﻿Vol. 64.] STTBDIVISIONS OF THE CHALK OF TEIMINGHAM. 



40 : 



Only SO much of them has been mapped as has been actually 

 accessible, and this gives a maximum length of unbroken Chalk of 

 about 700 yards. More Chalk has always been visible seawards ; 

 and at lowest tides rough ridges, apparently continuous with the 

 block, are seen extending out at sea from its southern end for at 

 least another 250 yards. 



I have now dealt with the general structure of this block, but 

 there are several small areas requiring special notice. The first and 

 most important is the neck of Chalk leading to the much discussed 

 North Bluff. This neck puzzled me extremely for a long time, for 

 in small exposures there was practically nothing to suggest the 

 existence of the fault (v) shown running through the neck. There 

 is no seam of grit, clay, or crushed chalk marking the fault, and the 

 strike and the character of the Chalk are practically the same on 

 both sides. It was only an exceptionally clean and extensive ex- 

 posure which gave me the clue — by showing that the dips on the two 

 sides of the fault were opposed, though the strikes were so nearly 

 identical. The Bluff in recent years has been wholly formed of the 

 beds (k') on the south side of this fault, and fortunately some of 

 the beds which appeared in the Bluff can still be traced continuously 

 down the neck and round to the south-east into a large mass of Chalk 

 with a gentle northerly dip, which is obviously natural and not the 

 result of inversion. Now, the section presented by the North Bluff 



was (roughly speak- 

 Pig. 2. — Section presented hy the 



North Bluff in 190u 



ing) a section of the 

 upper part of a fold 

 lying on its side, as 

 shown in the accom- 

 panying figure ; and 

 Mr. Clement Eeid 

 assumed, and in 

 1906 I adopted the 

 assumption, that the 

 upper part of this 



\ ^v^ --^^ fold had had its 



^-^^ ""--.^ original dip reversed, 



while the lower part 

 had been inverted. It is, however, now clear that the lower part 

 of the fold still retains its original dip, and that it is the upper part 

 which has been inverted. Therefore the inverting force must have 

 acted from the south, and not from the north as previously supposed. 

 Thus we get this force entirely distinct from that which caused the 

 main anticlinal folds and must have acted from the north, as these 

 folds are always steepest on the south side. It is possible that 

 the very curious S-shaped bend in the edge of the Grey Chalk {p) 

 to the east and the bending of a few of the nearest beds of flint 

 are another effect of the inverting force. 



It may be advisable here to recall that the inverting force was of 

 Cretaceous age, as the Bluff showed that on a denuded surface of 

 the inverted beds there had been deposited Grey Chalk with a pure 



