bluuebunny/crossref_metadata_2025 huggingface dataset:
Tata Institute Radiocarbon Date List IX
Authors: Agrawal D. P. , Gupta S. K. , Kusumgar Sheela
Published: July 2016

The C14 dates given below are in years b.p. calculated on the basis of τ1/2 = 5568 years. For converting to a.d./b.c scale, 1950 was used as reference year. Ninety-five per cent activity of NBS oxalic acid was used as a modern standard.
Bratislava Radiocarbon Measurements I
Authors: Usačev S. , Povinec P. , Chudy M. , Šáró Š.
Published: July 2016

The Radiocarbon Dating Laboratory was established in 1967 at the Department of Nuclear Physics, Comenius University, as part of a program of low level counting research of the department and as a contribution to geophysical, geologic, archaeologic and hydrologie research.
Lyon Natural Radiocarbon Measurements IV
Authors: Evin J. , Marien G. , Pachiaudi Ch.
Published: July 2016

This list includes most of the samples measured from June 1970 to June 1972 and some other results not yet published in previous date lists.
Tehran University Nuclear Centre Radiocarbon Dates II
Authors: Bovington Charles , Avi Azizeh Mahd , Masoumi Roghiyeh
Published: July 2016

Ages reported in this date list are calculated using the Libby half life of 5568 ± 30 years with 1950 as the standard year of reference; results are quoted in years b.p. and on the a.d./b.c. time scale.
La Jolla Measurements of Radiocarbon in the Oceans
Authors: Linick T W
Published: July 2016

The La Jolla Radiocarbon Laboratory has measured carbon-14 concentrations in seawater samples collected from 1957 through 1972. The dissolved inorganic carbon in seawater was extracted on board research vessels and was returned to the laboratory for processing and measurement. Both surface and sub-surface samples were collected, primarily from the Pacific Ocean, but also from the Indian Ocean. The purpose of the seawater measurements was to determine the distribution of bomb-produced radiocarbon in the surface water of the Pacific and Indian Oceans, the sub-surface penetration of bomb 14C, the change in 14C/12C ratios with depth, and thus the rate of uptake of bomb 14C by the oceans. This project was the basis of the author's doctoral dissertation (Linick, 1975).
Tartu Radiocarbon Dates VII
Authors: Liiva Arvi , Ekman Ilpo , Rinne Toivo
Published: July 2016

The present list contains dates of geologic samples from the southern part of the Karelian ASSR and partly from the northwest Leningrad Region, USSR, made in 1969-1975.
Geomagnetic Strength Over the Last 50,000 Years and Changes in Atmospheric 14C Concentration: Emerging Trends
Authors: Barbetti Mike
Published: July 2016

Palaeomagnetic field strength measurements for the last 50,000 years are summarized. The period before ~12,000 yr bp is characterized by low dipole moments, but high values are associated with the Lake Mungo polarity excursion between ~32,000 and ~28,000 yr bp. The variation since 12,000 yr bp, based on new results from Australia and published data from the Northern Hemisphere has a quasi-cyclic appearance with maxima at ~10,000 and ~3500 yr bp. The geomagnetic record is used to predict variations in atmospheric 14C concentration, and the results are compared with independent comparisons between 14C and other dating methods. Long-term variations in the 14C time-scale are readily explained by known geomagnetic changes.
The Radiocarbon Record in Tree Rings of the Last 8000 Years
Authors: Suess Hans E
Published: July 2016

It has become generally accepted during the last year that14C fluctuations, the so-called “wiggles”, observed in wood, dated by its tree rings, do indeed exist. Furthermore the La Jolla measurements show that apart from experimental noise, they do not represent random red noise, but characteristic, recurring features. In 1971, Houtermans found indications for the existence of cyclic components and recent Fourier analyses of all the available data by Neftel and Hartwig show a 200-year component. Cyclic oscillations with other periods appear to be present during limited time intervals. The character of the oscillations is not harmonic. The time derivative of many fluctuations is remarkably constant and such that the14C rises by 1 percent in about 20 years and decreases by 1 percent in slightly more than twice that length of time. The properties of the overall radiocarbon record have to be considered in attempts to explain the variations in terms of variations of the cosmic ray-production rate and changes of the geochemical distribution of radiocarbon.
Natural Processes and Time Fluctuations in the Radiocarbon Concentration of the Atmosphere
Authors: Dergachev V A , Kocharov G E
Published: July 2016

The concentration of radiocarbon in the earth's atmosphere is used to analyze the complex of problems associated with the study of various astrophysical, geophysical, and geochemical phenomena within the framework of the All-Union problem of Astrophysical Phenomena and Radiocarbon. Effects of the supernovae explosions, solar activity, geomagnetic field and climatic changes in the 14C level in tree-rings are considered.
Computer-Matched Radiocarbon Dates of Floating Tree-Ring Series
Authors: Kruse H H , Linick T W , Suess H E , Becker Bernd
Published: July 2016

The absolute time of growth of a floating tree-ring series is determined by computer, by first fitting a curve to the14C ages of tree-ring dated wood and then by matching the14C ages of the floating tree-ring series to that curve. The results obtained by this matching procedure are given here for five floating European oak chronologies for which14C dates have been published previously by Suess (1978). Three of these five floating series have been linked together dendrochronologically. There now remain three floating series covering a 4000-year time span from 4820 BC to 830 BC. Their14C dates, matched by computer to the bristlecone pine chronology, provide a possibility of obtaining precise ages of oak wood series from Neolithic sites in Switzerland and South Germany by dendrochronologically cross-dating with the calibrated master chronologies.
Possibility of Climatically Induced Variations in the 14C and 13C Enrichment Patterns as Recorded by a 300-Year-Old Norwegian Pine
Authors: Harkness D D , Miller B F
Published: July 2016

