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New Philadelphia : 2004 Archaeology Report |
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Two flotation samples were taken from Feature 1 level a1 and one sample was taken from level a2 of the feature. Feature 1 is a cellar feature on Block 9, Lot 5 that was filled in the early twentieth century after the structure above it was dismantled. The sediment for the samples was taken matrix that was screened through quarter-inch mesh hardware cloth. (The >0.25" material on the screen was not added to the samples.) Each bag held approximately 10 liters of screened sediment.
When the barrel is filled with water and the insert screen is in place, a
bag of fine-mesh nylon or polyester fabric (the equivalent of drapery sheer
material) is attached to the lip of the sluiceway. With the shower head
activated, the measured soil sample is slowly poured into the barrel insert.
Immediately charcoal and other light-weight items such as snail shells,
small bones, fish scales, eggshell, and small uncarbonized botanicals flow
over the sluice and are caught in the bag. The sediment that settles on the
screen in the insert is agitated by hand in order to free up other trapped
light-weight material and to facilitate the break up of sediment clumps.
Care is taken not to force materials down through the bottom of the screen.
The shower is allowed to run until no more material is being brought to the
surface and no sediment clumps remain on the screen. With most soils, the
process takes approximately 40 minutes, unless the human agitators are
particularly energetic in their sediment swishing, in which case 20-30
minutes will suffice.
The “light fraction” is the portion of sample collected in the fine-mesh
bag, and the water flotation “heavy fraction” is that which remains on the
screen when the barrel has been drained from the bottom. Both fractions are
rinsed in clean water. The heavy fraction is then refloated in a fine-mesh
(0.425 mm) sieve in a container (graniteware canner) filled with zinc
chloride solution of specific gravity of 1.6, as monitored with a
hydrometer. This processing in denser solution (water having a specific
gravity of only 1.0) results in the recovery of the denser botanical
material, such as black walnut shell fragments, as well as additional bone
and other small items. That items that floats to the surface in the zinc
chloride processing are scooped off with a 0.425 mm-mesh strainer, rinsed in
clean water, and added to the water flotation light fraction. The remaining
heavy fraction is rinsed in clear water several times, dried, and bagged
separate from the light fraction.
In the archaeobotany laboratory of the Illinois State Museum, the students
used a geologic soil sampler to randomly “split” each light fraction into
three parts. Hence the three bags originally taken as soil samples were
portioned out for analysis in nine parts. Working in groups of 2 or 3 at a
time, the students were given basic instructions in archaeobotanical
analyses and then undertook the sorting process on their own, with
supervision from the ISM archaeobotanist.
To begin, the students sieved their light fraction portion through nested
2-mm and 0.5-mm sieves, retaining the <0.5-mm residual. The non-charcoal in
the 2-mm screen was removed as “contaminant” but preserved in the bag with
the <0.5-mm residual, which is kept with the sample through the entire
process. The cleaned charcoal in the 2-mm sieve was then weighed to the
nearest 0.0001g, rounding to 0.001g. Under a dissecting microscope of from
0.8 X to 40 X zoom magnification, charcoal was sorted into type categories
(nut, wood, seed, corn cob). A 20-piece subsample of the wood and all other
items > 2 mm were then sorted into the most refined taxon possible, with
examples of different nut and wood types being shown to each student by the
ISM archaeobotanist. Counts of the number of specimens in each taxon were
made for all the charcoal (i.e., charred plant material) in the 2-mm screen.
For the material in the 0.5-mm screen, a subsample was taken using the
geologic soil sampler, and this small portion “decontaminated” by hand,
using tweezers and an artist’s paintbrush under the microscope. The
contaminants, the cleaned subsample, and the remainder were all weighed, and
an estimate of the weight of the charcoal in the uncleaned sample as a whole
made proportional to these fraction weights.
The one 10-liter sample from the lower level of Feature 1 (level a2) has an
estimated 14.2 grams of charcoal (14.2 g/10 l). Only 8.5g of the total (60%)
is within the 2-mm screen, indicating a higher percentage of breakage than
is evident in the upper level. Indeed, there may have been filtering of
smaller charcoal particles downward, resulting in the higher concentration
of 0.5-2mm sized charcoal in the lower level. By count, the 802 specimens of
charcoal in the 2-mm screen are 93.2% wood and bark, 3.1% nutshell, 2.9%
unknown, 0.6% corn, and 0.1% large seeds (actually one seed, wheat--Triticum
aestivum). Of the nutshell, 60% is hazelnut and 40% black walnut. Of the
wood charcoal, 51.04% is of the white oak group, 30.63% of the red oak
group, 6.7% black walnut/butternut, 5% maple/box elder, 3.3% wild cherry,
and 1.7% each of ash (Fraxinus sp.) and persimmon (Diospyros virginiana).
Among the charcoal 0.5 to 2 mm in size, there are two carbonized seeds of
blackberry or raspberry. With the wheat seed, total carbonized seed
concentration for this level of the feature is 3.0 seeds per 10 liters of
sample sediment.
Both levels contained numerous uncarbonized seeds that have to be considered
more recent “contaminants” to the carbonized material, as there is no way of
determining their actual age. It is expected that in an open-air site in
central Illinois, in non-”sealed” context, uncarbonized material would have
completely decayed within the time span under consideration (ca. 1936, when
the dilapidated building was removed, to present times). Types of seeds
found in uncarbonized state include blackberry/raspberry, jimson weed, black
nightshade, tobacco, elderberry, purslane, grasses, wild legume, and one
blueberry. Most of these can be found in fallow fields and agricultural
field margins today and can be found within soils that are bioturbated or
otherwise disturbed. Such tiny seeds as these could also have filtered down
during soil desiccation, or freeze/thaw cycles. The blueberry is the only
one of the uncarbonized that is not considered adventive or an escape, but
it may have been brought in by a bird or other visitor to the site.
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