106 THE MICHIGAN ACADEMY OF SCIENCE. 



being about south thirty degrees west, .and others about south sixty-five 

 degrees to seventy degrees west. A possible relation to the several 

 movements of the Labrador ice field was discussed before the Academy 

 in 1902 by W. H. Sherzer, whose paper has since appeared in the Jour- 

 nal of Geology. It was suggested by Sherzer that large grooves bear- 

 ing south thirty-eight degrees west are referable to the Illinoian stage 

 of giaciation ; that rather light striae bearing south sixty-eight degrees 

 west are referable to the lowan stage ; that a stronger set of striae bear- 

 ing about south thirty degrees west are referable to the Wisconsin when 

 at its greatest extension, while striae bearing about north thirty degrees 

 west are connected with the last moraine formed in that region. The 

 value of these suggestions has yet to be tested. 'This succession of ice 

 movements appears to harmonize well with the several borders to which 

 each is referred. 



LOBATIOX OF THE ICE MARGIN. 



A prominent lobation of the ice margin and disposition of the mo- 

 raines in great loops encircling the southern ends of the large basins 

 was clearly brought out by Prof. T. C. Chamberlin some twenty-five 

 years ago, together with the reasons for such lobation. (See Biblio- 

 graphy, page 109.) The thicker mass of ice in the basins and the smaller 

 resistance to ice movement there than would be found on the bordering 

 highlands naturally resulted in the extension of the ice sheet in the line 

 of the basin. Chamberlin drew illustrations from the southern penin- 

 sula of Michigan, and showed that the Lake Michigan basin, the Sagi- 

 naw basin, and the Huron-Erie basin were at a certain stage of giacia- 

 tion each occupied b}' distinct lobes of ice which formed prominent 

 morainic systems concentric with their respective basins. The moraines 

 of Michigan illustrate more clearly, perhaps, than those of any other 

 region the lobing of the ice margin. In addition to the great lobes just 

 mentioned there are found to be small morainic loops bordering narrow 

 tongues of ice. These are well displayed on the borders of the finger 

 like lakes along the east shore of Lake Michigan from Manistee north- 

 ward and back a few miles from the shore of Lake Huron from Macki- 

 nac to A]})ena. The tongues were from two to twenty miles long, and 

 but one to five miles wide. The headlands which come out to Lake 

 Michigan and rise 200 to 300 feet above the lowlands and the tracts of 

 corresponding prominence west of Alpena that pi'oject toward Lake 

 Huron ap])ear to be accunnlntions betwren such susall ice tongues. 



STRUCTURE OF THE DRIFT IX- ^MICHIGAN. 



The structure of the drift is more variable in Michigan, both on the 

 surface and below, than in a large part of the neighboring states of Ohio, 

 Indiana and Illinois. In those states the till or commingled drift 

 greatly preponderates over sand and gravel, and contains a large per- 

 centage of fine clayey material. In Michigan sand and gravel form a 

 notable part of the drift material, and much of the till is loose textured. 

 This great amount of loose textured drift seems attributable to the 

 excessive glacial drainage resulting from the convergence of the ice 

 lobes. It is best developed in the high portions of the State which were 

 built up between the ice lobes. In the plains next to the lake basins. 



