﻿Vol. 64.] THE LAURENTIAN SYSTEM IN EASTERN CANADA, 129 



The work of Prof. Lawson in tlie Lake-Superior region, which is 

 from 800 to 1000 miles farther west on the margin of the Laurentian 

 protaxis, has shown that in that region there are great bodies of 

 orthoclase-gneiss which form the base of the geological column, and 

 are, therefore, in position the equivalent of the Fundamental Gneiss 

 of Logan. This gneiss, as Prof. Lawson has shown, cuts up through 

 the oldest sedimentary series in that region, namely, the Keewatin, 

 in the form of bathyliths. The stratigraphical succession in that 

 western district, however, is entirely different from the succession in 

 the eastern portion of Canada where Logan's original Laurentian 

 area is situated. Neither the Grenville nor the Hastings Series occurs 

 there. It became evident, therefore, that if a satisfactory knowledge 

 of the character, structure, relations, and origin of Logan's Laurentian 

 succession in Eastern Canada was to be obtained, this could only be 

 secured by selecting some large area of these rocks and mapping 

 it in much greater detail than had been previously attempted, the 

 mapping being accompanied by a thorough petrographical study of 

 the various rock-types that occur in the area, employing in this 

 study all the varied resources of modern petrography. The most 

 suitable area in the Dominion for this purpose was that embraced 

 by Sheet 118 (Haliburton sheet), of the Ontario and Quebec 

 series of geological maps which are being issued by the Geological 

 Survey of Canada. This lies near the border of the Laurentian 

 protaxis, north of Lake Ontario and east of Lake Huron. 



The writer, in conjunction with Dr. A. E. Barlow, of the Geological 

 Survey of Canada, was accordingly instructed by the late Dr. G. M. 

 Dawson, then Director of the Geological Survey, to make a detailed 

 study of this area, which was a virgin field, no geological examination 

 of it having been previously undertaken. 



As the mapping progressed, it seemed best to extend the work 

 to the south-east, beyond the limits of the Haliburton sheet. Two 

 maps were accordingly prepared, one, consisting of the Haliburton 

 sheet, forming part of the regular series of geological maps above 

 mentioned — this being prepared on the scale of 4 miles to the 

 inch, — and the other embracing the south-eastern portion of this 

 sheet together with the district lying to the south-east of it, which 

 was designated as the Bancroft sheet. These together represent 

 an area of 4200 square miles. This second map, embracing as it 

 does an area of much greater complexity, and one which affords a 

 key to the geology of the rest of the district, was prepared on the 

 scale of 2 miles to the inch. It comprises an area of 1955 square 

 miles. A copy of the Bancroft sheet (PI. XIII) accompanies this 

 paper. The sketch-map (fig. 1, p. 128) shows the respective position 

 of these areas. 



The field-work occupied a period of eight years, audit is proposed 

 in the present paper to outline very briefly the chief results obtained : 

 reserving the presentation of the detailed studies made upon the 

 nepheline-syenites of the area with their associated corundum- 

 deposits, the genetic relations of the amphibolites, and certain 

 other points, for a series of papers by Dr. Barlow and myself which 



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