252 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 25, 



southward. 8ince however no general movement of depression of 

 the strata on the north could have produced the corresponding angle 

 of elevation, with the sands below as a fulcrum, it follows that this 

 angle of elevation must have resulted from an elevatory force acting 

 from the south, and consequently must have been the one passing 

 through the Alum Bay strata. 



At White Cliff Bay the effects of this disturbance are far more 

 distinctly marlvcd in the fluvio-marine beds. All the lower green 

 marls and limestones exhibit through a thickness of 300 feet a dip 

 varying from 80° to 85°. The operation of the disturbance ends 

 rather abruptly about the centre of the series. At this point the 

 limestone strata Nos. 32 and 34 outcrop at an angle of 82°, but 

 curve immediately and rapidly, and resume, without break, and at a 

 short distance to the northward, a position nearly horizontal. (See 

 PI. IX. fig. 2.) 



It appears therefore that this important disturbance took place 

 subsequently to the formation of the whole of the Isle of Wight 

 tertiary series, but that there is no evidence to show its exact age*. 

 Unlike the slow and comparatively tranquil changes of level in pro- 

 gress during the period we have treated of, this last and great change 

 appears to me to have been one of active agency and of compara- 

 tively short duration. 



EXPLANATION OF PLATE IX. 



Fig. 1. Section exhibited at White Cliff Bay, at the Eastern end of 

 THE Isle of Wight. 





0. a 



c 

 o 

 n3 



Description of Strata. 



Gravel on the top. 



38. Striped yellow, grey, brown and 

 greenish clays with marly sands and a thin 

 layer or two of hard indurated marl and a 

 few seams of shells. 



37. Green, and mottled red and green 

 clays and marls. 



36. Dark grey clay beds and light-co- 

 loured indurated marl with Ostrea. A few 

 rolled flint pebbles. 



35. Vei7 light-coloured marl passing up- 

 _^wards into dark green marl. 















^ 



r§ 











<u 



'.2 





•rj 



> 





M 



1 





(U 





6 







• fH 







> 







^ 











E 







Feet. 



50? 

 45 



10 

 5 



110 



Association of genera and 



characteristic species in the 



chief fossiliferous beds. 



37. 

 Melanopsis fusiformis. 

 Paludina lenta. 

 Melania fasciata. 

 Cyrena obovata. 



36. 

 Ostrea, 2 sp. 

 Melania fasciata. 

 Cyrena obovata. 

 C. cuneiformis. 

 Potamides acutus. 

 P. cinctus. 

 Melanopsis. 

 Serpula. 



* In the absence of data in our island to prove the age of this disturbance, we 

 may refer to the opinion of Elie de Beaumont, who considers it to belong to the 

 period of the elevation of the western chain of the Alps, with which it is parallel. 

 This system of elevation, according to the same authority, took place at the end 

 of the tertiary period, and immediately preceding the period of the diluvium and 

 drift. (Recherches sur quelques-unes des Revolutions de la Surface du Globe, p. 65.) 



