bluuebunny/crossref_metadata_2025 huggingface dataset:
Gliwice Radiocarbon Dates VI
Authors: Pazdur Mieczysław F , Pazdur Anna , Zastawny Andrzej
Published: July 2016

Results presented in this date list have been obtained from Jan 1977 to Dec 1977, but some earlier measurements are also included. All calculations are based on a contemporary value equal to 0.95 of the activity of NBS oxalic acid standard and on the Libby value for the half-life of radiocarbon. Ages are reported as conventional radiocarbon dates in years before AD 1950. No corrections for13C/12C ratio were made for measurements reported in this list. Errors quoted (±1σ) included estimated overall standard deviations of count rates of the unknown sample, contemporary standard and background (Pazdur & Walanus, 1979). Counting equipment and experimental procedures have been described earlier (Mościcki & Zastawny, 1976, 1977; Pazduret al, 1978; Pazdur & Pazdur, 1979a). Sample descriptions are based on information provided by the submitters.
Charcoal production from wood and cellulose: implications to radiocarbon dates and accelerator target production
Authors: Leavitt S W , Donahue D J , Long Austin
Published: July 2016

Radiocarbon dating with accelerators requires the manufacture of suitable carbon targets. Carbon yield and13C fractionation were investigated for the simple and direct pyrolysis of wood and cellulose to charcoal. Under continuous vacuum removal of evolved volatiles, carbon yields of 35 to 40% and δ13C fractionation of −2.5‰ were observed in the pyrolysis of wood to charcoal, whereas yields of 30% and fractionation of −0.8‰ were obtained in the pyrolysis of cellulose to charcoal. Yield and fractionation leveled off at temperatures above 300°C. Yields and fractionations were also measured for pyrolysis of wood and cellulose in a continously-flowing argon atmosphere. Yields were higher and fractionations smaller than for the corresponding vacuum cases. For cellulose sealed in evacuated glass tubes and pyrolized at 550 to 600°C, carbon yields greater than 60% and fractionation of about −0.5‰ were observed. Yields increased and fractionation tended to decrease as the ratio of tube volume/mass of cellulose decreased,ie, as the pressure increased. Reheating of this charcoal under continuous vacuum pumping revealed no loss of mass and no alteration of carbon isotopic composition. Fractionation measurements were additionally performed on wood and the charcoal produced from burning in a fireplace, conditions approximating the “natural“ production of charcoal. Despite the large potential fractionation suggested in the wood pyrolysis experiments, charcoal produced in the fireplace showed very small or no fractionation.
Calibration of radiocarbon dates: tables based on the consensus data of the Workshop on Calibrating the Radiocarbon Time Scale
Authors: Klein Jeffrey , Lerman J C , Damon P E , Ralph E K
Published: July 2016

A calibration is presented for conventional radiocarbon ages ranging from 10 to 7240 years BP and thus covering a calendric range of 8000 years from 6050 BC to AD 1950. Distinctive features of this calibration include 1) an improved data set consisting of 1154 radiocarbon measurements on samples of known age, 2) an extended range over which radiocarbon ages may be calibrated (an additional 530 years), 3) separate 95% confidence intervals (in tabular from) for six different radiocarbon uncertainties (20, 50, 100, 150, 200, 300 years), and 4) an estimate of the non-Poisson errors related to radiocarbon determinations, including an estimate of the systematic errors between laboratories.
Rudjer Bošković Institute Radiocarbon Measurements VII
Authors: Srdoč Dušan , Horvatinčic Nada , Obelic Bogomil , Sliepčevic Adela
Published: July 2016

Results of extensive and systematic radiocarbon dating of tufa samples and associated materials (wood, plants, moss, and peat) are presented in this paper. Samples were collected in Plitvice Lakes National Park, Central Croatia, Yugoslavia, where intensive precipitation of tufa has taken place over several geologic epochs in a typical Karst area. Problems associated with radiocarbon dating of tufa are discussed in a previous paper (Srdoč et al, 1980). The authors concluded that dating of tufa is feasible and reliable, at least in the specific case of Karst regions, where retention of groundwater is short. Tufa is precipitated as a result of decomposition of groundwater bicarbonates due to loss of CO2, usually in waterfalls and cascades, and it is practically contemporaneous with living organic material. However, radiocarbon activity of modern tufa is lower than that of organic material due to dissolution of inactive carbonates (limestone) in groundwater. The initial activity of groundwater depends on the geology and vegetation of the area and it is widely discussed in the literature (Geyh, 1973). The initial activity, Ao, of tufa could be easily measured on recent samples, had not bomb-test contamination upset the equilibrium. Namely, while the atmospheric CO2 and living matter responded relatively quickly to the injection of radiocarbon in the atmosphere, groundwater and, consequently, tufa showed a much slower and damped response. Therefore, we have based our estimation of the initial activity of tufa on measurements of samples of known age collected before the bomb-test era. An average value of the initial activity equal to 85% of modern has been obtained which is in accordance with data for groundwater activity in similar areas. Consequently, all radiocarbon ages of tufa samples in this paper are based on the Libby half-life of 14C (5568 years) and the initial radiocarbon activity equal to 85% of modern. The modern standard is 0.95 of the activity of NBS oxalic acid. Errors quoted are based on counting statistics only and do not include uncertainties in 14C half-life and in initial activity. The latter may introduce much larger errors, up to ± 1000 years, depending on the sampling site, as explained in the following sections. Whereas radiocarbon dating of Holocene tufa beds give reliable ages within the above specified errors, radiocarbon dating of old tufa beds is still questionable. Intrusion of minute quantities of modern calcareous material renders the ages of old (∼30,000 yr) tufa useless. Research on measuring the age of old tufa deposits by other methods is in progress.
University of Miami Radiocarbon Dates XXII
Authors: Johnson R A , Treadgold G E , 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 August 1980. Chemical and counting procedures remain the same as indicated in R, v 20, p 274–282.
The Long-Term Radiocarbon Trend of the Absolute German Oak Tree-Ring Chronology, 2800 to 800 BC
Authors: Becker Bernd
Published: July 2016

