The calibration of radiocarbon dates on marine materials involves a global marine calibration with regional corrections. Data from well-associated marine and terrestrial materials in archaeological artifacts from northern Chile indicated that the calibration is valid for the period ad 200–900 and suggest that coastal upwelling intensities during that period were similar to those of the early 20th century.

The limits of the statistical evaluation of 14C dates by histograms are discussed. The method of the attempt to establish a global chronology of the short-term eustatic sea-level changes during the Holocene is examined as well as its correlation with the precisely determined Suess wiggles.

The 2-L counter (GSC I) and the 5-L counter (GSC IV) were operated routinely during the past year. The 5-L counter was operated at 1 atm, except for February-March 1967, when it was operated at 4 atm. Approximately half the determinations reported were obtained from each counter.

For over 2 decades, there have been calls for Polynesian archaeologists to identify radiocarbon samples to taxon and material type, and preferentially date short-lived materials. This stems from recognition that even modest amounts of inbuilt age are problematic in this oceanic region where human settlement dates to the last 3 millennia or less. Despite programmatic statements to this effect, and empirical demonstrations of value, uptake of these practices has been slow. This article suggests that short-lived materials be defined as those with lifespans of 10 yr or less, recognizing that reducing the distance between target event and the dated material is an ongoing aim for archaeology. We identify both short-lived materials that are suitable for dating and long-lived species (>75 yr) that should be avoided given their potential for inbuilt age. Additionally, we suggest that given the destructive nature of 14C dating there is value to (1) obtain high-resolution photographs of samples prior to analysis, (2) split samples and archive residuals when possible, and (3) routinely report the tools and expertise used in identification. Past and recent dating analyses at a Polynesian site in the southern Cook Islands are used to illustrate how the suggested protocols might enhance current and future studies. We also establish that mature Calophyllum inophyllum, a common coastal tree and valued timber species, has been in the southern Cook Islands for at least the last 700 yr and is likely to be indigenous and long-lived.

This date list mainly contains results obtained for archaeological samples which were measured in the Groningen laboratory in the course of the years and which have not hitherto been published in a similar form. As such it is an extension of the previous date list (Groningen IV) and reference is made to this publication for information on the method of presentation, the corrections applied, etc. Samples which are primarily of geological significance will be presented separately in next year's list.

C14 measurements reported here were made in this laboratory between December 1, 1961 and October 1, 1962. Sample descriptions are classified as follows:

1. I. Tree-ring dated samples.

2. II. Modern shells from Santa Barbara County, California.

3. III. Archaeologic samples.

4. IV. Palynologic samples.

5. V. Geologic samples.

6. VI. C14 content of caliche.

7. VII. Water samples.

8. VIII. Modern organic sample.

The following is a list of radiocarbon dates obtained since the time of the preparation of Michigan list III.∗ The description of the essential features of our method of measurement as given in the introduction to list III applies to this list. The modern standards used were obtained from hardwood logs, and were of various ages from 75 to 150 years by ring count. These standards were sufficiently old so that no correction for the recent dilution of the atmospheric C14 is believed to be necessary in the dates reported here. The ages of carbonate sample are also calculated from modern wood as a reference standard, without any correction for isotope fractionation.

The following date list consists of samples prepared mainly during 1970 and 1971. Some old measurements, not included in previous lists are added. Ages reported here are calculated using the conventional half-life of 14C: 5568 years and NBS oxalic acid as recent standard.

Terrestrial plant macrofossils from the sedimentary record of Lake Suigetsu, Japan, provide the only quasi-continuous direct atmospheric record of radiocarbon (14C) covering the last 50 ka cal BP (Bronk Ramsey et al. 2012). Since then, new high precision data have become available on U-Th dated speleothems from Hulu Cave China, covering the same time range (Cheng et al. 2018). In addition, an updated varve-based chronology has also been published for the 2006 core from Lake Suigetsu (SG06) based on extended microscopic analysis of the sediments and improved algorithms for interpolation (Schlolaut et al. 2018). Here we reanalyze the radiocarbon dataset from Suigetsu based on the new varve counting information and the constraints imposed by the speleothem data. This enables the new information on the calendar age scale of the Suigetsu dataset to be used in the construction of the consensus IntCal calibration curve. Comparison of the speleothem and plant macrofossil records provides insight into the mechanisms underlying the incorporation of carbon into different types of record and the relative strengths of different types of archive for calibration purposes.

