LATER MORAINES OF LAKE MICHIGAN, SAGINAW, AND HURON-ERIE LOBES. 247 



Lansing and to the Otisville and other moraines in northeastern Genesee County. The normal 

 relief of these moraines, however, is distinctly lower than that of the bulkier moraines and 

 becomes greater only where several ridges are heaped up together. 



CHARACTER. 



Where they are openly deployed, these moraines are generally smoother than the bulkier 

 moraines and show fewer knobs and basins and other irregular surface features. They show 

 comparatively little evidence of drainage issuing from the ice while they were making, and 

 perhaps on this account their crests are less broken and irregular. The general flatness of the 

 plain on which they were deposited is probably the principal cause of their comparatively even 

 trend and broad curvature. 



In the region of overriding many of the forms developed are remarkably irregular and 

 some of them are almost fantastic. Such forms appear at several places east of Lansing, north- 

 east of Otisville, and particularly in the moraine-rimmed circular basin near Duplain. 



STRUCTURE OF THE DRIFT. 



THICKNESS. 



Throughout most of this district the thickness of the drift averages about 100 feet, but 

 varies locally from practically nothing to 300 or 400 feet. (See PI. II, in pocket.) Near Grand 

 Ledge in northeastern Eaton County, and through northern Ingham County into northwestern 

 Livingston and southern Shiawassee counties, the drift is in many places thin and in some is 

 interrupted by outcrops of bedrock. Bedrock is also exposed in the Grand River channel about 

 3 miles east of Ionia. But in general the drift in Ionia, Clinton, Shiawassee, and Genesee coun- 

 ties is 100 to 150 feet in depth, and in the counties which border these on the north it is still 

 deeper. A bored well at Saranac, 8 miles west of Ionia, goes 247 feet to rock, which is there but 

 little more than 400 feet above sea level. This well seems to penetrate an old valley in the rock 

 surface which opens to the northwest and is 150 to 200 feet deep. The present surface of the 

 country, however, gives not the slightest evidence of such a depression in the rock. 



COMPOSITION. 



In its composition the drift of the district is mostly rather uniform on the visible surface 

 but varies considerably as revealed in deep sections and in well borings. For a depth, say, of 

 40 to 50 feet, the drift is predominantly clayey with a yellowish or buff color and in places with 

 a tinge of brown. The deployed moraines are composed mainly of this clay. They carry com- 

 paratively few bowlders and are notably stony only in some parts of the district of overriding 

 or where they were washed by lake waves. 



On the high ground bordering the Grand River channel many sections in the bank and 

 many well borings reveal a thick bed of sand or gravel beneath 50 to 100 feet of till. Both 

 east and west of Ionia the north bank about 85 feet above the valley floor contains a great mass 

 of gravel, though in the town tough clay occurs at that level. Many borings in other parts of 

 the district reveal beds of sand or gravel beneath the surface till or intercalated between beds 

 of till. In the district east of Lansing most of the bored wells get water which contains enough 

 petroleum to give distinct odor and taste. 



Many of the borings penetrate in the deeper parts a bed of "hardpan," or dark-colored 

 indurated till, generally very stony, from a few feet to 80 or 100 feet thick, and commonly 

 separated from the bedrock by 2 or 3 feet of open, clean gravel in which the best water supply is 

 found. The dark indurated till appears to be distinctly older than the Wisconsin drift. In places 

 it shows cemented ferruginous bands and other evidences that suggest weathering. But the 

 "hardpan" is not so thick in this district as it is in some of the neighboring counties east and 

 west. 



