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NEW YORK STATE MUSEUM 



small throw, or at least of small heave, the dikes being shifted 

 laterally a few inches, or a few feet. More rarely the fault is 

 of sufficient dimension to cause the disappearance of the dike on 

 one side, its new position being beyond the limits of the outcrop. 



Since these dikes are themselves of late Precambric age, the 

 fact that they are faulted would indicate a very late Precambric 

 age for the faulting, provided it is Precambric at all. The only 

 evidence of such age is the fact that the later faults, so far as 

 they have been made out, are less numerous and of larger throw. 

 While this is suggestive, it is but slender evidence for making such 

 a discrimination. 



As will shortly be shown, joints abound in the Precambric 

 rocks. In numerous instances evidence of vertical slipping along 

 these joints is forthcoming, the immediate rocks being much 

 crushed and sheared, and the planes of slip thoroughly slicken- 

 sided. Excellent illustrations may be found in the numerous rock 

 cuts along the railroad between Saranac Inn and Floodwood, in 

 Franklin county. The anorthosite is seen to be locally much shat- 

 tered, abundant joints dividing it into parallel sheets of a thick- 

 ness of from 2 inches to 4 inches, the rock material much crushed 

 and sheared and the sheets slickensided on both surfaces. The 

 whole zone so affected varies from a few feet to a few yards in 

 breadth, grading off into the normal rock. The frequency of the 

 phenomenon in these excellent exposures suggests that it can 

 hardly be local, and that the fact that it has not been more widely 

 noted may likely be owing to the general poor and unsatisfactory 

 character of the usual exposures in the woods. That, in other 

 words, it is a common occurrence. 



Here again the evidence that the faulting may be of Precam- 

 bric age is merely the difference in character. The Paleozoic 

 faults are fewer and of large throw, and so far as noted do not 

 consist of numerous small slips along closely recurring joint 

 planes, with the production of a multitude of slickensided sur- 

 faces. Here again the evidence is far from conclusive. There is 

 however a system of joints in the Precambric rocks which ante- 

 dates the Paleozoic, since there are more joint systems in the 

 former than in the latter rocks. If it could be demonstrated that 

 the system of joints along which this faulting took place was 