Radiocarbon dating at the Tell el-Daba site in the Nile Delta has created an enigma for many years. Despite great efforts, the difference of about 120 yr between the chronology based on 14C dates and the one based on archaeological evidence linked to the Egyptian historical chronology has not been solved. In order to foster open discussions on this discrepancy, we present here the results of 40 14C accelerator mass spectrometry (AMS) measurements on short-lived plant material assigned to 14 different phases of the Tell el-Daba excavation, spanning 600 yr (about 2000–1400 BC). On the one hand, the recently established agreement between 14C dates and dynastic Egypt (Bronk Ramsey et al. 2010) makes it unlikely that the problem lies in the 14C dates and/or the Egyptian historical chronology. On the other hand, the extensive archaeological evidence from Tell el-Daba linked to many different cultures in the eastern Mediterranean and to the Egyptian historical chronology provides strong evidence for an absolute chronology shifted by about 120 yr with respect to the 14C dates.

The main purpose of this work is to reconstruct the atmospheric Δ 14C in the glacial-postglacial transition, 14,000 – 10,000 BP, a range not covered by the tree-ring calibration curve. We measured 14C/12C ratios on series of terrestrial macrofossils from sediments of two Swiss lakes. We selected exclusively plant remains of recognizable terrestrial origin that are not affected by hard water and thus reflect atmospheric 14C concentration. Due to the scarcity of such material, we used accelerator mass spectroscopy. Cores of two lakes were measured to eliminate local effects and to check the reproducibility of results. This required a reliable, 14C-independent correlation of the cores, obtained through local pollen zone boundaries 14C ages were obtained as a function of the depth in the cores. If sedimentation rates are known ages can be converted into Δ 14C values. We also attempted estimating sedimentation rates; calculations are based on the Swedish varve chronology. Results were combined to form an entire data set. The Δ 14C curve shows an increase with time during the Allerød and decreases during Preboreal and Bølling periods. Probabilities for these 14C variations are discussed.

Charcoal samples from ancient human occupation sites in Australia have been subjected to a rigorous pretreatment and stepped combustion regime in order to explore the possibility that these sites may be older than previous radiocarbon dating had suggested. In one case, the Devil's Lair site in southwest Australia, the methodology has clearly removed vestiges of contamination by more modern carbon and has led to a revised radiocarbon chronology that provides evidence for human occupation of southwest Australia by at least 44 ka BP and probably by 46–47 ka BP. In contrast, charcoal from the Nauwalabila site has been so severely altered that insufficient of the original carbon remains for reliable 14C dating. Finally, where the charcoal is well preserved, such as at the Carpenter's Gap site, the new results provide reassurance that earlier 14C results of ∼40 ka BP are indeed true ages and are not simply at the limit of the 14C technique.

We report on new 14C measurements of samples of 18 texts (scrolls) and 2 linen fragments from Qumran Caves 1, 2, and 4 and from Nahal Hever, both in the Dead Sea region. The radiocarbon results are in good agreement with estimates of age based on paleography.

We measured the 14C content of 36 living marine molluscs from Tairua Harbour and the rocky coast on the Coromandel Peninsula of New Zealand. We identified species suitable for radiocarbon dating and show that the open marine intertidal zone is enriched in 14C compared to the open marine subtidal zone or estuary. We also found a uniform 14C distribution in the Tairua Harbour, by analyzing samples of the estuarine bivalve Austrovenus stutchbwyi collected up to 5 km from the harbor entrance.

Databases of accumulated paleoecological and archaeological records provide a means for large-scale syntheses of environmental and cultural histories. We describe the current status of the Canadian Archaeological Radiocarbon Database (CARD), a searchable collection of more than 36,000 14C dates from archaeological and paleontological sites from across North America. CARD, built by the late Dr Richard Morlan of the Canadian Museum of Civilization, consists of uncalibrated 14C data as well as information about the material dated, the cultural association of the date (e.g. Paleoindian, Archaic, Woodland), and its geographic location. The database can be used to study questions relating to prehistoric demography, migrations, human vulnerability to environmental change, and human impact on the landscape, but biases relating to sampling intensity and taphonomy must first be accounted for. Currently, Canada and the northern United States are well represented in the database, while the southern United States is underrepresented. The frequency of 14C dates associated with archaeological sites increases through time from 15,000 cal yr BP until European contact, which likely reflects, among other factors, both the destruction of older cultural carbon due to erosion and dissolution and increasing population numbers through time. An exploratory analysis of the dates reveals their distribution in both time and space, and suggests that the database is sufficiently complete to enable quantitative analysis of general demographic trends.

