6i 



In the Porcupine gold area, one hundred miles to the 

 northwest of Cobalt, the Keewatin and Temiskaming series 

 are prominent. The Cobalt series is also present in this 

 area, and certain dikes are believed to represent the Nipis- 

 sing diabase of Cobalt. 



In the Gowganda silver-cobalt area, which lies fifty or 

 sixty miles to the west of Cobalt, the Nipissing diabase and 

 Cobalt series occupy much of the surface. The Temiskam- 

 ing series is found in good exposures in part of the area. 

 The latter series has also been found at Swastika and 

 Larder lake, at Abitibi lake, 75 miles north of Cobalt, and 

 eastward across the boundary in Quebec. It is thus known 

 to occur at various points over a large region. 



It is possible that unconformities that have not been dis- 

 covered exist in the pre-Cambrian of the Cobalt and adjacent 

 areas. Moreover, the relationship which the Cobalt and 

 Temiskaming series have to the fragmental rocks of the 

 classic Huronian area of the north shore of Lake Huron is 

 not known. Hence, in the following table the name Huron- 

 ian is not employed. If the Huronian is considered to 

 include all the post-Laurentian and pre-Keweenawan frag- 

 mental rocks of the region, then both the Cobalt and Tem- 

 iskaming series come under this heading. 



The dual subdivision of the pre-Cambrian into Algonkian 

 and Archean, or Proterozoic and Archeozoic, employed by 

 many authors, is not adopted by the writer, since he believes 

 that the Grenville series, which includes limestones and other 

 sediments of great thickness, is of pre-Laurentian age. 

 Thus a dual subdivision of pre-Cambrian rocks, based on 

 arguments that have been employed in its behalf, fails. If 

 a name is desired for the pre-Cambrian rocks, to correspond 

 with Paleozoic and Mesozoic, the well-known name Eozoic 

 mav be used. 



