bluuebunny/crossref_metadata_2025 huggingface dataset:
Further Developments in On-Line Computing and Radiocarbon Dating At the British Museum
Authors: Hewson A D , Hall J A
Published: July 2016

In November 1973 the British Museum Research Laboratory acquired a Hewlett Packard 2100A mini-computer for the storage, calculation and retrieval of scientific measurements made on museum objects. A part of the computer's work is the calculation of radiocarbon dates based on the liquid scintillation counting of14C activities. A system of programs and files has been developed and has been in daily use since August 1974 (Hall and Hewson, 1977).

This paper describes changes and improvements to the system to make it more flexible so that it now provides the full range of facilities required by an active14C laboratory. The reporting procedures in particular have been restructured in the light of experience. The paper will be of interest to all laboratories that have, or hope to have, access to similar mini- or micro-computers.
Radiocarbon Ages of Shells in Holocene Marine Deposits
Authors: Donner Joakim , Jungner Högne
Published: July 2016

Radiocarbon dates of marine shells from Central West Greenland, Finnmark, in North Norway, and Dublin Bay, in Ireland, were used in dating relative sea-level changes. When fossil assemblages and formation of marine deposits and their relationship to sea-level were taken into account, the constructed curves of relative sea-level changes agreed with the shell dates. The origin of the shells in the deposits studied varied from site to site, but the dates gave additional information of the formation of marine deposits which could not have been obtained from the study of sediments alone.
Radiocarbon Dating By Ion Counting: Proposals and Progress
Authors: Hedges R E M , White N R , Wand J O , Hall E T
Published: July 2016

In the two years since the first successful measurements of 14C by high energy mass spectrometry, the advantages and the basic techniques of the method have been sufficiently reported. They will not be repeated here. This paper describes the work being done at Oxford to fill the gap between demonstrating the effectiveness of the approach and the creation of a facility dedicated to the carbon dating of milligram samples.
Radiometric Dating with the University of Washington Tandem Van De Graaff Accelerator
Authors: Farwell G W , Schaad T P , Schmidt F H , Tsang M-Y B , Grootes P M , Stuiver Minze
Published: July 2016

The University of Washington Model FN tandem Van de Graaff accelerator is being used for the measurement of extremely small isotopic abundance ratios, notably 14C/12C and 10Be/9Be, in a joint project of the Nuclear Physics Laboratory (NPL) and the Quaternary Isotope Laboratory (QL). The experimental arrangements and technical developments are described, and some preliminary results on isotopic ratios in carbon and beryllium are presented.
Unreliability of 14C Dates from Organic Matter of Soils
Authors: Gilet-Blein Nicole , Marien Gérard , Evin Jacques
Published: July 2016

Contamination by recent carbon and the turnover of organic matter make dating of ancient soils difficult. In order to isolate the oldest organic fraction of sediments, two main extraction methods were previously proposed: 1) alkaline solubilization of humus that separates humins, humic acids, and fulvic acids, and 2) successive hydrolyses that solubilize increasingly resisting products. Both preparation methods were tested on the same actual or fossil soils of different pedologic types from five geologic profiles on which other chronologic data are available.

Analytic results show that 14C ages obtained from alkaline extraction products differ according to the duration of treatments and characteristics of soils: while hydrolysis should yield more homogeneous results and isolate oldest fractions. It seems likely that true ages of geologic formations were never obtained from their organic matter and that the oldest organic fraction, contemporaneous with the sediment formation, completely disappears. Thus, most ages from 14C dating of organic matter of soils must be too recent.
University of Rome Carbon-14 Dates II
Authors: Alessio M. , Bella F. , Cortesi C.
Published: July 2016

A first list of datings by our laboratory was published in 1957 (Bella and Cortesi, 1957). The measurements were performed with a solid Carbon counter (Ballario et al., 1955). Between the beginning of 1958 and December 1961 laboratory apparatus was completely renewed and proportional gas-counters were introduced. At present four counters are available. Measurements are carried out with CO2 at 3 atm pressure.
Riken Natural Radiocarbon Measurements I
Authors: Yamasaki Fumio , Hamada Tatsuji , Fujiyama Chikako
Published: July 2016

Natural C14 measurements at the Institute of Physical and Chemical Research (RIKEN) became routine in 1962. The counters presently used are made of stainless steel with a volume of about 2.7 L. They are surrounded by 2.5 cm of pure lead, a ring of 22 propane gas-flow anticoincidence counters, about 10 cm of boric acid and 20 cm of iron. When filled with dead CO2 up to 2 atm, they gave a background counting rate of about 9 cpm (Hamada, 1960).

In this article, results obtained for geologic and archaeologic samples since 1962 are described. Dates have been calculated on the basis of the C14 half-life of 5568 yr, and 95% of NBS oxalic acid as modern standard. Correction for isotopic fractionation was not applied.
Texas A & M University Radiocarbon Dates I
Authors: Noakes John E. , Stipp J. J. , Hood Donald W.
Published: July 2016

The Radiocarbon Dating Laboratory of Texas A & M University was initiated as a research facility in the Oceanography and Meteorology Department. The facilities are available to graduate study programs and to other research groups associated with the University.