Determined independently from annually laminated ice cores and lake sediments, and German pines, the calendar ages of Younger Dryas (YD) boundaries significantly disagree with one another. 14C dates, plotted vs. calendar ages for samples from different sediments, also reveal distinct offsets. The adjustment of varve chronologies to synchronize the boundaries of the YD nearly cancels the discrepancies between 14C data, and supports the synchronism of the YD cold period over the North Atlantic region. However, the exact timing of the event cannot be estimated in this way.

In situ radiocarbon inorganic production and retention pathways are distinct from those of the more commonly used traditional organic/atmospheric 14C. In addition, a growing number of laboratories are extracting in situ cosmogenic 14C from quartz, using a variety of analytical techniques. As such, a flexible yet internally consistent set of procedures for data reduction that recognizes the unique nature of the in situ14C system is essential for reliable comparison of results among laboratories. This article thus presents a brief data reduction framework that can accommodate differences in both AMS and laboratory analytical techniques.

Radiocarbon (14C) measurements of foraminifera often provide the only absolute age constraints in marine sediments. However, they are often challenging as their reliability and accuracy can be compromised by reduced availability of adequate sample material. New analytical advances using the MIni CArbon DAting System (MICADAS) allow 14C dating of very small samples, circumventing size limitations inherent to conventional 14C measurements with accelerator mass spectrometry (AMS). Here we use foraminiferal samples and carbonate standard material to assess the reproducibility and precision of MICADAS 14C analyses, quantify contamination biases, and determine foraminiferal 14C blank levels. The reproducibility of conventional 14C ages for our planktic (benthic) foraminiferal samples from gas measurements is 200 (130) yr, and has good precision as illustrated by the agreement between both standards and their reference values as well as between small gas- and larger graphitized foraminiferal samples (within 100±60 yr). We observe a constant contamination bias and slightly higher 14C blanks for foraminifera than for carbonate reference materials, limiting gas (graphite) 14C age determinations for foraminifera from our study sites to ~38 (~42) kyr. Our findings underline the significance of MICADAS gas analyses for 14C on smaller-than-conventional sized foraminiferal samples for paleoclimate reconstructions and dating.

The acid-base-acid (ABA) procedure is a common chemical pretreatment used on most organic matter samples. Although this pretreatment is straightforward, there is no consensus among labs about the optimum strength of the chemicals, or even the temperature, to be used for digestions. Comparisons between 14C results obtained by samples undergoing ABA against other wet oxidations, such as acid-base oxidation followed by stepped-combustion (ABOX-SC) or α-cellulose on wood, have sometimes suggested that ABA does not always remove all contaminating carbon. In addition, if not all ABA protocols are the same, could it be said that one procedure is better than others or comparable to wet-oxidation pretreatments, if rigorously applied? To determine whether 14C-free samples showed any fraction modern carbon (FmC) deviations due to pretreatment strategies, 3 experiments were carried out. The first compared 14C results for wood samples at or near the limit of 14C dating, pretreated with a standard ABA protocol used at UC Irvine's Keck Carbon Cycle Accelerator Mass Spectrometry (KCCAMS) facility, with those obtained from ABA- and ABOX-SC-prepared aliquots of the same samples performed at Australian National University (ANU) in 2001. The second experiment subjected wood samples, ranging from ∼12 ka BP to 14C-free, to 5 selected published ABA pretreatments. Third, we evaluated whether the ABA protocol needs a higher-strength final acid step (particularly important for removing CO2 absorption when samples are submerged in alkaline solutions). We are able to show that rigorous ABA treatments exist that can provide robust, reproducible results for many wood samples that are known to be >>50 ka BP, implying that a lack of control over the procedure's outcome might be sample-related, rather than due simply to inadequacies in the chemical pretreatment.

New Arizona high precision Δ14C data back to 6500 BC plot close to an 11,300-yr period sinusoid extrapolated from the post 5300 BC data (offset = +32‰, half amplitude = 51‰ and phase lag = 2.29 radians). The trend curve is modulated by high latitude components of the non-dipole field with a fundamental period of 2400 yr. Based upon a model of Lund and Banerjee (1985), the non-dipole field rotates and every 1200 yr the high latitude maxima pass over the north magnetic pole and near the south magnetic pole in reversed polarity. This modulates cosmic ray production producing extended maxima ca AD 1700, 700 bc, 3100 bc, and 5500 bc. The 2400 period appears to be stationary. The magnetic field also modulates the amplitude of the solar activity induced cycles of periods 200, 80, and 11 yr as can be seen in the Zürich-Bern Camp Century ice core data as well as in the Δ14 C fluctuation data. Reinterpretation of the Camp Century 10Be data indicates that it is in agreement with magnetic field as well as solar activity modulation of terrestrial radioisotope production.