MORAINIC SYSTEMS AT HEADS OF LAKE MICHIGAN AND SAGINAW BASINS. 197 



It is traversed nearly centrally by a sharp gravelly ridge, 30 or 40 feet high and about 7 miles 

 long, which leads from the south side of Wolf Lake southwestward to the middle of the morainic 

 spur. This ridge is a little broader than a typical esker, being in places nearly one-eighth 

 mile in width, but it appears to have been developed by the same process and to be referable 

 to the esker class. Like the morainic spur it seems to He very nearly along the Hue of junction 

 between the Saginaw and the Huron-Erie lobes. 



From the till plain just described northward past the Michigan Central Railroad and 

 eastward about to the line of Jackson and Washtenaw counties there is a gravel plain, known 

 as the Grass Lake Plain, which rises on the north into a prominent moraine of the Saginaw 

 lobe and on the east into a prominent moraine of the Huron-Erie lobe. It carries numerous 

 basins and connecting sloughs so that only a small part of its surface is up to the level of the plane 

 of deposition. At its northeastern end it extends as a narrow strip scarcely a mile wide for 

 2 or 3 miles into the midst of the coalesced morainic belt and has its head a mile north of Kava- 

 naugh Lake at the base of Sugarloaf Knob in sec. 32, Lyndon Townsliip, Washtenaw County. 



The moraines which border the Grass Lake Plain form a prominent spur about 5 nules 

 wide, from their point of union in northwestern Washtenaw County northeastward about to 

 Pinckney, in southern Livingston County, a distance of perhaps 10 miles. Part of it is within 

 the limits of the Ann Arbor quadrangle. The area of the spur is called by the residents the 

 "short-hill district," because its thickly set knobs give short but sharp gradients to the roads 

 which traverse it and have very little level surface. It is also thickly set with basins, the 

 largest of which are nearly a mile m longest diameter and one-fourth to one-half mile in width. 

 A number of them contain lakes, some of which are reported to have depths of 75 feet or more, 

 with water surfaces fully 100 feet below the highest neighboring parts of the moraine. The 

 land surface outside the lakes in this morainic spur has a range of about 200 feet in altitude, 

 or from 900 to 1.100 feet above sea level. 



From the northeast end of the interlobate spur eastward across southern Livingston County 

 clusters of sharp kames and interspersed gravel plains (see Howell and Ann Arbor topo- 

 graphic sheets) converge toward a gravel plain which leaves Huron River near Portage 

 Lake and leads westward as a prominent line of glacial drainage past Pinckney and around the 

 north end of the interlobate spur to the Portage Swamp, in northeastern Jackson County. The 

 kames rise 100 to 150 feet above the gravel plain and are distributed on both sides of Huron 

 River. Those on the north side appear to pertain to the Saginaw and those on the south side 

 to the Huron-Erie lobe. Back of them on either side of the river are bulky moraines, the one 

 on the north being the probable continuation of the Charlotte system of the Saginaw lobe, and 

 the one on the south belonging to the Huron-Erie lobe, which in northeastern Indiana includes 

 the Mississinawa, Salamonie, Wabash, and Fort Wayne moraines, and in Michigan, from a 

 point near the limits of the Ann Arbor quadrangle northward, the Defiance moraine. The 

 kames were probably formed while the lobes were nearly coalesced over the portion of the 

 Huron Valley east of Pmckney, but the moraines back of them appear to have been formed 

 after the lobes had become sufficiently separated to permit glacial drainage to flow between 

 them. 



Near Milford, in southwestern Oakland County, as shown on the Milford topographic 

 sheet, another interlocking of moraines indicates that the two lobes were for a time coalesced 

 down to that point while separated along the portion of the Huron Valley just below. In pass- 

 ing through these interlocking ridges Huron River is obliged to make a series of long curves. 

 The ice border after a time shrank away from these interlocking ridges and receded north and 

 south as well as northeastward. As it receded outwash aprons were formed on its borders, 

 those north of Milford being connected with a strong moraine of the Saginaw lobe and those 

 east and south of Milford with the Huron-Erie lobe. A prominent sandy plana east of Milford, 

 known as Commerce Plain because it covers much of Commerce Townsliip, and its continua- 

 tion down Huron River are both much lower than the outwash plains north of Milford, for 

 the latter are held up by the series of interlocking ridges near that village, through which only 

 narrow gaps lead into the Huron Valley. 



