Radiocarbon was measured in dissolved inorganic carbon (DIC) and living organisms collected off the west coast of Baja California in October 1980. Samples from three locations were examined. Δ14C of DIC at the southernmost station was higher than those further north, which reflects reduced upwelling in the southern region. Crabs and anchovies had Δ14C values significantly lower than surface DIC Δ14C, indicating the incorporation of ‘older', sediment-derived carbon sources from their diets. Comparisons are made between our DIC Δ14C measurements and those obtained during other cruises and at a coastal site, from 1959 through 1987. Two distinct time histories of DIC Δ14C are apparent for the post-bomb period: 1) a lower Δ14C curve for sites close to the coast influenced by enhanced coastal upwelling; and 2) a higher Δ14C curve for sites further offshore within the California Current.

The radiologic impact of 14C produced by the nuclear fuel cycle is assessed at both global and local levels. In the former context, it is predicted here that the specific activity of atmospheric CO2 in the year 2050 will be ca 7.6 pCig-1 C. Although this is similar to the present level, the subsequent collective dose commitment could be highly significant.

The enhancement of 14C concentrations around the nuclear fuel-reprocessing plant at Sellafield (Windscale) in Cumbria, U K has been monitored over recent years. For example, maximum levels of 27.2 pCig-1C (∼350% above natural) during 1984 were observed < 1 km from the plant, with enhanced activities detectable to at least 29km. Nevertheless, it is clear that the radiologic significance to the local population is low. The spatial distribution of the excess 14C allows atmospheric dispersion models to be tested in the context of continuous releases and the results thus far show that the Gaussian plume model performs successfully.

Measurements of the stable isotope ratio 13C/12C, relative to PDB, were made for fractionation correction purposes on all oak samples used in the Irish oak 14C calibration curve. Stable isotope data have not been published previously. We have collated the stable isotope data from the calibration work, carried out some further measurements to investigate anomalies in the original results, and generated tables of data that include site and tree information pertaining to both stable isotopes and source material for 14C calibration measurements. The data suggest that land-grown trees tend to be isotopically lighter than bog-grown wood, and that the Irish trees used in the calibration exercise tend to be isotopically heavier than those from Scotland and England. Preliminary analysis of the data is given.

The following list contains samples of geologic interest that were processed from June 1980 through March 1983 at the Illinois State Geological Survey (ISGS) Radiocarbon Dating Laboratory. The benzene liquid scintillation technique was used following laboratory procedures previously reported by Coleman (1973, 1974).

In this paper, we describe improvements to the in situ cosmogenic radiocarbon extraction system at SUERC made since 2004, highlighting the factors that potentially control the reduction of analytical variability. We also present new results on system blanks and of measurements of in situ14C in shielded quartz and a surface quartz sample used at the University of Arizona as an in situ14C standard (PP-4). The SUERC in situ14C extraction system was built in 2001 and is based on a combustion technique following the design of the extraction system at the University of Arizona. Our preliminary results suggest that the continuous running of the extraction system and the monitoring of gas collecting time and of the temperature of the cryogenic traps used in the gas cleaning steps are key to maintaining low and stable system blanks. Our latest average system blank is 2.02 ± 0.23 x 10514C atoms. This is consistent with those recently published by the University of Arizona and ETH in situ14C labs. Measurements of in situ14C concentrations in sample PP-4 yield an average of 3.82 ± 0.23 x 105 atoms g–1 quartz, again consistent with published values.

A new vacuum system for the preparation of graphite samples for radiocarbon (14C) measurement using an accelerator mass spectrometer (AMS) was constructed at the Dendrochronological Laboratory in AGH-UST Kraków. The central part of the system is a manual vacuum line for the production of graphite from carbon dioxide for subsequent AMS measurements. The graphitization system can handle up to five samples simultaneously, and the process lasts for approximately 1 hour. The graphitization line was built to support the preparation of wood samples for a project dedicated to dating a subfossil tree from the Younger Dryas period. For this purpose, the chemical preparation procedure for wood samples was optimized to obtain more reliable results. This includes the extraction of α-cellulose to increase the precision of the age determination. The performance of the system was tested with NIST OxII, IAEA standards (IAEA C3, C5, C6, and C8), and background samples. The results of the 13 samples of subfossil wood were tested and are presented. The methodology gives good reproducibility of results obtained for the samples prepared using this system.

