No. 2.J SPENCER — COPPER-BEARING ROCKS. 63 



On the north shore of Lake Superior, the Nippon or Copper- 

 Bearing Series is represented by a similar intercalation of igneous 

 and sedimentary rocks. These deposits are divided by the Ca- 

 nadian Geological Survey into two groups which :ire not con- 

 fonuiible. The Lower Group, called by Hunt the Animikie, 

 is somewhat different lithologically from the lower members of 

 the series on the South Shore, as it is largely composed of con- 

 glomer.tes, cherty layers, some dolomites, and missive blick 

 shales with occasion tl beds of trap. In some of the beds car- 

 bonaceous matter has been found. The Upper Group cont .ins 

 some dolomites and limestones which are not present, on Kewee- 

 naw Point. The Lower Group of the Canadian geologists 

 occurs principally to the north-west of Lake Superior, while the 

 Upper Division lies to the north and enst of the lake. According 

 to the measurements of Bell and Macfarl me, in different places, 

 the Nipigon or Cupriferous Series, on the Canadian side of Lake 

 Superior, attains a thickness of i3,00(i t0 16,000 feet, including 

 upwards of 2.0C0 feet of conulonier.tes. In the Nipigon Basin 

 this format-inn attains its greatest thickness about the middle and 

 southern portions, while to the northward it thins out. The trend 

 is northerly. The deposits are sometimes nearly horizontal, 

 and seldom is the dip greater than 15-20 degrees, although in some 

 places the strata are thrown up at high angles. Thundtr C pe 

 and very many of the hills on Nipigon, Bl ick. and Thunder B iys, 

 are capped by thick deposits of trappean rocks, which are de- 

 posited almost horizontally, resting unconformable on either the 

 Lower or theUpper Group of the Copper-bearing or Nipigon Series 

 The wrinkled structure of the trap rocks indicates the different 

 directions of the igneous overflows. The material of these erup- 

 tions, according to Bell, hid a north-westerly direction on Thun- 

 der Bay. while on I>le St. Ignace they "were to the north-eastward^ 

 and to the east of the lake Sir William Logan showed them to> 

 have had an easterly direction. Everywhere, on leaving the 

 great lake ba-in, the Nipigon deposits thin out. Numerous trap 

 dykes traverse this formation on the North Shore, but on the 

 south side of the lake they do not appear to p;ss higher than the 

 Huronian Series, while the veins are filled with metamorphosed 

 aqueous infiltrations, or with the debris of the adjacent rocks. 



Both on the north and south shores of Lake Superior, the 

 beds of the Nipigon Formation are considerably f.ulted. Be- 

 tween the Phoenix and Central Mines ou Keweemiw Point, there 



