48 NEW YORK STATE MUSEUM 



the whole State was then upraised practically without folding, and 

 the conditions were certainly favorable for extensive fracturing of 

 the strata. 



Any fault scarps or ridges produced during or at the close of 

 the Paleozoic must have been quite or nearly obliterated during the 

 long Mesozoic period of erosion. If so, how do we account for the 

 present Adirondack ridges which follow fault lines ? As a result of 

 the uplift of the Cretacic peneplain one or both of the following 

 things happened, namely, either that there was renewed faulting 

 or that, as a result of unequal erosion (due to differences in rock 

 character) on opposite sides of the faults, the old fault scarps were 

 renewed. It is quite certain that both things occurred and thus 

 we account for the present Adirondack fault ridges. That some 

 of the faulting actually dates from the uplift of the Cretacic pene- 

 plain, or possibly even later, is proved by the existence of certain 

 fault cliffs in perfectly homogeneous rock masses, and by the fact 

 that many of the tilted fault blocks have been little modified by 

 erosion since their formation. Among many good examples of fault 

 scarps in homogeneous rocks are those on the west sides of Moon, 

 Kelm, and Chase mountains, while tilted fault blocks little affected 

 by erosion are those of Moon, Birch, Crane and Huckleberry 

 mountains. 



Little-Crane-Huckleberry mountain faults. The structural rela- 

 tions shown by these three mountain masses are truly remarkable 

 and the faults are the most interesting within the quadrangle. The 

 deep, narrow rift between Huckleberry and Crane mountains was 

 carefully examined and, judging by the frequency of outcrops, it is 

 quite certain that a narrow belt of Grenville separates the mountain 

 masses as shown on the map. A narrow valley of Grenville, chiefly 

 limestone, with almost continuous outcrops separates Crane moun- 

 tain from the granite ridge just south. Likewise there is a valley of 

 Grenville, chiefly limestone, immediately to the south of the granite 

 ridge (Little mountain and its westward extension). 



In each case the mountain mass of igneous rock presents a 

 high and very steep to almost precipitous wall on the south side, 

 and in each case the belt of Grenville comes abruptly against the 

 igneous rock wall. A slight exception to the latter statement is 

 along the southwestern base of Crane mountain where a small 

 belt of syenite intervenes between the Grenville and the high 

 mountain mass. Almost invariably the rocks of the Grenville belts 

 d:r> at high angles downward and against the faults. The great 



f 



