ALBERT

Beschreibung: This study, which was carried out in the southern Brazilian Amazon region (Rondônia state and Humaitá, Southern Amazon state), presents and discusses the significance of carbon isotope data measured in soil profiles collected across natural boundaries of forest to savanna vegetation. The main objective of this study was to evaluate the expansion-regression dynamics of these vegetation units in relation to climate changes during the Holocene. 14C data from charcoal, soil organic matter (SOM) and its component humin fraction indicate that the organic matter in the studied soils is essentially Holocene in origin. 13C data indicate that C3 type plants were the dominant vegetation at all study areas in the early Holocene, and during the entire Holocene, in the forest sites of Central Rondônia state and in the forest site 50 km from the city of Humaitá. 13C data also indicate that C4 plants have influenced significantly the vegetation at the transitional forest and the Cerrado (wooded savanna) sites of Southern Rondônia state and the forest ecosystem located 20 km from the Humaitá city. These typical C4 type isotopic signatures probably reflect a drier climate during the mid-Holocene. The 13C records representing probably the last 3000 yr show an expansion of the forest, due to a climatic improvement, in areas previously occupied by savanna vegetation. These results and other published data for the Amazon region indicate that the areas representing today's forest-savanna boundaries have been determined by significant vegetation changes during the Holocene. The boundary between forest and savanna vegetation seems to be quite sensitive to climatic change and should be the focus of more extensive research to correlate climate and past vegetation dynamics in the Amazon region.

Beschreibung: We present a radiocarbon chronology of key Sayan-Altai monuments from the Scythian period, based on a statistical analysis of dates produced in the 1980s and now supplemented with new dates. These new 14C dates were produced for samples from the Tuekta-1 barrows (burial mounds) and were measured both in St. Petersburg and Groningen. These tree-ring samples were fitted to the calibration curve. Chronologies were established for the Arzhan, Tuekta-1 and Pazyryk-5 barrows. The time of the construction of the Arzhan and Pazyryk-5 barrows is the 9th and late 5th–4th centuries bc, respectively, and agrees with archaeology. According to new data obtained, the time of the Tuekta-1 barrow construction is some years older than has been accepted thus far by archaeologists.

Beschreibung: This note describes point and interval estimation of a settlement time from a collection of radiocarbon dates. An application concerning the settlement time of New Zealand is presented.

Beschreibung: By comparing the radiocarbon age of the soils under burial mounds of known archaeological age with the surface-exposed (background) soils of the surrounding landscapes, we may evaluate the rates of humus renewal in these soils. In the cold climate of the mideastern areas of the Russian plains, the value of humus rejuvenation coefficient decreases. This shows that humus renewal is 5–10 times slower than in the warmer climate of the southern regions. Using the obtained data on the rejuvenation rate of humus substances, we can determine the age of paleosols and study the dynamics of the carbon exchange processes in the biosphere.

Beschreibung: Three very different Canadian soils—clay soils of the St. Lawrence Lowlands, sandy forest soils of the Ottawa Valley, and organic-rich sediments from a wetland on the Canadian Shield—have been cored, sliced and separated into different density fractions, and the radiocarbon content of these soil fractions measured. In two of the areas sampled, cores were obtained close to operating nuclear reactors, as well as from beyond their region of influence. As a consequence, it has been possible to ascertain the depths of penetration of both the weapons-testing pulse (peaking in 1963), and a 25–50-yr chronic reactor input of 14C.The percentage of carbon stored in different density fractions varied with soil type. Turnover times for bulk soil organic carbon, estimated from soil degassing rates, have been compared with those predicated on the residual “bomb” 14C in background cores, and/or on the ratio of reactor-emitted 14C retained in the soils to the total deposited during the lifetime of operation. Residence times for the heavy carbon fraction present at depths below the influence of anthropogenic inputs have also been estimated.The accumulated data will be incorporated in a revised soil model, adjusted for the parameters deemed to be most important to carbon turnover rates under Canadian conditions.

Beschreibung: Organic matter in sediments and suspended matter is a complex mixture of constituents with different histories, sources and stabilities. To study these components in a suspended matter sample from the Ems-Dollard Estuary, we used combined molecular analysis with pyrolysis/gas chromatography/mass spectrometry and stable and radioactive carbon isotope analyses of the bulk and separated chemical fractions. Carbohydrates and proteins, ca. 50% of the total organic carbon (TOC), are much younger than the bulk sample and have a somewhat higher δ13C value. Lipids and the final residue are considerably older and have lower δ13C values. The final residue, ca. 17% of the total carbon, consists mainly of aliphatic macromolecules that could be derived from algae or terrestrial plants. The δ13C value points to a marine origin.

Beschreibung: Radiocarbon activities and uranium isotopic disequilibria were measured in water samples from both the sandy Pleistocene coastal aquifer and within the upper Cretaceous Judea Group carbonate aquifer of northwestern Israel. The samples in both aquifers exhibit a decrease in 14C activity that is concomitant to the growth in 234U-excess. This suggests that under specific conditions, 234U-excess dating of groundwater can be used to corroborate 14C dates, while offering the possibility of extending the range of dating of groundwater beyond that of 14C.

Beschreibung: Radiometric and AMS radiocarbon dating of a 6-m sediment core from Loch Ness, Scotland, indicates that it represents perhaps the very end of the Late Pleistocene, and the first ca. 7500 yr of the Holocene. Counts of laminations observed in the Holocene section of the core suggest that they are present in sufficient number to constitute annual laminations (varves), an hypothesis consistent with the pollen record, which contains a sequence of zones representative of the Early, Middle and part of the Late Holocene regional vegetation history. On the basis of BSEM and X-ray studies of sediments, and modern seston trap data, the laminations are believed to be produced by winter floods, which introduce increased silt loading into the Loch. Sediment for the rest of the year is mostly composed of clay-sized material. This hypothesis is being further tested, however, by continuing sedimentological and microfossil studies.Time-depth relations for the core based on calibrated 14C dates and lamination counts, respectively, illustrate the close correspondence between the two sets of data. The latter are therefore now being used to develop a varve chronology for the Holocene for Loch Ness. This will then in turn be used for further chronological studies, and for investigations of palaeoclimatic variations over the eastern North Atlantic, to which the signal of lamination thickness in the sediments is thought to be particularly sensitive. They may also eventually be used for calibration studies, employing 14C dating of specific carbon compounds, or groups of compounds extracted from the sediment using modern organic geochemical methods.

Beschreibung: The carbonate hydrochemistry of groundwater from the Hvinningdal aquifer (Denmark) was studied by radiocarbon (accelerator mass spectrometry (AMS)) and δ13C measurements as a preliminary step towards 14C groundwater dating. The 14C concentrations varied between 30 and 100 percent modern carbon (pMC) in apparent contradiction with tritium (3H) data, which in most cases indicate a post-bomb date. The dilution of 14C can be explained as being due to the combined effect of dissolution of old soil carbonate and oxidation of old organic carbon. The last effect proved to be essential. To calculate this correction the dissolved oxygen concentration was used together with the δ13C values. The combined corrections bring the 14C concentrations up to post-bomb levels in better agreement with the 3H data.

Beschreibung: A newly operating accelerator mass spectrometry (AMS) facility such as VERA has to go through an extensive testing phase in order to establish optimal conditions for 14C measurements, especially in the field of archaeological samples where an overall precision of 0.5% is desirable.We discuss the results of our measurements at the milligram carbon level as they relate to long-term stability, reproducibility, precision and isotope fractionation.

