Air sample collections over the western Pacific have continued since 1992 as a part of Center for Global Environmental Research, National Institute for Environmental Studies (CGER-NIES) global environmental monitoring program. The air samples collected on the Japan-Australia transect made it possible to trace the seasonal and secular 14CO2 variations, as well as an increasing trend of greenhouse gases over the western Pacific. A subset of CO2 samples from latitudes of 10–15°N and 23–28°S were chosen for accelerator mass spectrometry (AMS) 14C analysis using a NIES-TERRA AMS with a 0.3–0.4% precision. These 14CO2 records in maritime air show seasonal variations superimposed on normal exponential decreasing trends with a time constant of about 16 yr. The Δ14C values in the Northern Hemisphere are lower those in the Southern Hemisphere by 3–4 during 1994–2002. The Northern Hemisphere record shows relatively high seasonality (2.3 ± 1.5) as compared with the Southern Hemisphere (1.3 ± 1.2). The maximum values of seasonal cycles appear in late autumn and early winter in the Northern and Southern Hemispheres, respectively. Oscillations of 1–10 yr over the western Pacific are found to correlate possibly with the El Niño/Southern Oscillation (ENSO) events.

Subfossil trees with their annual rings constitute the most accurate and precise archive to calibrate the radiocarbon (14C) method. The Holocene part of the IntCal curve is based on tree-ring chronologies, absolutely dated by dendrochronological matching. For the Northern Hemisphere, the absolute curve starts at 12,325 cal BP. For the early part of the Younger Dryas (YD) climatic event (≈ 12,850–11,650 cal BP), there are only a few floating dendrochronological sequences, mainly from Switzerland and France. We present new 14C results from subfossil trees (Pinus sylvestris L.) collected from the Barbiers site (southeast French Alps). The dendrochronological series covers 416 years, corresponding to the onset of the YD period. In order to date our sequence, we matched it with the 14C record based on kauri trees from New Zealand. The Barbiers data were first averaged at the same decadal resolution as the kauri record. Statistical comparison of the different averaging options and matching techniques enables dating the Barbiers sequence to 13,008–12,594 ±10 cal BP, which thus includes the boundary between the Allerød and YD events. The new Barbiers record allows to calculate the 14C inter-hemispheric gradient (14C-IHG) during the period overlapping the kauri sequence. For the optimal dating option, the mean 14C-IHG is 37 yr with a standard deviation (SD) of 21 yr based on 43 decadal estimations (−6‰ with SD of 2‰). The 14C-IHG record exhibits minimal values, down to zero, between 12,960–12,840 cal BP. Excluding these minima leads to an average 14C-IHG of 45 yr with a SD of 14 yr based on 33 decadal values, in agreement with observations for the last two millennia. The Barbiers record suggests a 14C-IHG increase between the end of the Allerød period (IHG of 37 yr with SD of 14 yr) and the early part of the YD (IHG of 48 yr with SD of 14 yr), which is compatible with previously reported drop of deep-water convection in the North-Atlantic and the associated increase in wind-driven upwelling in the Southern Ocean.

The laboratory renewed operations in January, 1968 after a year's inactivity due to the absence of the head, who was on leave at the University of Bonn. Synthesized benzene continues as the dating medium, but various improvements have been made on the chemical method in order to increase capacity. Combustions are no longer carried out for normal materials. Instead, charcoal samples are used directly (after the usual pretreatment) and wood, plants, cloth, etc. are carbonized in a nitrogen atmosphere. Charring is a considerably more rapid procedure than combustion since it eliminates the CO2 collection, carbonate precipitation, and filtration steps. The charcoal then is reacted with molten lithium metal. Also, it was found that carbonates are attacked directly by hot lithium to produce carbides and the preliminary generation of CO2 gas is not indispensable. The carbide, cooled to room temperature, is reacted with old water (IVIC-317, Radiocarbon, 1967, v. 9, p. 240), the acetylene separated from hydrogen in a double liquid nitrogen-cooled trap, and benzene produced with a chromium activated silica-alumina catalyst.

The modern antiquities market uses radiocarbon (14C) dating to screen for forged objects. Although this fact shows the potential and power of the method, the circumstances where it is applied can be questionable and call for our attention. Here we present an outline of a call to radiocarbon laboratories for due diligence and best practice approaches to the analysis of antique objects requested by non-research clients.

