178 PEOF. J. PRESTWICH ON A SOUTHEET^^ DEIFT IJf THE THAMES 



Fig. 10. — Diagram of the lines of Elevation hounding the Tertiary 

 Basin of the Thames, showing their relative Age and Direction. 



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1. Anticlinal axis of the Weald (Late Pliocene). 



2. Escarpment of the Chalk. 1 /-^ i t>i • <. \ 



3. Escarpment of the Oolites. } ^^^^'^^ Pleistocene). 

 V. Valley of the Thames. 



-*- Dip of the strata. as>--*-Lines of drainage, 



8. General Nummary, 



The results of the foregoing inquiry may be summed up under 

 the following heads : — 



1. That the Westleton Shingle ranges from the Crag in Suffolk 



inland to the Chalk-escarpment in Oxfordshire and Berkshire, 

 rising gradually from the sea-level, until it attains a height of 

 from 500 to 600 feet. 



2. That the Tertiary strata were co-extensive with this Shingle 



at the time of its deposition, and that both extended to the 

 edge of the Chalk-escarpment, where they have been cut off 

 by subsequent denudation. 



3. That the upraising of the floor of the Westleton sea, or of the 



Westleton Shingle, immediately preceded the advance of the 

 Glacial deposits, so that while they are concordant or in con- 

 formable superposition in the eastern counties, they become 

 discordant as they range westward, and the Boulder-clay 

 occupies valleys formed, after the rise of the Westleton Shingle, 

 by early glaciation. 



4. That the belt of Tertiary strata and of Westleton Shingle on the 



northern borders of the Chalk-Basin, formed originally a con- 

 tinuous and unbroken zone, and that this was not broken 

 through until after the elevation of the Westleton floor and 

 the inset of the Glacial period. 



