398 PROCEEDINGS OF WASHINGTON MEETING. 



Reconvening at 2 p m, the first paper, read by the senior author^was 

 entitled — 



ORIGIN AND RELATIONS OF THE GRENVILLE-HASTINGS SERIES OF THE 



CANADIAN LA URENTIAN 



BY FRANK D. ADAMS AND ALFRED E. BARLOW 



{Abstract] 



Contents 



Page 



Resum6 of former results 398 



Recent and present investigations 398 



Present views concerning Laurentian system 398 



Divisions and their general characteristics 398 



Fundamental gneiss 399 



Grenville series 399 



Relations of Fundamental gneiss and Hastings and Grenville series 399 



Age of the Hastings series 401 



Tentative conclusions 401 



Resume of former Results 



In a former paper,* which appeared in 1893, it was shown that Logan's " Upper 

 Laurentian " does not exist as an independent geological series, the anorthosites, 

 which were considered as constituting its main feature, being in reality great in- 

 trusive or batholitic masses, and in a subsequent paper f it was shown that in the 

 remaining portion of the Laurentian two distinct classes of rocks could be distin- 

 guished, the first being beyond all doubt igneous rocks, and the second consisting 

 of highly altered rocks of aqueous origin. In addition to these two classes, whose 

 origin could be recognized, there remained a third class whose origin was doubtful. 



Recent and present Investigations 



Since the appearance of these papers the present writers have been working 

 together in mapping a large area (3,456 square miles) of the Laurentian in central 

 Ontario, in a district especially well suited for purposes of study. Portions of three 

 summers have already been spent in the district, and, as two years more must 

 probably elapse before the work can be completed, it is desired here to present a 

 general outline of the results so far obtained, indicating certain conclusions which 

 seem likely to be reached concerning the origin of the rocks in question. 



Present Views concerning Laurentian System 



DIVISIONS AND THEIR GENERAL CHARACTERISTICS 



The Laurentian system in Canada is now recognized as consisting of two series 

 of rocks, known respectively as the Fundamental gneiss and the Grenville series. 



*F. D.Adams: Ueber das Norian oder Ober Laurentian von Canada. Neues Jahrbuch fur 

 Mineralogie, Beil. Bd. viii. 



f F. D. Adams: A Further Contribution to our Knowledge of the Laurentian. Am. Jour. Sci., 

 July, 1895. 