The Florence Radiocarbon Dating Laboratory was built in 1970 under the direction of Consiglio Nazionale delle Ricerche at the Istituto di Antropologia, Università di Firenze.

We studied the chronology and periodization of the Pit-Grave (Yamnaya) culture at the Volga and Ural interfluve. Establishing the chronology of the Pit-Grave culture by archaeological methods is difficult due to the lack of artifacts in the burials. Therefore, we excavated 3 kurgan groups in the Orenburg region of Russia during the last decade. Eighteen kurgans of the Pit-Grave culture were studied using archaeological and paleopedological methods and radiocarbon dating. The funeral complexes studied were divided into 3 stages. A variety of carbon-containing materials from the same complexes were dated by different laboratories to increase the accuracy of the obtained dates. In addition, from the excavations of the last years some monuments of the Repino stage, the earliest period of the Pit-Grave culture, were dated using ceramics. Together with archaeological and paleopedological data, 14C dating helped to clarify and, in general, to confirm the 3-stage periodization of the Pit-Grave culture in the Volga-Ural interfluve: the early (Repino) stage, 4000–3300 BC; the advanced (classical) stage, 3300–2600 BC, which is divided into substages A and B at 3300–2900 and 2900–2600 BC, respectively; and the late (Poltavkinsky) stage, 2600–2300 BC.

The determination of the age of tropical trees and palms is of significant importance for ecological studies and designing sustainable forest management plans. Radiocarbon is a powerful tool that can potentially help the determination of ages and growth rates of these plants. However, the application of 14C analyses has one important problem for trees without annual rings and palms: the calibration of 14C measurements with common programs such as CALIBomb or OxCal gives erroneous determinations for wood formed between AD 1954 and 1964. This problem is illustrated here using samples from a tropical tree (Otoba gracilipes) and a tropical palm (Oenocarpus bataua). This study shows how the use of two adjacent samples can help to unambiguously determine the real age of the samples and their mean growth rates. For comparison, long-term growth measurements for both species were used and it was determined that 14C analyses provide accurate determination of growth rates for tropical trees and palms. Furthermore, the application of 14C analyses in palms allows the determination of the rosette stage, rarely quantified in forest inventories and life-history studies.

California's San Miguel Island contains over 600 archaeological sites, some occupied as early as 12,000 yr ago and most located along the island's north coast. Archaeologists have long believed the south coast to have been marginal or largely uninhabited. Burial of some landforms by sand dunes deposited after historical overgrazing, the lack of systematic survey, and a dearth of radiocarbon dating have also contributed to an underestimation of the intensity of human land use along the south coast of San Miguel Island. Our recent reconnaissance and dating of shell middens on the island's south coast indicate more intensive occupation than previously thought, with numerous south coast sites spanning at least the past 9000 yr, and demonstrate the utility of combining systematic archaeological reconnaissance and radiometrics in reconstructions of human settlement and historical ecology in coastal environments.

The dating equipment and operating conditions remain essentially as previously described. All samples in this list have been counted at a filling pressure equivalent to 152 cm Hg at 20°C. The proportional counter has recently been re-wired, resulting in a lowering of the operating voltage. Electron-microscopic examination of the old counter wire showed considerable thickening due to the accumulation of fine dust particles. A filter is being installed in the filling line to minimize this effect. Pretreatments are as given in previous date lists unless otherwise stated.

