196 PLEISTOCENE OF INDIANA AND MICHIGAN. 



INTERLOCKING MORAINES OF THE SAGINAW AND HURON-ERIE LOBES IN 

 SOUTHEASTERN MICHIGAN. 



The "thumb" or southeastern watershed of Michigan, the high divide draining on the east 

 into Lake St. Clair, Detroit Kiver, and Lake Erie and on the west into Lake Michigan and 

 Saginaw Bay, has a rock nucleus but is also occupied by a prominent system of interlocking 

 moraines formed between the Saginaw and Huron-Erie lobes. Moraines of Wisconsin age are 

 to some extent superimposed upon moraines of an earlier (Illmoian) stage of glaciation, for the 

 lobation of the ice in the earlier stage naturally was governed by topography in a manner 

 similar to that in the later stage. 



Many years ago, in the Douglass Houghton reports of the first Michigan Survey, the lead- 

 ing topographic features of the divide were so described as to lead one familiar with modern 

 interpretation to infer that it consisted of strong moraines. Years later the system of moraines 

 was recognized and its general features were discussed by Chamberhn, 1 who termed it an inter- 

 lobate moraine of the Saginaw and Western Erie lobes and who demonstrated its relation to the lobes 

 of the great Labrador ice sheet. It was not, however, until detailed studies were made by the 

 present writer that the presence of moraines and drift ridges of pre- Wisconsin age was noted, 

 or that it was determined that the drift, instead of being a single massive moraine traversing 

 the entire length of the district between the Saginaw and Huron-Erie ice lobes, consists of 

 several interlocking moraines leading up from either side at such angles as to form a reentrant 

 in which the drift is heaped up. This heaping up, repeated in the several moraines which 

 interlock in succession from southwest to northeast, constitutes what is here termed the inter- 

 lobate mOrainic belt. 



The moraines of the interlocking system in northern Indiana and southern Michigan have 

 already been discussed in connection with the development of earlier moraines of the Saginaw 

 lobe. The present discussion, therefore, begins in southern Jackson County, Mich., where the 

 outer moraine of the Kalamazoo system of the Saginaw lobe connects with the correlative 

 moraine of the Mississinawa system of the Huron-Erie lobe, and extends northeast to southern 

 Lapeer County, north of which no entanglements are found. The entire length of the system 

 in Michigan is 150 miles and its width 25 miles. 



DISTRIBUTION AND CHARACTER. 



At the place of interlocking flat outwash aprons and' lines of glacial drainage strikingly 

 contrast with the sharp knobs of the moraines with which they are connected. When the 

 southwestern end of the interlocking system was forming the reentrant in the ice border appears 

 to have been slight, but with the development of the system it became more marked. As 

 in northeastern Indiana, the Saginaw lobe receded more rapidly than the Huron-Erie lobe, 

 but the reentrant between the lobes receded still more rapidly than the end of the Saginaw lobe, 

 and the Saginaw lobe consequently is more clearly defined in the later than in the earlier moraines 

 of the interlocking system. 



, The Kalamazoo system of the Saginaw lobe connects with its correlative of the Huron- 

 Erie lobe in southern Jackson County in the vicinity of Hanover, which stands on a small 

 gravel plain in the reentrant between the two ice lobes. North of the village is a moraine 

 of the Saginaw lobe and south and east of it a moraine of the Huron-Erie lobe. The morainic 

 spur developed at the junction is more prominent than either moraine and extends northeast- 

 ward to a point about 6 miles south of Jackson where it terminates in a kame that stands 200 

 feet above Grand River, which flows at its northern base. The spur carries numerous knolls 

 50 to 75 feet high in groups or in short belts between which are lower tracts with small knolls. 

 At the northeast end of this prominent morainic spur a gently undulating till tract cover- 

 ing an area of about 30 square miles extends from the southern line of Jackson County north- 

 ward within 3 or 4 miles of the city of Jackson and eastward about to Brooklyn and Napoleon. 



1 Chamberlin, T. O, Preliminary paper on the terminal moraine of the second glacial epoch: Third Ann. Rept. XJ. S. Geol. Survey, 1883, p. 328. 



