We sampled individual growth rings from three ancient remnant bald cypress (Taxodium distichum) trees from a massive buried deposit at the mouth of the Altamaha River on the Georgia Coast to determine the best technique for radiocarbon (14C) dating pretreatment. The results of our comparison of traditional ABA pretreatment and holocellulose and α-cellulose fractions show no significant differences among the pretreatments (<1 sigma) thereby suggesting that ABA pretreatment will prove sufficient for the development of a high-resolution 14C tree-ring chronology based on these ancient bald cypresses which will indicate whether the U.S. Southeast is subject to a regional radiocarbon offset.

Human remains from the (late) Middle Paleolithic remain rare. Improving our understanding of their spatio-temporal distribution is essential for obtaining insights into human evolution and the dynamics between Neanderthals and early Anatomically Modern Humans (AMHs). We present the single-amino-acid radiocarbon dating and ancient DNA results from the only Neanderthal skeletal remains known in Slovakia (Šal’a I and Šal’a II). As they were found without archaeological context and in secondary deposition, recontextualization is important. By employing the hydroxyproline radiocarbon dating method, we were able to successfully counteract contamination issues and circumvent problems caused by highly degraded collagen. By contrast, DNA analysis did not detect any endogenous DNA at the limits of our resolution. We conclude that the radiocarbon ages of >44,800 BP (OxA-X-2731-16) and >45,100 (OxA-X-2731-15) firmly place the two individuals in the Middle Paleolithic, and before the arrival of AMHs to the region. Furthermore, indirect evidence based on morphology and possibly related faunal remains suggest ages younger than 100 ka. This time frame coincides with a period in which Neanderthal populations were highly dispersed in Europe, yet in decline.

The archaeological site of Tlatoani at Tlayacapan is located in the Mexican Highlands, in the present-day state of Morelos. The site is an extant settlement located at the top of the Tepoztlan mountain range, and has been occupied since the Late Preclassic period (AD 150–500). At the height of its occupation in the Epiclassic and Early Postclassic periods (AD 600–1150), Tlayacapan was situated on the top of the hill. The radiocarbon investigations reported herein revealed some further distinct findings, although no clear absolute chronology was demonstrated. A dog skull was found inside the oldest foundation stage, and dated between cal AD 646 and 765, the middle of the Epiclassic period. Human remains found in the first grave belonged to three individuals. A male skeleton was dated to AD 1158–1227. Fragments of an incomplete skeleton of a child and an incomplete skeleton of a second male were placed on top of the first male skeleton and were dated in the range AD 1030–1156. A fourth skeleton found nearby in the second grave gave a similar date of AD 1164–1253. These burials were in accordance with the Middle America cosmovisional system, where bodies were buried beneath the household space. It is evident from the 14C dates of the skeletons that the burial sites beneath the household space had been reused by exhuming and reburying skeletons that had been previously buried there. A comparison of dates on fractions of collagen and bioapatite of the same bones was possible. Two of the samples were in good agreement between these fractions, whereas the other three samples are close but just outside the 2σ range.

El Japón is a 16th century hamlet site in the marshlands of the southern Basin of Mexico in central Mesoamerica. Radiocarbon (14C) dating and OxCal modeling of human bone collagen (n = 11) identifies a range of burials at El Japón cemetery from 1550–1650 cal. CE. The refined chronology identifies use of this rural settlement well after the onset of colonial government-sponsored relocation of Indigenous people to larger settlements (congregaciones). Historically documented information in this work supports chronological modeling beyond stand-alone calibration. Stable isotopic study of bone samples demonstrates similar sources of dietary protein and carbohydrates. The similarity of carbon sources for bone apatite (bioapatite) and collagen offers security that both bone fractions are viable 14C dating opportunities. Recent extension of this work examines bioapatite 14C dates (n = 5) from the same bone samples when quality parameters are met—atomic carbon-nitrogen ratios of 3.2–3.3 and collagen yield of 10–20%. No significant difference is found between collagen and bioapatite dates of the same individuals (p = 0.17, Mann-Whitney U test). 14C dates from human bone samples in this primarily terrestrial dietary context can be successfully acquired from either collagen or bioapatite fractions.

During the last seven years, there has been a concerted effort in eastern Australia to obtain 14C ages from detrital shell samples of prograded sand barriers composed of beach ridges and chenier deposits (Cook and Polach, 1973; Cook and Mayo, 1977; Thom, Polach, and Bowman, 1978; Thom et al, 1981). These ages were used to establish the age sequence of deposition and rates of progradation. This date list is the result of work in two areas of the Gulf of Carpentaria, Queensland, Australia, where 57 shell samples were collected for 14C dating. For details of this research, see Rhodes et al (1980).

