14 
SOIL SURVEY OF BUFFALO COUNTY. 
occurring in the position of terraces; and (3) the overflow plains 
of the present streams. 
The soils in the last two divisions have been derived to a very 
large extent, if not wholly, from the soils of the first division 
and represent wash material transported by the streams and 
deposited in their flood plains. The material of the first bot¬ 
toms is of recent deposition and the process is still going on; 
but those in the terraces are much older, some probably dating 
back to glacial time or before, with the result that through 
weathering the surface has come to be more like that of the 
uplands than that of the first bottoms. 
The upland soils are predominantly silty, as is the case 
throughout the unglaciated area of the State. The great extent 
of silty soils has led some to believe that a blanket of wind blown 
material originally overspread most of the region and that the 
soils are derived for the most part from this deposit and are 
residual from the underlying formations which in an undecom¬ 
posed state are now usually found at a depth of less than 15 feet 
from the surface and outcrop in many places. The silty material 
is of a rather smooth texture and comparatively free of stone 
or other coarse material, but it is just such material as would 
be expected to result from the mature weathering of the country 
rock, consisting of fine and cherty limestones, shales, and sand¬ 
stones. 
Over a large part of the county the uppermost rock consists 
of the lower Magnesian limestone. Once the limestone was con¬ 
tinuous as the surface formation, but as the result of erosion 
which has deeply dissected and worn away much of the old plain, 
it is now found only as remnants capping the higher hills and 
ridges and giving way in all the lower levels to the Potsdam sand¬ 
stone, the immediately underlying formation. The limestone 
and a massive phase of the Potsdam sandstone outcrop along the 
upper slopes and give rise to steep stony slopes and cliffs. At 
lower levels the principal rock is a thin-bedded sandy shale or 
shaly sandstone with occasional layers of a heavier shale, 
underlain by limestone, characterized in general by a brownish- 
gray to brown silty soil underlain by a yellowish brown or buff- 
colored silty clay loam subsoil, are classed in the Knox series. 
The soils of the slopes below the limestone lying mainly on the 
sandstone and shale layers and which have been made up in part 
or wholly of materials derived from the sandstone, have been in- 