The secular patterns of Δ and δ13C measured in wood cellulose are compared with a palaeotemperature index published for the immediate growth region. 14C enrichment shows an overall decrease of ca 20% (Δ) during the 18th and 19th centuries with shorter term (decade) variations superimposed on the general trend. Measured Δ values correlate significantly with the average mean summer temperatures and indicate a linear coefficient of ca − 10.2% °C–1. Short-term variations in the natural concentration of 14C which are closely related to climatic change may reflect the latitudinal dependence for atmospheric mixing.

The secular trend in δ13C covers a range of 2% but variations of this magnitude reflect influences other than those directly associated with climatic change, eg, possible assimilation of recycled biospheric CO2 during early life and post AD 1850 anthropogenic effects. No evidence was found to suggest a significant correlation between δ13C and the mean atmospheric temperature during summer growth periods.
Low-Level Gas Proportional Counting in An Underground Laboratory
Authors: Loosli H H , Heimann Martin , Oeschger Hans
Published: July 2016

Results of measurements in an underground laboratory, 70m of water equivalent below surface, are given. Background values of proportional gas counters with volumes between 16cc and 1.5L are lower by a factor of 2—4.5 compared to the values in the previously used laboratory (7m w.e.). High counting gas pressures, up to 5 at CH4 and up to 36 at P-10, enable the use of relatively small counters with correspondingly small background contributions from the walls. A separation of the residual background into different components is attempted, distinguishing a pressure dependent volume effect and surface correlated contributions. It can be shown that the selection of radioactively pure counter construction material is very important for a good low level counting system.
A Possible Source of Error in 14C Dates: Volcanic Emanations (Examples from the Monte Amiata District, Provinces of Grosseto and Sienna, Italy)
Authors: Saupé Francis , Strappa Osvaldo , Coppens René , Guillet Bernard , Jaegy Robert
Published: July 2016

Wood from regular timbering of a shallow seated mine in Tuscany gave 14C ages of 5730 ± 100 years BP, much too old to be attributed to one of the known civilizations of Italy. This mine is located in a region of declining volcanic activity, noticeable especially through numerous emanations (natural or incidentally induced by drillings). It was suspected that the analyzed wood had grown in an environment where the normal atmosphere had been diluted by volcanic emanations. To check this hypothesis, living plants (trees, bushes and reeds) and volcanic emanations have been sampled and their 14C content measured. All present day plants are depleted in 14C, giving a fictitious age different from 0 (1805, 1820, 2540, 4350 years BP). Of the gaseous emanations sampled, two have a high pressure and show virtually no 14C (>41,000 years BP). Two others have a pressure close to atmospheric, and small amounts of 14C were introduced by atmospheric contamination (22,570 and 30,580 years BP).

Conclusion: plants grown in the vicinity of volcanic emanations have 14C activities that are too low because of a natural 14C dilution and yield anomalously high ages. The δ13C values obtained for two of these plants (—27.4‰ and —23.7‰) are close to the average for plants in general (—25‰), whereas the CO2 of mofettes is heavier than atmospheric CO2.
Modeling the Carbon System
Authors: Broecker Wallace S , Peng Tsung-Hung , Engh Richard
Published: July 2016

Claims that forest cutting during the last few decades has contributed significantly to the buildup in atmospheric CO2 have cast doubt on the validity of models used to estimate CO2 uptake by the ocean. In this paper we review the existing models and conclude that the box-diffusion model of Oeschger and his co-workers provides an excellent fit to the average distributions of natural and bomb-produced radiocarbon. We also take the first steps toward a more detailed ocean model which takes into account upwelling in the equatorial zone and deep water formation in the polar zone. The model is calibrated using the distribution of bomb-produced and cosmic ray-produced radiocarbon in the ocean. Preliminary calculations indicate that the fossil fuel CO2 uptake by this model will be greater than that by the box-diffusion model of Oeschger and others (1975) but not great enough to accommodate a significant decline in the mass of the terrestrial biosphere over the past two decades.
Bomb-Produced Carbon-14 in the Surface Water of the Pacific Ocean
Authors: Linick Timothy W
Published: July 2016

The distribution of 14C concentrations in the dissolved inorganic carbon in the surface waters of the Pacific Ocean is shown to have a primarily latitudinal pattern with Δ14C maxima at mid-latitudes in both hemispheres and a minimum at the equator. Oceanographic causes of this phenomenon are discussed.
Transfer of Bomb 14C to the Ocean Surface
Authors: Nydal Reidar , Lövseth Knut , Skogseth Fred H
Published: July 2016

