Hu New Developments in Isotope and Trace Element Analyses

Posted on February 1, 2017


Archaeology has been revolutionised by many scientific techniques like carbon dating and XRF. One that has really had an impact on archaeology is the examination of isotopes. These was a session at the EAA conference that explored the topic and we managed to film it:

Session Abstract:

Thursday, 1 September 2016, 14:00-18:30
Author – Plomp, Esther, Free University Amsterdam, Amsterdam, Netherlands (Presenting author)
Co-author(s) – Jaouen, Klervia, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
Co-author(s) – Brems, Dieter, University of Leuven, Departement of Earth and Environmental Science, Leuven, Belgium
Keywords: chemistry bioarchaeology, isotope, trace element

Trace element and isotope analyses are powerful tools for reconstructing past human diets, mobility and environments as well as establishing chronologies and provenancing materials and artefacts. With the recent developments in measurement methodologies for mass spectrometry during the 90’s, it is now possible to precisely and accurately measure stable isotope compositions of new elements (e.g. B, Ca, Cu, Fe, Hg, Mg, Nd, Pb, Sb, Sr, Zn) in all kind of materials, opening up new perspectives for archaeological sciences. This session aims to bring together researchers that are working on new techniques as well as scholars that employ traditional techniques using novel approaches to interpret their data (for example the interpretation of multiple isotope/trace element analyses of the same sample). We invite contributions that focus on a variety of materials, such as human or animal tissues (e.g., bone, tooth, blood, shells), archaeological materials (e.g. raw materials, ceramics, glass artefacts, metals, building stones) or environmental samples from archaeological sites (e.g. speleothems, soils). These contributions should show the potential of heavy stable and radiogenic isotopes (Nd, Pb) for archaeological sciences or present new developments in light stable isotope analyses (C,H,O,N,S). Studies that integrate isotopic/trace element and archaeological data in an innovative way are particularly welcomed, as well as discussions on the potential and limitations of these analyses. We hope that this session will demonstrate that these new techniques hold great potential for a more integrated interpretation of the archaeological record and that it is possible to get relevant archaeological information which is currently beyond reach.

Zinc isotope compositions of bone and dental enamel and their relationship to diet
Author – Dr. Jaouen, Klervia, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany (Presenting author)
Co-author(s) – Szpak, Paul, University of British Columbia, Vancouver, Canada
Co-author(s) – Beasley, Melanie, University of California, San Diego, United States of America
Co-author(s) – Herrscher, Estelle, LAMPEA, MMSH, Aix en Provence, France
Co-author(s) – Colleter, Rozenn, INRAP, Rennes, France
Co-author(s) – Balter, Vincent, ENS Lyon, Lyon, France
Co-author(s) – Schoeninger, Margaret, University of California, San Diego, United States of America
Co-author(s) – Richards, Michael, University of British Columbia, Vancouver, Canada
Keywords: archeological sciences, dietary tracer, nontraditional isotopes

Isotopic analyses of carbon and nitrogen are conventionally employed in bioarcheology for dietary reconstructions. These elements are however contained in the bone collagen which deteriorates over time. Mass spectrometry advances now allow trace element isotope analyses of bioapatite. First studies on Zn isotopes in blood showed its potential as a new dietary tracer. This contribution aims at testing the influence of diet on Zn isotope compositions of bone and teeth. We investigated the Zn isotopic variability in bone and tooth enamel of mammals and archaeological human populations characterized by various diets, environment contexts (arctic, arid, temperate) and historical periods. The samples were purified by column chromatography and the Zn isotopic ratios were measured using MC-ICP-MS. The isotopic composition of traditional food tracers (d13C and d15N) has been assessed in parallel. We will show that the Zn isotopic composition in the bones and teeth is strongly influenced by the trophic level, but that some dietary and environmental factors can generate additional variability. We will discuss the advantages and limitations of this new tracer by comparing its performance to that of classic isotope analyses.
Hydrogen stable isotope ratios measured in bone collagen from Danish prehistoric samples

Author – van der Sluis, Laura G.1 (Presenting Author) School of Geography,
Archaeology and Palaeoecology, Queen’s University Belfast, United Kingdom
Co-Author(s) – Ogle, N., School of Planning, Architecture and Civil Engineering, Queen’s University Belfast, United Kingdom
Co-Author(s) – Reimer, P.J., School of Geography, Archaeology and Palaeoecology, Queen’s University Belfast, United Kingdom
Keywords: Hydrogen, Bone, palaeodiet

