42 2 JAMES WALTER GOLDTHWAIT 



sidered, that there has been the same confusion of terraces mentioned 

 in connection with the strong bluffs near Algoma, Wis. — the upper 

 few feet of the Nipissing terrace in many places having been stripped 

 away at a slightly lower stage. The Nipissing plane, then, seems to 

 be horizontal, and about 14 feet above the present lake-level in the 

 southern parts of both the Huron and the Michigan basins. 



THE LAKE CHICAGO SHORE-LINES 



The terrace of the Calumet or 40-foot shore-line of Lake Chicago, 

 traced by Alden near Belgium, Wis., was followed with some difficulty 

 almost to Sheboygan. For most of this distance it is ill-defined, 

 occasionally giving way to low bars; and its height seems in places 

 to reach 49 feet. With a mile of the northern border of the Port 

 Washington sheet, and again east of Oostburg, a gravel ridge was 

 found 63 feet above the lake. If these fragments mark the Glenwood 

 or 60-foot stage of Lake Chicago, they are important in extending 

 that stage northw^ard nearly to Sheboygan, where broad flats of strati- 

 fied sand stand 60 feet above the lake. The Belgium and Oostburg 

 63-foot beach fragments are also important in showing that the Glen- 

 wood level persisted after a certain re-advance of the Michigan ice- 

 lobe, which seems to have buried Glenwood beach gravels beneath a 

 deposit of red clays near Milwaukee.' The fact that both the 60- 

 and 40-foot beaches appear interruptedly nearly as far as Sheboygan, 

 and there seem to end near a belt of rather strong morainic topography, 

 when seen in the light of Taylor and Leverett's studies on the eastern 

 side of the lake, suggests a re-advance of the ice in the vicinity of 

 Manitowoc and Manistee, Mich., at the close of the 40-foot stage, 

 overrunning for an unknown distance the northern part of the 60- and 

 40-foot beaches and destroying them. Further study of the beaches 

 and moraines on both sides of Lake Michigan should make this point 

 clear. So far as measurements were obtained on these Lake Chicago 

 beaches, they seem to indicate a horizontal attitude, at least as far 

 as Racine. It is possible that they rise a few feet between Racine 

 and Oostburg. 



I "The Delavan Lobe of the Lake Michigan Glacier," etc., U. S. Geological Sur- 

 vey, Professional Paper No. J4, by W. C. Alden, p. 69 (1904). 



