THE CRETACEOUS PERIOD 



253 



region continued to be submerged under sea water. Soon after 

 the beginning of the Cretaceous, a more or less interrupted 

 marine transgression caused considerable areas of western and 

 central Europe to become submerged, the deposits including both 

 marine and non-marine beds. At the same time marine waters 

 were more extended over the southern part of the continent. Map 



Fig. 156 



Sketch map showing the relations of land and water in Europe during 



Lower Cretaceous time. (Slightly modified after De Lapparent.) 



Fig. 156 affords a general picture of the relations of land and water 

 at that time. In western and central Europe all types of common 

 sedimentary rocks were formed, as well as some beds of coal in 

 Germany. As would be expected, because of the more prevalent 

 marine conditions in southern Europe, limestone was more com- 

 monly formed there. The conditions just described continued 

 essentially till the close of the Lower Cretaceous, when only com- 

 paratively slight sea retrogressions took place, as proved by the 

 fact that the Upper Cretaceous rocks usually rest conformably 



