GEOLOGY OF THE NORTHERN ADIRONDACK REGION 405 



formed in Precambric times, the case for the age of the faults 

 would be made out, but this has not yet been successfully done. 



Kemp has described three diabase dikes cutting the ore body in 

 the Hammondville iron mines, which he says fault the ore, rais- 

 ing it about 15 feet in each case.i The dikes appear not to be 

 faulted. If this be true, the faulting could hardly have been later 

 than the time of dike extrusion. A later fault might, it is true, 

 have paralleled the dike, but that this was the case ought to be 

 readily made out in the exposure. This would seem therefore to 

 be a veritable instance of Precambric faulting. 



The older Precambric dikes of the region, more specially the 

 granite and pegmatite veins, are not infrequently found faulted 

 repeatedly and in small amounts, as the diabase dikes are [pi. 11] . 

 Precise evidence of the date of faulting is equally lacking here. 



On the whole then it is to be said that, while demonstrative 

 evidence of Precambric faulting to any special extent has not 

 been forthcoming, it is nevertheless quite probable that such was 

 the case, the faulting having occurred in rather late Precambric 

 time, when, owing to the long conitinued surface erosion, the 

 originally deeply buried rocks had been transferred from the 

 deeper zone of flow to the superficial zone of fracture. 



Paleozoic faults. As such may be classed in all probability all 

 faults found in the Paleozoic rocks and many of those in the Pre- 

 cambric. Faulting may well have been initiated in the region 

 at the time of the uplift which terminated Lower Siluric depo- 

 sition, and which was most marked on the east, being there accom- 

 pamied by some considerable disturbance of the rocks. The great 

 earth disturbances which prevailed in the Appalachian zone 

 toward the close of the Paleozoic would seem more likely to have 

 brought about the major faulting of the region. To the east and 

 south of the district there was a time of disturbance, resulting in 

 prolific faulting, in the Mesozoic; but, if the region in question 

 was also affected, the results can not be discriminated from those 

 produced in the Paleozoic. However, the Champlain and Mohawk 

 faults are of a different type from those which abound in the 

 Newark Mesozoic of New England and the Middle Atlantic states, 

 which is evidence against their being classed together. 



■U. S. Geol. Snr. Bui. 107, p.40. 



