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IOWA ACADEMY OF SCIENCE 
Vol. XXIV, 1917 
lands of the region. The Nebraskan gumbotil is exposed only in 
those cuts the summits of which have been brought by erosion 
considerably below the elevations of the summits of the upland 
cuts. 
5. The loess is present as a mantle over the maturely dissected 
surfaces. It varies in thickness from a few feet to more than 
twenty-five feet. In general it thickens from the crests of the 
ridges down the slopes, and is apparently thicker on east slopes 
than on west slopes. The upper parts of the ridges have been 
broadened more than heightened by the deposition of the loess. 
In places the loess lies on Kansan gumbotil ; in places it is on 
Kansan drift; in other places it mantles the Nebraskan gum- 
botil ; and where there has been the most extensive erosion previ- 
ous to the deposition of the loess, it is on Nebraskan drift. 
6. The loess has two phases, the upper of which is buff in 
color, the lower, gray. In many places the buff loess is leached 
for a few feet from the surface ; in a few cuts the depth of leach- 
ing is about fifteen feet. The buff and the gray phases of the 
loess are closely related, and the evidence indicates that their 
differences are the result of chemical reactions rather than of 
different epochs of deposition. 
/ 
Department of Geology, 
The State University. 
