CHAPTER XIV 



THE CRETACEOUS SYSTEM 



A. NOMENCLATURE AND SUBDIVISIONS 



THIS system takes its name from creta, the Latin word for chalk, 

 because this well-known rock forms a conspicuous part of the 

 system in Western Europe. Beneath the chalk, however, there 

 is a variable series of marine sands and clays, and below these in 

 the south of England there is a great thickness of freshwater 

 deposits which have long been known as the Wealden, from the 

 large area occupied by them in the Weald of Kent and Sussex. 

 In the British area it is only in Yorkshire and Lincolnshire that 

 marine deposits of the same age as the Wealden are found, but 

 in other parts of Europe they attain a great thickness. 



The system is divisible into two great series, a Lower and an 

 Upper. On the European continent the whole system consists of 

 marine deposits, and a complete sequence is also found in the north 

 of England (Lincolnshire and Yorkshire), but in the south of 

 England the lower part is represented by the freshwater Wealden 

 Beds, overlain by some marine deposits which were formerly and 

 are still often called the Lower Greensand, but for which Vectian is 

 a much better name. 



The marine facie* of the Lower Cretaceous Series is most fully 

 developed in the soutli of Europe, and the nomenclature of its divi- 

 sions is taken from places in the soutli of France and in Switzer- 



" It is high time that the names Upper and Lower Greensand were 

 abandoned, for they were proposed by Webster at a time (1824) when the 

 beds between the Chalk and the Wealden were regarded as the "Greensaud 

 Formation." Thus they only perpetuate erroneous views of classification, 

 and are, moreover, cumbrous and misleading, for the "Lower Greensand" is 

 more often yellow or brown than green. Hence it is desirable that the name 

 Vectian (altered from the Vectine of Fitton) should be adopted instead of 

 Lower Greensand, while the "Upper Greensand" falls into the group of 

 beds for which the name Selbornian has recently been proposed. 



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