LATER TERTIARY GEOLOGY OF E^ST AKGLIA. 



75 



times twenty feet thick, did they present any traces of the Chilles- 

 ford Clay over them." 



In some of the excavations for the extraction of phosphatic nodules 

 (coprolites) these sands seem to pass down into the Red Crag by thin 

 seams of comminuted shell ; but in others they present an appearance 

 which, in the case of other formations, would be regarded as clearly 

 indicative of unconformity ; for their stratification is wholly indepen- 

 dent of the shelly crag beneath them, while the sands themselves 

 often overlap and envelop the latter. In some instances (but these 

 are the exception) they present the same oblique stratification which 

 is possessed by the greater part of the shelly beds of the Red Crag. 

 In others, such as that shown in section III. (page 81), detached and 

 apparently disconnected portions of the shelly crag are imbedded in 

 these sands, just as though they were transported masses imbedded 

 while the sands were being accumulated. 



Fig. 1. — Section I., in a Coprolite-pit one mile and a half north- 

 west of Waldr'uiQ 'field church. (Scale 10 feet to the inch.) 



a. Eed Crag, unaltered and full of shells. 



b. Red stratified sands, being a altered and restratified. 

 #. Seam of flint-pebbles. 



c. Pipe filled with sand traversing both the altered and unaltered Crag. 



The above section (I.) represents the usual way in which these 

 sands overlie the shelly crag, so far as their stratification is con- 

 cerned ; but in that section another stratification occurs in a band of 

 pebbles which, while conformable to that of the shelly crag where 

 it is included in that material, cuts obliquely across the horizontal 

 stratification of the unfossiliferous sands. 



It has long been known, and it is mentioned by Mr. Prestwich in 

 his paper on the Eed Crag *, that these sands occasionally include 

 ironstone casts of Crag shells. These we have found loose in them. 

 Mr. Whi taker also, about two years ago, discovered in a pit three 

 quarters of a mile N.E. of Kesgrave church, some bands of ironstone 

 in these unfossiliferous sands which contained numerous and well- 

 preserved impressions of Red -Crag shells, to which he called the 

 attention of one of us, expressing his opinion that the sands in which 

 these bands of ironstone occur had once been fossiliferous like the 

 shelly crag, but had been deprived of their shells by the action of 

 acidulated waters. 



The difficulties in the way of that view appeared to us to be, that 

 the line dividing the shelly crag from these sands was abrupt, no 



* Quart. Journ. Geol. Soc. vol. xxvii. p. 330. 



