of the Continent, 
§ 1. General Characters. 

-Rocks.—In the Huropean area, as will be afterwards pointed 
out in more detail, two tolerably distinct areas of deposit can be 
recognized, each with its own character of sedimentary accumulations. 
The northern tract includes Britain, the lowlands of Central Kurope 
southwards into Silesia, Bohemia, and round the Ardennes into the 
basin of the Seine. The southern region embraces the centre and 
south of France, the range of the Alps, and the basin of the Mediter- 
ranean eastwards into Asia. In the northern area, which appears to 
have been a basin in great measure shut off from free communica- 
tion with the Atlantic, the deposits are largely of a littoral or 
shallow-water kind. The basement beds, usually sands or sand- 
stones, sometimes conglomerates, are to a large extent glauco- 
nitic (greensand). The marked diffusion of glauconite both in 
the sandstones and marls is one of the distinctive characters of this 
series of rocks. In Saxony and Bohemia the whole Cretaceous — 
system consists chiefly of massive sandstones, which appear to have 
accumulated in a gulf along the southern margin of the northern 
basin. Considerable bands of clay, occurring on different platforms 
among the European Cretaceous rocks, are often charged with 
fossils, sometimes so well preserved that the pearly nacre of the 
shell remains, in other cases encrusted or replaced by marcasite. 
Alternations of soft sands, clays, and shales, usually more or less 
glauconitic, are of frequent occurrence in the lower parts of the 
system (Neocomian and older Cenomanian). The calcareous strata 
assume sometimes the form of soft marls, which pass into glau- 
conitic clays on the one hand and into white chalk on the other. 
The white chalk is a pulverulent limestone composed of fragmen- 
tary shells and foraminifera, the upper part showing layers of flints, 
In some places it becomes a hard dull limestone breaking with a 
splintery fracture. Nodular phosphate of lime occurring on different 
horizons is extensively worked as a source of artificial manure. 
Seams of coal appear in the Lower Cretaceous series of north- 
western Germany, as well as beds of concretionary limonite. In the 
southern basin, where the conditions of deposit appear to have been 
more those of an open sea freely communicating with the Atlantic, 
the most noticeable feature is the massiveness, compactness, and 
persistence of the limestones, which cover a large part of Southern 
Kurope. These rocks from their extent and organic contents in- 
dicate that during Cretaceous times the Atlantic extended across 
the south of Europe and north of Africa, far into the heart of 
Asia, and may not impossibly have been connected across the north 
of India with the Indian Ocean. 

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