794 THE JOURNAL OF GEOLOGY. 



ticularly along its west margin the rock is found to be seamed 

 with vein quartz in every direction. These characters have not 

 been found outside of the ridge, which is rarely over a quarter of 

 a mile wide. The well known greenish tremolite of Canaan is 

 from Maltby's Quarry at the extreme south of this ridge. The 

 rock was provisionally designated the tremolitic quartzitic lime- 

 stone and its area was mapped. Sudden changes in the strike 

 and dip of the beds were found to be particularly common in 

 this ridge. 



Now that the stratigraphy has been determined, there seems 

 to be no reason to doubt that this ridge marks the course of a 

 great reversed fault, which in its upthrown limb brings the 

 Canaan Dolomite against the newer beds in its western or under- 

 thrown limb. The development of tremolite is ascribed to the 

 profound shearing which has occurred along the fault plane, and 

 the ragged dolomite filled with quartz veins to fracturing or 

 crushing and recementing of the fragments by the silica of 

 waters which have percolated along the fractures — in other 

 words, it is a fault breccia. The ridge has survived as a topo- 

 graphical feature, because of the framework of quartzite and vein 

 quartz and the imbedded crystallized silicates in the dolomite. 

 The fault line may be followed by these characters from near 

 Sheffield village to Maltby's Quarry, northwest of South Canaan, 

 a distance of about ten miles. To the northward it probably 

 connects with some of the faults of Vosburgh Hill, but its course 

 here has not been followed. To the south of Maltby's Quarry 

 the fault is followed in the direction of the prevailing strike to 

 the northeast base of the Cobble, 1 which base it coincides with 

 for some distance. This, as will be more fully shown later when 

 that area is described, is indicated by the Cambrian Quartzite 

 being absent, the actual contact of gneiss and apparently over- 

 lying Canaan Dolomite being exposed. On the west base of 

 this narrow hill, the quartzite is present separating the gneiss and 

 dolomite, and it also runs around the north end of the hill to 



x At South Canaan. This is not the Cobble already referred to and located on the 

 map (Cf. Plate V.) 