Research was begun in June 1960, towards development of a carbon dating method utilizing liquid scintillation counting. Benzene was chosen as the counting solvent because of its high energy transmitting properties and the high carbon content of benzene which could be totally derived from the sample to be dated. A catalytic method of synthesis of C6H6 at low temperature, as first reported by Shapiro and Weiss (1957), was further developed and modified by Noakes and others (1963) to a procedure suitable for carbon dating. A combined effort of this laboratory and the University of Texas Radiocarbon Dating Laboratory has resulted in a routine procedure for carbon dating, as reported earlier (Texas I).

In the dates reported here the sample preparation and the method of conversion of carbon samples to the counting solvent, benzene, was the same as reported in the earlier papers cited. The problem, reported then, of variation in background count rate between counting vials was eliminated by prior determination of the background for each vial used. With the exception of samples TAM 1 and TAM 2, all dates reported here were calculated according to this procedure.
Gakushuin Natural Radiocarbon Measurements III
Authors: Kigoshi Kunihiko , Lin Der-Hwang , Endo Kunihiko
Published: July 2016

This date list covers many of the datings done from November 1962 to October 1963. The instruments and technique used for this work are essentially the same as those used for the previous work (Gakushuin II). Age calculations are based on the Libby half life of C14, 5570 ± 30 yr. The errors quoted are the standard deviations obtained from the number of counts only. When observed activities are less than 2a above background, infinite dates are given with a limit corresponding to the activity of 3σ, and when they are greater than the activity of 95% of NBS oxalic-acid standard minus 2a, modern dates are given with the limit equal to 3a below the 95% of NBS standard.
Hannover Radiocarbon Measurements III
Authors: Geyh Mebus A. , Schneekloth Heinrich
Published: July 2016

The following list covers the measurements in our institute from January 1962 to March 1963. Sample preparation and conversion into acetylene are described by Wendt, Schneekloth and Budde (1962).

An Oeschger counter with an effective volume of 1.5 L came into operation in 1962. It is shielded by 4 cm of iron and 10 cm of lead. The background amounts to 2.24 cpm, the standard C14 counting-rate 17.05 cpm. In routine measurements, the impure acetylene, after a four-week storing period, is put into the counters. Examination of purity of the gas is carried out by means of an external Cs137 source. In case the gas shows bad plateau characteristics, it is converted by a new process into ethane, using H2 and a palladium catalyst. Thereby, the plateau characteristics improve considerably. The 50%-voltage then is 200 v lower, the slope of the plateau only amounts to 0.2 %/100 v (with external source), and the plateau length increases from 600 v to 1200 v. The additional work amounts to 1/2 hour.
Geological Survey of Canada Radiocarbon Dates VII
Authors: Lowdon J. A. , Blake W.
Published: July 2016

The 2-L counter (GSC I) and the 5-L counter (GSC IV) were operated routinely during the past year. The 5-L counter was operated at 1 atm, except for February-March 1967, when it was operated at 4 atm. Approximately half the determinations reported were obtained from each counter.
University of Kiel Radiocarbon Measurements III
Authors: Willkomm H. , Erlenkeuser H.
Published: July 2016

Most of the measurements have been obtained with a 4.5-L CO2 counter (Kiel I). Dates given are not corrected for C13/C12 except Ulmus series. Error corresponds to 1σ of statistical variations of sample net counting rate including variance of reference and background, but does not include the uncertainty in C14 half-life and in secular C14 variations. Half-life is 5570 yr and a.d. 1950 is zero point of b.p. scale.
Oak Ridge Associated Universities Radiocarbon Dates II
Authors: Noakes John E. , Kim S. M. , Fischer F.
Published: July 2016

The Radiocarbon Dating Laboratories of the Oak Ridge Associated Universities (ORAU) has previously published radiocarbon dates under the Oak Ridge Institute of Nuclear Studies (ORINS) name. ORINS has recently changed its name to ORAU and its laboratories and programs have accordingly assumed this new name. The ORINS prefix, which previously designated the published radiocarbon dates of this laboratory, will be continued to minimize confusion in the literature.

The radiocarbon dating program carried out at this laboratory is primarily concerned with assisting the ORAU Special Training Program in its teaching and research activities. Radiocarbon dates which appear in this paper represent samples submitted from research groups associated with the 41 universities which make up ORAU and by other college and university personnel who do not have access to radiocarbon dating facilities.

Carbon samples are chemically synthesized to liquid benzene and their C14 activity determined by liquid scintillation spectroscopy. Samples are first converted to lithium carbide and then to acetylene gas as described by Barker (1953). The acetylene is catalytically trimerized to benzene by a method described by Noakes et al. (1965). Chemical yields for the synthesized benzene routinely approach 90% with no evidence of chemical impurities or carbon isotope fractionation occurring in the chemistry.

A Packard Tricarb Model 314 D.C. liquid scintillation spectrometer, which has been modified for low level counting, is used to count the benzene samples. Counting efficiency is 50% when operating at a voltage of 800 with discriminator setting of 100-800-1000. Background count rate is 1.7 c/m with a 5 cc benzene sample. Shielding consists of 4 in. of lead with coincidence and anticoincidence systems.

