GLACIAL GEOLOGY OF SOUTHERN MICHIGAN. 107 



where the ice was spreading out, the till or ground moraine is compact 

 and clayey, as it is in states to the south where the ice lobes were free 

 to spread. 



The first attempt to represent the several classes of drift on a map 

 of the entire peninsula was made h\ State Geologist A. C. Lane in 1899 

 in a report on the Water Eesources of the Peninsula, but a portion of 

 the moraines of the State were represented by maps prepared by Cliam- 

 berlin and his assistants many years earlier. It is worthy of note that 

 the distribution of the most prominent moraines of the State was known 

 to the first State Geologist. Douglass Houghton, as early as 1838, and 

 briefly discussed in his First and Second Annual Reports, though the 

 name moraine was not applied. The present writer has made a de- 

 tailed study and mapping of glacial features and soils, and F. B. Taylor 

 of the lake beaches, the result of which await publication. 



• GLACIAL LAKES. 



When the ice lobes of the Lake Michigan, the Saginaw Bay, and the 

 Huron-Erie basins had shrunk to positions within the limits of their 

 respective drainage basins so that there was a slope toward the ice 

 front, glacial lakes accumulated to a height sufficient to maintain a 

 discharge across the lowest available point on the rim of each drain- 

 age basin. The lake which occupied the southern end of the Lake Michi- 

 gan basin has been termed Lake Chicago; that at the western end of 

 the Huron-Erie basin, Lake Maumee; and that in the Saginaw basin, 

 Lake Saginaw. The outlet of Lake Chicago was through the Desplaines 

 River valley to the Illinois and Mississippi ; the outlet of Lake Maumee 

 was through the Wabash and Ohio valleys into the Mississippi, while 

 the outlet of Lake Saginaw was through Grand River valley to Lake 

 Chicago. Eventually the ice shrank sufficiently to permit the lake in 

 the Huron-Erie basin to discharge to Lake Saginaw, and finally become 

 merged with that lake at a common level. Each change of outlet and 

 lowering of lake level has given rise to the application of a new name 

 to the water body in the Huron-Erie basin so that its stages are called 

 successively Lake Maumee, Lake Whittlesey and Lake Warren. At each 

 of these levels the lake persisted long enough to form a strong beach or 

 shore line. The shore line of Lake Whittlesey attracted the attention 

 of Bela Hubbard and others in the first Geological Survey, and was 

 traced by Hubbard from Lenawee county to St. Clair. A large part of 

 the mapping of these shore lines in Michigan has been done by F. B, 

 Taylor, though numerous short sections of them have been traced out 

 by other students in an incidental way. 



An interesting result of the study of these old shore lines appears in 

 the evidence they bring of a change in the attitude of the land. Upon 

 passing from south to north a given shore line is found to increase in 

 altitude, and as the increase is greater than can be accounted for 

 through the attraction of the ice sheet on a water body, it is evident 

 that a northward differential uplift has occurred. Recent studies of 

 the Great Lake basins by G. K. Gilbert (see Bibliography, page 109), 

 indicates that the uplift may still be in progi'ess. 



