In response to the increasing demand for 14C analysis of samples containing less than 25 μg C, ultra-small graphitization reactors with an internal volume of ∼0.8 mL were developed at NOSAMS. For samples containing 6 to 25 μg C, these reactors convert CO2 to graphitic carbon in approximately 30 min. Although we continue to refine reaction conditions to improve yield, the reactors produce graphite targets that are successfully measured by AMS. Graphite targets produced with the ultra-small reactors are measured by using the Cs sputter source on the CFAMS instrument at NOSAMS where beam current was proportional to sample mass. We investigated the contribution of blank carbon from the ultra-small reactors and estimate it to be 0.3 ± 0.1 μg C with an Fm value of 0.43 ± 0.3. We also describe equations for blank correction and propagation of error associated with this correction. With a few exceptions for samples in the range of 6 to 7 μg C, we show that corrected Fm values agree with expected Fm values within uncertainty for samples containing 6–100 μg C.

The Dangoor REsearch Accelerator Mass Spectrometer (D-REAMS) is a dedicated carbon-only AMS system, built by National Electrostatics Corporation (NEC). It is based on the 1.5SDH Pelletron, operating at 460 keV. The machine was installed at the Weizmann Institute of Science, Rehovot, Israel, in January–February 2013, and passed the acceptance test on March 2013. Since then, over 4500 samples have been successfully measured. Here, we present the results of an intercomparison experiment, done in collaboration with the Vienna Environmental Research Accelerator (VERA), and some typical operation parameters and measurement values of the new AMS system.

Compound-specific radiocarbon analysis of five fatty-acid biomarkers was conducted for marine sediments collected from the western North Pacific. The fatty acids (C12 to C34) showed a typical bimodal distribution pattern with two maxima at C16 and C26. Their carbon isotopic compositions ranged from −25.1‰ (C16) to −31.8‰ (C28), suggesting that they derived from terrestrial higher plants and marine organisms. A large variations of 14C ages were found among the fatty acids detected in the same sedimentary horizon of the core, ranging from 530 BP (C18) to 3250 BP (C28). The results of 14C analysis of fatty acids could be divided into two groups, i.e., lower molecular weight (LMW) fatty acids (C16, C18) derived from marine organisms and higher molecular weight (HMW) fatty acids (C24, C26, C28) derived from terrestrial higher plants. The HMW fatty acids showed older ages, ranging from 2550 BP (C24) to 3250 BP (C28), than LMW fatty acids (530 BP [C18] to 1,820 years BP [C16]). On the other hand, bulk-phase total organic matter (TOM) showed the age of 2260 BP that is between those two groups, suggesting that it was likely a mixture of organic matter derived from marine and terrestrial sources. The compound specific 14C ages and δ13C data of sedimentary fatty acids presented here could provide useful information to decipher the fate and transport process of terrestrial organic matter to marine sediments.

The 14C activity in rings from an oak tree grown in a suburb of Uppsala, Sweden has been studied for the period, AD 1938 to 1981. We compare the results with the atmospheric carbon dioxide records from Abisko, northern Sweden, where local or regional contamination from fossil-fuel combustion can be disregarded. We assess the influence from different chemical pretreatment procedures in use and compare HCl-NaOH-HCl treatment with cellulose extraction. We split each ring into two samples corresponding to early (spring) and late wood. A more refined partitioning has been applied to the years 1963 and 1964.

After 22 yr of the low-level liquid scintillation counting 14C laboratory at the Center for Nuclear Energy in Agriculture (CENA) at São Paulo University (USP), Piracicaba, Brazil, and several collaborative projects with Brazilian and international researchers from distinct scientific areas, the first 14C accelerator mass spectrometry (AMS) laboratory in Latin America was installed at the Physics Institute of the Universidade Federal Fluminense (UFF), Niterói, Brazil. A 250kV single stage accelerator produced by National Electrostatics Corporation began its operation in 2012. In this work, we compare measurements performed at the AMS Radiocarbon Laboratory at UFF (LAC-UFF) with those performed at CENA and the University of Georgia (UGAMS), Georgia, USA. All the results obtained from distinct inorganic and organic samples were in very good agreement.