Additional 14C data from the atmosphere and ocean have been provided since the ninth 14C conference in 1976. At the moment, one sampling station in the troposphere in each hemisphere seems to give sufficient accuracy for exchange studies. The 14C concentration in the troposphere in December 1978 constituted a mean value of 30 ± 1 percent (Δ14C) above normal level, a concentration that has been reduced to about one half during 12 years. 14C measurements have been performed with intervals of 1 to 4 months in the surface water of the Atlantic, Pacific, and Indian Oceans. In addition to the 14C data observed, the salinity and temperature are also measured. Because of earlier objections against storing sea water in steel drums on board ships for months before treatment, the CO2 has now been flushed out immediately after collection. The reliability of previous measurements has been confirmed with 10 parallel samples. 14C concentration in ocean surface on each location shows some seasonal variation due to variable exchange of water with deeper layers.
On the 14C to Tritium Relationship in the North Atlantic Ocean
Authors: Roether Wolfgang , Münnich Karl-Otto , Schoch Hildegard
Published: July 2016

Nuclear-weapon produced 14C (or bomb 14C) in the ocean can be traced by simultaneous tritium observations. Data are presented on the general relationship of bomb 14C and tritium in the North Atlantic. For the period 1965 to 1973, the excess 14C to tritium ratios in the surface water vary, systematically, over a factor of 10: the ratios monotonically increase with time, and decrease with latitude, particularly so for the later observations. The sub-surface water ratios show that the mid- and low-latitude water below about the 15° C isothermal horizon (~500m depth) originates from higher northern latitudes, rather than being renewed by local vertical mixing. It is further shown that in the North Atlantic, bomb 14C did not penetrate beyond the horizon where the presently observed 14C concentration is Δ14C = —75‰. Observed concentrations up to about —40‰ can be corrected for a bomb contribution if the tritium concentration is known because the bomb 14C to tritium concentration ratio is rather uniform in this range. A surface water 14C concentration versus time curve is presented for the period since 1957. This curve is based on a North Atlantic mixing model and is fitted to the 14C observations. Making use of a previously published tritium versus time curve obtained by the same model, a time curve for the average excess 14C to tritium ratio in North Atlantic surface water is given. This curve reproduces the observations well. The presented data and theoretical curves show the usefulness of simultaneous 14C and tritium observations for mixing studies and to provide corrections for bomb 14C in sub-surface 14C data in the North Atlantic.
Ages of Charcoal Samples of Geomorphologic Interest in Northeast Hungary
Authors: Csongor Eva , Borsy Zoltán , Szabô Ilona
Published: July 2016

There are extended wind-blown sand territories in the northeastern part of the Great Hungarian Plain. Wind-blown sand migration periods were distineuished by means of radiocarbon age determination of charcoal samples found in the same type of a thin soil layer of chernozem character in different sand dune exposures. The ages of the samples were determined by proportional counter, and are around 12 000 years BP. This thin fossil soil layer, which is regionally spread in the northeast Hungarian wind-blown sand areas, presents a chronological mark between the blown sand forms evolved in the last glacial period and in the Holocene.
Carbon Isotope Measurement as An Index of Soil Development
Authors: Ladyman S J , Harkness D D
Published: July 2016

14C and 13C enrichment values are reported for a series of surface soil profiles which represent the progressive transition from mor to mull humus induced by birch (Betula pendula) colonization.

Variations in Δ and δ13C, which range between 85 to 154‰ modern and −28.1 to −25.3‰ (PDB), respectively, reflect changes in the rate and mode of organic decomposition. The most marked alterations in soil character occur over the first few decades following the introduction of birch, with clear isotopic evidence for the deeper penetration and accelerated mineralization of organic material.
Radiocarbon Dating of Pleistocene Bone: Toward Criteria for the Selection of Samples
Authors: Taylor R E
Published: July 2016

Amino acid composition data and stable isotope ratios (14N, D, and13C) are being evaluated as sources of information to indicate the presence of non-indigenous organics in bone samples intended for14C analyses. The study is being conducted in the context of the planned measurement of Pleistocene bone samples by a high energy mass spectrometric14C detection system.
Isotopic Fractionation of Norwegian Materials for Radiocarbon Dating
Authors: Gulliksen Steinar
Published: July 2016

To improve reporting of radiocarbon dates, Stuiver and Polach (1977) recommend that reported standard errors should include the error in the applied δ13C value, and suggest estimated mean values for δ13C to be applied when not measured. Based on δ13C data for ca 250 samples measured during 1975-1979, mean values for different materials dated by the Trondheim radiocarbon laboratory have been compiled. All material is from Norway and Svalbard (marine bone collagen). For peat, gyttja, and terrestrial bone material, δ13C should be measured to obtain optimal precision in the dates. For shell, wood, charcoal, and marine bones, the standard error in an estimated δ13C value will only increase uncertainty of a date from ±50 years to ca ±55 years.
W F Libby and the Archaeologists, 1946-1948
Authors: Marlowe Greg
Published: July 2016

Archaeologists began to participate in cross-disciplinary endeavors in the 1930's, albeit on a very limited basis. The passage of time found members of that discipline unprepared for collaboration with physical scientists when W F Libby announced the development of the radiocarbon dating method. Libby proposed to apply to

archeologic and geologic samples techniques based on ideas that were completely foreign to archeology …. The initial reactions of archeologists were sometimes amusing but more often significant, for they led to the foundation and emergence of the radiocarbon chronology that has so profoundly affected our understanding of prehistory (Johnson, 1967, p 165).