Beschreibung: The first radiocarbon dates for the famous monuments of European Scythia were produced for the Kelermes, Seven Brothers, Solocha and Chertomlyk barrows (burial mounds) by both accelerator mass spectrometry (AMS) and conventional methods. The obtained 14C dates confirmed the traditional archaeological chronology, which was based on the analysis of written data and typological comparisons of Scythian artifacts with similar objects found in the Ancient East and Greece. The 14C dates for the European Scythian monuments are compared with the Asian ones. The 14C chronology of the European Scythian monuments shows chronological synchronisms between the Asiatic and European monuments. The calibrated ages for the investigated barrows generally agree with the archaeological data.

Beschreibung: The Earth is within the Contemporaneous Solar Maximum (CSM), analogous to the Medieval Solar Maximum (MSM). If this analogy is valid, solar activity will continue to increase well into the 21st century. We have completed 75 single-ring and 10 double-ring measurements from ad 1065 to ad 1150 to obtain information about solar activity during this postulated analog to solar activity during the MSM. δ14C decreases steadily during the period ad 1065 to ad 1150 but with cyclical oscillations around the decreasing trend. These oscillations can be successfully modeled by four cycles. These four frequencies are 1/52 yr-1, 1/22 yr-1, 1/11 yr-1, and 1/5.5 yr, i.e., the 4th harmonic of the Suess cycle, the Hale and Schwabe cycles and the 2nd harmonic of the Schwabe cycle.

Beschreibung: 14C dating with the new Vienna Environmental Research Accelerator (VERA) began with the age determination of a mummified marmot found in the Austrian Alpine region. Soft tissue and bones of the marmot were used for the investigation. For comparison, bone material from known-age samples was also processed and measured. These exercises showed that 14C dating with VERA is reliable, and since that time various samples from archaeological context have been dated.We also studied the applicability of the 14C method in forensic sciences to determine the time of death of human individuals. 14C/12C measurements of samples from different organic human material (bone collagen, lipids from bone and bone marrow, hair) were performed and compared with the tropospheric “bomb peak” values to transform the measured ratios into “calibrated ages”. For specific substances with rapid turnover rates, this gives an estimate for the time of death of the individual. In our study, lipids and hair yield reasonable times of death, whereas the collagen fraction from bones, which has a relatively long turnover time, is not suitable for this purpose.

Beschreibung: We illustrate here the combined use of geographic information system (GIS) technology and a radiocarbon database for analysis of the environmental components and ancient sites in Western Siberia during the period 10–45 ka bp. In total, 230 14C dates from 75 Late Pleistocene outcrops and Paleolithic sites were used to generate paleolandscape maps and to establish the features of the spatiotemporal distribution of Paleolithic sites.

Beschreibung: Accelerator mass spectrometry (AMS) at the milligram level is routinely performed, but it is difficult to go substantially below 100 μg of carbon. We discuss various approaches for sample preparation, machine operation and data evaluation, to meet the special requirements of 14C AMS measurements at the microgram-carbon level. Furthermore, we present first results obtained at the Vienna Environmental Research Accelerator (VERA) from 14C measurements of a snow sample from Gaithersburg, Maryland, USA, prepared at the National Institute of Standards and Technology (NIST).

Beschreibung: The majority of samples processed at the National Ocean Sciences AMS Facility (NOSAMS) thus far were collected as part of the World Ocean Circulation Experiment (WOCE). Due to the long storage time (2–3 yr) required to analyze thousands of samples on the accelerator mass spectrometer (AMS), a test was designed and implemented to determine the effects, if any, of storage time on 14C concentration. We find no systematic offsets in AMS measurements made over a 5-yr period between a total of 16 replicate sets from surface and deep water collected at the same locality. Furthermore, the average δ14C value from the deepwater AMS replicates (-213.1%, std. dev. 7.3) agrees very closely with the conventional 14C results published for GEOSECS (-212.7%) from station 320 taken 20 yr earlier.A total of 73 WOCE shipboard replicate sets (162 AMS measurements) were analyzed with a mean precision of 4.3%. AMS results from 20 more shipboard replicate sets (44 AMS measurements) submitted as CO2 from the Stable Isotope Laboratory (SIL) at the University of Washington were analyzed with a mean precision of 3.4%. These results suggest no significant difference between water stripping methods used in each preparation lab.To assess reproducibility, we calculate a pooled estimate of σ for replicates called s, which we use as an approximation of σTOT for a given sample type. The s for WOCE seawater replicates is 4.9% and 5.8% for SIL gas replicates. These numbers demonstrate an overall reproducibility of seawater AMS results at NOSAMS that is in line with reported errors. We take the difference between total error s and machine error as the overall standard deviation of combined uncertainties associated with preparation of samples and with AMS. For seawater samples processed at NOSAMS, σSPL is calculated to be 2.4%, and for the SIL gas replicates it is 4.8%.Reproducibility of samples prepared with an acid hydrolysis technique is demonstrated using 24 coral samples submitted in triplicate by Dr. R. G. Fairbanks of Lamont Doherty Earth Observatory. Seventy-two replicates were prepared and analyzed at NOSAMS with a mean reported precision of 1.2%. The pooled estimate s for the Fairbanks triplicates is 2.6%. We calculate a laboratory reproducibility uncertainty for coral hydrolysis samples of 2.2%.In 1993, NOSAMS participated in the Third International Radiocarbon Intercomparison (TIRI) Study. We report here 60 AMS analyses of the six TIRI test materials, five of which are organic carbon samples, to validate sample-processing methods for organic carbon sample AMS analyses at NOSAMS.

Beschreibung: In May 1995 an impressive karstic cave possessing dozens of burials dating to the main phase of the Chalcolithic Period (ca. 4500–3500 bce) was discovered in Peqi'in in the high hills of Galilee in northern Israel. It was subsequently excavated over the course of the following months. The large amount of unique ceramic ossuaries and the variety of burial offerings shed light, for the first time, on this critical societal development period in a region where its remains have rarely been found. Although the major significance of the cave is as a mortuary center, it was also utilized in a domestic capacity some centuries previously, during the generally less familiar Early Chalcolithic Period. We present here the dating of 22 14C samples collected from these separate phases of cave use. Their interpretation should aid in understanding of the absolute dating of the Chalcolithic Period and its relation to the period preceding its inception.

Beschreibung: With 〉40 14C dates, mainly on bones and charcoal, the site at Son Mas is the only megalithic sanctuary on the Balearic Islands that has been dated by 14C in detail. Although soil erosion made stratigraphy difficult and the monument was cleaned out regularly during its long use, the results demonstrate that the site was occupied from the Pretalayotic (Chalcolithic) until the Roman period. The aim of this study was not only to date the construction and the use of the sanctuary, but also to correlate this monument, by means of dispersion diagrams, with the other prehistoric sites situated within the same valley. The dates were also used to compare the site with the generally accepted chronology of the Balearic archipelago (Mallorca, Menorca, Ibiza and Formentera).

Beschreibung: We present results that demonstrate the potential of the Packard Tri-Carb® Model 2770TR/SL for radiocarbon dating. For 2 g of sample benzene, a stable background count rate of 0.307 cpm and a stable counting efficiency of 64.78% were determined using a 13–75 keV counting window. Changes to the mathematical routines for t-SIE (quench indicating parameter) calculation and a reduction in the activity of the external standard have enabled stability of the t-SIE to be achieved, and combined with the use of a suitable balance point counting window; all of these factors give the stability of performance required for 14C dating. Calculations based on the above parameters indicate that the limit of detection for 2 g samples, counted for 5000 min, is 〉48,900 yr bp. The great advantage of this system is that these data were acquired using inexpensive standard 7-mL low potassium borosilicate glass vials. Vial holders manufactured from BGO reduced the background to 0.15 cpm with a minimum effect on efficiency (64.46% for 13–75 keV). A similar calculation of the limit of detection gave 〉51,700 bp. The use of the BGO vial holders in other instruments employing time-resolved liquid scintillation counting (TR-LSC) (Models 2250CA and 2260XL) also brought about significant improvements in detection limits.

