A PLEISTOCENE SECTION FROM DES MOINES SOUTH TO 
ALLERTON. 
BY JOHN Ii. TILTON. 
ABSTRACT. 
1. A valuable series of exposures is now to be found along the rail- 
road from Des Moines to Allerton. 
2. A detailed description of some of the outcrops. 
3. Ceneral observations 'and relations. 
The grading of a new railroad line from Des Moines to Allerton, 
passing from Polk through Warren, Marion, Lucas and into Wayne 
county, affords an excellent opportunity to secure parts of a, Pleisto- 
cene section from Des Moines south nearly across the southern half 
of the state from a series of exposures such as have never before been 
available in this region. The section is a key to the Pleistocene of south 
central Iowa, serves to connect previous work there with that yet to 
be accomplished in that region and in north central Missouri, and also 
affords data for comparison with the excellent records which Shimek 
has obtained along the Missouri river in western Iowa. 
The first important exposure south of Des Moines is immediately 
north of the small railroad station known as Coon V alley (see Des 
Moines Quadrangle, T. 78 N., R. 23 W., Ne. % of Sec. 21). The cut 
is about a quarter of a mile long. For two-thirds of that distance from 
the west the Des Moines shales may be seen, the surface rising gradu- 
ally to a height of twenty feet above the track near the center of the 
cut. What lies immediately on the shales is already concealed by talus 
in the west third of the cut; but just east of the highest point of the 
shale may be seen two bowlders of greenstone each about a foot in 
diameter embedded in a dense clay blotched with black and brown and 
resting on the disintegrated upper portion of the shale. Above these 
bowlders is three to four feet of dark brownish clay not distinctly 
separable from the clay enclosing the bowlders. Eighty feet farther 
east there rests on the Des Moines shales four feet of this dense clay, 
blue in color but brown along cracks, with pebbles of quartz and sand- 
