In the preceding paper (Stuiver and Östlund, this issue), some of the general features of the Geochemical Ocean Section Study (GEOSECS) were outlined and results were listed for the Atlantic Ocean. This paper will deal with the second major cruise, which was described by Craig and Turekian (1976), covering the Pacific Ocean in 1973-74 (cf fig 1).

This paper presents a compilation of atmospheric radiocarbon for the period 1950–2019, derived from atmospheric CO2 sampling and tree rings from clean-air sites. Following the approach taken by Hua et al. (2013), our revised and extended compilation consists of zonal, hemispheric and global radiocarbon (14C) data sets, with monthly data sets for 5 zones (Northern Hemisphere zones 1, 2, and 3, and Southern Hemisphere zones 3 and 1–2). Our new compilation includes smooth curves for zonal data sets that are more suitable for dating applications than the previous approach based on simple averaging. Our new radiocarbon dataset is intended to help facilitate the use of atmospheric bomb 14C in carbon cycle studies and to accommodate increasing demand for accurate dating of recent (post-1950) terrestrial samples.

Ultrafiltration of bone collagen provides a method of purification that can be very effective in reducing environmental contamination from soil-derived amino acids as well as removing degraded collagen or other short-chain proteins. The Oxford Radiocarbon Accelerator Unit (ORAU) first implemented ultrafiltration in the pretreatment of bone material for accelerator mass spectrometry (AMS) radiocarbon dating in 2000. However, the filters themselves contain carbonaceous material, and thus stringent quality control is required to demonstrate that this does not affect the accuracy of the dating. Here, we present quality assurance data from the bone pretreatment and dating program at ORAU, including dates on known-age and background-age bones over a range of sample sizes, and measurements of residual carbon contamination present in the filters after cleaning.

Like Lamont VI (Broecker and Olson, 1959), this list contains only results on samples of known age (most of which formed during the past ten years). The measurements were made largely in order to gain an understanding of the distribution of radiocarbon within the dynamic carbon reservoir. Again, the data are not reported primarily with the idea of drawing new conclusions but rather to bring together in one place information which is presently scattered throughout the literature or which otherwise might remain unpublished.

High-precision measurement of dendrochronologically dated Irish oak at bi-decade/decade intervals has continued in the Belfast laboratory, extending the 14C data base from ca AD 1840 to 5210 BC. The dendrochronology is now considered absolute (see Belfast dendrochronology this conference) (Brown et al, 1986) and a continuous detailed curve is presented, showing the natural variations in the atmospheric concentration of 14C over >7000 years. Each data point has a precision of <2.5., and some 4500 years have now been compared with Seattle, giving excellent agreement. Discussion of this data base and the justification of the claimed accuracy is given together with a comparison of other chronologies. Some of the advantages and limitations of the above are discussed.

Radiocarbon measurements of nine known age shells from the Mediterranean and the Aegean Seas combined with previous measurements provide an updated value for δR, the local variation in the reservoir correction for marine samples. Comparison of pre-1950s samples from the Algerian coast, with one collected in 1954, indicates early incorporation of nuclear weapons testing 14C into the shallow surface waters of the Mediterranean. Comparisons between different basins indicate the surface waters of the Mediterranean are relatively homogenous. The recommended δR for calibration of the Mediterranean marine samples with the 1998 marine calibration dataset is 58 ± 85 14C yr, but variations in the reservoir age beyond 6000 cal BP should be considered.

This paper is a twin paper to that of Stuiver and Pearson (1986) which covers the time period ad 1950–500 bc. The combined radiocarbon ages of dendrochronologically dated wood presented in this paper covers the time period 500–2500 bc.

Bone samples from the Greenland Viking colony provide us with a unique opportunity to test and use 14C dating of remains of humans who depended upon food of mixed marine and terrestrial origin. We investigated the skeletons of 27 Greenland Norse people excavated from churchyard burials from the late 10th to the middle 15th century. The stable carbon isotopic composition (δ13C) of the bone collagen reveals that the diet of the Greenland Norse changed dramatically from predominantly terrestrial food at the time of Eric the Red around AD 1000 to predominantly marine food toward the end of the settlement period around AD 1450. We find that it is possible to 14C-date these bones of mixed marine and terrestrial origin precisely when proper correction for the marine reservoir effect (the 14C age difference between terrestrial and marine organisms) is taken into account. From the dietary information obtained via the δ13C values of the bones We have calculated individual reservoir age corrections for the measured 14C ages of each skeleton. The reservoir age corrections were calibrated by comparing the 14C dates of 3 highly marine skeletons with the 14C dates of their terrestrial grave clothes. The calibrated ages of all 27 skeletons from different parts of the Norse settlement obtained by this method are found to be consistent with available historical and archaeological chronology. The evidence for a change in subsistence from terrestrial to marine food is an important clue to the old puzzle of the disappearance of the Greenland Norse, obtained here for the first time by measurements on the remains of the people themselves instead of by more indirect methods like kitchen-midden analysis.

A high-precision calibration curve, derived from the radiocarbon age determinations of 195 decade samples spanning the AD 1 to 1950 interval, is presented.

