LATER MORAINES OF LAKE MICHIGAN, SAGINAW, AND HUKON-ERIE LOBES. 259 



Eureka the moraine seems to be cut away entirely. The part north of Maple Rapids was 

 attacked by waves in the same way but was not comparably eroded. The conclusion seems 

 plain, therefore, that it was the return of the outlet river to a course close in front of the ice, 

 when the ice began to withdraw from the moraine west of Eureka, that caused the heavy cutting 

 along this part. 



These facts seem to establish bej'ond a doubt a movement of readvance to the Owosso 

 moraine amounting to at least 4 or 5 miles, and as no reason can be assigned why there should 

 have been a readvance to the Owosso moraine more than to others of the deployed group, there 

 is a possibility that a similar readvance preceded the building of each one of the slender moraines. 

 If oscillations with moderate readvances like this characterized the whole group the fact is 

 highly important in the discussion of all glacial and climatic questions and theories. 



Henderson moraine. — A mile or two east of Bannister a faint bowldery belt having a north- 

 west trend forms the watershed between Saginaw Bay and Lake Michigan. This belt, which 

 apparently marks the course of the Henderson moraine (the next following the Owosso), shows 

 no tendency to bend westward into the Grand River channel. The ice front did not form a 

 tongue like that of the Owosso moraine, for at this stage the moraine lay on flat ground a little 

 east of the head of the channel. That the outlet was not cut back to this position seems certain, 

 from the fact that though the outlet river was active for a relatively long time after the ice 

 had retreated permanently from this vicinity, there is now only a very shallow broad depression 

 on the divide. The original divide was farther west. 



TERRACES IN THE GRAND RIVER CHANNEL. 



In addition to the relatively small, thin gravel deposits associated with the moraines at 

 the top of the bluff (p. 256), a complex set of gravelly terraces and bowldery benches occurs 

 along the sides of the Grand River channel. The principal gravelly terraces are from 15 to 45 

 feet above the channel floor, but some fragments are found at higher levels. 



East of Matherton, on the south side of the channel, a well-defined bowldery terrace, 

 evidently at one time part of the channel floor, now stands slightly above it for over 2 miles. 

 About 2 miles above Lyons one of the finest terrace fragments in the valley runs along the 

 north side of the channel for about 3 miles and is 30 to 35 feet above the swampy floor. 



Between Matherton and Maple Rapids there are two islands in the old outlet channel, or 

 rather one long, narrow island broken by a cut that does not reach to the bottom of the present 

 channel. The island is a little over one-half mile in width at its east end, but in a mile narrows 

 to less than one-fourth mile, and west of the transverse trough decreases still more, being at 

 its extreme west end only 250 or 300 feet wide. The island is a remnant of the original till plain 

 and is flat topped, with an altitude of 50 to 60 feet above the channel floor. Just west of Maple 

 Rapids the channel divides in equal parts around this island, Maple River passing now on the 

 north side. Hayworth Creek enters the south channel south of the east end of the island and 

 runs northeast on the swampy floor to Maple River just below Maple Rapids. Islands like this 

 are common at the head of most glacial outlets. In this particular place the early flow of the 

 Imlay outlet river appears to have started the channel on the south side and a smaller stream 

 that on the north, both at levels considerably above the present channel floor; subsequently 

 the outlet river occupied and deepened both. 



ALLUVIAL FANS. 



After the Grand River channel was abandoned by the outlet river every stream that 

 came into it began to build an alluvial fan. Above Lyons all the fans are small and the channel 

 floor is very bowldery and swampy, scarcely any of it being fit for cultivation. At Lyons 

 Grand River has built a large alluvial fan, which extends up as well as down the channel for 

 some distance; it is this deposit that has crowded Maple River over against the north bank 

 at Muir. Stony Creek has done the same 2 miles above Muir. The fan at Lyons also keeps 

 Grand River to the north side of the valley for a mile or two west. From Lyons westward the 

 lower parts of the channel floor have been silted up by the river, leaving only the tops of gravel 