Palaeodietary studies commonly analyse 13C and 15N ratios in archaeological bone to infer past dietary habits, although 15N ratios can be influenced by a range of factors other than diet (aridity, manuring, soil conditions, etc.). 2H ratios have been shown to function as trophic level indicator (Birchall et al., 2005; Reynard and Hedges 2008), which can be very useful to aid our interpretation of the 13C and 15N ratios and improve our understanding of palaeodietary habits and subsistence practices. Hydrogen in organics consists of a non-exchangeable and exchangeable fraction; the latter will equilibrate with atmospheric hydrogen with atmospheric hydrogen from water vapor in the lab environment, resulting in meaningless values.This fraction needs to be calculated in order to obtain the non-exchangeable fraction which represents the true values. By applying a 2- stage equilibration method, sample specific and process specific factors influencing exchange rates are compensated for (Meier-Augenstein et al., 2011). Recently developed standards packed in silver tubes containing water of known isotopic composition (Qi et al. 2010) can be analysed alongside solid samples in the same run, which is essential to avoid scale compression. While this method is not novel (Bowen et al., 2005; Meier-Augenstein et al., 2011; 2013), its application with the use of Qi et al.’s standards to archaeological material is new. In this study we subjected bone collagen samples from prehistoric periods from the Limfjord region in northern Denmark spanning the Mesolithic to the Viking Age to a two-stage equilibration method using the silver tube standards to obtain absolute 2H ratios from the non-exchangeable hydrogen fraction.
Birchall et al., 2005. Journal of Animal Ecology 74.
Bowen et al. 2005. Rapid Comm. In Mass Spectrometry 19.
Meier-Augenstein et al. 2011. Rapid Comm. In Mass Spectrometry 25. Meier-Augenstein et al. 2013. Bioanalysis 5.
Qi et al. 2010. Rapid Comm. In Mass Spectrometry 24.
Reynard and Hedges 2008. Journal of Archaeological Science 35.

Stable isotope ratios and trace elements in modern mammal tooth enamel
Author – Dr. De Winter, Niels, Vrije Universiteit Brussels, Elsene, Belgium (Presenting author)
Co-author(s) – Snoeck, Chrstophe, Vrije Universiteit Brussels, Elsene, Belgium
Co-author(s) – Goderis, Steven, Vrije Universiteit Brussels, Elsene, Belgium
Co-author(s) – Van Malderen, Stijn, Ghent University, Ghent, Belgium
Co-author(s) – Vanhaecke, Frank, Ghent University, Ghent, Belgium
Co-author(s) – Claeys, Philippe, Vrije Universiteit Brussels, Elsene, Belgium
Keywords: bioapatite, isotopes, trace elements

Bioapatite from mammal tooth enamel is a popular biomineral used in the reconstruction of palaeoenvironment and palaeodiet. It records information about the animal’s environment and diet on a sub-annual scale and is proven to be highly resistant to diagenesis, allowing the preservation of its original chemical composition through archaeological and geological timescales. In this study, stable carbon and oxygen isotope analysis are used as a stepping stone to investigate the use of other chemical proxies for the reconstruction of environment and diet from mammal teeth. Concentration profiles of trace element distributions (measured with µXRF and cross-validated with Laser Ablation ICP-MS) and stable isotope ratios ( 13Cap, 18Oc & 18Op) are combined to test the reliability of trace element profiles from mammal teeth in recording seasonal changes in environment and diet of the animal.
A method is presented that links the various geochemical records within a tooth sequence using mineralization sequences and oxygen isotope seasonality. This way, a 3 year trace element and stable isotope record from horse tooth enamel is created showing seasonal variation in trace elements and isotope ratios linked to changes in climatic conditions and diet through the animal’s lifetime. This study shows how an entire new set of trace element proxies, that can be measured quickly and non-destructively, may yield information on palaeoenvironment and palaeodiet. These trace element measurements yield information from precious archaeological samples that could otherwise be obtained solely through destructive sampling. The versatility of the µXRF and LA- ICP-MS methods opens up a wide range of applications for trace element analysis in archaeology.

