THE LATE WISCONSIN DRIFT SHEETS. 339 



SECTION IV. THE VALPARAISO MORAINIC SYSTEM. 



The morainic system discussed under this name was brought to notice 

 by Chamberlin in an early report of this Survey, under the title "The 

 Moraine of the Lake Michigan Grlacier." I Inasmuch as the morainic 

 system was formed by an ice lobe which was almost confined to the basin 

 of Lake Michigan, it seems convenient to speak of it as the product of the 

 Lake Michigan glacier rather than to apply the more comprehensive term, 

 Illinois Glacial Lobe; and the drift is conveniently referred to as the Lake 

 Michigan drift. 



The course of this morainic system as outlined in the Third Annual 

 Report was chiefly traced from northeastern Illinois around the head of 

 Lake Michigan by Prof. L. C. Wooster, who subsequently examined it in 

 more detail. Chamberlin gave it considerable study in connection with his 

 investigations farther north and east. The writer's studies began after the 

 publication of that report. He has given this niorainic system but little 

 attention in northwestern Indiana, but has made a somewhat detailed study 

 of it in southwestern Michigan and in portions of northeastern Illinois not 

 covered by Wooster. 



The name Valparaiso, taken from a city of that name located on a 

 very prominent portion of the morainic system in northwestern Indiana, 

 was suggested by Wooster in a manuscript report and has been used by 

 the writer in previous papers which touch upon this system. 



DISTRIBUTION. 



As pointed out by Chamberlin, this morainic system "may be likened 

 to an immense U, embracing the great lake between its arms." It has a 

 length from north to south of over 100 miles, if portions coalesced with 

 older moraines on its outer border be included. The breadth of the lobe 

 averages nearly 100 miles. The parallelism of the morainic system to the 

 shore of Lake Michigan is one of its most striking features. In the portion 

 examined by the writer, which lies south of the latitude of the Illinois and 

 Wisconsin State line, the inner border is usually less than 15 miles and at 

 its closest approach is only about 6 miles distant from the lake, and this close 

 parallelism is known to be continued still farther north. In this portion 

 the breadth of the morainic system ranges from 5 or 6 miles up to nearly 



1 Third Annual Report U. S. Geol. Surrey, 1881-82, pp. 322-325. 



