58 NEW YORK STATE MUSEljM 



As shown on the map, short faults are suggested at the eastern 

 base of Mill mountain, the western base of Stockton mountain, and 

 the northern base of Wolf pond mountain. Except for some evi- 

 dence of shearing on the side of Stockton mountain, the only evi- 

 dence for these faults is topographic, it being difficult to account 

 for these steep scarps except on the basis of faulting. 



The writer believes it quite likely that other, chiefly minor, faults 

 occur within the quadrangle, but the ones above described are the 

 only ones he feels justified in representing on the geologic map as 

 actually or very probably present. 



FOLIATION 



All the rocks except the diabase and pegmatite show more or less 

 of the foliated structure. It is best seen in the Grenville gneisses 

 which are commonly distinctly banded due to differences in the 

 composition of the beds, the foliation so far as observed always 

 being parallel to the bedding. The syenite, granite, and granite 

 porphyry are always gneissoid but never distinctly banded, the 

 structure being accentuated by a drawing or flattening out of the 

 dark colored minerals parallel to the foliation. The more basic 

 pyroxene and hornblende syenites are, as a rule, not very gneissoid, 

 as, for example, the Bull Rock mountain syenite. In fact it may be 

 stated as a very general rule that the more basic, even and medium 

 grained rocks of the syenite-granite series are least gneissoid ; while 

 the more acid rocks carrying hornblende and some biotite are 

 clearly gneissoid; and the most acid rocks rich in quartz and 

 biotite are very gneissoid. In these last named rocks the very 

 presence of biotite flakes and the tendency of the quartz to be- 

 come flattened favor the development of the foliated structure. 

 Again, it often happens that when members of the great intrusive 

 series, especially the granites, are close to the Grenville the rocks 

 are more gneissoid. Thus, at the top of Heath mountain the pink 

 granite is rather poorly gneissoid while at the base of the mountain 

 it is very gneissoid. 



The typical basic gabbro stocks seldom show a gneissoid struc- 

 ture except rather often in the narrow amphibolite borders. Some 

 of the more acid stocks are clearly gneissoid. 



An interesting feature is the common occurrence of rapid changes 

 in degree of foliation even within the same rock ledge. Thus, just 

 west of The Glen (on the mountain side) there are big ledges of 



