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ABSTRACTIn the frame of the IAEA-CRP (Coordinated Research Projects): Enhancing Nuclear Analytical Techniques to Meet the Needs of Forensic Sciences, an intercomparison exercise was organized between three AMS laboratories. Aim of the program is to promote the use of nuclear and accelerator-based techniques in routine forensics practice. In this view, one of the key points is the assessment of the precision and accuracy levels achievable on material of forensic interest. We review the general structure and status of the project, with emphasis on results obtained in the analysis of wines of different grape varieties and grounded coffee beans from different locations such as Brazil, Spain, and Italy. The three laboratories processed the samples according to different chemical protocols and performed the 14C measurements using different systems: MICADAS in Zurich and Debrecen and a HVEE 4130HC 3 MV Tandetron in Lecce. Within the quoted uncertainty, the results showed good reproducibility, indicating that uncertainty level of the order of 0.3% are achieved by AMS on a single sample while multiple sample analyses results in precision down to 0.1–0.2%. The measured 14C concentrations on coffee and wine samples resulted to be consistent with atmospheric 14C levels in the growing years.

ABSTRACTThe application of accelerator mass spectrometry radiocarbon (AMS 14C) dating in forensics is made possible by the use of the large excursion of the 14C concentration in the post-WWII terrestrial atmosphere due to nuclear testing as a reference curve for data calibration. By this approach high-precision analyses are possible on samples younger than ∼70 years. Nevertheless, the routine, widespread application of the method in the practice of forensics still appears to be limited by different issues due to possible complex interpretation of the results. We present the results of an intercomparison exercise carried out in the framework of an International Atomic Energy Agency (IAEA) CRP-Coordinated Research Project between three AMS laboratories in Italy, Hungary, and Switzerland. Bone and ivory samples were selected with ages spanning from background (>50 ka) to 2018. The results obtained allow us to assess the high degree of reproducibility of the results and the remarkable consistency of the experimental determinations.

ABSTRACTAnnually resolved radiocarbon (14C) measurements on tree rings led to the discovery of abrupt variations in 14C production attributed to large solar flares. We present new results of annual and subannual 14C fluctuations in tree rings from a middle-latitude sequoia (California) and a high-latitude pine (Finland), analyzed for the period 1030–1080 CE, to trace a possible impact of the Crab supernova explosion, occurring during the Oort minimum of solar activity. Our results indicate an increase of Δ14C around 1054/55 CE, which we estimate is higher in magnitude than the cyclic variability due to solar activity at a 2σ significance level. The net signal appears to be synchronized in the studied locations. Several sources of this event are possible including γ-rays from the Crab supernova, an unusually weak solar minimum or a solar energetic particle incident. More data are needed to provide more insight into the origin of this 14C event.

ABSTRACTToday, accelerator mass spectrometry (AMS) technology enables us to carry out very precise measurements of radiocarbon (14C). Unfortunately, due to fluctuations in the 14C calibration curve, the resulting calibrated time intervals vary from decades up to centuries in calibrated age. Within a time scale of several decades, we can find several time intervals on the 14C calibration curve which correspond with periods of rapid increases in atmospheric 14CO2activity. Some of these “high slope” parts of the calibration curve could be used for fine time resolution for radiocarbon dating of individual samples. Nevertheless, there are certain limitations owing to the properties of the samples measured. We have prepared a time-resolution curve for the 14C dating method, applying calibration curve IntCal13 and assuming an uncertainty of 14C analyses ±15 yr BP (for recent samples). Our curve of the time resolution covers the last 50 ka. We found several time intervals with time resolution below 50 yr BP for the last 3 ka. Several time intervals which can enable substantially better time resolution compared to neighboring parts of the calibration curve were also found for periods older than 3 ka.

