256 PLEISTOCENE OF INDIANA AND MICHIGAN. 



are cut off at the channel 2 or 3 miles east of Maple Rapids the bluffs are 80 to 90 feet high at 

 some points. 



The relations of the slender moraines of the deployed group to the Grand River channel show 

 clearly that practically all of the channel was excavated after the building of the moraines. 

 The gently curving lines which the moraines take in bending around from east and west courses 

 on the meridian of Lansing to north and south courses where they cross the channel show that 

 the floor upon which the ice moved was smooth and without any important depression trans- 

 verse to its front. All the moraines except the Owosso (pp. 243, 257-259) cross the channel with 

 little or no change in their trend. 



EARLY HISTORY. 



During the deposition of the early moraines of the deployed group the Grand River channel 

 was a shallow, ill-defined depression in the surface of the drift. But though it was shallow at first, 

 the drainage from the ice and the near-by land gathered into it and soon began to develop a 

 definite river bed. As has been pointed out above, there was no concentration of drainage on the 

 south side of the channel during the deposition of the first three moraines. On the north side 

 there was rather strong drainage along the ice border at all stages of the ice front, but it did not 

 follow the ice front all the way to the line of the Grand River channel during the formation of 

 the earlier moraines. It turned off at points 10 to 20 miles north of Ionia and ran southwest 

 down the course of Dickenson Creek and Flat River to the line of the Grand River channel at 

 Lowell. 



On the south side of the channel south of Ionia the plain between the Grand Ledge and 

 Ionia moraines for 1 to 2 miles back from the bluff is covered with a thin coating of gravelly out- 

 wash which was evidently deposited before the excavating of the deep channel was begun. Its 

 western part lies in front of the Grand Ledge moraine as this runs northward along the east side 

 of Berlin Township and may be outwash from the ice front at this halt, but its main body forms 

 an apron-like front to the Ionia moraine. From this moraine it slopes westward with decreas- 

 ing coarseness. 



It is possible, however, that this deposit belongs to the Portland moraine and was deposited 

 by a river coming from the north along the course of Prairie Creek. The valley of this creek 

 seems to indicate previous occupation by a larger stream, and there is a small gravel deposit on 

 its east bank north of Grand River. In this case it may be assumed that a large part of the 

 original deposit was cut away by the later making of the Grand River channel. 



A small gravel deposit on the brow of the bluff at the north end of the channel which passes 

 Collins was probably deposited by the first flow of the Lookingglass glacial river, which skirted the" 

 front of the Portland moraine. Another small deposit in this channel just east of Collins prob- 

 ably marks a late stage of this moraine, when the drainage was first diverted toward Lyons. 



No distinct evidence of outwash was observed in connection with the Lyons moraine; drain- 

 age from the north at that stage probably continued to follow the course of Prairie Creek. At 

 this stage the Lookingglass glacial river broke through the Portland moraine east of Collins and 

 joined the fine of the main channel at Lyons. 



During the making of these moraines the channel along the fine of drainage westward had 

 been progressively deepening eastward as the ice withdrew, and the advent of the larger volume 

 of the Lookingglass glacial river no doubt augmented this process. 



On the south side of the channel at Matherton a very well defined fan of outwash, deposited 

 on the edge of the plain, indicates the absence of any distinct channel there at that time. The 

 drainage which made this deposit appears to have come from the north, but it may have issued 

 directly from the ice. 



INCURSION OF THE IMLAY OUTLET RIVER. 



Prior to the formation of the great Imlay outlet the volume of drainage gathered along the 

 line of the Grand River channel was relatively small and the channel produced was of correspond- 

 ingly small magnitude and depth. When the Imlay outlet river first began to flow it entered 

 the Line of the Grand River channel just south of Maple Rapids. At that time the outlet river 



