4 Life-histories of Northern Animals 



In Manitoba the Laurentian area lies to the eastward of 

 Lake Winnipeg and the prairies of the Red River Valley, and 

 its rocks belong to the lower division, or that of the primitive 

 gneiss. They extend eastward a long distance toward Hud- 

 son Bay. In St. Martin's Lake some small islands consist 

 of gneiss, and the same rock has been found, by boring, to 

 underlie the horizontal sedimentary rocks to the southward of 

 Lake Manitoba. The Archaean rocks probably underlie 

 these strata throughout Manitoba, their depth from the surface 

 increasing to the south and west. 



The Laurentian rocks of the province are immediately 

 overlaid to the westward by unaltered and almost horizontal 

 beds of the Ordivician or Cambro-Silurian system. Along 

 the west side of Lake Winnipeg these consist of sandstones at 

 the bottom, overlaid by impure magncsian limestones. Thick- 

 bedded mottled yellowish-gray magnesian limestones of the 

 same horizon are found at East and West Selkirk. At Stoney 

 Mountain fossiliferous limestones occur which are somewhat 

 higher in the series. 



Above the Ordivician rocks, the Devonian system is 

 represented on both sides of Lakes Manitnha and W innipegosis 

 by limestones which are much less magnesian than those of 

 that series. Rocks belonging to nnc or the other of the two 

 systems just mentioned are believed to underlie most of the 

 Red River Valley in Manitoba. At Burnside a boring made 

 by the Canadian Pacific Railway Company in 1874 showed 

 the Devonian at that locality to be King directly upon Lauren- 

 tian gneiss. 



On the second prairie lc\cl, that is, all the Assiniboine 

 prairies west of the escarpment of Pembina, Riding, and Duck 

 Mountain, the Devonian is overlaid by a series of Cretaceous 

 shales that are exposed at many points along the river valleys, 

 as well as on the eastern front of the above-named escarpment. 



On Turtle Mountain we find the Laramie limestones be- 

 tween the Cretaceous shales and the surface deposits or drift. 



The drift is composed of boulder clay, overlaid in places 

 with lake-bottom clay or sometimes delta sand. The clav and 