Two Pinus aristata samples submitted by C W Ferguson were separated in different fractions, as was done earlier with Pinus silvestris L from Sweden, to yield different fractions for studies of the pretreatment. One sample in this new series consisted of heartwood and the second of sapwood.

The treatment performed in the radiocarbon laboratory involved an acid treatment by boiling, washings, an hydroxide treatment at 80°C, washings and, finally, another acid treatment before being dried before the combustion. The sodium-hydroxide treatment was repeated to yield at least two soluble and two insoluble fractions.

The treatment performed by the wood chemists involved extractions with ethanol-benzene and water. The remaining wood was dated but was also used for the production of holocellulose. The extractives were partitioned between ethyl ether and water and that from the older wood was used for the isolation of neutrals, acids, and phenols. In all, 19 fractions of these two wood samples were dated.

It is confirmed that a treatment for 30 min in sodium hydroxide at 80°C is not sufficient to remove the extractives from the heartwood or the sapwood. A treatment at 80°C overnight with 1 percent NaOH yielded a sample from the older wood with a 14C content in good agreement with the results predicted from the curve presented by Stuiver (1978). The final statistical uncertainty in the present investigation was ca 4‰. The younger wood yielded results indicating a lower activity than that given by Stuiver.

This paper presents an updated radiocarbon chronology of the earliest pottery sites in the Old World. Ceramic production originated in the Late Glacial period in several regions of East Asia—the Japanese Islands, the Russian Far East, and southern China—at approximately the same time, about 13,700–13,300 BP (about 17,200–14,900 cal BP).

Dendrochronological studies of bristlecone pine, Pinus longaeva, have produced a continuous tree-ring sequence back to 6700 BC for the White Mountains of California and to 3258 BC for east-central Nevada.

In this article, we present a set of radiocarbon measurements from Atar Haroa, a site that belongs to the early Iron IIA Negev Highlands settlement system in southern Israel. The results place activity at the site in the 9th century BCE, with a possibility that it was founded in the 10th century BCE, probably in the second half. The Atar Haroa measurements seem to indicate that the early Iron IIA phase in the ceramic typology of Israel lasted until the mid-9th century BCE—somewhat later than previously suggested. These new data shed light on several issues related to the history of southern Israel in the late 10th and 9th centuries BCE.

Deposits from the Minoan Santorini (Thera) eruption in the eastern Mediterranean region constitute the most important regional stratigraphic marker in the chronological perplexity of the 2nd millennium BCE. Extensive tsunami deposits were discovered in Crete at the Minoan archaeological site of Palaikastro, containing reworked volcanic Santorini ash. Hence, airborne deposition of volcanic ash, probably during the 1st (Plinian) eruption phase, preceded the tsunami, which was apparently generated during the 3rd or 4th phase of the eruption, based on evidence from Thera. Average radiocarbon dates (uncalibrated) of animal bones in the Palaikastro tsunami deposits along the coast (3350 ± 25 BP) and at the inland archaeological site (3352 ± 23 BP) are astoundingly similar to the average 14C date for the Minoan Santorini eruption at Akrotiri on Thera (3350 ± 10 BP). The wiggle-matched 14C date of the eruption in calendar years is 1627–1600 cal BCE. Late Minoan IA pottery is the youngest element in the Palaikastro tsunami deposits, fitting with the LM IA archaeological date for the Santorini eruption, conventionally linked at ~1500 BCE with Dynasty XVIII of the historical Egyptian chronology. The reasons for the discrepancy of 100–150 yr between 14C dating and Egyptian chronology for part of the 2nd millennium BCE are unknown. 14C dates from Tell el-Dabca in the eastern Nile Delta show that the 14C age of the Santorini eruption matches with 14C results from 18th Dynasty strata C3 and C2, thereby confirming grosso modo the conventional archaeo-historical correlations between the Aegean and Egypt. We propose that a dual dating system is used in parallel: (1) archaeological material-cultural correlations linked to Egyptian chronology; (2) 14C dating. Mixing of dates from the 2 systems may lead to erroneous archaeological and historical correlations. A “calibration curve” should be established between Egyptian chronology and 14C dating for the 2nd millennium BCE, which may also assist to resolve the cause of the discrepancy.

