278 



GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



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the iron oxides to the soluble form in which they were concentrated in the 

 limestone bands as a preliminary to their change to amphibolite. It is, 

 however, wanting below the hornblendic bands, which 

 rest directly on the dark-gray and finei" mica-schist. 

 This makes it probable that none of the hornblendic 

 bands are overturned, though overturn may possibly 

 have preceded the final metamorphism. 



In places the passage of the amphibolite into the 

 mica-schist is by alternate bands and thin lenses of 

 the two rock varieties, and the passage beds may be 

 3 or -4 feet thick. This is more like the passing of 

 one sedimentary layer into another than like the con- 

 tact of an eruptive on a schist. 



The schists of the area just described are cut off, 

 going eastward, by a great drumlin, though the 

 quartzite can be followed by its north end. Beyond, 

 one finds sections which expose the whole thickness 

 of the schists and amphibolite bands. 



They are best studied in the area east of the 

 Purple blind road (see map, PI. IV, and fig. 19 for 

 section, and " Petrographical description," Nos. 16-21, 

 p. 293), where, commencing in the chestnut woods 

 northeast of the end of the road, at the basal con- 

 glomerate (a, fig. 19), we .pass south over a broad 

 area of the lowest inica-schist (b), broad because of 

 the low dip, and come upon the lowest amphibolite 

 (c), a band about 13 feet thick, here, as always, quite 

 ferruginous and pyritous. Fifty feet beyond there is 

 a second bed of the hornblendic rock (d) like the first, 

 and both are capped by the white mica-schist layer 

 described above. Farther on 66 feet, at the top of 

 the ridge, near a large chestnut tree conspicuous in 

 the open field, there is a third, rudely foliated layer 

 of amphibolite (e), thicker than the others. This is 

 capped by a bed 3 feet thick of a rusty limestone (/), 

 carrying abundantly cinnamon-colored garnet in large, shapeless masses 

 and light-green pyroxene, and by a thin band of quartzite. The thi-ee 



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