CHAPTER VII. 

 THE SAGINAW LOBE. 



By Frank Leverett. 

 GENERAL RELATIONS. 



The axes of movement of the Lake Michigan, Saginaw, and Huron-Erie lobes converge 

 toward northwestern Indiana, the Lake Michigan movement having been southward in the 

 general trend of the Lake Michigan basin, the Saginaw southwestward through and beyond 

 Saginaw Bay, and the Huron-Erie westward through the Lake Erie basin into Indiana. As a 

 result of the convergence a coalescence, more or less complete, was effected and was maintained 

 until destroyed by a rapid recession of the Saginaw lobe from the district south of the Kan- 

 kakee. This coalescence has thus far made it unnecessary to make more than a passing refer- 

 ence to the several ice lobes. 



A study of the moraines of northern Indiana and southern Michigan (see Pis. VI and VII) 

 has shown that the portion of the ice sheet which moved southwestward from the Saginaw basin 

 into Indiana melted back and disappeared from northern Indiana while the Lake Michigan and 

 Huron-Erie lobes still extended into that State. This perhaps is not surprising, for the path 

 of the Saginaw lobe, especially the part beyond the immediate basin of Saginaw Bay, was across 

 more elevated country than the paths of the bordering lobes. Its thickness must have been 

 correspondingly less and its movement correspondingly weaker, and these differences would 

 become more noticeable with the waning of glaciation and the decrease in the bulk of the ice 

 sheet. 



It is somewhat surprising to find that several strong moraines were formed by the Saginaw 

 lobe as it melted back from the border of the Kankakee basin into southern Michigan. Yet 

 this may not be inconsistent with its comparative weakness. The convergence of the three ice 

 movements might, at the culminating part of the Wisconsin stage of glaciation, have caused an 

 excessive loading with drift material in the part of the ice sheet which subsequently became 

 differentiated into the Saginaw lobe. This excessive loading may indeed have been even more 

 influential than the comparative thinness of the ice in bringing about weakness of movement. 

 However this may be, the fact remains that moraines that seem referable to the Saginaw lobe 

 appear at intervals of only a few miles all the way back from the eastern edge of the Kankakee 

 basin across St. Joseph, Marshall, Kosciusko, Elkhart, Noble, and Lagrange counties, Ind., and 

 Cass, St. Joseph, and Branch counties, Mich. 



The great line of glacial drainage at the junction of the Lake Michigan and Saginaw lobes, 

 now traversed by St. Joseph River and its tributaries in Kalamazoo, St. Joseph, and Cass 

 counties, Mich., to South Bend, Ind., and beyond South Bend by the Kankakee basin, breaks 

 the continuity of the moraines, and being in a reentrant angle, increases the difficulties of 

 correlating the individual moraines of the two lobes. A peculiar bunching or increase in bulk 

 of moraines on the southeast border of the glacial drainage plain seems to indicate that the 

 influence of the Lake Michigan lobe was felt even on that side. Illustrations are found south 

 of South Bend and Bristol, Ind., and White Pigeon, Mich. As a rule, however, the moraines 

 on the southeast were formed by the Saginaw and those on the northwest by the Lake Michi- 

 gan lobe. 



As a result of the recession of the Saginaw lobe, that part of the ice field came to have a 

 position at the head of a recess between the Lake Michigan and Huron-Eric ice lobes, and it 

 seems almost a misnomer to speak of it as a lobe during this early part of its differentiation. 



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