730 PROCEEDINGS OF THE OTTAWA MEETING 



ALTERATION OF SERPENTINE 

 BY A. KNOPF* 



Published as Bulletin of the Department of Geology, University of 

 California, volume 4, no. 18. 



PLEISTOCENE PHENOMENA IN THE MISSISSIPPI BASIN; A WORKING 



HYPOTHESIS 



BY W. G. TIGHT 



[Abstract] 



The present hypothesis proposes that prior to the earliest ice invasion of the 

 Pleistocene the drainage of the upper Mississippi basin was to the northward. 

 The early ice movements in occupying this basin were forced to advance against 

 the general slope of the basin, and hence the ice-front advanced upon a rising 

 plane. This produced frontal impounding of the drainage waters, with the 

 development of extensive frontal lakes and accompanying sluggish action of 

 the ice-front, poorly developed moraines, extra morainic drift, and sluggish 

 movement of the gravel trains from the margin of the ice. A new outlet to 

 the basin was developed along the line of the middle Mississippi section, which 

 became well established as the upper Mississippi drainage developed, with the 

 early recession of the ice. Later ice invasions into the basin followed the 

 established gradients, developed into extensive lobate forms, produced only 

 local and minor frontal lake phenomena, almost no extra-morainic drift, show 

 strong morainic development and vigorous action of streams discharging from 

 the ice-front. 



The Section then adjourned till next morning. 



Session of the Cordilleran Section, Saturday, December 30 



The Section was called to order at 10 a m, President W. G. Tight in the 

 chair. 



The following papers were read and discussed: 



CREOENTIO GOUGES ON GLACIATED SURFACES 

 BY G. K. GILBERT 



Printed as pages 303-316 of this volume. 



MOULIN WORK UNDER GLACIERS 

 BY G. K. GILBERT 



Printed as pages 317-320 of this volume. 



* Introduced by Andrew C. Lawson. 



