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



II. — The Petrology of the Suffolk Box-stones (Crag). 

 By P. G. H. Boswell, D.I.C., B.Sc. 



(PLATE X.) 



ALTHOUGH much has been written upon the palaeontology of the 

 Suffolk box-stones, no description appears hitherto to have been 

 published of the petrology of these boulders. This is the more 

 curious on account of the light it might throw upon the disputed 

 question of their source, no similar sandstone having yet been 

 recognized with certainty in situ. 1 The most recent account of the 

 molluscan fauna is by my friend Mr. Alfred Bell. In a preliminary 

 paper 2 he has given a list of sixty-three species (excluding cetacean 

 bones, teeth, crustaceans, etc.), about twelve new species and varieties 

 being described. Mr. Bell has now kindly let me see in advance the 

 MS. of a revised list of Mollusca (seventy-six species), much new 

 box-stone material having been obtained in the last few years. As 

 a result of recent work, he considers the affinities of the fauna to be 

 rather with the Rupelian (Continental Oligocene) than with the 

 Bolderian or Diestian, as he formerly thought. Mr. Clement Reid, 

 in The Pliocene Deposits of Britain (Mem. Geol. Survey, 1890), 

 considered the box-stones to be of about the same age as the Diestian 

 Beds, but Mr. F. W. Harmer has, in later publications, been inclined 

 to consider them to be rather older and of very early Pliocene age. 



The box-stones are masses of a fairly hard brown sandstone, about 

 the size of the fist, or a little larger. These boulders are often well 

 rolled, but sometimes occur as flattened tabular lumps, and have 

 received their name from workmen owing to the fact that about 

 10 per cent of them, on being broken open, are found to have enclosed 

 fossil remains. Fragments of wood and bone, as well as teeth and 

 casts of Mollusca, occur in this way, and, while it appears to be 

 probable that some of the box-stones may have been formed by 

 concretionary segregation of iron-oxides and calcium phosphate and 

 carbonate around organic nuclei, others appear merely to be the 

 broken-up fragments of a ferruginous sandstone. The latter may 

 have been derived from iron-impregnated bands in the original sandy 

 beds like those met with in the Lower Greensand or Red Crag. 



Large muscovite flakes glisten here and there, but macroscopically 

 the sandstone cannot be said to be highly micaceous, nor very compact. 

 Casts and impressions of shells are sometimes seen, and more rarely 

 a fragment of a calcite shell, e.g. Pecten. As in the Coralline and 

 Red Crags when they are decalcified, the aragonite shells have usually 

 disappeared as a result of solution. 



Appearance in thin section. — A number of box-stones from Foxhall, 

 Sutton, "Waldringfield, the mouth of the Deben, and also from the 

 collection of the Imperial College of Science and Technology have 

 been sliced and examined. The numbers in square brackets, attached 



1 Lyell drew attention to the similarity between the box-stones and some 

 Antwerp beds near Berchem (Q.J.G.S., vol. xxvi, p. 513, 1870). Other authors 

 have noted their similarity to the Diestian. 



2 " On the Zones of the East Anglian Crags " : Journ. Ipswich and District 

 Field Club, vol. iii, p. 5, 1911. 



