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Atomic and Laser Physics
Credit: Jack Hobhouse

Prof Christopher Ramsey

Professor of Archaeological Science

Research theme

  • Accelerator physics
  • Climate physics
  • Instrumentation

Sub department

  • Atomic and Laser Physics
christopher.ramsey@physics.ox.ac.uk
Telephone: 01865285215
School of Archaeology
  • About
  • Publications

Analyzing Radiocarbon Reservoir Offsets Through Stable Nitrogen Isotopes and Bayesian Modeling: A Case Study Using Paired Human and Faunal Remains from the Cis-Baikal Region, Siberia

Radiocarbon Cambridge University Press (CUP) 56:2 (2014) 789-799

Authors:

Christopher Bronk Ramsey, Rick Schulting, Olga I Goriunova, Vladimir I Bazaliiskii, Andrzej W Weber

Abstract:

Dietary offsets in radiocarbon dates are becoming increasingly interesting to researchers, not only because of their impact on the reliability of chronologies but also because of the possibilities for extracting further dietary information from the 14C data itself. This is the case with the cemeteries of the Cis-Baikal region being studied as part of the international Baikal-Hokkaido Archaeology Project set up to examine hunter-gatherer cultural dynamics in eastern Asia. Fortunately, to control for a freshwater reservoir offset, we were able to obtain a number of paired terrestrial herbivore and human material for 14C dating. This article tests the correspondence between stable isotope evidence and the offsets seen in 14C values and the implications for the analysis of the 14C measurements as “chronometric dates.” This is an unusually well-documented example of freshwater reservoir offsets, providing an ideal case study to test different approaches to analyzing such offset information. Here, a purely Bayesian approach is compared with the more frequently applied linear regression analysis.
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Freshwater Reservoir Offsets Investigated Through Paired Human-Faunal14C Dating and Stable Carbon and Nitrogen Isotope Analysis at Lake Baikal, Siberia

Radiocarbon Cambridge University Press (CUP) 56:3 (2014) 991-1008

Authors:

Rick J Schulting, Christopher Bronk Ramsey, Vladimir I Bazaliiskii, Olga I Goriunova, Andrzej Weber

Abstract:

Thirty-three paired accelerator mass spectrometry (AMS) radiocarbon dates on human and terrestrial faunal remains from the same Neolithic and Early Bronze Age graves are used to develop a correction for the freshwater reservoir effect (FRE) at Lake Baikal, Siberia. Excluding two outliers, stable nitrogen isotope (δ15N) values show a positive correlation(r2= 0.672,p< 0.000) with offsets in14C yr between paired human and fauna determinations. The highest offset observed in our data set is 622 yr, which is close to the value of ∼700 yr suggested for endemic seals in the lake. For each per mil increase in δ15N, the offset increases by 77 ± 10 yr in the overall data set. However, there are indications that different regression models apply in each of two microregions of Cis-Baikal. In the first, sites on the southwest shore of the lake and along the Angara River show a strong positive correlation between δ15N values and offsets in14C yr (r2= 0.814,p< 0.000). In the other, the Little Sea, both δ13C and δ15N values make significant contributions to the model (adjustedr2= 0.878; δ13Cp< 0.001; δ15Np< 0.000). This can be related to the complex13C ecology of the lake, which displays one of the widest ranges of δ13C values known for any natural ecosystem. The results will be important in terms of refining the culture-history of the region, as well as exploring the dynamic interactions of hunter-gatherer communities both synchronically and diachronically.
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High-Precision Bayesian Modeling of Samples Susceptible to Inbuilt Age

Radiocarbon Cambridge University Press (CUP) 56:1 (2014) 83-94

Authors:

MW Dee, C Bronk Ramsey

Abstract:

Radiocarbon dates on samples susceptible to inbuilt age are common in the chronological record of many archaeological and environmental sites. Indeed, fragments of charcoal and wood are sometimes the only materials sufficiently well preserved for dating. However, where high-precision estimates arc required the extra uncertainty associated with such measurements often renders them unusable. This article tests three Bayesian modeling approaches that are designed to tackle this problem. The findings of our study suggest that successful corrections can be made for the inherent age offsets. The most effective and versatile approach was based on a version of outlier analysis. It is hoped that this method will become more widely employed and enable samples susceptible to inbuilt age to be included in high-precision chronologies.
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Radiocarbon Dating in Paleoseismology

Chapter in Encyclopedia of Earthquake Engineering, Springer Nature (2014) 1-11
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Second Radiocarbon Intercomparison Program for the Chauvetpont d'Arc Cave, Ardèche, France

Radiocarbon Cambridge University Press (CUP) 56:2 (2014) 833-850

Authors:

A Quiles, H Valladas, J-M Geneste, J Clottes, D Baffler, B Berthier, F Brock, C Bronk Ramsey, E Delqué-Količ, J-P Dumoulin, I Hajdas, K Hippe, GWL Hodgins, A Hogg, AJT Jull, E Kaltnecker, M De Martino, C Oberlin, F Petchey, P Steier, H-A Synal, J van der Plicht, EM Wild, A Zazzo

Abstract:

The Chauvet-Pont d'Arc Cave is one of the most important sites for the study of the earliest manifestations and development of prehistoric art at the beginning of the Upper Paleolithic. Different dating techniques have been performed thus far (AMS 14C, U/Th TIMS, 36Cl dating) to model the chronological framework of this decorated cave. The cave yielded several large charcoal fragments, which enabled the opportunity for obtaining multiple dates; thus, a First Radiocarbon Intercomparison Program (FIP) was initiated in 2004 using three charcoal pieces. The FIP demonstrated that those cross-dated samples belonged to a time period associated with the first human occupation. One of the statistical interests of an intercomparison program is to reduce the uncertainty on the sample age; thus, to further assess the accuracy of the chronological framework, the Second Intercomparison Program (SIP) involving 10 international 14C laboratories was carried out on two pieces of charcoal found inside two hearth structures of the Galerie des Mégacéros. Each laboratory used its own pretreatment and AMS facilities. In total, 21 and 22 measurements were performed, respectively, which yielded consistent results averaging ∼32 ka BP. Two strategies have currently been developed to identify statistical outliers and to deal with them; both lead to quasi-identical calibrated combined densities. Finally, the new results were compared with those of the FIP, leading to the important conclusion that five different samples from at least three different hearth structures give really tightened temporal densities, associated with one short human occupation in the Galerie des Mégacéros.
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