X-ray and tomography for archaeology

This is why the use ofscientific X-ray imaging(radiography and tomodensitometry) has become essential for the study of closed forms or archaeological artifacts trapped in their gangue of sediments. By offering both laboratory and on-site analyses, CIRAM provides complete coverage of archaeological artifacts, and enables virtual excavations that do not damage these heritage remains in any way.

Reveal the inner structure of objects with high-definition scientific imaging

Thanks to high-definition scientific imaging techniques, we will be able to reveal the internal structure of objects, identify the nature and use of the artifact, define the degree of corrosion of metal alloys and the resulting degree of conservation.

Portable digital X-ray radiography

Our X-ray radiography equipment is digital and portable. With this latest-generation tool, we can take images in situ, without moving the objects in the storerooms, and therefore without risking damaging them. Our digital acquisition system also enables us to obtain X-ray images in real time. These snapshots enable us to adapt observation modes and viewing angles to obtain an optimum view of the objects.

Large digital detector for simultaneous examination of multiple objects

We also have a large digital detector, with a sensitive surface area of 1600 cm² (40 x 40 cm). This enables us to examine several objects at the same time, thereby reducing the cost of analysis. Our X-ray sensitive plate has a resolution of 5.5 million pixels, generating high-definition images. Last but not least, the study of large objects is entirely possible thanks to the digital reconstruction we carry out in post-production.

CT scan for 3D visualization

CT scanning complements X-ray radiography by adding a third dimension. This type of imaging enables 3D visualization, revealing the internal structure of objects without the need for sampling or invasive techniques. CT scans can also provide information on the techniques used to manufacture objects, or on the degree of conservation of materials.

Optimizing the use of CT scans for virtual excavations

By optimizing the use of CT scans, it will be possible to carry out virtual excavations and discover the contents and stratigraphy of a cinerary urn, for example. Image processing in contrast, false color, MIP or surface mode enhances visualization of the internal structure and identification of the elements present. Finally, video files can be extracted to make the most of these virtual excavations.

Scientific imaging and CT scans for heritage preservation and enhancement

Scientific imaging methods and CT scans are part of the overall approach to the study of archaeological artifacts, and contribute to their preservation, conservation and enhancement.

Complementary characterization for dating

Characterization (chemical, physical and imaging) of archaeological objects is a complementary approach to carbon-14 or thermoluminescence dating.

Since 2005, CIRAM has specialized in the analysis and dating of archaeological artifacts, art and heritage objects and historic monuments.

CIRAM, the laboratory where chemists, physicists and archaeologists work together. Our multi-disciplinary approach enables us to respond to archaeological issues as well as heritage restoration and conservation concerns.

Archaeometry: a constantly evolving discipline

Archaeometry is a relatively recent discipline in the world of science. Born in England in the 1950s, it developed in France from the 1970s onwards, and is still evolving today. In terms of research issues, it is associated with archaeology, history and art history. Its ambition is to document the life of past populations through the study of the material traces they left on the environment or through their material production. The adaptation of analytical techniques has made it possible to observe the organization and composition of matter on a microscopic scale, to determine the date of use of a material, and to read the geochemical signature of a raw material.

Wall paints are composite materials in the sense that they contain different types of components. These include the mineral substrate, which is likely to have been coated, and the various preparatory and pictorial layers, which are composed of mineral and organic materials. This is why we adapt our analysis techniques to the type of material involved.

Analyzing wall paintings: techniques and methods

Observation of the stratigraphy of the pictorial layers by optical and electron microscopy will enable us to define the succession of colors used, as well as their chronology. In addition, chemical analysis of the pigments will provide a relative dating of the different applications. For example, the identification of ultramarine blue (polysulfurized sodium aluminosilicate) will indicate that this coating could only have been applied from 1830 onwards. This is a terminus post quem. This stratigraphic study will make it possible to identify the original color of a mural and characterize the various restoration phases undergone.

Analysis of organic binders by infrared spectrometry or chromatography will enable us to define their nature, e.g. lipidic or proteinic, and more precisely oil or animal glue, for example. Identifying binders is also an important step in the process of restoring and conserving wall paintings.

