Problems, Middle Mississippi River Region, Pleistocene Time 211 
of the Mississippi River on the Missouri side. In no place can 
it be shown that the strip is more than a mile in width and it 
may be no more than a few hundred feet in some places. 
The northern end of the exposure is along cuts made by an 
unnamed creek two miles north of the pump house of the St. 
Louis City Water Works at Chain-of-Rocks, St. Louis. (This 
locality should not be confused with the village of Chain-of- 
Rocks, Lincoln County, which is referred to elsewhere in this 
report.) Here the I[llinoian drift is of gray to brown colored, 
stiff clay, containing numerous pebbles. One boulder may be seen 
protruding from the clay about 20 feet above the stream. An- 
other larger boulder, weighing more than a ton, of red granite 
porphyry lies in the creek bed below the drift. A photograph 
taken several years ago shows this boulder came from the Ih- 
noian drift. 
From the exposure in the unnamed creek, just described, to 
a point about half a mile south of the settling basins of the 
St. Louis City Water Works, the drift is mantled by loess, but 
can be traced by numerous cuts across it. In much of this dis- 
tance the drift resembles that in the cut in the unnamed creek 
two miles to the north. In Chain-of-Rocks Park, opposite the 
City Water Works, and for a short distance northward, much of 
the drift is waterlaid. A thickness of 40 feet of sand and gravel 
has been reported. 
U. S. Highway 66 crosses the glacio-fluvial deposit in this 
vicinity and a cut at the boundary between St. Louis and ot 
Louis County. (Table V). There is some question as tO the age 
of this drift. It may be in part water-laid pre-Ilinoian, but 
the bulk of the evidence favors its being water-laid [Ilinoian. 
In a small cut about a hundred yards north of the western 
end of the Chain-of-Rocks bridge there is an exposure of gravel. 
The gravel is 20 feet or more in thickness, apparently water- 
