REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1900 rSl 



that the rocks of both areas were deposited in the same basin and 

 are parte of the same great, conformable series. The writer is 

 therefore strongly of the opinion that at present no necessity 

 exists for a local name for the Adirondack rocks, and none will 

 exist till the stratigraphy of the series has been so thoroughly 

 worked out that some more rejfined basis of comparison is avail- 

 able and shows its desirability. 



In addition to the Grenville rocks, the pre^Oambrian of that 

 part of Canada which lies north of the Adirondack region com- 

 prises certain gneisses of doubtful age and origin, and certain 

 later eruptives, and the rocks of each class would seem to corres- 

 pond precisely to the Adirondack rocks. In Dr F. D. Adams's 

 report on the region north of the island of Montreal, the gneisses 

 are largely classed as belonging with the Grenville series, though 

 certain portions are separated as of possible earlier age and 

 hence to be perhaps classed with the fundamental gneis-s.^ But 

 on the map accompanying the report all appear a® one formation^ 

 from which the limestone bands alone are separated and given 

 another color, the separation being therefore a purely lithologic 

 one. The quartzite, sillimanite and graphite gneisses of probable 

 sedimentary origin are mapped in with the main body of uncertain 

 gneiss, the iseparation of the limestone being simply aei an aid 

 in interpreting the structure of the district. The gneisses are 

 more widespread and the later eruptives apparently less so than 

 in the Adirondacks. Because of the impossibility of making any 

 separation between gneisses associated with, and undoubtedly 

 belonging to the Grenville series, and other similar gneisses which 

 occur unmixed with Grenville rocks, and hence of doubtful 

 association, all are mapped as of the same formation. iVdams, 

 however, states distinctly that in other parts of Canada a separa- 

 tion can be made between the Grenville and the fundamental 

 gneiss. These difficulties are precisely those encountered in the 

 Adirondacks. Closely interbanded with the limestones and 

 schists of the Grenville are granitic, gabbroic and other gneisses 

 which seem to represent closely contemporaneous igneous intru- 



* Geol. sur. Can. An. rep't. 1896. v. 8, pt J. 



