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Research and teaching centre
environmental geosciences
Research and teaching centre
environmental geosciences

Applications of the Radiocarbon Unit

Radiocarbon calibration and the global carbon cycle

In its original form, radiocarbon dating is not accurate because the atmospheric 14C does not remain constant over time. This content has varied due to changes in the rate of production by cosmic rays, as well as rearrangements of the biogeochemical carbon cycle. To calculate the age of an ancient object from the measurement of 14C content of the product, it is necessary to know the 14C of the atmosphere contemporary with the time of the object's appearance. The initial radiocarbon age is therefore corrected (calibrated) by comparing the 14C measured with those of other samples for which accurate and precise ages have been measured by independent methods such as the counting of annual tree rings or the dating of carbonates by the uranium-thorium (U-Th) method. For thirty years, radiocarbon calibration curves have been prepared by the international IntCal working group, in which CEREGE has participated since its foundation.

The latest iteration of the IntCal20 calibration (Reimer et al. 2020, Heaton et al. 2020, 2021, 2022, 2023, Bard et al. 2020) includes the results obtained with the AixMICADAS spectrometer (Bard et al. 2015) measured in the framework of the EQUIPEX ASTER-CEREGE and ANR CARBOTRYDH projects (Capano et al. 2018, 2020a). The quality of the dating performed by AixMICADAS has been demonstrated in an international intercomparison on subfossil tree series (Wacker et al. 2020).

In parallel with the improved accuracy of the radiocarbon chronometer, the recording of natural variations in 14C is essential for our understanding of climate processes, variations in solar activity, geodynamic intensity and the biogeochemical carbon cycle. The development of a 14C over 50,000 years is used to study and simulate Earth processes and to improve the computer models used for current climate change projections (Heaton et al. 2021). Indeed, the climate simulations compiled by the Intergovernmental Panel on Climate Change (IPCC) are based on the 14C as an indicator of solar activity and as a tracer of the global carbon cycle - as well as of course as a timer for most of the paleoclimate series of the last 50,000 years. Our records from the French Alps are compared with similar results from the southern hemisphere (New Zealand and Tasmania), allowing us to study inter-hemispheric exchanges and the evolution of CO2 to the atmosphere (Capano et al. 2020). The 14C also tells us about the occurrence of extreme solar flares in the past, with amplitudes much larger than those observed by astronomers.

The study of 14C in the marine archives allows us to complete the calibration of the radiocarbon and to quantify the variations of the carbon cycle by comparing atmospheric and oceanic series. By performing dating 14C corals and planktonic foraminifera, it is possible to reconstruct the age variability 14C of the surface marine reservoir (MRA) which is a tracer of air-sea gas exchange and carbon mixing in the ocean (Skinner & Bard 2022, Skinner et al. 2023). In addition, the ages 14C measured on benthic foraminifera allow the assessment of deep ocean circulation (Skinner & Bard 2022, Skinner et al. 2023). Our international collaborative research project (ANR MARCARA with the Alfred Wegener Institute in Bremerhaven) is focused on observing and numerically modelling the MRA for key sites in the major oceans. We measure the ages 14C of micro-samples thanks to the AixMICADAS multipurpose ion source, allowing in particular the dating of individual foraminifera (Fagault et al. 2019). This leads us to better quantify the MRA by avoiding, or correcting, certain biases (Bard & Heaton 2021). Our project focuses on the last deglaciation and abrupt climate changes such as the Heinrich and Dansgaard-Oeschger events, whose role on the carbon cycle is still poorly understood.

Regional air pollution

Radiocarbon is the best tracer to distinguish and quantify products from fossil fuel use from other carbon sources such as biomass burning and natural biogenic emissions. The direct measurement of 14C on fine particles of atmospheric aerosol filters is performed using the elemental analyser coupled to the CO2 AixMICADAS gas analysis, which allows the analysis of samples of a few micrograms of carbon (Bard et al. 2015, Tuna et al. 2018). This technique has been applied to aerosols from the Chamonix valley (Bonvalot et al. 2016) and from Fos-sur-Mer (Bonvalot et al. 2019). Our studies have demonstrated the interest of combining the 14C with other source diagnostic molecular tracers to quantify the strong impact of biomass burning, especially in winter, and to dissociate it from other contributions such as car traffic or biogenic emissions. We are also studying the flows of particles and pyrogenic compounds towards the Mediterranean (ANR FIRETRAC project). The determination of the origins of the compounds separated by liquid chromatography is carried out by measuring the 14C micro-samples (Nouara et al. 2019).

Dating in archaeology and prehistory

Wood cellulose dating, optimized for our work on radiocarbon calibration, allows the precise dating of archaeological sites using the wiggle-matching technique combining 14C with dendrochronology (ARKAIA Chrono-Ignis project). Our first applications concern Bronze Age sites in Italy (Capano et al. 2020b) and the Sassanid period in Iran (Djamali et al. 2022).

