520 STRATIGRAPHICAL GEOLOGY 



east. From Poland and Silesia another band of chalk is believed 

 to extend across the Moscow basin, but no deposits of Upper 

 Cretaceous age have been found in Northern Russia, though it 

 seems likely that they originally spread over those of the Lower 

 Series. 



E. THE HISTORY OF THE PERIOD 



The history of Cretaceous time in Europe is the history of the 

 gradual submergence of the large tracts of land which existed in 

 the region at the beginning of the period. These tracts included 

 (1) a large area in the north which may be called the Fenno- 

 Scandian region ; (2) a western land including the British area, the 

 whole of Western France, and the greater part of Spain ; this may 

 be called the Atlantic region ; (3) a long tract extending from the 

 north-east of France through Central Europe, Bohemia, and the 

 southern part of Russia, which for want of a better name may be 

 called the Hercynio-Sarmatian land. The Atlantic and Hercynian 

 regions were connected by a broad isthmus across Belgium and 

 the North Sea, and it is also possible that there was a land -connection 

 between the Fenno-Scandian and the Sarmatian regions. 



There is fairly good evidence that some of this land rose to a 

 considerable elevation above the sea-level of early Cretaceous time, 

 because some parts of it were never entirely submerged even after 

 the deposition of several thousand feet of strata and the formation 

 of chalk below water which must have been over 3000 feet deep. 

 We know also that there were both large rivers and large lakes on 

 this continent, and we know the actual position of two of these lakes. 

 The one, known as the Wealden lake, occupied a large part of 

 Southern England with the adjacent parts of what is now the 

 English Channel. The other occupied a large area in the north- 

 west of Germany, and appears to have been connected with the 

 estuary of a river which opened into a gulf of the Northern Sea. 



With regard to the Wealden lake, I think there is no doubt 

 about its having been an enclosed inland lake with an excurrent 

 river emerging from its southern side and running south-eastward 

 through France. In spite of the views held by certain French 

 geologists, there is no good reason for believing that the Southern Sea 

 invaded the Pays de Bray or the Boulonnais before Aptian time. 

 The few species of Lamellibranchs on which they rely for the 

 presence of the Hauterivian Sea in the Pays de Bray are all found 

 in the Vectian of the Isle of Wight. The northern termination 

 of this sea appears to have been in the Haute Maine, where its 

 characteristic fauna occurs in a limestone overlying a set of 

 freshwater beds, some 60 feet thick. Such a conjunction seems 



