THE CRETACEOUS PERIOD. 



169 



Upper Cretaceous beds spread beyond the Lower, having notably 

 greater extension both in the central and southern parts of the country. 

 In central Russia, the uppermost beds of the system have little develop- 

 ment, though they are of importance farther south, covering wide 

 areas south of latitude 55°. 



As in the case of the Lower Cretaceous, the Upper Cretaceous of 

 southern Europe is notably unlike that of the central province. While 



Fig. 407. — Sketch-map of Europe showing the relations of land and sea (shaded area) 

 during the Cenomanian epoch. (After de Lapparent.) 



clays and marls are common, limestone is still the dominant formation 

 in the southern province, where clear waters still prevailed. From a 

 characteristic genus of fossils, much of the limestone of the system 

 is known as the Hippurite limestone. 



The most notable petrographic feature of the Upper Cretaceous 

 system of Europe is the abundance of chalk. Both in England and 

 France it attains an aggregate thickness of several hundred feet, though 

 much of it is far from pure. It grades into marls and clays on the 

 one hand, and into sandstone on the other. The lowest chalk-beds occur 



