REVIEWS 447 



Falls. From this point to the Lobstick portage, Laurentian gneisses 

 and inica schists crop out occasionally. The narrow Huronian belt 

 from the Lobstick to the foot of the canyon or Long Portage, consists 

 mainly of augite-syenite, passing into gabbro to the north. Beyond 

 this portage Laurentian gneiss extends to the Devonian contact above 

 the Sextant rapids. 



Coleman' gives a general account of a visit to all the iron and 

 copper regions of the Lake Superior country. For the ranges on the 

 United States side of the boundary no facts are given not found in the 

 published reports. On the Canadian side of the boundary the Michi- 

 picoten Range, the iron formation near Dog River, and the siliceous 

 iron ores of Batchavvana Bay are described. In the Michipicoten 

 range the Helen mine in particular is referred to. In general, the rocks, 

 including the ore at this mine, have all the appearance of Lower 

 Huronian or Keewatin rocks, as in the Vermilion district, and not 

 those of the Upper Huronian or Animikie, as in the Mesaba. 



Near Dog River are iron formation rocks similar to those extend- 

 ing northeast from Michipicoten bay. It is thought probable that 

 the two may connect. 



The occurrence and relations of iron formation material northeast 

 from Michipicoten Bay and near Dog River are indicated on a sketch 

 map. 



Coleman,- as a result of an examination of the new Michipicoten 

 iron district, and the consideration of other iron formation areas in 

 Ontario, has collected facts which seem to throw some light on the 

 relative ages of the different areas mapped as Huronian on the north 

 shore. In the Michipicoten district iron -formation material, consist- 

 ing of banded ferruginous sandstones, cherts, and jaspers, standing 

 nearly vertical, extends from Little Gros Cap northeastward for twenty 

 miles; then bending to the north and west it takes a westerly direction 

 for more than thirty miles. The width of the belt is but a few hun- 

 dred yards. 



Sandstones of the same peculiar type occur at Little Turtle Lake, 

 east of Rainy Lake and near Fort Frances, on Rainy River, as well as 

 at the Scramble gold mine, near Rat Portage, on Lake of the Woods. 



'Coleman, Dr. A. P.: Copper and Iron Regions of Ontario, bv A. P. 

 Coleman. Report of the Ontario Bureau of Mines for 1900, pp. 143-191. 



^ Upper and Lower Huronian in Ontario, by Arthur P. Coleman : Bull. Geol. 

 *Soc. Am., Vol. II, 1900, pp. 107-114. 



