THE LIFE OF GLACIAL LAKE CHICAGO 93 



Four feet of fine, almost impalpable clay cover this sand deposit, indicating 

 that the water at this later stage was heavily filled with sediment. No life 

 was observed in this stratum. 



c. Near Calumet Lake 



South of Calumet Lake, near 130th Street, east of the Michigan Central 

 Railway tracks, a number of mollusks were found beneath Indian graves. 

 They are believed to be referable to the Hammond stage. Six species are 

 represented. 



Fusconaja undata Eurynia recta 



Quadrula pnstulosa Lampsilis ventricosa 



Elliptio gibbosus Goniobasis livcscens 



G. LOW WATER STAGE — THE CHAMPLAIN SUBMERGENCE 



The continued recession of the ice to the northeast eventually uncovered a 

 low pass thru Lake Nipissing and the Ottawa Valley and the lake waters fell 

 upwards of 60 feet, 60 forming a three-lake condition. At the same time the 

 land to the east was submerged and the sea entered the St. Lawrence basin, 

 forming two arms, the southern arm extending well into the Ontario basin and 

 the northern arm entering the Ottawa Valley. Oxidized silt beds overlying 

 the deposits of the Hammond stage are believed to represent this low water 

 stage, at which time all of the land covered by the lake waters was made dry. 

 As no evidence of terrestrial (or other) life have been found in this stratum 

 it is to be presumed that the low water stage did not endure long enough for a 

 fauna and flora to develop or migrate from the south. 



H. THE ENGLEWOOD STAGE 61 



Continued uplift in the northern portion of the Nipissing outlet raised the 

 level of the lakes until they again overflowed southward thru the St. Clair 

 River, producing a condition known as the two-outlet stage. The lakes at 

 this stage are also known as the Nipissing Great Lakes, the area covered being 

 but little greater than that of the present Great Lakes. In the Chicago region 

 the waters rose to about twelve feet above the present level. The shore lines 

 of this stage "are characterized by an exceptionally strong development of cut 

 bluffs and terraces, rather than by beach ridges. In this manner they express 

 the vigorous encroachment of a lake which was rising upon its shores. " 62 



During the Englewood stage (Plate XLIV) the shores of the lake differed 

 little in position from those of the two preceding stages, except in the northern 

 region. Wilmette Bay (Plate XLV) became much smaller; the Graceland 



81 Goldthwait (Records of Extinct Lakes, p. 66) suggests a sea-level stage. 

 n See foot-note page 90. 



82 Goldthwait, Records of Extinct Lakes, p. 67. 



