DEPOSITS OF THE LAKE CHICAGO BASIN 



57 



reserve line of the Illinois and Michigan canal in Sec. 14, T. 37 N., R. 11 E. 

 of the 3rd P.M. to the north and south center line of Sec. 32, T. 37 N., R. 

 14 E. of the 3rd P.M.) a length of over 16 miles. The channel is cut in both 

 rock (western end) and dirt (eastern end); the deposits consist of peat, clay, 

 sand, gravel, and boulder clay. The depth of the channel is about 34 feet. 

 The channel is cut thru the center of the southern arm of the outlet of 

 glacial Lake Chicago, which separated Mount Forest island from the main part 

 of the Valparaiso moraine. The cut should, therefore, clearly reflect the history 

 of the postglacial waters of the Chicago basin, and, except for the physical 

 differences, this history should agree with that shown in the cut of the north 

 shore channel. The physical differences, however, were considerable, the 

 north shore channel being cut thru an old embayment of the lake, while the 

 Calumet-Sag channel is partly in one of the old outlets, which was a large 

 river almost a mile in width. A section of the channel at West 92nd Avenue 

 exhibited the strata shown below. 



Calumet-Sag channel at west 92nd Ave. Surface 593.5 A. T.; 13.5 A.L.M. 

 (Plates XXVI, XXVII) 



Strata 



Deposit 



Depth 



Remarks 



rx 



Surface soil; oxidized peat 



24 

 114 



12 



48 

 24 



51 



2 

 65 

 78 



408 





VIII 



Peat, almost pure 



Shells and plants, especially in 



lower part. 

 Pockets of shells in lower part. 

 Upper part impalpable clay. 

 But few shells. 



VI I 



Peaty clav 



VI 



Clav, sandy in lower part 



V 



Fine gray sand 



IV 



Fine sand, coarse sand and fine 

 gravel; sand cross bedded in 

 some places; lenticular pockets 

 of fine gravel, shells, and wood, 

 apparently beach worn 



Some large stones and a few naiad 

 shells. 



Naiad shells on surface. 



III 



Boulders, clay, sand, pebbles; 



boulder pavement on top of 



till 



II 



Boulder clay 



Very hard. 



I 



Niagara limestone 





Total thickness.... 



=34 feet. 



Elliplio crassidens 

 ' ' gibbosus 



BIOLOGICAL REMAINS 



Stratum III 



Campeloma integrum 



'' integrum obesum 



