19 



INTERIOR OF THE NICKEL BASIN. 



The next rock in position is the great laccolithic sheet of 

 the nickel-bearing eruptive, which is bent into a boat-shaped 

 syncline, 17 miles wide and 36 miles long, from southwest 

 to northeast, with the square end of the boat at the latter 

 end. As the sheet is really much later in age than the over- 

 lying beds, the sedimentary rocks enclosed in it will be 

 described first. They were considered Cambrian by Dr. 

 Robert Bell, but no fossils have been found in them, and 



Onaping- Falls over vitrophyre tuff. 



petrographically they somewhat resemble the western Ani- 

 mikie (Upper Huronian), so that it seems better to class 

 them with the Upper Huronian, though their age cannot be 

 certainly fixed at present. 



There are four subdivisions exposed in very regular suc- 

 cession in the interior of the basin, the Trout Lake conglom- 

 erate on the outside resting directly on the upper part of the 

 eruptive sheet, followed by the Onaping tuff, which forms 

 an inner and wider belt; and then by the Onwatin slate; 

 while the Chelmsford sandstone runs down the centre of 

 the basin. 



The conglomerate is coarse textured and has generally 

 been greatly metamorphosed by the underlying eruptive 



