242 



GEOLOGY OF THE ISLE OF WIGHT. 



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The date of the disturbances of which we 

 have a part in the Isle of Wight is known 

 to have been subsequent to the deposition of 

 the Hamstead Beds (Middle Oligocene) by 

 the fact that these strata share in the tilting 

 up of those along the central range. There 

 is no evidence of the movement having com- 

 menced in an earlier period. Had such been 

 the case, there would have been a tendency 

 in the Tertiary formations to thin away 

 against the anticlinal folds. On the other 

 hand, the movements have been proved to 

 have been earlier than the Pliocene.. For on 

 the North Downs, near Lenham,* we find 

 Lower Pliocene deposits resting directly on 

 the Chalk, the absence of all the older 

 Tertiary strata being clearly due to the 

 denudation that resulted from the upheaval 

 of the Weald anticline. The date of the 

 disturbances may thei-efore be assigned ap- 

 proximately to the Miocene Period. 



As will be presently seen, the fixing of this 

 date is of special interest, for the production 

 of the folds directly determined the courses 

 taken by most of the South Country rivers. 



As is often the case where beds have under- 

 gone much folding, there are comparatively 

 few faults in the Isle of Wight. The few 

 which have been observed produce only a 

 trifling effect on the position of the outcrops, 

 and have had no share vv^hatever in pro- 

 ducing the physical features of the Island. 

 They have been noted in the course of the 

 detailed descriptions of the sections, but we 

 may enumerate them here for the purpose of 

 comparing their directions. The amount of 

 throw is uncertain in every case, but always 

 insignificant, except at Ashey (p. 114). 



Ashey. Chillerton Down, 



ComptonBav? W. 30° S. and S. 



(p. 8). ^ 25° W. 



Carisbrook, W. 15 



s. 



St. Catherines, 



W. 11° S. 

 Commencing with 



Culver Cliff, W. 30° S. 

 Little Stairs Point, 

 E. 20° S. 



the northern half of 



the Island, we see at once from the map that 

 the most important feature in that district is 



* Clement Reid, On the Pliocene Deposits of North West Europe. Nature, vol. 34, 

 p. 341. 1886. 



