GROUP OF LIGHT SANDS AND FINE SANDS 47 
PLAINFIELD SAND. 
The surface soil of the Plainfield sand to an average depth of 
about 12 to 14 inches consists of a fairly loose, brown to dark- 
brown loamy sand of medium texture. There is a considerable 
amount of fine sand mixed with the medium sand in places, and 
in such places the soil might be classed as a fine sand if of suf¬ 
ficient extent. Litmus-paper tests indicate that the soil is acid. 
The subsoil consists of a lighter brown medium sand which gradu¬ 
ally becomes a yellow sand at from 28 to 36 inches. The deep 
subsoil consists of stratified sand in which varying amounts of 
gravel may be found. As a rule the soil next to the bluffs is 
darker and slightly heavier than that close to the river. 
The largest area of this type mapped in the present survey oc¬ 
curs as a narrow terrace along the Chippewa River Valley in 
the northwestern part of the county. This terrace ranges in 
width from one-eighth to one-half mile, and has a length of over 
10 miles and an elevation above the flood plain of the river of 20 
to 50 feet or more. The rise from the flood plain is quite abrupt 
in most places. At the mouth of Big Waumandee Creek there is 
a terrace of the same soil about 4 miles long and in its widest 
place about three-fourths of a mile across. None of this type is 
found outside of the Mississippi and Chippewa Valleys. 
The terrace occupied by this soil has the same position as that 
occupied by the La Crosse fine sandy loam, and the surface is 
usually level or gently sloping toward the streams. In places 
there is an undulating or billowy topography, where the wind 
apparently has altered the original surface features to a slight 
extent. On account of the loose, open structure of the material 
the type is excessively drained and subject to drought. 
Being of a terrace formation, the type is alluvial in origin, the 
material having been deposited by the Mississippi River during 
the glacial period, when the volume of water carried by that 
stream was much greater than at the present time. A small 
quantity of gravel is mixed with the sand in the low ei sections, 
and this gravel is doubtless of glacial origin, as is also a part of 
the sandy material. 
The greater proportion of this type was originally in the con¬ 
dition of a prairie, with only a few scattered sciubby oaks. 
Prairie grass was the most common growth, though this was not 
heavy. 