Beschreibung: To obtain a better understanding of the relationship between calcrete genesis and the results of different absolute dating methods, thermoluminescence (TL), radiocarbon (14C) and uranium/thorium (U/Th) were applied to coeval sample; take from a very young calcrete profile in Namibia. The methodically different ages reflect the characteristics of the applied dating methods, the genetics of calcrete and different events of calcrete genesis. The conventional 14C ages and the TL dates cover the last 50 ka, while the corresponding U/Th dates of coeval samples are many times larger, Uranium-series dates are not related to the deposition of the host material or to its cementation if the ages are smaller than ca. 120 ka. The TL clock is set to zero during eolian transport and the corresponding radiometric ages of the quartz and feldspar grains date the time of their deposition. The 14C ages of the cement correspond, on the other hand, to a time shortly after the onset of the cementation and long before its termination. In the case of very old calcrete, the mixture of young and old cement results in ambiguous ages if they cannot be confirmed by an independent technique.

Beschreibung: A recent broad study of the background of all types of low-level beta and gamma detectors has now made it possible to analyze its components more reliably and with greater detail. This general analysis is developed further here for gas proportional and liquid scintillation counters used in radiocarbon dating. The background of gas counters, which is dominated by secondary cosmic gamma radiation, is now well understood and can be described quantitatively. The background of liquid counters is less well understood and can only be described semiquantitatively, its analysis resting partly on estimates. Methods to reduce the background of both types of systems are described and their effectiveness discussed. This analysis may help in evaluating the quality of existing systems as well as in designing better ones.

Beschreibung: We present here new radiocarbon dates for the different barrows (burial mounds) of the nomadic tribes of the Scythian period in the Khakassia and Tuva regions (Central Asia). The time scale of these barrows is compared with the elite barrows of the Sayan-Altai. In agreement with archaeological evidence, some barrows in Khakassia are chronologically close in time to the Arzhan barrow. The first 14C dates produced for the barrows from the Tuva region belong to a later Scythian period, compared with the elite Arzhan barrow. We determined the final stage of the barrow construction, but to establish the starting time, more dates are necessary (both by dendrochronology and 14C).

Beschreibung: A new set of radiocarbon dates from a rockshelter in Mendoza, Argentina addresses the question of the temporal overlap between the presence of an unidentified extinct ground sloth (cf., Mylodontidae) and evidence of human activity. Dung balls on the cave floor, evidently deposited by sloth, are overlain by charcoal, apparently of cultural origin. 14C dates, mostly on charcoal and dung from this shelter, calibrated using recently published curves, as well as the stratigraphy of the deposits from which the samples were collected, suggest that any co-occurrence of humans and ground sloths in this region was brief. In contrast, the single date on mylodon dermal ossicles from this shelter suggests significant time overlap. Replication of this date as well as obtaining new high-precision 14C analyses from this site will be the next priority.

Beschreibung: We measured radiocarbon ages of 11 pieces of ancient Japanese documents by accelerator mass spectrometry (AMS). The purpose of this study is to compare the relationship between the calibrated 14C age and the historical age of Japanese paper samples. Calibrated ages of nine pieces agree with their historical ages, indicating that Japanese ancient documents can be used for 14C dating in the recent historic period. On the other hand, the 14C age of paper that was used for reinforcement of a sutra is ca. 300 yr older than the historical age of the sutra. This shows that the sutra was repaired with old paper.

Beschreibung: We discuss results of 14C dating peat of palsa of different regions of Northern Eurasia. We apply these dates to determine the age of active palsa growth during different periods of the Holocene in permafrost zone.

Beschreibung: We present δ13C data from both bulk organic sediment samples and terrestrial plant macrofossils from five high-resolution sedimentary sequences from the United Kingdom from which extensive multiproxy data sets have been obtained. These span the last glacial-interglacial transition. Chronological control has been provided by radiocarbon dating and/or tephrochronology. The results demonstrate that significant shifts in bulk organic δ13C can be identified at key climatic transitions in most of the sites. The data are affected by site-specific influences that restrict their use as chronological markers. However, terrestrial plant macrofossil records are more consistent and reveal shifts that appear to be synchronous and which therefore offer a basis for interregional correlation as well as significant paleoenvironmental information.

Beschreibung: β-counting software programs were developed and installed in new PCs for operation under a Windows® NT workstation. The new software programs allow us to simultaneously control several β-counting systems, either remotely or from within the laboratory. This setup is much less expensive than our previous arrangement, which required a separate PC for each counter.

Beschreibung: 14C is one of the radionuclides that are produced to different degrees by neutron-induced reactions in all types of nuclear reactors. Part of the 14C created is continuously released into the surrounding environment during normal operation as airborne effluents in various chemical forms (such as CO2, CO and hydrocarbons) through the ventilation system of the plant. Because of the biological importance of carbon and the long half-life of 14C, it is of interest to measure the releases and their incorporation into living material. We report here on the 14C activity concentrations in annual tree rings and the air around two Swedish nuclear power plants, as well as the background 14C activity levels from two reference sites in southern Sweden from 1973–1996. We used both accelerator mass spectrometry (AMS) and decay counting in the investigation.

Beschreibung: Through the establishment of radiocarbon chronozones relating common geological events within lacustrine and eolian sediments from five profiles representative of loess yuan (tablelands), river valley and northwest margin features of the Loess Plateau, we propose a series of stratigraphic divisions within the last 30 ka. The focus of this detailed study involves stratigraphic relationships contributing to evidence of Younger Dryas events, with the recognition of cold-dry, cool-wet and cold-dry periods represented within the Heiheze silt, Midiwan peat and Liushuwan eolian sand. The stratigraphic profiles reflect century-scale fluctuations of the East Asian monsoons. The precursor events enable us to place the Pleistocene/Holocene boundary at 10,000 bp.

Beschreibung: We report on a review of 14C production and release from the nuclear industry in the United Kingdom (UK). Using earlier predictions (Bush, White and Smith 1984) it is estimated that a total of 1764 TBq of 14C would have been produced in UK graphite-moderated reactors up to the end of 1995, and 135 TBq of this total would have been released. Release rates, based on reported discharges, of 5.1 and 0.93 TBq GW(e)a-1 have been derived for Magnox reactors and Advanced Gas Cooled Reactors (AGRs), respectively. Using these new figures, cumulative discharges of 14C up to 1995 from reactors have been estimated at 531 TBq. The combination of these reactor discharges and the reported discharges from Sellafield (388 TBq) and Amersham (52 TBq) suggest a total cumulative release of 971 TBq of 14C up to the end of 1995.

Beschreibung: Accurate radiocarbon ages were obtained from terrestrial moss from two drill holes in Tern Lake deposits, Antarctica, using liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS). The results show that the lake deposits have been accumulating since the end of the last glacial epoch ca. 12,600 cal BP at the rate of 0.13–1.1 mm a-1. We discuss the validity of 14C ages of Antarctic lake deposits, with respect to the latitude effect of 14C productivity, the reservoir effect, the environment effect and the hard-water effect.

Beschreibung: We calculated apparent increment values based on the radiocarbon dates of 21 Estonian ombrotrophic mires (raised bogs). For short periods, the values vary significantly, but the integrated increment for the total complex of ombrotrophic peat shows a strong increasing tendency with decreasing peat age. This is probably due to the decay of accumulated organic matter. Our hypotheses concern the mechanisms of decay and methods for increasing the reliability of the interpolation and extrapolation of 14C data.