The development and subsistence strategies adopted in ancient settlements are crucial to the understanding of long-term human–environmental interaction in the past. Here, we reassess the chronology of the ancient walled settlement of Sanjiao in the Hexi Corridor in northwestern China through accelerator mass spectrometry radiocarbon (AMS 14C) dating and explore the subsistence of the settlers inside through the identification of carbonized seeds and charcoal. In addition, high-resolution paleoclimate records in the Hexi Corridor and nearby regions are employed to explore the reason for the construction of Sanjiao. Our results show that Sanjiao was built around 828 cal BC and remained inhabited through 384–116 cal BC. This indicates Sanjiao is the earliest known walled settlement in the Hexi Corridor. Ancient people at Sanjiao consumed crops such as barley, broomcorn millet, and foxtail millet, and used wood from Tamarix chinensis, Tamarix, Salix, Picea, Hippophae, Betulaceae, and Poaceae as fuel. The construction date of Sanjiao correlates with climate deterioration and social upheavals in the Hexi Corridor, potentially suggesting a defensive purpose for the site.

Previous research in leeward Kohala, Hawai'i Island, has determined that the Leeward Kohala Field System (LKFS), a vast agricultural zone covering ∼60 km2, developed between the 14th and 18th centuries AD. Additional analyses have documented the establishment of traditional socioeconomic territories, known as ahupua'a, in tandem with the expansion of the field system. This article further refines the chronology of human settlement and socioeconomic development in leeward Kohala through the analysis of deposits associated with prehistoric residences. Based upon survey and excavation, we present a chronology for Hawaiian household transition and economic development in 2 study areas of leeward Kohala, spanning the field system to the coast. Forty-nine radiocarbon dates from short-lived plant materials and 5 230Th dates on corals from residential and ritual features are synthesized into 3 temporal periods, which allow for comparison of residential size, distribution, number, and associated faunal materials from archaeological deposits. Changes in household composition and economy are suggested to have developed in tandem with the establishment of individual ahupua'a and land divisions within them, and the further development of agricultural production.

The radiocarbon dates obtained since August, 1968, are reported here. Wood, charcoal, and peat samples are pretreated with dilute NaOH and dilute H3PO4 before conversion to the methane used as counting gas; marls and lake cores are treated with acid only. The reported dates have been calculated using 5568 years as the half-life of C14, 1950 as the reference year. Samples are run at least once in each of two 0.5 liter counters at 3 atm pressure for a minimum total of 15,000 counts. The standard deviation quoted includes only the 1σ of the counting statistics of background, sample, and standard counts.

The measurements reported have been carried out during the first half of 1967 in the Isotope Laboratory of the Institute of Geophysics and Planetary Physics as a continuation of the UCLA date lists I through VI. Samples were analyzed as CO2-gas at close to one atm in a 7.5 L proportional counter with 3 energy channels described earlier. Radiocarbon ages have been calculated for uniformity on the basis of a 5568-yr half-life as was recommended by the Sixth International C14 and H3 Dating Conference, June 1965, in Pullman, Washington. The standard for the contemporary biosphere remains as 95% of the count rate of NBS oxalic acid for radiocarbon laboratories. Background determinations have been based on CO2 obtained from marble. The error listed is always at least a 1σ statistical counting error. In critical cases C13/C12 isotope ratio measurements were made to correct the dates for fractionation. All samples were subjected to accepted NaOH and/or HCl pretreatments depending on the individual case as a minimum to exclude contamination. The annual curve for the atmospheric C14 content at China Lake, California, will be published in the next date list.

The Madaras profile found at the northernmost fringe of Bácska loess plateau is one of the thickest and best-developed last glacial loess sequences of Central Europe. The 10-m profile corresponds to a period between 29 and 12 b2k. To unravel feedback to small-scale centennial climatic fluctuations at our site, recorded in the Greenland ice and North Atlantic marine cores, construction of a reliable chronology is needed. Reliability is expressed in terms of best achievable chronological precision. Accuracy however is based on choosing the model best describing the sedimentological features of our profile. Five different age-depth models had constructed and compared relying on 15 14C dates using various statistical, probabilistic approaches to choose the model with the highest achievable precision. Accuracy was also evaluated using accumulation rates against stratigraphy. Models constructed using the computer program Bacon performed best in terms of achieving the best possible stratigraphic accuracy. Seven meters of the profile represents the period of the LGM. The average sedimentation time was 16.8 yr/cm with the highest confined to the period of the LGM. Calculated average sedimentation rates were 4 times higher than previously reported. The peak accumulation periods are dated to the nadir of the LGM.

