A COMPARISON OF METHODS FOR ESTABLISHING FATTY ACID CONCENTRATION GRADIENTS ACROSS POTSHERDS: A CASE STUDY USING LATE BRONZE AGE CANAANITE AMPHORAE*

Canaanite amphorae fragments in fabrics believed to be associated with the bulk transport of vegetable oils from the fourteenth‐century BC site of Amarna, Egypt, have been examined. A comparison is made between solvent extraction, saponification and the use of TMTFTH (m‐trifluoromethylphenyl)trimethylammomum hydroxide, used here for the combined extraction and derivatization of ceramic‐absorbed organic residues. Extracts were studied using gas chromatography and gas chromatography‐mass spectrometry. The extraction of fatty acids from small ceramic samples has established concentration gradients of absorbed organic matter from the inner to the outer surfaces of the sherds.     

The Application of Steroidal Biomarkers to Track the Abandonment of a Roman Wastewater Course at the Agora (Athens,Greece)*

A subterranean, stone‐built, sediment‐filled culvert discovered during excavations at the Agora (Athens, Greece) was dated to the Roman period on the basis of its characteristic construction and associated finds, including coins. The location of the culvert relative to other adjacent watercourses and an ancient river bed suggested that the structure was a sewer. This was confirmed through a multi‐molecular biomarker approach based on analysis of the bile acids associated with sediment filling the sewer, using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The acid fraction contained predominantly deoxycholic and lithocholic acids, while the neutral steroid fraction comprised a complex mixture of Δ⁵ sterol and 5β‐ and 5α‐stanols, dominated by coprostanol, suggesting the presence of faecal matter of predominantly human origin. The concentrations of neutral and acidic faecal biomarkers were observed to vary in tandem, with the highest concentrations being found in the sediment at the base of the fill in the culvert. A reduction in concentration occurred with decreasing depth of the fill, with concentrations in the uppermost samples being little different from control samples of sediment taken beyond the confines of the culvert. The enhanced concentration of bile acids relative to 5β‐stanols compared with fresh human faeces must reflect the enhanced diagenetic stability of the former, thereby making bile acids the possibly preferred biomarker for this type of study. The quantitative data obtained suggest that the culvert fell rapidly out of use, possibly coinciding with the Slavic incursion in AD 582–3.     

IN VITRO DECOMPOSITION OF BONE COLLAGEN BY SOIL BACTERIA: THE IMPLICATIONS FOR STABLE ISOTOPE ANALYSIS IN ARCHAEOMETRY*

To understand biogenic collagen type I decomposition and to establish how diagenesis may bias archaeometric data, modern mammalian bone was inoculated with a selection of ubiquitous soil bacteria. The presence of exogenous microbial biomass in the inoculated specimens was then checked microscopically prior to collagen extraction. The experimentally degraded bone collagen showed altered amino acid compositions, attributable to the selective breakdown of certain amino acids by the bacteria. While both the bulk collagen extract and the single amino acids exhibited shifts to more negative δ¹³ C-values, enrichment was recorded for general δ¹³ N, and a depletion trend relative to unaltered collagen was observed for individual amino acid δ¹³ N. One explanation for the enrichment of the global δ¹⁵N-values is cleavage of peptide bonds, which leaves ¹⁵ N within the substrate, while the change of ¹³C is mostly due to the altered amino acid composition. On the other hand, possible repolymerization of cleavage products under experimental conditions may also be responsible for the depletion trend of individual amino acid δ¹³C- and δ¹⁵ N-values. This paper discusses the results as a basis for the development of a method for the reconstruction of the isotopic abundance of the original collagen, using the amino acid composition of the degraded product, the contribution of individual amino acids to its global δ-values and of isotope discriminations implied in the microbial decomposition.     

