CORRELATION OF RAISED BEACHES 413 



Geological Survey/ were taken to mark a local ice-front lake, Lake 

 Chicago. Of these beaches, the highest, about 60 feet above the lake, 

 and a lower one about 40 feet, were not known to extend north of 

 Racine County, Wisconsin, until very recently, when Alden found a 

 terrace near Belgium (a few miles north of Port Washington) which 

 corresponds somewhat closely to the 40-foot plane. 



According to Taylor's studies, these beaches seemed to lie wholly 

 above the plane of Lake Algonquin. Lower beaches of Lake Chicago, 

 forming a complex group from 10 to 25 feet above Lake Michigan 

 and called the "Toleston" beaches, had not been traced northward 

 beyond Belgium when the present study was undertaken; and the 

 actual relation between these and the inferred Algonquin plane was 

 doubtful. It was suspected by Leverett, Chamberlin, and others 

 that the lower beaches of the Toleston group (those from 10 to 15 feet 

 above the lake) in the Chicago district might be shore-lines of Lake 

 Algonquin. 



In the summer of 1905 opportunity was given the writer by the 

 Wisconsin Geological and Natural History Survey to study the old 

 shore-lines of eastern Wisconsin with these problems of exploration 

 and correlation in mind. Sufficient evidence was collected, it is 

 thought, to show that only the beaches above 40 feet in the Chicago- 

 Sheboygan district belong to a separate Lake Chicago; that the 

 20-2 5 -foot Toleston beach of the Chicago district is the shore-line of 

 Lake Algonquin; and that the strong 14-foot terraces and ridges of 

 southeastern Wisconsin and northeastern Illinois mark the border of 

 a later stage of importance, known as the stage of the Nipissing great 

 lakes. It is the purpose of this paper to show on what grounds these 

 conclusions were reached. 



THE FIELD-WORK 



The distance around the shores of Green Bay, from Marinette 

 southward to Green Bay City, and thence northeastward to Washing- 

 ton and Rock Islands, is about 100 miles. From Washington 

 Island southward along the shore of Lake Michigan to the Illinois 

 line is approximately 200 miles. This entire stretch of shore, except 



I See Monograph XXXVIII, U. S. Geological Survey, "The Illinois Glacial Lobe," 

 by Leverett; and the Chicago Folio, No. 81, with discussion of Lake Chicago by Alden. 



