In the present work, we assess the chronology of archaeological sites known as earthen mounds, commonly found at the Pampas biome, among the lowlands of Brazil, Uruguay, and Argentina. We focused on the Pontal da Barra settlement, which is a testimony of the long-term occupation of indigenous groups in the swamp and wet environment of Patos Lagoon, southern Brazil. A Bayesian chronological model based on the radiocarbon (14C) dating of 17 samples of fish otolith, 5 charcoal fragments, and 2 bones (human and dog) allowed determination of the beginning of the occupation as well as the occupational synchronism of the different mounds. The nature of the samples allows us to study the local 14C reservoir effect through the comparison between the group of marine and terrestrial samples, deriving a reservoir offset value of 63±53 14C yr for this particular area, indicating a strong freshwater influence in the lagoon system. We estimate the start of human intervention in the landscapes of southern Patos Lagoon to be around 2200 cal BP, with the most intense activity between 1800 and 1200 cal BP.

This work presents an attempt to date brines and determine flow rates of hypersaline groundwater in the extremely dynamic system of the Dead Sea (DS), whose level has dropped in the last 30 yr by ∼20 m. The processes that affect the carbon species and isotopes of the groundwater in the DS area were quantified in order to estimate their flow rate based on radiocarbon and tritium methods. In contrast to the conservative behavior of most ions in the groundwater, the carbon system parameters indicate additional processes. The dissolved inorganic carbon (DIC) content of most saline groundwater is close to that of the DS, but its stable isotopic composition (δ13CDIC) is much lower. The chemical composition and carbon isotope mass balance suggest that the low δ13CDIC of the saline groundwater is a result of anaerobic organic matter oxidation by bacterial sulfate reduction (BSR) and methane oxidation. The radiocarbon content (14CDIC) of the saline groundwater ranged from 86 pMC (greater than the ∼82 pMC value of the DS in the 2000s) to as low as 14 pMC. The similarity between the 14CDIC value and Na/Cl ratio of the groundwater at the DS shore and that of the 1980s DS brine indicates that the DS penetrated to the aquifer at that time. The low 14CDIC values in some of the saline groundwater suggest the existence of ancient brine in the subaquifer.

The chief objective of this paper is to improve our understanding of the Neolithic in Eastern Hungary using absolute chronological data. To accomplish this we calibrated new measurements as well as previously published dates. The up-to-date, standardized evaluation of 261 calibrated measurements showed temporal overlaps between archaeological cultures defined on the basis of ceramic styles. The increasing number of dates suggest that the Neolithic period began at the turn of the 6th and 7th millennia bc and lasted for ca. 1500 yr in the present area of the Great Hungarian Plain (Alföld). Further research should be aimed at complementing the current data set with dates from western Hungary and establishing additional correlations among stratigraphic, typological and radiocarbon dates.

In the Copenhagen I and II date lists radiocarbon dates for samples representing the late-glacial Aller⊘d oscillation and early Neolithic periods in Switzerland and Denmark were given. At the time of publication no account was taken of the dilution of the atmosphere with inactive carbon by the extensive combustion of fossil fuels since the Industrial Revolution (Suess, 1955), and of its influence on the dating results. This effect as measured by Suess amounted to 3.4% depletion in wood samples from the heavily industrialized east coast of the United States. Several later measurements have shown that the magnitude of this reduction in atmospheric C14 concentration varies in different areas. The average universal decrease was calculated by Fergusson (1958) as 2.03 ± .15%. However, the magnitude of reported Suess effects may vary with the chosen reference sample as a result of periodic changes (de Vries effect) in the atmospheric C14 concentration as found by de Vries (1958).

Osteocalcin, a non-collagen bone-matrix protein, has been examined as a possible source of autochthonous 14C data in fossil bones where collagen has been seriously degraded. Extraction procedures for osteocalcin yield a well-characterized product that can be clearly distinguished from collagen. The Gla content indicates that osteocalcin is present in the fossil bones at levels similar to the range present in modern bone. However, it appears to be extracted primarily as proteolytic polypeptide fragments rather than as an intact protein. Concordant 14C determinations are obtained on osteocalcin and gelatin extracts from the same bone when the collagen is relatively well preserved. However, increasing discordances in the 14C values of the osteocalcin and gelatin fractions are associated with reduced concentrations of the gelatin extract in the bone.

