POET HURON MORAINIC SYSTEM AND PKOBABLE CORRELATIVES. 305 



was laid down in large part by ice and that its limits mark the extent of the glacial readvance. 

 The red color is as pronounced in Wisconsin as in the reddest phases in Michigan. The path of 

 the ice which reached Michigan on this interpretation seems to have led through less heavy 

 deposits of lacustrine silt than that which reached the Wisconsin side of the Lake Michigan 

 basin. Possibly the Michigan side owes the redness of its material entirely to the incorporation 

 of material derived directly from the rock formations in the eastern part of the northern 

 peninsula. 



OTJTWASH. 



The outer moraine is accompanied by a broad outwash apron, one of the best developed in 

 Michigan. Its general width is 5 or 6 miles and it is present along nearly the entire length of 

 the outer moraine from eastern Oscoda County around to the border of Lake Michigan in Mason 

 County. 



Numerous small basins and some large ones lie in this gravel plain, and some of them con- 

 tain lakes. Otsego Lake, one of the largest lakes in the interior of Michigan, lies south of Gay- 

 lord, partly in this outwash apron and partly in a depression between drift ridges of earlier date. 

 Possibly this lake is in a valley that was blocked at the north by the deposition of the outwash. 



Outside the second moraines from the reentrant angle between the Michigan and Huron 

 lobes near the corners of Charlevoix, Cheboygan, and Otsego counties the drainage was directly 

 southwestward to the bend of Boardman River in southern Grand Traverse County through a 

 plain ranging in width from 2 miles to about 8 miles. From Boardman River the- drainage con- 

 tinued southwestward past Interlochen and down Betsey River to Thompsonville, where it 

 turned southward down Bear Creek valley to Manistee River, and then led southwestward 

 through a series of gravel and sand plains that follow the line of the moraine. The material 

 in this outwash belt is fine gravelly sand, very little coarse gravel being present in the line of the 

 main channel. In the recesses west of Traverse City the outwash is in places of coarse material, 

 indicating vigorous discharge, as might be expected from the steepness of the descent. The 

 altitude in the reentrant angle exceeds 1,200 feet, and the glacial drainage channel drops to 

 about 1,000 feet at Kalkaska in a distance of 30 to 35 miles, to 800 feet in the next 40 miles, and 

 to about 700 feet in 20 miles more. This drainage, it should be remembered, is in a region which 

 has suffered northward differential uplift (see pp. 430, 439) of 75 to 100 feet between the south- 

 ern and northern ends of the channel, which would reduce the original rate of fall about 20 

 per cent. The effect of the high gradient is probably largely offset by the breadth of the 

 tract through which the waters found their passage. They were probably split up into several 

 streams of relatively small volume and were lacking in vigor notwithstanding their rapid descent. 



Southeastward from the reentrant angle the drainage seems to have made its way through 

 gaps among the morainic tracts of northeastern Otsego, central Montmorency, southwestern 

 Alpena, and central Alcona counties to join the border drainage on the northwest side of the 

 Saginaw lobe. These gaps are filled with fine sandy material deposited apparently under ponded 

 conditions or by rather sluggish streams. 



INNER BORDER. 



HURON SLOPE. 



DISTRIBUTION OF MORAINES. 



Several ridges of morainic type lying some distance north of the morainic system trend 

 northwest and southeast, approximately parallel with the main system, but no continuous 

 morainic belt traverses the entire length of the northern Huron slope. The isolated short 

 morainic ridges He so far out of line as to make their correlation with one another uncertain; 

 in fact they seem likely to have been developed at different times in the retreat of the ice border. 

 Some are arranged in an overlapping series, showing successive development instead of strict 

 contemporaneity. A series of three lies in southeastern Cheboygan and southwestern Presque 

 34407°— 15 20 