High freshwater inputs into Scottish sea lochs (fjords) combined with the restricted exchange between sea loch basin water and coastal Atlantic water masses are likely to result in reduced regional marine radiocarbon reservoir ages (R[t]) in these environments. To test this hypothesis, historical, museum-archived shells, collected live on known dates prior to AD 1950 from coastal locations in NW Scotland, were 14C dated to provide a means of determining R(t) and hence the regional deviation (ΔR) from the modeled global surface ocean reservoir age (R). The sea loch data, when combined with 14C dates from the Scottish west coast (Harkness 1983), yield a regional ΔR value of −26 ± 14 yr. The ΔR of sea loch (fjordic) and coastal waters of NW Scotland are statistically different (at a confidence level >95%) from the ΔR value of 17 ± 14 yr reported for UK coastal waters (Reimer 2005; data after Harkness 1983) and are in good agreement with the coastal ΔR value of −33 ± 93 yr reported by Reimer et al. (2002). Therefore, it is recommended that a regional ΔR correction of −26 ± 14 yr should be applied to modern (i.e. pre-bomb but not prehistoric) marine 14C dates from the NW coast of Scotland.

We present results of 14C dating of several tree-ring series from the Late Glacial and Early Holocene, analyzed at the Heidelberg University radiocarbon laboratory. Although these are floating series, they contribute high-resolution information about the variability of atmospheric 14C during those periods.

Using the model of Stacker and Wright (1996), we investigate the effect of a succession of ocean ventilation changes on the atmospheric concentration of radiocarbon, δ14Catm, the surface reservoir ages, the top-to-bottom age differences, and the calendar-14C age relationships in different regions of the ocean. The model includes a representation of the cycling of 14C through the atmosphere, the ocean and the land biosphere. Ocean ventilation changes are triggered by increasing rates of freshwater discharge into the North Atlantic, which are determined according to a simple feedback mechanism between the melting rates and the climatic state of the North Atlantic region. The results demonstrate that ventilation changes can cause δ14Catm fluctuations of 25%, surface reservoir age fluctuations of 100 yr in the Pacific (200 yr in the Atlantic) and top-to-bottom age variations of 500 yr in the Pacific (1000 yr in the Atlantic). We also show that 14C age estimates based on marine organisms that live in the near-surface region of the ocean and take up the signal of surface 14C can result in apparent age reversals if the assumption of a constant reservoir age is made.

Several approaches to dealing with the problem of mixed-age fossil assemblages are presented. These involve the use of amino-acid epimerization analysis (D-alloisoleucine/L-isoleucine ratio, or A/I) and are illustrated by deposits of land snail shells. This method requires only very small samples, so shells can be analyzed individually. Mixed-age deposits are indicated when variation in A/I among individual shells within the deposit exceeds the analytical error. Methods are presented for 1) estimating the true time of deposition of slightly-mixed-age assemblages based on bulk 14C dates and epimer analyses, 2) selection (for 14C analysis) of a set of individual shells that are uniform in age and represent the true time of deposition, and 3) estimating ages of individual shells within a mixed-age deposit based on their A/I ratios.

The radiocarbon dating of volcanic ash (tephra) deposits in New Zealand has been difficult on sites remote from the eruption, which contain either little carbon or degraded and contaminated charcoal. Although many studies of contamination removal from macroscopic charcoals from tephra sequences have been made, little attention has been paid to those containing no visible charcoal, because of the difficulty of obtaining sufficient carbon for radiometric dating. We report here experiments using accelerator mass spectrometry to establish a reliable method for dating a low-carbon aeolian and peat deposit containing a tephra horizon. Results so far demonstrate that improvements to existing chemical pretreatment methods are possible, and that dates obtained on oxidized fine-grained residues can approach the maximum age determined on good quality charred wood samples.

