BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 33, pp. 491-514 September i, 1922 



STAGES OF THE ICE AGE * 



BY WARREN UPHAM 



{Presented before the Society December 28, 1921) 



CONTENTS 



Page 

 Sequence of glacial and interglacial stages 491 



Nebraskan glaciation 493 



The Af tonian interglacial stage ,.,.,, 495 



Kansan glaciation . . = . . 499 



The Yarmouth interglacial stage , 503 



Illinoian glaciation 504 



The Sangamon interglacial stage 505 



lowan glaciation and loess deposition 506 



The Peorian interglacial stage 506 



Wisconsin glaciation 507 



The Champlain stage 510 



Estimated time ratios 512 



Sequence of Glacial and Interglacial Stages 



Throughout the Glacial period of growth, culmination, and decline of 

 the North American and European ice-sheets, the climate causing the 

 snowfall and ice accumulation fluctuated to such an extent that the 

 boundaries of the continental glaciation were alternately advanced and 

 checked or drawn back. 



North America had five stages of widely extended icefields. First was 

 the long time of N"ebraskan glaciation, followed by a great recession of 

 the ice-borders during an interglacial stage named Aftonian, from its 

 stratified beds and fossils near Afton, in southwestern Iowa. The second 

 and maximum extension of ice accumulation is named, in the Keewatin 

 area of its outflow west of the Mississippi, the Kansan stage, which was 

 broken by the Yarmouth interval of ice melting and retreat. With the 

 Kansan glaciation, but in part spreading across the eastern edge of its 



1 Manuscript received by the Secretary of the Society December 12 s 1921, 



(491) 