To date, our historical knowledge about the nature, function, and impact of the early (1946-1948) relations between Libby and American archaeologists has come to us in the form of published anecdotes, many of which contain inaccurate information. The author's access to W F Libby's private 14C correspondence, combined with data obtained from interviews with some of the principal participants throughout this period, offers many new or different insights into the nascent years of radiocarbon dating. When, and under what unexpected cricumstances, did Libby first encounter representatives of the achaeologic community? What strategies were employed to facilitate diffusion of knowledge about 14C dating across disciplinary boundaries? How did archaeologists respond to the introduction or “intrusion” into their field of Libby's radioactive age-measurement tool?
Sharp Laboratories Measurements I
Authors: Ellis John G. , Sharp Rodman A.
Published: July 2016

Radiocarbon measurements were begun at Sharp Laboratories in the spring of 1962 with the construction of a complete C14 dating laboratory. This first system used the method described by Fairhall, Schell, and Takashima (1961) for the conversion of CO2 to methane via ruthenium catalyst. This system proved to be fast and reliable, giving overall yields of solid sample to counting gas of better than 90% for the total conversion and purification (the conversion yield of CO2 to methane is quantitative). The detector in present use is 2 L, with construction materials consisting solely of O.F.H.C. copper, teflon, and epoxy resin. The shield consists of 4 in. of high purity lead (specially prepared), 4 in. of borated hydrogenous neutron moderator, a guard counter (cosmic ray detector), and 1 in. of ultra pure mercury. The gross to net ratio obtained with this system averages about 53. The background, for P in cm methane pressure, is:

Background = 3.95 ± .008 + .00705P
Monaco Radiocarbon Measurements I
Authors: Thommeret J. , Rapaire J. L.
Published: July 2016

Created in 1961, the C14 dating laboratory of the Centre Scientifique de Monaco (founded by H. S. H. Prince Rainier III in 1960) made its first dating measurements in 1962.
Saclay Natural Radiocarbon Measurements I
Authors: Delibrias G. , Guillier M. T. , Labeyrie J.
Published: July 2016

The following list shows the age measurements carried out at Saclay by the Service d'Electronique Physique, using the C14 method.

The apparatus employed was completed and calibrated in 1956 and the first tests were performed during the same year. The counting unit is a 1.2 L stainless steel proportional counter and the filling gas is pure CO2 at 74 cm Hg pressure. The shield consists of 20 cm of lead, 10 cm of iron, a coincidence ring and 2 cm of bismuth. The background is 4.86 ± 0.05 counts/min. (Error is ± σ, the duration of each counting being 24 hours.) Final purification is performed by adsorption of CO2 on alumina at low temperature, followed by desorption at room temperature; this has proved particularly effective and gives a very good filling gas. Technique was described in detail previously by the authors (Perquis, Delibrias, and David, 1956; Delibrias and Perquis, 1958).

As a modern carbon standard we first used wood taken from the 1930 to 1945 rings of a large Douglas fir; this standard gave a net count of 6.02 counts/min. This activity, taking into account a 2% Suess-effect for this wood, was found to be 95% of the activity of the NBS oxalic-acid standard, measured in the same counter.

The NBS standard has been adopted by this laboratory since January 1961, and values given here are calculated from this new standard.

Measurements listed are dates obtained from 1956 through 1962. No reports are given here from other types of measurements carried out at Saclay, such as: (1) C14 content of wild plants growing in the vicinity of nuclear reactors; (2) measurement of C14 in blood proteins of workers of the radioactive-tracers industry; (3) Spallation cross-sections for C14 production in oxygen and iron by high energy protons; (4) C14 content of meteorites.
Ohio Wesleyan University Natural Radiocarbon Measurements I
Authors: Ogden J. Gordon , Hay Ruth J.
Published: July 2016

Installation of a Sharp CDL-14 Carbon-Dating Laboratory was completed at Ohio Wesleyan University in June, 1962. The unit includes a sample conversion system constructed by Radiochemistry, Incorporated for the conversion of carbonaceous samples to the counting gas, methane. Counting equipment consists of a modified Sharp Low Beta system with a 6kv power supply and dual printout registers which automatically blank the counting circuits for 0.1 min for each 100-min printout. The detector has a sensitive volume of 0.5 L and is housed in a shield consisting of 8 in. of lead, 1 in. of steel, and 1 in. of mercury. Anticoincidence is provided by a cylindrical 2-L detector containing 16 anodes and filled with petroleum-generated methane to a pressure of 96 cm Hg.
Isotopes' Radiocarbon Measurements VI
Authors: Buckley James D. , Trautman Milton A. , Willis Eric H.
Published: July 2016

This list presents dates on a portion of the samples measured at ISOTOPES since publication of Isotopes V, and for previously analyzed samples for which complete sample data are now available.

Samples were analyzed by gas proportional counting of carbon dioxide at 3 atm pressure in counters of 1 1. volume. Each sample was assayed twice, in different counters and on different days.

Procedures employed in sample preparation and age calculations have been described previously (Isotopes V).
University of Texas at Austin Radiocarbon Dates VI
Authors: Valastro S. , Davis E. Mott , Rightmire Craig T.
Published: July 2016

This laboratory is now a part of the Bureau of Economic Geology, The University of Texas at Austin. The present list reports C14 measurements made in dating projects completed in the year ending November, 1967, and some measurements for projects still in progress. Age calculations are based on C14 half-life of 5568 yr and a modern standard of 95% of NBS oxalic acid. The deviations reported are based on the counting statistics of the sample, background, and modern, and are ± 1σ except that when the sample count approaches either the modern or the background, 2σ limits are reported. The laboratory continues to use liquid scintillation counting of benzene, using Li2C2 and vanadium activated catalyst in preparation, as described in Texas IV and earlier lists. Chemical yields now average 85%.