Though derived for the Pacific Northwest and California, the curve can be used for a large part of the northern hemisphere. This is proven by the radiocarbon ages of contemporaneous sample pairs which are, in most instances, identical within the quoted precision. Two sets of single-year data reveal no evidence for an 11-year cycle with an amplitude beyond the 12-year measuring precision. This indicates that the calibration curve is also applicable for single-year 14C samples.

Analysis of the Seattle data sets and comparison with those published by the Belfast, La Jolla, and Heidelberg laboratories show that the total variability in a radiocarbon age determination is often larger than that predicted from the quoted errors. Upper limits for the error multiplier (ie, the factor with which the quoted error has to be multiplied to obtain the overall laboratory variability) are estimated at 1.5 for Seattle and Belfast, 1.1 to 1.4 for La Jolla, and 2.0 for Heidelberg.

The comparisons with Belfast, La Jolla, and Heidelberg also reveal offsets with the Seattle calibration curve of, respectively, 4, 27 to 55, and 58 years. These offsets are most likely due to laboratory bias. An improvement of the present calibration curve by combining data sets from other laboratories will only be possible when offsets and error multipliers are precisely known through interlaboratory calibration.

It has become generally accepted during the last year that 14C fluctuations, the so-called “wiggles”, observed in wood, dated by its tree rings, do indeed exist. Furthermore the La Jolla measurements show that apart from experimental noise, they do not represent random red noise, but characteristic, recurring features. In 1971, Houtermans found indications for the existence of cyclic components and recent Fourier analyses of all the available data by Neftel and Hartwig show a 200-year component. Cyclic oscillations with other periods appear to be present during limited time intervals. The character of the oscillations is not harmonic. The time derivative of many fluctuations is remarkably constant and such that the 14C rises by 1 percent in about 20 years and decreases by 1 percent in slightly more than twice that length of time. The properties of the overall radiocarbon record have to be considered in attempts to explain the variations in terms of variations of the cosmic ray-production rate and changes of the geochemical distribution of radiocarbon.

We have refined marine reservoir age estimates for eastern Pacific coastal waters with radiocarbon measurements of mollusk shells collected prior to 1950. We have also investigated interspecific variability in 14C ages for historic and ancient shells from San Francisco Bay.

During the last decade radiocarbon dating has been used extensively in distinct regions of Brazil to provide information about soil chronology in paleoenvironmental studies. This paper presents 14C data of soil organic matter (SOM), humin fraction, and charcoal in several soil profiles under natural vegetation from different Brazil locations (north, central, and southeast regions). The main objective is to compare the obtained 14C dating of total SOM with humin, the oldest fraction of SOM. In order to validate the humin ages these data are compared with the age of charcoal collected at similar depths. The 14C ages obtained on charcoal were, in most of the cases, in agreement with the humin fraction considering the experimental errors, or 20% older in average. The dates obtained from total SOM showed significantly younger ages than the humin fraction indicating contamination by younger carbon. These results show the humin fraction is considered a reliable material for 14C dating in soils. However, the humin fraction ages could be assumed as the minimum ages for carbon in soils.

Radiocarbon age determinations of wood charcoal are commonly used to date past forest fire events, even though such ages should be greater than the fire event due to the age of the wood at the time of burning. The difference in the 14C-derived age of charcoal and the time-since-fire (the “inbuilt age”) may be considerable in some vegetation types and thus must be estimated before interpreting fire dates. Two methods were used to estimate the potential range of inbuilt age of soil charcoal dated to determine ages of forest fires on the west coast of Vancouver Island (Canada). First, 26 14C ages on charcoal in surficial soil were compared directly with ages of forest fire determined by tree-ring counts, suggesting inbuilt ages of 0–670 years. Second, a simulation model that uses estimated fuel loads, fuel consumption, charcoal production, and the ages of charred wood (time since wood formation), suggests that the combination of slow growth rates and slow decay rates of certain species can account for inbuilt ages of more than 400 years in this forest type. This level of inbuilt age is large enough such that the actual age of a fire may not occur within the 2σ confidence interval of a calibrated charcoal 14C age determination, and thus significantly affect the interpretation of fire dates. A method is presented to combine the error of a calibrated 14C age determination with the error due to inbuilt age such that the larger adjusted error encompasses the actual age of the fire.

The last decade has seen the development of a range of new statistical and computational techniques for analysing large collections of radiocarbon (14C) dates, often but not exclusively to make inferences about human population change in the past. Here we introduce rcarbon, an open-source software package for the R statistical computing language which implements many of these techniques and looks to foster transparent future study of their strengths and weaknesses. In this paper, we review the key assumptions, limitations and potentials behind statistical analyses of summed probability distribution of 14C dates, including Monte-Carlo simulation-based tests, permutation tests, and spatial analyses. Supplementary material provides a fully reproducible analysis with further details not covered in the main paper.

