Identification of activity area signatures in a reconstructed Iron Age house by combining element and lipid analyses of sediments

One promising analytical method used in household archaeology in addition to inorganic (element) geochemical analysis is that of organic (lipid) analysis applied to anthropogenic sediments. We use both methods here to review chemical imprints that might be useful for recognizing space use and identifying daily activities in a reconstructed Iron Age village at Lejre, Denmark. As documented in many previous studies, element analysis enabled separate activity areas to be distinguished, but the results could not be used to identify the specific activities pursued in the areas. A more qualitative identification of activity areas was possible through lipid analysis, however. The carbon chain distribution, studied for Average Chain Length (ACL), Carbon chain Diversity Index (CDI) and Carbon Preference Index (CPI), enabled a similar separation to be achieved as by element analysis, so that the same areas could be discerned in addition to the reference samples. The stable was distinguished by a substantial input of coprostanol and even more so by 24-ethylcoprostanol, indicating a faecal input from herbivores. Trace levels of these markers were also identified at the entrance, where the animals had passed through. The dwelling area, consisting of two adjacent rooms, could be identified by the sterol ratio (cholesterol/[stigmasterol + β-sitosterol + campesterol]). Lipids from an archaeological context have decayed further toward simpler compounds and become more difficult to identify. Some markers have however a better potential for survival. The results emphasize the importance of further studies on ethnoarchaeological material in order to recognize past activities by element analysis. Moreover, the combination of element and lipid analyses provided a tool that enabled all the separate areas to be identified and provided positive identification of the activities concerned in all areas except the smithy.     

A MULTI‐ANALYTICAL APPROACH FOR THE CHARACTERIZATION OF COMMODITIES IN A CERAMIC JAR FROM ANTINOE (EGYPT)*

This paper describes a multi‐analytical chemical study performed on the original, almost totally conserved, content of a small ceramic jar from the Antinoe archaeological site (fifth to seventh centuries ad, Roman Egypt) and now belonging to the archaeological collection of the Istituto Papirologico ‘Girolamo Vitelli’ (Florence, Italy). Scanning electron microscopy with an energy‐dispersive X‐ray spectrometer (SEM–EDX), Fourier transformed infrared spectroscopy (FTIR) and X‐ray diffraction (XRD) were all used to characterize the inorganic components of the archaeological material. The organic substances were analysed using FTIR, direct exposure mass spectrometry (DE–MS) and gas chromatography – mass spectrometry (GC–MS). The inorganic component essentially consisted of halite (NaCl). Among the NaCl crystals, lamellar elements were identified. They were chemically characterized by carbonato‐apatite and showed a concentric morphology typical of the scales of small fish. The most prevalent organic constituents of the sample were monocarboxylic acids, α,ω‐dicarboxylic acids, and cholesterol and its oxidation products. The organic material composition was consistent with the occurrence of lipids of animal origin. In addition, diterpenes related to pine pitch were also identified. The overall results suggest that the material recovered in the small ceramic jar found in Antinoe is a residue of fish‐based pickles such as garum, muria, allex and liquamen, which were commonly used in Roman times.     

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.     

Experimentally produced glass compared with that occurring at The Torr, NW Scotland, UK: vitrification through biotite melting

It is proposed that the vitrification in some Iron Age forts in NW Scotland can be explained through decomposition of micas (largely biotite) giving melts that react with or dissolve quartz and crystallise orthopyroxene and feldspars, so equating with the reaction biotite + quartz = sanidine + orthopyroxene + liquid. A sample of Moine semi-pelite has been experimentally melted at c. 850 °C demonstrating this breakdown reaction. A preserved thermal gradient across the sample reveals the progressive degradation of biotite towards the melting (upper) surface. Degradation is evident from the initial emphasis of mica cleavages in grains at the bottom of the sample, and then appearance and progressive increase in size of bubbles associated with biotite and melt towards the top of the sample. A chocolate-brown melt was produced as a coating on the upper surface and along micaceous layers. A near equivalent sample was located from the fort at The Torr that, whilst being more thoroughly affected by heat, with no unaffected biotite, preserved similar textures. Compositions of original Moine minerals are used to constrain the melts produced and melt evolution is tracked through quenched crystals. These include ternary feldspars as well as sanidine, spinels and orthopyroxene. Spot geochemical evidence demonstrates the heterogeneity of the melts, plus varying contributions of Ca and Na that could be attributed to the onset of reactions involving feldspars and other minerals from the original assemblage. It is thus concluded that a similar temperature to that of c. 850 °C derived in the experiment was reached in the vitrification process at The Torr in order to produce the glass observed.     

Does it come from the Pays de Bray? Examination of an origin hypothesis for the ferrous reinforcements used in French medieval churches using major and trace element analyses

A new methodology based on major and trace element analyses of slag inclusions is proposed to determine (or exclude) the provenance of iron artefacts. It is applied to verify if the Pays de Bray, a French area between Rouen and Beauvais, could have been an important supplier for the ferrous reinforcements used in the Middle Ages for the building of churches and cathedrals in these two towns. To this purpose, the behaviour of trace elements during both direct and indirect operating chains is studied combining experimental smelting and different analytical methods, such as SEM–EDS, ICP–MS, LA–ICP–MS and INAA, performed on archaeological samples. The chemical signature of the Pays de Bray iron ore and slag is determined considering MnO and P₂O₅ contents as a first rough filter and seven couples of trace elements. Then, the major and trace elements are analysed using the same methods in the slag inclusions of 32 artefacts from the Beauvais and Rouen churches, made by the bloomery process. The trace element signature of the inclusions from each artefact is compared with the ore from the Pays de Bray area. The iron used in the Rouen and Beauvais churches seems not to come mainly from the Pays de Bray.     

CHEMICAL CHARACTERIZATION OF ANCIENT MESOAMERICAN ‘COPAL’ RESINS: PRELIMINARY RESULTS*

So‐called ‘copal’ resins from nine Aztec/Mixtec turquoise mosaics have been subject to analysis by gas chromatography – mass spectrometry to examine their higher terpenoid composition with a view to botanical identification. Botanical specimens and modern commercial ‘copal’ resins were analysed for reference. A range of botanical sources for the resins was identified, including pine, Protium and possibly Bursera. The data reinforce the ambiguity in the use of the term ‘copal’ and demonstrate the need for further work on characterization of ancient Bursera resins.     

AN EVALUATION OF ANALYTICAL AND INTERPRETATIVE METHODOLOGIES FOR THE EXTRACTION AND IDENTIFICATION OF LIPIDS ASSOCIATED WITH POTTERY SHERDS FROM THE SITE OF SAGALASSOS,TURKEY*

Three lipid analysis methods were applied to extracts of archaeological potsherds from the ancient city of Sagalassos, south‐west Turkey. In the fatty acid methyl ester fraction, obtained by selective transesterification of acylglycerols, the ratio of methyl palmitate to methyl stearate was determined. Secondly, by means of gas chromatography– combustion–isotope ratio mass spectrometry (GC–C–IRMS), stable carbon isotope ratios were measured for the same methyl esters. Finally, triglyceride composition was determined via high‐performance liquid chromatography–mass spectrometry (HPLC–MS). All three methods can be used to trace the origin of animal fat. Agreement between them is reasonable, especially in recognizing ruminant adipose fat. One sample was found to be of dairy origin using both GC–C–IRMS and HPLC–MS. The advantages of the various methods are discussed. Variations in lipid composition were observed between samples from different periods and excavated in diverse areas within the city of Sagalassos.