Problems, Middle Mississippi River Region, Pleistocene Time 213 
laid, interspersed with beds of sand and composed principally 
of chert pebbles (Fig. 15 and Table VI). 
It may be that the glacier has incorporated some Lafayette 
gravel with the drift. The Lafayette gravel occurs in a char- 
acteristic way within a few miles of this locality. It might be 
added that the Lafayette gravel is composed of almost, but not 
quite exclusively, of rounded pebbles of chert, quartz, and quartz- 
ite, together with sand. 
About a mile west of the place just described, Watkins 
Creek has undercut its bank and exposed a section of drift 17 
feet thick overlaid by 36 feet of loess (Fig. 16). A part of 
this drift is also stratified. A large number of reddish purple 
quartzite boulders are found in the stream, which leads to the 
supposition that this might be pre-IIlinoian drift (Fig. 17). The 
Kansan drift of Lincoln County, Missouri, has many such 
boulders. But it is highly probable that these boulders are from 
reworked Lafayette gravel as previously suggested. 
From one-half mile south of the settling basins of the St. 
Louis City Water Works to O'Fallon Park, for a distance of 
four miles, no drift appears. In the northern portion of this 
section, near Prospect Hill, the Missouri Portland Cement Co. has 
excavated a large pit in the Pennsylvanian shale. In the face 
of the overburden no drift may be seen. A very few pebbles 
of northern origin were picked up; but it would seem clear that 
no ice-laid deposit was made here. There is, however, meager 
circumstantial evidence that drift underlies both Calvary and 
Bellefontaine Cemeteries. 
In O’Fallon Park steep gullies expose at least 50 feet of 
till covered by about 20 feet of loess. ‘The drift is of a light 
buff to gray color, clay-like, with numerous small pebbles and 
not a few limestone erratics exceeding two feet in diameter. 
The drift has been leached and in certain layers calcareous con- 
