BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 VOL. 29, PP. 235-244 JUNE 30, 1918 



EXPLANATION OF THP] ABANDONED BEACHES ABOUT 

 THE SOLF^rn END OF LAKE MICHIGAN ^ 



BY G. FKEUEKICK WRIGHT 



{Presented in abstract before (he iSoriety December 28, 1916) 



CONTENTS 



Page 



L)eh5crii)tion of the beaches , 2.'i5 



Peat deposits between the second and third beaclies 'I'M 



The series of moraines 2:>.S 



History of the ChicajiJjo outlet 'I'.VA 



Supposed clian,ij:es of hind levels 240 



Supposed earlier openinj; of the Sa.i; outlet 240 



Effects of the divei'sion of the water In the .Ljlacial lakes in Ihe Erie- 

 Ontario Basin 241 



Glacial and clay deposits underneath Chicago ; 24;j 



I'rovisional estimates of glacial time afforded in this area 244 



Descriptioist of the Beaches 



Three abandoned postglacial beaches at the south end of Lake Michigan 

 have been known for many years. In 1870 Dr. Edmund Andrews de- 

 scribed them in a very elaborate paper published by the Chicago Academy 

 of Sciences. Later, Mr. Leverett, in his monograph, "Illinois glacial 

 lobe," and Mr. William C. Alden, in his Chicago Folio of the U. S. 

 Geological Survey, have collected the facts in very full measure. From 

 these and other published observations it appears that, surrounding the 

 south end of Lake Michigan from about the vicinity of Waukegan, on the 

 west side, and extending indefinitely northward on the east side, there is 

 an abandoned beach approximately 60 feet above the level of the lake. 

 This is called the Glen wood beach. 



Twenty feet lower, or al)Out 40 feet above the present level of tlie lake, 

 occurs what is called the Calumet beach. Twenty feet lower still, oi- 

 approximately 20 feet above the level of th^ lake, occurs the Tollestoii 

 beach. These are shown on the accompanying map (figure 1), compiled 



Manuscript received by the Secretary of the Society March It), 1918. 



(235) 



