CHAPTER XV 



TERTIARY OR C^ENOZOIC TIME 



PAL/EOGENE SYSTEM 



As explained on p. 11, the Tertiary deposits are usually divided 

 into five or six groups with a nomenclature based on the pro- 

 portional number of species of Mollusca found in each group that 

 have survived to exist at the present day. But these groups 

 cannot be regarded as systems of the same palasontological value 

 as those into which the Mesozoic and Palaeozoic rocks have been 

 divided. Only two such systems can be recognised in Caenozoic 

 time, the Eocene and Oligocene divisions forming one system, the 

 Miocene, Pliocene, and Pleistocene divisions forming a second. For 

 these two systems the German geologist Hoernes proposed the 

 names Palceogene and Neogene, signifying the older and the newer 

 kind of Tertiary life, and though not altogether satisfactory names, 

 they have been widely adopted on the European continent. 



The older Tertiaries of North-western Europe occur in several 

 basins or broad trough-shaped areas, separated by parallel anticlines 

 or axes of elevation. The most northern of these is known as the 

 London basin, which, however, is only the western part of a large 

 geo-syncline extending from Belgium across the North Sea and 

 terminating in Wiltshire. A second but much smaller basin is 

 known as the Hampshire basin, extending through Sussex, 

 Hampshire, and Dorset, but bounded on the south by the sharp 

 anticline which runs through the Isle of Wight and the Isle of 

 Purbeck. A third is the Paris basin, occupying a broad depression 

 in the Chalk area of Northern France. South of this, again, are 

 the two separate basins of Aquitaine and Provence. 



Some account of the Palaeogene deposits in all these areas will 

 be given in the following pages, taking first the Eocene and 

 afterwards the Oligocene Series. 



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