DEPOSITS OF THE LAKE CHICAGO BASIN 



61 



No record was kept of the stratum from which these shells came, but they 

 are believed to be referable to the Hammond stage of Lake Chicago. 6 

 Corner of West Monroe and Morgan Streets 

 Unio shells" 



Chicago Heights 

 The tooth of a mammoth (Elephas columbi) was found in the bank of Wal- 

 lace Creek, at a depth of 18 or 20 feet. 7 This creek flows in the Valparaiso 

 moraine in which it has sunk its bed for twenty feet or more. The tooth was 

 probably washed from a higher source. It is impossible to determine with 

 just which lake stage the fossil is to be correlated; it is, however, certainly 

 postglacial. 



IV. Typical Sections of Beaches 



A. GLENWOOD BEACH 

 Haas' gravel pit, Oak Park. Surface 625 feet A.T.; 45 feet A.L.M.* 



Strata 



Deposit 



Depth 



1 



Brown-stained gravel, capping summit 

 and slope 



18-30 inches 



2 

 3 



Fine gravel, fresh or stained but little . , . 



Sand, very thin at top, but increasing 



toward side of bar 



24-48 " 

 0-36 " 



4 



Fine gravel, increasing like no. 3 



0-48 " 



5 



Fine gravel, nearly 4 feet in thickness, 

 which passes upward from near the east 

 side of the excavation, assuming a near- 

 ly horizontal position beneath the crest 

 of the ridge 



40-48 inches 



6 



Sand, thickening toward the higher part 

 of the ridge 



6-36 " 





1 





5 It is exceedingly unfortunate that systematic records and collections were not made 

 when the large drainage canal was being excavated. Its entire length is in the bed of the old 

 outlet, and, judging by the fragmentary records which are obtainable from this region, it 

 undoubtedly presented quite as fully the biological history of Lake Chicago as did the strata 

 uncovered in the north shore channel. 



6 Higley and Raddin, p. XV. It is not known from what horizon these specimens were 

 obtained. 



7 Collected by Mr. James H. Knapp. Identified by Dr. O. P. Hay. 



' Leverett, Pleistocene Features, p. 70. This section is on the Oak Park spit and not 

 in the beach proper, which attains an elevation of 50 feet. 