Studying the deposits present on the surface of wall paintings will also be an essential aid to restoration. These deposits can be of various natures, either mineral or biological. Deposits of soluble salts can cause serious damage to painted works. They are identified by ion chromatography, and their nature is linked to their origin. For example, the presence of nitrates is due to contaminated water underlying the foundations and to bacterial activity. These are capillary effects that allow nutrients produced by nitrogen bacteria to rise to non-negligible heights. Nitrate salts, which are highly soluble, migrate easily. Biological deposits correspond mainly to molds or fungi, bacteria, algae or yeasts. Identifying them is a prerequisite for precisely defining the treatments to be used to guarantee the conservation of wall paintings.

CIRAM, a specialist in carbon-14 dating and archaeomaterial analysis, also offers acomplete analysis of wall paintings. These studies remain essential in the process of restoring and conserving cultural property.

 A brief history of metallurgy
 

Still widely used today, copper was one of the first metals to be mined in prehistoric times. Indeed, copper metallurgy began as early as the third millennium BC. Later, the Bronze Age defined the production of an alloy of copper and tin. We can't talk about metal in general, as there are many differences between bronze (an alloy of copper and tin), brass (an alloy of copper and zinc), cast iron, silver and gold. Copper alloys are particularly interesting, as their use dates back to the origins of our civilizations, and continues to the present day.

Study of chemical composition by optical microscopy and scanning electron microscopy
 

As bronzes cannot be dated directly, we have to look for usable chronological markers, such as technical clues, the degree of corrosion and the composition of corrosion products.

The most relevant approach for bronze objects remains the observation and study of chemical composition by optical microscopy and scanning electron microscopy (SEM-SEM).

Study of metal microstructure
 

The first step is to study the metal's microstructure, which will provide information on manufacturing techniques. For example:

- The presence of dendrites characterizes a melt;

- Flattened and aligned inclusions are evidence of hammering;

- A very regular alignment corresponds to lamination.

Metal composition study
 

The second step is to study the metal's chemical composition. Elemental analysis of concentrations of major and minor elements, and possibly the presence of traces, enables the nature of the alloy to be identified. The main major elements are copper, tin, zinc and lead. Minor elements are iron, arsenic, antimony, nickel, etc. Trace elements are numerous and vary in space and time.

Characterization of metal objects and corrosion analysis
 

The final stage in the characterization of a metal object is the analysis of its corrosion. This is called patina. While this term implies a surface approach, the study of corrosion is concerned in particular with the nature of surface corrosion products (the patina proper), but also with the development of corrosion processes within the alloy.

A copper alloy that is hundreds or thousands of years old will have undergone numerous attacks from the environment: humidity, temperature variations, the development of micro-organisms... These elements lead to the degradation of the metal and therefore to corrosion. The most characteristic signs of natural corrosion include the following:

- Grain boundary alterations ;

- Dendritic, inter-granular or trans-granular corrosion ;

- Mineralization.

Corrosion products come in many forms, depending on the composition of the metal and the nature of the environment. They include cuprite (copper oxide), azurite and malachite (copper carbonates), atacamite, paratacamite and nantokite (copper chlorides), tin oxides, lead salts... Associated with these corrosion products, we can also detect landfill sediments, plant residues, microorganisms...

It is crucial to bear in mind that the study of a metal's chemical composition and degree of weathering provides indirect technical and chronological clues. It is impossible to obtain quantifiable chronological information on metal.

CIRAM laboratories, specialists in materials authentication
 

CIRAM, a specialist in the dating and analysis of archaeomaterials, offers a comprehensive interpretation. We share our results and discuss their interpretation with you, to explain the relevance of our research, particularly for metal objects.

By combining cutting-edge technologies such as infrared spectrometry, Raman spectrometry and chromatography, our scientists are able to detect and identify the organic remains found in ancient amphorae and pottery. The techniques developed by CIRAM enable us to characterize oils, fermented beverages, resins, fats and perfumes, so as to understand the dietary and cosmetic habits of ancient peoples.

