CHAPTEK XVI 

 NEOGENE SYSTEM 



MIOCENE AND PLIOCENE SERIES 



THE Newer Tertiary strata, i.e. those which are newer than the 

 Oligocene Series, have so much in common, both as regards their 

 mode of occurrence and the species of fossils which they contain, 

 that they can hardly be considered to form more than one system, 

 and even when so grouped together it is only in the south and 

 south-east of Europe that they constitute a series of deposits 

 comparable in thickness and extent to those of older systems. 



As explained 011 p. 526, the name Neogene will be adopted for 

 this system, and it will be regarded as including the three groups 

 or series which were termed Miocene, Pliocene, and Pleistocene by 

 Lyell. It is true that many geologists, both in this country and on 

 the Continent, exclude the Pleistocene from the Neogene System 

 and place it in what they call a Quaternary or Post-Tertiary 

 System, but the only essential difference between the Neogene and 

 the Quaternary is that the remains of man have hitherto only been 

 found in the latter. It would, however, be rash to say that man 

 did not exist during the later part of Pliocene time, and thus the 

 distinction on which a Quarternary System is based must be 

 regarded as an assumption. No hard-and-fast line can be drawn 

 between deposits of Pliocene and Pleistocene age, and from a purely 

 geological point of view it is more logical and correct to say that 

 Tertiary time merges into the Recent or Historic period than to 

 imagine that Tertiary time ended when man first appeared. 



When the Miocene, Pliocene, and Pleistocene Groups were 

 established by Lyell the percentage of living species of Mollusca in 

 each fauna was taken as a guide and as a criterion of age, but subse- 

 quent researches have shown that the percentages originally adopted 

 by Lyell cannot be sustained, and that if the principle is to be retained 

 the proportional numbers must be altered, and further, that much 

 latitude be allowed in certain cases. It may be considered, 

 however, that the Miocene molluscan fauna has only from ten to forty 



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