Radiocarbon dating by accelerator mass spectrometry (AMS) of the shell bar section of Qaidam Basin, NE Tibetan Plateau, shows that this section was formed between ~39.7 and ~17.5 14C kyr BP and represented the highest paleolake development period since the Late Pleistocene. It was difficult to obtain reliable dates due to the low organic carbon content, which was formed mainly by authochtonous algae-bacteria (Zhang et al. 2007a). In order to improve the dating, 14C ages of both the alkali residual and acid-soluble components of the organic carbon were measured to check the consistency of the dating results. Total organic carbon (TOC) content and stable carbon isotopes (δ13Corg) might also be used as critical references for checking the reliability of dates. For example, in our study of the shell bar section from Qaidam Basin, we found that when the TOC content was higher than 0.15% and/or δ13Corg was lower than −23, the AMS dates were reliable. AMS dating of fossil shells demonstrated that they could provide valuable age information. The ages given by fossil shells are comparable to those of bulk carbonate from a similar sampling site, and are about 15~18 kyr older than the ages given by organic matter. Due to the U/Th dating requirements and open nature of the system, we concluded that U/Th dating results are unreliable and that this technique is unsuitable for dating halite deposits from Qaidam Basin.

Increasing concern with nuclear waste isolation technology is leading to additional studies of naturally occurring isotopes in ground water. Such studies provide information on 1) the use of radionuclides to estimate ground-water travel times and/or residence times. This information can he an extremely useful adjunct to conventional hydrologic data in developing the understanding of regional hydrology needed in the site selection process, and 2) the use of natural radionuclides as analogues to the behavior of radionuclides of concern in nuclear waste.

14C is one of the radionuclides that are produced to different degrees by neutron-induced reactions in all types of nuclear reactors. Part of the 14C created is continuously released into the surrounding environment during normal operation as airborne effluents in various chemical forms (such as CO2, CO and hydrocarbons) through the ventilation system of the plant. Because of the biological importance of carbon and the long half-life of 14C, it is of interest to measure the releases and their incorporation into living material. We report here on the 14C activity concentrations in annual tree rings and the air around two Swedish nuclear power plants, as well as the background 14C activity levels from two reference sites in southern Sweden from 1973–1996. We used both accelerator mass spectrometry (AMS) and decay counting in the investigation.

The following list comprises a selected number of measurements made up to November, 1965. Age calculations are based on a contemporary value equal to 95% of the activity of the NBS oxalic-acid standard, and on a half life for C14 of 5570 yr. Results are reported in years before 1950, and in the A.D./B.C. scale. Errors quoted include the standard deviations of the count rates for the unknown sample, the contemporary value, and the background. Because possible errors arising from isotopic fractionation in the plants, or from the de Vries effect, have not been included, calculated errors smaller than 100 yr have been increased by rounding to that figure as a minimum.

Four charcoal samples from loess key sites in Austria, Moravia, and western Ukraine were submitted to ABOx (acid-base oxidation) pretreatment to compare results with the classical ABA (acid-base-acid) method. For this purpose, charcoal samples already dated in Groningen laboratory were selected from 3 archaeological sites: Molodova V in western Ukraine (subunit 10–1, ∼32.6 ka BP), Willendorf II in Austria (unit C4, ∼32.1 ka BP and unit C8, ∼38.9 ka BP) and Vedrovice V in Moravia (unit 4, upper part of Bohunice soil, ∼39.5 ka BP). Each selected charcoal sample has been homogenized and divided into 3 subsamples, which were submitted to ABA in Groningen and to ABA and ABOx pretreatments in Oxford. The results show that the ABOx dates are older than the ABA dates. Nevertheless, down to ∼40 ka BP ABOx and Groningen ABA dates appear in good agreement within a time interval of ∼1 millennium at 1σ. However, Groningen ABA pretreatment produces older dates than the Oxford ABA pretreatment. Both Oxford ABOx and Groningen ABA pretreatments provide sets of dates in good agreement with the chronological background of each selected site.

This list includes most of the samples measured during 1974 and most of those measured previously but not published in the preceding date list (R, 1975, v 17, p 4–34.)

The Rehovot Radiocarbon Laboratory was established in 1968, as an extension of a low-level tritium laboratory, which has been in operation many years. Intended to be a supporting facility in geohydrological studies, the laboratory now offers general services in carbon dating.

Results of measurements for 3 years (1981–1983) of 14C activity of dissolved inorganic carbon (DIG) in water samples from the Korana River, as well as that of recent tufa and aquatic plants, showed that 14C concentration increases from karst spring to the estuary. A model describing the increase of 14C activity was developed assuming that the increase is due to the exchange of the dissolved CO2 in stream water with atmospheric CO2 and to dissolution of CO2 from the decay of organic material and root respiration. It is possible to distinguish these two contributions by measuring the δ13C values of DIC in water. As expected, our data show that the exchange process between atmospheric CO2 and DIC dominates at rapids and waterfalls, while biologic contribution is much higher in lakes and along the lowland flow of the Korana River. Agreement between the calculated and the measured activities supports the proposed mechanisms of chemical and isotopic exchanges in stream waters.

