206 PLEISTOCENE OF INDIANA AND MICHIGAN. 



the head of the Rives esker system (p. 192) and some spurs extending to the south. Some of 

 these spurs include esker-like gravel ridges, and some small eskers stand between the spurs in 

 the plains just outside the moraine. The range between the tops of the highest knolls and 

 the beds of the deepest depressions is 75 to 100 feet, but few of the knolls are over 50 feet 

 high and most of them are 25 feet or less. Among the knolls are numerous swampy basins, 

 but lakes are not common. 



In Livingston County, where the Charlotte system is more or less closely combined with 

 the Kalamazoo, the northern portion of the combined system resembles the Charlotte system 

 hi Ingham County. Swampy depressions containing eskers (see Fowlerville and Howell topo- 

 graphic sheets) extend from the till plain southward into the edge of the morainic system 

 and in some places connect with outwash aprons which head well back into the moraine 

 from the south border. The breaks in the moraine thus seem to be due to a combination of 

 subglacial and extraglacial drainage. 



The large kames in the midst of the interlobate tract lie, some in the Saginaw and some 

 in the Huron-Erie portion. Some prominent ones, indicated on the Howell sheet, are found 

 near the inner border, as, for instance, a kame 3 miles west of Howell, on which the tuberculosis 

 sanitarium stands, and others 3 or 4 miles northeast of Howell. Three kames west and south of 

 Chilson reach the 1,100-foot contour, rising about 150 feet above the bordering country. In 

 the northeastern portion of Livingston County, in Tyrone and Hartland townships, the inner 

 part of the moraine is very prominent; points in central Tyrone Township rise above 1,200 feet 

 and considerable areas in both townships rise above 1,100 feet, though the neighboring plains on 

 the inner border rise to less than 1,000 feet.. This prominent part as well as the lower part 

 hi the western portion of the county is traversed by deep swampy depressions, some of which 

 pass entirely through to the lines of glacial drainage leading into the interlobate gravel plains. 

 On the inner border of the morainic system, northeast and east from Howell, till plains with 

 an area of 2 to 6 square miles are nearly surrounded by tracts with a hummocky topography, 

 like the neighboring moraine. The conditions are so complex both in the moraine and on its 

 inner border that it is difficult to set forth the details, but reference to the topographic sheets 

 will serve to make many features clear. The leading features of the interlobate system in 

 Oakland and southern Lapeer counties have already been discussed. (See pp. 196-199.) 



STRUCTURE OF THE DRIFT. 



Along the entire length of the morainic system the drift is exceedingly variable. In the 

 more subdued portions the knolls are commonly capped with till, but in many places excava- 

 tions show them to have a nucleus or pocket of gravel and sand; little of the surface material 

 shows a stiff clayey constitution, though a large part of it would be classed as till rather than 

 as assorted material. The prominent portions of the moraine are made up very largely of 

 assorted material and are to be classed as kames and eskers. This morainic system includes, 

 perhaps, more small eskers than any other hi Michigan, and it receives the southern termini of 

 some of the most conspicuous eskers of the State. Some of the esker ridges have a nucleus 

 of gravel and sand with a thin capping of till, a feature which suggests that they were formed 

 near the base of the ice sheet at a horizon low enough to permit the deposition of the englacial 

 material on them. 



The amount of assorted material along the line of this morainic belt is such that wells 

 may easily be obtained at moderate depths nearly everywhere. In Ingham and Eaton counties, 

 however, where the drift is of moderate depth, it is customary to continue the wells into the 

 underlying sandstone, for the water there obtained is softer than that from the drift formations. 



The thickness of the drift is from 40 to 75 feet along much of the moraine in Eaton and 

 Ingham counties, but is much greater in Livingston and Oakland counties. In Kent County 

 the distance to rock is moderate in the vicinity of Grand Rapids and also near Lowell, but 

 elsewhere the rock surface lies so low that wells have not reached it. 