The geochemical relationship between soil, plant and streamwater; implications for migration studies
Author – Ryan, Saskia, Trinity College Dublin, Dublin, Ireland
Co-author(s) – Crowley, Quentin, Trinity College Dublin, Dublin, Ireland
Co-author(s) – Snoeck, Christophe, Vrije Universiteit Brussel, Brussels, Belgium (Presenting author)
Co-author(s) – Babechuk, Michael, Trinity College Dublin, Dublin, Ireland
Keywords: Geographical discrimination, Multi-element composition, Strontium isotopes

Strontium isotope (87Sr/86Sr) and rare earth element (REE) analyses of rock, the leachable fraction of soil, plant and surface waters are applied as chemical proxies to assess chemical reservoir interactions, element bioavailability and geographic variability. These processes are the basis for geographic discrimination and associated archaeological provenancing. 53 biosphere samples were collected from a small geographic area in Co. Meath, a region of Ireland that has highly variable bedrock and surficial geology and hosts significant archaeological sites including, Newgrange, the Hill of Tara and Knowth. These multi-element and isotope data geochemically constrain this region and the high degree of spatial variability in 87Sr/86Sr highlights the inherent requirement for high-density sampling in order to isotopically characterise distinct reservoirs. The results of this study provide a baseline of biosphere geochemical data that can be applied to archaeological studies examining the past migration of populations in this archaeologically important region.

The potential of large-scale seasonality studies, results from the Farasan Island shellmound complex
Author – Dr. Hausmann, Niklas, Foundation for Research and Technology – Hellas, Heraklion, Greece (Presenting author)
Keywords: LIBS, Seasonality, Shellmound

The Farasan shell mounds are one of the largest traces of the Arabian Neolithic Period, with over 3,000 sites having accumulated between 7,000 and 4,000 cal BP. Seasonality data based on stable oxygen and carbon isotopes have determined year-round exploitation of shellfish. Additionally, they revealed patterns of seasonal stratification within individual layers. This was used to determine sub-annual accumulation rates, exploitation intensity, and degrees of bioturbation within the stratigraphy. This dataset is now being analysed more thoroughly by using Laser Induced Breakdown Spectroscopy (LIBS). LIBS is a rapid and cost-effective laser ablation method, that is able to measure the elemental composition of shell carbonates to determine season of death. By providing a high sampling resolution (<100µm) and short processing time, large sample sizes can be analysed in great detail. In turn, it allows us to analyse exploitation and accumulation patterns of the Farasan Islands in more detail. More specifically, this study aims to answer questions regarding (1) how analysing a larger number of shells per layer changes the interpretation of site seasonality, (2) whether seasonal layering of shell deposits are singular or repeated events, and (3) how accumulation rates based on seasonality can vary throughout the deposit and tells us more about the processes behind shell deposition.

Elemental and Sr/Nd isotopic investigation of late Hellenistic to early Roman glass bowls and sand raw materials from Lebanon
Author – Brems, Dieter, KU Leuven, Leuven, Belgium (Presenting author)
Co-author(s) – Freestone, Ian, University College London, London, United Kingdom
Co-author(s) – Griffiths, Dafydd, University College London, London, United Kingdom
Co-author(s) – Degryse, Patrick, KU Leuven, Leuven, Belgium
Keywords: Natron glass, Sand raw materials, Isotopes

Excavations in the Souks area of Beirut, Lebanon, not only revealed large amounts of glass artefacts from the Hellenistic to the Islamic period1 but also remnants of primary tank furnaces, dating to the early 1st century CE2. We determined the major elemental compositions of 66 mid-2nd century BCE – early 2nd century CE cast glass bowls from Beirut via electron microprobe. 41 beach sand samples taken along the coastline of Lebanon were analysed for their major elemental compositions via ICP-OES. A selection of sand and glass samples were subjected to Sr and Nd isotopic analysis. Results were compared to the composition of glass from the tank furnaces3 and Lebanese sandsto investigate the possibility of a localorigin. All glasses were soda-lime-silica in composition, with natron as a flux. Strongly coloured glass was coloured with Co, Cu and Mn. Pale coloured glass has varying MnO, up to 1.9%, suggesting that they were intended to be colourless. Colourless bowls can be divided into three groups: Mn-, Sb- and mixed Mn-Sb-decoloured glass. All Mn-decoloured, pale and strongly coloured vessels have closely similar base glass compositions to glass from the tank furnaces3, suggesting local production and working. The Sb-decoloured glass was made from a different sand source with higher Si2O and lower Al2O3 and CaO. Mixed Mn-Sbdecoloured glass has intermediate compositions, suggesting they are theresult of recycling. Sr and Nd isotopic analyses confirm the different primary origin of the Sb-decoloured glass. The isotopic signatures of the other glasses correspond well to those measured in some of the Lebanese sands, suggesting they were indeed produced locally.
1 S. Jennings, Vessel glass from Beirut (Bey 006, 007 and 045), Berytus Archaeological Studies 48-49, 2006.
2 I. Kouwatli, H.H. Curvers, B. Stuart, Y. Sablerolles, J. Henderson, P. Reynolds, A pottery and glass production site in Beirut (BEY 015), Bulletin
d’Archéologie et d’Architecture Libanaises 10, 103-130, 2008.
3 J. Henderson, Ancient glass: An interdisciplinary exploration, Cambridge University Press, pp. 423, 2013.

