LATER MORAINES OF LAKE MICHIGAN, SAGINAW, AND HURON-ERIE LOBES. 225 



Valparaiso morainic system near Bloomingdale and near Bangor, were noted on the crest of one 

 of these till ridges in western Allegan County. 



The plains bordering the moraines show the same changes as the moraines in passing from 

 north to south, those in the northern portion where the ridges are sandy and gravelly being 

 underlain by sandy material, and those in the southern portion bordering the till ridges being 

 underlain by clayey material. In a few places, as between Muskegon and Grand rivers, a thin 

 outwash of sandy gravel, derived from the ice border during the development of the till ridges 

 covers the till. 1 



GLACIAL DRAINAGE. 

 LINES OF DISCHARGE. 



Reference has already been made (p. 223) to the numerous lines of glacial drainage developed 

 in connection with the recession of the ice border from the outer to the inner members of the 

 Lake Border morainic system. In most areas the lines of discharge for the glacial waters are 

 very clearly shown. The most elevated outwash tract is found just north and west of Cadillac, 

 where about 100 square miles, standing at an altitude of 1,300 to 1,350 feet, was coated with sand 

 and gravel by streams issuing from the outer moraine. Clam River, a tributary of Muskegon 

 River, heads in this plain and, with the Muskegon, probably carried the glacial waters to just 

 above Newaygo, where they were deflected by ice to a well-defined channel that leads southward 

 past Rice Lake to Rapid River, a tributary of Grand River. From Grand River near Grand 

 Rapids the glacial waters made their way southward along the edge of the ice through narrow 

 lakes to the incipient Lake Chicago at the head of the Lake Michigan basin and thence down 

 the Chicago outlet. 



As a rule the outwash in all the fines of glacial drainage connected with the Lake Border 

 system is a rather fine sandy material. 



GLACIAL LAKES. 



Distribution. — During much of the time when the Lake Border morainic system was form- 

 ing the area now covered by Lake Michigan was occupied by ice, and the drainage of western 

 Michigan was forced to follow the eastern edge of the ice sheet southward to the southern end 

 of the basin, where it found discharge through the Chicago outlet into the Desplaines Valley 

 and thence to the Illinois and Mississippi valleys and the Gulf of Mexico. At that time the 

 eastern tributaries, which now lead through the Lake Border morainic system directly to 

 Lake Michigan, seem to have flowed south through a series of small glacial lakes that occupied 

 the lowest available ground outside the ice sheet. In the early part of the development of the 

 system, while the ice still covered the moraine north of Rabbit River in northern Allegan County, 

 the northernmost lake in the series was apparently one that occupied the lower Kalamazoo 

 Valley and received drainage from districts farther north through rivers whose courses lay 

 outside the edge of the ice sheet. Grand River discharged into this lake along the abandoned 

 channel that runs southward from Grand Rapids past Ross to Rabbit River. In the course of 

 development Muskegon River also found its way to Grand River at Grand Rapids through a 

 valley leading past Rice Lake to Rouge River, a tributary of Grand River heading in southern 

 Newaygo County. Later, when the ice border was close to Lake Michigan near Holland, more 

 or less ponding probably took place on the lower courses of White, Muskegon, and Grand rivers 

 and a nearly continuous lake probably extended along the edge of the Lake Michigan basin 

 from near Holland to the Chicago outlet. 



The small lakes along the edge of the ice in southwestern Michigan did not form beaches 

 of sufficient definiteness to permit easy mapping. The levels at which they stood can, however, 

 generally be determined by the deltas of their large affluents and by the height of their outlet 

 channels. The series of lakes and connecting channels was so complicated that the writer did 



1 For further details of the drift structure see Mon. U. S. Geol. Survey, vol. 38, and Water-Supply Papers IT. S. Geol. Survey Nos. 21, 182, 

 and 183. 



34407°— 15 15 



