302 PLEISTOCENE OF INDIANA AND MICHIGAN. 



Huron morainic system on the "thumb" of Michigan. When the ice front was resting on this 

 moraine on the "thumb" it made at least three or four subordinate oscillations before it 

 uncovered lower ground and allowed the waters of Lake Whittlesey to fall to lower levels. At 

 the east end of Lake Erie these three or four ridges were not set close together but were deployed 

 at considerable intervals, and during the making of the first three or four the level of Lake 

 Whittlesey was not affected. Apparently the Alden moraine was the last ridge made while 

 Lake Whittlesey kept its level. This moraine is therefore believed to be the correlative of 

 the last of the secondary ridges on the "thumb" which held Lake Whittlesey up to its level. 

 The eastern equivalents of the Port Huron morainic system include in all probability the 

 Gowanda, Hamburg, Marilla, and Alden moraines as described by Mr. Leverett. 1 



PORT HURON MORAINIC SYSTEM IN NORTHERN HURON AND NORTHERN 



MICHIGAN BASINS. 



By Frank Leverett. 



GENERAL RELATIONS. 



In the northern part of the southern peninsula a complex group of moraines appears 

 to continue the Port Huron morainic system to the north and west from the Au Sable Valley, 

 where Mr. Taylor's description ends. (See pp. 293-301.) It embraces all the moraines and 

 associated glacial features found on the slopes descending toward the northern end of Lakes 

 Huron and Michigan from the great table-land in the northern part of the southern peninsula. 

 The moraines of this system in places show a discordance in relation to the earlier ones 

 such as might result from a readvance following a marked recession of the ice border. Further 

 evidence that the moraines of this group are markedly younger than the ones outside is shown 

 by the relation of the moraines in the Michigan basin to the beaches of Lake Chicago. It is 

 by means of this relation to the beaches that correlations have been made with moraines on 

 the Wisconsin side of Lake Michigan. 



DISTRIBUTION. 



In the northern part of the southern peninsula the border of this morainic system follows 

 the northern edge of the high table-land in which Au Sable and Manistee rivers rise. It is 

 accompanied by a great outwash gravel plain or apron that bears evidence of a prolonged stand 

 of the ice border at this culminating position. From the Au Sable Valley in eastern Oscoda 

 County the outer moraine leads northwestward across Montmorency to northwest Otsego 

 County, where there was a reentrant between the Huron and Michigan lobes. Thence it goes 

 southwestward through Antrim and Kalkaska counties, keeping just east of the line of the 

 Grand Rapids & Indiana Railway, leads westward across southern Traverse County, and turns 

 south through eastern Manistee County, keeping a few miles back from Manistee River through- 

 out its course in these counties to the latitude of Manistee, where it crosses the river, beyond 

 which it is continued only as disjointed ridges. These ridges lead southwestward nearly to 

 the shore of Lake Michigan in western Mason County at the east end of Hamlin Lake, then 

 make a southeastward detour into southern Mason County and come back to the shore of Lake 

 Michigan south of Ludington. In Oceana County they are in places banked against the western 

 end of the great spur of the Lake Border system (p. 223). South of this spur are two ridges. 

 One, known as the Whitehall ridge, lies 3 to 5 miles back from the shore of the lake and is trace- 

 able past Whitehall to Muskegon, south of which it passes into Lake Michigan. West of White- 

 hall in northern Muskegon County a second ridge, which seems closely related to the outer one, 

 appears for a few miles along the shore of Lake Michigan; it was not recognized farther south 

 than White Lake. 



On the Wisconsin side of Lake Michigan the correlative of this moraine seems to be 

 found in a deposit of red till which covers a narrow strip on the coast from Milwaukee north- 



i Mon. U. S. Geol. Survey, vol. 41, 1902, pp. 673-685. See also Niagara folio (No. 190), Oeol. Atlas U. S., U. S. Geol. Survey, 1913, fig. 8, 

 p. 17; also Trans. Canadian Inst., vol. 10, 1913, map opposite p. 23. 



