GEOLOGICAL AND NATURAL HISTORY SURVEY, 11 



4. Coarse sand, not calcareous • 6 to 12 



5. Calcareous loam 3 



6. Yellow clay, very calcareous, with leaves im- 



bedded • . . 3 



7. Carbonaceous band, not calcareous • • . . 2 



8. Yellow calcareous clay, similar to No. 6 4 to 6 



9. Band of carbonaceous material, not calcareous. . 2 



ID. Brown sand, with twigs and peaty material 8 to 10 



II. Water bearing sand and talus-covered slope 8 



Height of blufif 20 to 22 feet. 



The calcareous clays, Nos. 6 and 8, of the last section, and 

 Nos. 6 and 7 of Dr. Marcy's section, contain numerous gasteropod 

 shells. Dr. Marcy has collected a large number of shells from this 

 horizon, among which there are Unios, apparently of several dif- 

 ferent species, but not specifically identified. Mr. C. T. Simpson 

 has identified nine different genera of mollusks, all of existing 

 species, found in No. 7 of Dr. Marcy's section. Planorbis and 

 Lymnea are very abundant. Prof. D. P. Penhallow has identified 

 tw^o w^ood specimens, one a new species of Picea (Picea Evanstoni), 

 the other a new oak (Quercus Marcyana) (i). The bone .of the 

 deer, found by Dr. Marcy, is a portion of the femur. The writer 

 has found many localities in the sandy portions of this beach, where 

 molluscan shells abound. Nearly every exposure in the sandy dis- 

 trict west of the beach, from the main part of the city of Chicago 

 southward to Englewood exhibits them. This beach is, therefore, 

 in striking contrast with the two higher beaches, which contain 

 few remains of aquatic life. 



An excellent artificial section across this beach, made by the 

 Fullerton avenue conduit, which leads from the Chicago River 

 eastward to Lake Michigan, across the north part of Chicago, is 

 discussed above. The deposit throughout is mainly sand, 

 but some gravel is encountered. Shells of Unios and other mol- 

 lusks were noted at frequent intervals throughout nearly the whole 

 width of the deposit. Beneath these beach deposits there is every-' 

 where a pebbly blue-gray clay, apparently an unmodified glacial 

 till. Some of the sewer' ditches in Hyde Park, west of Grand 

 boulevard, have reached peat deposits below sand, at a level a few 

 feet above the lake. Wood has often been found in the sand west 

 of this beach in Chicago. 



Reference has been made to the beachlets which occupy the 

 interval between the main beach and the present shore of the lake. 

 (1) Trans Royal Society of Canada, 1891, pp. 39-32, plate II. 



