258 P. G. H. Boswell — Petrology of Suffolk Box-stones. 



staurolite, epidote, muscovite, and kyanite, in great abundance. The 

 richness of the mineral suite and the angularity and large size of 

 the grains, with the absence of grading in size, suggests that the 

 constituents had not travelled far. The extraordinary profusion of 

 andalusite and muscovite is noteworthy, but it is not clear why biotite 

 should be as rare as it is, when epidote and other ferromagnesian 

 minerals are plentiful and fresh. 



The nearest area which would yield the detrital minerals described 

 is undoubtedly the region of the Ardennes, the metamorphic rocks of 

 which have been described in detail in so many publications of the 

 Belgian geological societies. In this connexion the mineral 

 constitution of the Tertiary deposits of Belgium and Northern France 

 is interesting. A discussion of these, and a comparison of the 

 minerals of the Box-stone Bed with those of the East Anglian Eocene, 

 Pliocene, and Glacial beds, must be reserved for a future paper. 



A comparison of the petrology of the box-stones with that of 

 British Pliocene deposits generally is also interesting. In mineral 

 constitution the box-stones have no counterpart, so far as the writer's 

 examination of sediments goes. The Lenham Beds (as well as other 

 high-level ferruginous sandstones of the North Downs), which have 

 been said to possess a molluscan fauna similar to that of the box- 

 stones, show interesting petrological differences. Writing in 1870 on 

 the box-stones, Sir E. Bay Lankester gave it as his opinion that they 

 were very probably of the same age as the Lenham Sandstone, which 

 they resembled most closely in condition and contents. 1 In the light 

 of more recent work the statements require modification. The fauna 

 is an older one, and the beds differ petrologically. The material of 

 the Lenham Beds is finer, less angular, and is well graded. There 

 seems to be no phosphatic cement. The mineral assemblage is less 

 rich than that of the box-stones, and garnets, if present, are rare. 

 (The same remarks apply to the Netley Heath sand.) While the 

 box-stones and Lenham Beds may have been derived from the same 

 area, the former certainly did not arise from the denudation of the 

 latter. Neither is there any striking resemblance between the 

 box-stones and such Diestian material as the writer has been able to 

 obtain from the Continent, although the mineral composition of the 

 latter beds is similar but less rich. More work remains to be done 

 upon the Continental Tertiary deposits. 



The mineral suite of the box-stones conforms generally to that of 

 the East Anglian Pliocene deposits, and is entirely different from the 

 assemblage found in the Eocene beds. It is highly improbable that 

 the same tract of country and area of rocks yielded the material of 

 both series of sediments. The break in mineral composition between 

 the London Clay or the latest Eocene deposits in East Anglia, the 

 Bagshot Beds, and the box-stones, is as striking and significant as 

 the palaeontological gap. 



My thanks are due to my friends Mr. Alfred Bell and Mr. S. A. 

 Notcutt, of Ipswich, for providing me with some of the box-stone 

 material examined. 



1 " Contributions to a knowledge of the Newer Tertiaries of Suffolk and their 

 Fauna" : Q.J.G.S., vol. xxvi, p. 501, 1870. 



