Detonation of the first fission bomb at White Sands, New Mexico, on July 16, 1945, produced a tremendous neutron flux capable of creating tritium and radiocarbon byproducts. We sampled a 115-year-old pinyon (Pinus edulis) 10km east of the Trinity test site to determine 14C evidence of this event. The most likely mechanism for this enrichment in the 1945 tree ring would be fixation of 14CO2 produced at the blast site and carried with the fallout cloud over the pinyon site. Analysis of cellulose of the 1944 and 1945 rings shows δ13C values of −19.9 and −19.5, respectively, and 14C activity (fraction of modern uncorrected for δ13C) as 0.991 ± .005 and 0.991 ± .006, respectively. It is likely that the duration and/or concentration of the 14CO2 exposure was not sufficient to increase 14C activity expected for that year.

In 1991, a 14C ß-counting installation with four proportional CO2 gas counters was tested at the Modane underground laboratory, 1700 m below the summit of Pointe du Fréjus, reducing the muon flux to 4 muons per square meter and per day. With cosmic radiation attenuated by a factor of 2.106, the background level of the counters was reduced by 65 to 85% while its variability was reduced by a factor of 30–80 depending on the type of counter. The dating limit of these counters extends to well beyond 60,000 years.

The second home-made single stage accelerator mass spectrometer (SSAMS) system dedicated to radiocarbon (14C) measurements was built after the first SSAMS system was moved to Guangxi Normal University. With some improvements to the second SSAMS system, the performance has been improved. With the conditions of total ion energy of 200KeV, ions charge states of 1+ and helium as stripper gas, 14C measurements with precision of 0.5% and a background level of 0.5 pMC were achieved. Details of the system and the experimental performance are given here.

We present an alternative radiocarbon (14C) age-depth model using IntCal20 to calibrate new accelerator mass spectrometry (AMS) data applied to a Lake Baikal sediment core (VER99G12) in southern Siberia. 14C dating showed that the core extends to 31 ka. To take into account uncertainties in 14C age and sedimentation depth in the core, a new age-depth modeling routine, undatable, was used in this study. Undatable revealed that significant changes in sedimentation rate correspond to global climate events, either warm or cold, which periods are likely close to the timing of the occurrence of the Meltwater pulses (MWP) at 19 and 14 ka, and the Last glacial Maximum (LGM) at 21–20 ka. Since the Selenga River accounts for 50% of the total river inflow to Lake Baikal, we interpret that these changes in sedimentation rate could be signals of significant changes in Selenga River discharge to the lake, which is expected to be affected by global climate change. Based on pollen analysis, it is highly probable that the sudden influx of the Selenga River to Lake Baikal, particularly at 19 ka, was due to the thawing of permafrost water through the Selenga River, which had developed in the region. Total organic carbon content and mean grain size increases concurrent with sedimentation rate, suggesting river inflow increased available nutrients for biological activity. Our results indicate that hydrological changes corresponding to MWP events can be observed in continental areas of the Northern Hemisphere.

The following radiocarbon dates are a partial list of samples measured for a variety of projects and materials since January 1980. Chemical and counting procedures remain the same as indicated in R v 20, p 274-282.

This study focuses on the chronology of King Den’s reign, the fifth ruler of the 1st Egyptian dynasty. A series of radiocarbon (14C) dates were established on archaeological material from several tombs at the Abu Rawash site, near Cairo, which comprises a complex of 12 monumental mud-brick mastabas. Modeling the 14C results enables us to estimate the date of King’s accession and to link this to the beginning of the 3rd Dynasty, i.e., to Egyptian state’s structuration. Through the application of OxCal software, sets of 14C results obtained from the same archaeological context have been summarized and compared with the precise state of our knowledge on the historical duration of this reign. These results place King Den’s accession between 3104 and 2913 BCE (2σ), with the more likely date being 3011–2921 BCE (1σ). The modeled temporal density thus obtained is based both on new contextualized 14C dates and on an updated reading of the historical information on his reign. This is a dynamic result, which can be refined as soon as we have more data to integrate into the model. Above all, this resulting model becomes a crucial chronological point to better determine the beginning of the Egyptian Old Kingdom.

This research aims to contribute to our knowledge of the chronology of the main cultural entities of the Bronze Age in the Southern Urals. The objectives of this work include the verification of earlier conclusions regarding individual sites, expanding the date series for the key cultures with reliable dates, and creating reference series for the Bayesian modeling of key archaeological sites. Thirty-two samples were selected from reliable contexts. They reflect seven different cultural traditions of the 2nd millennium calBC (Sintashta, Srubnaya, Alakul, Fedorovka, Cherkaskul, Final Bronze Age1, Transition to Early Iron Age2). Collagen (human and domestic animal bones), charcoal, and wood samples were used for radiocarbon dating. Pairs of different-type samples (human bone – animal bone, animal bone – charcoal) were obtained for the same undisturbed burial and the building floor at the time of its abandonment. The data and the composition of δ15N and δ13C isotopes allow the new dates to be considered reliable. Furthermore, the new results do not conflict with the previously obtained accelerator mass spectrometry (AMS) dates. Determining boundary intervals for the main cultures of the Andronovo cultural community (Alakul and Fedorovka) resulted in statistically reliable conclusions on their relationship. The Alakul culture appeared earlier than the Fedorovka culture. The latter has a migratory origin in the Southern Urals. The two traditions have a long history of interaction, but the Alakul culture ending earlier. The series of dates for the Final Bronze Age, divided into two sub-periods, has been significantly expanded. Bayesian modeling of the chronology of the stratified settlement Sintashta II (Levoberezhnoe) made it possible to determine the intervals of the main phases of its history: 2004–1852 calBC (Sintashta culture) and 1410–1170 calBC (Final Bronze Age). Intermediate Cherkaskul phase is represented by a single date (1731–1541 cal BC).

Radiocarbon dates obtained since August 1969 are included in this report. The procedures followed and equipment used have been described previously (Radiocarbon, 1966, v. 8, p. 522-533).

The following radiocarbon measurements are a partial list of geologic samples dated since September 1975. The technique used is described in R, v 18, p 210-220. Dates are calculated using a 14C half-life of 5568 yr and errors are reported as one standard deviation. This includes only the counting errors on the sample, background and modern standard.

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 effects of different measurement conditions and sample preparation in liquid scintillation counting of benzene for 14C dating were tested. The goal of this work was to find the highest figure of merit through the variation of scintillation cocktail to benzene ratio, and measurement windows. Measurements were performed on 5ml of benzene plus increasing quantities of scintillation cocktail (7g of PPO and 0.5g of Me2POPOP in 1L of scintillation-grade toluene). Spectra of both background and standard were obtained and the counting windows selected for the highest figure of merit (Q). The best condition was 5ml of benzene plus 0.75ml of scintillation cocktail. This spectrum is compared with that of 1) pure toluene-14C plus cocktail, and 2) pure benzene-14C in which the equivalent amount of PPO and Me2POPOP present in 0.75ml of cocktail was dissolved. A correlation between the increase of the amount of cocktail and the broadening of the spectrum was observed. The effect of wrapping the upper part of the counting vial with aluminum foil to reduce background was also tested. A drastic background increment was observed in the low energy range, for unwrapped vials; the standard spectrum showed a broadening and a lower counting efficiency which reduced the figure of merit.

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.

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.

Measurements have continued with the same proportional counter system, pretreatment procedure, methane preparation and measurement, and calculation, as described previously (R, 1970, v 12, p 298–318). Uncertainties quoted are single standard deviations originating from standard, sample, background counting rates and half-life. No C13/C12 ratios were measured.

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.