The modern reference standard is 0.95% activity of NBS oxalic acid standard which is 6.82 c/m/g carbon. Ages are calculated on a C14 half-life of 5570 yr as suggested by Godwin (1962). The statistics quoted are compiled as one standard deviation (1σ) of the uncertainty involved in counting background, standard, and sample.
University of Saskatchewan Radiocarbon Dates V
Authors: McCallum K. J. , Wittenberg J.
Published: July 2016

This series reports some of the measurements made since publication of the previous list. Equipment and methods are described in Saskatchewan II.
Khlopin Institute Radiocarbon Dates I
Authors: Arslanov Kh. A.
Published: July 2016

Lime (grouting) from old structures near city of Khar'khov [50° 00′ N Lat, 36° 10′ E Long]. Subm. [n.d.] by L. P. Papkova.
Radiocarbon Dating in the Vernadsky Institute IV
Authors: Vinogradov A. P. , Devirts A. L. , Dobkina E. I. , Markova N. G.
Published: July 2016

Peat, at depth 3.5 m, from upper of 2 layers, at village of Timoshkovichi [53° 35′ N Lat, 26° 05° E Long], Korelichi Raion, Grodno Oblast, Belorussian SSR. Timoshkovichi is located on Novogrudok upland, beyond limits of region of Valday [Wurm] Glaciation. Cross section synchronous with ancient ravine of Neman R. basin where 2 horizons of peat can be detected: the lower, according to pollen data, accumulated at time of Mikulino [Eem] Interglacial; the upper believed accumulated at time of 2nd climatic optimum of Mikulino Interglacial, or at time of early Interstadial of Valday [Wurm] Glaciation (Tsapenko and Makhnach, 1959). Coll. 1962 by N. S. Chebotareva, Geog. Inst., Acad. of Sci., USSR.
Mass Spectrometric Studies of Carbon 13 Variations in Corn and Other Grasses
Authors: Bender Margaret M.
Published: July 2016

Our experience in radiocarbon dating has shown that dates obtained from samples of corn cob and kernels are usually too young compared with dates from wood samples. Since other laboratories have also commented on the same problem, a study of C13/C12 ratios in corn and other plant materials has been undertaken.
Berlin Radiocarbon Measurements III
Authors: Kohl G. , Müller H. M.
Published: July 2016

The following list includes selected geologic and pollen dated samples measured since 1965. After moving to new laboratory quarters, we increased shielding to 470 g/cm2 on all sides and 660g/cm2 at the top. Background of our Houtermans-Oeschger-type counters filled with 700 mm Hg of acetylene is now:
Instituto Venezolano De Investigaciones Cientificas Natural Radiocarbon Measurements IV
Authors: Tamers M. A.
Published: July 2016

The laboratory renewed operations in January, 1968 after a year's inactivity due to the absence of the head, who was on leave at the University of Bonn. Synthesized benzene continues as the dating medium, but various improvements have been made on the chemical method in order to increase capacity. Combustions are no longer carried out for normal materials. Instead, charcoal samples are used directly (after the usual pretreatment) and wood, plants, cloth, etc. are carbonized in a nitrogen atmosphere. Charring is a considerably more rapid procedure than combustion since it eliminates the CO2 collection, carbonate precipitation, and filtration steps. The charcoal then is reacted with molten lithium metal. Also, it was found that carbonates are attacked directly by hot lithium to produce carbides and the preliminary generation of CO2 gas is not indispensable. The carbide, cooled to room temperature, is reacted with old water (IVIC-317, Radiocarbon, 1967, v. 9, p. 240), the acetylene separated from hydrogen in a double liquid nitrogen-cooled trap, and benzene produced with a chromium activated silica-alumina catalyst.
Riken Natural Radiocarbon Measurements V
Authors: Yamasaki Fumio , Hamada Tatsuji , Hamada Chikako
Published: July 2016

The C14 dates given below are a continuation of the work presented in our previous list (Radiocarbon, 1968, v. 10, p. 333-345), and have been obtained by counting CO2 at ca. 2 atm pressure in a 2.7 L stainless steel counter. Results obtained mainly during 1968 are described.

Dates have been calculated on the basis of the C14 half-life of 5568 yr and 95% of NBS oxalic acid as modern standard.
University of Pennsylvania Radiocarbon Dates XII
Authors: Ralph Elizabeth K. , Michael Henry N.
Published: July 2016

This list is a continuation of Univ. of Pennsylvania Dates VII (Radiocarbon, 1965, v. 7, p. 179-186). It includes results for samples of Sequoia gigantea and for Pinus aristata, most of which were tree-ring dated at the Lab. of Tree-Ring Research, Univ. of Arizona.

All sequoia and bristlecone pine samples have been corrected for deviations in C13/C12 ratios. The δC13 values listed represent the deviations (multiplied by 2) of the samples measured from the δC13 value of our 100-yr old standard oak sample which is also the reference value (adjusted for zero age) for the calculation of δC14. In our previous publication (Radiocarbon, 1965, v. 7, p. 179-186), δC13 values were erroneously reported as negative deviations from our oak standard. For the calculation of the Δ's, however, they were used in the correct sense. This mistake has been corrected in this list and one notes that the sequoias and bristlecone pines tend to be enriched slightly in C13 as compared with the oak standard.
Tbilisi Radiocarbon Dates II
Authors: Burchuladze A. A. , Gedevanishvili L. D. , Mirianashvili G. M. , Togonidze G. I.
Published: July 2016

The peculiarities of the geologic structure of the Caucasus, of Georgia in particular, and the existence of numerous rich archaeologic monuments on the territory of the Georgian SSR have made it necessary for the Scientific Laboratory to date both geologic and archaeologic samples.
Fortaleza Radiocarbon Measurements I
Authors: Santiago M Marlucia F , Torquato Joaquim Raul , St Räde Heinz
Published: July 2016

