GEOLOGY OF THE LONG LAKE QUADRANGLE 489 



quent and important structural features in the Paleozoic rocks 

 which fringe the Adirondacks ; that they most abound on the east; 

 that on the north and south they diminish in number and mag- 

 nitude going westward, and that on the west they are small and 

 infrequent. It is also known that they are normal faults with 

 nearly vertical hade; that many of them have throws of several 

 hundred feet (some of from iooo to 2000 feet); that the principal 

 ones run north to northeast; that there are numerous cross faults 

 running west to northwest ; and that from the Paleozoics they run 

 into the crystalline rocks with their magnitude unimpaired. A 

 priori therefore their presence should be expected in the Adiron- 

 dacks, and they should diminish in importance westward through 

 the region. 



The Long Lake quadrangle is in the mid- Adirondack region. 

 In the Mohawk valley large faults are found considerably west of 

 its meridian, the Little Falls fault, longitude 74 50', being the 

 •most westerly of the large faults there, and with an average north- 

 northeast trend. Faulting on that trend, prolonged into the Adi- 

 rondacks from Little Falls would involve the Long lake region, and 

 some evidence of faulting would naturally be expected, though not 

 as prominently as would be the case farther east. 



Actual evidence of faulting is furnished by the slickensided char- 

 acter of the multiple joint surfaces previously described, but this 

 seems to be faulting of very ancient date, and is not the common 

 type of faulting, here under consideration. 



The indirect evidence for faulting in the district is twofold. 



1 Topographic. As repeatedly urged by Kemp for the more 

 faulted district to the east the shape of the ridge blocks, a gentle 

 crest slope in one direction and a steep cliff face in the other, is 

 strongly suggestive of block faulting, and indeed no other reason- 

 able explanation suggests itself for it. Fault scarps of the sort 

 appear in the Long Lake quadrangle. The great cliff on the south 

 side of Mt Morris [see the topographic map and pi. 5] is one such, and 

 is one of the most conspicuous examples in the whole region. The 

 two big ridges to the southeast of Mt Morris are also of the block- 

 faulted type [pi. 19]. But on the whole this type of ridge is not 

 especially prominent within the quadrangle, or at least recent 

 faulting of the sort is not suggested outside of the examples men- 

 tioned. Others of the ridges do somewhat suggest more eroded 

 examples of the same type. 



