126 



THEOBY OF SUDDEN EISE OF 



* [Ch.YII. 



them 



as c, 



ibid. 



The proof, then, of the extreme suddenness of the convul- 

 sion is supposed to be the shortness of the time which 

 intervened between the formation of the chalk and the origin 

 of certain tertiary strata.* Even if the interval were re- 



limits 



imp 



lapse of time. In strictness of reasoning, however, the 

 author cannot exclude the Cretaceous or Tertiary periods 

 from the possible duration of the interval during which the 

 elevation may have taken place. For, in the first place, it 

 cannot be assumed that the movement of upheaval took 

 place after the close of the Cretaceous period ; we can merely 

 say, that it occurred after the deposition of certain strata of 

 that period ; secondly, although it were true that the event 

 happened before the formation of all the tertiary strata now 

 at the base of the Pyrenees, it would by no means follow 

 that it preceded the whole Tertiary epoch. 



The age of the strata, both of the inclined and horizontal 



may 



mav 



going on before the animals of the Chalk period, such as are 

 found fossil in England, had ceased to exist, or when the 

 Maestricht beds were in progress, or during the indefinite 

 ages which may have elapsed between the extinction of the 

 Maestricht animals and the introduction of the Eocene 

 tribes, or during the Eocene epoch, or the rise may have 

 been going on throughout one, or several, or all of these 



periods. 



It would be a purely gratuitous assumption to say that the 

 inclined cretaceous strata (&, fig. 1) on the flanks of the 

 Pyrenees, were the very last which were deposited during the 

 Cretaceous period, or that, as soon as they were upheaved, all 



or nearly all the species 

 fossil in them were sudde 



anim 



exterminated ; yet, unless this 



can be affirmed, we cannot say that the Pyrenees were 

 upheaved during the Cretaceous period. Consequently? 

 other range of mountains, at the base of which cretac 



* Phil. Mag. and Annals, No. 58. New Series, p. 2-13. 



not 

 an- 





