546 Fisher — Denudations of Norfolk. 



But the well at Yarmouth proves that the erosion which existed at that place 

 during the Eocene period was again repeated in later times, upwards of I20 feet 

 beneath the sea-level bemg now occupied by very late deposits. 



We have no evidence that the sea of the Crag period occupied any part of the 

 present estuary of the Wash. It is probable on the other hand that the Chalk may 

 have extended considerably to the westward of its present escarpment, and two 

 reasons seem to favour this idea. In the first place an immense quantity of the 

 debris of both the upper and lower beds of the Chalk is met with in the glacial 

 deposits, showing how much has been destroyed ; and in the second place the 

 general depression of the surface, which would have been requisite for the submer- 

 gence of the Crag beds to the probable depth at which they were formed of 120 

 feet or so beneath the sea, would allow nearly 2CX) feet on a rough estimate to be 

 added to the Chalk, without its forming higher land during the Crag period than it 

 does at present. This would manifestly bring the escarpment considerably to the 

 west of its present position, without its forming more elevated land than it does 

 now. 



Immediately upon the Chalk at Thorpe, and more or less so at all the localities 

 where the Crag rests upon it, there lies a thick bed of flints. These flints are not 

 rolled, but appear to be the accumulated result of the removal of the Chalk inter- 

 vening between several successive layers. In a large chalk pit at Coltishall I 

 observed a band of flint i7i situ in the Chalk, cropping out into, and forming an 

 integral portion of this remarkable deposit. It is among these flints that the 

 numerous bones, teeth, and tusks of Mastodon and Elephas meridionalis and 

 other mammalia occur. I believe they are more numerous at Horstead than else- 

 where. The interstices of this bed are filled with sand and shells ; and many 

 of them, in their natural positions with valves united, are found among the flints, 

 especially at Thorpe. My belief is that the Chalk to which these flints are due, 

 was removed by the erosion of currents, which were not strong enough to move 

 the flints ; but sweeping in among their interstices, and charged with sand, 

 gradually eroded the softer Chalk. Nevertheless, if that were so, there is still a 

 difficulty in accounting for the bones being buried among the flints. The other 

 alternative that the Chalk formed a land surface, on which the bones were 

 left, the flints being accummulated by subaerial solution of the Chalk, presents still 

 greater difficulties. For it is hardly possible to conceive submergence to have 

 taken place over so wide an area, without the formation of cliffs, and the conse- 

 quent entire destruction of the old surface. And even if that had been spared, the 

 introduction of the united valves of mollusks throughout the entire layer offers no 

 less difficulty than that of the bones on the other supposition. Moreover, such a 

 subaerial condition would have been accompanied by pipes, which I do not believe 

 occur of that particular date. And also the bones ought to lie only on the surface 

 of the stratum, which I believe is not the case. 



We have now arrived at a period in the Geological past of Norfolk, which 

 presents among many intricate problems one of the most intricate, namely, the 

 succession of events subsequent to the period of the Crag. Closely connected with 

 this question is the position of the Chillesford clay. I trust, therefore, that I shall 

 be excused if I say a few words upon that point. I formerly held and published 

 an opinion that the Chillesford clay is older than the Norwich Crag. But subse- 

 quent observation led me to recant that opinion, ^ and agree with my friends, the 

 Messrs. Searles Wood, that the Norwich crag is the lower stratum of the two, and 

 that the shell bed at the base of the Chillesford clay, as seen at Chillesford, Sud- 

 bourne Church Walks, Easton Bavent Cliff, Aldeby, and other places, is no other 

 than the Upper Crag, distinguished and described by Mr. Taylor as occurring at 

 Bramerton, and other localities in this neighbourhood. ^ The Chillesford deposit 

 itself is very changeable, often passing suddenly into sands without a trace of the 

 usually fine micaceous grey clay. This variable character may be well seen in a 

 section in a rickyard between Surlingham Ferry and Bramerton pit. But although 

 I adopt the view of the Messrs. Wood regarding the sequence downwards from the 

 Chillesford clay to the Crag (whether red or fluviomarine), I do not think that its 

 position relative to the Forest bed, and the Glacial series above, is yet satisfactorily 

 made out. Mr. Searles Wood, jun., tells us shortly, in the explanation of his 



' Jour. Geol. Society, vol. xxiii , p. 175. 



« Wood on the Red Crag. Quart. Jour. Geol. Soc., vol. xxii, p. 547. 



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