4^ NEW YORK 5TATE MUSEUM 



Very I real r-visted or contorted structures within the Gren\-ille 

 limestones and associated pyroxene and hornblende gneisses, and 

 also within portions of the mixed gneisses, are frequently met, but 

 practically nothing like distinct folds could be determined within 

 the Grenville formation, or rather such fragments of the formation 

 as now remain. There is no e\'idence that the Gren\-ille strata were 

 ever thrown into folds as a result of any great compressive or 

 mountain-makiBg force brought to bear upon the region, the present 

 strikes and dips probably, for most part at least, ha\-ing been due to 

 tilting and upturning of the strata as a result of the great igneous 

 intrusions. 



Faults 



General considerations. In marked contrast with the eastern 

 and southeastern Adirondack regions, recognizable faults are few 

 in nmnber and tiieir topographic influence relatively minor. Of 

 the five faults represented on the accompanying geologic map, four 

 strike northeast-southwest or parallel to the predominating fracture 

 lines of the Adirondacks. All five of the faults might more properly 

 be called zones of fracture or crushed zones which are nearly 

 strai^t for considerable distances. In no case was the whole dis- 

 placement found to follow a sharply defined fatilt-stu-face, but 

 rather there are broken-rock zones from 25 or 30 to 100 or more 

 feet wide in which fault breccias, slickensided surfaces, and local 

 fault surfaces are frequently seen. 



Referring to apparently similar phenomena on the Long Lake 

 sheet. Professor Gushing says: "Lines of excessive faulting are 

 not infrequent in the eruptives. In such places from two to four 

 joint sets are well marked, and the joints are closely spaced, their 

 distance apart being measured in inches rather than feet, chopping 

 up the rock into a multitude of small blocks, and forming prominent 

 lines of weakness in it. Often multiple faulting has taken place 

 along these strips on one of the joint sets., grinding and slicken- 

 siding the rock surfaces." ^ The longest shattered-rock zone of this 

 kind mentioned by Gushing on the Long Lake sheet is in the 

 Raquette falls gorge which is nearly a mile long. Within the Blue 

 Mountain quadrangle, the writer has in several instances observed 

 crushed-rock zones frequently occurring along nearly straight lines 

 for from 2 to 8 nules, and with distinct topographic influence. 

 Such alignments of crushed-rock zones are regarded by the writer 

 as due primarily to faulting, probably multiple faulting. Further- 



Y. S:5.te Mns. But. 115. p. 488. 1907. 



