bronze age environment and economy in the troad - Universität ...

chapter 2: methods
The set of data of the identified and counted botanical remains
raises the question of how far the data represent the original
situation. In other words, what are the processes affecting the
assemblage between the beginnings of the deposition of plant
remains and recovery and analysis by the archaeobotanist The
solution of these questions is difficult, and even more so the
consideration and integration of the results into the
interpretation of the data. Some of the taphonomic effects on
plant remains are known, e.g. that of combustion (more
damage occurs with increasing temperature). All later
processes during deposition, or sampling and extraction of the
carbonised remains, result mainly in fragmentation.
For the taphonomic effects on macroremains during
carbonisation, Boardman and Jones (1990) obtained
quantitative data from charring experiments. They tested
destruction of different parts of the cereal plants caused by
carbonisation. Their results suggest limits to the interpretation
of cereal remains. One of their main discoveries was that those
components which are characteristic of early crop-processing
stages and which are rarely represented in archaeological
contexts (i.e. straw, free-threshing cereal rachis) are the first to
be lost through charring. Crop-processing might not to be
recognised on this basis. During combustion, some of the
species/taxa seemed to be more resistant to destruction than
others. The grain generally survives better than the chaff.
Einkorn chaff generally survives best. As already mentioned,
glume wheat chaff survived better than rachises of naked wheat
or barley, of which the latter was less resistant.
Where little chaff from free-threshing cereals (rachis segments)
is found at archaeological sites, this could be a result of loss of
material by its pre-depositional combustion and might not
necessarily reflect the original function or even economic
behaviour.
According to Hillman (1983), electron spin resonance (ESR)
determinations of the charring temperature should be standard
archaeobotanical procedure. This would show the likelihood of
chaff and straw loss. The interpretation of ESR results remains
difficult, however, because of the somewhat unclear influence
of depositional and post-depositional processes.
With the material from Troy and Kumtepe, it has not been
possible to investigate pre-depositional taphonomy by
techniques such as ESR analysis. Therefore taphonomic
consideration has had to concentrate on depositional and postdepositional
processes. The following section discusses some
questions of taphonomy relating to these processes. For this,
sedimentological aspects were considered within the
excavation. The need for a sedimentological analysis was
suggested when a relationship between the amount of
macroremains in the sediment and the sediment characteristics
was observed during the flotation process.
At the beginning of the flotation in 1993, it was observed
thathe state of preservation of the remains seems to be related
to the type of sediment in which they are found. The first
thought was that by understanding this relationship, one would
learn more about the depositional conditions of the sediment,
and therefore of the remains, aiding interpretation not at least
in terms of representativeness (Willerding 1971). In the first
stage of this work a comprehensive analysis of the sediments
was planned, but this aim was given up, because the laboratory
efforts required were disproportionate to the value of the
results.
Amongst the most promising qualities of the sediment that
might be related to the taphonomy of carbonised remains are
those that indicate any kind of mechanical process, for
example, whether the quantity of carbonised remains is low
when the sediment is chalky and rich in sharp-edged stones.
Loss by ignition, which provides information on the organic
proportion within the sediment (e.g. microfauna, roots) was
also thought to be suitable evidence for ‛mechanical stress’.
Organic matter could represent the remains of aggressive
agents such as roots or microfauna, actively disturbing the
sediment particles and therefore mechanically destructive of
carbonised plant remains. The organic content in the sediment
can be measured through the loss by ignition, the loss of weight
after heating to 400°C representing the organic portion.
The proportion of chalk (CaCO 3 ) was measured because of its
potential to harden the sediment and to damage the fragile
carbonised remains. The content of chalk was measured with a
second combustion at a higher temperature. The loss of weight,
i.e. the former content of CaCO 3 can be calculated from the
molecular weight of the escaping carbon dioxide. In general the
chalk proportion at Troy was slightly higher than that of the
Kumtepe samples. From the few samples analysed from Troy,
those from the Lower City came up with the highest proportion
of chalk (trenches I 17, p28 and w 28), due to their proximity
to outcrops of bedrock. Samples from those trenches were at
the same time quite poor in remains, so that one could assume
a relationship exists. More samples have to be analysed,
however, to prove that this pattern is not coincidental.
Further, the results from the sediment analysis were planned to
be related to fragmentation and distortion of the carbonised
material. Preservation of the grains in these samples was
therefore recorded.
Different methods exist for recording the state of preservation
of subfossil seeds and fruits, e.g. Murphy and Wiltshire (1994)
for waterlogged material and Hubbard and al Azm (1990) for
carbonised cereal grains. A scheme similar to that of Hubbard
and Al Azm was used to evaluate the remains from Troy and
Kumtepe. This assessment scheme contains three states of
fragmentation and three states of distortion that are estimated
with scores from one to three for the carbonised cereal grains.
The three states of fragmentation are mainly matter of postdepositional
preservation. These are (1) ‛not fragmented’, (2)
‛single split offs, but with more than 50% of the grain
preserved’, and (3) ‛heavily fragmented, difficult to identify’.
Pre-depositional fragmentation, e.g. during crop-processing, is
recognisable by swelling at the surface of the break during
charring. Such grains were not considered. For corrosion or
distortion, which mainly represents the effects of combustion,
there was the choice between an (1) ‛intact surface’, (2) ‛single
split offs of the surface’ and (3) ‛surface hardly preserved, up
to skeletal structure of the grain’.
The 30 samples which were evaluated for loss of ignition,
chalk content, fragmentation and corrosion of the cereal were
from different periods, and came from the Upper and the
Lower City of Troy and Kumtepe.
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