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



eluded in his little iDook on the Strata of the Isle of Wight previously 

 cited. In these publications he does not appear to propose the 

 application of the term to this bed for the first time, although it is 

 probable that its position was now first clearly defined ; he thus 

 speaks of it at p. 21 : ^ 



" The Chloritic Marl or principal phosphate of lime bed comes 

 next in succession and divides the Chalk Marl from the Upper 

 Greensand. It is a grey marl full of gi'een grains of a silicate of 

 iron and sand, very fossiliferous. The upper part in places exhibits 

 a conglomerate of pebbles and small boulders, and in it the fossils 

 are chiefly broken as if rolled on a beach. The lower beds contain 

 the fossils whole and appear to have been formed in still water. 

 Ammonites varians and splendens, and Scaphites striatus are the 

 most characteristic fossils, but it also contains abundantly nodules of 

 a coprolitic form, composed of from 15 to 28 per cent, of phosphate 

 of lime." 



The bed is stated to vary in thickness from one to three feet, and 

 to occur all round Shanklin and St. Boniface Downs directly under 

 the Chalk Marl ; a list of other places where the stratum is observ- 

 able is also given. 



Nothing is added to this description in the Geological Survey 

 Memoir of 1862, except a fuller and more accurate list of fossils. 

 Mr. Best informs me that the term Chloritic Marl appears to have 

 been first adopted by the Survej^ during the year 1856, as it is not 

 mentioned in the Index of Colours for tliat year, but is contained in 

 the first edition of the Catalogue of Eock Specimens published early 

 in 1857. It may, however, have been used in the field before this 

 date, and Prof. Forbes is by tradition accredited with the recognition 

 of the fact that its fauna, though peculiar, links the bed rather with 

 Chalk Marl than with the Greensand below ; probably this was be- 

 tween the years 1844 and 1848, as Prof. Forbes comments upon the 

 list of fossils originally appended to Capt. Ibbetson's paper in that 

 year. Capt. Ibbetson also refers to Messrs. Austen and Nesbit as 

 having mentioned the occurrence of the Chloritic Marl at Guildford 

 and Farnham i-espectively. These gentlemen in 1848 had indicated 

 the exact position occupied by the several phosphatic beds in the 

 Cretaceous series of Hampshire and Surrey,^ and although their 

 papers do not contain any actual mention of the marl, it is suffi- 

 ciently evident that one of the phosphatic beds lies in the uppermost 

 green marl described by Messrs. Paine and Way as varying in thick- 

 ness from one to fifteen feet, and that this is much on the same 

 horizon as the bed identified by Capt. Ibbetson. 



This was also the view taken by Messrs. Bristow and Whitaker 

 in their Memoir on Sheet 12 (1862), where the Chloritic Marl is 

 mentioned as occupying a narrow band at the base of the Chalk 

 Marl, overlying the Malm Eock, and varying in thickness from a 

 few inches to ten or fifteen feet. Sections of this marl are also de- 

 scribed in the later Memoir on the Weald by Mr. Topley, who prefers 



1 Notes, etc., on the Strata of the Isle of Wio-ht, London, 1»49. 



2 Quart. Journ. Geol. Soc. vol. iv. pp. 257 and 262. 



