Making the most of radiocarbon dating: some statistical considerations

Antiquity ◽  
1994 ◽  
Vol 68 (259) ◽  
pp. 252-263 ◽  
Author(s):  
C. E. Buck ◽  
C. D. Litton ◽  
E. M. Scott

The revised radiocarbon calibration curve, published last year, extends back into the Pleistocene the radiocarbon determinations that can be converted to real calendar years. For determinations of any age, the right judgements and statistical considerations must be followed if the real information held in the determinations is to be found. Here is advice with some worked examples.

2020 ◽  
Author(s):  
Christopher Bronk Ramsey ◽  
Timothy Heaton ◽  
Maarten Blaauw ◽  
Paul Blackwell ◽  
Paula Reimer ◽  
...  

<p>Calibration is a key element of the radiocarbon dating methodology and the underlying Bayesian statistical approach taken, and algorithms used, are well established and used in calibration software and associated analysis packages.  These calibration methods are based on a calibration curve which provides a mean estimate for the radiocarbon isotope ratio (fractionation corrected) expected in samples, and the associated standard uncertainty, both as a function of time (or calendar age).  The measured samples also have their radiocarbon isotope ratio reported in the same form and so the calibration process involves comparison of the sample radiocarbon measurements with the calibration curve at different points on the calendar age scale.  This then yields a probability distribution function, with associated highest probability density ranges, for the sample calendar age.  We discuss here how improvements in the construction of the IntCal20 curve offer new opportunities, enabling users to obtain more from the calibration curve than previously possible and address some of the limitations of previous calibration approaches.</p><p>Previous approaches to calibration assumed that the values of the calibration curves at any time were normally distributed around their estimated mean. However, there are time periods where the distribution of these curves are not well represented by such a normal distribution. This is potentially significant even for calibrations of single samples. The new IntCal20 curve generates multiple possible calibration curves, providing us with the opportunity to identify and adapt to such non-normality.  A second limitation of previous approaches to calibration arises when multiple determinations are used within a broader chronological model. In such cases the usual assumption is that the calibrated uncertainties are independent.  This is certainly not the case if all the samples are the same age (which is currently addressed by combination before calibration) but also is potentially wrong if the samples are close enough in age for there to be correlated uncertainty in the calibration curve.  Again, using the collection of possible curves provided in the construction of IntCal20, rather than just the summary curve, we look at possible solutions to this challenge.  The implications for high-precision chronologies are also discussed.</p>


Radiocarbon ◽  
1995 ◽  
Vol 37 (1) ◽  
pp. 75-79 ◽  
Author(s):  
Irena Hajdas ◽  
Susan D. Ivy-Ochs ◽  
Georges Bonani

Radiocarbon dating of varved lake sediments shows that, during the Late Glacial (10–12 kyr bp), the offset between the 14C and the absolute time scales was ca. 1 kyr. Varve counting and accelerator mass spectrometry (AMS) dating were used to build absolute and 14C time scales of sediments from two lakes—Soppensee, Switzerland and Holzmaar, Germany. The resulting chronologies extend back to ca. 12.9 kyr cal bp (12.1 kyr bp) in the case of Soppensee and to ca. 13.8 kyr cal BP (12.6 kyr bp) in the Holzmaar record. They compare well with each other but differ significantly from the 14C-U/Th chronology of corals (Bard et al. 1993; Edwards et al. 1993).


Radiocarbon ◽  
1997 ◽  
Vol 39 (2) ◽  
pp. 193-204 ◽  
Author(s):  
F. B. Knox ◽  
B. G. McFadgen

We Fourier transformed and filtered calibration curve data to compensate for the averaging effect of radiocarbon-dating sets of adjacent tree rings. A Wiener Filter was also applied to minimize the effects of the counting errors of the dates on the resulting calibration curve and to produce a least-squares curve through the data. The method is illustrated using a short 14C-dated tree-ring sequence from New Zealand to produce a calibration curve at yearly intervals for New Zealand matai (Prumnopitys taxifolia). The resulting curve has a nominal standard error of 10 ± 3 yr, which is ca. half the average standard error of the original raw data.