AbstractWe performed a new series of measurements on samples that were part of early measurements on radiocarbon (14C) dating made in 1948–1949. Our results show generally good agreement to the data published in 1949–1951, despite vast changes in technology, with only two exceptions where there was a discrepancy in the original studies. Our new measurements give calibrated ages that overlap with the known ages. We dated several samples at four different laboratories, and so we were also able to make a small intercomparison at the same time. In addition, new measurements on samples from other Egyptian materials used by Libby and co-workers were made at UC Irvine. Samples of tree rings used in the original studies (from Broken Flute Cave and Centennial Stump) were obtained from the University of Arizona Laboratory of Tree-Ring Research archive and remeasured. New data were compared to the original studies and other records.

Abstract—We report on studies of the concentrations of cosmogenic nuclides in the magnetic fraction of cosmic dust particles recovered from the South Pole Water Well (SPWW) and from Greenland. Our results confirm that cosmic dust material from these locations contains measurable amounts of cosmogenic nuclides. The Antarctic particles (and possibly those from Greenland as well) also contain minor amounts of solar Ne. Concentrations of cosmogenic nuclides are consistent with irradiation of this material as small objects in space, with exposure ages similar to the expected Poynting‐Robertson (P‐R) lifetimes of 50–200 kyr for particles 25–100 μm in size.

Abstract—We have analyzed Shişr 033, a CR chondrite from the Omani desert, using several different analytical techniques designed to study the degree of terrestrial alteration of this meteorite and also its petrologic classification. Bulk chemical analyses (including organic carbon and mean total H2O content) are consistent with a CR classification. Additionally, oxygen isotope analysis on a bulk sample indicates that Shişr 033 is of type CR2. Amino acid analysis using liquid chromatography with UV fluorescence detection (HPLC‐FD) and liquid chromatography‐time of flight‐mass spectrometry (LC‐ToF‐MS) show that the absolute and the relative amino acid content of Shişr 033 is distinct from other carbonaceous chondrites. Oxygen isotope analysis of a phyllosilicate‐rich dark inclusion shows that this inclusion is closer to CV3 or CO3 chondrites. The effects of terrestrial weathering in Shişr 033 are evident from the dark inclusion carbon isotopic data, bulk chemistry (through the elevated concentrations of Sr and Ba), and amino acid data, which suggests extensive amino acid contamination of the meteorite from the fall site soil. Nevertheless, Shişr 033 contains a small fraction of indigenous components, as indicated by the presence of the extraterrestrial amino acid α‐aminoisobutyric acid (AIB) that was not detected in the Shişr soils. Finally, the terrestrial age of Shişr 033 was determined and is discussed in the context of high levels of contamination.

Abstract—We report concentrations of cosmogenic 10Be, 26Al, 36Cl, and 41Ca in the metal phase of 26 ordinary chondrites from Frontier Mountain (FRO), Antarctica, as well as cosmogenic 14C in eight and noble gases in four bulk samples. Thirteen out of 14 selected H chondrites belong to two previously identified pairing groups, FRO 90001 and FRO 90174, with terrestrial ages of ˜40 and ˜100 kyr, respectively. The FRO 90174 shower is a heterogeneous H3–6 chondrite breccia that probably includes more than 300 individual fragments, explaining the high H/L chondrite ratio (3.8) at Frontier Mountain. The geographic distribution of 19 fragments of this shower constrains ice fluctuations over the past 50–100 kyr to less than ˜40 m, supporting the stability of the meteorite trap over the last glacial cycle. The second H‐chondrite pairing group, FRO 90001, is much smaller and its geographic distribution is mainly controlled by wind‐transport. Most L‐chondrites are younger than 50 kyr, except for the FRO 93009/01172 pair, which has a terrestrial age of ˜500 kyr. These two old L chondrites represent the only surviving members of a large shower with a similar preatmospheric radius (˜80 cm) as the FRO 90174 shower. The find locations of these two paired L‐chondrite fragments on opposite sides of Frontier Mountain confirm the general glaciological model in which the two ice flows passing both ends of the mountain are derived from the same source area on the plateau. The 50 FRO meteorites analyzed so far represent 21 different falls. The terrestrial ages range from 6 kyr to 500 kyr, supporting the earlier proposed concentration mechanism.