For the rarest and most valuable artefacts in archaeology, such as human remains, tools and bone carvings, the destruction of the samples required for conventional accelerator mass spectrometry dating would cause irreparable damage. The CO2 AixMICADAS gas analysis overcomes this constraint due to the very small sample size (Tuna et al. 2018). The development of the dating of purified collagen from human bones was carried out in collaboration with the Max Planck Institute for Evolutionary Anthropology in Leipzig and the Chair of Paleoanthropology at the Collège de France. The first step was to establish an optimal method for the synthesis of CO2 from collagen using an elemental analyser and a zeolite trap coupled to the AixMICADAS ion source (Fewlass et al. 2018, 2019a). This method has been used to date purified collagen samples from fragments of human remains from famous sites such as the Dolni Vestonice triple human burial site in the Czech Republic (Fewlass et al. 2019b), the Pradis cave in Italy (Lugli et al. 2022) and the Bacho Kiro cave in Bulgaria (Fewlass et al. 2020) for which the same human bones dated by 14C have been the subject of genetic and proteomic analyses (Hublin et al. 2020).

For samples heavily contaminated with exogenous carbon, a more efficient method is to purify and date one of the main amino acids in collagen. The separation of hydroxyproline is currently being developed in the organic geochemistry unit.

Radiocarbon unit references


Heaton TJ, Butzin M, Bard E, Bronk Ramsey C, Köhler P, Hughen KA, Reimer PJ. Marine Radiocarbon calibration in polar regions: A simple approximate approach using Marine20. Radiocarbon, (2023).

Skinner L, Primeau F, Jeltsch-Thömmes A, Joos F, Köhler P, Bard E. Rejuvenating the ocean: ventilation seesaws, CO2 release, and radiocarbon budget closure across the last deglaciation. Communications Earth & Environment (2023).


Heaton TJ, Bard E, Bronk Ramsey C, Butzin M, Hatté C, Hughen KA, Köhler P, and Reimer PJ. A response to community questions on the Marine20 radiocarbon age calibration curve: Marine reservoir ages and the calibration of 14C samples from the oceans. RadiocarbonDOI:10.1017/RDC.2022.66 (2022).

Lugli F, Nava A, Sorrentino R, Vazzana A, Bortolini E, Oxilia G, Silvestrini S, Nannini N, Bondioli L, Fewlass H, Talamo S, Bard E, Mancini L, Müller W, Romandini M, Benazzi S. Tracing the mobility of a Late Epigravettian (~ 13 ka) male infant from Grotte di Pradis (Northeastern Italian Prealps) at high-temporal resolution Scientific Reports 12, 8104, 1-13, +6 p. suppl. DOI: 10.1038/s41598-022-12193-6 (2022)

Schimmelpfennig I, Schaefer JM, Lamp J, Godard V, Schwartz R, Bard E, Tuna T, Akçar N, Schlüchter C, Zimmerman S, and ASTER Team: Glacier response to Holocene warmth inferred from in situ 10Be and 14C bedrock analyses in Steingletscher's forefield (central Swiss Alps), Climate of the Past 18, 23-44, DOI: 10.5194/cp-18-23-2022 (2022).

Skinner LC, Bard E. Radiocarbon as a dating tool and tracer in palaeoceanography. Reviews of Geophysics 60, 1, 1-64, e2020RG000720, DOI: 10.1029/2020RG000720 (2022).

Djamali M, Capano M, Askari A, Faucherre N, Guibal F, Northedge A, Rashidian E, Tuna T, Bard E, An absolute radiocarbon chronology for the World Heritage site of Sarvestan (SW Iran); a late Sasanian heritage in early Islamic era. Archaeometry 64, 545-559, DOI: 10.1111/arcm.12716 (2022).


Bard E, Heaton TJ. On the tuning of plateaus in atmospheric and oceanic 14C records to derive calendar chronologies of deep-sea cores and records of 14C marine reservoir age changes. Climate of the Past 17, 1701-1725, DOI: 10.5194/cp-17-1701-2021 (2021).

Heaton TJ, Bard E, Bronk Ramsey C, Butzin M, Köhler P, Muscheler R, Reimer PJ, Wacker L. Radiocarbon: a key tracer for studying the Earth's dynamo, climate system, carbon cycle and Sun. Science 374, 707, 1-11, eabd7096, DOI: 10.1126/science.abd7096 (2021).

Young NE, Lesnek AJ, Cuzzone JK, Briner JP, Badgeley JA, Balter-Kennedy A, Graham BL, Cluett A, Lamp JL, Schwartz R, Tuna T, Bard E, Caffee MW, Zimmerman SRH, Schaefer JM. Cosmogenic isotope measurements from recently deglaciated bedrock as a new tool to decipher changes in Greenland Ice Sheet size. Climate of the Past 17, 419-450, DOI: 10.5194/cp-17-419-2021 (2021).


