﻿358 A. J. Julies Browne — On the Upper Greensand, etc. 



Cliloritic Marl, it is evident that this identification is not correct, and 

 that these beds must be restored to the Upper Greensand.^ 



The mistake was probably caused by the existence of remanieb 

 fossils from the Warminster beds in the Chloritic Marl of the Isle 

 of Wight, imparting to its fauna the semblance of that below ; this 

 appears to be also the case with its probable equivalent in the Devon- 

 shire section, namely, that numbered 13 by Mr. Meyer, which he 

 describes as resting upon an uneven surface of the bed below, and 

 as containing numerous phosphate nodules and casts of shells, some 

 of which he regards as having probably been derived from the erosion 

 of the beds below. He rightly considers this bed as forming the 

 base of the Chalk Marl, and remarks upon the importance of the 

 line formed by its marked separation from the Warminster beds. 



The paper indeed is a valuable one, for though mistaken in 'one 

 particular, he correctly states the infra-position of the Blackdown to 

 the Warminster beds, and of the latter to what is really the Chloritic 

 Marl ; the true relations of these beds had not before been ascer- 

 tained, and tlie lists of fossils aifford the means of determining and 

 recognizing the beds over a larger area. 



1 have previously drawn attention to the similarity between the 

 conditions presented by the base of the Chalk Marl in Devonshire 

 and those observable in the Cambridge Greensand ;- there can, I 

 think, be little doubt that the two beds occupy exactly the same 

 horizon, and that the fossil contents of both are to .a greater or 

 less extent remanies. There is, however, this great difference be- 

 tween the two sets of derived fossils, viz. that the one of them 

 was derived from the fauna of the Warminster beds, and the other 

 from that of the Upper Gault ; the reasons of this difference I have 

 also fully explained.* The Cambridge bed has been described as 

 Chloritic Marl by the Eev. T. G. Bonney in a paper read before 

 the Geologists' Association in 1872,* and more recently in 'his Cam- 

 bridgesMre Geology, but without distinctly comparing it to the 

 Chloritic Marl of the Isle of Wight; in the former paper, indeed, 

 he was inclined to regard it as to some extent the equivalent of 

 the Upper Greensand, but adds at p. 19, "It must, however, be 

 remembered that, probably, our Cambridge bed is rather homo- 

 taxial than absolutely contemporaneous -with some at least of the 

 more western developments of the South of England Upper Green- 

 sands." I think, however, I am not misrepresenting Mr. Bonney's 

 present views in saying that he concurs with me in considering the 

 Nodule Bed as forming the actual base of the Chalk Marl, and, 

 therefore, as the exact equivalent of the Chloritic Marl according 

 to its more recent definition. 



^ See Barrois, Sur I'age des couches de Blackdown, Ann. Soc. Geol. du Nord, 

 torn. iii. p. 7. 



2 Quart. Journ. Geol. Soc, vol. xxxi. p. 272. 



" The fact of the entire absence of the characteristic fossils of the Warminster beds 

 in the CHmbridge Greensand is sufficient proof that these beds were never deposited 

 in that area, loc. oif., pp. 272, 273. 



■* Proc. Geol. Assoc, vol. iii. 



