MORAINIC SYSTEMS AT HEADS OF LAKE MICHIGAN AND SAGINAW BASINS. 195 



On the outwash plains surface bowlders are rare, and the plains rise above the level of the knolls 

 that stand in the basins. 



The outwash is very largely fine gravel, though in places on the immediate border of the 

 moraine it carries cobbles and even coarser rock material at the surface. It commonly includes 

 sand and in places is so sandy as to be unsuitable for road ballast. The large amount of the 

 sand is probably attributable to the interruptions to free flow by masses of stagnant ice and 

 also to the wide branching and rather low gradient of the streams flowing away from the ice 

 sheet. 



The plain in the reentrant between the Saginaw and Huron-Erie lobes slopes gradually 

 soutlrwestward toward the valley of Wolf Creek, an eastern tributary of Grand River entering 

 at Jackson. It has a width near Grass Lake of about 6 miles. Its altitude at the border of the 

 moraine north and northeast of Grass Lake is about 1,030 feet, but between Grass Lake and 

 Wolf Creek it scarcely exceeds 1,000 feet. 



BORDER DRAINAGE. 



The border drainage led westward from Jackson at different levels ; the altitudes of the 

 outer or southern channels, which pass south of Spring Arbor, are between 990 and 1,000 feet, 

 and those of the northern ones, which lead past Trumbull station west of Jackson, are about 

 960 feet on the divide between Sandstone Creek, a tributary of Grand River, and Rice Creek, 

 a tributary of Kalamazoo River. The altitude of a channel east of Parma leading more directly 

 to the Kalamazoo Valley is also about 960 feet. The width of these channels is irregular, being 

 commonly one-fourth mile, but ranging up to nearly a mile. They generally have steep banks 

 or low bluffs 15 to 20 feet in height. Their bottoms are marshy, for their gradients are too low 

 for the present small streams to drain them effectually. Portions of the beds in the vicinity 

 of Parma are thickly strewn with bowlders, so that the land if drained could scarcely be culti- 

 vated. It is probable that the northern channels formed the outlet for the outwash tract in 

 the reentrant east of Jackson during much of the time it was receiving outwash from the border- 

 ing ice lobes. 



The westward descent brings the channels along Rice Creek and Kalamazoo River down to 

 about 900 feet, at which level they open into the gravel plain near Marshall. The altitude of 

 the gravel plain next to the moraine is more than 900 feet for several miles west of Marshall 

 and over a considerable area in the reentrant between the Saginaw and Lake Michigan lobes 

 in northeastern Kalamazoo and southwestern Barry counties, but in the vicinity of Kalamazoo 

 River it is a little less than 900 feet. It seems to have been about 875 feet where the drainage 

 turned southward from the Kalamazoo toward the St. Joseph Valley in eastern Kalamazoo 

 County. 



THICKNESS. 



The thickness of the outwash deposit is known only in places where wells pass from the 

 surface gravel into underlying till or into bedrock. A few wells northeast of Kalamazoo on an 

 elevated part of the gravel plain enter till at about 40 feet. Directly east of Kalamazoo on the 

 south side of Kalamazoo River the outwash deposit is very thin, so that the till in places is at the 

 surface. This tract, however, has suffered some erosion because of the concentration of so 

 much glacial drainage. In the district between Battle Creek and Marshall the outwash gravel 

 seems to have been but a few feet thick, for the ravines Cut down into bowldery drift and in 

 places sandstone is near the surface. The depth of the outwash material in the plain east of 

 Jackson is likely to equal the depth of the basins, which is 30 to 50 feet. 



