hi] tertiary period. 51 



expression of climatal zones similar to those recognised in Ju- 

 rassic times. In North America, Cretaceous rocks are spread over 

 a wide area, also in North Africa, India, South Africa, and other 

 parts of the world. Within the Arctic Circle strata of this age 

 have become famous, chiefly on account of the rich flora de- 

 scribed from them by the Swiss palaeobotanist Heer. The fauna 

 and flora of this epoch are alike in their advanced state of 

 development and in the great variety of specific types; the 

 highest class of plants is first met with at the base of the 

 Cretaceous system. 



XI. Tertiary. 



" At the close of the Chalk age a change took place both in 

 the distribution of land and water, and also in the development 

 of organic life, so great and universal, that it has scarcely been 

 equalled at any other period of the earth's geological history ^" 

 The Tertiary period seems to bring us suddenly to the threshold 

 of our own times. In England at least, the deposits of this age 

 are of the nature of loose sands, clays and other materials con- 

 taining shells, bones, and fossil plants bearing a close resemblance 

 to organisms of the present era. The chalk rocks, upheaved from 

 the Cretaceous sea, stood out as dry land over a large part of 

 Britain; much of their material was in time removed by the 

 action of denuding agents, and the rest gradually sank again 

 beneath the waters of Tertiary lakes and estuaries. In the 

 south of England, and in north Europe generally, the Tertiary 

 rocks have suffered but little disturbance or folding, but in 

 southern Europe and other parts of the world, the Tertiary 

 sands have been compacted and hardened into sandstones, and 

 involved in the gigantic crust-movements which gave birth to 

 many of our highest mountain chains. The Alps, Carpathians, 

 Apennines, Himalayas, and other ranges consist to a large extent 

 of piled up and strangely folded layers of old Tertiary sediments. 

 The volcanic activity of this age was responsible for the basaltic 

 lavas of the Giants' Causeway, the Isle of Staffa, and other 

 parts of western Scotland. 



1 Kayser and Lake (95), p. 326. 



4—2 