This date list covers a selection of 14C results of hydrologic samples investigated from January 1978 until August 1979. According to convention, the ages were calculated with a 14C half-life of 5568 yr and 0.95% of the activity of NBS oxalic acid standard and are quoted in years before 1950. The recent activity of water is assumed to be 90% modern (Geyh and Kreysing, 1973) and corrections for 12C/13C isotopic fractionation have not been made.
Tartu Radiocarbon Dates X
Authors: Ilves Evald
Published: July 2016

The present list includes 74 dates of geologic samples determined using the liquid scintillation 14C method at the Geobiochemical sector of the Institute of Zoology and Botany, Academy of Sciences, Estonian SSR.
Use of the CO2 Source in Radiocarbon Dating by AMS
Authors: Bronk C R , Hedges R E M
Published: July 2016

Since Middleton showed the potential for a sputter source working from CO2, we have been building a source which can automatically change samples. The source produces a maximum beam of 25μA of C−, with typical operation between 10 and 20μA. Although beam generation from the source is very reliable, the mechanics of sample changing have given considerable problems. The changing of samples also involves considerable care in gas handling, and a computer control system has been written which ensures the correct sequence of the 16 operations required for sample change.
Low Background Liquid Scintillation Counting Using an Active Sample Holder and Pulse Discrimination Electronics
Authors: Noakes John E , Valenta Robert J
Published: July 2016

A Packard low-level liquid scintillation counting system is described which provides superior low-background beta-counting capability for3H and14C. The design is based on a novel pulse-discrimination circuit that separates background from valid scintillation pulses. Background discrimination is further enhanced by adding a plastic vial holder that acts as an anticoincidence guard. When excited by background radiation, the scintillation properties of the plastic provide an increased burst of photons to the detection electronics, which discriminate based on the number of component pulses in the burst. Experimental data demonstrate the low-level counting capabilities of this counter.
Changes of Carbon Isotopes in Atmospheric CO2 of the Kraków Region in the Last Five Years
Authors: Kuc Tadeusz
Published: July 2016

The Krakow Radiocarbon Laboratory has been measuring isotope composition of atmospheric CO2 and its natural concentration in the Kraków region for the last five years. We have been sampling on a continuous basis in two-week intervals at ca 20m above ground level, close to the center of Kraków. CO2 was sorbed while slow pumping atmospheric air through a molecular sieve. After recovery by heating, the CO2 was converted to benzene and 14C measured in a liquid scintillation spectrometer. In a small portion of CO2 δ13C was determined in a mass spectrometer. Concentration of CO2 was assessed by measurement of the volumes of the sorbed CO2 and the pumped air. A five-year record (1983–1987) reveals a multi-annual linear trend and winter-summer oscillations. Calculated parameters of the regression line (intercept and slope) for the measured δ14C, δ13C and concentration are: 222 (Jan 1983) and −15.5/yr, −9.57% (Jan 1983) and −0.042/yr, 336ppm (Jan 1983) and 1.4ppm/yr, respectively.
Changes in Ocean Ventilation Rates Over the Last 7000 Years Based on 14C Variations in the Atmosphere and Oceans
Authors: Peng T-H
Published: July 2016

Changes in the ocean ventilation rate may be one of the causes for a net decrease of 100‰ Δ 14C in atmospheric CO2 over the last 8000 years. Ocean ventilation rates of the past can be derived from the 14C record preserved in planktonic and benthic foraminifera in deep-sea sediments. Results of 14C dating using accelerator mass spectrometry on deep sea sediments from the South China Sea show that the age differences between planktonic (G sacculifer) and benthic foraminifera increase from 1350 yr ca 7000 yr ago to 1590 yr at present. An 11-box geochemical model of global ocean circulation was used for this study. Both tree-ring-determined atmospheric 14C values and foraminifera 14C age differences are used as constraints to place limits on patterns of changes in ocean ventilation rates and in atmospheric 14C production rates. Results indicate: 1) 14C production rates in the atmosphere may have decreased by as much as 30% between 7000 and 3000 yr ago, and may have increased again by ca 15% in the past 2000 yr, and 2) the global ocean ventilation rate may not have been at steady state over the last 7000 yr, but may have slowed by as much as 35%.
The Recovery and Dating of Carbon Dioxide in Polar Ice Cores
Authors: Wilson A T , Donahue D J
Published: July 2016

A new method is described for recovering trapped CO2 from polar ice cores. The ice is sublimed under vacuum, and H2O vapor and CO2 are collected at appropriate cold traps. The application of this method to obtain CO2 from a specific ice core, the conversion of that CO2 to graphite, and the measurement of radiocarbon in the CO2 are described in detail. The potentialities and problems of the method are discussed.
Evaluation of 14C Ages of Organic Fractions of Paleosols from Loess-Paleosol Sequences Near Xian, China
Authors: Head M J , Zhou Weijian , Zhou Mingfu
Published: July 2016