Iron isotopes as a new tool for ancient metal tracing: comparison with classical tracing methods

Author – PhD student Milot, Jean, Géosciences Environnement Toulouse, Toulouse, France (Presenting author)
Co-author(s) – Poitrasson, Franck, Géosciences Environnement Toulouse, Toulouse, France
Co-author(s) – Baron, Sandrine, TRACES Laboratory, Toulouse, France
Keywords: Ancient metals, Iron isotopes, Provenance studies

The development of precise and accurate analytical techniques over the last decades has allowed expanding the range of methods for ancient metal tracing. Elemental and isotopic analyses are now widely used for this purpose. For a relevant archaeological interpretation, metallurgical processes must be taken into account, and analyses must be performed on archaeological ore, slag and metal. So far, isotopic methods were rather employed for non-ferrous metal tracing [e.g. 1] whereas elemental analyses were used for ferrous metal tracing [e.g. 2]. However, currently used elemental and isotopic methods show limitations, which underline the need to develop new tracers to complement existing ones3.
We used Fe isotopes as a new tool for ancient metal provenance studies. Isotopic ratios 57Fe/54 Fe and 56Fe/54Fe were measured using a Multiple Collector Inductively Coupled Plasma Mass Spectrometer after sample dissolution and Fe purification4. We first developed this approach by analysing materials from archaeological experiments on iron ore reduction. In order to compare our results with classical tracing methods, we also analysed the Fe isotope compositions of archaeological materials whose provenance hypotheses have been established with trace elements analyses of slags. Furthermore, some materials coming from different regions of ferrous and non-ferrous metal production were analysed to assess the tracing potential of Fe isotopes compared to trace elements and Pb isotope analyses. Our first results show that the bloomery process does not induce Fe isotopic fractionation, i. e., the signature of metals and slags reflect that of their corresponding ores. Moreover, Fe isotopes analyses tend to confirm the provenance hypothesis of ancient artefact established with trace elements analysis of slags. The results obtained so far suggest that Fe isotopes are a relevant tracer for archaeological materials, which can be applied to ferrous metals. The combination of this new method and the more classical ones involving trace elements or Pb isotopes analysis could allow to refine previous provenance hypotheses of ancient metals.
1 S. Klein, C. Domergue, Y. Lahaye, G.P. Brey and H.-M. von Kaenel, 2009, The lead and copper isotopic composition of copper ores from the
Sierra Morena (Spain), Journal of Iberian Geology 35 (1), 59-68.
2 M.-P. Coustures, D. Béziat, F. Tollon, C. Domergue, L. Long and A. Rebiscoul, 2003, The use of trace element analysis of entrapped slag
inclusions to establish ore–bar iron links: examples from two Gallo-Roman ironworking sites in France (Les Martys, Montagne Noire and Les
Ferrys, Loiret), Archaeometry 45, 599–613.
3 S. Baron, M.P. Coustures, D. Béziat, M. Guérin, J. Huez and L. Robbiola, 2011, Lingots de plomb et barres de fer des épaves romaines des
Saintes-Maries-de-la-Mer (Bouches-du-Rhône, France): Questions de traçabilité comparée, Revue Archéologique de Narbonnaise 44, 71-98.
4 F. Poitrasson and R. Freydier, 2005, Heavy iron isotopes composition of granites determined by high resolution MC-ICP-MS, Chemical Geology
222, 132-147.

Iron Slag and the Quest for Provenance

Author – Bauzyte, Ema, Aarhus, Denmark (Presenting author)
Keywords: Iron, Provenance

Over the past few decades our growing ability and competence in determining the provenance of archaeological artefacts using scientific methods has been one of the most exciting developments in the field of archaeological science. However, when it comes to iron and attempts to determine its geological origin, more questions than answers have been posed. The 3-year research project launched by UrbNet centre based at the University of Aarhus is facilitating the collaboration of geologists and archaeometallurgists and aims to employ a multi-analytical approach in order to determine the extent to which the chemical composition of iron ores is preserved in the iron slag. We investigate the slag from east Africa Swahili coastal sites, presenting the potential for both, local and imported material. The artefacts are subjected to petrographic, metallurgical, elemental and isotopic analyses in order to determine the validity of methods and the feasibility of further analyses. Thermal experiments are devised and performed so as to replicate thermodynamic processes and define their significance in altering elemental and isotopic ratios. We hope to share the preliminary results and stimulate conversation on potential further approaches that may be taken in order to improve the data and overcome some of the challenges we are facing.

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