in East Anglia. 415 



of the escarpment which in pre-Thanetian times faced south-east- 

 ward and stretclied away many miles to the west and south. Between 

 Yarmouth and Aldeburgh there appears to be evidence of a drop to 

 the eastwai'd, which is most clearly shown between Beccles and 

 Lowestoft, but we are hardly in a position to place much confidence 

 in any explanation put forward concerning this interesting and 

 somewhat unexpected feature. The writer thinks it not unlikely 

 that, along a N.W.-S.E. line traversing the central part of the 

 Norfolk area, there was, during the deposition of the Chalk, a definite 

 movement of depression, whereby a greater thickness of sediment 

 was deposited vertically above this line than was laid down farther 

 east. If this was the case, the severity of the denudation suffered 

 by the Chalk in, the central portion of the area is still further 

 emphasized. 



The evidence of an advancement in the stage to which the 

 denudation of the Chalk proceeded during post-Eocene and pre- 

 Pliocene (i.e. Miocene) times, is verj- striking. The earth-move- 

 ments which were ia operation in Miocene times, governing the 

 general character of the denudation, were, in this area, different in 

 their direction from those whose activity resulted in the production 

 of the old E.N.E.-W.S.W. pre-Eocene escarpment. A movement of 

 uplift along an axis traversing the central part of Norfolk, and 

 disposed in a general N.W.-S.E. direction, appears to have taken 

 place, and denudation proceeded in such a way as to produce an 

 escarpment facing west and making a pronounced feature in the 

 landscape. A strong valley was eroded in the Chalk in pre-Pliocene 

 times, but we are not in a position to state the age of the abrading 

 stream with any precision. It may have been initiated in pre-Eocene 

 times and perhaps entered the area at a spot somewhere between 

 Happisburgh and Yarmouth. On the supervention of the new 

 movement of uplift fresh river-systems were initiated, which are 

 those of the present day, and one stream, the Waveney, throughout 

 a part of its course, actually occupies the site of the old valley, thus 

 providing us with an interesting illustration of reversal of drainage. 

 The severity of this post-Eocene and pre-Pliocene denudation of the 

 Chalk is well brought out by the map. Where the isopachytes 

 emerge from beneath the Eocene cover they change direction most 

 abruptly and exhibit a very pronounced tendency towards parallelism 

 in a general N". W,-S.E. direction. A considerable thickness of chalk 

 must have been removed from the exposed portions of the formation 

 during this time, particularly in the northern part of the area. 

 With the advent of Crag times a further portion of the chalk surface 

 was covered, and that part which is yet concealed beneath the Crag 

 has, of course, escaped all post-Pliocene denudation. This post- 

 Pliocene denudation has effected the removal of much of the Crag 

 cover and carried the attrition of the chalk beneath it to a still more 

 advanced stage. 



In addition to bringing out the interesting points already 

 considered, our map is of service in enabling us to insert the 

 boundaries of the outcrops of the successive zones of the Chalk, 

 for unless the zones vary in thickness throughout the area, the 



