282 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



Because of its position in the hollows between the hornblendic ridges 

 the mica-schist, which really occupies more of the surface than the former, 

 seems on casual inspection to be of suboi'dinate extent and importance. 



The thickness of the beds, calculated on the average dip of 22°, is: 

 quartzite, 350 feet; mica-schist, 370 feet; hornblende rock, 508 feet; which 

 is certainl}^ far too lai-ge judging from the long line of outcrops farther 

 northeast, and it is probable that each is partially repeated several times by 

 cross faults. 



I have elsewhere suggested that amphiljolite beds of this type are 

 generallv derived from limestone, and in fact the hornblende bands are 

 still locally quite rich in carbonates. At the locality first described above, 

 just east of Fall River, the broad amphibolite band contains layers of lime- 

 stone an inch thick; and farther noi'theast, at a large chestnut tree east of 

 the end of the Purple blind road, there occurs in the same association a bed 

 nearly a meter thick of impure limestone earrjnng' garnet and pyroxene. 

 The development of hornblende at the upper surface of the crinoidal bed 

 has been detailed above, and the large development of hornblende in the 

 quartzite surrounding the limestone in South Vemon points in the same 

 direction. 



THE FELDSPATHIC QrARTZITE. 



Reserving the question of the identity of this rock with the basal con- 

 glomerate, I may first call attention to its curious distribution as shown on 

 the map, PI. IV. It occupies a broad area along the eastern border of the 

 schist series described above, everywhere dips away from it to the east- 

 ward with ap^jarent conformity, and makes the same folds with it all the 

 way from the State line south to the point where the main South Vemon- 

 Bernardston road crosses the railroad, even swinging round to a north-south 

 strike with the schists. Beyond this point it occupies a broad area stretching 

 from the railroad across to the Purple blind road, east of Dry Brook, and 

 is plainly sei3arated from the schists on the north by a curvilinear fault- 

 Thence it continues in a broad band southeastward a long distance and 

 can be followed in scattered outcrops across the sand plains into the town 

 of Gill. Beyond Dry Brook it seems to regain its conformity with the 

 schists. Across the narrow neck by which the West Northfield sands join 

 those of Bernardston the same quartzite reappears in the northwest shoulder 