Abstract—Fifty‐four fragments of ordinary chondrites from 50 finds representing all searched areas in central Oman and all weathering stages were selected to compare the physical, chemical, and mineralogical effect of terrestrial weathering with 14C terrestrial ages. 14C ages range from 2.0 to >49 kyr with a median value of 17.9 kyr. The peak of the age range, which is between 10–20 kyr, falls in an arid climate period. A comparison of the chemical composition of Omani chondrites with literature data for unweathered H and L chondrites demonstrates a strong enrichment in Sr and Ba, and depletion in S during weathering. Water contents in H chondrites increase with terrestrial age, whereas L chondrites show a rapid initial increase followed by nearly constant water content. Correlating Sr, Ba, and H2O with age indicates two absorption trends: i) an initial alteration within the first 20 kyr dominated by H2O uptake, mainly reflecting Fe‐Ni metal alteration, and ii) a second Ba‐and Sr‐dominated stage correlated with slower and less systematic weathering of troilite that starts after H2O reaches −2 wt%. Sulfur released from troilite partly combines with Ba and Sr to form sulfate minerals. Other parameters correlated with 14C age are degree of weathering, color of powdered meteorites, and the Ni/Fe ratio. Chemical analyses of 145 soils show a high degree of homogeneity over the entire interior Oman Desert, indicating large‐scale mixing by wind. Soil samples collected from beneath meteorite finds typically are enriched in Ni and Co, confirming mobilization from the meteorites. High Cr and Ni concentrations in reference soil samples, which decrease from NE to SW, are due to detrital material from ultramafic rocks of the Oman Mountains.

Abstract—We measured the concentrations of noble gases in 32 ordinary chondrites from the Dar al Gani (DaG) region, Libya, as well as concentrations of the cosmogenic radionuclides 14C, 10Be, 26Al, 36Cl, and 41Ca in 18 of these samples. Although the trapped noble gases in five DaG samples show ratios typical of solar or planetary gases, in all other DaG samples, they are dominated by atmospheric contamination, which increases with the degree of weathering. Cosmic ray exposure (CRE) ages of DaG chondrites range from ˜1 Myr to 53 Myr. The CRE age distribution of 10 DaG L chondrites shows a cluster around 40 Myr due to four members of a large L6 chondrite shower. The CRE age distribution of 19 DaG H chondrites shows only three ages coinciding with the main H chondrite peak at ˜7 Myr, while seven ages are <5 Myr. Two of these H chondrites with short CRE ages (DaG 904 and 908) show evidence of a complex exposure history. Five of the H chondrites show evidence of high shielding conditions, including low 22Ne/21Ne ratios and large contributions of neutron‐capture 36Cl and 41Ca. These samples represent fragments of two or more large pre‐atmospheric objects, which supports the hypothesis that the high H/L chondrite ratio at DaG is due to one or more large unrecognized showers.

Abstract—The compositionally typical H5 chondrite St‐Robert has an exposure age, 7.8 Ma, indistinguishable from that of the main cluster of H chondrites. Small values of the cosmogenic 22Ne/21Ne ratio in interior samples imply a pre‐atmospheric radius on the order of 40 cm. Sample depths based on tracks and the production rates of Bhattacharya et al.(1973) range from 6 to ∼40 cm and are generally larger than depths estimated from published 60Co activities, perhaps because the track production rates adopted are too high. Depth profiles of the production rates of 14C, 36Cl, 26Al, 10Be, and 21Ne in stony material show increases with depth and reach levels 5% to 15% higher than expected from modeling calculations. The maximum concentrations in St‐Robert are, however, generally comparable to those measured for the L5 chondrite, Knyahinya, whose pre‐atmospheric radius of ∼45 cm is thought to lead to the maximum possible production rates in chondrites. We infer that the pre‐atmospheric radius of St‐Robert was within 5 cm of the value that supports maximum production rates (i.e., 45 ± 5 cm). This radius corresponds to a pre‐atmospheric mass of (1.3 ± 0.4) × 103kg.