The 14C dating of organic fractions from paleosol layers containing <2% carbon in loess-paleosol sequences from the loess plateau in China has yielded results that are quite often much younger than the true age of the sediments. Percolation of modern organic materials from agricultural activities, and binding of these materials within the weathered clays of the paleosols has meant that conventional pretreatment techniques for 14C dating would not isolate a reliable chemical fraction. The total sequence from Bei Zhuang Cun, in Shaanxi Province, reflects the climatic history of the area for ca 30,000 years, ranging from the interstadial of the last glacial period to the postglacial period. Analysis of solvent extracts of organic material from this site indicates that they are mainly composed of carbohydrate residues originating from the relatively recent agricultural activity. Validity of the humic components for dating will be discussed.
Accelerator-Measured 14C Activity in Tree Rings From the Vicinity of the First Atomic Bomb Test
Authors: Leavitt S W , Long Austin
Published: July 2016

Detonation of the first fission bomb at White Sands, New Mexico, on July 16, 1945, produced a tremendous neutron flux capable of creating tritium and radiocarbon byproducts. We sampled a 115-year-old pinyon (Pinus edulis) 10km east of the Trinity test site to determine 14C evidence of this event. The most likely mechanism for this enrichment in the 1945 tree ring would be fixation of 14CO2 produced at the blast site and carried with the fallout cloud over the pinyon site. Analysis of cellulose of the 1944 and 1945 rings shows δ13C values of −19.9 and −19.5, respectively, and 14C activity (fraction of modern uncorrected for δ13C) as 0.991 ± .005 and 0.991 ± .006, respectively. It is likely that the duration and/or concentration of the 14CO2 exposure was not sufficient to increase 14C activity expected for that year.
Radiocarbon Dating of the Vučedol Culture Complex
Authors: Durman Aleksandar , Obelić Bogomil
Published: July 2016

Radiocarbon dates of the Vučedol culture range from its earliest beginnings at Vučedol and Pivnica to its late phase at Vinkovci, Eastern Slavonia, Hrustovača, northwest Bosnia, Parte, Slovenia and Rudine, northwest Croatia. Recent 14C analyses are discussed and compared to corresponding dates outside the scope of the Vučedol culture. Findings provide evidence for the expansion of the late Vučedol culture both in time and space.
An Overview of Some Interlaboratory Studies
Authors: Scott E M , Baxter M S , Aitchison T C , Harkness D D , Cook G T
Published: July 2016

Many interlaboratory studies have been made in the 14C community at irregular intervals over the past ten years. At times, the results from these studies have been contentious, mostly because of the lack of consistency in their findings. The importance of regular exercises has become particularly acute due to the large number of operating laboratories and the diversity of their methodologies. Hence, we briefly review the studies that have been made in the 1980s, focusing on those in which our laboratories participated. These include the 14C Interlaboratory Comparison in the UK (Otlet et al 1980), the International Comparison (ISG 1982, 1983) and the first two parts of the current International Collaborative Program (Scott et al 1989a, b). The development of each study, its findings and shortcomings, are highlighted in order to assess the concordance of the conclusions.
Sources of Random Error in the Debrecen Radiocarbon Laboratory
Authors: Hertelendi Ede
Published: July 2016

A new high-pressure methane-filled counter system for 14C dating was installed in 1986 when the first stage of the International Collaborative Study (ICS) started. Random errors in the new measuring system and in the process of chemical pretreatment and preparation were checked during the three years of intercomparison. Results show that the most important source of error in our laboratory is gas contamination. This causes variation of the count rate to exceed the statistically expected variability. Other sources of error are also discussed and limits of their contributions are given.
An Overview of All Three Stages of the International Radiocarbon Intercomparison
Authors: Scott E M , Aitchison T C , Harkness D D , Cook G T , Baxter M S
Published: July 2016

The International Collaborative Study involved a wide range of sample materials and ages and, on completion, assessed each stage independently (Scott et al 1989; Aitchison et al 1990). We combine here the three stages of the study and provide an overview of the uncertainties in the dating procedure as a whole and in its component processes. Three key optimal performance indices, related to internal and external precision and to bias, have been defined to allow quantitative assessment of Internal Consistency and External Consistency (Aitchison et al 1990). We believe that these measures provide quantitative descriptions of a laboratory's reproducibility, accuracy and precision.

For the internal consistency, we have defined the Internal Error Multiplier of the quoted error and, for the external consistency of any laboratory relative to an appropriate baseline, we have defined two indices, the Systematic Bias and External Error Multiplier of the quoted error. We have evaluated the three indices over the three stages and have assessed the relative performances of gas counting, accelerator and liquid scintillation laboratories. The quoted errors describe adequately the variability in duplicate results, but there is evidence of systematic biases and underestimation of interlaboratory variability. We have considered the contribution of pretreatment, synthesis counting to the overall variability for each laboratory type. We found that, for liquid scintillation (LS) and gas counting (GC) laboratories, ca 66% of the total variation is due to counting and sample synthesis whereas, for accelerator mass spectrometry (AMS) laboratories, the major sources of variability are the sampling and pretreatment processes.
Intercalibration of Environmental Isotope Measurements: The Program of the International Atomic Energy Agency
Authors: Gonfiantini Roberto , Rozanski Kazimierz , Stichler Willibald
Published: July 2016

We briefly present here the environmental isotope intercalibration programs of the International Atomic Energy Agency (IAEA). In fact, the IAEA has implemented two parallel programs during the last 20 years: for stable isotopes of light elements and for a radioactive isotope of hydrogen, tritium. This IAEA activity resulted in the preparation of a number of reference and intercomparison materials of various types, now stored in the Agency and available upon request.
Time-Resolved Liquid Scintillation Counting
Authors: Kessler Michael
Published: July 2016