Rightmire's caliche dating (done for an M.A. thesis in the Dept. of Geol.) is the principal project reported in this list; in addition to the research he prepared the samples in our laboratory and wrote the statements which accompany the list. Valastro is in charge of all technical operations in the laboratory, and he and Davis share the administrative responsibilities. Davis, who handles sample screening (with the aid of an Advisory Committee) and archaeological appraisal, compiled the list.
Geological Institute Radiocarbon Dates II
Authors: Cherdyntsev V. V. , Alekseyev V. A. , Kind N. V. , Forova V. S. , Zavel'Skiy F. S. , Sulerzhitskiy L. D. , Forsenkova I. V.
Published: July 2016

Charcoal. Pavlov campsite [48° 50′ N Lat, 16° 25′ E Long], Czechoslovakia. Archaeologic [sic] age is beginning of Wörm III. Other determinations of charcoal from same campsite are: 24,800 ± 150 yr (GRO-1325, de Vries, 1958) and 26,400 ± 230 yr (GRO-1242, ibid.), which agree with our date. Subm. by A. N. Rogachev; [no date given (E.M.S.)].
University of Wisconsin Radiocarbon Dates V
Authors: Bender Margaret M. , Bryson Reid A. , Baerreis David A.
Published: July 2016

The radiocarbon dates obtained since August, 1967 are included in this report. The procedures followed have been described previously (Wisconsin II).

The reported dates have been calculated using 5568 as the half-life of C14, 1950 as the reference year. Samples are run at least once in each of two counters at 3 atm pressure for a minimum of 15,000 counts. The standard deviation quoted includes only the 1σ of the counting statistics of background, sample, and standard counts.
Nancy Natural Radiocarbon Measurements II
Authors: Hassko B. , Guillet B. , Coppens R.
Published: July 2016

The following list includes a selected number of measurements made during 1967-1968 in the Natural Radiocarbon Laboratory of the Centre de Recherches Radiogéologiques de Nancy. This list is a continuation of Nancy Natural Radiocarbon Measurements I (Radiocarbon, 1968, v. 10, p. 119-123). The dating method, counting technique, and equipment are described in that list. All measurements were made in a proportional counter with a capacity of 1.16 L, normally filled with CO2 under a pressure of 736 mm Hg. Ages are calculated using a C14 half-life of 5568 yrs with 1950 as reference yr. Modern standard used following samples Ny-118 is 95% of NBS oxalic acid activity. The SC14 mentioned later in the date list are calculated according to Broecker and Olson (1959).
University of Tokyo Radiocarbon Measurements II
Authors: Sato Jun , Sato Tomoko , Otomori Yasuko , Suzuki Hisashi
Published: July 2016

Radiocarbon measurements in the list below were made during the period from Sept. 1967 to Aug. 1968. Our measuring system is based on acetylene counting in an Oeschger-Houtermans-type proportional counter (1 L) at a pressure of I atm. All data are based on duplicated measurements. For calculation of ages, 95% activity of NBS oxalic acid is used as the modern standard and the value of 5570 ± 30 years is used for the half-life of C14. Details of procedures are given in the previous report (Radiocarbon, 1968, v. 10, p. 144-148).
University of Miami Radiocarbon Dates XIX
Authors: Johnson R A , Stipp J J
Published: July 2016

The following radiocarbon dates are a partial list of samples measured for a variety of projects and materials since January 1980. Chemical and counting procedures remain the same as indicated in R v 20, p 274-282.
A Semi-Automated Bone Pretreatment System and the Pretreatment of Older and Contaminated Samples
Authors: Law I A , Hedges R E M
Published: July 2016

A semi-automated continuous-flow system used to process archaeological bone to purified gelatin or amino acids for 14C dating is described. Powdered bone is retained in flow cells specifically designed to permit the sequential leaching of the bone with acid, alkali and water. Crude collagen obtained by this process is gelatinized, and than either purified directly using a macroporous cation exchange resin (BioRad AGMP-50), or hydrolyzed and the amino acids desalted on BioRad 50W-X8 resin. When compared with previous methods used by the laboratory, the new method allows more samples to be treated to a higher degree of purification. Examples of dates obtained on “standard” bones are presented, and confirm that no contamination is introduced from the components used in the new process.
Fast 14C Sample Preparation of Organic Material
Authors: Dörr Helmut , Kromer Bernd , Münnich Karl Otto
Published: July 2016

A fast 14C sample preparation technique for organic material in conventional 14C counting is described. The basic difference from conventional preparation is oxidation of the organic substances in a closed system under an oxygen pressure of ca 10 bars. After the explosion-like combustion, the reaction products SO2 and NO2 are oxidized immediately to SO4
2-and NO3
− and precipitated on the wall of the reaction vessel. The residual gas mixture is passed first through a cold trap at −78° to remove water vapor and then through an activated charcoal column at 0° for purification. CO2 is removed from the remaining O2−CO2 gas mixture in a LN2 trap at a pressure of ≃ 100mbar. With this method sample preparation time is reduced from ca 10 hr to ca 1 hr. The efficiency and reproducibility of the procedure is shown with 14C and 13C measurements of a sugar-carbon standard. The results obtained by the new technique agree well with conventionally prepared wood and bone samples.
Liquid Scintillation 14C Spectrometry: Errors and Assurances
Authors: Polach Henry
Published: July 2016

