﻿352 A. J. Jukes Browne — On the Upper Greensand, etc. 



the Gault and Chalk-marl, and to review some of the conclusions 

 arrived at by different writers on the subject, in order that the way 

 may be paved towards the establishment of a better nomenclature, 

 and a more natural classification in this part of the geological series. 



The Upper Greensand. 



The early history of this formation is chiefly connected with that 

 of the Wealden area, where the Firestones and Greensands below 

 the Chalk had attracted attention in the beginning of the present 

 century ; it was to these I believe that the term " Greensand " was 

 first applied : thus in William Smith's Memoir (1815), the suc- 

 cession of the strata is correctly given as follows : 

 Chalk (Upper and Lower) . 

 Greensand parallel to the Chalk. 

 Blue marl (viz. Gault). 

 Kentish Rag, etc. 



This last, however, and some other beds between the Gault and 

 Weald Clays, being likewise of a green colour, came also to be 

 spoken of as " the Greensand." Thus Conybeare and Phillips, in 

 1822, showed the Firestone-beds of Merstham to be distinct from 

 the Greensand, and separated therefrom by a blue marl which they 

 doubtfully refer to the Cambridge Gault. They also distinguish the 

 [Lower] Greensand from the Hastings beds of the Weald, then 

 called "Iron sand"; but they do not make the same distinction in 

 the Isle of Wight, where their Greensand is the Upper Greensand. 



It was left for Fitton, in 1824,^ to finally clear up doubts and 

 difficulties which attended the correlation of the Greensands and the 

 Iron sands, and by him the whole series was correctly described 

 both in the Wealden area and in the Isle of Wight. 



It being thus proved that there were two horizons where beds of 

 Greensand occurred, viz. above and below the Gault or "Blue 

 nrarle," it was natural that these should come to be called the 

 Upper and Lower Greensand, Sir E. I. Murchison seems, however, 

 to have been the first who actually made use of the name in any 

 published paper : this being in his Memoir on West Sussex, read 

 before the Geological Society in 1825. 



Mr. Martin adopted the name for the beds in the northern part of 

 the Weald, and Dr. Fitton in 1836 for those in the Isle of Wight 

 and the south-east of England. The name was thus accepted as 

 designating all the sandy beds between the Gault and Chalk-marl, 

 and was a division founded purely on lithological characters, and 

 without any reference to the fossils which its several component 

 strata contained. 



The first attempt to estimate accurately the thickness of the Gault 

 and Greensands is recorded in the Quart. Journal for 1845 by Mr. 

 J. W. Simms,* the following section being measured between Ather- 

 field Point and the cliff south of St. Catherine's Down : — 



1 Ann. Philos. ser. ii, vol. viii. pp. 365 and 458. 



2 Quart. Journ. Geol. Soc. vol. i. p. 77. 



