230 GEOLOGY OF OLD HAIVIPSHIEE COUNTY, MASS. 



TOPOGRAPHY. 



The mica-schist, when set on edge, is usually the more durable rock, 

 and appears in the row of hills — Mallards Hill, Beech Hill, Pitts Hill, Fall 

 Hill — which sharply border the gneiss, depression of North Orange; and 

 where the central anticline brings up the amphibolite and whetstone it 

 produces the "Brush Valley," and the mica-schists, divaricating on the west 

 from the main body, formed the long ridge of Barbers Hill. At the same 

 time the quartzites, sharply folded and compacted with granite, rise high 

 above the level of these hills in Mount Grace. On the other hand, in the 

 next anticline to the east the "Big Tully Mountain," made of granite, rises 

 to a peak which dominates the whole region. The Swift River fault runs 

 between these two basins, and some comparatively modern elevation may 

 explain the discrepancy. 



SOUTH ORANGE AND NEW SALEM. 



The western border. — The western-border beds cross the river east of 

 West Orange and go south down the west line of Orange, crossing the 

 corner of Wendell and continuing south along the New Salem-Shutesbury 

 line, where they become involved in the West Branch fault. 



The following section across the middle of this town line, from the 

 schoolhouse in the west edge of Shutesbury, gives the succession of all 

 the strata, including the mica-schist : 



Section in Shuteshnry. 



Feet. 



1. Monson gneiss (a) 



2. Granular, micaceous quartzite (Rowe) (b) 100 



3. Amphibolite (Chester) (d) 100 



4. Rusty, contorted, chloritic seri cite- schist (Savoy) {e) 325 



5. Amphibolite 16 



6. Dark-gray, spangled mica-schist (Conway) (/) 



The latter bed is graphitic, garnet-bearing, contains transverse biotite 

 scales, and is identical with the Conway schists. It includes a single bed of 

 thin-fissile quartzite, consisting of a limpid quartz like that of a mineral vein. 



This border series seems to meet the fault line at a very acute 

 angle, so that in the hill just north of Cooleyville the lower member of 

 the section above is cut out and the amphibolite (d) abuts against the 



