The structure of Mound D was clearly indicated by the vertical cross
sections (Fig. 7). An old humus-stained surface underlying the marginal
portions of the mound was sharply defined at an average elevation of
98.0 feet. No artifacts or cultural refuse were found in the floodplain
below this surface. Prior to construction of the mound a shallow,
circular pit had been excavated in the surface of the floodplain to an
average depth of 1.5 feet. The sides of the pit sloped sharply downward,
and the floor was approximately level. An embankment of yellow-brown
sand, possibly composed of back-dirt from the pit, was mounded up about
1.5 feet high and four to six feet wide around the perimeter of the pit.
This light sand zone contained a few artifacts but little or no
charcoal.
A hard-packed house floor about 0.2 feet thick lay on the bottom of the
pit. This floor zone was composed of compact sandy clay which contrasted
sharply with the overlying mound fill. Charcoal, ash, and burned clay
daub were found in quantity in the floor zone, but only a few artifacts
were recovered. Just above the house floor was a 1-foot thick layer of
dark gray-brown sand containing several charred poles and a large amount
of charcoal, ash, and burned clay daub. Above that was the sandy fill
making up the bulk of the mound. A mantle of surface humus from 0.2 to
0.8 feet thick covered the mound.
A ring of post molds was discovered around the edge of the floor, and
other molds on the west side of the house marked the position of an
extended entranceway (Fig. 10). No interior post molds were discovered.
The pothole, which extended downward through the center of the floor,
had apparently removed a centrally located hearth, only slight evidence
of burning at the edge of the pothole remaining to show that the hearth
had been there.
The entire mound fill, including the embankment around the house, was
composed of various shades and textures of sand. All of this material
was probably derived from the sandy floodplain surrounding the mound.
Small quantities of clay around the hearth and on the house floor could
have been acquired at nearby outcrops in the stream channel.
As at Mounds B and C, the circular shape of the house at Mound D was
outlined by an area of organically stained soil which extended upward
from the house floor almost to the surface of the mound. The flanks of
all three mounds were of light colored sand which contrasted sharply
with the dark, circular house outlines. The only reasonable conjecture
thus far advanced to explain this circumstance is that a low embankment
of relatively clean sand had been piled against the exterior wall of
each house. Thus when a house burned the embankment would remain
standing, well above the house floor, as a sort of mold of the lower
portion of the house. Then when a mound was erected over the burned
house remains and the standing embankment, the outline of the house
might appear in the mound fill as a cast of the house, delineated by the
circular embankment.