At the Intertropical Convergence Zone (ITCZ), the northern and southern Tradewinds converge, and this region is characterized by low atmospheric pressure and high precipitation. The climate in the Timor Sea is characterized by seasonal precipitation changes driven by meridional migrations of the ITCZ and the monsoonal front. The ITCZ shifts in response to changes in the thermal balance between the northern and southern hemispheres. Thus, reconstruction of paleo-precipitation in the Timor Sea is expected to reveal past changes in both regional and global climate, the latter through inference of the ITCZ position. To reconstruct paleo-precipitation in the Timor Sea, we performed extensive radiocarbon analysis on both planktonic foraminifera and total organic carbon (TOC), which is derived from terrestrial and marine sources. Increased precipitation enhances the fraction of relatively old, terrestrial carbon to the core site, which in turn increases the difference between the ages of TOC and planktonic foraminifera. Variations in radiocarbon ages reveal that during northern hemisphere cooling intervals such as Heinrich Stadial 1 and the Younger Dryas, the ITCZ was in a southern position, thus increasing precipitation in the Timor Sea. However, the Timor Sea was dryer during the Bølling–Allerød warming as the ITCZ shifted northward.

The Inner Mongolian Plateau lies along the northern limit reached by the East Asian summer monsoon. This geographic setting makes it especially sensitive to environmental change and an excellent site for understanding Quaternary East Asian monsoon variability. In this study we present new results of hydrogen isotopic compositions of fatty acids extracted from sediments, which were used to construct Holocene paleoprecipitation (or moisture) changes in Northern China. The hydrogen isotopic composition (D/H ratio) of n-acids in the sedimentary sequence of the Duoerji peat, Inner Mongolia, was determined with gas chromatography and mass spectrometry. Changes in the precipitation from middle Inner Mongolia are recorded by the D/H ratio of n-C20, n-C22, n-C24, n-C26, n-C28 acids (δD). From 10–9 ka, the relatively high δD values indicate reduced precipitation in the Early Holocene. Subsequently, increased precipitation is reflected by reduced δD values from 9–5.5 ka. After 5.5 ka, gradually increasing δD values record an overall decrease in precipitation. The precipitation trends established for the Duoerji sequence are consistent with other major paleoclimate proxies in the East Asian monsoon region, especially with a distinct Holocene optimum of increased monsoonal activity from 9–5.5 ka. The δD resulting paleo-precipitation record clearly shows that the Holocene climate in Northern China is basically controlled by the insolation changes.

We are observing a dramatic increase of CO2 in the atmosphere, unprecedented in the last several million years. Carbon isotopic ratios have been very useful in helping to untangle the respective roles of anthropogenic emissions and sources/sinks of CO2 in the oceans or terrestrial biosphere. However, this untangling has not been as simple as was often hoped. The isotope ratio signatures produced by emissions and removals that are present in atmospheric CO2 are always vigorously being erased by isotopic exchange with the oceans and terrestrial ecosystems, without there necessarily being any effect on total CO2. Especially in the last decades this pure isotopic exchange effect has led to gross errors that have clouded the public debate on climate change, obscuring mankind’s role. This paper traces my own struggle with the scientific and public sides of this issue, which I ran into from the start of my career in Groningen and throughout my years at NOAA. It is still relevant today.

Glassy microspherules, typically 200μm or less in diameter, are well documented from a variety of terrestrial and extraterrestrial sources (Baker, 1959, p 192–198; Glass, 1969; Rost, 1969; McKay, Greenwood & Morrison, 1970; Mueller & Hinsch, 1970; Cross, 1971; O'Keefe, 1980). To these we would add the formation of microspherules of similar habit when wood charcoal is burned in a combustion bomb (Barker, Burleigh & Meeks, 1969; Burleigh, 1973, 1974; Switsur, 1973; Switsur et al, 1974) as a first step in the chemical synthesis of samples for 14C age measurement. The glassy material of these spherules originates from fusion at the high temperatures reached during the combustion, of traces of alkali-metal minerals in the charcoal and silica bodies (phytoliths) within its microstructure. Other materials commonly burned, such as bone collagen, do not yield microspherules. The age and source of the charcoal are immaterial, though different species (and perhaps other woody plant materials) may be more-or-less productive of spherules. Here we give a brief summary of the characteristics of these glassy microspherules, based on optical and scanning electron microscopy and energy-dispersive x-ray analysis.