Liquid scintillation (LS) 14C spectrometry, using ultra low-level, high-efficiency and resolution α and β particle detection equipment is seen as an excellent tool supporting future 14C radiometry. Modern technology ensures electronic excellence: high-precision, small-sample (100mg) dating ability, flexibility of use for the detection of α and β particle emitting radioisotopes at and below natural abundance levels. Multiple applications to environmental research, supported by elegant software and commercial availability, are its attributes. However, mastering the new technology takes time as lessons learned in gas-proportional 14C radiometry and high-background counting are not directly applicable to ultra low-level 14C LS spectrometry using benzene as the counting medium. That discordant results can be obtained by any technique based on physical measurement is well established. This is demonstrated for 14C age determination by reference to an international cross-check organized by the University of Glasgow. Reasons for aberrations are explored and the question is raised if it is not timely to introduce the type of quality assurance practiced by other analytical disciplines. Better results will not only serve the daters and users but will generally enhance the value of worldwide 14C research.
Performance of the Packard 2000 CA/LL and 2250 CA/XL Liquid Scintillation Counters for 14C Dating
Authors: Cook G T , Harkness D D , Anderson Robert
Published: July 2016

Results are presented on the comparative characteristics of the Packard 2000 CA/LL liquid scintillation counter with and without the low-level option on line. An initial performance assessment using 14C labeled benzene with butyl-PBD as the scintillant revealed that although the background count rate decreased by approximately a factor of 3 using the low-level option, a substantial decrease in efficiency was also observed. However, subsequent investigations have indicated that, by careful manipulation of both scintillant composition and concentration, this loss in efficiency can largely be overcome with little or no concurrent increase in background count rate. The introduction of an active vial sample holder and a new light-guide system proved to be significant advances on the standard 2000 CA/LL.
Design and Preparation of Samples for the International Collaborative Study
Authors: Harkness D D , Cook G T , Miller B F , Scott E M , Baxter M S
Published: July 2016

Sample materials issued to participants in the interlaboratory calibration exercise are defined and in context of their intended interpretational significance. Preparation of the benzene and calcium carbonate standards as issued for stage 1 is described in detail; likewise, the source and pretreatment/extraction of the environmental samples dispatched for stages 2 and 3.
An Interim Progress Report on Stages 1 and 2 of the International Collaborative Program
Authors: Scott E M , Aitchison T C , Harkness D D , Baxter M S , Cook G T
Published: July 2016

We report in this paper on a preliminary analysis of Stages 1 and 2 of the International Collaborative program. We have chosen to concentrate on the internal and external consistencies of the participating laboratories. The two stages so far completed have dealt only with the processes of sample synthesis and counting, and results indicate that the major component of variability lies in the counting process. Outlying laboratories are observed at each stage. A third stage is in progress which will allow an assessment of any further variability due to sample pretreatment. With the inclusion of duplicate samples in each stage, we are able to report that laboratories are remarkably consistent internally, ie, the differences between duplicates generally agree with the laboratory's claimed precision.
The Atmospheric δ13C Record as Derived from 56 Pinyon Trees at 14 Sites in the Southwestern United States
Authors: Leavitt S W , Long Austin
Published: July 2016

We have developed a master δ13C chronology from 14 pinyon pine sites in 6 states of the southwestern U S. Two of the individual isotopic chronologies, reported here for the first time, and 10 of those previously reported (Leavitt & Long, 1986; 1988) are from sites where cores from 4 trees were pooled prior to analysis, and the other 2 are merged from groups of 4 single-tree chronologies (sites) developed in an earlier phase of research (Leavitt & Long, 1985). Regressions of first differences of ring-width indices and δ13C values from each site were used to “correct” individual δ13C chronologies for climate effects which appear primarily related to high-frequency δ13C fluctuations, many of which are common among sites. These climate-corrected chronologies were normalized as deviations from their respective 1800–1849 δ13C means, and these normalized chronologies were averaged into the master. The overall δ13C drop from 1600 to the present is ca 1.2–1.4, consistent with recent ice-core data showing a drop of 1.14 ± 0.15% from 1740 to present (Friedli et al, 1986). However, the δ13C decline in the late 19th and early 20th centuries is greater in the pinyon chronology than that of the ice cores, thus supporting a greater biospheric CO2 input to the atmosphere than that indicated in the ice-core data.
Bomb 14C in the Indian Ocean Measured by Accelerator Mass Spectrometry: Oceanographic Implications
Authors: Bard Edouard , Arnold Maurice , Toggweiler J R , Maurice Pierre , Duplessy Jean-Claude
Published: July 2016

AMS 14C measurements on samples collected in the tropical-equatorial Indian Ocean during the INDIGO program (leg II, 1986) are presented and compared with β-counting results obtained under both INDIGO program and GEOSECS expedition in the Indian Ocean (1978). The most significant observation is a doubling of the bomb-14C inventory and mean penetration depth in the equatorial zone. Based on hydrologic considerations, two hypotheses can be proposed: 1) direct influx of Pacific mid-latitude waters through the Indonesian archipelago and 2) advection and/or mixing with Mode Water from the southern gyre of the Indian Ocean. Results obtained with a general circulation model of the ocean suggest that the influx from the Pacific is important in the upper 300m and that below 500m the bomb-14C budget is dominated by Mode Water advection.
Aridity in Equatorial Africa During the Last 225,000 Years: A Record of Opal Phytoliths/Freshwater Diatoms From the Zaire (Congo) Deep-Sea Fan (Northeast Angola Basin)
Authors: Jansen J H F , Alderliesten C , Houston C M , de Jong A F M , Van Der Borg K , Van Iperen J M
Published: July 2016