Abstract—We measured the concentrations of the cosmogenic radionuclides 14C (half‐life = 5.73 × 103years) in the bulk and of 10Be (1.5 × 106years), 26Al (7.05 × 105years), 36C1 (3.01 × 105years) and the light noble gases in metal and stone fractions of the Chinguetti meteorite to investigate the controversial claim that the 4.5 kg mesosiderite is part of a much larger mass in the Mauritanian desert. Based on the 36C1‐36Ar, 10Be‐21Ne and 26Al‐21Ne pairs in the metal fraction, we derive an average cosmic‐ray exposure age of 66 ± 7 Ma. Chinguetti is now the third out of 20 mesosiderites with an exposure age between 60 and 70 Ma. This may be the first hint of a major impact on the parent body of the mesosiderites, which show ages ranging from 10 to 300 Ma (Terribilini et al., 2000). From the 14C‐10Be pair we derive a terrestrial age of 18 ± 1 ka, which seems too recent to be consistent with the original description of the main mass having a heavily wind‐eroded base, overhung by the upper part of the meteorite. Finally, from the radionuclide concentrations in combination with Monte‐Carlo based calculations, we conclude that our sample of Chinguetti was irradiated at a depth of ∼15 cm in an object not larger than 80 cm in radius. This is the most compelling evidence against the reports that the Chinguetti mesosiderite is a small fragment of a mass 100 m long and 40 m high.

Abstract—We measured the concentrations of 10Be, 26Al, 36Cl, 41Ca and 14C in the metal and/or stone fractions of 27 Antarctic chondrites from Frontier Mountain (FRO), including two large H‐chondrite showers. To estimate the pre‐atmospheric size of the two showers, we determined the contribution of neutron‐capture produced 36Cl (half‐life = 3.01 times 105years) and 41Ca (1.04 times 105years) in the stone fraction. The measured activities of neutron‐capture 36Cl and 41Ca, as well as spallation produced 10Be and 26Al, were compared with Monte Carlo‐based model calculations. The largest shower, FRO 90174, includes eight fragments with an average terrestrial age of (100 ± 30) × 103years; the neutron‐capture saturation activities extend to 27 dpm/kg stone for 36Cl and 19 dpm/kg stone for 41Ca. The concentrations of spallation produced 10Be, 26Al and 36Cl constrain the radius (R) to 80–100 cm, while the neutron‐capture 41Ca activities indicate that the samples originated from the outer 25 cm. With a pre‐atmospheric radius of 80–100 cm, FRO 90174 is among the largest of the Antarctic stony meteorites. The large pre‐atmospheric size supports our hypothesis that at least 50 of the ∼150 classified H5/H6‐chondrites from the Frontier Mountain stranding area belong to this single fall; this hypothesis does not entirely account for the high H/L ratio at Frontier Mountain. The smaller shower, FRO 90001, includes four fragments with an average terrestrial age of (40 ± 10) × 103years; they contain small contributions of neutron‐capture 36Cl, but no excess of 41Ca. FRO 90001 experienced a complex exposure history with high shielding conditions in the first stage (150 < R< 300 cm) and much lower shielding in the second stage (R< 30 cm), the latter starting ∼1.0 million years (Ma) ago. Based on the measured 10Be/21Ne and 26Al/21Ne ratios, the cosmic‐ray exposure ages of the two showers are 7.2 ± 0.5 Ma for FRO 90174 and 8 ± 1 Ma for FRO 90001. These ages coincide with the well‐established H‐chondrite peak and corroborate the observation that the exposure age distribution of FRO H‐chondrites is similar to that of non‐Antarctic falls. In addition, we found that corrections for neutron‐capture 36Ar (from decay of 36Cl) result in concordant 21Ne and 38Ar exposure ages.