We measured radiocarbon in an annually-banded coral core collected from Con Dao Island, Vietnam, 90 km from the mouth of the Mekong River, and estimated the regional correction of the marine reservoir age (ΔR value). Twelve samples were continuously taken from the annual bands (AD 1949–1960) which were clearly identified under UV light (∼352 nm) as well as by X-radiography. The 14C content of the samples was determined using an accelerator mass spectrometer at the National Institute for Environmental Studies, Tsukuba, Japan. Results provide a Δ14C time series showing a relatively steady value of −48.6 ± 4.6‰ for the period of 1949–1955 and an abrupt increase starting from 1956 that indicates a quick response to the atmospheric testing of nuclear bombs. Using the prebomb 14C data, the ΔR value in the south of Vietnam is estimated to be −74 ± 39 yr.

ΔR results of known-age shells from the Solomon and Coral Seas and the northwest coast of New Ireland are presented. The results are too few to be conclusive but indicate that ΔR in this region is variable. An average ΔR value of 370 ± 25 yr is recorded for a range of shell species from Kavieng Harbor, New Ireland, and is primarily attributed to weak equatorial upwelling of depleted 14C due to seasonal current reversals. In contrast, values from the Solomon and Coral Seas are lower (average ΔR = 45 ± 19 yr). Higher ΔR values for some shellfish from these 2 seas is attributed to ingestion of 14C-depleted sediment by deposit-feeding species.

Bi-decade samples of dendrochronologically matched Irish Oak, measured with a precision of ca ± 20 years, covering the period 200 to 4000 BC are presented. The data are compared with the published data of Suess, de Jong, and Mook to provide a general calibration of the 14C time scale for this period. Although the dendrochronologic sequences presented are not absolutely tied to present, the best fit (based on 14C evidence) of the Belfast data to absolute chronologies, the error and evidence associated with such positioning is given. The intervals chosen for analysis were 20 years, reducing slightly the resolution of short-term variations when compared to 10-year intervals, which are sometimes measured. However, this calibration would suffice for most scientific purposes and certainly for the calendrical conversion of 14C dates derived from archaeologic samples.

Radiocarbon-age measurements reported here were made by the carbon dioxide gas-proportional counting method since conversion of the laboratory from the solid-carbon method. Assembly of the shield and construction of the glass system was accomplished during the summer of 1959. By January 1960, shield, anticoincidence ring, counters and electronics were set up and in operation. The first year of operation was occupied with calibration, comparison of dating with other C14 laboratories, and the repeating of many of the analyses previously made by the solid-carbon method. Special attention was given to dates open to question from an archaeologic point of view.

The open-air archaeological site at Krems-Hundssteig is a well-known Upper Paleolithic site located in Lower Austria. The site was discovered in the late 19th/early 20th centuries when a large number of archaeological remains were collected during the course of loess quarrying. Although no systematic excavation has ever been performed, Krems-Hundssteig has been described since its discovery as typical of the Aurignacian period in this region based on the numerous archaeological finds; accordingly, the culture has been named Kremsien by some authors. Surprisingly, the artifacts found in a recent excavation adjacent to this location showed solely Gravettian features, calling into question the original assignment to the Aurignacian. Although the earlier assignment was supported by a radiocarbon date of ∼35 kyr BP (Hahn 1977), new accelerator mass spectrometry (AMS) 14C dates proved that the recently excavated cultural layer originates from the Gravettian period. Older paleosols were also detected by sondage drillings at some depth below it.

The new results indicate that a large Aurignacian level and a substantial complex of Gravettian layers are present in this area. Therefore, it must be assumed that more than 1 cultural level was affected and destroyed by the historic loess quarrying, and that the assemblage of Krems-Hundssteig artifacts, traditionally ascribed to the Aurignacian, might be interspersed with Gravettian pieces.