Historically, scientists who perform low-level measurements of 14C for age dating, and 3H2O for environmental contamination, have purchased or constructed highly specialized instruments to quantitate low-level radionuclides using a general-purpose liquid-scintillation analyzer (LSA). The LSA uses special time-resolved 3-D spectrum analysis (TR-LSC) to reduce background without substantially affecting sample counting efficiency. This technique, in combination with a special slow fluor scintillating plastic, further reduces the minimal detectable limit for the TR-LSC liquid scintillation counter.
Report of the International Workshop of Intercomparison of Radiocarbon Laboratories: A Summary of the Meeting
Authors: Baxter M S
Published: July 2016

In closing this workshop, I must thank all of the delegates for making this meeting so very enjoyable for ourselves, the organisers. So much so that we will give serious thought to inviting you back to Scotland very soon. The meeting has, in our view, been eminently successful in the scientific sense. I believe that we have made uniquely important and fundamental observations and plans for the future of 14C dating. I would like to summarise quickly my personal view of the main findings of the workshop. I would start this by recalling the eight questions posed in my opening address. The questions and my impression of the workshop's answers are as follows:
Harwell Radiocarbon Measurements IX
Authors: Walker A J , Young A W , Keyzor R S , Otlet R L
Published: July 2016

The results in this list come from our earlier years of operation and form part of the special series of lists being prepared to clear the backlog of unpublished dates from this laboratory, in this case 49 samples coming from sites in and around Northampton, UK. They originate from excavations directed by John Williams and Helen M Bamford of the Northampton Development Corporation between 1973 and 1982, and all were submitted for measurement and paid for by the Ancient Monuments Laboratory of the Historic Buildings and Monuments Commission for England and Wales.
Łódź Radiocarbon Dates III
Authors: Kanwiszer Andrzej , Trzeciak Paweł
Published: July 2016

The results presented in this list were obtained from 1986 to 1989. Equipment, measurement and treatment of samples are as reported previously (Kanwiszer & Trzeciak 1984: 111). Age calculations are based on a contemporary value equal to 95% of the activity of NBS oxalic acid standard and on the conventional half-life for 14C of 5568 ± 30 years. Results are reported in years before 1950 (years BP). Errors quoted (± 1σ) include standard deviations of count rates for the unknown sample, contemporary standard and background. The dates are not corrected for 13C fractionation. Descriptions and comments are based on information supplied by submitters of samples.
Radiocarbon Dates for Lava Flows and Pyroclastic Deposits on São Miguel, Azores
Authors: Moore Richard B , Rubin Meyer
Published: July 2016

We report 63 new radiocarbon analyses of samples from São Miguel, the largest (ca 62 × 13km) and most populous (ca 150,000 inhabitants) island in the Azores archipelago (Fig 1). The samples are mainly carbonized tree roots and other plant material collected from beneath 20 mafic lava flows and spatter deposits and from within and beneath 42 trachytic pyroclastic flow, pyroclastic surge, mudflow, pumice-fall, and lacustrine deposits and lava flows. One calcite date is reported. The samples were collected during geologic mapping of the entire island (Moore, in press A; sample locations are shown on this map). Nine 1:25,000-scale topographic maps, published in 1983 by the Portuguese Army Cartographic Service, cover the island; samples and locations described below refer to these named sheets.
AMS Dating of a Late Quaternary Tephra at Graham's Terrace, New Zealand
Authors: Gillespie Richard , Hammond A. P. , Goh K. M. , Tonkin P. J. , Lowe D. C. , Sparks R. J. , Wallace Gavin
Published: July 2016

The radiocarbon dating of volcanic ash (tephra) deposits in New Zealand has been difficult on sites remote from the eruption, which contain either little carbon or degraded and contaminated charcoal. Although many studies of contamination removal from macroscopic charcoals from tephra sequences have been made, little attention has been paid to those containing no visible charcoal, because of the difficulty of obtaining sufficient carbon for radiometric dating. We report here experiments using accelerator mass spectrometry to establish a reliable method for dating a low-carbon aeolian and peat deposit containing a tephra horizon. Results so far demonstrate that improvements to existing chemical pretreatment methods are possible, and that dates obtained on oxidized fine-grained residues can approach the maximum age determined on good quality charred wood samples.
Harwell Radiocarbon Measurements XI
Authors: Hardiman M. A. , Fairchild J. E. , Longworth Geoffrey
Published: July 2016

Following Harwell Measurements VIII (Walker, Williams & Otlet 1990), this is the final series of lists of English archaeological dates commissioned for measurement by the Historic Buildings and Monuments Commission (HBMC) for England within prescribed contractual periods. This list, containing 127 dates, refers to the period April 1988 to March 1990, and results are reported irrespective of whether the associated projects are completed or ongoing.
Rehovot Radiocarbon Measurements IV
Authors: Carmi Israel , Segal Dror
Published: July 2016

The following list consists of dates of archaeological samples, obtained by gas-proportional counting of ethane, between 1985 and the end of 1991. During this time a close cooperation has been established with the Israel Antiquities Authority, which now has an archaeologist (D.S.) participating in the operation of the lab and serving as a liaison officer with the archaeological community.
University of Granada Radiocarbon Dates VI
Authors: Gonzalez-Gomez Cecilio
Published: July 2016