Beschreibung: Time series of δ14C, δ13C, and concentration of atmospheric CO2 covering the last 12 years are available at the Kraków sampling site (southern Poland) representing an urban area exposed to anthropogenic pollution of both local and regional origin. The samples represent continuous monitoring in biweekly intervals. Observations covering the time period 1983–1994 show a linear decrease of the 13C/12C ratio (δ13C = −9.6% in Jan. 1983) with a slope of −0.02% a−1. The decreasing tendency in the case of 14C (δ14C = 221% in January 1983) is weaker with a broad minimum in 1991 (δ14C = 124%) and subsequent gradual increase by ca. 10%, coinciding with a substantial reduction of coal consumption in Poland (26% reduction in 1991–1994 for heat and electricity production), partly compensated in agglomerations by increased gas consumption. The 12-year record of the CO2 concentration in Kraków points to a constant value fluctuating at a high level (average: 373 ppmv) reaching a maximum yearly average of 376 ppmv. These carbon isotope signatures were used for the separation of fossils from biogenic and “background” components, reflecting the strength of relevant sources. The monthly mean of the fossil component varies from ca. 10 ppmv in June to 27.5 ppmv in March while the yearly mean decreased ca. 16 ppmv since 1991.

Beschreibung: A living spruce tree was collected near the explosion center of the Tunguska event that occurred in 1908. We measured annual ring width and studied anatomical features to reconstruct the possible vegetational changes caused by the biological aftereffects of the Tunguska explosion. δ14C of annual rings from 1908 to 1910 was measured with a Tandetron accelerator mass spectrometer. The annual ring width decreased rapidly in 1908–1912, drastically increased in 1913, and decreased gradually thereafter. Traumatic resin ducts were observed in the transition zone between early- and latewood of the annual ring formed in 1908. We thus reconstruct these vegetational changes in the Tunguska forest: the Tunguska explosion damaged forest trees severely for ca. 3 yr, releasing rich nutrients from burned plants into the soil, and subsequently the vegetation was stimulated to recover by decreased socio-biological competition and better lighting conditions. δ14C values range from −28.2 to −1.5% for Tunguska spruce, and from −29.7 to 12.6% for Hinoki cypress. These fluctuations are within the ranges presented in Stuiver and Becker (1993), suggesting no evidence of anomalies of cometary origin in carbon isotopic composition. We found no significant difference between δ14C of Tunguska spruce and of Hinoki cypress.

Beschreibung: 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.

Beschreibung: Interlaboratory comparisons have been widely used in analytical chemistry and radiochemistry as an important part of ongoing quality assurance programs. The 14C community has been no exception in this respect, and in just under 20 years, there have been a number of significant and very extensive interlaboratory trials organized by individual laboratories and the International Atomic Energy Agency (IAEA) to the benefit of the 14C community (both labs and users) (Otlet et al. 1980; ISG 1982; Scott et al. 1990; Rozanski et al. 1992; Scott et al. 1992; Gulliksen and Scott 1995). The comparisons have varied widely in terms of sample type and preparation, but all have had as their primary goal the investigation of the comparability of results produced under possibly quite different laboratory protocols. As techniques have been developed and new labs formed, the reference materials created as a result of the intercomparisons have presented an opportunity for checking procedures and results. Users have been reassured by the existence of regular comparisons as one sign of the concern that laboratories have to ensure highest quality results, but also confused about how to make use of the results from past exercises in the interpretation of sets of dates from many laboratories. The laboratories have also learned valuable lessons from participation in such studies. These have included identification of systematic offsets and additional sources of variation and in studies which have used realistic samples requiring pretreatment, chemical synthesis and counting, it has been possible to identify the stage at which such problems have arisen and to quantify the relative contributions to the overall variation. In this paper, we will briefly review the comparisons so far, draw some conclusions from their findings, and make proposals for the future organization of intercomparisons.

Beschreibung: We discuss the possibility of dating ice wedges by the radiocarbon method. We show as an example the Seyaha, Kular and Zelyony Mys ice wedge complexes, and investigated various organic materials from permafrost sediments. We show that the reliability of dating 18O variations from ice wedges can be evaluated by comparison of different organic materials from host sediments in the ice wedge cross sections.

Beschreibung: Tree trunks and wood fragments in minerotrophic fen peat that accumulated as the result of a jökulhlaup in the outwash plain of Unteraarglacier were radiocarbon-dated using conventional ß-counting. Different pretreatment methods were tested on two wood samples to determine the reliability of our dates. We dated the wood compounds after extended acid-alkali-acid treatment, as well as extraction of cellulose and lignin. The results of the samples Picea (B-6687) and Pinus cent-bra (B-6699) show insignificant differences of 〈 1σ.The 14C dates represent retreat of Unteraarglacier due to warmer and/or drier phases in the Holocene compared to modern climate conditions. The glacier was at least several hundred meters smaller in extent than today ca. 8100–7670 bp, 6175–5780 bp, 4580–4300 bp, 4100–3600 bp and 3380–3200 bp. The 14C dates suggest a ca. 2000-yr cyclicity of tree growth in the area covered by the present Unteraarglacier. The most intense warm and dry period occurred between 4100 bp (probably extending back to 4580 bp) and 3600 bp, with growth of fen peat between 3800 and 3600 bp attributed to wetter conditions.

Beschreibung: The need for increased quality assurance for radiocarbon measurements performed by the monitoring laboratories at nuclear stations has spurred the introduction of a number of interlaboratory comparisons. We organized two such intercomparisons: the first set, circulated in 1994, consisted of two milk samples, one containing current global levels of 14C, the other containing an added spike of 14C-methylated casein. The second set, circulated in 1995, consisted of two samples of natural vegetation growing on the site of the Chalk River Laboratories (CRL), containing two different levels of 14C, both well above global background. The response to our invitation to participate in these studies was very encouraging; six laboratories took part in the first intercomparison, eleven in the second. The list included both monitoring laboratories and those whose main function is 14C dating. Understandably, some of the latter preferred not to analyze the higher-activity samples. The results in 3 of the 4 data sets were consistent with a statistical distribution based on the reported errors. This report provides details of two intercomparisons, including the preparation of the samples, which may now be considered potential secondary reference materials, the range of analytical techniques in use at the participating laboratories, and a statistical analysis of the results returned to us.

Beschreibung: One explanation for the radiocarbon dates on the Shroud of Turin being younger than the time of Christ is that the heat from a fire, which scorched a portion of the Shroud, may have affected the 14C content (dates) on the shroud by affecting molecular exchange between the fabric and atmospheric carbon. This report describes a laboratory test on the susceptibility of cellulose, in the form of cotton, to incorporate carbon from CO2 while it is heated in a closed tube with carbon dioxide until the cotton considerably darkened. To maximize the effect of this hypothetical process, we simulated the shroud material with cotton that had a 14C level of 0.55 modern (55 pMC, equivalent to 4800 yr), and the atmosphere with pure CO2, which had a 14C level of 1.3 modern (130 pMC). No measurable 14C transferred from the gas phase to the solid phase. The implication of this test is that scorching is an unlikely mechanism to affect the apparent age of cellulose-like material.

Beschreibung: The chief objective of this paper is to improve our understanding of the Neolithic in eastern Hungary using absolute chronological data. To accomplish this we calibrated new measurements as well as previously published dates. The up-to-date, standardized evaluation of 147 calibrated measurements showed temporal overlaps between archaeological cultures defined on the basis of ceramic styles. The average timespan of tell settlements of 285 yr was obtained using radiocarbon dates from four major settlements in eastern Hungary: Berettyóújfalu-Herpály, Hódmezővásáhely-Gorzsa-Cukortanya, Öcsöd-Kováshalom and Polgár-Csőszhalom.

