306 PLEISTOCENE OF INDIANA AND MICHIGAN. 



Isle counties. (See PI. VII.) Southwest of Rogers, in Presque Isle County, there is also a 

 double moraine of considerable prominence, yet neither member can be traced for more than 

 7 or 8 miles, both fading out into sandy plains or gently undulating till tracts. 



North of Burt Lake a very prominent moraine has points that reach 900 feet and a breadth 

 of 3 to 4 miles. North of this and separated from it by only a narrow sand plain a narrower 

 morainic ridge rises above the 800-foot contour. A complex system of disjointed ridges extends 

 from Mullet Lake southeastward across Cheboygan and Presque Isle into Montmorency County, 

 the highest rising above the 900-foot contour. North of Black Lake in eastern Cheboygan and 

 northwestern Presque Isle counties a very conspicuous morainic belt about 5 miles long rises 

 above the 800-foot contour. Much of the double moraine southwest of Rogers also rises above 

 the 800-foot contour. From northern Presque Isle County southeastward into southeastern 

 Alpena County the morainic topography shows very little development, but west of Devils Lake, 

 in southeastern Alpena County, a conspicuous moraine sets in and is traceable southeastward 

 to Harrisville and thence southward nearly to southern Alcona County as a land-laid moraine. 

 Farther south its expression is much milder, and it appears to have been formed at the border 

 of Lake Warren (p. 392). It probably finds a continuation southward in either the Bay City 

 or Tawas moraines, but the great width of the gap at Au Sable River makes correlation difficult. 



The surface of the prominent morainic belts just noted presents a close aggregation of 

 knolls and basins which give the moraines strong expression. It seems remarkable that mo- 

 raines having such strong relief and such strong surface expression should be so discontinuous 

 or have such fragmentary development. 



From a' point west of the middle of Devils Lake the inner slope of this moraine is heavily 

 cut, producing a great bluff extending most of the way to Harrisville. This cutting has been 

 attributed by the authors solely to the waves of Lake Algonquin, but it is perhaps a question 

 whether it may not be due in part to a river flowing between the ice and the moraine, as was 

 the case at Romeo and probably at Gagetown. (See pp. 284, 300.) The locality was studied 

 before those at Romeo and Gagetown and has not been revisited. 



Most of these morainic ridges consist largely of loose-textured drift, with considerable 

 stony as well as sandy material. Clayey till is developed in only a few places, commonly on 

 the inner or northeast slope of the morainic ridges. There is, however, considerable clayey 

 till in the prominent morainic line in southeastern Alpena and eastern Alcona counties. 



CHEBOYGAN MORAINE. 



A very narrow morainic ridge scarcely one-fourth mile in average width, known as the 

 Cheboygan moraine, is traceable from Cheboygan northwestward to Mackinaw City along 

 the south side of the Straits of Mackinac, half a mile to a mile back from the shore. The ridge 

 is also traceable eastward from Cheboygan for about 3 miles through the southern part of 

 sees. 5, 4, and 3, T. 37 N., R. 1 W., and the ice border appears to have continued east-northeast- 

 ward to the south part of sec. 32, T. 38 N., R. 1 E., as an ice-contact face between a bowldery 

 till plain and a high sand plain to the south. Bowldery strips which run eastward for several 

 mfles farther probably represent the continuation of the border of the ice; their mapping is 

 incomplete, but they are known to extend into the north part of T. 37 N., R. 2 E., Presque 

 Isle County. The portion of this moraine and bowldery area east from Cheboygan lies within 

 3 miles of Lake Huron, at a very slight elevation above the lake level. 



Although this moraine was formed at a level much below that of Lake Algonquin, the 

 beaches of which are found on the uplands a few miles to the southwest, it is a remarkably 

 distinct ridge, with well-defined knolls and greater irregularity of surface than is common in a 

 water-laid moraine. It apparently marks the southern edge of a lobe of ice which came into 

 the northern end of the Huron basin from the northern peninsula of Michigan and appears to 

 be the youngest moraine on the southern peninsula. 