We recently started a systematic approach to determine the reservoir age in southeast Arabia and its dependence on mollusk species and their environment. This part of the study concentrates on local reservoir age and stable isotopes of the lagoonal species Terebralia palustris and Anadara uropigimelana at Khor Kalba, Oman Sea. Environmental and nutritive influences on mollusks are reflected in the radiocarbon and stable isotope signal. We found a local reservoir age of A. uropigimelana of about 940 yr and that of T. palustris as 800 yr. Sclerochronological analyses yielded information about seasonality of growth and death in A. uropigimelana. The modern shell of Periglypta reticulata shares food resources and habitat with Anadara sp., of which we did not find a modern specimen. It provided information on response to changes in temperature in the lagoonal system needed for suitability as reflecting climatic conditions. We were interested in carbon pathways of the mangrove in Kalba and a mangrove planted anew on a former mangrove sediment in Ajman. Being an obvious source of charcoal and food of T. palustris makes this information necessary. Further analyses will be performed to interpret changes in reservoir age in complex lagoonal systems as reaction to environmental variability.

Substantial amounts of annual radiocarbon (14C) data have recently been produced with the purpose of increasing the time resolution of 14C records used for constructing the calibration curve and for studying the occurrence of abrupt cosmic-ray events. In this study, we investigate if it is possible to resolve sub-annual scale changes in the atmospheric 14C content by measuring radiocarbon in early-wood and late-wood fractions from Danish oak. The tree-ring samples span the period 1954–1970 CE, hereby covering the peak of the bomb pulse. A least squares test comparing the atmospheric 14C content and the new sub-annual 14C record from Danish tree rings reveals that by measuring early-wood and late-wood fractions, it may be possible to resolve sub-annual variations in past atmospheric 14C levels.

Several authors have claimed that radiocarbon dates in the Ancient Near East are too early. Herein, a hypothesis that might explain this is presented. Marine degassing of “old” carbon (i.e. 14C-deficient C), induced by upwelling of old subsurface water, has been observed, in modern times, to cause century-scale 14C ages in the surface atmosphere. A review of the Mediterranean Sea post-ice-age circulation concludes that the subsurface waters became very old, primarily due to millennia-long stagnation. It is hypothesized that as the stagnation ended, subsurface waters were brought towards the surface, where they degassed old carbon. Additionally, Anatolian dendrochronology is shown to not contradict the hypothesis.

Amino acid composition data and stable isotope ratios (14N, D, and13C) are being evaluated as sources of information to indicate the presence of non-indigenous organics in bone samples intended for 14C analyses. The study is being conducted in the context of the planned measurement of Pleistocene bone samples by a high energy mass spectrometric 14C detection system.

The following is a list of dates obtained since the time of the compilation of List X in December 1964. The method is essentially the same as that used for the work described in the previous list. Two CO2-CS2 Geiger counter systems are used. The equipment and counting techniques have been described elsewhere (Crane, 1961). The dates and estimates of error in this list follow the practice recommended by the International Radiocarbon Dating Conferences of 1962 and 1965, in that (a) dates are computed on the basis of the Libby half-life, 5570 yr, (b) A.D. 1950 is used as the zero of the age scale, and (c) the errors quoted are the standard deviations obtained from the numbers of counts only. In previous Michigan date lists up to and including VII we have quoted errors at least twice as great as the statistical errors of counting, in order to take account of other errors in the over-all process. If the reader wishes to obtain a standard deviation figure which will allow ample room for the many sources of error in the dating process, we suggest he double the figures that are given in this list.

The early Holocene in North Africa remains a poorly known period, documented unequally by region. Eastern Algeria and Tunisia have the greatest number of deposits, but most were excavated decades ago without the controls and recording required for modern interpretation. The chronological framework is based on radiocarbon (14C) dates that are also old, for the most part. Recent work on Mesolithic lithic industries of Western Europe has enabled us to revive the hypothesis of the existence of contacts between the northern and southern shores of the western Mediterranean at least by the 6th millennium cal BC. A collective research program was conducted in 2016–2017 to test this hypothesis with a particular focus on documenting the technological traditions in the lithic industry and situating them precisely in time. We have 46 new radiocarbon dates that were recently carried out on previously excavated Algerian sites, some of which contain several levels, allowing the construction of Bayesian models. These new measures reinforce the hypothesis of contacts between Europe and Africa by demonstrating the contemporaneity of similar technological processes. Above all, they make it possible to accurately refine the chronology of the main cultural entities of the Maghreb at the beginning of the Holocene.

