GEOLOGY OF LAKE PLEASANT QUADRANGLE 53 



course of Ninemile creek. A shear zone was noted in the creek 

 about a mile below Helldevil dam. The topographic effect of this 

 fault is marked with downthrow side on the north. Its amount of 

 displacement is at least several hundred feet. The continuation of 

 this fault for some miles into the Piseco Lake quadrangle is clearly 

 indicated by the topography. 



North Branch-Moose Mountain fault 

 A clearly defined, prominent fault with northeast strike lies along 

 the eastern bases of Moose and North Branch mountains and Chub 

 mountain of the Piseco Lake sheet. For 7 or 8 miles the steep 

 fault scarp rises 400 to 900 feet as a bold topographic feature. The 

 upthrow side of the fault is on the west. The actual displacement 

 appears to be no less than 500 or 600 feet. An excellent sheared 

 rock zone was observed in the creek at the base of Moose mountain. 

 Due to the tilting of the fault block, there is a long, westward 

 downslope of the several miles from the crest of the scarp to the 

 Sacandaga river on the Piseco Lake sheet. Only a few small, very 

 swift streams flow down the fault scarp side. 



Silver Lake outlet fault 



The position of this fault is well marked by the topography and 

 usual stream adjustment along the line of fracture. The down- 

 throw side is on the west with maximum displacement no less than 

 200 feet within the map limits. This fault extends for some 6 miles 

 southwestward to Pine lake and Pine mountain of the Gloversville 

 sheet and, along this southern part, the displacement is no less than 

 500 to 700 feet. 



Sugarloaf-Silver Lake Mountain fault 

 This northeast-southwest fault passes along the eastern bases of 

 Sugarloaf and Silver Lake mountains and thence along the Sacan- 

 daga river to near the southern map edge. Its topographic influence 

 is distinct. Northward, as indicated on the map by the broken line, 

 this fault is thought to be continuous with the Jimmy Creek fault. 

 The topographic evidence very strongly favors this view. South- 

 ward from where it crosses Ninemile creek, the downthrow side is 

 on the east, but northward, between that point and the river, the 

 downthrow side is on the west due to the great downsinking of the 

 fault block between the Whitehouse and Moose Creek faults. 

 Along the trail at the eastern base of Sugarloaf mountain, there is 