After an intercomparison age experiment carried out in the framework of the first MODIS (MOrtar Dating Inter-comparison Study) project, the results showed general agreement both between optically stimulated luminescence (OSL) dating laboratories and with radiocarbon (14C) dating results. As the needs for the selection of samples convenient for an inter-comparison are not the same between 14C and OSL, for the second running, it has been decided to choose two different sample sets, one to share between the radiocarbon labs and one for the OSL dating ones. The results obtained by applying different experimental protocols (multigrain and single grain techniques) and different statistical models (weighted mean, central age mode, average dose model, minimum age model and exponential exposure dose) are discussed in this work.

Huon pine is endemic to Tasmania. It has well-defined annual rings, may live for over 2000 years, and is particularly resistant to decay. Celery-top pine has similar characteristics and may live for 800 years. As part of a multi-disciplinary study of these trees and their habitat, a simple wood pretreatment method for isotope analysis is described. The solvent-acid-alkali-acid sequence yields a value of Δ14C = −16 ± 6‰ for AD 1941–45 Huon pine heartwood; Δ14C for extracts containing various proportions of post-AD 1955 carbon are also presented. Δ14C measurements on super-canopy and sub-canopy leaves from Celery-top pines are compared and used to place an upper limit of 10% on the amount of sub-canopy CO2 assimilated by sapling leaves, originating from decaying litter-mass. 14C ages from well-preserved logs illustrate the potential for a continuous Holocene chronology from 7400 years BP to the present. A 12,000-year-old Celery-top log has also been found.

The method of determining the biobased carbon content in liquid fuel samples is standardized, but different laboratories use different protocols during sample preparation and perform the measurements using different machines. The accelerator mass spectrometry (AMS) laboratories use different combustion, preparation, and graphitization methods for the graphite production for the spectrometric measurements. As a result, the intercomparison between the laboratories is inevitable to prove precision and accuracy and to demonstrate that the results are comparable. In this study, we present the results of an intercomparison campaign involving three 14C accelerator mass spectrometry laboratories. Five samples were used in the measurement campaign, including two biocomponents (fatty acid methyl ester, hydrotreated vegetable oil), one fossil component (fossil diesel), and two blends (mixtures of fossil and biocomponent with 90–10% mixing ratio) in the laboratories of CEDAD (Italy), ETH (Switzerland), and INTERACT (Hungary). The results presented by the laboratories are comparable, and all three laboratories could determine the biobased carbon content of the samples within 1% relative uncertainty, which is acceptable in the scientific, economic, and industrial fields for biocomponent determination.

The following list includes selected geologic and pollen dated samples measured since 1965. After moving to new laboratory quarters, we increased shielding to 470 g/cm2 on all sides and 660g/cm2 at the top. Background of our Houtermans-Oeschger-type counters filled with 700 mm Hg of acetylene is now:

The floating dendrochronological sequence of pine wood from Józefowo, N. Poland was expected to cover the ∼660 BC radiocarbon (14C) excursion. The sequence was radiocarbon dated using the OxCal wiggle matching procedure and the IntCal20 calibration curve. 14C concentrations were measured in one-year α-cellulose samples from around 660 BC. The published data on the ∼660 BC 14C excursion from Grabie, Poland were used to absolute date the Józefowo chronology with 1-year accuracy. The results confirm the occurrence of a rapid increase in Δ14C in 664/663 BC and its potential to be used as a fixing point for floating dendrochronological sequences.

The 14C dates given below are continued from our previous list (R, 1972, v 14, p 223–238), and results obtained mainly during 1971–2 are described. A 2.7L stainless steel counter and a 3.3L copper counter are used as previously, yielding background counting rates of 6.9 and 6.0 cpm, respectively, when filled with dead CO2 at ca 1.8 atm. Dates have been calculated on the basis of the 14C half-life of 5568 yr and 95% of NBS oxalic acid is modern standard. No correction has been made for any of the samples in this list.

The Xi-Sha Islands comprise 35 coral reefs, cays, and islets lying to the northwest of the South China Sea. Since Miocene time, > 1200m of bioherms developed on slowly subsiding granite-gneiss bed rock. These sediments provide evidence for sea-level changes and crustal movements in the South China Sea.

A single-stage accelerator mass spectrometer (GXNU-AMS) developed for radiocarbon and tritium measurements was installed and commissioned at Guangxi Normal University in 2017. After several years of operational and methodological upgrades, its performance has been continuously improved and applied in multidisciplinary fields. Currently, the measurement sensitivity for radiocarbon and tritium is 14C/12C ∼ (3.14 ± 0.05) ×10–15 and 3H/1H ∼ (1.23 ± 0.17)×10–16, respectively, and the measurement accuracy is ∼0.6%, which can meet the measurement requirements in the nuclear, earth, environmental and life science fields. This study presents the performance characteristics of GXNU-AMS and several interesting application studies.