GEOLOGY OF THE BROADALBIN QUADRANGLE 39 



ness of the formations at this point shows that the displacement is 

 at least five hundred feet. The fault line is not straight but its 

 general course is northward to northwestward from the Aloha wk 

 river to where it cuts across the northwestern corner of the Broad- 

 albin quadrangle. This fault has been traced for a distance of at 

 least thirty miles. 



The Noses fault enters the sheet two and one-half miles north- 

 northeast of Mayfield from which point it strikes north-northeast 

 along a fairly straight line through Gifford's valley and thence off 

 the map. The upthrow side is on the west. Because of heavy 

 drift piled against the fault scarp the fault plane is at no point 

 visible, but the line of fracture can be pretty accurately traced. 

 Every evidence points to a very steep if not vertical fault plane. 

 A good idea of the amount of displacement may be obtained in 

 Gifford's valley where the base of the Little Falls dolomite is 

 sharply faulted against the Precambric under Buell mountain. The 

 base of the dolomite here lies at an elevation of 800 feet, but there 

 are something like 200 feet of Paleozoics below the dolomite so 

 that the Precambric surface is about 600 feet above sea level. 

 On top of Buell mountain the Precambric lies at 2020 feet which 

 makes a difference of 1420 feet in elevation of the Precambric 

 on opposite sides of the fault, all due to faulting. If we add the 

 unknown thickness of Precambric eroded from the mountain 

 top since the faulting occurred we get a total displacement of 

 the fault here of at least 1500 feet. The dolomite beds dip toward 

 the fault plane at angles of from five to twenty degrees and this 

 is quite the reverse of the updrag effect in the shales along this 

 fault west of Johnstown as well as along most of the Mohawk 

 valley faults. A small but very distinct fracture, which appears 

 to be a branch of the main fault, runs through Gifford valley. 

 This fault is clearly traceable by means of the topography and by the 

 brecciated zone, and although its throw could not be exactly deter- 

 mined, it is probably not over fifty feet. It downthrows to the 

 east. 



The presence of this little outlier of Paleozoics in Gifford valley 

 is due to the fact that the sediments have been sharply faulted 

 against the base of the mountain and have thus been protected 

 against entire removal by erosion since the faulting. 



On the divide, about a mile south of Gifford valley, the throw 

 of the Noses fault lias diminished by two or three hundred feet. 

 Two miles south of the valley a small wedge of the Theresa forma 

 tion lies against the fault plane. West of Cranberry Creek the 