Maps of accumulation rates of freshwater diatoms and opal phytoliths in the surface sediments of the Zaire fan show that both types of microfossils were supplied to the ocean floor by the Zaire River, and that opal phytoliths also have a southern source, probably the region of the Namibian desert. The PhFD ratio, of opal phytoliths to freshwater diatoms, can be regarded as an aridity index for equatorial Africa, and probably for large parts of the central and southern Atlantic. In two cores, the record of the PhFD ratio indicates humidity ca 225–190 ka BP, aridity 190–135 ka BP with maxima ca 170 and 140 ka BP and a humid excursion 150 ka BP, an increase in humidity 115 ka BP, a less humid period 90–30 ka BP, more humidity ca 30–17 ka BP with possibly more arid intervals ca 22.5 and 20 ka bp. In general, glacial (sub) stages were more arid and interglacial (sub) stages more humid. For the last 20 ka, the PhFD ratio corresponds closely with the known climatic events in tropical Africa.
Spallogenic 14C in High-Altitude Rocks and in Antarctic Meteorites
Authors: Jull A J T , Donahue D J , Linick T W , Wilson G C
Published: July 2016

14C in high-altitude rocks and in Antarctic meteorites of long terrestrial age has been found at levels consistent with in-situ production by cosmic rays. Levels of 0.2–0.59 dpm/kg (or 1.0–2.6 × 106
14C/g) are found in high-altitude samples ranging from 3300 to 5460m. Similar values are observed in Antarctic meteorites that have been dated by 81Kr by Freundel, Schultz & Reedy (1986) as over 100 kyr old.
Tritium and 14C in Tree Rings of the Last Three Decades
Authors: Kozák Kristóf , Obelić Bogomil , Horvatinčić Nada
Published: July 2016

Tree rings spanning the past three decades were collected from Picea spp trees grown in Matra, northern Hungary. Cellulose was prepared from the wood and samples were separately combusted for tritium and 14C analyses. Methane was synthesized from CO2 obtained by sample combustion via catalytic reaction with tritium-free hydrogen. 14C activity was measured by proportional counter. The exchangeable tritium was removed from cellulose samples used for tritium analysis. Water samples produced by combustion were measured by liquid scintillation counting. The distribution of tritium and 14C activities in tree rings are shown for years 1956–1986. Results are compared with published data on global-scale distribution of 14C and HTO. A comparison of tritium activity in precipitation and wine samples from the same region is presented.
Determination of 14C in Alcoholic Beverages
Authors: Schönhofer Franz
Published: July 2016

A simple and quick method for the determination of 14C in ethanol has been developed, using an ultra low-level liquid scintillation counter. I have studied factors influencing the lower limit of detection and have shown that liquor can be measured directly without pretreatment. Results of measurements on Austrian wines are presented and compared with results obtained from tritium measurements. The applicability and limitations of the results to age determination are discussed.
Calibration of Radiocarbon Ages by Computer
Authors: Van Der Plicht Johannes , Mook W G
Published: July 2016

A PC-based computer program for automatic calibration of 14C dates has been developed in Turbo-Pascal (version 4.0). It transforms the Gaussian 14C dating result on the 3σ level into a real calendar age distribution. It uses as a calibration curve a spline function, generated along the calibration data points as published in the Radiocarbon Calibration Issue. Special versions of the code can average several 14C dates into one calibrated result, generate smoothed curves by a moving average procedure and perform wiggle matching.
Improvement of the Procedure for Probabilistic Calibration of Radiocarbon Dates
Authors: Pazdur Mieczysław F , Michczyńska Danuta J
Published: July 2016

A set of computer procedures for probabilistic calibration of 14C dates was developed at the Gliwice Radiocarbon Laboratory for the IBM PC compatible microcomputer. The program comprises three main options: 1) calibration of a single 14C date, 2) calibration of a set of arbitrary dates, 3) calibration of a set of related dates. Results of calibration are presented in the form of graphs and numeric data, including tables of selected quantiles and inter-quantile ranges of resulting probability distribution of cal age. In this paper, we present the aims of the program, with a short description of its structure, show examples of working with output data in terms of expected archaeological application, and consider the possibility of standardization of calibration procedures.
Groundwater Analysis of Environmental Carbon and Other Isotopes From the Jakarta Basin Aquifer, Indonesia
Authors: Geyh M A , Söfner Bernd
Published: July 2016

Groundwater of the Jakarta Basin aquifer is heavily exploited for drinking water. As a result, the piezometric head has dropped dramatically. Extensive hydrogeologic and numeric model studies have been made to find a reliable basis for managing available groundwater resources. Environmental carbon (14C, 13C) and other isotope analyses (18O, 2H, 3H) were made. Two sampling strategies were employed, which show that using well-defined and representative sampling sites, no matter how few, is the only way to obtain reliable geoscientific information. Large quantities of data from randomly distributed samples of uncertain origin is not recommended.
Investigating Gas-Water-Rock Carbon Isotope Exchange in the Field
Authors: Eichinger Lorenz
Published: July 2016

