14 PAUL MAC CI.INTOOK 



fore, in the present state of the investigation to refer it to the earliest glacia- 

 tion (Nebraskan). 



Recent studies by Leverett and Schoewe (unpublished data) have 

 shown a drift older and more extensive than the Kansan in Kansas and 

 western Missouri. Pre-Illinoian drift is found in southeastern Missouri 

 from St. Louis County southward to about the head of the gulf embayment. 

 The occurrence of old till in St. Louis County has been discussed by Dtu- 

 shell 1 and Fenneman 2 and more recently noted by Shipton and I Ianley, while 

 farther south, erratics on the uplands have been noted by Shaw, M. Weller, 



TABLE II 

 Limestone: 



Dense dark 14 . 3 



Soft ( Pennsylvanian ) 13 . 5 



Dense, few large crystals 2.3 



Crystalline 1.2 



Total 31.3 



Chert 19.4 



Sandstone ( Pennsylvanian ) 14 . 3 



Ironstone concretions ( Pennsylvanian ) 10 . 



Igneous rocks: 



Granite 4.0 



Greenstone 4.8 



Basalt 1.2 



Total 10 . 



Lime concretions ( Pleistocene ) 8.0 



White quartz pebbles ( Pennsylvanian ) 3.1 



Shale ( Pennsylvanian ) 2.0 



Quartzite ( brownish and gray ) 1.6 



Quartz (white, crystalline) 0.4 



Sauer, Flint, and Leverett. Rut in no place could the age of this older drift 

 be definitely determined. In Illinois it has been described from the bluffs 

 northwest of Alton, 3 but evidence in this case was not sufficient to determine 

 whether the drift belongs to the Keewatin or the I^abrador drift sheet. 

 Leverett has described 4 pre-Illinoian drift in Monroe County where, west of 

 Rock School (NE. ]/ A , Sec. 21, T. 3 S.. R. 10 W.), he found T feet of much- 

 indurated, massive till below 7 feet of softer Illinoian till. South of Rurkes- 

 vill station (near the center of Sec. 20), a roadcut descending the hill showed 

 a kaolinized soil zone at the top of the lower till. These exposures, how- 



1 Jour. Geol.. Vol. XVI (1908) pp. 493-98. 



2 "Geology and Mineral Resources of the St. Louis Quadrangle," V. S. Geol. Survey, 

 Bull. .J.W, p. 31. 



3 M. M. Leighton, "The Pleistocene Succession near Alton, Illinois," Jour. Geol., Vol. 

 XXIX (1921), pp. 505-14. 



4 Frank Leverett, personal communication, 1925. 



