20 GEOLOGY OF TflE ISLE OF WIGHT. 



Neocomlan strata of the north to have been conteraporaneous with a 

 part of the Wealden Beds of the south, the one having been depo- 

 sited in an area open to the sea, the other in a basin that remained 

 hmd-locked until a later part of the Neocomian period. The 

 history of the great freshwater deposits, of which in the Isle of 

 Wight we have only the upper part, is beyond the scope of this 

 Memoir, and will be treated more fully in the General Memoir on 

 the Cretaceous Rocks. 



The Lower Greensand of the Isle of Wight is divisible into four 

 groups, capable of being traced throughout. But at Atherfiekl, 

 where they are most fully developed, Fitton made six principal 

 divisions and sixteen minor groups. In the following table 

 Fitton's groups are compared with those adopted in this Memoir, 

 and with those in use in the Weald of Kent and Sussex. 



The only point in which a material difference between the two 

 classifications exists, occurs in Fitton's Division F. A portion of 

 this has now been separated under the name of Oarstone, while 

 the lower part of it is grou})ed with E., to which it is lithologically 

 allied, under the name of Sand-rock Series. The lowest member 

 of Fitton's Group XV., a thick bed of clay, is taken as the top of 

 the Ferruginous Sands, in consequence of the similarity of the 

 deposit to a band of shale wliich forms the top of the Sandgate 

 Beds at Pulborough.* The Perna Bed, though palieontologically 

 of the greatest interest, is too thin to be separately map])ed. The 

 names used have been adopted as far as possible from those who 

 first investigated the beds. 



The term Shanklin Sands was pi'oposed by Fittonf for the 

 whole of the Lower Greensand to avoid confusion between this 

 formation and the Upper Greensand, and was used in this sense 

 by Martin. But subsequently the name became restricted to the 

 up{)er beds of the Lower Greensand, and having been made to 

 include a varying proportion of the deposit by various authors, 

 and its original meaning, as intended by its author, having been 

 lost, it has been thought better to abandon it. The name Vectine, 

 also proposed by Fitton, and subsequently modified into Vectian 

 by Mr. Jvd?es-Browne,t has never come into general use. {See 

 also p. 2 on the use of Vectian for the Fluvio-Marine Series.) 



Geological Geological 



Fitton, 1845. Survey, 188/. Survey. 



(Atherfield.) (Isle of Wight.) (S.E.England.) 



XVI. Various sands and clays 



F 

 XV. Upper clays and sandrock 



EJ 



>--< 



Carstone. 



Sand-rock 

 Series. _^ 



Folkestone 

 ■ Beds. 



* Geology of the Weald (Geological Survey Memoir), p. 13G. 

 t Ann. Phil., 2, viii. p. 461. 

 X Geol. Moif. for 1885, p. 208. 



