MICHIGAN ACADEMY OF SCIENCE. 37 



determined sufficiently to afford data as to the area of the lake or the 

 heijilit of its beaches. Professor Coleman has noted shore features 

 on the northeast liorder of the Lake t^nperior basin n]) to an altitude 

 of about 1,400 feet above the sea or 800 feet above Lake Superior which 

 are thoiight to rejiresent the work of Lake Algonquin.^ 



The area of Lake Algonquin has suffered differential uplift through- 

 out the Superior basin and much of the Huron basin, but uplift has 

 affected only the northern portion of the Michigan basin, as may be 

 seen by reference to Fig. 7. In the southern portion of the Huron basin, 

 and as far north in the IMichigan basin as the mouth of Grand Traverse 

 Bay, and the north end of Door peninsula in Wisconsin, the amount of 

 uplift has been but a few feet, and the slope of the beaches is therefore 

 very gTadual, with scarcely any splitting into separate members. 

 Farther north, however, the rate of uplift is much more rapid, and the 

 beaches are found to split up into several members. The splitting of 

 the beaches shows clearly that the uplift was in progress during the life 

 of Lake Algonquin. The divergence of the several members of the Al- 

 gonquin shore amounts to more than the uplift which has taken place 

 since the lowest of the beaches was formed. It thus appears that the 

 resilience was very rapid in the course of the departure of the ice, though 

 there was not a complete restoration of the preglacial level, and a slow 

 rate of uplift is apparently going on at the present da.y. 



It is a matter of interest to note the area affected by uplift during 

 the Lake Algonquin stage does not extend so far south in the Huron- 

 Erie basin as that which affected the shores of Lake Whittlesey and 

 Lake Maumee, but the cause for the lessening of the area of uplift is not 

 as yet fulh' established. The features suggest a complete resilience 

 in the soutliern portion of the uplifted area ver^' soon after the reces- 

 sion 01 the ice from that area ; whereas farther north complete resilience 

 has not as yet been attained. 



It will be noted that the trend of the isobases of Lake Algonquin 

 is not uniform through all the area of uplift (Fig. 7), the trend being 

 more nearly east to west in the Michigan basin than in the Huron and 

 Superior basins. If we may judge by the isobases of Lake Duluth in the 

 Avestern Superior basin (Fig. 2). the trend of the isobases is not uniform 

 throughout the width of that basin. The tilt lines in different parts of 

 tlie Lake Algonquin region, or lines at a right angle to the isobases, have 

 a tendency to trend in the direction of the axial movement of the ice in 

 each of the gi'eat basins, the movement in the Michigan basin being more 

 nearly southward than in the Superior and Huron basins. This may 

 signify that the variations in the trend of the tilt line have been gov- 

 erned to some extent by the lines of heaviest ice weighting. 



TRANSITION LAKES (BATTLEFIELD AND FORT BRADY BEACHES ). 



The Algonquin Lake stage was brought to an end b}' the opening of an 

 eastward passage along the ice border into the Ottawa valley, just as 

 Lake Warren was brought to an end by the opening of a passage along 

 the ice border into the Mohawk valley. The Ottawa valley is several 

 miles in width, and the ice border appears to have shrunk across it from 



^Eighteenth Annual Report, Bureau of Mines, Ontario, 1909, pp. 286-87. 