The methane emissions from the Hungarian Pannonian Basin are not well qualified, due to a lack of measurements of CH4mole fraction and δ13CCH4in the air. This study reports methane measurements in air samples from Hungary, placing them in the context of regional and global background data, to investigate the inputs to the methane burden in Central Europe. CH4mole fraction and δ13CCH4from the Hungarian tall tower station, Hegyhátsál, and additional data from Mace Head (Ireland) and Zeppelin (Svalbard) are used with back trajectory modeling to identify central European source areas and their seasonal variation between the summer vegetation and winter heating periods. Methane measurements in air masses sampled in the European interior, have significantly higher maxima and seasonal amplitudes than at the Mace Head and Zeppelin European background sites. The mean CH4mole fraction value is about 80 ppb higher than the comparable marine background, and values above 2,000 ppb were frequently observed between February 2013 and December 2015. The mean δ13CCH4value −47.5 ± 0.3‰ (2σ) was comparable to values at all three monitoring sites, but specific pollution events were detected at Hegyhátsál. Concentration weighted trajectory modeling, meteorological parameters, stable carbon isotopic composition (δ13CCH4), and Miller‐Tans analysis show that the main factors influencing CH4at the Hegyhátsál, apart from diurnal and seasonal changes in the planetary boundary layer, are emissions from residential heating and industrial CH4emissions during the winter. The main factors influencing local CH4values at Hegyhátsál (HUN) are local meteorology, and seasonal anthropogenic emissions related to heatingThe HUN station is valuable for monitoring local and regional methane emissions and tracking source inputsCH4increments and isotopic seasonality in air at the Hungarian continental background site are comparable to other European regional sites The main factors influencing local CH4values at Hegyhátsál (HUN) are local meteorology, and seasonal anthropogenic emissions related to heating The HUN station is valuable for monitoring local and regional methane emissions and tracking source inputs CH4increments and isotopic seasonality in air at the Hungarian continental background site are comparable to other European regional sites

Abstract—The Peekskill H6 meteorite fell on 1992 October 9. We report extensive measurements of cosmic‐ray produced stable nuclides of He, Ne, and Ar, of the radionuclides 22Na, 60Co, 14C, 36Cl, 26Al, and 10Be, and of cosmic‐ray track densities. After correction for shielding viathe 22Ne/21Ne ratio, the concentrations of cosmic‐ray produced 3He, 21Ne and 38Ar give an average exposure age of 25 Ma, which is considered to be a lower limit on the true value. The 10Be/21Ne age is 32 Ma and falls onto a peak in the H‐chondrite exposure age distribution. The activities of 26Al, 14C, 36Cl, and 10Be are all close to the maximum values expected for H‐chondrites. Together with cosmic‐ray track densities and the 22Ne/21Ne ratio, these radionuclide data place the samples at a depth >20 cm in a meteoroid with a radius >40 cm. In contrast, the 60Co activity requires a near‐surface location and/or a much smaller body. Calculations show that a flattened geometry for the Peekskill meteoroid does not explain the observations in the context of a one‐stage irradiation. A two‐stage model can account for the data. We estimate an upper bound of 70 cm on the radius of the earlier stage of irradiation and conclude that Peekskill's radius was <70 cm when it entered the Earth's atmosphere. This size limit is somewhat smaller than the dynamic determinations (Brown et al., 1994).

Keratinous horn sheaths of the extinct Harrington's mountain goat, Oreamnos harringtoni, were recovered at or near the surface of dry caves of the Grand Canyon, Arizona. Twenty-three separate specimens from two caves were dated nondestructively by the tandem accelerator mass spectrometer (TAMS). Both the TAMS and the conventional dates indicate that Harrington's mountain goat occupied the Grand Canyon for at least 19,000 years prior to becoming extinct by 11,160 ± 125 radiocarbon years before present. The youngest average radiocarbon dates on Shasta ground sloths, Nothrotheriops shastensis, from the region are not significantly younger than those on extinct mountain goats. Rather than sequential extinction with Harrington's mountain goat disappearing from the Grand Canyon before the ground sloths, as one might predict in view of evidence of climatic warming at the time, the losses were concurrent. Both extinctions coincide with the regional arrival of Clovis hunters.

