S16 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1912. 



lakes, outlet at Kirkfield, Ontario, uplift in north begins; (3) Port 

 Huron-Chicago, or Port Huron stage, outlets at both of these places 

 at first, but rapidly diminishing at Chicago and increasing at Port 

 Huron. Main great uplifts occur in this stage and cause great 

 tilting and divergence of beaches at the north. Three groups of 

 beaches formed: (a) Upper Algonquin group, (b) Battlefield group, 

 and (c) Fort Brady group. Most rapid uplift was during Battlefield 

 group, (4) closing transition stage leadmg to Nipissing Great Lakes. 

 Outlet eastward to Ottawa Valley. 



(1) Early Lake Algonquin. — At its beginning. Lake Algonquin 

 probably had a brief stage, when it was confined entirely to the 

 southern half of the Lake Huron basin. (Fig. 6, ice border at position 

 A.) The ice front then rested against the highlands which bound 

 the two sides of the southern half of Lake Huron, as shown by the 

 moraines in both Michigan and Ontario. This stage, however, was 

 of relatively short duration, for the ice front was so far north at its 

 beginnmg that a very slight additional retreat opened passages to 

 the east and northwest and lower outlets were available in both 

 directions — to the east to Georgian Bay and the Trent Valley in 

 Ontario and to the northwest to Lake Chicago and through this to 

 the Chicago outlet. These two passages probably opened nearly at 

 the same time. From the fact that no separate beach or outlet is 

 known for this stage, it might be thought that this lake is wholly 

 hypothetical and its existence entirely uncertain. But, besides the 

 logical consequences of the relation of the ice sheet to the highlands 

 (fig. 6), the early distributaries of the St. Clair and Detroit Rivers 

 seem inexplicable, except as incidents of the transition from Lake 

 Lundy to a lower stage corresponding to Early Lake Algonquin. 

 And further, the five short gorges which Niagara River made in the 

 Niagara escarpment during its early flow, which was of relatively 

 short duration, show conclusively that Niagara River then had a 

 volume as large or very nearly as large as at present, and this could 

 not have been the case, except by a large contribution of water to 

 Lake Erie from the north. This was clearl}^ before the opening of 

 the Kirkfield outlet in Ontario. The discharge from Early Lake 

 Algonquin was larger than might be expected, because this lake 

 received a large afiluent from the east, from the region of the Notta- 

 wasaga Valley and Lake Simcoe in Ontario, and also a large amount 

 directly from the ice barrier. 



(2) The Kirkjield stage. — There seems to be no reason to suppose 

 that the Chicago outlet was at this time low enough to take the whole 

 discharge from Port Huron. On the other hand, the Trent Valley 

 outlet at Kirkfield, Ontario (fig. 7), was surely low enough, and as 

 soon as it opened the overflow went to the Trent Valley and the 

 level of the lake fell below the outlets at Port Huron and Chicago, 



