40 NEW YORK STATE MUSEUM 



fault plane, the upper portion of the Trenton-Utica passage beds is 

 exposed near the mouth of Orum creek, at an elevation of 80 feet 

 above the river, and on the south side, at Indian Castle, the same 

 rocks show only 30 feet above the river level, with the Utica out- 

 cropping close at hand and only 20 feet higher up. The westerly 

 dip would carry these rocks down to, and slightly below, the river 

 level before reaching the fault line. Hence it is inferred that no 

 great thickness of Utica shale, say 100 feet as a maximum, can 

 be involved east of the fault line, and that therefore the throw of 

 the fault at Little Falls is certainly as much as 750 feet, and lies 

 somewhere between that figure and 850 feet. 



South of the Mohawk, after climbing the hill, the Trenton and 

 then the passage beds are at the surface on the Avest, and the Utica 

 shales on the east of the fault. Since, however, the Utica is at 

 the river level on the east side, since the altitude here is from 500 

 to 600 feet above the river, and since the dip is to the south about 

 100 feet to the mile, the horizon in the Utica. must be in the 

 neighborhood of from 650 to 700 feet above the base of the forma- 

 tion, so that the throAv has not greatly diminished in this direction 

 if it has at all. 



The fault plane crosses the river with an approximately north- 

 east and southwest trend. Within the first mile north of the 

 river it SAverves someAvhat to the north, and then curves sharply 

 westAvard through an angle of nearly 90°, continuing in this new 

 direction for a mile, Avhen it again swerves to the northAvard at a 

 sharp angle. In this AA^estAvardly trending portion the fault is 

 not a single sharp break as heretofore, but shoAvs Utica shale on 

 the doAvnthroAv, and BeekmantoAvn rocks on the upthrow side, 

 Avith a zone of much shattered Trenton betAveen, having a varying 

 breadth of from 100 to 300 yards; in other words, the fault is 

 doubled through this part of its course Avith an intermediate 

 shattered zone of no great breadth. 



The accompanying section [fig. 5 a], made along the road which 

 crosses the fault line midAvay in this part of its course, shows the 

 usual conditions, though Avith less minor breakage than usual. 

 Just to the Avest of the road in the fields, displaced blocks of the 



