CONGLOMERATES NEAR RAINY LAKE 111 



region. The conglomerate was formed, then, at a far later time than the 

 underlying Keewatin schists, since they must have been solid rocks before 

 the eruption of anorthosite, and this very coarse grained plutonic rock 

 must have had time to cool, doubtless at a great depth, and to be deeply 

 eroded before pebbles of it could have been rolled on a seashore and in- 

 corporated in a rock belonging to the upper part of the series.'* This 

 conglomerate is about three miles south of Little Turtle lake, near which 

 iron-bearing sandstone has been found. 



Lawson maps conglomerates of a similar kind on the Minnesota side 

 of Rainy lake, where the river of the same name flows out, and mentions 

 saccharoidal quartz pebbles as occurring in them along with various 

 other kinds of rock.f He also describes a conglomerate at the west end 

 of Schist lake, containing pebbles composed of quartz "in a very fine 

 mosaic aggregate, partly chalcedonic." J Probably these pebbles are of 

 the same character as the iron-bearing sandstone found by myself a mile 

 east of Fort Frances, on Rainy river. Another important belt of con- 

 glomerate containing sandstone and black quartzitic pebbles occurs 

 near Mosher bay, at the east end of Upper Manitou lake, about 25 miles 

 north of Shoal lake.§ From the facts just mentioned it will be seen 

 that conglomerates with sandstone pebbles are widely distributed in the 

 Rainy Lake region. 



Schist conglomerate occurs also at Rat portage, a short distance south- 

 east of the sandstone band found at the Scramble gold mine, but up to 

 the present no pebbles of sandstone have been observed in it, though it 

 is probably of the same age as the conglomerates of the Rainy Lake 

 region, 80 or 100 miles to the southeast. 



The Jaspers of the eastern Huronian 



Turning now to the eastern portion of the province, which includes the 

 typical Huronian north of lake Huron and its extension to lake Temis- 

 caming, no undoubted sandstones have been found, though a silicious 

 rock with narrow bands ^of magnetite, probably the equivalent of the 

 Michipicoton rock, occurs near Batchawana bay, at the southeast end of 

 lake Superior. I am indebted to Mr J. A. Holmes, State Geologist of 

 North Carolina, for this information, which he obtained while examin- 

 ing an iron deposit nine miles inland. Jasper banded with hematite 

 and magnetite is known to occur at two points in the northeastern part 

 of the area, having exactly the same appearance in hand specimens as 



*Jour. Geol., vol. iv, no. 8, 1896, p. 911. 

 fGeoi. Sur. Can., 1887-88, p. 82 F. 

 J Ibid., p. S4 F. 

 I Ont. Bur. Mines, 1897, p. 123. 



