GEOLOGY OF THE PARADOX LAKE QUADRANGLE 



465 



The drainage is well-adjusted, the principal valleys being either 

 upon the limestone or in the depressions occasioned by block 

 faulting. The limestone valleys are usually wider and physiograph- 

 ically older than the faulted valleys. This contrast is shown in 

 plate 1, figure 2, where Chilson lake in the foreground lies in a lime- 

 stone valley, while the steep face of Knob mountain marks a fault 

 cliff which extends northward about five miles. 



Glacial agencies have interrupted the last erosion cycle, hence this 

 valley at the foot of Knob mountain is not occupied by a single 

 stream but by three small lakes and a considerable extent of swamp, 

 outletting westward in its middle portion. The limestone valleys 

 are also drift-filled, but their drainage is usually not so markedly 

 disarranged as it is in the narrower faulted valleys. Plate 3, figure 1, 

 illustrates the condition in the wider valleys. 



PART 2 



PHYSIOGRAPHY AND GL A CIO LOGY 



Cambric drainage lines 



Certain main lines of drainage were established before the close 

 of Cambric time. These have been greatly modified by later adjust- 

 ments — in addition to normal valley development, drowning, rejuve- 

 nation, faulting and glaciation entering into their history at various 

 times — nevertheless the Cambric drainage can be made out and is 

 in some localities remarkably similar to the present. 1 



The Lower and Middle Cambric strata are found in Vermont; 

 only the Upper Cambric in the Adirondacks. This fact indicates 

 that the Cambric sea advanced from the east, its progress being 

 slow. It covered Vermont in Middle Cambric time, but did not 

 reach the Adirondacks until the Upper Cambric. 



Hence in Lower and Middle Cambric time the Adirondack region 

 was a land area, and was consequently being worn down by streams. 

 Prof. Kemp has shown that these Cambric streams were well 

 adjusted to the structure, having placed their valleys on the lime- 

 stone, and that these valleys had mature profiles and cross-sections. 



*J. F. Kemp. Physiography of the Eastern Adirondack's in the Cambrian 

 and Ordovician Periods. Geol. Soc. Am. Bui. 8:408-12. 



