ELIZABETHTOWN AND PORT HENRY QUADRANGLES 87 



It extends a short distance to the northwest and has an eruptive 

 contact with the anorthosite, fragments of which it incloses. Its 

 contacts with the syenite near New pond are not sharply defined. 

 • Areal distribution of the Woolen Mill type. The most ac- 

 cessible locality of this type is in the bed of the Branch, about a 

 mile west of Elizabethtown but the same rock runs to the west- 

 ward, where it appears in the rather few exposures along the brook 

 itself. It also constitutes the marked ridge which lies between the 

 two Grenville areas at the northern edge of the map. It forms the 

 summit of Cobble hill, and appears well down its flanks. The blue 

 knots or augen of labradorite occasionally appear and serve to 

 identify it. 



The same rock has a flne development in Blueberry mountain 

 along the southern edge of the sheet, where once again the blue 

 labradorite knots appear in the basic gneissoid rock. 



Areal distribution of the New Pond type. This interesting 

 rock is much less abundant than the others just mentioned. Only 

 the exposure along the road to New pond has been discovered ex- 

 cept for loose boulders to the south and except for possible gneisses 

 derived from it by shearing. 



Areal distribution of the syenites. The chief area of the 

 syenitic series is in the southeastern portion of the area, but a 

 few scattered exposures have been noted in outlying portions to the 

 northwest, which although not sharply marked are believed to be 

 intrusive in their nature. 



The syenites are believed to constitute a batholith of size cover- 

 ing 50 square miles or more and of irregular outline. Its contacts 

 with the other formations so far as worked out are chiefly faulted 

 ones, syenite on one side of the valley, anorthosite or Grenville on 

 the other. As to the distinction between possible basal gneisses 

 in the Grenville and syenitic members dragged out into gneissoid 

 forms, the matter is difficult. Tlie syenites are believed to be the 

 chief wall rocks of the iron ores. 



Areal distribution of the basic gabbros. Within the area of 

 the present map there are 25 to 30 known exposures of the basic 

 gabbros, the greater number of which are small. They can rarely 

 be identified as actual dikes. They must be usually mapped without 

 definite or characteristic shape, either from limited exposures, or 

 because the outcrop actually presents the form of an irregular boss 

 or knob. The largest area covers 3 or 4 square miles and lies east 

 of Little pond which is itself southeast of Elizabethtown. The 

 gabbro mass contains several bodies of titaniferous magnetite. Two 