Bard E, Heaton TJ, Talamo S, Kromer B, Reimer RW, Reimer PJ. Extended dilation of the radiocarbon time scale between 40,000 and 48,000 years BP and the overlap between Neanderthals and Homo sapiens. Proceedings of the National Academy of Sciences 117 (35), 21005-21007, +2 p. suppl, DOI: 10.1073/pnas.2012307117 (2020).

Capano C, Martinelli N, Baioni M, Tuna T, Bernabei M, Bard E. Is the dating of short tree-ring series still a challenge? New evidence from the pile dwelling of Lucone di Polpenazze (northern Italy). Journal of Archaeological Sciences 121, 1-12, 105190, DOI:10.1016/j.jas.2020.105190 (2020b).

Wacker L, Scott EM, Bayliss A, Brown D, Bard E, Bollhalder S, Friedrich M, Capano M, Cherkinsky A, Chivall D, Culleton BJ, Dee MW, Friedrich R, Hodgins GWL, Hogg A, Kennett DJ, Knowles TDJ, Kuitems M, Lange TE, Miyake F, Nadeau M-J, Nakamura T, Naysmith JP, Olsen J, Omori T, Petchey F, Philippsen B, Ramsey CB, Prasad GVR, Seiler M, Southon J, Staff R, Tuna T. Findings from an in-depth annual tree ring radiocarbon intercomparison. Radiocarbon 62 (4), 873-882, DOI: 10.1017/RDC.2020.49 (2020).

Heaton TJ, Köhler P, Butzin M, Bard E, Reimer RW, Austin WEN, Bronk Ramsey C, Grootes PM, Hughen KA, Kromer B, Reimer PJ, Adkins JF, Burke A, Cook MS, Olsen J, Skinner LC. Marine20 - the marine radiocarbon age calibration curve (0-55,000 cal BP). Radiocarbon 62 (4), 821-863, DOI: 10.1017/RDC.2020.68 (2020).

Reimer PJ, Austin WEN, Bard E, Bayliss A, Blackwell PG, Bronk Ramsey C, Butzin M, Cheng H, Edwards RL, Friedrich M, Grootes PM, Guilderson TP, Hajdas I, Heaton TJ, Hogg AG, Hughen KA, Kromer B, Manning SW, Muscheler R, Palmer JG, Pearson C, Plicht Jvd, Reimer RW, Richards DA, Scott EM, Southon JR, Turney CSM, Wacker L, Adophi F, Büntgen U, Capano M, Fahrni S, Fogtmann-Schulz A, Friedrich R, Köhler P, Kudsk S, Miyake F, Olsen J, Reinig F, Sakamoto M, Sookdeo A, Talamo S. The IntCal20 Northern Hemisphere radiocarbon calibration curve (0-55 kcal BP). Radiocarbon 62 (4), 725-757, DOI: 10.1017/RDC.2020.41 (2020).

Hublin JJ, Sirakov N, Aldeias V, Bailey S, Bard E, Delvigne V, Endarova E, Fagault Y, Fewlass H, Hajdinjak M, Kromer B, Krumov I, Marreiros J, Martisius N, Paskulin L Sinet-Mathiot V, Meyer M, Pääbo S, Popov V, Rezek Z, Sirakova S, Skinner MM, Smith GM, Spasov R, Talamo S, Tuna T, Wacker L, Welker F, Wilcke A, Zahariev N, McPherron SP, Tsanova T. Initial Upper Palaeolithic Homo sapiens from Bacho Kiro Cave, Bulgaria. Nature 581, 299-302, + 13 supplementary pages, DOI: 10.1038/s41586-020-2259-z (2020).

Fewlass H, Talamo S, Wacker L, Kromer B, Tuna T, Fagault Y, Bard E, McPherron SP, Aldeias V, Maria R, Martisius NL, Paskulin L, Rezek Z, Sinet-Mathiot V, Sirakova S, Smith GM, Spasov R, Welker F, Sirakov N, Tsanova T, Hublin JJ A 14C chronology for Middle-to-Upper Palaeolithic transition at Bacho Kiro Cave, Bulgaria. Nature Ecology & Evolution 4, 794-801, + 4 supplementary pages, DOI: 10.1038/s41559-020-1136-3 (2020).

Milesi VP, Debure M, Marty NCM, Capano M, Jézéquel D, Steefel C, Rouchon V, Albéric P, Bard E, Sarazin G, Guyot F, Virgone A, Gaucher EC, Ader M. Early Diagenesis of Lacustrine Carbonates in Volcanic Settings: The Role of Magmatic CO2 (Lake Dziani Dzaha, Mayotte, Indian Ocean). American Chemical Society Earth and Space Chemistry 4 (3), 363-378, DOI: 10.1021/acsearthspacechem.9b00279 (2020).