Organic residues: understanding old habits and practices

Organic residues found in dishes, vases and flasks provide clues to food customs and ancient cooking methods, for example. But they can also provide information about trade in Antiquity or the Middle Ages, as well as ancestral burial practices. CIRAM laboratories have an analytical network that covers a wide spectrum of investigations, from the identification of major product families (oil, fat, resin, etc.) to the discovery, in the best of cases, of ancient cooking recipes.

Organic residue analysis methods

Fourier transform infrared spectroscopy, in ATR mode or under microscopy, is used to identify the major families of organic compounds. For example, the presence of oil, animal fat or natural resin can be characterized. Mineral matter, however, can provide a spurious signal, preventing identification of the organic compounds present. For this reason, infrared spectrometry will usually be used as a preliminary step. CIRAM teams will generally couple FTIR spectrometry with other analysis techniques, such as chromatography or Raman spectrometry.

GC-MS coupling to locate and identify substances

Gas chromatography (GC) coupled with mass spectrometry (MS) is the technique dedicated to the study of organic compounds. Chromatography separates compounds in a sample, while mass spectrometry identifies compounds according to their mass. This GC-MS coupling enables the precise identification and quantification of many substances present in very small quantities, or even in trace amounts. Using GC-MS analysis, our scientists can characterize most of the molecules present in an archaeological mixture or organic residue. It is the nature of these molecules, combined with their concentration, that enables us to trace them back to the material used: olive oil, walnut starch, animal fat, tannin...

Complementary analytical techniques for the analysis of certain residues

Although Raman spectrometry is more suited to the study of mineral matter, it is nonetheless an interesting method for archaeometry, as it is non-invasive and requires no sample pre-treatment.

This analysis provides very good spatial resolution, making it possible to study samples on a very small scale (spots of a few µm). Raman spectrometry can be used on its own, or in conjunction with FTIR spectrometry or GC-MS chromatography. In fact, the residues found in ancient pottery are so complex that it is generally necessary to use different complementary analytical techniques.

Carpology for the study of seeds and fruits that have been discovered

Carpology is the study of seed and fruit remains found in ancient containers or archaeological sediments. Analysis of these plant residues provides information on human activities and ancestral lifestyles. Even when charred, CIRAM scientists are able to identify the nature of these seeds, and thus understand their use and reconstruct environments.

Palynology, the study of pollen and spores

Palynology is the study of pollen and spores released by plant species. Coupled with carpology and anthracology, these techniques enable us to reconstruct environments and climates. Observations made using light microscopy or electron microscopy will make it possible to determine the size and shape of pollen grains or spores, the number and shape of apertures, ornamentation, wall structure... and thus define the plant family, genus and, in the best case, species.

CIRAM laboratories, specialists in carbon-14 dating and archaeometric analysis.

CIRAM, a specialist in carbon-14 dating and archaeomaterials analysis, offers a meticulous examination of organic residues. To deliver relevant and accurate results, we interpret the results and remain at your disposal to discuss hypotheses according to your needs.

We are well aware of the time constraints to which archaeologists are subject, which is why we propose standard turnaround times of 3 months for TL (depending on the laboratory's production load) and try to keep OSL turnaround times as short as possible. Luminescence dating methods are less well known than carbon 14, and their use remains limited in historical archaeology. They mainly refer to thermoluminescence (TL) and optically stimulated luminescence (OSL) dating.

TL dating, to date the last heating of materials

TL (thermoluminescence) is used to date the last heating of a material, whether clay or hearthstone (quartzite, flint, sandstone, etc.). This method is frequently used in prehistoric times, when other types of remains are less abundant.

However, applications have also been tested on materials more closely related to historical issues, such as architectural terracotta. One of the most frequent uses is in kiln dating, where TL is one of the most suitable methods, along with archaeomagnetism.

A complementary study using OSL dating

As a complement to thermoluminescence dating, OSL offers additional possibilities. In fact, this method makes it possible to date the last exposure of a material to light. It's not hard to imagine how interesting it can be to date a stratigraphic sequence on a site. Numerous applications have been developed in response to problems associated with the archaeology of historic and protohistoric periods. For example, OSL is used to date the installation layer of a megalith, the sealing of mortar in masonry...

