3S0 Eggleston — Eruptive Rocks at Cutting sville, Vt. 



"granite." This hill is crescentic in form, with a knob 

 towards either end of the crescent, the south knob rising 

 about 250 feet higher than the north knob (fig. 4). The 

 shape of the hill is very suggestive of a low glacial cirque 

 tributary to the glaciated valley of Mill Creek. 



Two smaller eruptive bodies lie on the northeast side of 

 Mill River (fig. 1), and, still farther north, a mass of 

 breccia occupies the eastern half of a 1,400-foot hill north 

 of Mill Creek (fig. 4). Including the breccia, the bodies 

 extend along a line nearly 3 1 /-) miles long. The accom- 

 panying geological maps are based upon an enlargement 

 of adjoining parts of the Wallingford and Rutland, Vt., 

 sheets of the topographic map of the United States. 



CONDITIONS OF EXPOSURE. 



Much of Granite Hill, particularly the north and east 

 slopes of the two knobs, is thickly wooded. The bowl, 

 crest, and west slope are fairly free from trees, but the 

 bowl is heavily drift-covered. Along the crest, on the 

 slopes of the north knob, and also at the east foot of each 

 knob, where Mill Creek is actively eroding, exposures are 

 especially numerous ; those on the south knob much fewer. 

 Three small abandoned quarries, several test pits, a pros- 

 pect cut, a tunnel and a railroad cut south of Cuttings- 

 ville (see fig. 1) furnish fresh rock. Ledges and open 

 cuts along a pyrrhotite deposit on the lower southwest 

 slope of Copperas Hill expose a group of dikes presum- 

 ably connected with the main eruptive body (fig. 5). 



Excepting along the crest of the middle part of Granite 

 Hill and for a short stretch along the crest of the south 

 knob, contacts are rarely exposed. As mapped they are 

 accordingly for the most part only approximate. 



OUTLINE OF FIELD RELATIONS. 

 Countey Rocks. 

 The country rocks are all metamorphic — chiefly horn- 

 blende-pyroxene and mica gneisses, with considerable 

 limestone, and quite subordinate chloritic schists and 

 quartzite. In a zone a score or two feet wide along the 

 only visible contact, on the west side of the main eruptive 

 body, they show some contact metamorphism besides 

 moderate brecciation, diking, and impregnation by erup- 

 tive rocks. 