The compounds are obtained by reacting the metal carbonyl anion with the appropriate 1,2-dichloro olefin. Similar compounds are not isolated following treatment of cobalt carbonyls with . The new bridged complex is described.

The annual 14C data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle (SEP) events in the past. Signatures of extreme SEP events have been reported in 774/775 CE, 992/993 CE, and ∼660 BCE. Here, we report another rapid increase of 14C concentration in tree rings from California, Switzerland, and Finland around 5410 BCE. These 14C data series show a significant increase of ∼6‰ in 5411–5410 BCE. The signature of 14C variation is very similar to the confirmed three SEP events and points to an extreme short‐term flux of cosmic ray radiation into the atmosphere. The rapid 14C increase in 5411/5410 BCE rings occurred during a period of high solar activity and 60 years after a grand 14C excursion during 5481–5471 BCE. The similarity of our 14C data to previous events suggests that the origin of the 5410 BCE event is an extreme SEP event. The 14C data of tree rings register extreme storms of solar energetic particles (SEPs), far larger than the largest SEP event ever observed in the Space Era. So far, three extreme SEP events have been reported as a rapid 14C increase in tree rings and 10Be and 36Cl increases in ice cores. In this study, we found a new rapid 14C increase in 5410 BCE using annual 14C content in ring samples from California, Switzerland, and Finland. The 14C signature of 5410 BCE event ties the origin of this 14C excursion to an extreme SEP event similar to three other extreme SEP events (774/775 CE, 992/993 CE, and ∼660 BCE) confirmed with radionuclides of ice cores. Rapid 14C increase of ∼6‰ with significant level was found in tree rings from California, Switzerland, and Finland around 5410 BCEFive thousand, four hundred ten BCE event occurred during a period of high solar activity and 60 years after a grand 14C excursion of ∼20‰ from 5481 to 5471 BCEThe similarity of this 14C signature to already known solar events suggests that the origin of this new 5410 BCE event is an extreme SEP Rapid 14C increase of ∼6‰ with significant level was found in tree rings from California, Switzerland, and Finland around 5410 BCE Five thousand, four hundred ten BCE event occurred during a period of high solar activity and 60 years after a grand 14C excursion of ∼20‰ from 5481 to 5471 BCE The similarity of this 14C signature to already known solar events suggests that the origin of this new 5410 BCE event is an extreme SEP

Abstract—We discuss possible evidence for a dilution of 14C caused by the Tunguska impact event, proposed by Rasmussen et al.(1999). The results presented in that paper and other available information do not support this hypothesis.

We report here that shells of the marine bivalve mollusc Arctica islandica, collected near King Edward, Scotland, yield isoleucine epimerization D/L ratios only slightly higher than ratios in late-glacial specimens of the same taxon collected from nearby sites. We have determined the ages of two of the King Edward shells by tandem-accelerator mass spectrometry (TAMS) radiocarbon dating to be >40kyr. From the difference in D/L ratios, we calculate the average temperature depression during the last glaciation to have been ≥9 °C below Holocene temperatures.