The chronological range of these methods extends from a few hundred to a million years, enabling them to be used on any type of archaeological site.

The basic principles of luminescence dating

Luminescence dating methods are based on common principles. They rely on the ability of minerals (mainly quartz and feldspars) to record ambient radioactivity over time. The radioactivity absorbed comes from the earth's surface, essentially from the decay of three radioelements:

• Potassium (K);
• Uranium (U) series;
• Thorium (Th).

The emission of particles (alpha and beta) and gamma radiation from these three elements occurs regularly over time, and constitutes what is known as the dose rate. This annual dose (I) is supplemented by the effects of cosmic radiation, which vary according to burial depth, altitude and latitude. The quantity of radioactivity absorbed at the moment of measurement is called the archaeological dose (Qnat) or equivalent dose (De).

It is the ratio of these two quantities (Qnat and I) that gives the age between the last heating of the object and its study in the laboratory:

When measured in the laboratory, the crystals under study emit light (or luminescence). The amount of luminescence emitted is proportional to the amount of radiation absorbed by the sample since it was last heated. For OSL, thermal stimulation is replaced by optical stimulation. Our laboratory scientists measure luminescence emissions by illuminating the crystals.

From field to laboratory: analysis by CIRAM laboratories

As explained above, it's important to measure two quantities to obtain luminescence dating: the archaeological dose and the annual dose. To do this, several steps are required, starting in the field in the best of cases.

Operational procedure in the field, meticulous sampling for accurate results

During the excavation operation, several samples and measurements are taken. It's important to sample what you want to date: sediment from a stratigraphic sequence, hearth hearth, heated flints... the sampling is substantial, around 1kg.

Then, to calculate the annual dose, two alternatives are possible:

• Gamma and cosmic radiation can be measured at the sampling point using a gamma probe;
• Or the radioactive environment can be "reconstructed" in the laboratory, using sediments collected within a 30 cm radius of the sample.

The depth of burial of the sample must also be available to enable dosimetry calculations to be carried out as accurately as possible.

Laboratory operating procedures

The first step is to choose (if possible) the material on which to carry out the experiment. The abundance and granulometry of the crystalline species used (mainly quartz and feldspar) need to be determined, in order to choose which protocol to use.

Based on this determination, CIRAM scientists choose either the large quartz inclusion technique or the small polymineral inclusion technique. This choice determines the material preparation stages, which can last from a few days to several weeks.

Thermoluminescence measurements involve three steps for optimal dating (Qnat and I measurements):

• Measurement of natural luminescence, Q nat, with the addition of laboratory-controlled irradiation doses, also known as first reading;
• Measuring the radiochemical composition of sediment using low background gamma-ray spectrometry;
• Determination of the annual irradiation dose, I, by a posteriori reconstruction.

Once the operational procedure is complete, our scientists process and interpret the results.

Processing TL and OSL results

TL and OSL provide dates that are independent of any external reference. The only factors influencing uncertainty are intrinsic to the measurements and the quality of the initial sample. In the case of TL, the optimum uncertainty can be as low as 5%, and 3.5% for OSL. Whether used alone or in conjunction with other methods, luminescence dating, despite its high accuracy, does not always enable two distinct archaeological facts to be finely discriminated.

In this context, the use of statistical processing methods seems particularly appropriate.

These allow :

• To propose a more precise chronological phasing of the sequence of archaeological structures,
• Propose average phase dates with reduced uncertainties,
• But also to refine each individual dating.

To optimize these treatments, the stratigraphic relationships observed in the field are of prime importance. Indeed, if two datings present partial overlaps and belong to stratigraphic units associated by a relationship of anteriority/posteriority, these overlaps are considered impossible.

The chronological model is based on Bayesian statistics, and the date probability fitting functions are determined by Monte-Carlo simulation.

