472 A. W. G. WILSON — SHORELINE STUDIES ON ONTARIO AND ERIE 



I 'age 



Distribution of waste ou the shores 497 



Summary : Place in cycle of shore development 499 



Clomparison of modern Ontario and glacial lake Iroquois 500 



General Character of the Basins op both Lakes 

 topograpey of the basins— complex 



The general character of the topography of the basins of the different 

 lakes can be most readily understood from the standpoiat of a physiog- 

 rapher by describing the region as an ancient belted coastal plain subse- 

 quently modified by glacial ice. The inner lowland, that bounded on the 

 south and southwest by the Niagara cuesta, is occupied in part by the 

 Georgian bay and ia part by the bed of lake Ontario, there being also in 

 Ontario an nnsubmerged portion of this lowland lying between the two 

 bodies of water just mentioned. The outer lowland, bounded by the 

 margin of the Cumberland plateau, is in its lowest parts occupied (in 

 part) by the beds of lakes Erie, Huron, and Michigan. . The waters of 

 Georgian bay, which is confluent with lake Huron, cover parts of the 

 inner and innermost lowlands, and in this area the escarpments separating 

 the three lowlands are partly submerged at the present time. 



There seems to be little doubt but that immediately prior to the advent 

 of the Glacial period the topographic features of the rock-basins of the 

 Great Lakes region were developed in all their essential features at least 

 as much as we find them today. During the Glacial interval the topogra- 

 phy already developed was modified both by degradation and aggradation 

 within the basins, so that at the time of withdrawal of the last ice-sheet 

 the relatively simple topography of the rock-basins had become more com- 

 plicated by the superposition in many parts of the basins of till and other 

 glacial materials. During the interglacial intervals the glacial debris of 

 the earlier periods was variously shifted by aggrading and degrading 

 agencies. During the Great Lakes period immediately following the last 

 Glacial epoch, while the bedrock topography was little modified, we find 

 that in places the glacial materials were partially eroded, and that the 

 eroded material was deposited elsewhere. Although the total amount of 

 material thus shifted was large, relatively it was too small to have any 

 great effect in modifying preexisting topography in the basins now occu- 

 pied by the waters of the Great lakes. 



INITIAL CHARACTER OF THE SHORELINES 



We find that the initial topography of the basins was somewhat com- 

 plex. In small part the lakes were bordered by portions of bedrock topog- 



