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NEW YORK STATE MUSEUM 



In the eastern Adirondack^ there is some evidence of yet more 

 recent faulting, which may have utilized the already formed fault 

 lines, or constructed new ones, the former seeming the more 

 probable supposition, though it is in general impossible to say 

 which was the case. So far as known to the writer, the evidence 

 for this later faulting is topographic simply, certain prominent 

 fault scarps being difficult of explanation except on this assump- 

 tion. 



These Paleozoic faults are for the most part readily made out in 

 the marginal belts of Paleozoic rocks of the Champlain and Mo- 

 hawk valleys. They are not so readily discoverable on the north, 

 owing to the very low northward dip of the Potsdam and Beek- 

 mantown formations there, the great thickness of both these for- 

 mations and the northerly slope of the surface in the same direc- 

 tion as the rock dip, giving them great breadth of outcrop ; while 

 their various beds are so similar lithologically and so unfossilifer- 

 ous that precise horizons are not to be made out, in a district of 

 such scanty outcrops. Enough evidence can be obtained however 

 to show that the faults do occur, and that the conditions are 

 quite like those on the south side of the region. The strong prob- 

 ability is that the faults, or rather the faulting, extend clear 

 across the region. Evidence of their presence is frequently forth- 

 coming in the Precambric areas, but in these it will require 

 the closest sort of areal work to disclose and to map them 

 accurately. 



Faults most abound and attain greatest magnitude along the 

 eastern border of the region. Thence westward they diminish in 

 number and in importance, though large faults occur as far west 

 as Little Falls in the Mohawk region, and at Potsdam on the 

 north, and small ones, at least, are found still farther west. 



The greater breaks of the region are meridional, trending from 

 a north-south to a northeast-southwest direction. They therefore 

 rudely parallel the strike of the Paleozoic rocks in the Champlain 

 region, while in the Mohawk region, and on the north, they cut 

 it at a high angle, forming what are known as dip faults, the 

 others being called strike faults [fig. 3, 4]. The large majority 

 of them downthrow to the east and with their rude parallelism 

 divide the region into a series of strips, or slices, this slicing 

 apparently characterizing the bulk of the Adirondack region. 