Efficient analysis and comprehensive critical synthesis with CIRAM

The analytical team's university training, dedicated to the physical and chemical analysis of archaeological materials and in particular to luminescence dating, provides a solid basis for experimentation. In addition, CIRAM's technological autonomy is guaranteed by its ownership of equipment for measuring TL and OSL. This, combined with CIRAM's high level of responsiveness and availability, means that TL dates can be obtained within 3 months, depending on the laboratory's production load.

CIRAM has also developed a scientific partnership with a nuclear research center (University and CNRS), for the analysis of the radiochemical composition of materials. CIRAM goes beyond simply obtaining dates, and is committed to providing a complete critical synthesis of the results and proposing the best possible archaeological exploitation.

Carbon-14 dating is not the only scientific technique used in archaeology. Archaeometry encompasses many other investigative and dating techniques. Anthracology is a method practiced by CIRAM laboratories. For complete results, we study charcoal and identify wood species. Anthracology is one of the pillars of archaeobotanical studies, enabling us to understand how ancient human societies used materials. Anthracology also reveals the origin of wood samples, enabling us to differentiate between heartwood, branches and twigs. This makes it possible to avoid the "old wood" effect in carbon-14 dating.

Strict protocol and sophisticated equipment for anthracological studies 

Anthracological studies require a meticulous sample preparation protocol. After refreshing surfaces with a razor blade, charcoal is analyzed anatomically along three axes: transverse, tangential and radial. Observation of the anatomical elements in all three dimensions enables us to determine the family and genus, and more rarely the species.

Observations are made using a stereomicroscope (Olympus® SZ61 binocular loupe) and a dark-field metallographic microscope (Olympus® BX53M), under "natural" light (calibrated white light), coupled with digital cameras.

To characterize the coals, the following information is collected:

CIRAM laboratories offer charcoal characterization using precise analysis and objective data such as :

1 - the presence of bark and pith: by simultaneously observing these two elements on a sample, we can deduce the size of the stem.

2 - Reaction wood (characteristic of small branches or leaning trunks). This criterion, combined with strong curvature, indicates a small branch.

3 - The presence of thylls: thylls form in the vessels of some hardwood species, during heartwood formation. The presence of thylls not only helps us to identify potential species, but also gives us an indication of where to sample.

4 - The presence of fungal hyphae: filaments may be found in the vessels. They correspond to the hyphae of fungi growing under aerobic conditions on the surface of a dead or dying tree only at high temperatures (summer season) and humidity levels of between 70 and 90%. The presence of hyphae gives us valuable information about the state of the wood before combustion.

5 - Degradation by insects or perforating worms: the presence of galleries in coals is evidence of an attack by insects or perforating glass. Charred organisms can be found in these galleries. This is proof that the wood was dead and worm-eaten before it was burnt. In some cases, the sapwood of a living tree can be attacked by such organisms.

6 - The presence of radial shrinkage cracks and vitrification: wood saturated with water will show a large number of shrinkage cracks. Vitrification is a complex phenomenon that occurs during combustion. Aspects of vitrification depend on the nature of the wood (species, size, moisture content) and combustion conditions (temperature and oxygenation conditions). We will distinguish 4 aspects of vitrification corresponding to 4 levels of carbonization:

• Matte appearance (level 0): coals are matte, gray or black in color. The anatomical structure is preserved.
• Shiny appearance (level 1): coals are dark to light gray in color and very shiny.
• Melted appearance (level 2): surfaces are very shiny and the anatomical structure is no longer discernible.
• Scoriaceous appearance (level 3): this is the last degree of vitrification, in which the coals are completely destructured.

7 - Grading: analysis of the curvature of the growth rings and the angle of the wood rays will identify the part of the tree from which the charcoal comes. Charcoal will be classified into 4 categories:

• Strongly curved rings: indicates very small-gauge wood
• Dark circles with moderate curvature
• Slightly curved rings: indicates the use of large-gauge wood (large branch or trunk).
• Rings with indeterminate curvatures

8 - Growth ring width and growth rate. Low ring widths indicate slow growth (unfavorable growing conditions or old trees). Wide ring widths, on the other hand, indicate strong growth (very favorable conditions or young trees). The rate of growth, i.e. the regularity of ring widths, indicates whether the tree has grown homogeneously or whether events have temporarily hindered growth (weather conditions, fungal attack, tree injuries, etc.).

