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NEW YORK STATE MUSEUM 



suggestive of recent faulting and tilting, since there is no topo- 

 graphic break between the two rocks, yet one is far less resistant 

 than the other. 



The only difficulty in the way of considering this the prolonga- 

 tion of the Tracy brook fault is the sharp change in direction 

 from southwest to south at the point of Rand hill. It is quite 

 possible that this point marks the junction of the Tracy brook 

 fault with a north and south fault, of whose existence the topo- 

 graphy on that line north of Rand hill gives some evidence. At 

 the best, however, this is not a fault of great throw, while that 

 on the east edge of Rand hill is directly comparable in magnitude 

 to the Tracy brook. As it can be traced to the south beyond 

 the limits of the sheet and clearly connects with the Tracy brook 

 fault, it gives great length and importance to this. If the writer 

 be correct in the belief that the Oalciferous comes clear to the 

 edge of Rand hill, the entire Potsdam being faulted out, then the 

 throw of the fault there is as great, or greater than at Chazy vil- 

 lage, where it is about 2000 feet. 



Another considerable fault occurs between the Calciferous at 

 West Chazy and the Chazy limestone to the northward, the latter 

 dipping directly toward the fault. The throw of this fault can 

 not be determined owing to the uncertainty as to the precise 

 horizon in the Calciferous of the West Chazy exposures. 



Other faults or probable faults are (a) one in the extreme north 

 that limits the passage beds on the west, which have a low north- 

 westerly dip, yet suddenly disappear and are replaced by Potsdam 

 to the westward; (b) a fault of unknown throw in the Potsdam at 

 Jericho, with the red, basal beds on the east side and a coarse, 

 glassy sandstone on the west, the one horizontal and the other 

 with a 6° dip to the west; and (c) a more doubtful fault across 

 Rand hill, separating the Potsdam and Dannemora gneiss on the 

 west from the gabbro on the east. 



In addition to these greater faults there are a multitude of 

 minor breaks in the pre-Cambrian rocks at least, best shown by 

 the aid of the later dikes. These are frequently found faulted a 

 few inches or feet, little enough to make the identity of the 



