VSF 2010 Report - Nabo

homefield, but cannot further our understand of the building.
Sample 35 (Figures 5.3 and 5.4)
This sample was taken from an area closer to the centre of the structure, and contained a
thicker occupation layer since the floor deposit was thicker in the centre of the room than
it was at the sides.
Like the other samples, this thin section included the underlying podzol. However,
notably this particular sample included three horizons from this soil layer, including the
the A horizon, the light coloured (elluviated) E horizon, and below this the reddish B
horizon, where the iron leached from the horizon above had accumulated. These natural
soil horizons contained a small number of bone and charcoal inclusions that had entered
the layers due to bioturbation, which was also indicated by the presence of earthworm
channels.
The dark occupation deposit captured in this sample had evidence of trampling in
the form of horizontal planar voids that had been created by vertical compression. Like the
other samples from Structure 3, this floor layer contained a high percentage of charcoal,
both small fragments and larger pieces. All of the identifiable charred wood appeared to be
Betula (birch) (Figure 5.18), the most common wood species and fuel source in the region
(see Mooney, this report). The other identifiable charred organic material in this layer was
seaweed, indicating that dried seaweed was burnt, either as a fuel, or to generate a smokey,
oxygen-poor environment, or to generate the salts that could act as a flux in the iron
smelting processes (see Birch, this report). Also present in this floor layer was a significant
amount of amorphous organic matter, indicating that there had been plants and on the floor
that had since decomposed. Fungal sclerotia is present in this layer due to the high organic
content. The other anthropogenic inclusions located in this layer were a number of burned
and unburned bone fragments (Figure 5.19).
The turf collapse layer, as in the other samples from Structure 3, was very
heterogeneous with a number of irregular lenses in it. The lowermost part of this layer
contained a distinct organic lens, packed with grass phytoliths, which is the former H
horizon (the layer consisting of plant matter) of a piece of turf, which had been turned
upside down (Figure 5.20) In the upper part of this turf layer was a clear black lens that
was not present in any of the other samples (Layer 5 in Figure 5.4). This is best interpreted
as the sooty remains of the underside of the roof turf, which had been blackened by the
fire, supporting the view of reversed stratigraphy in the turf roof collapse. This turf layer
has a lenticular structure, with silt cappings on top of the soil aggregates, which was
created by post-depositional episodes of free-thaw (Figure 5.21). Freeze-thaw evidence is
only present in the roof collapse layers of Structure 3, and not in any of the floor deposits
or underlying soil. It is therefore likely that this freezing occurred after the abandonment
of the building, when the upper, roof collapse layers were prone to wetting and freezing
processes.
Sample 38 (Figures 5.5 and 5.6)
The underlying soil layer in this sample contained a high concentration of organic
material, which was located at the top of the layer and had a dominant horizontal
orientation (Figure 5.22). This thin organic layer, rich in grass phytoliths, is the remains of
grass from the H horizon of the underlying podzol, and as such is definite evidence that the
farmers chose not to deturf the area prior to constructing the building. The grass had died
in situ and had been trampled/crushed into a horizontal orientation. The grass would have
died shortly after the construction of the building roof (due to lack of sun and water) and
would then have been trampled early in the building's use, and finally buried under the
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