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HISTORY OF WOOD COUNTY
Marking the southern border of the second drift is a prominent range of hills
known as the Marshfield Moraine. The topography over the glaciated region
varies from level to rolling, and in a few places, hilly, The surface is
largely char-
acterized by long gentle slopes. The soil is comparatively free from stones
and
consists mainly of silt loam or clay loam. One of the most important character-
istics of this old drift is the heavy compact nature and the pronounced mottling
of the subsoil. This material has weathered to a much greater degree than
the
late Wisconsin drift, the topography is much more mature and there are no
lakes
and few peat marshes. With the exception of the Marshfield Moraine and a
few
other limited areas, the effects of glaciation in this region have been largely
ob-
literated through erosion and weathering.
   Along the eastern border of the county, in parts of Milladore, Sherry,
Sigel
and Rudolph Townships, the soils are considered to be largely of residual
origin.
The material forming the surface soil, and, more especially, the subsoil
has been
derived from the weathering of the underlying crystalline rocks. Angular
rock
fragments are scattered frequently over the surface and a few glacial boulders
occur. It seems probable that parts of the region were traversed by an ice
sheet,
but in most instances this does not seem to have had any appreciable influence
on the formation of the soil. The surface is in the main gently rolling,
with long
slopes and broad, rounded elevations. In the southern half of the county
also
there are a few areas in which the soil is residual, but here it has been
derived from
Potsdam sandstone instead of crystalline rocks.
   The region of alluvial soils is confined to the southern third of the
county,
mainly to the south of Wisconsin Rapids and the Green Bay and Western Rail-
road. The country consists of a series of sand flats, associated with which,
west
of the Wisconsin River, there are extensive marshes. Some of these marshes
con-
tain numerous small sand islands only one or two feet higher than the level
of the
marshland. The greater part of the material throughout this sandy region
is of
alluvial origin, having been deposited by enlarged streams during preglacial
or
interglacial times. In a few places the underlying Potsdam sandstone comes
to
the surface and gives rise to a residual sandy soil. When a shaly phase appears
with the sandstone the residual material is considerably heavier.
   Over most of the county, except the southern sandy region, the surface
shows a
covering of extremely silty material which has the characteristics of loess,
and it
seems probable that much of the surface material making up the silt loam
was
deposited by wind action.
   Throughout most of the northern balf of the county and over isolated areas
in the southern, crystalline rocks, mainly granite, make up the surface formation.
In the vicinity of Milladore, Pittsville, and Wisconsin Rapids, and in a
few other
places, gneiss and schist appear as the surface rock. In the vicinity of
Arpin and
Powers Bluff conglomerate and quartzite occur. In Milladore and Sherry town-
ships and at. a few other points diorite-gabbro constitutes the surface rock.
The
depth to bedrock usually varies from four or five to over fifty feet. Outcrops
of
these various formations occur frequently. Over most of the southern part
of the
county and along the western border sandstone appears as the surface rock.
In a
few places the sandstone outcrops, though in most cases, especially near
the Wis-
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