410 PLEISTOCENE OF INDIANA AND MICHIGAN. 



But if the union took place after the opening of the Kirkfield outlet, the waters of Early 

 Lake Algonquin must have been lowered through that outlet, and when the union with Lake 

 Chicago came the whole discharge must have been given to Kirkfield, leaving the outlets at 

 Port Huron and Chicago dry. In this case the waters of the Huron-Georgian Bay-Simcoe 

 basins fell to the Kirkfield outlet immediately after Early Lake Algonquin time, and those 

 of Lake Chicago fell to it later. No facts yet known are decisive as to the time relations of 

 these events. 



When the introductory stage of Lake Algonquin, with its complicated substages, had 

 passed, the waters of all the upper basins — Huron, Georgian Bay, Michigan, and Superior — 

 came to one level with the outlet at Kirkfield, Ontario, and established the second or Kirkfield 

 stage, which endured for a relatively long time. The outlet channel at and below Kirkfield 

 shows that it carried the whole overflow. The Port Huron and Chicago outlets were therefore 

 dry, the level of the lake at that time being in all probability 50 to 100 feet below these 

 outlets and below the upper Algonquin beach as now seen in the southern parts of the Lake 

 Huron and Lake Michigan basins. 



When the outlet had been estabhshed at Kirkfield for a relatively long time and the area 

 of Lake Algonquin had become greatly expanded, the northern and northeastern parts of the 

 Great Lakes were strongly uplifted, affecting Kirkfield greatly but having no effect on Port 

 Huron and Chicago. It seems certain that when the Kirkfield outlet first opened it was 50 to 

 100 feet lower than the other two, but that when the uplift began it soon raised Kirkfield to 

 the same level and higher, carrying the whole discharge back to Port Huron and to Chicago 

 and beginning the third or Port Huron-Chicago stage. The outlet at Chicago was held firm 

 by a rock sill, but that at Port Huron was composed of clay and was cut down rapidly. The 

 overflow appears to have been largest at Port Huron from the first, and to have turned more 

 and more to that outlet. It was during this stage that the mam part of the great northern 

 uplift took place, raising the region north of Lake Huron and Georgian Bay and most of that 

 around Lake Superior by at least 600 or 700 feet. South of the isobase of Kirkfield the beach 

 of the Kirkfield stage was everywhere submerged. Hence all the Algonquin beaches south of 

 this isobase and probably some of the higher ones north of it belong either to the third or Port 

 Huron-Chicago stage, or to the intervening three-outlet phase, when the overflow was changing 

 from Kirkfield to Port Huron and Chicago and all three outlets were active at once. 



The Port Huron-Chicago stage continued until the ice sheet withdrew from the Mattawa 

 and Ottawa valleys and permitted the waters to escape in that direction, diverting the over- 

 flow from Port Huron and Chicago and initiating a short three-outlet or two-outlet phase, 

 known as the Ottawa transitional stage. The waters fell until the rocky divide at North Bay 

 became the sill over which the outlet stream flowed to the Ottawa Valley. This last event 

 marked the total withdrawal of the ice, brought Lake Algonquin to an end, and inaugurated 

 the nonglacial Nipissing Great Lakes. 



THEORETICAL RELATIONS OF THE BEACHES. 



Lake Algonquin appears to have attained nearly its greatest extent before it was affected 

 by much uplifting or warping of the land. If during all this time it had had only one outlet 

 and if this outlet had remained unaffected by erosion so as to keep the lake constantly at one 

 level, then the whole extent of beach made during that time would constitute one continuous 

 individual and, in distinction from other lower beaches of Lake Algonquin, might be truly 

 designated as the upper or highest beach of the lake. But as a matter of fact there were, 

 during the time preceding the great uplift, two or three changes of outlet involving at least 

 slight changes in the altitude or level of the lake surface. Then later the great uplift produced 

 another change, causing one outlet to be abandoned and two others to become active, and 

 dividing the discharge between them. One or possibly both of these outlets had carried the 

 discharge of this same lake at an earlier stage. Such changes give considerable complexity 

 to the history of what is seemingly the highest Algonquin beach. Except at a few places 

 (all in the far north) what appears to be the highest Algonquin beach is everywhere about the 



