380 
SOUTHERNMOST KANSAS TILES 
diameter. The larger boulders, which are more numerous at ex¬ 
posure 2, measure over one foot in diameter and consist for the 
most part of red Sioux quarzite. 
In all cases the till is exposed on gentle slopes leading down to 
young valleys. A loess-like silt covers the till-like materials in 
most places, and in some instances small pebbles of quartzite, chert 
and quartz are included in the overlying cover. The immediate 
country is relatively flat with few shallow valleys cut in it. Be¬ 
cause of this topography exposures are very few and in most 
cases nothing but the silt-like material appears at the surface. 
To account for the presence of these deposits several interpre¬ 
tations are presented: 
1. The material is in situ, having been deposited by the Kansan 
ice-sheet which advanced farther south than is indicated by the 
position of the mapped glacial border according to Todd. 
2. The material is in situ, having been deposited by a tongue 
of the main ice-mass rather than by the ice-sheet itself. 
3. The material is not in situ, having been brought to its present 
position by debris-laden ice-bergs floating on a lake or in the 
current of a stream or having been deposited as outwash. 
4. The till-like deposits are associated with Nebraskan gla¬ 
ciation. 
According to the hypothesis that the county south of the Kansas 
River is glaciated, the Kansan ice-sheet crossed the valley of 
Kansas River and advanced southward at least as far as the 
two southermost outcrops. The deposits, therefore, represent till 
in situ. Whether the entire ice-mass crossed the valley, is difficult 
to determine with the knowledge at hand. Insufficient exposures 
and lack of thorough investigation up to the present time make it 
impossible to come to definite conclusions. To the writer it is 
^ not at all unlikely that the region south of the Kaw valley has 
been actually glaciated. The topography is flat, the slopes are 
gentle, hence exposures are few. What lies below the general 
silt-like covering has never been determined. Like the Iowan 
ice-sheet, the edge of the Kansan ice-sheet was undoubtedly thin 
and more or less sluggish, as the thickness of the till where known 
north of Kansas River is relatively thin and patchy having been 
made more attenuated by post-Kansan erosion.’’ According to 
7 L,oc. cit., p. 35. 
