1916] Lawson: Correlation of Pre-Cambrian Rocks 11 



It thus seems pretty certain that the territory extending from Lake 

 Huron to Lake Temiskaming, and including the Lake Huron, Sud- 

 bury, and Cobalt districts, suffered granite invasion at two widely 

 spaced periods. These two periods of granitic invasion separate the 

 sequence of epigene rocks throughout these three districts into three 

 parts, precisely in the same way as the two granites on the south side 

 of Lake Superior do, and it seems probable that they are chronological 

 equivalents each to each. 



If this be true, then it follows that the Temiskamian and Bruce 

 series both fall into the middle of the three great divisions of time, 

 that is, they were deposited in the period between the degradation of 

 the Laurentian and the invasion of the region by the Killarney or 

 Lorrain granite. The relations of the Temiskamian to the Bruce series 

 have not yet been satisfactorily established, but it seems probable that 

 the Bruce series is the equivalent of the Sturgeon quartzite and Kona 

 dolomite, etc., of the south side of Lake Superior ; while it is equally 

 probable that the Temiskamian is the equivalent of the group of 

 variously named formations on the south side comprising the Tyler 

 and Hanbury slate, the Ironwood, Negaumee, and V ulcan iron forma- 

 tion, the Palms and Ajibik formations, etc., and therefore the correla- 

 tive of the Seine Series on the northwest side of Lake Superior. The 

 Cobalt Series appears then with little question to be the equivalent of 

 the Copps, Michigamme, etc., on the south side and of the Animikian 

 of the northwest side. 



Southeastern Ontario and Adirondacks. — In Southeastern Ontario 

 there is an older granite gneiss, the Laurentian, cutting the Keewatin 

 and Grenville series, and a later, Moira, cutting the Hastings series, 

 which rests upon the eroded surface of the Laurentian. These two 

 granites, by the hypothesis here advanced, are the respective chrono- 

 logical equivalents of the two granites on the north shore of Lake 

 Huron, on the south side of Lake Superior and on the northwest side ; 

 and the Hastings series is either the correlative of the Temiskamian, 

 as Miller and Knight assert, as well as of the Tyler-Hanbury-Palms- 

 Siamo-Ajibik, etc., and of the Seine ; or the correlative of the Bruce 

 series. 



In the Adirondacks, according to Gushing, 8 there are two granites 

 of widely different ages, the Laurentian intrusive in the Grenville, and 

 the Pieton, itself undeformed, cutting the Laurentian after the de- 

 formation of the latter. 



» Am. Journ. Sci., vol 39, pp. 288-294, March, 1915. 