Beschreibung: Previous results from remains of tusks, teeth and bones collected from Wrangel Island (Vartanyan et al. 1995) had given results in the range 3730 bp to 20,000 bp and the authors had concluded that “mammoths inhabited Wrangel Island for as long as 6000 yr after the estimated extinction on the Siberian continent”. There still remained the question of the earliest date for such remains. Further, the authors had noted such samples may present some difficulty in dating and therefore duplicate samples had been measured in a second laboratory with satisfactory results. The replicate dating of important or controversial samples in more than one laboratory is well-established (e.g., Turin Shroud) and in this paper, we present results for 5 mammoth samples dated by 6 laboratories. Such interlaboratory comparisons provide an independent means of verification of laboratory comparability, and give added confidence in the results, particularly when applied to more controversial samples. A further objective of the work has been to evaluate the material for inclusion in any large-scale interlaboratory comparison, such comparisons having in the past formed part of laboratory quality assurance protocols. The design and organization of a laboratory intercomparison requires homogeneous samples in sufficient quantity to satisfy participants, and so in principle, a single mammoth tusk would meet these criteria. Samples such as the mammoth tusk have been used in previous intercomparisons: e.g., in the last large-scale international intercomparison (Gulliksen and Scott 1995), whalebone was one of the materials distributed. One of the key advantages of such material is that a single sample (a mammoth tusk) can be resampled for analysis by multiple labs and thus does not require bulk homogenization. Therefore, as part of a preselection process for a future intercomparison, five samples from separate mammoth tusks were collected from Wrangel Island in 1995 in sufficient quantity to allow multiple dating. The aim was to identify five separate samples of young age, sample up to 1 kg from each tusk and mark the location so that after preliminary dating, samples could be retrieved as required in the future. Six laboratories received samples for dating. The paper will discuss the results from the laboratories, present consensus values, and make recommendations concerning use of these samples in a future laboratory intercomparison.

Beschreibung: A significant reduction in cosmic-ray activity and backgrounds of the gas-filled proportional counters, as measured in a heavy iron shield, was observed when the Uppsala Conventional 14C Laboratory was moved in 1984. The new site was better shielded from cosmic rays because of additional concrete layers above the laboratory. A study that lasted over one year yielded a figure for the muon reduction. The backgrounds were reduced approximately to the extent expected from the soft-component contribution at the old Laboratory as judged from barometric-pressure dependence. After a few years, new electronics enforced, and enabled, the revision and improvement of the standard values for the activity and age calculations.A careful analysis of the results for the counters has increased the accuracy of the small corrections needed to yield internal error-multiplication factors mostly between 1 and 1.5 for the background for short periods of up to 12 months, and

Beschreibung: We discuss the radiocarbon chronology of the loess deposited during the Upper Pleniglacial (Isotope Stage II) for the key site of Cosautsi (Republic of Moldova), which presents some major problems in 14C dating. Special care was paid to accurate microstratigraphic positioning of samples, collection of top-quality material (mainly conifer charcoal), and selection of uncontaminated pieces for dating and crossdating with bones by accelerator mass spectrometry (AMS) and/or conventional 14C dating. The results provide reliable and precise information on the sedimentation processes, the succession of short climatic events and the cycle of recurrent human settlements on the site between ∼20,000 and 16,000 bp. Two sets of climatic improvements can be ascribed to interstadial oscillations named, successively, Cosautsi VI (19,500–19,000 bp) and Cosautsi V (18–17,500 bp).

Beschreibung: During the past two decades, accelerator mass spectrometry (AMS) has allowed major developments in many areas of geosciences and archaeology. In the near future, AMS should realize a similar potential in the field of biomedical research, leading ultimately to clinical applications. For such applications, the required instrument differs significantly from that presently used in the field of 14C dating. Whereas the needed accuracy and sensitivity is more than an order of magnitude less demanding than that for present state-of-the-art 14C instrumentation, the widespread acceptance of 14C AMS in biomedical research will require AMS spectrometers that are small, simple to operate and capable of handling CO2 samples. In order to satisfy these demands, HVEE has developed a compact 14C AMS spectrometer dedicated to biomedical research. The instrument consists of a compact accelerator with a footprint of 2.25 × 1.25 m and an ion source that features direct CO2 acceptance and optimal user friendliness. Having previously described the layout and design of the accelerator, we here discuss progress on the accelerator and present the design and first results of the CO2 ion source.

Beschreibung: Pretreatment of organic samples can be achieved by removal of contaminants, or, alternatively, by isolation of sample-specific components. We discuss the molecular aspects of these two pretreatment types, together with an assessment of their effectiveness in relation to sample type. The main division in sample type is the one between carbohydrates and proteins, leading to opposite chemical strategies for the two sample categories. Recommendations for routine 14C chemistry of organic samples also include the standardization of quality screening procedures using chemical, stable isotope and elemental data that can be collected routinely during the pretreatment of each sample.

Beschreibung: We have determined the earliest calibrated dates on three types of basketry from the Great Basin of western North America. The oldest twined basketry dates to 10,380–10,918 cal bp, reed duck decoys to 2355–2773 cal bp, and wooden sandals of sagebrush bark or twined tule to 9247–10,375 cal bp and 9242–9836 cal bp, respectively.

Beschreibung: Since 1994, a new data-acquisition system with rise-time (RT) based background reduction has been in operation at the Gliwice Radiocarbon Laboratory. During long-term stability tests, we observed large shifts in the RT spectra obtained during various measurement series. These shifts caused important changes in the count rate measured with RT reduction. As a result, we have ascertained that the shifts are the consequence of variable concentration of electronegative impurities. A correction method was considered, using average RT of pulses obtained in coincidence with the muon events, so-called ARTL (average rise time of L pulses), for estimation of the RT of the spectrum's shift. However, radiocarbon dates calculated based on count rates with RT discrimination, which were corrected using this method, are not more precise than traditional 14C dates. Nevertheless, the value of the average coincidence pulse RT is a good indication of sample gas purity.

Beschreibung: We have worked in collaboration with the Westinghouse Savannah River Company and Packard Instrument Company to develop a prototype instrument for remote, near real-time, in situ analysis of environmental levels of tritium in surface and ground water samples. The unit consists of a Packard Radiomatic™ 525TR liquid scintillation counter that has been modified to achieve lower detection levels through background reduction using Packard's After-Pulse Burst Discrimination electronics and an auxiliary Bi4Ge3O12 scintillation detector guard. The system is fully programmable to enable remote calibration, sample collection, sample analysis, reconfiguration of operational mode and interrogation for analytical results.

Beschreibung: The carbon concentration in CuO and iron was determined by isolating C. The values were in agreement with results reported in other studies. Contaminating carbon from CuO and Fe was transformed to AMS targets and measured for 14C. C-traces in CuO were shown to be the major contribution to the 14C sample processing blank. In addition, there is a significant variability in the 14C content of CuO observed between different production batches. The combined contamination potential of CuO and Fe was found to be 4.47–8.92 μg recent carbon, whereas the more realistic estimate for AMS-target preparation conditions ranged between 1.63 and 3.24 μg recent carbon, depending on the 14C level in CuO.

Beschreibung: 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.

