78 S. V. WOOD, JT7N., AND F. W. HAEMER ON THE 



Chillesford Clay and the Contorted Drift were removed by one and the 

 same denudation, no evidence has as yet been found to determine, 

 because none of the sections in these outliers of the Contorted Drift 

 have been carried sufficiently deep to disclose it. The thickness of 

 this Drift in one of the outliers, at Kesgrave, section XX. (page 104), 

 would appear, from the well sunk below the bottom of the excava- 

 tions made for brickmaking, to exceed 50 feet; but it is not unlikely 

 that the lowest portion of this may be the Chillesford Clay, because, 

 this Clay being equally a brick- earth with the Contorted Drift, there 

 would be nothing to indicate in the workmen's report of a well- 

 sinking its separate existence from the brick-earth of the Contorted 

 Drift which overlay it. If therefore the Chillesford beds do remain 

 anywhere over the area bounded by the Butley creek and the Stour, 

 it is probable that they do so in the way suggested in sections XX. 

 and XXI. (pp. 104, 105), carried through the Contorted-Drift outliers 

 for the purpose of showing the unconformity between the Lower and 

 Middle Glacial deposits which it is the principal object of this paper 

 to describe ; in which case it seems probable also that they were 

 removed by the denudation which destroyed so much of the Con- 

 torted Drift and gave rise to the unconformity in question. 



2. The Unconformity between the Lower and Middle Glacial, and the 

 Interglacial Valley -excavation which is connected therewith. 



In reference to this unconformity we observed, at page xx of the 

 before-mentioned "Introduction," u that the breaking off of this 

 deposit (the Contorted Drift) into outliers southward is evidently due 

 to a great denudation of the Lower Glacial formation prior to the 

 accumulation of the Middle Glacial sands, which occupy to a great 

 extent troughs or valleys in the Lower Glacial beds ; and that it is 

 quite possible that outliers of it may be concealed under the table- 

 lands of Middle Glacial sand which separate the East- Anglian valleys 

 from each other ; " and we added that "it was clear that the valley- 

 system of East Anglia had its inception in that denudation." 



The existence of this unconfornity in the Glacial series, and of 

 this interglacial excavation of the East- Anglian valley-system, is of 

 more general importance, geologically, than at first sight appears — 

 because, if it were due to a conversion of the area into land after a 

 considerable submergence had occurred giving rise to the Lower 

 Glacial deposits, it indicates an arrest and reversal of the glacial 

 subsidence which is not generally admitted, and has a bearing on 

 one of the theories of climate which has lately provoked so much 

 discussion. 



In entering upon this subject it will be convenient first to examine 

 how far there is any indication of the valleys of Norfolk and Suffolk 

 having had any existence prior to the deposit of the Glacial beds. 



Commencing with the long natural section afforded by the north 

 coast of Norfolk, we find that while the surface of the country 

 intersected by that coast is indented by deep valleys, an almost 

 level floor of Chalk extends along the base of the cliff where these 