The usefulness of radiocarbon dates in archaeology greatly depends on both the stratigraphic relationship of the sample submitted and on the origin and homogeneity of the measured carbon. For very small samples, stratigraphic relationships can raise additional problems of movement. In chemically well-characterized materials, the best example being collagen, the carbon source can be reasonably well purified. Many samples, however, survive as a complex mixture of high molecular weight polyphenolic materials, with properties between charcoals, humic acids, and lignins. Charred bone, eg, which rarely contains useful quantities of amino acids, and charred seeds, as well as ‘charcoal,’ frequently come into this category. For such samples, the likelihood of contamination by percolating soil humics is high. It is often possible to extract chemically different fractions and to compare the dates obtained. A less exact comparison can also be made for different samples from the same context. The results suggest that ‘humic’ acid dates can be reliable in a surprisingly frequent number of situations, and that where direct comparison is possible, the reliability can be individually assessed.

Radiocarbon concentration measurements in tree rings from Upper Silesia indicate significantly lower 14C concentration as compared to the concentrations occurring in “clean air” areas. This phenomenon is known as the Suess effect and is caused by contamination with inactive carbon that originates from fossil fuels combustion. This effect is observed in large urban and industrial areas. Samples for the measurements presented in the paper were collected in some of the largest cities in Upper Silesia: Gliwice, Ruda Śląska, and Chorzów. The samples were annual tree rings (Populus nigra, Pinus silvestris) covering years 1965–1992 and the atmospheric CO2 collected weekly between December 1994 and December 1995.

An age-depth model for laminated sediments of Lake Soppensee is constructed using radiocarbon ages of macrofossils and a depositional model of the OxCal v 4.1 program with the updated IntCal09 data set. The resulting calendar chronology is compared with the varve chronology that was built for this record in a previous study (Hajdas 1993); there is a very good agreement between the 2 approaches. This illustrates the potential of high-resolution 14C dating for construction of reliable, high-resolution calendar timescales for sedimentary records. Based on the age-depth model of this study, the Vasset/Killian tephra found in sediment of Soppensee dates to a calendar age of 9291–9412 cal BP (2-σ range) while the Lachersee tephra dates to 12,735–12,871 cal BP (2-σ range). Precise dating of the Late Glacial boundaries is possible with this chronology but requires more precise correlation between proxies and records than typically practiced.

This article discusses 18 accelerator mass spectrometry (AMS) radiocarbon dates from the peat bog sites Sakhtysh 2a, Ozerki 5, and Ozerki 17 in the Upper Volga region. The aim is to contribute to a better understanding of the emergence and dispersal of early ceramic traditions in northern Eurasia and their connection to the Baltic. With 1 exception, all dates were obtained from charred residue adhering to the sherd. A possible reservoir effect was tested on 1 piece of pottery from Sakhtysh 2a by taking 1 sample from charred residue, and another sample from plant fiber remains. Although a reservoir effect was able to be ruled out in this particular case, 4 other dates from Sakhtysh 2a and Ozerki 5 seem too old on typological grounds and might have been affected by freshwater reservoir effects. Considering all other reliable dates, the Early Neolithic Upper Volga culture, and with it the adoption of ceramics, in the forest zone of European Russia started around 6000 cal BC.

The Middle Upper Palaeolithic (MUP) in eastern Central Europe (ECE) comprises three variants of Gravettian culture: Early Gravettian, Pavlovian, and Late Gravettian. While Early Gravettian and Pavlovian are merely located in Lower Austria and Moravia, the Late Gravettian occupations occurred over the entire territory of ECE. Compared to the number of sites the radiocarbon dating and the absolute chronology of the Late Gravettian is rather poor. The results presented here bring a new set of radiocarbon (14C) dates for the Late Gravettian period in ECE and propose that this period began and ended earlier than previously suggested.

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).

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.

High-resolution sediment chronologies with the best possible time control are essential for comparing palaeoecological studies with independent high-precision climatic, archaeological or historic data in order to disentangle causes and effects of past environmental, ecological and societal change. We present two varved lake sediment sequences from Moossee and Burgäschisee (Swiss Plateau) that have chronologies developed with Bayesian models and radiocarbon (14C) dating of terrestrial plant macrofossils extracted from sediment samples with constant age ranges. We illustrate the potential of high-resolution 14C dating for the construction of robust, high-precision sediment chronologies. The mean 2σ age uncertainties were reduced to±19 cal yr for Moossee and to±54 cal yr for Burgäschisee over the entire period of 3000 cal yr, while 2σ uncertainties of only±13 cal yr and±18 cal yr respectively, were achieved for shorter time intervals. These precisions are better than or comparable to those of previous varve studies. Our results imply that a sophisticated subsampling strategy and a careful selection of short-lived and well-defined terrestrial plant remains are crucial to avoid outlying 14C ages. A direct linkage between palaeoeological studies with dendrochronologically dated, local archaeological sites as well as a precise comparison with high-resolution climate proxy data have become feasible.

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.

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 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.