56 NEW YORK STATE MUSEUM 



ness of this facies to the inclusion of granite from which it is not 

 very sharply separated, taken in the light of various obseiwations 

 made by the writer on the North Creek quadrangle gabbro, strongly 

 supports the view that this acidic facies of the gabbro was pro- 

 duced by assimilation of some granite during the intrusion of 

 the gabbro magma. In this same vicinity some outcrops of rather 

 coarse-grained, nonfoliated gabbro show 5 to 10 per cent red garnets 

 ranging in diameter from a millimeter or two to one-third of an 

 inch. These variations all occur within a stone's throw. Just 

 north of the granite inclusion, the gabbro is medium to fine grained, 

 very gneissoid, and relatively richer in feldspar. Gabbro similar 

 to this latter also appears on the ridge crest about three-fourths of 

 a mile northeast of the granite inclusion; otherwise the many 

 exposures along the whole ridge crest are very typical, medium 

 grained, nonfoliated gabbro with diabasic texture. No. 41 of table 

 4 shows the mineral content of a thin section of this typical gabbro. 

 Similar gabbro outcrops in considerable force near the extreme 

 southwestern end of the area, and also on the ridge along the 

 eastern side of the area. 



The Cheney pond stock is the second largest. It covers nearly 

 3 square miles. There are many good exposures. Most of this 

 gabbro is very typical in every way, being medium to moderately 

 coarse grained, nonfoliated, and possesses a diabasic texture. No. 42 

 of table 4 shows the minerals contained in a thin section. Good 

 exposures of the amphibolitic border facies occur along the south- 

 ern border between the pond and the old road, on the little island 

 in the pond, and where the river enters the pond. In a field a few 

 rods south of where the river enters the pond, a sharply defined 

 8-inch inclusion of typical Whiteface anorthosite occurs in the 

 gneissoid gabbro. A body of granite large enough to be mapped 

 occurs as an inclusion in the gabbro i^ miles northeast of the 

 Lester dam. Whether or not the gabbro near this inclusion is 

 more acidic than usual was not determined. 



The large stock partly shown within the map limits northwest 

 of Cheney pond is mostly very typical gabbro with considerable 

 amphibolite developed as a border facies. In a field a few rods 

 north of the house ('where the trail leads off) there are some very 

 interesting ledges showing amphibolitic gabbro and Whiteface 

 anorthosite rather intimately associated. 



A number of good exposures show the gabbro of the stock about 

 a mile southeast of Minerva to be mostly medium grained and 

 massive with only poor development of diabasic texture. Locally 



