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Each sieve fraction must be scanned separately under a low-powered stereo microscope with 10-50-fold magnification. For that, small portions of the sieving residues are put into petri dishes together with a small amount of water. To become acquainted with the different tissues in a sample it is recommended to start with the biggest sieve fraction. During the scanning process the identifiable plant or animal remains have to be picked out with soft tweezers to avoid breaking or crumbling the delicate particles. The different groups of remains must be immediately sorted into small containers with water and must not be allowed to dry out. It is useful to have a range of containers or petri dishes of different sizes ready in which to sort the extracted finds. In the case of very rich samples, two or three scanning passes of the same petri dish might be necessary.
Uncountable plant tissue fragment have to be quantified immediately during the scanning process and only some of them must be picked out for further identification, pictures etc. Quantification Waterlogged.
Quantification of waterlogged remains
Quantification of waterlogged remains
Every distinguishable part of a species should be quantified separately (apple seeds, apple pericarps, apple fruit epidermis etc.). The best kind of quantification is of course counting the remains, and in the case of fragmented remains, initially counting units have to be defined. Plant tissue fragments, like cereal bran or epidermis fragments, are often uncountable. Here semi-quantitative methods like estimating or scoring are used.
While unique plant remains such as seeds, fruits or cereal chaff are usually counted after their identification, tiny fragments of plant tissues which often occur in larger quantities (fragments of leaves, epiderms, mosses etc.) must be quantified by estimation during the scanning process.
Scoring of abundances provides only rough results and is rather subjective, but allows a quick analysis of a sample. From some rest types countable complete pieces, halves or quarters will be found in the bigger sieve fractions, while the tiny fragments from the smaller fractions are not countable and have to be estimated. There are different ways to come to estimation values, but usually a scale similar to the following will be used: p = present, + = few, ++ many, +++ masses.
Basis for the next step, the data analysis should be a raw data list, containing name of species name, remain type, state (uncharred) and the quantity of remains per sample.
When samples are very rich in plant remains, it may not be possible to scan the entire material of the smallest fractions and subsamples must be taken. This could be done for example by grid-sampling in a flat, square bowl with drawn quadrants. The material of the fraction is put as homogenious as possible in the bowl and the subsamples are taken from some of the quadrants. An ideal quantity of a subsample can not be given in principle, but depends on the particular sample itself and must be decided new in every case (Jacomet et al. 2007, 28f.).
In the case of large sample series "Rapid Scanning" is used to get a first impression of the samples and to select those which should afterwards be analysed in detail. For that the fractions are scanned roughly and the plant remains are noticed half-quantitatively. From the smaller fractions only 2-3 teaspoons of material are scanned (Jacomet et al. 2007, 30).
Waterlogged samples may contain plant remains of various types and preservation states. They may be charred or uncharred or mineralised or partly carbonized. Remains of cultivated plants and field weeds as well as twigs and wood pieces (charcoal) often occur in both states, while fruits and seeds of wild plants, leaves, mosses, epidermis fragments, buds, bark and apple pericarps are nearly always uncharred. It is necessary to sort and record the different types of remains separately.
Animal remains as well as plant remains, may be found in waterlogged samples. They may derive from insects, from the aquatic or litoral fauna of the lake, river or moorland (molluscs, fish) or from human meals (mammals, birds, fish). For further examination, these remains could be also sorted roughly by the archaeobotanist or the sieving residues should be transfered to a specialist.
Scanning and sorting
Scanning and sorting
Scanning and sorting with a low-powered stereo microscope. Photo: IAR project.
Different utensils for scanning and sorting. Above from left: basin for the sieving residue; glass tubes with caps for storing the finds in preservation liquid; bottles for water and preservation liquid; below from left: big petri dish for scanning a sample of the sieving residue; small petri dish into which the selected items are sorted; various tweezers, a pen and various boxes for finds. Photo: IAR project.
Various types of remains in waterlogged samples
Various types of remains in waterlogged samples
Peaces of charcoal, bark and wood fragments, small stones, fish bones and fish scales, roots, raspberry seeds. Photo: Ch. Herbig.
Twigs of ash, tiny wood and charcoal fragments. Photo: Ch. Herbig.
Masses of fish and mammal bones, snail shells, fruitstones from plums and common dogwood, blackberry seeds etc. Photo: W. Tegel.
References
References
- Jacomet, S.
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