Cardiff Studies in Archaeology - Specialist Report Number 18

THE CHARRED PLANT REMAINS

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By S. Colledge

Charred plant remains were selected from 150 of the mound 3 samples for detailed analysis. The majority of these samples came from the lower and middle floors of the house and the upper and lower floors of the corn drying kiln. To date 104 have been investigated fully. Preservation of the plant remains was moderate to poor and the density of the charred material was low (0.4 cm3/litre). Only one sample, from the corn drying kiln, had a density significantly higher than the mean (14.4 cm3/litre). This suggests that most of the samples represent general scatters of burnt debris rather than discrete purposeful deposits.

The plant remains were dominated by the grains of crop plants, namely cereals (hulled barley, oats and rye) and flax. Cereal chaff (culms, rachis internode fragments, floret bases) and seeds of wild taxa were present in a few samples but in low numbers. Fragments of wood charcoal and charred peat/organic matter/dung, nutshell and roots/tubers were also present. Figure 12 depicts the results of a ubiquity analysis of all taxa for the 104 samples. This clearly shows the dominance of barley, oats, rye and flax in the assemblages, all of which occur in more than 50% of the samples. Seeds identified as species of either Rumex or Polygonum were also present in a majority of samples. Only five of the other wild taxa were found in more than 10% of samples, as were rachis internode fragments of barley, the most common chaff element in the assemblages.

Initial examination seemed to suggest that there was very little variation in the composition of the crop and wild taxa in the samples from the different floors. However, multivariate analysis undertaken of 84 samples and 24 taxa highlighted significant differences. For example a correspondence analysis on the 84 samples and five cereal taxa, shows that the samples from the kiln and those from the house form groupings either side of the 2nd principal axis (vertical) (Figure 13). This would indicate that the two sets of samples have distinct compositions based on the relative amounts of barley, oats and rye they contain. The kiln samples are allied more closely with oats and rye, whereas the samples from the house floors are coincidental with barley grains and rachis.

Certain contexts had exceptionally high numbers of grains of crops and wild taxa. The lower floor of the corn drying kiln had five concentrations (>100 grains of each taxa); two of barley, one of oats, one of barley and oats and one of barley, oats and rye. The upper floor had five concentrations; three of oats and two of oats and barley. These concentrations were restricted to the south east corner of both floors. This was probably the most isolated part of the structure away from the entrance and the access to the kiln flue. Concentrations in the house floors were more unusual occurrences. The lowest floor had three concentrations; one of flax, one of barley and flax and one of barley. The latter had over 1000 grains of flax. The two flax rich samples were located close to an ash dump in the centre of the house but the barley rich sample was on the west side of the house and is unrelated to any feature. Two samples from the middle floor had concentrations but they were both from the same location in the main hearth. The upper sample was rich in barley the lower sample rich in barley, flax and wild taxa.

These initial results of this analysis are encouraging and have provided a detailed picture of the range of crop species exploited by the inhabitants of mound 3. The large quantities of barley and oats is comparable to other assemblages from Norse settlements in Scotland (summarised in Campbell and Batey 1998, 210) but the discovery of both flax and rye is more unusual. Their presence at Bornais suggests a more diverse agricultural economy than normal. Spatial analysis of the data suggests there are significant differences in the distribution of different species in the different structures and are beginning to highlight spatial variations within the floor layers which help us understand the use of these structures.

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