298 



MINERALS AND GEOLOGY 



Fio. 242. 



The dotted line in this diagram 

 indicates the level below which the 

 rocks are concealed. 



The stratigraphical relations of the two 

 series, Laurentian and Huronian, in this 

 district, have not yet been clearly made 

 out. The mineral characteristics, and 

 especially the presence of conglomerates 

 holding gneissoid and other fragments, 

 lead undoubtedly to the conclusion that 

 the Huronian beds are of later formation 

 than the Laurentian; but, as pointed out by Dr. Selwyn, the Huronian 

 appear in many places to pass under the latter. This can only be 

 explained by the assumption of great overturned or reversed dips* 

 as shewn roughly in fig. 242. 



As regards distribution, whilst the Laurentian rocks cover perhaps 

 the greater portion of the district now under description, large areas 

 within it are occupied by Huronian beds. The latter form essen- 

 tially a series of wide bands ranging in a north-east and south-west 

 direction. The largest perhaps of these Huronian areas lies immedi- 

 ately west and south-west of Lake Temiscammgue, extending in the 

 latter direction to near Killarney on Georgian Bay, and along the 

 north shore of Lake Huron and the back country to beyond Goulais 

 Bay in the south-east angle of Lake Superior. This area is traversed 

 for about miles by the Canadian Pacific Railway, from the Wah- 

 nahpitae River, by Sudbury, to Spanish Forks, where Laurentian 

 rocks come up ; and fine sections may be seen in the railway cuttings, 

 especially in the vicinity of Sudbury Junction, and westward, where 

 large deposits of copper ore occur. The copper pyrites of Eagle Lake 

 (near Lake Huron) and that of the Bruce Mines, now apparently 

 exhausted, occur in quartz veins traversing the same Huronian for- 

 mation. About Sudbury and along the branch line to the Algoma 

 Mills on Georgian Bay the Huronian quartzites and conglomerates 

 are broken through by many dykes and erruptive masses of diorite 

 and syenite. Another Huronian area of considerable size extends 

 around Michipicoten Harbour, and along Michipicoten, Magpie and 

 Dog Rivers, for some distance inland. Here the rocks are more or 

 less ferruginous, and are broken through by some large granitic 

 masses. Huronian beds occur also further west on Lake Superior 

 along the course of Pic River. And again, with granitic intrusions, 

 in the back country between Black Bay and the International boun- 



