74 



NEW YORK STATE MUSEUM 



are usually lenslike or elliptical in ground plan and essentially 

 parallel to the foliation of the inclosing rocks. 



Figure 8 shows an interesting case of a sharply bent small mass 

 of Grenville gneiss in granite on Ledge hill. 



Foliation of the Intrusive Rocks 



The anorthosite and syenite-granite series. The great instru- 

 sives of the quadrangle, including both the anorthosite and the 

 syenite-granite series, exhibit more or less foliation, though large 



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Fig. 8 Sketch showing ground plan of part of an exposure near the east- 

 ern border of the gabbro stock on Ledge hill. The gneissoid granite, with its 

 sharply curving foliation, wraps about a portion of a sharply bent small 

 inclusion of hornblende gneiss. 



portions of the Marcy anorthosite commonly show practically none. 

 In the syenite-granite series at least a faint foliation seldom fails 

 to appear, and it varies from this to very highly foliated. The 

 degree of foliation often varies notably within very short dis- 

 tances. Both strike and dip of the foliation also often vary notably, 

 though the general trend or strike is from east-west to northwest- 

 southeast. Regarding the foliation in the adjoining Paradox Lake 

 quadrangle, Doctor Ogilvie says : " The general direction of strike 

 is similar. A direction of N 40 E is the prevailing one, with low 

 southeast dips." According to this, the general strike of foliation 

 of the Schroon Lake quadrangle is almost at right angles to that 

 of the Paradox Lake quadrangle. In many ledges the general strike 



