420 C. K. LEITH 



Lake and the Churchill River in Canada. The area covered by the 

 report is bounded on the south by the Churchill and Clearwater rivers ; 

 on the west by the lower portion of the Athabasca River ; on the north 

 by Athabasca Lake, Stone River, with its expansions, Black and Hatchet 

 lakes, Wollaston Lake, and Cochrane or Ice River ; on the east by the 

 lower part of the Cochrane River, Reindeer Lake, and Reindeer River. 



Laurentian rocks, including hornblende-granites, biotite granites, 

 muscovite granites, granitoid gneisses, gabbros, and norites, are found 

 outcropping on the Churchill River from two miles below the mouth 

 of the Mudjatick River eastward to the mouth of the Reindeer River ; 

 thence northward they occupy most of the eastern part of the district. 

 Further west they are followed north to Cree Lake. In the northern 

 part of the area they occupy most of the northern shores of Athabasca 

 and Black lakes. 



As far as at present known, the Huronian is represented in this 

 district solely by three small areas on the north shore of Lake Atha- 

 basca. The Huronian here includes quartzites, calcareous sandstones 

 and schists, conglomerate, halleflinta, ferruginous chlorite-schists, and 

 other green schists. 



The Laurentian and Huronian are unconformably overlain by 

 horizontal sandstones and conglomerates, called the Athabasca sand- 

 stone, which is placed in the Cambrian. However, these sandstones 

 are similar to the sandstones found to the north associated with 

 quartz-porphyries, diabases, etc., like those of the Keweenawan of 

 Lake Superior, and there is little doubt that the two sets of rocks 

 belong to the same horizon. 



Tyrrell 1 reports on an exploration of the Doobaunt, Kazan, and Fer- 

 guson rivers northwest of Hudson Bay, the northwest coast of Hudson 

 Bay, and on two overland routes from Hudson Bay to Lake Winnipeg. 



Laurentian rocks, including granites, diorites, and granite and 

 diorite gneisses, occupy a large part of the region crossed by the 

 three main lines of travel — the Doobaunt River and Chesterfield Inlet, 

 the Kazan and Ferguson rivers, and the west coast of Hudson Bay, — 

 although their precise extent is unknown. 



The Huronian rocks include three more or less distinct groups, the 

 Marble Island quartzites, the greenish quartzites and graywackes, and 



1 Report on the Doobaunt, Kazan, and Ferguson rivers, and on the northwest 

 coast of Hudson Bay, by J. B. Tyrrell : Ann. Rep. Geol. Surv. of Canada, Vol. IX, 

 1898, Part F, pp. 218. With geol. maps. 