Beschreibung: More radiocarbon analyses have been produced for the Neolithic flint mines of Grimes Graves than for any other site with which the British Museum's Radiocarbon Laboratory has been involved. Despite this heavy concentration of effort, a recent review of these figures concluded that poor sample selection, combined with a lack of sufficient quality assurance procedures, severely limit the use that can be made of this database. To overcome these difficulties, a redating program has been undertaken using a carefully selected subset of the original material. In this paper I discuss the flaws in the original data set, due to both technical and sampling problems; set out ways to avoid similar problems in the future, with particular reference to quality assurance; and discuss the new results and their archaeological implications.

Beschreibung: For very small samples, it is difficult to prepare graphitic targets that will yield a useful and steady sputtered ion beam. Working with materials separated by preparative capillary gas chromatography, we have succeeded with amounts as small as 20 μg C. This seems to be a practical limit, as it involves 1) multiple chromatographic runs with trapping of effluent fractions, 2) recovery and combustion of the fractions, 3) graphitization and 4) compression of the resultant graphite/cobalt matrix into a good sputter target. Through such slow and intricate work, radiocarbon ages of lignin derivatives and hydrocarbons from coastal sediments have been determined. If this could be accomplished as an “online” measurement by flowing the analytes directly into a microwave gas ion source, with a carrier gas, then the number of processing steps could be minimized. Such a system would be useful not just for chromatographic effluents, but for any gaseous material, such as CO2 produced from carbonates. We describe tests using such an ion source.

Beschreibung: This paper includes determinations of archaeological, geological and paleobotanical samples from Spain and Brazil, measured at the University of Granada Radiocarbon Dating Laboratory, mainly from 1991 to 1992. As previously reported (González-Gómez 1992), pretreatment of charcoal and wood samples is a standard acid-basic procedure using 8% HCl and 2% NaOH at boiling temperature. The collagen of bone samples was extracted by the Longin (1971) method. The method of dating is liquid scintillation counting of synthesized benzene.

Beschreibung: Céide Fields is a 12 km2 Neolithic field system in North Mayo in the west of Ireland. The fields, enclosed by an integrated system of stone walls, have been preserved intact by a cover of blanket bog that is 〉4 m deep in places. At many locations within this blanket bog the stumps of ancient pines (Pinus sylvestris) are found in situ. The pine roots in most cases are either on the surface of the mineral soil under the peat or at an intermediate level in the peat itself. The age of the trees in the bog overlying Céide Fields is therefore of great significance for the dating of the fields, as the trees must be younger than the bog in which they are growing, which in turn must be younger than the field system beneath it. We present here the dates (N = 15) for pine trees from the bogs overlying Céide Fields and the dates (N = 29) of pine trees from other areas of the North Mayo blanket bog. We compare these pine dates with published dates of peat associated with a major pollen analytical study from within the fields and with published dates for bog pine from Scotland. The results of the study suggest that the dates for the construction and period of use of Céide Fields and other Neolithic pre-bog field systems in North Mayo are older than anticipated and that the date for initiation of blanket bog in many parts of North Mayo is also older than previously estimated. Further, the range of dates of the pine stumps indicates a synchronic event contemporary with a similar phenomenon observed in Scotland.

Beschreibung: The lithium reagent used in the synthesis of benzene for 14C dating contributes insignificant 14C in high-precision measurements on 7 g benzene samples. Blank experiments on three different batches of lithium yielded small amounts of carbon, most of which probably originated as “memory” in the reaction vessel.

Beschreibung: We have developed a technique using a single apparatus to recover the inorganic and organic carbon from a small (few milligrams) aliquot of dried marine material for radiocarbon analysis. The main advantages of using a single apparatus are: 1) less sample is required, 2) decreased handling reduces contamination, and 3) less time and materials are used. Blank values of ∼5 μg and 19–44 μg are obtained for the inorganic and organic carbon extractions, respectively. δ14C results from sinking particulate organic and inorganic carbon are presented for samples collected in deep-sea sediment traps deployed for 10–30 day periods at 650 and 100 m above bottom (mab) in the northeast Pacific Ocean.

Beschreibung: The following radiocarbon date list contains dates of samples measured since our previous list (R, 1982, v 24, p 352–371). As before, age calculations are based on the Libby half-life (5570 ± 30) yr and reported in years before 1950. The modern standard is 0.95 of the NBS oxalic acid activity. Sample pretreatment, combustion, and counting technique are essentially the same as described in R, 1971, v 13, p 135–140, supplemented by new techniques for groundwater processing (R, 1979, v 21, p 131–137).

Beschreibung: Radiocarbon determinations, employing both decay and direct counting, were obtained on various organic fractions of four human skeletal samples previously assigned ages ranging from 28,000 to 70,000 years on the basis of their D/L aspartic acid racemization values. In all four cases, the 14C values require an order of magnitude reduction in age.

Beschreibung: In the past 30 years many hundreds of archaeologic samples have been dated by radiocarbon laboratories. Yet, one cannot say that 14C dating is fully integrated into archaeology. For many archaeologists, a 14C date is an outside expertise, for which they are grateful, when it provides the answer to an otherwise insoluble chronologic problem and when it falls within the expected time range. But if a 14C date contradicts other chronologic evidence, they often find the ‘solution’ inexplicable. Some archaeologists are so impressed by the new method, that they neglect the other evidence; others simply reject problematic 14C dates as archaeologically unacceptable. Frequently, excavation reports are provided with an appendix listing the relevant 14C dates with little or no discussion of their implication. It is rare, indeed, to see in archaeologic reports a careful weighing of the various types of chronologic evidence. Yet, this is precisely what the archaeologist is accustomed to do with the evidence from his traditional methods for building up a chronology: typology and stratigraphy. Why should he not be able to include radiocarbon dates in the same way in his considerations?

Beschreibung: 14C dates of a medieval settlement with archaeologically well-dated strata are compared with the true ages of the respective layers. The 14C values indicate that each layer may contain older material reaching up to the beginning of settlement. Therefore, the 14C measurement of only a few wood or charcoal samples may lead to age estimations several hundred years too old.

Beschreibung: Penguin is a Macintosh computer application that facilitates the use of CALIB 3.03, the 14C age calibration program by Stuiver and Reimer (1993). Penguin offers an easy user interface based on the well-known Macintosh standard multiwindow environment to create and edit the CALIB 3.03 calibration files and to export data in text format. Penguin and CALIB interact at the file level, i.e., Penguin is capable of reading and writing files in CALIB formats. Files containing the data are created in the Penguin environment and then saved on disk in the Penguin format. Penguin allows multiple editing of the calibration parameters and recalibration of the list of samples without the need to insert any modifications manually throughout the list. Penguin can also be used to read already calibrated files in order to extract the “cal” ages and display them in a spreadsheet-like window.

Beschreibung: 13C isotope analyses of different stages of benzene synthesis have been made to study partial isotope fractionation. More than 60 analyses of carbonates, charcoal, carbon dioxide, and benzene were made in a double collector mass spectrometer. In the first stage of the synthesis (conversion to carbon dioxide) little or no fractionation was observed, beyond the analytical error of the method. Later stages of the process, show a greater and systematic fractionation. The experimental techniques are described.

Beschreibung: A mini-gas-proportional counter prototype of 10ml capacity (at NTP) was constructed of oxygen-free Finnish copper. The counter tube will be one of 16 equivalent tubes of a small-sample gas counting system, which is equipped with passive graded shield made of lead, cadmium, and copper and a dual active anticoincidence shield, consisting of an external cosmic gas-proportional and an internal plastic scintillation guard. The aim of this study was to evaluate the parameters leading to the design of a cost-effective and compact shielding package for mini-counters.

