20 Spencer — Deformation of Algonquin Beach, 



case is not settled so easily as that of the Ontario basin, for we 

 have not yet the instrumentally measurable proof that the 

 Algonquin plain was lower than 300 feet above the sea, although 

 it probably was, and against which probabiltiy there is not the 

 slightest evidence, for we do not know what was the initial 

 plain of upward movement. Without applying the objections 

 made to an ice dam closing the Ontario basin during the Iro- 

 quois episode, let us examine some conditions of the Algonquin 

 basin. 



The Algonquin plain stood at an elevation of about 300 feet 

 above the sea, when the lower Iroquois Beach commenced its 

 growth. Were its waters held up to that altitude by an ice 

 dam, or had they shrunken to the lower level (which, however, 

 would not have dismembered the upper lake) and were they 

 connected with Lake Iroquois by a strait 300 or 400 feet deep, 

 like the modern outlet of Lake Michigan ? L^p to this time, 

 there had not been any warping to separate the lake basins, for 

 the greater part of the barriers has been uplifted since the 

 episodes of the Algonquin and Iroquois Beaches. I have 

 shown that the greater proportion of the differential movement, 

 even in the higher beaches about Lake Erie has been since the 

 Iroquois episode.* In the earlier part of this paper, it has also 

 been shown that most of the warping of the beaches, east of 

 Lake Huron, Las been since the Algonquin episode. ISTow these 

 higher beaches are identical with those south of Lake Erie, 

 whose movement have been compared with those of the Iro- 

 quois Beach. Hence, it is not difficult to understand that the 

 unequal uplift of both the Algonquin and Iroquois plains has 

 been nearly synchronous, since the completion of the latter 

 beach. I speak only of the differential movements that have 

 deformed the old water levels, and not of the absolute rise, 

 which lifted the Algonquin plain above the Iroquois, unless the 

 waters which made the former beach were retained at the 

 higher altitude, for long ages, by an ice dam. 



At most, no ice barrier could have longer blocked the Xipis- 

 sing outlet than the episode of the lowering of the waters, 300 

 feet, to the level of the Iroquois Beach, for at that time, ail 

 glaciers had shrunken back beyond the Ontario basin, and the 

 two basins were connected by the deep JSTipissing Strait. And 

 of such a dam we have not proof, or even probability, to even 

 as great an extent as in the case of a hypothetical Iroquois 

 dam. With the continued regional uplift, the waters of Algon- 

 quin Lake were further lowered, as is shown by the numerous 

 beaches, until the lake was dismembered, and Sujierior, Mich- 

 igan, Huron and Georgia had their birth and drained through 



*" Deformation of the Iroquois Beach," etc. This Journal, vol. xl, page 443, 

 1890. 



