MORAINIC SYSTEMS AT HEADS OE LAKE MICHIGAN AND SAGINAW BASINS. 213 



b}' narrow swampy tracts. There are also slight offshoots in places, a few rods in length. The 

 greatest complexity is found in sec. 1, Whiteoak Township. The height of the ridges ranges 

 from 15 feet to about 40 feet. 



The portion of the esker in Livingston County is of coarser material than that in Ingham 

 County; in Livingston County cobble is in places mixed with the gravel, and in Ingham County 

 sand is mingled with it. 



IOSCO ESKER. 



About 2 miles east of the southern part of the esker system just described a disjointed 

 chain of short eskers leads west of south from sec. 29, Handy Township, to sec. 19, Iosco Town- 

 ship. The portions in sees. 29 and 32, Handy Township, are in the midst of an isolated tract 

 of knolls that lies north of the Charlotte morainic system, its southern end being separated 

 from the inner border of the moraine by a till plain over a mile in width. In sec. 5, Iosco Town- 

 ship, the esker runs out onto this till plain and is broken by a marshy gap about a mile in width. 

 It reappears in sec. 7, Iosco Township, and continues as disjointed ridges as far south as sec. 

 19, where it terminates in the midst of the Charlotte morainic system with a small sandy expan- 

 sion, possibly a delta. 



OAK GROVE-HOWELL-CHILSON ESKER SYSTEM. 



The Oak Grove-Howell-Chilson system is apparently a combination of two and possibly 

 three eskers in an end-to-end series. (See PL XL) The southernmost and probably the oldest 

 leads from near Howell Junction or Ann Pere southward toward Chilson, but the depression 

 in which it lies continues northward past Thompson Lake in the east part of Howell to the 

 southern end of another well-defined esker which extends along the valley of Bogue Creek 

 for 4 or 5 miles. Beyond a space of a mile or more along Bogue Creek is without esker ridges, 

 but at Oak Grove a chain of esker ridges begins and is traceable northward for 2 miles. 



The combined length of the series is 14 or 15 miles. The jDortion between Howell Junction 

 and Chilson consists of disjointed ridges for about a mile, but from near the center of sec. 7, 

 Genoa Township, a nearly continuous ridge extends to the east part of sec. 19. It is very 

 winding in its course through sec. 18, but maintains a general trend about S. 20° E. Its height 

 ranges from 10 to 20 feet and its width from 50 to 75 yards. Near its southern end a fanlike 

 expansion plane, except for basins and surrounded by an extensive swamp a few feet lower, 

 covers the southwest part of sec. 20. The swamp in turn is surrounded by prominent morainic 

 hills, and the morainic topography extends north nearly to Howell along the east side of the 

 esker. In the line of continuation of this esker system, and possibly related to it, in the por- 

 tion of the moraine west and southwest of Chilson, there is a chain of prominent kames, three 

 of which reach 1,100 feet and a fourth 1,060 feet above sea level. The esker trough reaches 

 920 to 950 feet in the portion south of Ann Pere. 



The esker along Bogue Creek has a fanlike expansion at its southern end, in sec. 25, Howell 

 Township, where also it is developed into a plexus of ridges. With tins exception it is gen- 

 erally a single ridge, though in parts of sec. 19, Oceola Township, it consists of two parallel 

 ridges side by side. The sag or depression followed by the esker is swampy along much of its 

 length, though in places Bogue Creek has cut down sufficiently to drain the swamp. This 

 swamp is at the western edge of a complicated network of swamps that covers the western 

 third of Oceola Township and appears to mark the lines of subglacial drainage in the plain 

 north of the great interlobate moraine whose inner border comes up to Howell. These features 

 are shown quite clearly on the Howell topographic sheet. Several exposures on the borders 

 of these sloughs and swampy tracts show a thin deposit of till resting on sand and gravel and 

 possibly consisting of englacial material deposited during the withdrawal of the ice and the 

 contemporary deposition of the esker ridge. 



Most of this esker along the Bogue Creek valley is not regular but is bead-shaped — bunched 

 up in places connected by very weak, low ridges. Parts of it, however, in sec. 18, Oceola 

 Township, form typical esker ridges 10 to 20 feet high. On the line between sec. 12, Howell 

 Township, and sec. 7, Oceola Township, the ridge is 30 to 40 feet high and in places nearly one- 



