LATER MORAINES OF LAKE MICHIGAN, SAGINAW, AND HURON-ERIE LOBES. 283 



STRUCTURE OF THE DRIFT. 



From Inilay to Romeo the moraine is generally bowldery on the surface, but is composed 

 largely of clay beneath, though it comprises several gravel deposits in the form of kames, the 

 most notable ones being in sees. 33 and 34, Imlay Township, and sec. 35, Aimont Township, and 

 several smaller ones between Aimont and Romeo. The strong ridge back of Romeo is composed 

 mainly of stony clay but has kames and much sandy outwash along its west front in the north- 

 ern part of Washington Township. Southward from Rochester the ridge is composed more 

 generally of clay. 



GLACIAL DRAINAGE. 



As nearly all the moraines of the Huron-Erie slope in Michigan are water-laid, there is rela- 

 tively little ice-border drainage to discuss. Mr. Leverett has described that associated with the 

 Defiance moraine farther south (p. 281), and the writer has discussed the relation of the Imlay 

 outlet to the moraines that border upon it (p. 277). What remains is ruainly drainage associated 

 with the Birmingham moraine. 



ALMONT CHANNEL. 



As Mr. Leverett has pointed out, the Defiance moraine pressed against the earlier deposits in 

 the vicinity of Amy, 4 or 5 miles east of Pontiac, and interfered with the southward drainage from 

 the interlobate angle in Lapeer County. This interference led to the development of a line of 

 glacial drainage that went northward through eastern Dryden Township, Lapeer County, 

 turning northwestward a mile northeast of Dryden. The channel is very plain in southern 

 Attica Township, where two or three branches follow narrow courses between high morainic 

 knolls. 



A small, narrow channel, known as the Aimont channel, opens out of the eastern branch in a 

 nearly reverse direction or a little south of east. It is commonly not over 400 or 500 feet wide 

 and to Aimont is rather crooked. Its course and character and relations as far as Romeo have 

 already been described (p. 281). West of Romeo it passes into the broad Rochester channel, 

 which lies in front of the strongly developed part of the Birmingham moraine, but for 4 or 5 

 miles it keeps in its narrow bed, with the outwash rising 40 to 50 feet above it; finally it loses 

 its identity in a swamp in the southwest part of Washington Township, Macomb County. 



At its head in sec. 26, Attica Township, Lapeer County, the altitude of the Aimont channel 

 is 8S0 or 890 feet, at Aimont about 830 feet, west of Romeo about 810 feet, and in southwestern 

 Washington Township 800 feet. Its length is about 20 miles and its descent 80 to 90 feet. 

 Allowing for subsequent tilting of the land, its original descent was 60 to 70 feet, for the river 

 flowed toward the south. 



ROCHESTER CHANNEL. 



A valley about a mile wide begins about 2 miles west of Romeo and extends southwest along 

 the west or front side of the strongly developed part of the Birmingham moraine to Birmingham. 

 A mile or two southwest of the latter place it opfens out onto the eastward slope of the old lake 

 bottom below the highest beach of Lake Maumee. Throughout its 20 miles of length it maintains 

 a constant relation to the Birmingham moraine. Its character and relations strongly suggest 

 that it is a fragment of a large glacial drainage channel, and it is here termed the Rochester 

 channel. 



Its connections and relations to other drainage, however, are obscure, its greatest peculiarity 

 being its abrupt termination at its north end, where it is 1£ miles wide and where, except for its. 

 narrow entrance, it is surrounded on the east, west, and north by morainic deposits that rise 

 100 feet or more above it. The sandy and gravelly deposits on its floor are not smoothly laid, 

 like the floors of most drainage channels, but show considerable irregularity. For 4 or 5 miles 

 from the north end it is filled with sandy outwash from the Birmingham moraine to a level of 

 840 to 860 feet, which is considerably higher than its general level farther south. Between 

 Rochester and Birmingham it is again filled with a wide flat deposit of outwash up to 810- to 

 815 feet. Near its north end it has swampy areas, which he below 800 feet and which seem to be 

 original depressions not scoured out by a river. Nevertheless, it seems much like the channel 



