6o NEW YORK STATE MUSEUM 



Southward it runs into shales and can not be traced. Northward 

 there are indications of it for a mile, beyond which it is hidden by 

 drift. 



McGregor fault. Darton spoke of the group of faults about 

 Saratoga as the Saratoga faults. The group seems to us to consist 

 of a main fault with branches and we desire to retain the name 

 Saratoga fault for the branch in the village, often called the 

 *' Springs " fault. The grand scarp of the main fault along the 

 front of Mt McGregor has suggested that as a most fitting name 

 for this fault. 



In front of Mt McGregor the fault has Precambric rocks on the 

 upthrow side and Canajoharie shale on the downthrow, so that 

 the full thickness of the Potsdam, Theresa, Hoyt, Little Falls and 

 Amsterdam formations is faulted out. This means a minimum 

 thickness of at least 600 feet ; in addition there is another thickness 

 of 600 feet of Precambric in the fault scarp, with the summit likely 

 200 feet below the horizon of the base of the Potsdam. How much 

 thickness of the Canajoharie shale is involved is uncertain, but the 

 throw of the fault is certainly 1400 feet at Mt McGregor, and likely 

 200 feet more than that. It seems to be increasing toward the north. 

 Near Kings Station, 4 miles north of Saratoga, a branch fault sets 

 off from the main fault toward the northeast, bringing a block of 

 Little Falls dolomite to the surface between the shales and the 

 Precambric. This may be called the Gurnspring fault. Carbonated 

 waters rise along it in the same way and under very similar 

 structural conditions as they do along the Saratoga fault. This 

 block of dolomite seems cut off at the north by shales, and hence by 

 another fault, but rock outcrops are so few that conditions are very 

 conjectural. 



To the northward the McGregor fault runs as one of the prom- 

 inent breaks of the region, passing to Lake George and forming the 

 prominent fault scarp along the west shore of the lake and of 

 Northwest bay, at the apex of which it passes inland away from 

 the lake. 



Between Kings Station and St Clements the McGregor fault runs 

 unbroken, but at the latter place, somewhat over a mile north of 

 Saratoga, it sends off two branches, much diminishing the throw of 

 the main fault. This swerves around to the west and becomes 

 eventually lost under the heavy drift of the Kayaderosseras valley. 

 Its throw is rapidly diminishing and it probably dies out in that 

 district. 



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