26 A. J. Jahes-Broicnc — Bor'uuj through Chalh near Dieppe. 



According to the diagrammatic section of the coast-line given bj' 

 Hebert in 1872, Pays stands on the chalk of the Holnster j^lan^is 

 zone/ which corresponds to the lowest part of the flinty chalk 

 east of Dover. Thus the chalk traversed by the boring is the 

 equivalent of the whole of our Lower and Middle Chalk. In 1875 

 Hebert estimated the thickness of the jj/ajiits zone near Dieppe 

 at 11 metres (36 feet) and that of his zone of Inoceraimts labiatus 

 (our zones of Ehynchonella Cuvieri and Terehratnlina gracilis) at 

 70 metres (230 feet). The three zones taken together, therefore, are 

 estimated at 266 feet, and if Ave deduct this from the oll^ feet of 

 chalk travei'sed hy the boring, there remains 24o^ feet as the 

 thickness of the Lower Chalk. This is rather a greater thickness 

 than might have been expected for the Lower stage, and it is 

 probable that the Middle Chalk or Turoniau is rather thicker than 

 Hebert supposed. As a matter of fact he measured 65 metres of it 

 in the cliff itself, and its base is nowhere exposed ; hence it is not at 

 all unlikely that its full thickness is nearly 75 metres (or 247| feet), 

 and in this case the thickness assignable to the Lower Chalk will be 

 228 feet, which is a more probable amount. 



The two metres of green&and and sandy clay at the base of the 

 Chalk probably corresponds with what we know as the Chloritic 

 Marl or zone of Stauronema Carteri. This has a thickness of about 

 15 feet at Folkestone, but not more than 4 feet near Eastbourne. 



As nothing of the nature of sandstone or ' gaize ' is recorded in 

 the boring, we may assume that nothing of an ' Upper Greensand ' 

 character is present below Dieppe, and that the zone o? Ammonites 

 rostratus is represented by clay and marl as it is at Wissant and 

 Folkestone. This is interesting as showing that what may be called 

 the Folkestone facies of Gault extends as far as Dieppe, which is 

 about 78 miles south of Folkestone and rather less from Wissant. 



November 10. — Since the above was written I have received, 

 through the kindness of Monsieur G. DoUfus, a more complete 

 account of this boring. The followin<r is a translation : — 



Ground excavated ... 

 /'AVhiteraarl 



Soft white marl ... 



Grey marl ... 



"White marl 



Grey marl -with Hints 



Hard white marl ... 

 ^ ") Hard marl (^-ith Inuecrainits Mnatiis) 

 "^ Grey clialk 



Grey chalk with flints 

 Grey chalk 

 Greeuisli saudy clay . 

 Green sandy clav ... 

 Black clay" " ... 

 Clayey green sand 

 Grey sand ... 

 Black sandy clav . . . 



Bull. Soc. Geol. France, ser. ii, vol. xxix, p. 586. 



