CURRENT PRE-CAMBRIAN LITERA TURE 205 



region may be separated into (1) a granite-gneiss basal complex, form- 

 ing the basement upon which the Huronian was deposited, and perhaps 

 representing a portion of the original crust of the earth or its down- 

 ward continuation, and (2) later granite and gneiss intrusive in the 

 Huronian, and therefore of Huronian or post-Huronian age. This 

 discrimination has been uniformly made south of Lake Superior, in a 

 number of cases in Canada, and in other parts of North America, and 

 it is believed that it may also be made in this region of western Ontario. 

 If this were done the rocks of the true fundamental complex in this 

 area would occupy perhaps a very small area. Whether such a com- 

 plex may be called Archean, as advocated by the United States geolo- 

 gists, or by some other name, is immaterial. If the term Laurentian 

 be employed, it would need to be redefined to cover the narrower range 

 of rocks, and because of its present wide application, including both 

 the basal complex and later eruptives, some confusion might result. 

 The term Archean has been carefully defined and consistently used 

 by the United States geologists to represent the oldest group of rocks 

 or basal complex, and in this narrow application has priority to any 

 other term. 



The portion of the granites and gneiss intrusive in the Huronian 

 would be called simply Huronian or post-Huronian. If the true basal 

 complex be altogether absent in this region, the granites and gneisses 

 now called Laurentian are of Huronian or post-Huronian age, and are 

 not to be correlated with rocks of the true basal complex of other areas. 



Parks ' describes the geology of the base and meridian lines in the 

 Rainy River district, in an area extending from Lac Seul on the north- 

 west and Lake Wabigoon on the southwest, to Sturgeon Lake and Mat- 

 tawa Lake on the east. Laurentian and Huronian rocks occur in folds 

 with a general northeast-southwest trend. The Huronian rocks occur 

 in three main areas, the Sturgeon River area, the Lake Minnetakie area, 

 and the Wabigoon Lake area. They consist of altered traps, horn- 

 blende-schists and other green schists, altered porphyrites, quartz 

 porphyries, phyllites, and conglomerates. In general they resemble 

 Lawson's Keewatin series to the south. The Laurentian consists of 

 hornblende-syenite, hornblende-granite-gneiss, mica-syenite, biotite- 

 granite-gneiss, and various granitic rocks. C. K. Leith. 



1 Geology of base and meridian lines in the Rainy River district, by W. A. Parks : 

 Rept. Bureau of Mines, Ontario, Vol. VII, 1898, pp. 161—183. With geological map. 