Radiocarbon ◽  
2004 ◽  
Vol 46 (3) ◽  
pp. 1123-1125 ◽  
Author(s):  
F G McCormac ◽  
A Bayliss ◽  
M G L Baillie ◽  
D M Brown

Radiocarbon dating has been rarely used for chronological problems relating to the Anglo-Saxon period. The “flatness” of the calibration curve and the resultant wide range in calendrical dates provide little advantage over traditional archaeological dating in this period. Recent advances in Bayesian methodology have, however, created the possibility of refining and checking the established chronologies, based on typology of artifacts, against 14C dates. The calibration process, within such a confined age range, however, relies heavily on the structural accuracy of the calibration curve. We have therefore re-measured, at decadal intervals, a section of the Irish oak chronology for the period AD 495–725. These measurements have been included in IntCal04.


Radiocarbon ◽  
2019 ◽  
Vol 61 (4) ◽  
pp. 939-952
Author(s):  
R S Kidd

ABSTRACTTombs and cairns present a dating challenge when the human remains are unstratified, incomplete and dispersed. By considering the distribution of time intervals between deaths as a possible a priori condition of multiple burials of select groups, a Bayesian model is suggested that may constrain the uncertainty date range of the group. The method may also address the wide uncertainties seen in radiocarbon calibration on a calibration curve plateau. The mathematical justification for the choice of Log Normal intervals, between death events, is first presented, followed by worked examples that compare the treatment of groups of 22 dates using Phase then Sequence with interval gaps. Finally, scenarios of potential Select Groups are examined, to demonstrate the efficacy of this alternative heuristic model to current model treatments.


Radiocarbon ◽  
2008 ◽  
Vol 50 (1) ◽  
pp. 11-17 ◽  
Author(s):  
F G McCormac ◽  
A Bayliss ◽  
D M Brown ◽  
P J Reimer ◽  
M M Thompson

Radiocarbon dating has been used infrequently as a chronological tool for research in Anglo-Saxon archaeology. Primarily, this is because the uncertainty of calibrated dates provides little advantage over traditional archaeological dating in this period. Recent advances in Bayesian methodology in conjunction with high-precision 14C dating have, however, created the possibility of both testing and refining the established Anglo-Saxon chronologies based on typology of artifacts. The calibration process within such a confined age range, however, relies heavily on the structural accuracy of the calibration curve. We have previously reported decadal measurements on a section of the Irish oak chronology for the period AD 495–725 (McCormac et al. 2004). In this paper, we present decadal measurements for the periods AD 395–485 and AD 735–805, which extends the original calibration set.


2017 ◽  
Vol 21 (3) ◽  
pp. 411-430 ◽  
Author(s):  
Piotr Jacobsson ◽  
Alex G.C. Hale ◽  
Gordon Cook ◽  
Derek Hamilton

There are at least four wooden intertidal platforms, also known as marine crannogs, in the Firth of Clyde, on the west coast of Scotland. The interpretation of these sites partly depends on their dating and, if coeval, they could point to the presence of a native maritime hub. Furthermore, the spatial coincidence with the terminus of the Antonine Wall has led to speculation about the role they may have played in Roman-native interaction during the occupation of southern Scotland in the early first millennium calad. Hence, a better absolute chronology is essential to evaluate whether the marine crannogs were contemporary with one another and whether they related to any known historic events. This article presents results of a wiggle-match dating project aimed at resolving these uncertainties at two of the sites in question, Dumbuck and Erskine Bridge crannogs. The results show that the construction of these sites pre-date direct Roman influence in Scotland. Furthermore, the results indicate that the two sites were built at least 300 years apart, forcing us to consider the possibility that they may have functioned in very different historical contexts. Other findings include technical observations on the fine shape of the radiocarbon calibration curve near the turn of the first millenniabc/adand potential evidence for persistent contamination in decayed and exposed sections of waterlogged alder.


