254 PLEISTOCENE OF INDIANA AND MICHIGAN. 



evidence favoring this interpretation was found. When the ice front rested on the high moraine 

 east and south of Ortonville it had free drainage southeastward into the interlobate area of that 

 time at a level over 200 feet higher than the Holly channel just north, and no certain evidence 

 of later moraines nor of ice-border drainage was found on the slope down to the channel. If the 

 ice front paused in its retreat down this slope, it made no distinct moraines and left no trace of 

 ice-border drainage. The absence of drainage channels, however, is not by itself conclusive, 

 because the interlobate area in Lapeer County may have drained southward along the east side 

 of the "thumb" during this time, and Holly Kiver may have been the first diversion of that 

 drainage to the west side. 



On the other hand, if the slender moraines of this group mark a pronounced readvance of 

 the ice front, as is perhaps suggested by the buried Lansing channel, the first diversion of drain- 

 age to the west side may have been along a line farther north than the Holly channel (pp. 252- 

 253), and the channel made then may have been overridden. The drainage line may then have 

 been pushed up the slope to the position of the Holly channel by a readvance to the Hadley ridge. 



ELBA CHANNEL. 



During the building of the Lyons moraine, which is next later than the Portland, drainage 

 from Lapeer County passed southwestward along the front of the moraine. Its course, how- 

 ever, was not determined, for the moraine disappears in the overridden belt. The drainage may 

 have reached the Holly channel in Groveland or Holly Township. 



The amount of outwash from the morainic deposits in the belt of overlapping east of Lan- 

 sing appears to be small, being limited to a few kames and to gravels and sands deposited in 

 transverse troughs which seem to be in some sense successors of lines of eskers farther south. 

 Along the Holly glacial river and in the lake region near Fen ton and Argentine in front of the 

 Fowler moraine considerable areas of gravels and sands are found, but these appear to have 

 been gathered and deposited mainly by the rivers flowing along the ice front. 



IMLAY CHANNEL AND KERSLEY GLACIAL LAKE. 



When the ice front retreated from the St. Johns moraine a great river suddenly made its 

 appearance and flowed westward close along the front of the Saginaw lobe from a point near 

 Flint to the Grand River channel at Maple Eapids and thence along the course of Maple and 

 Grand rivers to glacial Lake Chicago, which it entered a few miles southwest of the city of Grand 

 Rapids. This river came thus suddenly upon the scene when the retreat of the ice opened a new 

 outlet for the glacial Lake Maumee near Imlay in eastern Lapeer County. The new river was 

 several times larger than any of those previously described in this district, it's floor being generally 

 a mile or more in width though somewhat narrower in a few places. From its head to Maple 

 Rapids this old river bed is called the Imlay channel. 



When the river first began to flow, the ice front was resting on the Flint moraine, or probably 

 on a line a little farther north that was overridden by a readvance of the ice, but it kept its course 

 along the front of the Flint moraine westward from Flint to a point southwest of Owosso only 

 while the ice rested on that moraine. When the ice front drew back to the Owosso moraine the 

 outlet river broke through the Flint moraine at Flint and followed the front of the Owosso 

 moraine on a line farther north. The channel which it made in this new position, however, is not 

 so deeply trenched nor so well defined, apparently because the fall of the stream and velocity of 

 current were less west of Flint than they were when the ice rested on the Flint moraine. It is, 

 however, fairly well defined from a point north of Vernon westward past Corunna to Owosso. 

 The depression continues past Elsie but shows less evidence of scour west of Owosso. 



Running through the Flint moraine southwest from Owosso there is a broad, flat transverse 

 valley containing fragments of an esker on its east side. During the development of the Flint 

 moraine this was an esker trough, probably marking a strong line of drainage issuing from the 

 ice. The Michigan Central Railroad passes through it. That part of the Imlay channel which 

 runs west from this trough to Maple Rapids is generally wider and otherwise suggests somewhat. 