This paper includes determinations of archaeological, geological, palaeobotanical and other samples from Spain, Portugal and Bolivia, measured at the University of Granada Radiocarbon Dating Laboratory, mostly from 1989 to 1990. Pretreatment of charcoal and wood samples is a standard acid-basic procedure using 8% HCl and 2% NaOH at boiling temperature. We obtain collagen from bone samples using the Longin (1971) method.
Implications of Dipole Moment Secular Variation from 50,000–10,000 Years for the Radiocarbon Record
Authors: Sternberg R. S. , Damon P. E.
Published: July 2016

Sparse paleointensity data from 10–50 ka suggest that the average dipole moment (DM) was 50–75% of the average of 8.67 μ 1022A m2for the past 5 Ma, and 8.75 μ 1022for the past 12 ka. A linear ramp function, increasing the DM from 4 to 8.75 μ 1022A m2between 50–10 ka BP, generates a total14C inventory of 126 dpm/cme2, agreeing very well with an inventory assay of 128 dpm/cme2, which includes14C in sediments. With the Lingenfelter and Ramaty (1970) production function and a model DC gain of about 100, this DM function would give a Δ14C of 500‰ at 20 ka BP, consistent with the Barbados coral record, and also gives a good match to the Holocene record. A Laschamp geomagnetic event at about 45 ka BP, with a DM of 25% of its average value and lasting 5 ka, would only increase the present inventory by 0.3–1.2 dpm/cme2, and would probably have only a small effect on Δ14C at 20 ka BP, but could produce a short-lived14C spike of over 500‰.
Reflection of Solar Activity Dynamics in Radionuclide Data
Authors: Blinov A. V. , Kremliovskij M. N.
Published: July 2016

Variability of solar magnetic activity manifested within sunspot cycles demonstrates features of chaotic behavior. We have analyzed cosmogenic nuclide proxy records for the presence of the solar activity signals. We have applied numerical methods of nonlinear dynamics to the data showing the contribution of the chaotic component. We have also formulated what kind of cosmogenic nuclide data sets are needed for investigations on solar activity.
Variation of Radiocarbon Content in Tree Rings During the Maunder Minimum of Solar Activity
Authors: Kocharov G. E. , Peristykh A. N. , Kereselidze P. G. , Lomtatidze Z. N. , Metskhvarishvili R. Ya. , Tagauri Z. A. , Tsereteli S. L. , Zhorzholiani I. V.
Published: July 2016

We present here annual data on 14C abundance in tree rings during the Maunder minimum of solar activity (ad 1645–1715). We show that the solar modulation persisted during the minimum. We also compare these data with measurements of 10Be concentration in dated polar ice cores and with records of aurorae recurrence during this time interval.
A Supernova Shock Ensemble Model Using Vostok 10Be Radioactivity
Authors: Sonett C. P.
Published: July 2016

Analysis of the Vostok ice-core record of 10Be (Raisbeck et al. 1987) suggests that the sharply resolved increases in 10Be at 35 ka (kyr) and 60 ka are due to cosmic-ray (CR) increases. As an alternate to long-term solar modulation or strong decreases in the Earth's magnetic field, supernova (SN) forcing is qualitatively consistent with the generation of a forward-reverse shock ensemble from a spherical blast wave of age very approximately at 75 ka. This age agrees with Davelaar, Bleeker and Deerenberg's (1980) identification of 75 ka for the age of a North Polar Spur SN remnant. Confirmation would be the first geochemical detection of supernova forcing of spallogenic and perhaps cosmogenic isotope production in the atmosphere. The three 10Be increases can be satisfied by a modification of the Sonett, Morfill, and Jokipii (1987) model. This consists of 2 or 3 shock waves from a single SN event, which includes the first stage in the expansion, leading to a forward shock, S1+, and a pair of reverse waves, S1− and S2−. One reverse wave arises from the spherical expansion, itself, and the other is a reflected wave from a remnant precursor shell boundary from a more ancient SN. The model requires the solar system to be immersed in the ‘bubble’ of the earlier post-SN evolution, possibly affecting estimates of heliospheric boundary distance. However more recent analysis of Camp Century ice core data discloses only the 35 ka 10Be peak. This recent result compounds the difficulty of constructing a completely consistent model for the source of the Vostok spikes. This paper is written in the spirit of suggesting only one of possibly several different models, even within the subclass of SN models.
Theoretical and Experimental Aspects of Solar Flares Manifestation in Radiocarbon Abundance in Tree Rings
Authors: Kostantinov A. N. , Levchenko V. A. , Kocharov G. E. , Mikheeva I. B. , Cecchini Stefano , Galli Menotti , Nanni Teresa , Povinec Pavel , Ruggiero Livio , Salomoni Agostino
Published: July 2016

We describe our method of determining solar cosmic-ray flux and spectrum in the past, based on the comparison of different cosmogenic isotopes. For the period, AD 1781–1950, we have detected several intervals with a high probability of powerful solar flares.
National Taiwan University Radiocarbon Dates III
Authors: Liu Tsung-Kwei
Published: July 2016