Beschreibung: The preparation and calibration of a secondary standard for the INGEIS Radiocarbon Dating Laboratory are presented. This standard is barium carbonate with a specific activity almost twice that of NBS oxalic acid. It was prepared from BaCO3 with high specific activity and commercial potassium carbonate by an isotopic dilution technique. The advantages of this standard are: 1) the preparation is simple and can be achieved with ordinary labware; 2) the production of CO2 by acid attack from this carbonate shows minimum isotopic fractionation. At least, it has less fractionation than wet oxidation of oxalic acid, the problems of which are described in the literature. This standard ensures better reproducibility in activity measurements; 3) despite some problems of activity exchange with atmospheric CO2 concerning carbonates, measurements of activity over a period of about two years have shown no significant deviation from the mean value. A tentative explanation of this phenomenon is also given. The activity ratio between BaCO3 and NBS oxalic acid is given with its error, and the statistical tests used in the calibration are briefly explained. Finally, a control chart for the activity of the standard over a long period is drawn, showing non-significant deviation and supporting the usefulness of this standard.

Beschreibung: Computer storage and surveys of large sets of data should be an attractive technique for users of 14C dates. Our pilot project demonstrates the effectiveness of a text retrieval system, NOVA STATUS. A small database comprising ca 100 dates, selected from results of the Trondheim 14C laboratory, is generated. Data entry to the computer is made by feeding typewritten forms through a document reader capable of optical character recognition. A text retrieval system allows data input to be in a flexible format. Program systems for text retrieval are in common use and easily implemented for a 14C database.

Beschreibung: This paper discusses the characteristics of the commoner classes of writing materials and textiles deriving from ancient and more recent historical sources and the problems they present for 14C dating. The materials under consideration are, firstly, paper in various forms, parchment, and vellum (ancient papyrus, which poses different kinds of dating problems, is not considered) and secondly, fabrics such as linen, cotton, and woolen textiles, to which, from the dating point of view, similar technical considerations apply. Our main concern is with problems associated with the dating of paper.

Beschreibung: Variability in temperature and 14C levels are recorded in coralline aragonite that grew in the Gulf Stream during the past four centuries. In particular, 18O/16O ratios reflect a decrease of ca 1°C in surface water temperature during the latter part of the Little Ice age. 14C levels also rose in the surface waters of the Gulf Stream and in atmospheric CO2 during the Maunder minimum. These observations indicate that ocean circulation may have been significantly different in the North Atlantic around the beginning of the 18th century.

Beschreibung: 14C ages were obtained for the Australian lakes recorded below in order to complement research into their magnetic stratigraphy and sedimentology. It has been possible to establish precise 14C chronologies in six separate lakes, and also to compare ages obtained from stratigraphically equivalent horizons in different parts of the same lake so as to determine the reproducibility of these ages.

Beschreibung: We demonstrate the feasibility of pulse time of arrival information for early detection of periodic events in low level counting. Time of arrival data allows us to apply time series analysis and serial correlation tests which, in graphic form, give the user an illustrative view of the parameters affecting the validity of counting statistics. The decision to discontinue counting can already be made on the basis of less than 100 counts from the time information alone if more than 10 of these are non-Poisson periodic counts. The analyses also serve as a means of quality control for low level counting, being directly based upon the interval distribution of the Poisson process.

Beschreibung: The real-time measurement of net photosynthesis and dark respiration of plants has been possible since the development of the infra-red analyzer and its application in the 1940's. This technique has allowed intensive investigations of the mechanisms and dynamics of carbon dioxide assimilation by green plants (Sestak, Catsky, and Jarvis, 1971). As a result, physiologic and ecologic aspects of net carbon dioxide exchange are the subject of much research (eg, Osmond, Bjorkman and Anderson, 1980).

Beschreibung: This series reports some of the measurements made since publication of the last list (R, 1981, v 23, p 94–135). Also included are a number of earlier dates previously withheld pending submitter evaluation. For some the authors have been unable to obtain appropriate comment. References to other publication of these dates are given where known.Acetylene proportional gas counting methods essentially remain as described in Saskatchewan II (R, 1960, v 2, p 73). Bone dating is carried out on soluble collagen extract (Longin, 1971) since 1978.

Beschreibung: Facilities for radiocarbon dating were established at the University of Frankfurt/Main in the Institute of Anthropology. The Radiocarbon Laboratory provides assistance to the Amino-Acid-Dating Laboratory. This list reports on 14C dates measured up to September 1983.The laboratory is installed in the basement of a three-story building and is equipped with a 2L copper proportional counter filled to 1013 mbar with purified CO2. The counter is protected against cosmic and surrounding radiation by a 3.5 ton lead shield and a copper multiwire anticoincidence ring-counter flushed with purified 90Ar/10CH4. Electronics are of the commercial NIM type. Charcoal and wood samples are treated by standard acid-alkali-acid methods. Bone samples are treated according to the collagen methods described by Berger, Horney, and Libby (1964), Longin (1971), Protsch (1972; 1975), and Protsch and Berger (1973).

Beschreibung: The following list consists of dates for archaeologic and geologic samples mostly measured from June 1982 to June 1983. The dates were obtained by liquid scintillation counting of benzene using the laboratory procedures outlined in previous lists (see, eg, BM-VIII, R, 1976, v 18, p 16). Dates are expressed in radiocarbon years relative to ad 1950 based on the Libby half-life for 14C of 5570 yr, and are corrected for isotopic fractionation (δ13C values are relative to PDB). No corrections have been made for natural 14C variations. The modern reference standard is NBS oxalic acid (SRM 4990). Errors quoted with dates are based on counting statistics alone and are equivalent to ± 1 standard deviation (± 1σ). Descriptions, comments, and references to publications are based on information supplied by submitters.

Beschreibung: This radiocarbon laboratory began operation in 1980 using the benzene scintillation method. The benzene synthesizer is essentially identical with that of Ikeda (1976). A liquid scintillation counter is Aloca LSC-LB1. Samples dated are wood, charcoal, shell, and coral.Pretreatment of wood and charcoal is a standard acid-alkali procedure, using 2% HCl and 2% NaOH at elevated temperatures. Charcoal is further heated in concentrated HNO3 for one hour, diluted in water, stands one night, and is washed and dried. Pretreated wood and charcoal are carbonized before combustion. The combustion products are passed over CuO, and are collected in an ammonium hydroxide bubbler system, and precipitated with calcium chloride.

Beschreibung: A sodium bicarbonate solution with a 10-fold activity compared to oxalic acid is used as a secondary standard in the Heidelberg 14C Laboratory. All routine checks and counter tests are greatly facilitated because of the high activity of the solution.

Beschreibung: 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.

Beschreibung: Procedures and equipment have been described in previous date lists. Except as otherwise indicated, wood, charcoal, and peat samples are pretreated with dilute NaOH–Na4P2O7 and dilute H3PO4 before conversion to the counting gas methane; marls and lake cores are treated with acid only. Very calcareous materials are treated with HCl instead of H3PO4. Pretreatment of bone varies with the condition of the bone sample; solid bone with little deterioration is first cleaned manually and ultrasonically. The bone is treated with 8% HCl for 15 minutes, then dilute NaOH–Na4P2O7 for 3 hours at room temperature, washed until neutral, and the collagen extracted according to Longin (1971). Charred bone is treated with dilute HCl, NaOH–Na4P2O7, and then dilute HCl again.

