Condition of the archaeological deposits

Plant preservation

Remains of plants (Table 15) preserved by anoxic waterlogging were rather sparse in the samples examined during this exercise, although the humic content of the deposits presumably mostly originated through the decay of plant matter. Charred remains were restricted to charcoal (occasionally present in moderate to large amounts), and occasional charred propagules, almost always seeds of weeds, typically cornfield taxa. Mineral-replaced material was sparse except for the samples with concretions, but even here there were few discrete fossils. A small number of layers showed at least local mineral deposition throughout the matrix, revealed by a 'biscuity' texture.

The anoxic, waterlogged plant material was generally poorly preserved; wood fragments were usually soft and amorphous, often pale in colour. Wood observed in the raw sediments was frequently extremely soft and crumbly, with a reddish or orange colouration; it is likely that this did not survive laboratory processing in large enough fragments to be recorded from residues. There was no correlation between wood preservation and stratigraphic depth or between preservation and pH . Other anoxically-preserved remains were generally somewhat eroded (except perhaps for fig, Ficus carica L., seeds, whose hard, shiny testa is in any case very resistant to decay). The colour of these remains was often paler than they would have been 'in life'. They were comparable in overall quality of preservation with those from the worst third of the range seen in deposits at 16-22 Coppergate. There was a weak negative correlation between preservation and depth - perhaps because pit fills (with inherently better preservation and/or higher organic input) tended to be in the upper parts of the sequences, although the plot of fruit/seed preservation and organic content gives no support to the argument that at this site higher organic content is correlated with quality of preservation (rather, the opposite). Moreover, there was, as shown above, no significant difference in mean organic content between 'pit fills' and 'dumps'. There was a slight correlation between the degree of decay of fruits and seeds and pH, which matches preconceptions about the causes and effects of alkalinity in deposits of these kinds.

The charred remains were generally quite well preserved, although in some samples charcoal was very crumbly; there appeared to be no pattern to this with depth and observations of modern charcoal show that fresh material may range from almost crystalline to soft and powdery in texture.

The mineral-replaced plant material, whether in concretions or as discrete fossils, was usually very poorly preserved, the fabric being crumbly rather than having the glassy texture sometimes observed at other sites. This is probably not a function of post-depositional decay, but rather of the ground conditions during and immediately following deposition, since recent work has shown that mineral-replacement occurs rapidly following deposition (Allison and Briggs 1991; Briggs and Kear 1993a; 1993b). Some of the mineralised sediments appeared to be oxidising, being very delicate and in some cases extremely strongly orange in colour.


© Author(s). Content published prior to 2013 is not covered by CC-BY licence and requests for reproduction should usually go to the copyright holder (in most cases, the author(s)). For citation / fair-dealing purposes, please attribute the author(s), the title of the work, the Internet Archaeology journal and the relevant URL/DOI.

University of York legal statements

Last updated: Wed Mar 6 2002