9 - Traces of woodworking: grooves/scratches on the surface can attest to woodworking using tools.

For each archaeological site referenced, a systematic analysis of all charcoals will be carried out according to the criteria outlined above. Data will be compiled in the form of tables and graphs, and reported in an analysis report.

CIRAM, a specialist in carbon-14 dating and archaeomaterial analysis, offers a meticulous examination of your wood and charcoal. We are committed to delivering relevant and accurate results, and comply with current international standards.

While Carbon-14 dating is the ideal method for analyzing bones found in archaeological contexts, the method differs for calcined bones or bones found in arid regions or acidic environments.

How to date bones using Carbon 14? 

C14 dating is the most common and effective method for dating all organic matter. This technique, developed in the 1940s, relies on the radioactivity of carbon 14 (instability of carbon 14, which changes over time) contained in every organism. By measuring the concentration of carbon 14, it is possible to determine the time elapsed since the death of a living organism. But while Carbon-14, or radiocarbon, dating is relevant for conventional bones, the method differs for charred bones or bones found in arid environments. As the latter are damaged, alternative protocols will have to be used to obtain relevant dating.

What's the difference between bones and burnt bones? 

Conventional" bones contain 10-20% of their mass in collagen, whereas burnt bones contain almost none at all, or the collagen has been severely degraded. It's precisely this protein that we analyze when we carbon-14 date bones.

For bones that have been calcined or preserved in an arid and/or acidic environment, collagen is either of "poor quality" or too low in quantity. The C/N (carbon/nitrogen) ratio provides the collagen quality index. This atomic ratio must be between 2.9 and 3.6 for reliable collagen dating. If this is not the case, our scientists use an alternative protocol and date the mineral part of the bone, the bioapatite.

Treatment and extraction of charred bones

For radiocarbon dating, we always prefer white bones burnt at over 500° C, as the structural carbonates are more resistant to soil contamination.

To avoid the presence of impurities in the samples, it is imperative to use an acid-etch purification method. The reaction of carbonates with phosphoric acid releases CO2, which is then absorbed in a column filled with zeolitic material and graphitized with hydrogen and an iron catalyst. This method is recognized, as studies attest to the agreement between Carbon-14 dating on bioapatite and C14 dating on associated coals.

C14 dating method and calibration

In order to deliver accurate measurements, we systematically validate our analytical protocols through the analysis of international standards (OxII, IAEA-C7, IAEA-C5). They serve as calibration and enable us to assess our uncertainties at around 0.5 pMC, and between 0.1 and 0.2‰ for δ¹³C and δ¹5N.

Finally, our scientists separate the different carbon isotopes using particle gas pedal mass spectrometry (AMS) and measure the concentration of Carbon 14, 13 and 12.

Conventional age is expressed in years before 1950 (BP = before present). 1950 is the reference year for carbon-14 dating. The conventional age, or gross age, is then calibrated, using OxCal v4.4 software. The calibrated dates obtained are expressed within two sigmas, i.e. 95.4% of solutions are presented.

While preparation prior to measurement differs from that for "conventional" bones, CIRAM laboratories have the resources and know-how to date calcined, collagen-poor bones.

In this article, we discuss the use of stable carbon and nitrogen isotopes (δ13C and δ15N) in bone collagen. Thanks to these methods, it is possible to identify the environment from which individuals have drawn their resources, as well as their relative positions in the food web. Stable isotope analysis not only reveals a group's food choices, but also socio-cultural and economic distinctions. Our laboratory scientists propose individual and collective dietary trends based on information from each individual.

Determining diet using stable carbon and nitrogen isotopes

Carbon-14 dating is not the only technique used in archaeometry. Stable isotope analysis of carbon and nitrogen also provides a wealth of information. As far as plants are concerned, our scientists distinguish between two types of photosynthesis:

• In C3 for woody trees, rice, cotton or wheat which have a δ13C lower than -20 ‰ ;
• In C4, such as grass, corn or sugarcane, which have a δ13C of between -10 and -20%.