In this study we report on accelerator mass spectrometry (AMS) wiggle-match dating of selected macrofossils from organic deposits ca. 800 cal bc (ca. 2650 bp). Based on paleological, archaeological and geological evidence, we found that the sharp rise of atmospheric 14C between 850 and 760 cal bc corresponds to the following related phenomena:

1. 1. In European raised bog deposits, the changing spectrum of peat forming mosses and a sharp decline in decomposition of the peat indicate a sudden change from relatively dry and warm to cool, moist climatic conditions.

2. 2. As a consequence of climate change, there was a fast and considerable rise of the groundwater table so that peat growth started in areas that were already marginal from a hydrological point of view.

3. 3. The rise of the groundwater table in low-lying areas of the Netherlands resulted in the abandonment of settlement sites.

4. 4. The contemporaneous earliest human colonization of newly emerged salt marshes in the northern Netherlands (after loss of cultivated land) may have been related to thermal contraction of ocean water, causing a temporary stagnation in the relative sea-level rise.

Furthermore, there is evidence for synchronous climatic change in Europe and on other continents (climatic teleconnections on both hemispheres) ca. 2650 bp. We discuss reduced solar activity and the related increase of cosmic rays as a cause for the observed climatological phenomena and the contemporaneous rise in the 14C-content of the atmosphere. Cosmic rays may have been a factor in the formation of clouds and precipitation, and in that way changes in solar wind were amplified and the effects induced abrupt climate change.

Statistical analysis is becoming much more widely used in conjunction with radiocarbon dating. In this paper I discuss the impact of Bayesian analysis (using computer programs such as OxCal) on archaeological research. In addition to simple analysis, the method has implications for the planning of dating projects and the assessment of the reliability of dates in their context.

A new formalism for describing chronological models is introduced here: the Chronological Query Language (CQL), an extension of the model definitions found in the program OxCal.

New methods of Bayesian analysis can be used to overcome some of the inherent biases in the uncertainty estimates of scientific dating methods. Most of these methods, including 14C, uranium series and thermoluminescence (TL), tend to favor some calendar dates over others. 14C calibration overcomes the problem where this is possible, but a Bayesian approach can be used more generally.

The novel tabletop miniaturized radiocarbon dating system (MICADAS) at ETH Zurich features a hybrid Cs sputter negative ion source for the measurement of solid graphite and gaseous CO2 samples. The source produces stable currents of up to 6 μA C− out of gaseous samples with an efficiency of 3–6%. A gas feeding system has been set up that enables constant dosing of CO2 into the Cs sputter ion source and ensures stable measuring conditions. The system is based on a syringe in which CO2 gas is mixed with He and then pressed continuously into the ion source at a constant flow rate. Minimized volumes allow feeding samples of 3–30 μg carbon quantitatively into the ion source. In order to test the performance of the system, several standards and blanks have successfully been measured. The ratios of 14C/12C could be repeated within statistical errors to better than 1.0% and the 13C/12C ratios to better than 0.2%. The blank was <1 pMC.

Human bones from single inhumation burials and artifacts made from terrestrial mammal (ungulate) bone found in direct association with the skeletons were obtained from the Stone Age site of Schela Cladovei situated just below the Iron Gates Gorge of the River Danube. The results of stable isotope analyses of the human bone collagen are consistent with a heavy dependence on aquatic protein while radiocarbon dating of the samples reveals an offset of 300–500 years between the two sample types, indicating a freshwater reservoir effect in the human bone samples. Since protein consumption is by far the major source of nitrogen in the human diet we have assumed a linear relationship between δ15N and the level of aquatic protein in each individual's diet and derived a calibration for 14C age offset versus δ15N which has been applied to a series of results from the site at Lepenski Vir within the gorge. The corrected 14C ages (7310-6720 BP) are now consistent with the previous 14C age measurements made on charcoal from related contexts (7360–6560 BP). In addition, the data indicate a change from a primarily aquatic to a mixed terrestrial/aquatic diet around 7100 BP and this may be argued as supporting a shift from Mesolithic to Neolithic. This study also has wider implications for the accurate dating of human bone samples when the possibility exists of an aquatic component in the dietary protein and strongly implies that δ15N analysis should be undertaken routinely when dating human bones.

Since our first report on the performance of the Kiel accelerator mass spectrometry (AMS) system and our early work on sample preparation, systems have been built to improve the sample quality and throughput of the laboratory. Minor modifications were also made on the AMS system, mainly in order to reduce the amount of work and time needed to maintain the system in optimal condition. The design and performance of a 20-port reduction system, a pneumatic target press, and a remote alarm unit for the AMS system are discussed, along with an overview of the results obtained during the last year and the procedure used to obtain them. Statistical analysis shows that the contribution of the AMS system to the measuring uncertainty at our current level (0.3% for a modern sample) is negligible.

Increased marine 14C reservoir ages from the surface water of the North Atlantic are documented for the Younger Dryas period. We use terrestrial and marine AMS 14C dates from the time of deposition of the Icelandic Vedde Ash to examine the marine 14C reservoir age. This changed from its modem North Atlantic value of ca. 400 yr to ca. 700 yr during the Younger Dryas climatic event. The increased marine reservoir age has implications for both comparing climatic time series dated by 14C and understanding palaeoceanographic changes that generated the increase.