Extensive investigations of isotope content and hydrochemical parameters in soil gas, soil material, groundwater and seepage water from a Quaternary aquifer show a good correlation between 14C concentration of the groundwater and its mean residence time in the unsaturated zone. The initial 14C concentration varies between 100 and 50% modern. It decreases through solution and dissolution of carbonates to 50% of the 14C concentration of atmospheric CO2.
A Critical Review of Radiocarbon Dating of a Norse Settlement at L'Anse Aux Meadows, Newfoundland Canada
Authors: Nydal Reidar
Published: July 2016

Recent progress in high-precision calibrations of radiocarbon dates has led to evaluations of earlier research. This has been the case with dates from the Norse settlement at L'Anse aux Meadows which was discovered by Helge Ingstad in 1960. The most problematic feature of this series up to now was the use of sample material which partly derived from driftwood. The present paper concludes that charcoal from this site demonstrated no greater errors than normal from other settlement sites. With an assumed total systematic error of 30 ± 20 years, as a mean for various tree rings, the calibrated age range of L'Anse aux Meadows is AD 975–1020. This agrees well with the assumed historical age of ca AD 1000, a result which has also been recently corroborated by high-precision accelerator dating at the University of Toronto.
The Radiocarbon Data Base at Rudjer Bošković Institute Radiocarbon Laboratory
Authors: Obelić Bogomil
Published: July 2016

A multidisciplinary radiocarbon data base system written in dBASE III PLUS which follows the recommendations of the International Database Commission and specific requirements of our laboratory is described. The system updates, stores and maintains records and retrieves data according to specific key-words.
International Workshop of Intercomparison of Radiocarbon Laboratories: Welcome - The Aims - The Programme
Authors: Baxter M S
Published: July 2016

On behalf of the organising committee, it is a great pleasure to welcome you all to this 14C workshop and indeed to Scotland. The organising committee has already indicated its ability by arranging sunshine for a place and time in which horizontal rain is more common. We plan to build on this initial success by having an outstanding week of good science and pleasant social activity. Scientifically, we have the opportunity firstly to look back and review previous research on the accuracy and precision of 14C dates. Then we will hear and discuss some important new results from the final stage of the present international intercomparison study. Finally, we will discuss and plan mechanisms and procedures by which, in future, we can improve our general level of performance. Paralleling this and of equal if not more importance, we have arranged a social programme which we hope will give us the opportunity to eat and drink well together, see some of the country, get to know each other better and discuss our science informally. So our hopes are high and our welcome sincere.
Radiocarbon Dating Reproducibility at the Museo de La Plata Radiocarbon Laboratory
Authors: Figini Anibal , Huarte Roberto , Carbonari Jorge
Published: July 2016

We discuss here the variability, for our laboratory, in counting for radiocarbon dating of replicate measurements of background and secondary modern standard, duplicate measurements of samples provided by the International Collaborative Study, and replicate measurements of the dilution of the14C-labeled benzene standard. The variability in the measurements of the International Collaborative Study samples suggest the existence of systematic bias.
Statistical Quality Control Graphs in Radiocarbon Dating
Authors: Switsur Roy
Published: July 2016

I describe here the establishment and use of statistical control graphs based on the analysis of variance for monitoring the stability of operation of radiocarbon dating counting systems.
Scintillation Cocktail Optimization for 14C Dating Using the Packard 2000CA/LL and 2260XL
Authors: Anderson Robert , Cook G T
Published: July 2016

In terms of both quenching and, in particular, counting efficiency, scintillation counters employing burst counting circuitry are sensitive to changes in scintillant concentration. Our research demonstrates that there are plateau regions where neither parameter is significantly influenced by moderate changes in a cocktail containing butyl - PBD and bis - MSB. One of these, consisting of butyl - PBD 2.8mg.g-1 and bis - MSB 3mg.g-1 of benzene is recommended for these counters, as it enables open window counting efficiencies of ca 90% while exhibiting optimal resistance to quenching. A method for accurate dispensing of such small weights is also described.
A Late Quaternary Stratigraphic Framework for Eastern Mediterranean Sapropel S1 Based on AMS 14C Dates and Stable Oxygen Isotopes
Authors: Troelstra S R , Ganssen G M , van der Borg Klaas , de Jong A F M
Published: July 2016

Detailed stable oxygen isotope analyses coupled with AMS 14C measurements on an eastern Mediterranean sapropel S1 sequence indicate that adverse bottom conditions persisted for ca 8000 years. AMS dates on additional sequences show that complete bottom anoxia lasted for 300-800 years. The S1 event is not synchronous throughout the eastern Mediterranean, but started earlier in the deeper parts of the basin.
British Museum Natural Radiocarbon Measurements XXII
Authors: Ambers Janet , Matthews Keith , Bowman Sheridan
Published: July 2016

The following list consists of dates, obtained by liquid scintillation counting of benzene, for archaeologic samples mostly measured between June 1987 and October 1989.

Charcoal and grain samples were pretreated with 1M HCl followed by washing in water and, where considered necessary, with dilute alkali for the removal of humic acids. Wood samples were treated either in the same way, or, where large enough, were reduced to cellulose by the action of chlorine dioxide producedin situ. All antler and bone samples were treated with cold dilute acid. The term ‘collagen’ is used throughout to mean the acid insoluble organic fraction produced by this treatment. Peat samples were treated with dilute acid and alkali to separate the humin and humic acid fractions, which were dated individually.