OF CENTRAL CANADA PART V. 



299 



dary on Pigeon River. Long belts of Huronian rocks range also 

 towards the north-east from the eastern shore of Lake Nepigon. 

 Still further west, Huronian beds, mostly in the form of hornblendic* 

 chloritic and nacreous schists, with some clay-slates and quartzites, 

 extend around the shores and through the numerous rocky islets of 

 the Lake of the Woods. On the north-east shore and adjacent 

 islands of this lake, especially round Big Stone Bay, gold-bearing- 

 quartz veins have been opened at several localities. Eruptive gran- 

 ites are of common occurrence also throughout this portion, of the 

 Huronian area. 



Lower Cambrian Strata : Animikie and Keweenian Formations : 

 The actual age of these formations is still somewhat uncertain, but 

 they belong most probably to an early Cambrian period. But 

 although of post-Archa3an age, they form part of the great Archaean 

 region of North-western Ontario, and are thus legitimately described 

 with the latter. They were designated originally by Sir William 

 Logan as the " Upper Copper-bearing R.ocks of Lake Superior." 

 Two series or separate formations are recognized. The lower forma- 

 tion, now known as the Animikie formation,* is made up principally 

 of black slates with subordinate stratifications of white, gray and 

 black chert (in places antLracitic), dark gray ferruginous dolomite, 

 occasional layers of altered sandstone, and bands of trappean matter, 

 mostly composed of dark hornblende and greenish white feldspar, 

 and frequently porphyritic. An enormous trappean overflow, with 

 well-marked sub-columnar structure, caps the entire formation, as 

 seen in the bold promontary of Thunder Cape, as well as at McKay's 

 Mountain, and on Pie Island and elsewhere around Thunder Bay. 

 The higher formation, known as the Keweenian (or Keweenian and 

 Nepigon), consists of white and red calcareous sandstones and marls, 

 beds of conglomerate, and numerous interstratified trappean bands, the 

 whole overlaid as in the lower series by a great trappean overflow' 

 These traps or greenstones are more or less compact or fine-granular in 

 texture as regards those which occur west of Thunder Cape and which 

 are thus associated with the Animikie series \ whilst the more east- 

 ern displays, or those connected more especially with the higher 



* The earliest name bestowed on this series was that of the Kaministiquia Formation, 

 in the first edition of this work, published in 1864. The name was derived from the Kaminis- 

 tiquia River of the Thunder Bay country, along the course of which these rocks are princi- 

 pally developed. 



