1897] Ells— Recent Conclusions in Quebec Geology. 173 

 RECENT CONCLUSIONS IN QUEBEC GEOLOGY. 



R. W- Ells, LL. D., F. K. S. C, Geological Survey, Ottawa. 

 (Read before Section C, British Association Meeting, Toronto, Canada, 1897.) 



The paper gives a brief outline of the progress of geological 

 exploration in this portion of the Dominion, with a statement of 

 the most recent conclusions arrived at as the result of the 

 detailed study of the rocks in the field. It is largely a summary 

 of the conclusions stated in the published report of the Geological 

 Survey of Canada,* on this district. 



The principal problems west of the St. Lawrence were the 

 relations of the great Anorthosite masses, lying to the north of 

 Montreal, to the Laurentian Fundamental Gneiss and the Gren- 

 ville Series ; and secondly, the relations of the Grenville Series 

 itself to the underlying Gneiss on the one hand and to the 

 Hastings Series of Ontario on the other. 



These may now be regarded as fairly well settled, at least 

 to the satisfaction of those who have most recently worked in 

 this field. In regard to the age of the Anorthosites the old con- 

 tention that these were an altered series of the sedimentary rocks, 

 resting unconformably on the gneiss and limestone of the 

 Grenville series, has been abandoned. It has been found that 

 the Anorthosites and Gabbros which are associated with these, 

 are igneous in character, and that they are newer, in point of 

 time, than the Grenville rocks ; that they have invaded these at 

 many points and altered them along the lines of contact. 



The change of view in regard to their origin dates back 

 to about 1879-80, and their igneous intrusive character was first 

 pointed out by Vennor nearly twenty years ago. This view was 

 expounded by Dr. Selwyn in the report forthe years mentioned,but 

 the whole question has more recently been investigated, principally 

 by Dr. F. D. Adams, whose observations in the field and in the 

 laboratory have finally conclusively settled the problem and shewn 

 that the anorthosite areas are masses of igneous rocks newer than 

 the Grenville limestone and associated gneisses. 



The second grand problem as to the relations of the Gren- 

 ville limestone and associated rusty and hornblende gneisses to 

 the Fundamental Gneiss of the Laurentian proper, has also 

 been conclusively settled. It is now held by all the recent ob- 

 servers in this field that the rocks of this division are a newer 



* Annual Report, Vol. VII, N. Series, 1894, Part J. 



