752 THE PLIOCENE DEPOSITS OP HOLLAND. [Nov. 1 896. 



and the Crag from Norwich to Dramerton, produced eastward in the 

 direction of Yarmouth, very nearly intersects the base-line of the 

 Pliocene beds under that town. 



When we pass to the other side of the North Sea and of the 

 English Channel, we find evidence of similar earth-movements, but 

 on a larger scale. While an elevation of the southern portion of 

 the Pliocene area, corresponding to that at Lenham, has taken place 

 in Belgium and in the North-east of Prance, the northerly 

 depression has in Holland reached a total depth, possibly, of more 

 than 1500 feet. (See section, fig. 3, p. 753.) 



In a map published in 188 7, 1 from which the distribution of the Plio- 

 cene beds of Belgium in the accompanying sketch-map (PL XXXIY.) 

 has been taken, the eminent Belgian geologist M. E. Van den Broeck 

 has shown a chain of outliers of Diestien deposits, generally capping 

 isolated hills, extending from Cape Blanc Nez, near Calais, where 

 they attain an elevation of about 500 feet, through Cassel, Tournai, 

 Grammont, and Brussels to Louvain, at which pLace, however, they 

 are not more than 195 feet above the sea. From Louvain, Diestien 

 strata extend in a continuous sheet, covering a considerable extent 

 of country to the N.E. Mr. Clement Reid connects these Belgian and 

 Prench beds with those at Lenham, by a belt of outliers of similar 

 ferruginous sandstone, occurring on the English side of the Channel 

 near the Chalk escarpment between Polkestone and the river Stour. 2 

 It is considered by M. Van den Broeck that these deposits indicate 

 generally the southern boundary of the Diestien sea. In passing I 

 may say that M. G. P. Dollfus, the President of the Geological 

 Society of Prance, insists that this sea was closed to the south, 3 but 

 the marked resemblance between the molluscan fauna of the Coral- 

 line Crag (the English equivalent of the upper part of the Diestien 

 formation) 4 and that of the Lusitanian and Mediterranean areas at 

 the present day makes me tenacious of the hypothesis that there 

 was at the period in question direct communication between the 

 Anglo-Dutch basin and the Atlantic. 5 If the line from Louvain to 

 Lenham, indicated by this chain of deposits, formed the continuous 

 margin of the Diestien sea, it may still have been connected with 

 the south-west by means of a strait over some part of the southern 

 counties of England. 6 Whether or not the sea of the Coralline Crag 



1 Bull. Soc. Beige Geol. vol. i. pi. ii. 



2 ' The Pliocene Deposits of Britain,' Mem. Geol. Surv. 1 890, p. 49. 



3 Eep. Brit. Assoc. Ipswich (1895) p. 691. 



4 While agreeing with Mr. Reid that the Lenham Beds are equivalent to the 

 ferruginous Diestien Sands of Belgium, the study of the fauna of Lenham leads 

 me to think that the deposit may be slightly older than the Coralline Crag. The 

 latter is evidently of similar age to the Belgian ' zone a Isocardia Cor,' which 

 M. Yan den Broeck considers to be the upper part, while the sands of Oassel,etc, 

 are, in his opinion, the lower part of the Diestien formation. Of the species of 

 mollusca known from the Isocardia-beds 87 per cent- occur in the Coralline Crag. 



5 See Geol. Mag. 1896.. p. 27. 



6 It may be accidental, but perhaps it is worthy of not'ce, that the triangular 

 shape of the Red Crag area between Saxmundham and Sudbury, with its apex 

 pointing to the S.W. (see map, PI. XXXIV.), seems almost to suggest that a de- 

 pression, from which the sea was gradually retreating as the southerly elevation 

 went on, may have formerly existed in that direction. 



