394 J. B. Tyrrell — Geological JSxjjloration — 



11. — Notes on the Pleistocene of the North-West Territories 

 OF Canada, North- West and West op Hudson Bay.^ 



By J. BuRu Tyrrell, M.A., B.Sc, F.G.S. 



IN the extreme northernmost part of Canada, lying between North 

 Latitudes 56° and 68° and West Longitudes 88° and 112°, is an 

 area of about 400,000 square miles, which had up to the past two 

 years remained geologically unexplored. 



In 1892 the Director of the Geological Survey of Canada sent the 

 writer to explore the country north of Churchill River, and south- 

 west of Lake Athabasca ; in 1893 the exploration was continued 

 northward, along the north shore of Athabasca Lake, travelling 

 from the east end of Lake Athabasca across the country in canoes to 

 the west end of Chesterfield Inlet, and thence continuing in canoes 

 along the shores of Hudson Buy almost to Churchill, from which 

 place an overland journey was made to Winnipeg, Manitoba. 



The south-western half of the country traversed in these two 

 summers is more or less thickly covered with coniferous forest, 

 while the north-eastern half is devoid of trees, and is generally 

 covered with stunted grasses or lichens. 



North of Churchill River the country is underlain by red and 

 grey Laurentian granites and gneisses, with a fairly persistent strike 

 in a south-westerly direction. 



South of Lake Athabasca and Black River these Laurentian rocks 

 are overlain by horizontal red sandstones and conglomerates, occa- 

 sionally cut by trap dykes, which probably represent the Kewenawan 

 sandstones of Lake Superior, and are therefore of Cambrian age, 

 though no fossils were found in them. Athabasca, Black, Wollaston, 

 and Cree Lakes lie along the line of contact of these sandstones and 

 the underlying Archeean rocks. 



The north shore of Lake Athabasca is composed of Laurentian 

 gneiss, and Huronian quartzite, conglomerates, and schists, which 

 in one place were found to be associated with a large deposit of 

 bgematite. The country crossed from Lake Athabasca to Doobaunt 

 Lake is underlain by Laurentian gneiss, which, however, is often 

 hidden by extensive deposits of Boulder-clay. 



In one localit}^ a small outline of unaltered fossiliferous Ordovician 

 limestone was found, very similar in character to the white limestone 

 of the Winnipeg Basin. 



On Doobaunt Lake the Kewenawan sandstones and conglomerates 

 were again discovered, and the country lying between this lake and 

 the head of Chesterfield Inlet was found to be largely underlain by 

 these rocks. The north side of Chesterfield Inlet is generally red 

 and grey Laurentian gneiss, while the greater part of the shore of 

 Hudson Bay for 150 miles south of the Inlet is composed of green 

 Huronian schists cut by many quartz veins, and sprinkled through 

 with particles of copper pyrites. 



The whole of this region shows abundant evidence of having 

 been comparatively recently covered with a mantle of ice, and even 



1 Publislied by permission of the Director of the Geological Survey of Canada. 