This list consists of radiocarbon dates for geological samples measured from 1988 to 1990 at the resumed National Taiwan University (NTU) Radiocarbon Dating Laboratory. The NTU Radiocarbon Dating Laboratory was re-activated in 1988, after more than 14 years.
On the 14C and 39Ar Distribution in the Central Arctic Ocean: Implications for Deep Water Formation
Authors: Schlosser Peter , Kromer Bernd , Östlund Gote , Ekwurzel Brenda , Bönisch Gerhard , Loosli H. H. , Purtschert Roland
Published: July 2016

We present ΔA14C and 39Ar data collected in the Nansen, Amundsen and Makarov basins during two expeditions to the central Arctic Ocean (RV Polarstern cruises ARK IV/3, 1987 and ARK VIII/3, 1991). The data are used, together with published Δ14C values, to describe the distribution of Δ14C in all major basins of the Arctic Ocean (Nansen, Amundsen, Makarov and Canada Basins), as well as the 39Ar distribution in the Nansen Basin and the deep waters of the Amundsen and Makarov Basins. From the combined Δ14C and 39Ar distributions, we derive information on the mean “isolation ages” of the deep and bottom waters of the Arctic Ocean. The data point toward mean ages of the bottom waters in the Eurasian Basin (Nansen and Amundsen Basins) of ca. 250-300 yr. The deep waters of the Amundsen Basin show slightly higher 3H concentrations than those in the Nansen Basin, indicating the addition of a higher fraction of water that has been at the sea surface during the past few decades. Correction for the bomb 14C added to the deep waters along with bomb 3H yields isolation ages for the bulk of the deep and bottom waters of the Amundsen Basin similar to those estimated for the Nansen Basin. This finding agrees well with the 39Ar data. Deep and bottom waters in the Canadian Basin (Makarov and Canada Basins) are very homogeneous, with an isolation age of ca. 450 yr. Δ14C and 39Ar data and a simple inverse model treating the Canadian Basin Deep Water (CBDW) as one well-mixed reservoir renewed by a mixture of Atlantic Water (29%), Eurasian Basin Deep Water (69%) and brine-enriched shelf water (2%) yield a mean residence time of CBDW of ca. 300 yr.
Intercomparison of High-Precision 14C Measurements at the University of Arizona and the Queen's University of Belfast Radiocarbon Laboratories
Authors: Kalin R. M. , McCormac F. G. , Damon P. E. , Eastoe C. J. , Long Austin
Published: July 2016

High-precision measurements were completed concurrently at the University of Arizona and the Queen's University of Belfast on blind samples of Irish oak originally measured for the 1986 radiocarbon calibration curve. Subsequent single-year Sequoiadendron results were decadally averaged and compared with published results on decadal Douglas-fir samples. The results of these intercomparisons show that the Arizona high-precision results compare favorably with published values from the University of Washington, but show a systematic offset with published Belfast data.
Dating of Lake and Loess Sediments
Authors: Beer Juerg , Sturm Michael
Published: July 2016

Lake and loess sediments represent archives that record important information about the iocal, regional and global climate conditions in the past. Lake sediments consist of autochthonous particles formed by biogeochemical processes within the lake and allochthonous particles brought into the lake from the catchment area. After deposition, the stratigraphy of the sediment can be altered by chemical, physical and biological processes. Under favored conditions, the sediment shows individual annual layers (varves), which can be used to date the sediment. Other dating methods are based on radioactive decay (14C, 210Pb) or on time markers such as tephra layers, deposits of natural catastrophes, e.g., floods, or radioactivity, e.g., emissions from a nuclear power plant.
Note Concerning “Intercomparison of High-Precision 14C Measurements at the University of Arizona and the Queen's University of Belfast Radiocarbon Laboratories” by Kalin et al. (1995) and the Regional Effect
Authors: Damon Paul E.
Published: July 2016

Although a coauthor of the paper of Kahn et al. (1995), I was not available in time to review the final copy. Consequently, I take this opportunity to make further comments and, hopefully, clarify some of the content and conclusions.
Further Evidence of Changing Stability of the Atmosphere
Authors: Hartwig Sylvius
Published: July 2016

In a recent paper (Hartwig, ms.) I have shown that it is possible to understand and discuss the changing Austausch (i.e., exchange of air parcels between different atmospheric layers) between the stratosphere and troposphere by means of long-term measurement of series of spallation products. It is well known (Friend 1961; Müh et al. 1966; Hartwig et al. 1969) that there is a seasonal pattern in the 7Be concentration of ground-level air with a maximum during May–June. This maximum is caused by enhanced exchange processes between the atmospheric compartments of the stratosphere and troposphere during this interval. Generally, those exchange processes are a consequence of stability and dynamics of the atmospheric compartments, which themselves result from, among other factors, the distribution of the heat sources in those compartments, namely the ground and the ozone layer.
Commissioning of a Quantulus 1220™ Liquid Scintillation Beta Spectrometer for Measuring 14C and 3H at Natural Abundance Levels
Authors: Pawlyta Jacek , Pazdur Anna , Rakowski Andrzej Z. , Miller Brian F. , Harkness Douglas D.
Published: July 2016

In 1994, the Gliwice Radiocarbon Laboratory began operating a liquid scintillation spectrometry system, consisting of a Quantulus 1220™ spectrometer and two vacuum rigs for benzene production. This paper describes the procedures used for the benzene synthesis from samples containing < 1 g of carbon and in the range 1 to 10 g of carbon. We also present the Quantulus calibration procedures used in the Gliwice Radiocarbon Laboratory and NERC Radiocarbon Laboratory, and compare the calibration parameters.