Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/229

PROCEEDINGS

 

OF

 

THE GEOLOGICAL SOCIETY.

 

---

POSTPONED PAPERS.

---

 

1. On the Structure of the Crag-beds of Suffolk and Norfolk, with some Observations on their Organic Remains. By Joseph Prestwich, Esq., F.R.S., F.G.S. Part I.—The Coralline Crag of Suffolk.

(Read March 11, 1868.)

[Plate VI.]

Previously 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 established. In that year Mr. Charlesworth^[1], in a paper communicated to this Society, showed that in Suffolk the Crag could be divided into an Upper (the Red) and a Lower (the Coralline) Crag; and he afterwards 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 Red and Coralline Crags. On the other hand, the difference between the Red and Mammaliferous Crag was founded entirely on palæontological 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. Lyell^[2] and, more lately, of Mr. Searles Wood, Jun.^[3], and several other geologists; but the Red 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 all of which latter I took notes during the construction of the Great Eastern Railway. 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 Mammaliferous Crag of Norfolk to the Red 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

1. Proc. Geol. Soc. vol. ii. p. 195.
2. Proc. Geol. Soc. vol. iii. pp. 126 & 437, and Mag. Nat. Hist. 1839, p. 313.
3. Ann. & Mag. Nat. Hist. for March 1864.