PROCEEDINGS 



THE GEOLOGICAL SOCIETY. 



POSTPONED PAPERS. 



1. On the Strtjcttjre of the Crag-beds of Stjefolk and Norfolk, 

 with some Observations on their Organic IIemaijSts. By Joseph 

 Pkestwich, Esq., F.E.S., F.G.S, Part I. — The Coralline Crag 

 OF Sitffole:. 



(Read March 11, 1868.) 



[Plate VI.] 



Previouslt to 1835, although some observers, and Mr. Searles Wood 

 in particular, had noted the peculiarity of the fossils from the beds 

 now known as the " Coralline Crag," no stratigraphical divisions of 

 the Crag-beds of Norfolk, Suffolk, and Essex had been estabhshed. 

 In that year Mr. Charlesworth *, in a paper communicated to this 

 Society, showed that in Suffolk the Crag could be divided into an 

 Upper (the Eed) and a Lower (the Coralline) Crag ; and he after- 

 Avards formed a third and higher zone of the Mammaliferous Crag of 

 Norfolk. With respect to the two lower divisions several cases of 

 direct superposition were given, which established beyond doubt 

 the relative position of the E,ed and Coralline Crags. On the other 

 hand, the difference between the Eed and Mammaliferous Crag was 

 founded entirely on palaeontological evidence, as no instance of 

 superposition was known; and although more than thirty years 

 have now elapsed, the question in that respect remains in the same 

 condition. The observations of Mr. Charlesworth were followed by 

 those of Sir C. Lyellf and, more lately, of Mr. Searles Wood, Jun. J, 

 and several other geologists ; but the Eed Crag has received more 

 attention than the Coralline Crag. 



The object of this communication is to describe the physical 

 structure of the several Crags, and to determine, if possible, the exact 

 relation the Suffolk Crags bear to the Crag of Norfolk. With this 

 object in view, I have examined on several occasions the coast- 

 section from Aldborough to Weybourne, and the various inland 

 pit- and railway-cuttings, of aU of which latter I took notes during 

 the construction of the Great Eastern Eailway. The greater part 

 of my observations date, in fact, so far back as from 1845 to 1855, 

 which will explain the variation in some of the coast sections, and 

 account for the disappearance of some inland sections. The difficulty 

 of obtaining direct evidence showing the relation of the Mammah- 

 ferous Crag of Norfolk to the Eed Crag of Suffolk, and of correlating 

 the beds beneath the Boulder-clay with the other beds of the same 

 age through the south of England, led me to delay bringing this 



* Proc. G-eol. Soc. vol. ii. p. 19o. 



t Proc. Geol. Soc. vol. iii. pp. 126 & 437, and Mag. Nat. Hist. 1839, p. 313. 



X Ann. & Mag. Nat. Hist, for March 1864. 



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