DEPARTURE OF IQE-SIIEET FROM THE LAURENTIAN LAKES. 21 



The next [K\pt'r, l)y the same author, was read b}^ title: 



DEPARTURE OF THE WE-SITEET FROM THE LAVRENTIAN LAKES 

 BY WAKHKX I rilAM 



[Abstract] 



Conttnits 



Page 



Phenonu'iia iifteinUng tlio ivtroat oltlio contiiuMital glaeier 21 



Ancient high sliorolinos in the wc-storn part of the basin of lake Superior 22 



Beaelies of the Western Superior gh\eial hiice and their altitudes 'j:\ 



First Duitith beaeh 23 



Second Duluth beacli 2.", 



Boulevard beaeh 2:i 



Beaches of the glacial lake Warren and their altitudes 2;j 



Belmore beach 2:i 



Nelson beach 2;i 



McKwen beach 24 



Thibeault beach 24 



Double Bay beach 24 



First Beaver Bay beacli 24 



Second and third Beaver Bay beaches 24 



Chester Creek beach 24 



Beach of the glacial lake Algonquin and its altitudes 24 



Western Superior glacial lake 24 



Lake Warren 25 



Lake Algonquin 25 



Order of recession of the ice-sheet territorially 2(5 



Character and progress of the uplift following recession of tlie ice-sheet 27 



Phenomena attending the Retreat of the continental Glacier. 



The glacial drift reveals to us far more of the history of the Chain])laiii epoch or 

 time of general retreat of the ice-sheet with deposition of its drift and accumula- 

 tion of its retreatal moraines than all which we can learn concerning the oncoming 

 and culmination of the Ice age. During this closing Champlain epoch of the Ghx- 

 cial period lakes of great extent, held in on their nortliern and northeastern or 

 iceward sides by the l)arrier of the gradually waning and departing ice-sheet, 

 existed in tlie valley of the Red river of the North and the basin of the great lakes 

 of Manitoba and in the basins of the Laurentian lakes, Superior, Michigan, Huron, 

 Erie, Ontario and Champlain. The glacial lake Agassiz, attaining an area of more 

 than 1(X),000 sijuare miles, occupied the Red river valley and a large i)art of INIani- 

 toba, and the similar but smaller lakes Warren, Algon(iuin, Iro(iuois^and lludson- 

 Champlain, in part successive and in part contemporaneous with one another, 

 tilled the basins of the great lakes now outflowing by the Saint Lawrence, their 

 ancient shorelines, with beaches and deltas, being much higher than the present 

 lake levels. The uplift of the area of lake Agassiz was practically (•())iii)lete(l dur- 

 ing the Champlain epoch or time of the glacial retreat, as is known hy (he imri- 

 zontality of its lowest and latest beaches, whereas its highest and earliest shores 

 have receive<l an inclination of ascent northward averaging ahout one foot i)er 

 mile along their observed extent of 400 miles.* In like manner, but with greater 



•" Wnvclike Progress of an Epeirogenic Uplift," Journal of Geology, vol. ii, pji. 38^-31)5, May- 

 Junc, WJl. 