Beschreibung: Procedures and equipment used in the University of Wisconsin laboratory have been described in previous date lists. Except as otherwise indicated, wood, charcoal, and peat samples are pretreated with dilute NaOH-Na4P2O7 and dilute H3PO4 before conversion to the counting gas methane; marls and lake cores are treated with acid only. Very calcareous materials are treated with HCl instead of H3PO4. Pretreatment of bone varies with the condition of the bone sample; solid bone with little deterioration is first cleaned manually and ultrasonically. The bone is treated with 8% HCl for 15 minutes, then dilute NaOH-Na4P2O7 for 3 hours at room temperature, washed until neutral, and the collagen extracted according to Longin (1971). Charred bone is treated with dilute HCl, NaOH-Na4P2O7, and then dilute HCl again.

Beschreibung: The geomagnetic field is one of the major physical fields of the earth. Because its source is fluid motion in the outer core, it exhibits temporal changes, called secular variation, which are quite rapid compared to most geologic phenomena. The prehistoric secular variation is usually inferred from paleomagnetic data. We will discuss here how changes in the atmospheric 14C content can be used to gain additional insight into the behavior of the dipole moment over the past 8500 years. By rewriting the differential equations representing the 14C geochemical cycle in finite-difference form, we are able to convert the atmospheric 14C activity record into an equivalent radiocarbon dipole moment.

Beschreibung: After routine accelerator mass spectrometry (AMS) radiocarbon dating had been established at the Leibniz-Labor with the completion of systems for CO2 production, graphitization, and target making, a systematic investigation was conducted to find the sources of 14C concentrations observed in background materials. We quantified the contributions of the AMS-system, the reduction, CO2 production from carbonate, carbonate contamination, and combustion. Carbonate contamination appears to be the dominating factor. Improvements in the pretreatment of foraminifer carbonate have led to the elimination of most of this contamination.

Beschreibung: Data on the depth distribution of the major atmospheric gases and the abundance of gaseous 12CO2, 13CO2, and 14CO2 in the subsoil unsaturated zone have been obtained from several sites in the western Great Plains of the United States. Sample profiles range from land surface to depths of 50m. Although each site must be considered on an individual basis, several general statements can be made regarding the profiles. 1) Diffusion of these gaseous molecules through the unsaturated zone is an important transport mechanism. 2) As predicted by diffusion theory, depth profiles of the various isotopic species of CO2 differ substantially from one another, depending on individual sources and sinks such as root respiration and oxidation of organic carbon at depth. 3) In general, post-bomb (〉 100% modern) 14C activities are not observed in the deep unsaturated zone, in contrast to diffusion model predictions. 4) In spite of generally decreasing 14C activities with depth, absolute partial pressures of 14CO2 in the subsoil unsaturated zone are 1–2 orders of magnitude higher than the partial pressure of 14CO2 in the atmosphere.

Beschreibung: We describe progress in developing a novel miniaturized laser-heated “microfurnace” aimed at preparing ultra-small (∼5 μg) graphite samples from CO2 (Smith et al. 2006, 2007, 2010). Recent effort has focused on automation of the process using a LabVIEW interface, which has permitted feedback control of the catalyst temperature as the reaction proceeds and the logging of reaction parameters. We trialed a number of different pure iron catalysts as well as Fe2O3 (which is reduced in situ to iron) and discuss the reaction rates. We studied the graphite morphology by scanning electron microscopy (SEM) and found there is a marked difference in graphite morphology with catalyst type. We assessed how each catalyst performs in the cesium sputter ion source of the ANTARES Accelerator Mass Spectrometry (AMS) facility. We utilized a quadrupole mass spectrometer to study the gas composition during the reaction, in order to better understand the underlying chemical reactions for such small samples and to better estimate the overall efficiency of the process. Results show that all CO2 is converted to CO by reduction on the iron catalyst within a few minutes of applying laser power. The reaction pressure stabilizes after 40 min; however, some CO is not converted to graphite. The cold trap temperature of –80 ° is effective at trapping H2O, so there is little CH4 production.

Beschreibung: A new and unique radiocarbon accelerator mass spectrometry (AMS) facility has been constructed at the Woods Hole Oceanographic Institution. The defining characteristic of the new system is its large-gap optical elements that provide a larger-than-standard beam acceptance. Such a system is ideally suited for high-throughput, high-precision measurements of 14C. Details and performance of the new system are presented.

Beschreibung: A test for the reliability of 14C dating of soil was made at two sites with buried, autochthonous, and in parts, allochthonous sandy podzols, dated either litho- and pedostratigraphically or palynologically. The differences between the age ranges obtained and the apparent mean residence times (AMRT) calculated from the 14C content of alkaline extracts from fossil soil layers and horizons lean in organic matter exceed 10,000 years, corresponding to a maximum contamination with recent carbon of up to 50 %. The use of correction factors for the apparent mean residence times of podzols is not valid, not even for climate zones, because these values have a broad scatter for the same profile.

Beschreibung: We measured the radiocarbon ages of 165 single-year tree rings from a Japanese Choukai Jindai cedar using accelerator mass spectrometry (AMS). By wiggle-matching the Choukai_AMS data set to the IntCal04 calibration data using OxCal v 3.10 and using the variation of the correlation coefficients between the Choukai_AMS and IntCal04 data sets, we precisely re-estimated that the 321 Choukai Jindai cedar tree rings range from 780 to 460 cal BC with an accuracy of 8 yr. The Choukai_AMS data set is older than the 3 raw data sets of European tree rings that comprise IntCal04. The Belfast and Seattle data sets are younger by −21.3 ± 5.5 and −22.7 ± 5.6 14C yr, respectively. The Choukai Jindai cedar is ∼22 14C yr older than the European tree rings, which is equivalent to an offset of −2.8‰ in 14C. In addition, the Choukai_AMS data set correlates well with the Belfast and Seattle data sets, with correlation coefficients of 0.89 and 0.68, respectively, between the temporal profiles. Hence, the temporal profile of the Choukai 14C ages shows a global variation.

Beschreibung: The article reports the first radiocarbon dating of a live African baobab (Adansonia digitata L.), by investigating wood samples collected from 2 inner cavities of the very large 2-stemmed Platland tree of South Africa. Some 16 segments extracted from determined positions of the samples, which correspond to a depth of up to 15–20 cm in the wood, were processed and analyzed by accelerator mass spectrometry (AMS). Calibrated ages of segments are not correlated with their positions in the stems of the tree. Dating results indicate that the segments originate from new growth layers, with a thickness of several centimeters, which cover the original old wood. Four new growth layers were dated before the reference year AD 1950 and 2 layers were dated post-AD 1950, in the post-bomb period. Formation of these layers was triggered by major damage inside the cavities. Fire episodes are the only possible explanation for such successive major wounds over large areas or over the entire area of the inner cavities of the Platland tree, able to trigger regrowth.

Beschreibung: Three factors—contamination, a dietary reservoir effect, and a regional δ14C anomaly—are considered as possible contributing explanations for an almost 2-century offset between the historically documented age of 612 BCE and the calibrated ages of 9 14C determinations obtained on 3 human skeletons directly associated stratigraphically with an archaeologically—and historically—defined 612 BCE event at the ancient site of Nineveh in northern Mesopotamia (Iraq). We note that on the order of a 1% (∼80 yr) offset caused by one or a combination of these 3 factors, or other as yet unidentified additional factor(s), would be sufficient to move the average measured 14C age of these bone samples within the major “warp” in the 14C timescale during the mid-1st millennium BCE. We provide what we believe to be sufficient evidence that contamination is not a major factor in the case of these bone samples. At this time, we lack appropriate data to determine with sufficient rigor the degree to which a dietary reservoir effect may be contributing to the offset. At present, a posited regional δ14C anomaly does not appear to be supported on the basis of data from several other localities in the Near East of similar age. One purpose of presenting this data set is to solicit comparisons with 14C values obtained on samples from additional, historically well-documented, known-age archaeological contexts for this time period in this and adjacent regions.