During the late 1960s, N. J. van der Merwe (1969) obtained 14C measurements on 11 iron pieces, ranging in carbon content from medium carbon (0.22%) wrought iron (1.2 kg used) to high carbon (3.2%) cast iron (30 g), thereby demonstrating the feasibility of the technique for 14C dating iron. In the early 1980s, Sayre et al. (1982) repeated two of van der Merwe's measurements, and carried out two analyses on a recently rediscovered Elizabethan(?) iron bloom. Thirty grams were required of this medium carbon wrought iron to obtain an age using small proportional counters. A number of iron artifacts have recently been analyzed by accelerator mass spectrometry (AMS) at IsoTrace. Samples ranged in size from 3.4 g of a medium carbon (≃0.4%) wrought iron bloom to 274 mg for a high carbon (1.79%) wootz steel fragment. AMS now permits analysis of samples that previously were too small or too valuable to be analyzed. For larger samples, multiple analyses can reveal variations that may aid the evaluation of sample history.

The dating of the settlement of Iceland has been debated for many years. According to written sources (sagas) from the early 12th century, the first Norwegian settlers arrived in Iceland in AD 874. However, some 14C dates from the earliest archaeological sites in Iceland, invariably from samples of birch and other indigenous wood species, have yielded surprisingly old ages, older by 100–150 yr than the historical date, suggesting that the settlement took place in the 7th or 8th century. In this paper, we report 16 new 14C dates of pairs of barley grain and wood samples from an excavation in Reykjavík in 2001. The new results show that the wood samples tend to be older than the grain samples by up to about 100 yr. We argue that the barley grains give the true date (AD 890), whereas the wood dates are too old. The grain dates are in close agreement with the settlement year quoted in the written sources. In particular, our new data eliminate the need of any of the ad hoc theories introduced up to now to explain the suspiciously high 14C ages of wood samples from the settlement of Iceland, namely, 1) the island effect, 2) the volcanic or geothermal effect, or 3) that settlement actually took place significantly before the time recorded in the sagas.

During the last three years the ETH-EN-tandem accelerator facility has been adapted for the quantitative determination of the rare isotopes 14C and 10Be in mg samples. The goal of this project is to routinely achieve a 1% accuracy when measuring 14C/12C ratios with a minimum expenditure of human resources and beam time. The concept is similar to that proposed by Purser and Henley (1978). The early evolution of this dating facility was described previously (Suter et al, 1981a,b). This paper is a brief report on the current status of the system and its development.

The Δ14C content of surface waters in and around the Cariaco Basin was reconstructed from radiocarbon measurements on sub-annually sampled coral skeletal material. During the late 1930s to early 1940s, surface waters within and outside of the Cariaco Basin were similar. Within the Cariaco Basin at Islas Tortugas, coral Δ14C averages −51.9 ± 3.3%. Corals collected outside of the basin at Boca de Medio and Los Testigos have Δ14C values of −53.4 ± 3.3% and −54.3 ± 2.6, respectively. Additional 14C analyses on the Isla Tortugas coral document an ∼11% decrease between ∼1905 (−40.9 ± 4.5%) and ∼1940. The implied Suess effect trend (−3%/decade) is nearly as large as that observed in the atmosphere over the same time period. If we assume that there is little to no fossil fuel 14CO2 signature in Cariaco surface waters in ∼1905, the waters have an equivalent reservoir age of ∼312 yr.

We analyze here the time record of total carbonate carried as CaCO3 in a sea-bottom core from the Ionian Sea. Several major periods appear, most strongly at 1100, 690, 500, 340, 250 and 90 yr, confirmed both in the periodogram and maximum entropy estimates. The Gleissberg period appears in common with the 14C and other records, such as the sunspot index and aurorae. The manifestation of this period in what we surmise to be a climatic record is further evidence that the Gleissberg period has correlated bolometric and electrodynamic aspects.