Direct dating by simultaneous independent physical methods is of particular interest to prehistoric archaeology in central Europe. Radiocarbon and thermoluminescence measurements were made to date two tell settlements in the Carpathian Basin: the Late Neolithic site at Gorzsa (southeast Hungary) and the Eneolithic site of Vučedol (east Croatia, Yugoslavia). Samples from Gorzsa span from the Szakalhát to the Proto-Tiszapolgár periods, while most important cultural layers from the Vučedol site belong to the Baden, Kostolac, and Vučedol cultures. By including some of our earlier dates from the Tiszapolgár-Basatanya Copper Age site, a chronological framework, spanning the period from Late Neolithic to Early Bronze Age can be established. The quartz inclusion technique was used for TL dating of pottery. Beta and gamma dose rates were determined by TL dosimetry. Allowances were made for supralinearity, water content, and beta attenuation in quartz grains. The TL ages range from 1900 to 4300 BC and 3600 to 2900 BC, for the Gorzsa and Vučedol sites, respectively.

Since 2018, the radiocarbon laboratory of Lanzhou University has been equipped with a compact accelerator mass spectrometer—a 200-KV mini carbon dating system (MICADAS), together with an auto graphitization equipment (AGE III). The laboratory has for a long time prepared graphite targets for 14C dating of plant fossils, charcoal, bones, and bulk organic matter. Herein, we give an overview of the operating status and performance of the dating facility. The long-term measurements of the standard and blank samples indicated that the results for MICADAS in Lanzhou University were accurate and stable and of high sensitivity. Fifteen sets of organic materials collected from archaeological sites in northwest China were selected for an inter-comparison study involving the participation of four specialist laboratories. The 14C dating results for the homogenized archaeological samples from several of the laboratories showed a high degree of consensus. The long-term performance and inter-comparison data for MICADAS confirmed that the radiocarbon laboratory of Lanzhou University could provide stable and accurate 14C dating results. In this context, the 14C dating results for a number of key archaeological/environmental samples were validated.

A sample with a 14C concentration estimated to be greater than 30,000 Modern was inadvertently graphitized and measured in an AMS system. No measurable contamination of the cesium sputter ion source was observed. Simple cleaning procedures removed the contamination from the sample preparation system, with the exception of the reaction vessel in which the sample was graphitized. Sample cross-contamination factors were estimated for all of the preparation and measurement procedures.

The new 14C dating system of the Geological Survey of Finland consists of three CO2 proportional counters of conventional size, a liquid scintillation anticoincidence guard, and a passive shield of about 90-year-old iron. The counting room is an air-conditioned Faraday cage constructed of concrete with aggregate of crystalline Precambrian limestone. We apply pulse-shape discrimination that greatly improves the precision of our 14C analyses - the reduction of background is over 70%, while the modern count rate is reduced only by 15 to 20%. The purity of the counting gas is monitored by recording the cosmic muon pulse-height spectrum. At present, the dating limit for a two-day measurement is 57 ka. We summarize here the most significant results and aspects of pulse-shape discrimination

Extensive eruptions of alkalic basalt from low-elevation fissures and vents on the southern flank of the dormant volcano, Cerro Evermann, accompanied the most recent phase of volcanic activity on Socorro Island, and created the Lomas Coloradas, a broad, gently sloping terrain comprising the southern part of the island. We obtained 14C ages of 4690 ± 270 BP (5000–5700 cal BP) and 5040 ± 460 BP (5300–6300 cal BP) from lacustrine deposits that occur within volcanic sequences of the lower Lomas Coloradas. Apparently, the sediments accumulated within a topographic depression between two scoria cones shortly after they formed. The lacustrine environment was destroyed when the cones were breached by headward erosion of adjacent stream drainages. This was followed by the eruption of a thin basaltic flow from fissures near the base of the northernmost cone. The flow moved downslope for a short distance and into the drainages that presently bound the study area on the east and west. The flow postdates development of the present drainage system and may be very recent. Our 14C data, along with historical accounts of volcanic activity over the last century, including submarine eruptions that occurred a few km west of Socorro in early 1993, underscore the high risk for explosive volcanism in this region and the need for a detailed volcanic hazards plan and seismic monitoring.

Ca. 150 unequivocal 14C dates from the prehistoric cultures in the Russian Far East can be used to elucidate chrono-cultural boundaries in that region. Microblade technology started as early as ca. 20,000 bp, and continued to exist in the middle Amur River basin until ca. 10,500 bp, and in Primorye until ca. 7800 bp. The emergence of pottery-making in the lower Amur River basin goes back to ca. 13,300 bp. The transition from Upper Paleolithic to Neolithic took place during the time interval 13,300–7800 bp and pottery was widely spread in the Russian Far East by ca. 6700–8400 bp. The first evidence of shellfish collection is estimated to ca. 6400 bp at Peter the Great Gulf coast, Sea of Japan. The beginning of agriculture in Primorye, based on finding of both millet seeds (Setaria italica L.) and pollen of cultivated cereals (Cerealia), is 14C-dated to ca. 4200–3700 bp (ca. 1980–2900 cal BC). The Neolithic/Early Iron Age boundary was estimated at ca. 3100–3300 bp (1400–1600 cal BC) in the mainland Russian Far East, and to ca. 1800–2300 bp (400 cal BC–200 cal ad) on the Sakhalin and southern Kuril Islands.