Author(s):  
Irina V. Bogdashina

The article reveals the measures undertaken by the Soviet state during the “thaw” in the fi eld of reproductive behaviour, the protection of motherhood and childhood. Compilations, manuals and magazines intended for women were the most important regulators of behaviour, determining acceptable norms and rules. Materials from sources of personal origin and oral history make it possible to clearly demonstrate the real feelings of women. The study of women’s everyday and daily life in the aspect related to pregnancy planning, bearing and raising children will allow us to compare the real situation and the course of implementation of tasks in the fi eld of maternal and child health. The demographic surge in the conditions of the economy reviving after the war, the lack of preschool institutions, as well as the low material wealth of most families, forced women to adapt to the situation. In the conditions of combining the roles of mother, wife and female worker, women entrusted themselves with almost overwork, which affected the health and well-being of the family. The procedure for legalising abortion gave women not only the right to decide the issue of motherhood themselves, but also made open the already necessary, but harmful to health, habitual way of birth control. Maternal care in diffi cult material and housing conditions became the concern of women and the older generation, who helped young women to combine the role of a working mother, which the country’s leadership confi dently assigned to women.


Radiocarbon ◽  
2016 ◽  
Vol 59 (5) ◽  
pp. 1623-1627 ◽  
Author(s):  
Ron W Reimer ◽  
Paula J Reimer

AbstractA regional offset (ΔR) from the marine radiocarbon calibration curve is widely used in calibration software (e.g. CALIB, OxCal) but often is not calculated correctly. While relatively straightforward for known-age samples, such as mollusks from museum collections or annually banded corals, it is more difficult to calculate ΔR and the uncertainty in ΔR for 14C dates on paired marine and terrestrial samples. Previous researchers have often utilized classical intercept methods that do not account for the full calibrated probability distribution function (pdf). Recently, Soulet (2015) provided R code for calculating reservoir ages using the pdfs, but did not address ΔR and the uncertainty in ΔR. We have developed an online application for performing these calculations for known-age, paired marine and terrestrial 14C dates and U-Th dated corals. This article briefly discusses methods that have been used for calculating ΔR and the uncertainty and describes the online program deltar, which is available free of charge.


Cephalalgia ◽  
2017 ◽  
Vol 38 (7) ◽  
pp. 1245-1256 ◽  
Author(s):  
Eleonora Vecchio ◽  
Eleonora Gentile ◽  
Giovanni Franco ◽  
Katia Ricci ◽  
Marina de Tommaso

Background Transcutaneous external supraorbital nerve stimulation has emerged as a treatment option for primary headache disorders, though its action mechanism is still unclear. Study aim In this randomized, sham-controlled pilot study we aimed to test the effects of a single external transcutaneous nerve stimulation session on pain perception and cortical responses induced by painful laser stimuli delivered to the right forehead and the right hand in a cohort of migraine without aura patients and healthy controls. Methods Seventeen migraine without aura patients and 21 age- and sex-matched controls were selected and randomly assigned to a real or sham external transcutaneous nerve stimulation single stimulation session. The external transcutaneous nerve stimulation was delivered with a self-adhesive electrode placed on the forehead and generating a 60 Hz pulse at 16 mA intensity for 20 minutes. For sham stimulation, we used 2 mA intensity. Laser evoked responses were recorded from 21 scalp electrodes in basal condition (T0), during external transcutaneous nerve stimulation and sham stimulation (T1), and immediately after these (T2). The laser evoked responses were analyzed by LORETA software. Results The real external transcutaneous nerve stimulation reduced the trigeminal N2P2 amplitude in migraine and control groups significantly in respect to placebo. The real stimulation was associated with lower activity in the anterior cingulate cortex under trigeminal laser stimuli. The pattern of LEP-reduced habituation was reverted by real and sham transcutaneous stimulation in migraine patients. Conclusions The present results could suggest that the external transcutaneous nerve stimulation may interfere with the threshold and the extent of trigeminal system activation, with a mechanism of potential utility in the resolution and prevention of migraine attacks.


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