25th International Meeting on Organic Geochemistry IMOG 2011

P-136
Analysis of insoluble organic residues in graves by sequential
thermal desorption/pyrolysis-gas chromatography-mass
spectrometry
Matthew Pickering, Kimberley Green, Don Brothwell, Brendan Keely
University of York, York, United Kingdom (corresponding author:brendan.keely@york.ac.uk)
The archaeological investigation of human burials
provides valuable insights into past populations. The
approaches employed focus mainly on the recording,
examination and interpretation of the visible human
remains, grave goods, burial structures and soil
features. While grave soil in direct contact with the
body is sometimes examined for physical traces such
as seeds, pollen and parasite eggs, it has rarely been
examined in detail and is often discarded.
The InterArChive project has adopted a combination
of approaches: organic geochemistry and soil
micromorphology; to characterise organic matter in
grave soils in order to reveal signatures of body
decay, mortuary practices, clothing, diet and morbidity
and to evaluate soil compositions and types that lead
to enhanced preservation of the organic signatures.
The work presented here focuses on one aspect of
the organic analysis: the use of sequential thermal
desorption-gas chromatography (TD-GC-MS) and
pyrolysis-gas chromatography-mass spectrometry
(Py-GC-MS) to characterise the constituents of
solvent insoluble organic residues associated with
human burials.
Burials spanning a wide range of ages, geographical
locations and soil types have been sampled at
specific locations around the skeletal remains and
from any associated artefacts (e.g. burial pots, coffin
stains). In addition, visible fragments of hair, coffin
wood, textiles, leather and paper have been collected.
Control samples of the grave fill and from outside the
grave enable the organic geochemical background to
be established. Duplicate samples of undisturbed soil
have been collected from key positions around the
skeletal remains for micromorphological analysis.
Elemental analysis (C/H/N/S/O and total organic
carbon content) provided a broad indication of the
nature and quality of the organic matter present and
has been used to identify soils containing sufficient
organic matter concentrations for pyrolysis. Analyses
of the solvent insoluble organic residues by TD- and
Py-GC-MS have been compared with those from
modern reference materials, revealing information
regarding the identity, composition and preservation
state of these materials from their chemical
signatures. The pyrograms from partially preserved
coffin woods recovered from sites in Scotland and
Belgium (e.g. Fig. 1) show marked similarities in the
profiles of lignin-derived guaiacyl subunits, these
more closely matching the signatures of modern pine
than of oak, and exhibit preferential breakdown of the
cellulose component of the wood. The project aims to
evaluate the potential for the detection of such
remains in grave soils in which visible remains are
absent.
A fundamental goal of the InterArChive project is to
provide sampling recommendations that can be used
to inform future archaeological excavations of human
burials in order to maximise the amount of information
retrieved. In addition, the methodologies and data are
relevant in the context of the forensic examination of
more recent burials.
Fig. 1. Partial Py-GC pyrogram (610°C) of a sample of
coffin wood collected from a grave in Belgium.
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