GEOLOGY OF THE NORTHERN ADIRONDACK REGION 429 



amount along this axis during the uplift which terminated the 

 Oretaceous erosion cycle, with accompanying downfaulting on the 

 east, giving the fragments of the Cretaceous peneplain varying 

 altitudes and increasing the prominence of the Champlain depres- 

 sion. 



Lake belt 



In southern Franklin county, nestling in the angle produced 

 by the offset of the main axis of elevation to the west is an area 

 of broad valleys and low ridges in which lakes are more thickly 

 clustered than in any other part of the region, and for which 

 therefore the name " Lake belt " has been suggested, for the lack 

 of a better term. The valley bottoms have the same levels that 

 they have in adjacent districts, but the ridges are low, commonly 

 only 200 feet or 300 feet high, not by any means, attaining the 

 levels that they do in the country east, and considerably lower 

 than the summits in the other direction, though the discrepancy 

 is not so pronounced. The relief is in general insignificant. All 

 the ridge summits are well beneath the horizon of the Cretaceous 

 peneplain level. 



No cause for this discrepancy is to be found in the character 

 of the underlying rocks. These are anorthosite and syenite for 

 the most part, the most resistant of all the Adirondack rocks. 

 The rocks of the Lake belt are in no sense weaker than in the 

 areas of higher altitude and greater relief adjoining, are in fact 

 stronger than those to the west. 



The belt has many features which indicate that the main pre- 

 glacial drainage systems passed through it ; and this would neces- 

 sarily tend to lower its general level more rapidly than would be 

 the case at a greater distance from the main drainage lines. But 

 the fact that it is sharply separated from the adjacent districts 

 instead of fading into them, with no change in the rock character, 

 and the abundant rock ridges, all of small altitude and none reach- 

 ing at all nearly the Cretaceous base level, seem to require a 

 structural cause for their explanation; and it is regarded as a 

 probable dropped fault block, the district to the east having been 