This paper reports on the first chronological assessment of the Jewish Catacombs of the ancient Rome performed by accelerator mass spectrometry (AMS) dating of small-size charcoal fragments scattered in the mortar used for sealing off the graves in the Villa Torlonia Catacomb complex. The significance of the obtained 14C readings has been carefully evaluated by taking into consideration the known technologies of quicklime production during Roman and recent times. The new data are of great concern for providing evidence that the Jewish catacombs were used for burial since the first century AD, thus some two centuries prior to the period traditionally believed to be the starting point of burial in the Jewish catacombs of ancient Rome. Such a significant aging of the Jewish catacombs could result in a deep re-examination of the current understanding of the beginning and the evolution of the custom of catacomb burial in both Jewish and early Christian communities in Rome.

Extraneous carbon (Cex) added during chemical processing and isolation of black carbon (BC) in environmental matrices was quantified to assess its impact on compound specific radiocarbon analysis (CSRA). Extraneous carbon is added during the multiple steps of BC extraction, such as incomplete removal of solvents, and carbon bleed from the gas chromatographic and cation columns. We use 2 methods to evaluate the size and Δ14C values of Cex in BC in ocean sediments that require additional pretreatment using a cation column with the benzene polycarboxylic acid (BPCA) method. First, the direct method evaluates the size and Δ14C value of Cex directly from the process blank, generated by processing initially empty vials through the entire method identically to the treatment of a sample. Second, the indirect method quantifies Cex as the difference between processed and unprocessed (bulk) Δ14C values in a variety of modern and 14C-free or “dead” BC standards. Considering a suite of hypothetical marine sedimentary samples of various sizes and Δ14C values and BC Ring Trial standards, we compare both methods of corrections and find agreement between samples that are >50 μg C. Because Cex can profoundly influence the measured Δ14C value of compound specific samples, we strongly advocate the use of multiple types of process standards that match the sample size to assess Cex and investigate corrections throughout extensive sample processing.

Fewer than 20 radiocarbon dates have been obtained from Paleolithic sites on the Korean Peninsula. It is still unknown how and when Korean Middle Paleolithic stone industries developed, despite the handful of dates older than 40,000 BP obtained from some sites. A lower boundary for the Korean Upper Paleolithic of approximately 30,000 BP can be inferred from the few dates associated with stone blade industries. 14C dates associated with microlithic industries of 24,000 BP are considered too old in light of evidence from other areas of East Asia. Most such assemblages are post-Last Glacial Maximum in age. Improved understanding of the Korean Paleolithic sequence will depend ultimately on the further accumulation of 14C dates, as well as the application of alternative dating techniques and attention to the reconstruction of site formation process.

Radiocarbon is produced within minerals at the earth's surface (in situ production) by a number of spallation reactions. Its relatively short half-life of 5730 yr provides us with a unique cosmogenic nuclide tool for the measurement of rapid erosion rates (>10−3 cm yr−1) and events occurring over the past 25 kyr. At SUERC, we have designed and built a vacuum system to extract 14C from quartz which is based on a system developed at the University of Arizona. This system uses resistance heating of samples to a temperature of approximately 1100° in the presence of lithium metaborate (LiBO2) to dissolve the quartz and liberate any carbon present. During extraction, the carbon is oxidized to CO2 in an O2 atmosphere so that it may be collected cryogenically. The CO2 is subsequently purified and converted to graphite for accelerator mass spectrometry (AMS) measurement. One of the biggest problems in measuring in situ 14C is establishing a low and reproducible system blank and efficient extraction of the in situ 14C component. Here, we present initial data for 14C-free CO2, derived from geological carbonate and added to the vacuum system to determine the system blank. Shielded quartz samples (which should be 14C free) and a surface quartz sample routinely analyzed at the University of Arizona were also analyzed at SUERC, and the data compared with values derived from the University of Arizona system.

We present a novel application for radiocarbon dating by aging 4 scales from a single large adult lungfish (Neoceratodus forsteri) from the Burnett River, in Queensland, Australia. The relict fish species lack a solid crystalline otolith, which precludes the use of the otolith annuli as a reliable age indicator. Previous attempts to age lungfish using a number of techniques have had only limited success. We report on ages obtained from the dense lamellar bone of the scale, which were isolated from the organic layers that thicken and subsequently obscure the 14C signal. Using the characteristics of the bomb curve, 2 parameter von Bertanalffy growth functions were fit, providing an estimate of absolute age to be ∼65–70 yr. The information gleaned from this study will aid in assessing the population structure, and therefore management, of this vulnerable species.