LATER MORAINES OF LAKE MICHIGAN, SAGINAW, AND HURON-ERIE LOBES. 275 



The significance of this channel in the lake history is largely problematic, for it is only an iso- 

 lated fragment cut off from direct connection with the only glacial lake that can be supposed to 

 have been connected with it. The river that made it must have been fully as large as the Imlay 

 outlet river, for its proportions resemble those of the larger sections of the latter — those, for in- 

 stance, between Richfield and Flint in Genesee County. It is one of those suggestive fragments 

 which shows the complexity of the lake history without shedding a clear light on the events con- 

 nected with its origin. 



North and west of Imlay a rather high, bulky moraine has crowded westward into the Lum 

 channel, closing it entirely and cutting off all southward extension, unless one be found in the 

 somewhat doubtful Rochester channel (p. 283). At its northwest end in northern Deerfield 

 Township the Lum channel opens into the Imlay channel, and no certain indication of its course 

 farther west has been found, though it is possible that the extra width of the Imlay channel 

 above Columbiaville represents its continuation. The slope is northward, for railroad profiles 

 show altitudes of 871 feet at Lum and 861 at Kings INIills and both stations are 4 or 5 feet above 

 the channel floor. Toward its south end the floor of the channel contains much outwash, and 

 near Kings Mills it is swampy and covered with peat. 



The altitude of the highest Maumee beach at Imlay is 850 feet and near Goodland Church 

 about 855 feet. From this it appears that the Lum channel could have served as the outlet of 

 glacial Lake Maumee only if the land in Lapeer County stood at that time lower relatively to the 

 land at Fort Wayne, Ind., than it did a little later during the operation of the Imlay outlet. In 

 that event it may have become the outlet at the time of an extreme backstep in the oscillations 

 of the ice front, and the beach made then may have been completely overridden and destroyed as 

 far south as Birmingham by the readvance of the ice to the Birmingham moraine. It is this 

 same Birmingham moraine that closes the Lum channel northwest of Imlay and forms the 

 eastern boundary of the Rochester channel farther south. 



Although it is not possible at present to make sure of its relations to the lake history, it 

 seems almost certain that the Lum channel, including probably the Rochester channel as a part 

 of the same line, marks the establishment of a full-volume discharge for Lake Maumee before the 

 time of the Imlay outlet and during the early part of the time when the western front of the 

 retreating Lake Huron ice lobe was oscillating back and forth across this critical area. The 

 beach of Lake Maumee, which was the correlative of the Lum channel, has not been identified. 



IMLAY OUTLET CHANNEL. 



MAIN IMLAY CHANNEL. 



General character. — The Imlay channel west of Lapeer County was described in connection 

 with the glacial drainage of the eastern limb of the Saginaw lobe (p. 254). The head of the chan- 

 nel has generally been described as being a mile or two south of Imlay, and it was in fact there 

 during the last stages of Lake Maumee. But when the channel was first established through 

 eastern Lapeer County its head was 7 or S miles farther south, or about at Almont; and this 

 short length of the channel, which really belongs with the moraines of the Huron-Erie slope, 

 may as well be described here. 



From Almont to North Branch the Imlay channel is bounded on the east by a moraine 

 which, though a slender individual, is nevertheless through most of the distance quite clearly 

 and strongly developed. It forms the immediate eastern bank of the channel throughout this 

 interval and except in one reach between Imlay and central Goodland Township is so closely set 

 against the channel that it seems to have been pressed forward to make the channel more narrow. 



The Imlay channel begins to have a definite floor 2 miles east of Almont. The floor is 

 swampy and contains more or less peat and marl nearly all the way from Almont to Imlay and 

 in this interval has a width of a third to a half mile, although at the level of the highest beach of 

 Lake Maumee it is generally a mile or more wide. North of Irnlay for 4 or 5 miles the moraine 

 stands back a little to the east, and the swampy channel floor holds a width of about one-half 

 mile. In the central part of Goodland Township the moraine presses in again more closely than 