GC–MS ANALYSIS OF LIPIDS IN PREHISTORIC ROCK PAINTS AND ASSOCIATED OXALATE COATINGS FROM THE LOWER PECOS REGION,TEXAS*

The presumption that lipids were used as binders/vehicles in pictograph paints from southwestern Texas was tested using gas chromatography–mass spectrometry (GC–MS). A one‐step transesterification/derivatization procedure was used to convert bound and unbound fatty acids to fatty acid methyl esters for the analysis. Approximately 30 organic compounds were detected in the natural rock coating that encapsulates the paints, but there were no compounds unique to the paints. Moreover, the C_16:0 and C_18:0 concentrations in the paint samples were similar to the concentrations of these fatty acids in the rock coating, indicating that the compounds are native to the patina. Thus, lipid binders were either not used in the original paint mixture or have since degraded.     

Traces of Fatty Acids from a Byzantine Sounding Lead Recovered off the Israeli Coast

Fatty acids, typical to large herbivores, were isolated from a 7th century Byzantine sounding lead recovered from a shipwreck off Dor, an ancient anchorage in Northern Israel. The fatty acids survived by being sheltered in an anaerobic environment provided through a site formation process induced by the disintegrating wreck. Previously established identification criteria for fatty acids, absorbed in ceramics, were used to show that tallow was used in this navigational instrument in the Eastern Mediterranean during late antiquity.     

GC–MS ANALYSIS AND FATTY ACID RATIOS OF ARCHAEOLOGICAL POTSHERDS FROM THE WESTERN GREAT BASIN OF NORTH AMERICA*

The study of organic residues in archaeological pottery has focused on fatty acids due to their relative stability and longevity. However, even these compounds are subject to degradation, which makes assignment of residues to original foods problematic. This paper suggests that the use of ratios of fatty acids that degrade at roughly the same rate can be useful to identify very general categories of foods. It compares independent information on pot function based on ethnography and engineering/technological studies to that reconstructed based on extracted fatty acid ratios. The results support the notion that Great Basin pots were used primarily to boil seeds and that pot shape and pot function were related.     

GC/MS ANALYSIS OF FATTY ACIDS FROM ANCIENT HEARTH RESIDUES AT THE SWAN POINT ARCHAEOLOGICAL SITE*

Gas chromatography – mass spectrometry (GC/MS) is used to analyse soil residues from hearth sites in Swan Point, Alaska. An experimental hearth is also prepared by burning animal bones to study the characteristics of bone fires and the lipid residues that they leave embedded in soil. Hearth soil samples are derivatized with HCl in methanol to convert bound and unbound fatty acids into methyl esters. Concentrations of saturated fatty acid methyl esters in the samples are determined and their ratios analysed. The fatty acid patterns found in ancient campfires are consistent with burning bones of large ruminants as well as monogastric herbivores.     

BLOOD AS A BINDING MEDIUM IN A CHUMASH INDIAN PIGMENT CAKE

As part of a study of Chumash Indian pigments, some black pigment cakes have been examined. One pigment cake was characterized as soot by polarized light microscopy, and Fourier transform infrared microscopy showed that the binder was proteinaceous. Protein determination was followed by examination using gas chromatography-mass spectrometry analysis which showed a characteristic suite of amino acids to be present, proportionally similar to blood. The blood identification was confirmed by immunological analysis. The binder was shown to be a mixture of human and animal blood, the animal being pronghorn antelope. This is the first successful identification of a binding medium from a Chumash Indian pigment cake.     

Isolation and Isotopic Analysis of Individual Amino Acids from Archaeological Bone Collagen: A New Method Using Rp‐hplc

This paper presents a new method for the isolation and isotopic analysis of some individual amino acids from proteins. The technique and its constituent steps are discussed; then isotopic analyses of amino acids from several samples of bone collagen from the Late Roman site of Poundbury, Dorset, UK are presented. The applications of the method are discussed, as well as some advantages of this technique relative to other methods. Although developed for use with archaeological bone collagen, the technique is equally applicable to other proteinaceous materials. The use of reversed‐phase HPLC avoids problems of isotopic fractionation inherent in using ion‐exchange HPLC. Amino acids are isolated preparatively, allowing both carbon and nitrogen isotopic values to be measured on a single sample using CF‐IRMS. Since amino acids are isotopically analysed in an underivatized form (unlike GC‐C‐IRMS), the method also presents the possibility of collecting the CO₂ generated during CF‐IRMS: this would allow the subsequent dating by ¹⁴C‐AMS of individual amino acids isolated from archaeological samples.