BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 19, pp. 29-52, PLS. 1-2 MARCH 30, 1908 



BEGINNING AND EECESSION OF SAINT ANTHONY FALLS' 



BY FREDERICK W. SARDESON 



(Presented by title before the Society December SO, 1907) 



CONTENTS 



Page 



Introduction 29 



Contrasting valleys of the Mississippi and Minnesota rivers 31 



Beginning of the Saint Anthony gorge 36 



Early stages of the falls 37 



The gorges at Minnehaha falls 40 



The Lake Street terraces and fallscarp 43 



Other terraces 44 



The Nicollet Island rapids 4G 



Saint Anthony falls 47 



Conclusion 48 



iNTRODUCTIOISr 



It is now 30 years since Professor N. H. Winchell first discussed the 

 history of Saint Anthony falls and 20 years since his final description of 

 "The Eecession of the Falls of Saint Anthony" was pulilished.^ 



The conclusions which he then reached have stood without revision 

 or notable modification to this time. Both his description of the sharply 

 defined gorge in which the Mississippi river runs from the falls at Minne- 

 apolis to near its junction with the Minnesota river and his interpreta- 

 tion of the gorge as the work of the gradually receding waterfall appear 

 to have been generally accepted as final. The Saint Anthony gorge 

 stands therefore today with that of Niagara falls, as one of the great 

 geological timepieces by which the duration of time since tlie Glacial 

 period may be calculated. 



The gradual recession of Saint Anthony falls for the distance of about 

 8 miles in about 8,000 years, marking the time since the final melting of 



1 Manuscript received by tlio Secretary January 21, 1908. 



'Geological Survey of Minnesota, Fifth Annual Report, 1877, p. 17.'>. Final Report, 

 vol. 11, 1888, p. 313. 



IV — Bull. Geol Soc. A.m., Vol. 19, 1907 (29) 



