414 Herbert A. Baker — Denudation of the Chalk 



In our study of the map it is helpful to hear one consideration in 

 mind. It is a fair assumption to make that, at the beginning of 

 Eocene times and again at the beginning of Pliocene times, the base 

 of the Chalk in this area did not deviate markedly from horizontality. 

 Consequently the lines upon our map give, for the area where the 

 Chalk is yet covered by Eocene, a generalized representation of the 

 pre-Eocene contours of the Chalk surface, and for the area where 

 the Chalk is covered by Crag, the pre-Pliocene contours. For that 



Map showing Chalk surface contours in the East Anglian area, when the base 

 of the Chalk is corrected to horizontality at sea-level. The lines also 

 serve as the isopachytes of the Chalk. 



area where the Chalk is bare the lines serve to indicate the stage to 

 which its denudation has proceeded at the present day. 



With regard to the pre-Eocene Chalk-surface contours, the most 

 outstanding features are that there appears to be a drop from the 

 figure of 1,350 feet at Happisburgh down to 1,000 feet at Aldeburgh, 

 and the prevailing direction of the lines is N.E.-S.W. There can be 

 very Itttle doubt but that we have here the last remaining evidence 