We also use the isotopic ratio of nitrogen 15 and 14 to determine the origin of proteins.

Thanks to stable carbon and nitrogen isotopes, it is possible to determine the diet of a person or animal. We know, for example, whether they were carnivores, herbivores or omnivores. We can also determine whether the diet was more terrestrial or marine in origin.

Determining the state of preservation of the bone material, an important step in exploiting the samples

By quantifying carbon and nitrogen concentrations and analyzing the C/N ratio, it is possible to assess the state of preservation of the organic bone material, collagen. If collagen is in a poor state of preservation, the samples cannot be processed. Only a C/N in the 2.9 to 3.6 range will reveal a state of preservation compatible with reliable carbon-14 dating and isotopic study.

Interpretation of results

The results of carbon and nitrogen stable isotope analysis provide valuable information such as :

• Origin of animal proteins (predominantly meat, milk/dairy products or fish);
• Importance of cereals and legumes in ancient times.

It is also possible to compare results with different groups of individuals to detect different habits and to understand archaeological issues. Our scientists interpret the results and work with you to resolve your hypotheses.

CIRAM laboratories use a vario ISOTOPE select elemental analyzer (EA) from ELEMENTAR, which measures carbon and nitrogen concentrations (atomic %). This is a high-temperature combustion unit, up to 1200°C. The weighing range is from 20 µg to 300 mg. Concentration range is up to 7 mg absolute for carbon and up to 10 mg absolute for nitrogen. External accuracy (1s) is less than 0.1% for carbon and nitrogen. The elemental analyzer is the IRMS gas injection system. ELEMENTAR's IRMS isoprime precisION is an isotope ratio mass spectrometer that measures the stable isotope ratios of carbon (13C/12C) and nitrogen (15N/14N) expressed in per thousand (‰). External precision (1s) is 0.1 ‰ for δ13C and 0.15 ‰ for δ15N.

CIRAM, leader in dation and analysis since 2005

Stable isotope analysis is a goldmine for understanding the dietary and social habits of a group of individuals, but to be reliable it must be carried out on a significant corpus of individuals, otherwise the results cannot be representative.

CIRAM, laboratory dating and analysis since 2005, accompanies all its results with a complete, documented report. Our teams of researchers are always ready to listen to your needs and to work closely with you in the field.

Carbon-14 is a radioactive isotope present in all living organisms. This isotope can be used to date a large number of organic materials found in archaeological contexts.

Specialists in AMS carbon-14 dating, our scientists perform laboratory analysis of materials such as wood, bone and charcoal, as well as peat and other organic sediments. Discover our peat analysis methods for precise dating of all your organic residues.

Valuable information thanks to C14 peat analysis

Peat bogs, which have been present in some areas for over 10,000 years, provide valuable information on environmental changes such as climate and anthropological changes.

For example, it is important to be able to define chronologically the start of turfigenesis on an archaeological site in order to carry out a paleo-environmental reconstruction.

Thanks to the distribution of the dates obtained and their comparison with geomorphological, paleoecological and archaeological data, it is possible to trace the evolution and changes in landscapes and societies.

While radiocarbon dating is the most suitable method for the chronological setting of peat bogs and other sediments, there are several methodological problems.

Different types of peat

We can analyze and date many types of peat and organic sediments. For accurate results, we take care to eliminate macro-rests.

For silty peats that do not contain macro-rests, we use organic sediment.

Fibrous peat (the most common in the samples we analyze) is a mixture of decomposing plant remains and silty peat. For this type of peat, we extract the fibrous part, which undergoes ABA (acid-base-acid) treatment to eliminate carbonates and humic and fulmic acids.

Sediment and peat analysis methods

Methods differ between silty peats and fibrous peats.

Silty peat is first sieved to 100 microns to remove micro-rests. Silty peats and the insoluble fraction of humic sediments are treated exclusively with acid to remove carbonates.