Capano M, Miramont C, Shindo L, Guibal F, Marschal C, Kromer B, Tuna T, Bard E. Onset of the Younger Dryas recorded with 14C at annual resolution in French subfossil trees. Radiocarbon 62 (4), 901-918, DOI: 10.1017/RDC.2019.116 (2020a).


Fewlass H, Talamo S, Kromer B, Bard E, Tuna T, Fagault Y, Sponheimer M, Ryder C, Hublin JJ, Perri A, Sázelová S, Svoboda J. Direct radiocarbon dates of mid Upper Palaeolithic human remains from Dolní Věstonice II and Pavlov I, Czech Republic. Journal of Archaeological Science 27, 102000, 1-8, DOI: 10.1016/j.jasrep.2019.102000 (2019b).

Lamp JL, Young NE, Koffman T, Schimmelpfennig I, Tuna T, Bard E, Schaefer JM. Update on the cosmogenic in situ 14C laboratory at the Lamont-Doherty Earth Observatory. Nuclear Instruments and Methods in Physics Research B 456, 157-162, DOI: 10.1016/j.nimb.2019.05.064 (2019).

Bonvalot L, Tuna T, Fagault Y, Sylvestre A, Mesbah B, Wortham H, Jaffrezo JL, Marchand N, Bard E. Source apportionment of carbonaceous aerosols in the vicinity of a Mediterranean industrial harbor: A coupled approach based on radiocarbon and molecular tracers. Atmospheric Environment 212, 250-261, DOI: 10.1016/j.atmosenv.2019.04.008 (2019).

Fewlass H, Tuna T, Fagault Y, Hublin JJ, Kromer B, Bard E, Talamo S. Pretreatment and gaseous radiocarbon dating of 40-100 mg archaeological bone, Scientific Reports 9, 5342, 1-11, + 4 p. suppl, DOI: 10.1038/s41598-019-41557-8 (2019a).

Nouara A, Panagiotopoulos C, Balesdent J, Violakia K, Bard E, Fagault Y, Repeta DJ, Sempéré R. Liquid chromatographic isolation of individual carbohydrates from environmental matrices for stable carbon analysis and radiocarbon dating. Analytica Chimica Acta 1067, 137-146, DOI: 10.1016/j.aca.2019.03.028 (2019).

Fagault Y, Tuna T, Rostek F, Bard E. Radiocarbon dating small carbonate samples with the gas ion source of AixMICADAS. Nuclear Instruments and Methods in Physics Research B 455, 276-283, DOI: 10.1016/j.nimb.2018.11.018 (2019).


Tuna T, Fagault Y, Bonvalot L, Capano C, Bard E. Development of small CO2 gas measurements with AixMICADAS. Nuclear Instruments and Methods in Physics Research B 437, 93-97, DOI: 10.1016/j.nimb.2018.09.012 (2018).

Capano M, Miramont C, Guibal F, Kromer B, Tuna T, Fagault Y, Bard E. Wood 14C dating with AixMICADAS: methods and application to tree-ring sequences from the Younger Dryas event in the southern French Alps. Radiocarbon 60, 51-74, DOI: 10.1017/RDC.2017.83 (2018).

Fewlass H, Talamo S, Tuna T, Fagault Y, Kromer B, Hoffman H, Pangrazzi C, Hublin JJ, Bard E. Size matters: radiocarbon dates on microgram collagen samples back to the Palaeolithic with AixMICADAS and its gas ion source Radiocarbon60 (2), 425-439, DOI: 10.1017/RDC.2017.98 (2018).


Sepulcre S, Durand N, Bard E. Large 14C age offsets between the fine fraction and coexisting planktonic foraminifera in shallow Caribbean sediments. Quaternary Geochronology 38, 61-74, DOI: 10.1016/j.quageo.2016.12.002 (2017).


Bonvalot L, Tuna T, Fagault Y, Jaffrezo JL, Jacob V, Chevrier F, Bard E. Estimating contributions from biomass burning, fossil fuel combustion, and biogenic carbon to carbonaceous aerosols in the Valley of Chamonix: a dual approach based on radiocarbon and levoglucosan Atmospheric Chemistry and Physics 16, 1-20, DOI: 10.5194/acp-16-13753-2016 (2016).


Bard E, Tuna T, Fagault Y, Bonvalot L, Wacker L, Fahrni S, Synal H-A. AixMICADAS, the accelerator mass spectrometer dedicated to 14C recently installed in Aix-en-Provence, France. Nuclear Instruments and Methods in Physics Research B 361, 80-86, DOI: 10.1016/j.nimb.2015.01.075 (2015).