Primary and secondary standards are essential in radiocarbon analyses for the purpose of reporting and comparing data among laboratories, as well as for internal laboratory data quality control. ANU sucrose is one of the IAEA-certified 14C standards (C-6) with a consensus value of 1.5061 ± 0.0011 fraction modern (Fm). All of our measurements of ANU sucrose (n = 351) as a secondary standard over the last 7 yr result in an average value of 1.5016 ± 0.0005 Fm (2-σ standard error). After applying the same outlier tests used for IAEA reference standards, a weighted average value of 1.5016 ± 0.0002 Fm (n = 294) was calculated. This value is significantly lower than the IAEA C-6 consensus value (t test with unequal variance; p = 0.023). In contrast, our measurements of other secondary standards over the same time period are in excellent agreement with their respective consensus values. Since ANU is the only secondary standard measured in our lab that does not agree with the consensus values, and we have measured a larger number analyses compared to what went into the definition of the consensus value, we suggest that the consensus value of ANU sucrose might be too high by ∼0.0045 ± 0.0011 Fm. Given that some labs routinely use ANU sucrose as a primary standard, our results suggest that revisiting the consensus value of ANU sucrose may be necessary.

The Caribbean Archaic Age (about 3000–500 BC) is thought to represent the earliest migration of humans from South America into the Lesser Antilles. However, there is a conspicuous absence of these early sites on islands south of the Guadeloupe Passage. To date, only a single radiocarbon date derived from a Queen conch (Strombus [Eustrombus] gigas) shell at the Heywoods site on Barbados was indicative of an Archaic occupation in the southern Antilles apart from a scattering of poorly reported (and mostly undated) sites. Given a number of issues associated with reliance on a single date to establish a cultural horizon, along with other problems derived from possible carbonate cement contamination and dating marine shells of a longer-lived species such as Queen conch, 2 additional samples were taken from the same unit and context at Heywoods to confirm whether the site is truly representative of an occupation during the Archaic Age. Results from a Queen conch shell adze in Context 7 dated to 2530–2200 BC (2 σ) and overlaps with the only other Archaic date from the site dating to 2320–1750 cal BC, while a juvenile specimen of the same species from Context 8 at 3280–2940 BC (2 σ) indicates that Barbados may have been settled even earlier. This suggests that Heywoods may be the oldest site between Trinidad and Puerto Rico. While further confirmation is required, these new dates have implications for understanding the nature of migratory ventures in the Caribbean, such as whether the “Southward Route” hypothesis—which postulates that earlier migration events from South America during the Ceramic Age (beginning ∼500 BC) initially bypassed the southern Lesser Antilles—also applies to the Archaic, and if other phenomena such as active volcanism may have played a role in structuring settlement patterns. Questions also remain as to why Heywoods does not exhibit the typical lithic Archaic tool kit.

The construction and performance of a proportional CO2 counter system is described by which an over-all accuracy is obtained of 1.3‰ after a two-day counting period.

Connecting calendar ages to radiocarbon (14C) ages, i.e. constructing a calibration curve, requires 14C samples that represent, or are closely connected to, atmospheric 14C values and that can also be independently dated. In addition to these data, there is information that can serve as independent tests of the calibration curve. For example, information from ice core radionuclide data cannot be directly incorporated into the calibration curve construction as it delivers less direct information on the 14C age–calendar age relationship but it can provide tests of the quality of the calibration curve. Furthermore, ice core ages on 14C-dated volcanic eruptions provide key information on the agreement of ice core and radiocarbon time scales. Due to their scarcity such data would have little impact if directly incorporated into the calibration curve. However, these serve as important “anchor points” in time for independently testing the calibration curve and/or ice-core time scales. Here we will show that such information largely supports the new IntCal20 calibration record. Furthermore, we discuss how floating tree-ring sequences on ice-core time scales agree with the new calibration curve. For the period around 40,000 years ago we discuss unresolved differences between ice core 10Be and 14C records that are possibly related to our limited understanding of carbon cycle influences on the atmospheric 14C concentration during the last glacial period. Finally, we review the results on the time scale comparison between the Greenland ice-core time scale (GICC05) and IntCal20 that effectively allow a direct comparison of 14C-dated records with the Greenland ice core data.

The Swedish varve chronology, or Swedish Time Scale, is an annual chronology based upon the successive correlation of more than 1000 varve-thickness diagrams. The Late Glacial-Early Holocene varved clays were deposited as glaciolacustrine sediments in the Baltic Sea during the recession of the Scandinavian ice sheet. Formation of varved clays continued throughout the Holocene and is still going on in the estuary of River ångermanälven in northern Sweden. Accelerator mass spectrometry (AMS) radiocarbon measurements, which have been performed on terrestrial plant macrofossils extracted from the varved clays, show—in comparison with other annual chronologies—that several hundreds of varve years are missing in the varve chronology. These findings are supported by, among others, pollen stratigraphic investigations on time-equivalent varve year intervals. If an effort were undertaken to evaluate the erroneous parts, the Swedish Time Scale would have the potential of becoming a continuous annual chronology.

