70 THE GLACIAL LAKE AGASSIZ. 



The basal sandstone of these sections is the lowest fomiatiou exposed 

 in this basin above the Archean rocks. It is regarded by Mr. J. B. TyiTell, 

 of the Canadian Geological Survey, who has recently examined the lake 

 region of Manitoba, as of the same age with the Chazy limestone of New 

 York and the St. Peter sandstone of the Upper Mississippi. He reports 

 its thickness to be about 100 feet, consisting of "white quai-tzose sandstone, 

 with generally well-rovmded grains, running down, at the bottom, into a 

 quartzose conglomerate." ^ 



The overlpng limestone, called the Trenton formation by Whiteaves 

 and Tyrrell, appears t(5 represent both the Trenton and Galena formations 

 of the Mississippi Valley. It is described by TyiTell as "consisting at the 

 bottom of a mottled buif and gray dolomitic limestone, found at Big and 

 Swampy islands, etc., and probably also at East Selkirk, above which are 

 other horizontal and evenly bedded limestones and dolomites, amounting in 

 all to a few hundi-ed feet, and all more or less rich in fossils."^ 



Next in ascending order, these authors identify the Hiidson River 

 formation, the highest member of the Lower Silurian system, "represented 

 by less than 100 feet of fossiliferous shales and dolomites," at Stony Moun- 

 tain, at Clarks Point and Harbor, on the west shore of Lake Winnipeg, and, 

 10 miles south of the last-named locality, on the Little Saskatchewan River 

 from 1 to 3 miles above its mouth. 



East Selkirk: — Dolomitic limestone, having a light-buff or cream color, 

 delicately and very in-egularly streaked and mottled with light yellowish 

 brown, is quarried in three localities near East Selkirk, on the Red River, 

 about 20 miles north-northeast of Winnipeg. It has been much disturbed 

 by glacial agencies, and most of the quarrying is of large detached blocks, 

 which have been removed slightly from their original position and are 

 embedded in the di-ift. In one of the excavations a thickness of 10 or 12 

 feet of the stone is seen in place, having a horizontal stratification, at an 

 elevation approximately 730 to 740 feet above the sea. It contains abun- 



' -'Three deep wells in Manitoba." Tr.ans. Roy. Soc. Canada, Vol. IX, sec. 4, 1891, p. 91. S)im- 

 mary Report of the Geological Survey of Canada for 1891, p. 18. 



•J. B. Tyrrell, as before cited. J. F. Whiteaves, "The Orthoceratidin of the Trenton limestone 

 of the Winnipeg Basin." Trans. Roy. Soc. Canada, Vol. IX, sec. 4, 1891, pp. 77-90. 



