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Title: Development and application of archaeological biomarkers in organic residue analysis
Other Titles: Ontwikkeling en toepassing van archeologische biomerkers in organische residueanalyse
Authors: Baeten, Jan
Issue Date: 23-May-2012
Abstract: Archaeology attempts to reconstruct past human societies in both their generality and specificity. Inferences about social organisation, cultural behaviour, the relationship between man and environment, etc. are made from the material evidence recovered by archaeological excavations – either products of human activity (e.g. buildings, ceramics) or environmental evidence (e.g. pollen). Among this material evidence, organic remains testify the exploitation of biological resources by man for nutritional, technological or socio-cultural purposes. These organic remains, particularly when amorphous, can be examined by organic residue analysis, a biomolecular approach comprising a range of advanced chemical analytical techniques such as infrared spectroscopy, chromatography and mass spectrometry. These techniques facilitate the isolation and identification of hundreds of individual molecules from organic residues. In order to interpret these molecular signatures objectively, biomarkers or molecule-species relationships are required to link a certain molecule – or even a certain pattern of molecules – to its biological origin. An additional prerequisite for interpreting chemical signatures is a comprehensive understanding of the processes that alter the composition of biological products during their utilisation and after burial. This doctoral thesis covers a range of diverse organic residue types including lipid residues associated with ceramics and lipids preserved in coprolites and sediments. Furthermore, the case studies presented herein cover a broad range of issues including pharmaceutical practices in history, the art of ancient perfumes, human diet, waste disposal and manuring.First of all, an in situ preserved 16th century ointment from the castle of Middelburg (Belgium) was characterised both qualitatively and quantitatively by a multi-analytical approach involving chromatography, mass spectrometry, X-ray techniques, elemental analysis and infrared analysis. The organic fraction, constituting about 24 wt. %, consisted of beeswax next to smaller amounts of a triglyceride lipid source. The inorganic ingredients represent about 30 % of the total mass and contained minerals such as calcium sulphate (gypsum) and lead sulphate. Furthermore, infrared analyses indicated the presence of calcium carboxylate soaps indicating a post-burial exchange of cations between the lead carboxylates and gypsum. Comparison with Late Medieval manuscripts revealed that the ointment constituted in fact a medicinal lead plaster used for treating bruises, ulcers and sores. Beeswax was added to the plaster for easy application on the skin. Gypsum could have been added to whiten or to strengthen the plaster.Surface residues from a Late Helladic grave flask from the site of Hala Sultan Tekke (Cyprus) constitute another type of residue. Specifically, it was attempted to verify if these residues contain traces of the original contents of the flask – presumably a scented ointment or perfume. Lipid analyses revealed clear biomarkers for a ruminant fat andfor vegetal sources. Whereas the animal fat could have served as a base for an ointment or perfume, the presence of plant lipids may indicate the addition of odoriferous herbs. However, the authenticity of these plant lipids cannot be ascertained because they do also occur commonly in soil organic matter. Particularly the detection of a number of soil minerals in the inorganic fraction of the residue supports this hypothesis. The presence of the animal fat is less doubtful since its biomarkers have been detected in high amounts and do not commonly occur in soil organic matter.In order to retrieve direct evidence of dietary habits in Anglo-Saxon Hamwic (Southampton, UK), absorbed lipid residues from coarseware from this site were analysed by gas chromatography mass spectrometry (GC-MS). This technique has proven particularly useful in resolving complex lipid signatures which show a mixture of various inputs. The results show that the vessels were used for preparing stews of ruminant fats and vegetables (mainly cabbage), and marine foods. Beeswax was also present in one case and most likely relates to a sealing function or to honey. A mixture of animal and plant derived ketones was identified by examining the carbonyl distribution in mid-chain ketones. The study also revealed potential novel biomarkers. The isomeric mixture of 8- to 16-hydroxyoctadecanoic acid was found to be highly diagnostic for ruminant fats. Furthermore, the co-occurrence of heptadecenoic, nonadecenoic and isoprenoid fatty acids was proposed as a biomarker for aquatic food sources. This finding presents a particular advantage to the field as the tracing of fish and sea foods in archaeological residues has been particularly troublesome in the past, especially when these foods are not extensively heated in ceramics (e.g. garum).Finally, it was also aimed to reconstruct the history of the public latrine from the ‘Imperial Baths’ of Sagalassos (Turkey). Therefore, sediments from several occupation levels within the room were investigated by a multidisciplinary approach involving radiocarbon dating, geomorphological analysis, elemental calcium analysis, faecal biomarker analysis and botanical analyses. 5ß-stanols of human origin were found in the sewage channels together with mineralised plant remains, indicating a human faecal context. The botanical remains are furthermore representative of the Roman diet in Sagalassos. Soil layers, deposited on top of the latrine floor and dating to the Early Byzantine period, contained herbivore derived 5ß-stanols. Additionally, the epimerisation of these stanols to its 3α-epimers is a prime indicator for the compositing of the animal dung. In this period, the former latrine was clearly used as a manure production site. This is further confirmed by stratigraphic evidence of large amounts of urban waste artefacts and lime layers. The results of the present study also support the theory that off-site potsherd scattering can be used as a proxy for manuring events. Additionally, the data show key evidence for vertical migration of5ß-stanols and presumably also for the leaching of bile acids.
ISBN: 978-90-8826-240-1
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Archaeology @ Leuven
Centre for Surface Chemistry and Catalysis
Sagalassos Archaeological Research Project

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