Fibrous peats are first treated with acid, then alkaline and finally washed with acid to remove carbonates and humic acids.

It is also necessary to sieve the soluble fraction of humic sediments to remove macro-rests. Once the fraction is clean, we use a hot acid treatment, repeated if effervescence persists, followed by an alkaline treatment. Our scientists recover only the alkaline solution by centrifugation or filtration. Finally, an acid treatment is applied until precipitation.

As a general rule, the acid-washed and sieved organic sediment fraction will give a more accurate dating.

Results and calibration

Our scientists systematically calibrate the analyses using international standards. There is a difference between the gross age and the calibrated dates, depending on the data and the estimated age of the peat. Gross age is expressed in BP years, i.e. before 1950. We always convert raw ages into calibrated dates, which are corrected by the calibration curve.

CIRAM laboratories can help you interpret your results

CIRAM's laboratories are committed to delivering results that are in line with the realities of the field, and always provide a detailed commentary to address your specific issues. We are also at your service to provide additional information and discuss the results in order to advance your research and meet your needs in relation to the archaeological context.

Follow-up of results, dialogue between professionals and proximity, CIRAM laboratories deliver serious expertise in collaboration with you.

Isotopes are found everywhere in the environment, in plants via sediments and water, and in animal tissues (and therefore in human tissues) through eating, drinking and breathing. The analysis of stable isotopes, such as those of carbon, nitrogen, strontium, etc., makes it possible to study the diets of an individual or group of individuals, and to determine where an individual grew up or lived for the last twenty to twenty-five years of his or her life.

Strontium is abundant in nature, found mainly in rocks and sediments. As sediments are eroded and dispersed in water and food resources, it is absorbed by the body and incorporated into bone tissue. The isotopic ratio of strontium varies from one geographical region to another. Consequently, the analysis of strontium isotope ratios in bones or teeth can be used to determine the geographical origin of an individual, or to measure the homogeneity of a group of individuals.

Bone and teeth are the most frequently analyzed tissues, as they are hard and can be preserved for a long time in archaeological contexts. Bone is made up of two components: an organic matrix composed mainly of collagen, and an inorganic mineral matrix composed mainly of calcium phosphates. Bone is a living tissue that constantly renews itself as we grow and age. However, this process is very slow, and dense cortical bone reflects approximately the last ten to fifteen years of an individual's life. Teeth are also composed of organic and mineral materials, but tooth enamel does not renew itself. Teeth are therefore very useful in determining the environment of an individual's early years. Moreover, by comparing the teeth and bones of the same individual, it is possible to determine whether he or she has migrated from one region to another since childhood. Teeth show where a person lived during childhood, and bones show where they lived in the years leading up to death.

The principle is to compare the 87Sr/86Sr ratio of bone and/or dental enamel with that of the environment (sediments) around the archaeological site and in neighbouring regions (with different geological substrates). This will enable us to discuss the geographical origin of the food ingested by the individuals.

As far as possible, the selection of material should respect the preservation of the archaeological remains, while satisfying the needs of the study. Bone fragments should preferably be sampled from the cortical bone. To be relevant, the study should be carried out on series of several subjects, and we will always try to select the same anatomical part. For dental tissue studies, depending on the inter- or intra-individual study issues, we will either carry out an analysis per tooth, or a multi-analysis per stratum. Analysis will be carried out using a multi-collector mass spectrometer , with or without laser ablation.

Animal tooth samples are cleaned with ethanol and placed on a glass slide to remove the outer enamel surface. For the specific case of herbivore teeth, we will choose analysis zones at the base, middle and top of each tooth, in order to assess the enamel formed at different times in the individual's life. The spectrometer is coupled to a laser system, equipped with an ablation cell (LA-ICP-MS). For laser ablation analysis, 500 µm long line scans are applied, with a circular spot size of 100 µm and a translation speed of 5 µm/s. We use several internal reference materials of bioapatite, as well as apatite and carbonate.

Strontium analysis is invaluable for studying the movement of populations. Thanks to our experienced scientists and state-of-the-art equipment, strontium analysis is a specialty of CIRAM laboratories.