We have undertaken extensive programs of natural radiocarbon measurement to date the evidence for various events buried in peat bogs. Two case studies are described here: 1) the chronological reconstruction of South Kamchatka volcanic eruptions and, 2) investigation of multi-layered archeological sites in the Upper Volga River Basin. Studies of sample composition and peat taphonomy allowed us to determine the source of 14C age deviations and to reconstruct the environmental history of organic matter accumulation. Data sets, obtained from different types of peat bog and containing traces of these Holocene events, are discussed.

The Marine20 radiocarbon (14C) age calibration curve, and all earlier marine 14C calibration curves from the IntCal group, must be used extremely cautiously for the calibration of marine 14C samples from polar regions (outside ∼ 40ºS–40ºN) during glacial periods. Calibrating polar 14C marine samples from glacial periods against any Marine calibration curve (Marine20 or any earlier product) using an estimate of ${\rm{\Delta R}}$, the regional 14C depletion adjustment, that has been obtained from samples in the recent (non-glacial) past is likely to lead to bias and overconfidence in the calibrated age. We propose an approach to calibration that aims to address this by accounting for the possibility of additional, localized, glacial 14C depletion in polar oceans. We suggest, for a specific polar location, bounds on the value of ${\rm{\Delta }}{{\rm{R}}_{20}}\left( {\rm{\theta }} \right)$ during a glacial period. The lower bound ${\rm{\Delta R}}_{20}^{{\rm{Hol}}}$ may be based on 14C samples from the recent non-glacial (Holocene) past and corresponds to a low-depletion glacial scenario. The upper bound, ${\rm{\Delta R}}_{20}^{{\rm{GS}}}$, representing a high-depletion scenario is found by increasing ${\rm{\Delta R}}_{20}^{{\rm{Hol}}}$ according to the latitude of the 14C sample to be calibrated. The suggested increases to obtain ${\rm{\Delta R}}_{20}^{{\rm{GS}}}$ are based upon simulations of the Hamburg Large Scale Geostrophic Ocean General Circulation Model (LSG OGCM). Calibrating against the Marine20 curve using the upper and lower ${\rm{\Delta }}{{\rm{R}}_{20}}$ bounds provide estimates of calibrated ages for glacial 14C samples in high- and low-depletion scenarios which should bracket the true calendar age of the sample. In some circumstances, users may be able to determine which depletion scenario is more appropriate using independent paleoclimatic or proxy evidence.

This article describes the contribution of the radiocarbon dating method to the authentication of ethnographic objects on some significant examples coming from the collections of the Quai Branly Museum (Paris, France) and the Museum of African Arts (Marseilles, France). The first object is a bludgeon of hard wood from the Tupinambá ethnic group and thought to be brought from Brazil by Andre Thévet, cosmographer of King Francis I. This object supposedly dates to the 16th century. Another example concerns a series of architectural columns, brought from Peru in 1910 by Captain Paul Berthon from the archaeological site of Pachacamac, the largest sanctuary on the central coast of Peru. These pieces have induced a strong reaction in the French scientific community, which has described them as “some vulgar fake” because of a particular decoration and also their unique typology. We will present also the dating of 2 Tibetan textiles and 2 pre-Columbian ponchos made with feathers, which were not well documented. The last example concerns a decorated skull covered with a mosaic of blue and black turquoises and belonging to a civilization predating the Aztecs (AD 1300–1500). All these examples illustrate the decisive contribution of 14C dating to the authentication of museum objects that lack information about their origin.