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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 limestone 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 underthrown 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 topographical 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 overlying 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

  1. ↑ At South Canaan. This is not the Cobble already referred to and located on the map (Cf. Plate V.)
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