THE HASTINGS DISTRICT d 



by Vennor. Here the sedimentary rocks are in vastly greater volnmc 

 and the metamorphism of large areas is much less advanced than in the 

 original Laurentian district. The later studies of Adams led him to the 

 conclusion that there are gradations between the moderately metamor- 

 phosed sedimentary rocks, in which limestone is the greatest formation, 

 to the intensely metamorphosed varieties, which are like those of the 

 original Laurentian area, and he concluded that the Grenville and 

 Hastings series are one. 



A committee representing the United States and Canadian geological 

 surveys, consisting of Messrs Adams, Barlow, Coleman, Cushing, Kemp, 

 and Van Hise, accepted Adams' conclusions and agreed to extend the 

 term Grenville, previously applied in the Laurentian district only, to the 

 similar formations in the Hastings and Adirondack districts. In the 

 report of this committee the term Laurentian was restricted to the acid 

 gneissic and granitic rocks, many of which are intrusive into tlie sedi- 

 mentary series, in accordance with the usage recognized in tlie report of 

 the committee upon the Lake Superior region, to be mentioned later- 

 (see page 12). 



The report of the committee showed that there is in the Madoc area 

 of the Hastings district a series of rocks, consisting largely of conglom- 

 erates, felsites, slates, and schists, which rest unconformably upon a 

 limestone-hearing series. The existence of a physical break in the sedi- 

 mentary series was thus recognized, but its importance and the position 

 of the upper series were left undetermined. The last word upon tliis 

 district is l)y Miller and Knight,^ who hold that they have proved that — 



"much, at least, of what has heeu called the Hastings series, consisting of 

 limestones, conglomerate, and other fragniental rocks, is much younger than, 

 and forms a well defined unconformable series with, the t.vpical crystalline 

 limestones and associated fragmental rocks of what has been called the Gren- 

 ville series proper. The view that the Grenville and Hastings constitute one 

 series, the former being a more highly altered phase of the latter, is no longer 

 tenable." 



Miller and Knight also think that in places they have found tlie Kee- 

 watin lava floor on which the Grenville series has been deposited. Ac- 

 cording to them. 



^ Report of a special committee on tlie correlation of the pre-Cambrian rocks of the 

 Adirondack mountains, the "Original Laurentian area" of Canada and eastern Ontario, 

 by Messrs F. D. Adams, A. E. Barlow, A. 1'. Coleman, H. P. Cushing, J. F. Kemp, and 

 C. R. Van Hise. Journal of Geology, vol. 15, 1907, pp. 191-217. 



3 Grenville-Hastings unconformity and the probable identity in age of the Grenville 

 limestone with the Keewatin iron formation of the Lake Superior region, by Willot G. 

 Miller and Cyril W. Knight. Sixteenth Report, Bureau of Mines, Ontario, 1907, pp. 

 221-223. 



