4 GEOLOGY OF THE ISLE OF WIGHT. 



The correlation of these two groups of the Isle of Wight with 

 the Wealden strata of the mainland has caused some diversity of 

 opinion. Dr. Fitton and the older authors spoke of the upper 

 group only as Wealden and of the lower as Hastings Sand. By 

 the Geological Survey they were both included under the name 

 Wealden, but in 1856 Mr. Godwin Austin* stated that the Weald 

 Clay might he seen " to alternate with, and therefore to be 

 synchronous with, the marine Neocomian." Professor Judd f 

 also in 1871 stated that he looked upon "the great mass of 

 variegated strata containing only freshwater and terrestrial fossils 

 . . . . as the Wealden proper," and that the upper group 

 or Punfield Beds, as he called them, " may be regarded indif- 

 ferently either as the highest member of the Wealden in our 

 classification of terrestrial strata, or as a portion of the Neoco- 

 mian in our grouping of the marine series." This view of their 

 relations was suggested by the intermingling of brackish water 

 or marine forms such as Cardita, dwarfed oysters, and the estuarine 

 Vicarya with purely freshwater forms such as Paludina and Unio. 

 But unfortunately, the true base of the Lower Greensand not 

 having been then discovered at Punfield, a large part of this forma- 

 tion, with its highly characteristic fauna, was included in the 

 " Punfield Beds " of Professor Judd, with the result that the 

 fauna of these Punfield Beds was made up partly from the Lower 

 Greensand and jiartly from the Wealden. 



This fact was first ascertained by Mr. MeyerJ in the years 

 1871-72. He observed that the Atherfield Clay with some of 

 its characteristic fossils occurred beneath the fossiliferous zone 

 from which many of the marine Punfield fossils had been obtained, 

 and that the characteristic cypridiferous shales Avith limestone 

 occurred beneath and nowhere above this marine band. His con- 

 clusions were strengthened by observations made by the Geologists' 

 Association§ in 1882, and have been fully confirmed by the exami- 

 nation that was undertaken for the purpose of the present Memoir. 

 The results and measurements obtained during this examination 

 will be incorporated in the following pages, but it may be stated 

 here that at Punfield, as in the Isle of Wight, the palreonto- 

 logical break between the Wealden and Lower Greensand is 

 complete, and is accompanied by evidence of considerable erosion 

 of the former. 



The name of Punfield Beds, therefore, having been applied to 

 strata belonging to two distinct groups, will not be used here. But 

 at the same time it will be convenient to distinguish the beds for 

 which the name was intended from the vai'iegated Wealden type 

 which has been mentioned above. The name Upper Wealden 

 is scarcely suitable, for, though generally found at the top 

 of the Wealden formation, they appear also to be interstra- 



* Quart. Journ. Geol. Soc, vol. xii. p. 66. 

 f Ibid., vol. xxvii. p. 207. 

 j Ibid., vol. xxviii. p. 243, and vol. xxix. p. 70. 

 § Proc. Geol. Assoc, vol. vii. p. 388. 



