GEOLOGY OF THE POUGHKEEPSIE QUADRANGLE 27 



the degree of chloritization of the mica. It is without evidence of 

 bedding. This rock grades in places at the south into a laminated 

 finer-grained variety v^^hich is common in the gorge of the creek 

 below the railroad bridge at Glenham. At the north this type is 

 more abundant, outcropping frequently between the road from Fish- 

 kill Village to Wappinger Falls and Vly mountain. 



Vly mountain is composed of this variety. It grades into the 

 coarser rock and, like the latter, is usually chloritized, though the 

 red color of the iron usually predominates. The laminations strike 

 between n. 12° e. and n. 15° e. As was noted in the petrographic 

 description of this gneiss, it occasionally passes into a rock com- 

 posed only of feldspar and quartz. 



The varieties so far described make up the surface rock of the 

 Glenham belt and are the ones which have been emphasized by 

 most observers. 



The road from Fishkill Village to Wappinger Falls crosses the 

 Glenham belt diagonally about midway of its length. Several shal- 

 low cuts have been made in the gneisses along the road. Beginning 

 at the first cut on the south, the section is through about one hun- 

 dred feet of a coarse, granitic hybrid rock. This is followed b}^ 

 hornblende gneiss and at the top of the hill the latter is succeeded 

 by a banded, slightly crinkled gneiss with pinkish red and dark green 

 laminae. A hundred yards beyond to the north of this rock on the 

 west side of the road is a massive, coarse granitoid gneiss with 

 quartz, light colored feldspar and biotite as the chief minerals. The 

 joints in this rock are filled or faced with epidote. Beyond this is 

 a fine-grained pinkish rock carrying epidote in many places and 

 very similar in essential mineralogy to that described in the Mount 

 Beacon brook section as composing the wall of the gorge above the 

 bridge. Beyond this the cut is for some distance through medium- 

 grained hornblende gneiss exposed on both sides of the road. The 

 last section, on the east side of the road, is mainly through this 

 hornblende rock which shows slight variations and fairly distinct 

 " bedding," with a southeast dip. 



These gneisses of the Glenham belt show no distinct types, except 

 as described above for the surface exposures. On the other hand, 

 the hornblende and other gneisses show marked resemblance to the 

 mountain rocks. Roughly correcting the section for the gradient, 

 the bearing of the road and the angle of dip, which seems a little 

 smaller than that of the mountain gneisses, the thickness of the 

 gneissoid types is similar to those observed in the gneisses of the 

 spurs. 



