GEOLOGY OF THE NORTHERN ADIRONDACK REGION 437 



ing of the ice sheet or at a somewhat later period, spaall local 

 glaciers appeared high up on the mountain sides which, grinding 

 away at their beds, with this bergschrund action at work on their 

 sides, excavated the amphitheaters. But, while the ridges have 

 thus been ice-sculptured, it is wholly unlikely that they were 

 produced by glacial action. The ice found the ridges and valleys 

 when it entered the region and merely left them somewhat modi- 

 fied. Some of the back slope cliffs strongly suggest fault scarps. 

 One for example, suggests a fault across the ridge crest which 

 has dropped its southern portion and produce the clifif and ter- 

 race outline. There is but a single sort of rock in that ridge, a 

 resistant quartz syenite gneiss, so that the topography can not 

 be accounted for by varying rock resistance. The sudden manner 

 in which many of the ridges are chopped off at the south is very 

 indicative of faulting. If faults are present, they are cross faults, 

 since the main ones parallel the ridges. It is an exceedingly 

 difficult matter to determine just how large a share the faults 

 have had in determining the present situation and character of 

 the ridges. 



Streams 



The workinig out of the varied history of the Adirondack 

 streams is a matter of the future. No one hias yet had opportunity 

 to give the problem the thorough anid exhaustive study that it 

 requires. Furthermore, it is a difficult problem, owing to the 

 great age of the land area, the several oscillations of level which 

 it has experienced, the difficulty of determining the controlling 

 factors in the Precam.bric district, and the many changes pro- 

 duced in the drainage by the action of the ice sheet.^ 



The general drainage of the present dlay runs' radially outward 

 from the main axis of elevation, and in part these streams seem 

 the lineal descendants of the original consequent streams. Since 



^No attempt will be made in this paper to discuss tlie Pleistocene history 

 of the region, since little connected work has hitherto been done on it. and 

 because Professor Woodworth is now at work on the problem. Much 

 information may be gained from papers by Brigham and Ogilvie. Geol 

 Soc. Am. Bui. 9:183-210; Jour. Geol. 10:397-413. 