Organic carbon (OC) radiocarbon (14C) signatures in marine surface sediments are highly variable and the causes of this heterogeneity remain ambiguous. Here, we present results from a detailed 14C-based investigation of an Arabian Sea sediment, including measurements on organic matter (OM) in bulk sediment, specific grain size fractions, and OC decomposition products from ramped-pyrolysis-oxidation (RPO). Our results show that 14C ages of OM increase with increasing grain size, suggesting that grain size is an important factor controlling the 14C heterogeneity in marine sediments. Analysis of RPO decomposition products from different grain size fractions reveals an overall increase in age of corresponding thermal fractions from finer to coarser fractions. We suggest that hydrodynamic properties of sediment grains exert the important control on the 14C age distribution of OM among grain size fractions. We propose a conceptual model to account for this dimensionality in 14C variability that invokes two predominant modes of OM preservation within different grain size fractions of Arabian Sea sediment: finer (<63 µm) fractions are influenced by OM-mineral grain aggregation processes, giving rise to relatively uniform 14C ages, whereas OM preserved in coarser (>63 µm) fractions includes materials encapsulated within microfossils and/or entrained fossil (14C-depleted) OC hosted in detrital mineral grains. Our findings highlight the value of RPO for assessment of 14C age variability in sedimentary OC, and for assessing mechanisms of OM preservation in aquatic sediments.

The following is a list of dates obtained since the time of the compilation of List IX in December 1963. The method is essentially the same as that used for the work described in the previous list. Two CO2-CS2 Geiger counter systems were used. The equipment and counting techniques have been described elsewhere (Crane. 1961a, 1961b). The dates and estimates of error in this list follow the practice recommended by the International Radiocarbon Dating Conference of 1962, 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 other sources of error in the dating process, we suggest he double the figures that are given in this list.

A formally modeled radiocarbon chronology for a new profile through the great Neolithic tell of Vinča-Belo Brdo, Serbia, is the third interwoven strand in refining the chronology of the tell. This now joins models for the whole sequence based on the archive of early excavations, and for the last two known horizons at the top of the settlement mound, investigated in recent decades. In the new deep sounding, Vinča culture occupation from the 52nd century cal BC is slightly later than in the main sequence, probably reflecting the horizontal extension of the tell as it began to grow. The last dated occupation falls in the late 47th–early 46th century cal BC, slightly earlier than in the main sequence, but the top of the profile is affected by the slippage that caused the new excavations. Formal estimates are given for the succession and varying durations of burnt and unburnt houses, and indicate a period in the first part of the 5th millennium without house burning. Overall, the combined results from the three interwoven strands serve to produce a radically enhanced understanding of the temporality of the tell, which builds on, rather than supplants, previous research. We knew previously that Vinča-Belo Brdo was very long-lived, but now we can time that history with much greater precision. We can assert with much greater confidence that its vertical buildup was steady and largely uninterrupted. We have begun, from the work on the top of the tell and in the new deep sounding, to grasp better the fluctuations in house durations from generation to generation, and can now contrast the relative fortunes of unburnt and burnt houses. We can say much more about the timing and tempo of the ending of the tell, and about the possible circumstances in which that took place.

Paired radiocarbon and stable carbon analyses have been carried out on aragonite shells and organic soft bodies of snails from the Chinese Loess Plateau in order to explore the possibility of using these kinds of samples as environmental and chronological indicators. Results show that the soft bodies exhibit 14C concentrations similar to those of plant leaves, indicating that carbon in the soft bodies is fixed from organic diets. The aragonite shells are depleted in 14C compared to the soft bodies due to ingestion of 14C-depleted carbonate. This depletion shows a consistent pattern across the Chinese Loess Plateau, implying a good potential for the snail shells to be applicable for 14C dating with a simple correction. The δ13C values measured for aragonite shells display a linear relationship with those obtained for the soft bodies with a constant offset. In addition, the carbon derived from organic diets accounts for more than 70% of the total shell carbon. This fact suggests that stable carbon isotope composition of aragonite shells mainly reflects that of organic diet, and could be used as a reliable indicator of paleodiet in the Chinese Loess Plateau.

For radiocarbon calibration, the arrow of time is pointing backwards but the entropy does not necessarily decrease in this direction…