' ' ' GEOLOGY OF THE BROADALBIN QUADRANGLE 49 



mile west of Broddalbin. In the village, however, the dolomite 

 was struck under thirty feet of drift in a well on the Husted place. 

 A mile south of North Broadalbin Trenton and Canajoharie out- 

 crop close together. Where the fault crosses Kennyetto creek 

 numerous fragments of the Trenton and Lowville limestones make 

 the presence of these formations almost certain here. The south- 

 ward extension of the fault is completely drift covered but it prob- 

 ably disappears near the map edge. Northward it has disappeared 

 before reaching the point one mile south of North Broadalbin 

 where Trenton and Canajoharie are in normal position. Just west 

 of Broadalbin the dolomite lies about sixty feet above the Canajo- 

 harie shale and to this must be added the whole thickness of Black 

 River-Trenton limestone and an unknown thickness of shale in 

 order to give the amount of dislocation. Darton estimates the 

 throw here at two hundred feet and it is quite certainly not more 

 than this. 



TROUGH FAULTING 



The Batchellerville and Noses faults run approximately parallel 

 and are about six or seven miles apart, the great escarpment of 

 Precambric rock of the one fault facing the equally great escarp- 

 ment of the other. In other words we have here a fine illustration 

 of trough faulting, the whole country between the Batchellerville 

 and Noses faults being a great depressed block much of which now 

 lies fully one thousand feet below the level of the scarps on either 

 side. A glance at the Broadalbin sheet will show the extent of 

 this fault block which occupies at least seventy-five square miles or 

 all of the region between the following points : Three miles north 

 of Batchellerville ; two and one-half miles northwest of Northville ; 

 two miles west of Mayfield ; and two miles southeast of North- 

 ampton. On the State geological map the deep indentation caused 

 by the northward extension of the Paleozoic rocks to Northville 

 roughly corresponds to this depressed block, although recent map- 

 ping by the writer shows that the Paleozoics should extend at least 

 six or eight miles farther northward along the Sacandaga river. 

 This great trough block is not perfectly simple because, on the west 

 side especially, a number of minor fractures have considerably 

 modified it and some of these minor faults are so arranged, as at 

 Northville, that small trough fault blocks are included between 

 them. t 



Eastward from the great trough block and lying between the 

 Batchellerville and Hoffman's Ferry faults is a great upraised block 