Communities of abundant organisms, similar to those which surround the hydrothermal vents of the East Pacific Rise (EPR), occur in 3,266 m of water in the Gulf of Mexico. They were discovered with the Alvin at 26° 02′ N, 84° 55′ W in an area where pore waters seep from the Cretaceous limestones of the adjacent platform at the contact between the Florida Escarpment and the Holocene hemipelagic sediments of the Abyssal Gulf. Because of the unusual abundance of organisms in this deep-sea environment, and the taxonomic similarities to the chemosynthetically based communities which surround the hydrothermal vents on the EPR, the seep communities are suspected to exist on a local non-photosynthetic food source1. We have now measured isotope ratios in tissues of organisms which surround these saline seeps to determine the origin of the local food chain. The tissues have extremely negative δ13C (−42 to −77‰, PDB) and δ15N (−2.72 to −9.34‰ air) values. Such highly fractionated carbon and nitrogen isotopes are unknown in food chains based on photosynthesis, suggesting that these communities are chemosynthetic. The cause of this extreme fractionation is attributed either to assimilation from local supplies of isotopically depleted methane and ammonium or to biochemical fractionation. The tissues of these animals contain significant amounts of 14C (∼60% modern), so the source of this fractionated carbon is not predominantly fossil methane.

Criteria for recognizing alien (historically introduced) plants in continental floras are largely inferential, involving range disjunctions, absence in the first botanical records for a region, pioneer status in secondary successions (‘weedy habit’), and, to a lesser extent, the fossil record. Decisions on whether a species is native or introduced commonly appear in local and regional floras. In a few cases, the plant's occurrence in the fossil record has reversed its presumed alien status1. Ironically, the appearance of assumed introduced species in prehistoric contexts could also be taken as an index of modern contamination due to stratigraphical mixing. We now present conclusive evidence for the prehistoric occurrence of Corispermum L. (Chenopodiaceae), a herbaceous annual growing on sandy soils throughout western North America, where it was previously reported as adventive from Eurasia. The use of tandem accelerator mass spectrometry (TAMS) for direct radiocarbon measurement of seeds eliminates problems with stratigraphical mixing and using this method we verify a pre-Columbian age for Corispermum.

Abstract—A new 2.8 kg meteorite find from the United States, Kansas University, is classified as an L6 (S3) chondrite based on optical microscopy and electron microprobe analysis of mafic minerals. Natural thermo‐luminescence (TL) and 14C measurements suggest that the Kansas University meteorite has a short terrestrial age compared to other meteorite finds from this area and is not paired with the other local meteorite finds, Densmore (1879), Lawrence, Kansas and Long Island, Kansas.

The view that human populations may not have arrived in the Western Hemisphere before about 12,000 radiocarbon yr BP1,2has been challenged by claims of much greater antiquity for a small number of archaeological sites and human skeleton samples. One such site is the Homo sapiens sapiens cairn burial excavated in 1971 from the Yuha desert, Imperial County, California3–5. Radiocarbon analysis of caliche coating one of the bones of the skeleton yielded a radiocarbon age of 21,500±1,000 yr BP4, while radiocarbon and uranium series analyses of caliche coating a cairn boulder yielded ages of 22,125±400 and 19,000±3,000 yr BP, respectively5. The late Pleistocene age assignment to the Yuha burial has been challenged by comparing the cultural context of the burial with other cairn burials in the same region6, on the basis of the site's geomorphological context and from radiocarbon analyses of soil caliches.7,8In rebuttal, arguments in defence of the original age assignment have been presented9,10as well as an amino acid racemization analysis on the Yuha skeleton indicating an age of 23,600±2,600 yr BP11. The tandem accelerator mass spectrometer at the University of Arizona has now been used to measure the ratio of 14C/13C in several organic and inorganic fractions of post-cranial bone from the Yuha H. sapiens sapiens skeleton. Isotope ratios from six chemical fractions all yielded radiocarbon ages for the skeleton of less than 4,000 yr BP. These results indicate that the Yuha skeleton is of Holocene age, in agreement with the cultural context of the burial, and in disagreement with the previously assigned Pleistocene age of 19,000–23,000 yr.

LUNAR soils treated with deuterated acid release a variety of deuterocarbon gases including CD4, C2D6, C2D4, C2D2and C3species1–3. We now suggest that the principal hydrolysable carbon phase in lunar samples is carbon in solid solution in body-centred cubic iron (α-Fe). The yield of deuterocarbons (excluding C2D2) from a lunar soil is probably a quantitative estimate of this carbon.