374 SECTIONAL TRANSACTIONS.—C. 
Saturday, September 7. 
Excursions to (a) North Norfolk Coast (9.30). 
(6) Sudbourne and Orford (9.30). 
Sunday, September 8. 
Excursion to Ipswich, Bramford, Hoxne (10.0). 
Monday, September 9. 
Jomst Symposium AND Discussion with Section E (Geography) on 
Denudation chronology (Section C room) (10.0). 
Dr. S. W. Woo.pripce.—The principles of denudation chronology, 
with special reference to south-east and south-west England. 
The study of erosion surfaces is a young and undeveloped branch of 
geology, and one that has many purely geographical aspects. Little notice 
was taken of such features until early in the present century, but since that 
time many largely isolated and unrelated observations have been made 
in this country. In both Continental Europe and America the subject 
has enjoyed a more favourable position. In this discussion a review 
of the facts and of the methods of inquiry and interpretation will be 
attempted. 
The major erosion surfaces entering into the constitution of the British 
landscape are of two kinds: (a) uplifted peneplains (or peneplanes) formed 
under subaerial conditions and never covered save by regolith or thin 
continental deposits ; and (b) stripped planes of unconformity, secondhand 
peneplains, trimmed by marine abrasion, in most cases. Less extensive 
surfaces—old valley floors—can also be recognised, and to these also 
American usage extends the term peneplain, but some alternative term 
seems desirable. 
Whether subaerial or marine, erosion surfaces must be expected to show 
appreciable gradients, quite apart from later warping, if any. Correlation 
on a basis of essential flatness along directions measured at right angles to 
present or former coastlines, leads only to absurd and impossible conclusions, 
in most cases. 
In all the major regions of Britain which have yet been studied, there are 
the remains of a gigantic physiographic stairway of erosion levels—a succes- 
sion of uplifted and dissected base-levels—which contains the elements of 
a scheme of denudation chronology, running parallel with the later stages 
of stratigraphical history. Interpretation is hindered, however, by the 
difficulty of distinguishing between Tertiary and older exhumed surfaces. 
In these circumstances it is essential that interpretation should begin in 
south-east England, where surfaces can be dated with reference to deposits 
of known age. 
With this principle in mind a summary will be given of the denudation 
chronology of south-east England, where sub-Eocene, Miocene, sub-Pliocene 
and various Pleistocene surfaces can be traced, and the form of the sub- 
Cretaceous surface can also be approximately ascertained. By means of 
the evidence of river-profiles the later stages of the chronology can be 
confirmed. 
The conclusions drawn from the study of these surfaces in south-east 
England will be briefly applied to the problems of south-west England. 
