LAMPLUGH : NOTES ON THE WHITE CHALK OF YORKSHIRE. 187 
weight ot superincumbent rock. The strata in which we now see 
them were originally covered by at least another 900 to 1000 feet of 
Chalk,* and it is very probable that the greater part of this covering 
was in existence when the folding occun-ed. As to the upward extent 
of the contortions or the mode in which the the forces were manifested 
in the higher beds of the series we have of course now no means of 
judging. As a further mark of the enormous quantity of rock which 
has been denuded from the Wolds since the time of these contortions, 
it will be well noted that, as the photograph shows, there is no feature 
at the surface to indicate the existence of the contorted zone, so that 
had it not been for the accident of a convenient chff-section we should 
not have discovered it here. So far as we can judge, this denudation 
has been effected by subaerial agencies, and not by the planing action 
of the sea, as there are no adequate grounds for supposing that the 
Yorkshire Wolds have been submerged since Miocene times.f 
By these denuding agencies not only has the Chalk plateau 
been everywhere lowered, but its edges have also been cut away, and 
so undermined by the removal of portions of the softer underlying 
clays and shales, that a steep escarpment has been shaped out along 
its inland termination ; and by the prolonged recession of this escarp- 
ment the Chalk has been diraini.shed to its present bounds. Yet 
this denudation has been accomplished within time limits, which aro, 
geologically speaking, comparatively short. 
Throughout early Pliocene times the district was probably 
always considerably elevated, and during this period the broader of 
our present Wold valleys were partially excavated. The general 
tendency of the oscillations of level was now however to depress the 
land, and in the later stages of the Pliocene, marine encroachment 
began to affect the area, and a coast-line was carved out across the 
Upper Cretaceous rocks somewhat to the eastward of that of the 
present day. In this coast-line the Headland of Flamborongh 
gradually emerged as a prominent feature. 
With some minor changes of level, these conditions probably 
*See "Notes on the Chalk of Yorkshire." Op. cit. 
t Some interesting data and speculations regarding the subaerial wa>tin(^ 
of the Chalk of the district will be found in the papers by Mr. .f. R. Mortime'r 
and by Rev. E. M. Cole, referred to in the previous part of these Notes. 
