GEOLOGICAL AREAS OF CANADA. 17 



Superior country, described, under the District of tlie Upper Lakes, 

 in the geology of Ontario. It includes all the country lying between 

 the boundary-line of Ontario (not yet definitely settled), and the 

 Winnipeg River and Lake, with probably a wider extension of area 

 towards the north-west. It is occupied essentially by Laurentian 

 strata of micaceous and syenitic gneiss, quai'tzite, &c., with over- 

 lying belts, in various places, of micaceous, chloritic, and hornblendic 

 slates, and slaty conglomerates, of Huronian age. These Crystalline 

 strata form the surface in many parts, but in others, and especially 

 on the south-east shore of Lake Winnipeg, they are covered by thick 

 deposits of Glacial and Post-Glacial clays and sands. The average 

 altitude of the district is about 1,200 feet — the ground rising in 

 places to 1,500 or 1,600 feet above the sea, but descending to 710 

 feet at Lake Winnipeg. 



(2.) The Eastern Prarie, or Lake Manitoba District. — This sub- 

 division comprises the country immediately west of Lake Winnipeg, 

 Deer Lake, Lake Arthabasca, &c., and the entire area around Lake 

 Manitoba, Lake Winnipegosis and connected series of lakes, with 

 the valley of Red River and the lower courses of the Assiniboine, 

 Swan River, and Saskatchewan. It forms essentially the " First 

 Prairie Steppe" of the north-west, and occupies an elevation of about 

 750 or 800 feet above the sea, stretching to the base of the second 

 prairie along the line of hilly country defined by the Pembina, 

 Riding, Duck, and Porcupine Mountains and the Basquia Hills. It 

 is underlaid in its more eastern portion (including Fort Garry, the 

 lower coxirse of Red River, the western shores of Lake Winnipeg, 

 Cedar Lake, &c.) by Lower Silurian strata belonging essentially, if 

 not wholly, to the Trenton formation, and consisting chiefly ot 

 dolomitic limestones in horizontal or nearly horizontal beds. The 

 more western and north-western portion (including Lake Manitoba, 

 Dauphin Lake, the west shore of Lake Winnipegosis, Swan Lake, 

 &c.) is underlaid by Devonian strata, consisting most probably of 

 the higher portion of the series. Numerous brine springs, and, here 

 and there, outflows of petroleum, appear to mark the Devonian ai-ea 

 generally ; but the surface of the district is almost entir-ely covered 

 by Glacial and Post-Glacial deposits, mostly in the form of stratified 

 marly clays. 



(3.) The Genti'al Prairie District. — This is essentially a prairie 

 region, but interspersed with patches of woodland, and forming on 

 the whole a rolling and often hilly country. It comprises the second 

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