GEOLOGY OF THE VICINITY OF LITTLE FALLS 43 



of the fault (310 feet) was made here, and is accurate for the 

 one fault, whose throw is just the thickness of the Beekmantown 

 here, approximately 300 feet. But the real throw here Is the 

 combined throw of the two faults, and the second fault throws 

 out the entire Trenton, the passage beds, and an unknown amount 

 of the Utica, so that in the writer's judgment its throw is equal 

 to, or exceeds that of the main fault, as from 100 to 200 feet of 

 the Utica seem clearly to be inyohed. If that estimate be cor- 

 rect, the combined throw of the two faults here giyes a total 

 which does not fall far short of the throw of the single fault east 

 of Little Falls. 



One mile farther north the pre-Cambrian rocks appear at the 

 surface from beneath the Beekmantown on the upthrow side of 

 the fault, and thence northward are continuously at the surface 

 on that side. The Utica is the surface rock on the other, but does 

 not show in outcrop anywhere near the fault line. The more 

 northerly of the sections of the structure section sheet crosses 

 the fault line hereabout. The throw of the fault here is some- 

 what conjectural, since the amount of Utica inyolyed is unknown. 

 The Beekmantow^n has thinned to only about half the thickness 

 present at Little Falls, but the Trenton and passage beds seem 

 somewhat thicker here than there, though outcrops do not suffice 

 for any precise measurement of their thickness. The horizon in 

 the Utica would seem certainly higher than at Little Falls. It 

 is thought that this, with the thicker Trenton, will largeh^ make 

 up for the diminished BeekmantoAvn thickness, so that, while 

 the thfow here may be 100 feet less than at Little Falls, that is 

 an outside limit. 



All along this part of its course the absence of outcrops on the 

 east side of the fault makes it impossible to determine whether 

 the fault branches or consists of a single break, though in the 

 absence of any evidence to the contrary the latter is regarded 

 as most probable. 



Dolgeville fault. This fault can be traced for only IJ miles, 

 beyond which its farther extent in both directions is concealed by 

 heavy drift deposits. To the south it must soon disappear because 