The Hohenheim Tree-Ring Laboratory has extended the Holocene oak tree-ring chronology back to prehistoric times by analyses of subfossil tree trunks from gravel deposits along the rivers of central Europe. Hundreds of subfossil oaks can be collected each year because of widespread gravel quarrying. Despite this nearly continuous source of samples (at present, 2200 trees are analyzed), even within these deposits some limitations do exist in linking together a Holocene tree-ring sequence.
Radiocarbon Activity Variation in Dated Tree Rings Grown in Mackenzie Delta
Authors: Fan C Y , Tie-Mei Chen , Si-Xun Yun , Kai-Mei Dai
Published: July 2016

Forty-five tree rings (1881–1925) were taken from a white spruce grown near Campbell River in Mackenzie Delta, Canada, for the measurement of 14C activity variation. Because of the narrowness of the rings, 2 and sometimes 3 rings were combined to yield a total of 21 specimens. The 14C content in these specimens was measured with a liquid scintillation-PM tube counter system of the History Department of Peking University. The data points exhibit a 10‰ variation, anti-correlated with sunspot numbers. The physical implication is discussed.
14C Variations During the Upper Pleistocene
Authors: Vogel J C
Published: July 2016

Parallel determinations of 14C and ionium dates on a stalagmite from the Cango Caves provide evidence of variations in the 14C content of the atmosphere beyond the range of the California tree-ring sequence. During the Holocene growth period the 230Th dates are compatible with the tree-ring calibrated 14C dates. At 18,000 BP and between 30,000 and 40,000 BP the 14C ages are markedly younger than the 230Th ages, suggesting that the 14C level of the atmosphere was considerably higher at these times. Between the 230Th ages of 35,000 and 29,000 BP the 14C ages remain nearly constant at 29,500 BP, indicating that 14C production must have been drastically reduced during this period. The 14C fluctuation is greater than that predicted by Barbetti (1980) but it may be explained by postulating a substantial increase in the geomagnetic dipole field, for which there is mounting evidence.
Statistics of the AD Record of Climatic and Carbon Isotopic Change
Authors: Stuiver Minze
Published: July 2016

The AD time series of Δ14C, δ13C, and cosmic ray fluxes, Q, were analyzed for similarities. Two cases of significant correlation between Q and tree-ring δ13C were encountered, for which up to 25% of the variance can be attributed to changes in the tree's isotope fractionation that related to solar induced climatic changes. However, it is possible that the demonstrated correlation is fortuitous because actual climate proxy records generally do not correlate significantly with the Q record.
14C Dating and Magnetostratigraphy
Authors: Thompson Roy
Published: July 2016

The history of the earth's magnetic field is preserved in the fossil magnetism of archaeologic specimens, natural rocks and sediments. Samples such as lava flows and baked sherds that acquired a thermoremanent magnetization on cooling can be used to estimate ancient geomagnetic field intensities and directions. Paleofield directions can also be obtained from fine-grained sediments that acquired detrital magnetic remanence when deposited. Study of the earth's magnetic field over the last few tens of thousands of years yields information on geomagnetic dynamo theories, causes of fluctuations in cosmic-ray activity, and the formulation of a new regional chronologic tool.
Modeling of Atmospheric Radiocarbon Fluctuations for the Past Three Centuries
Authors: Damon P E , Sternberg R S , Radnell C J
Published: July 2016

Relatively precise quantitative observations of geophysical parameters are available to evaluate the fluctuations of atmospheric14C activity during the past three centuries. As reviewed by Damon, Lerman, and Long (1978), these fluctuations seem to result from three factors: 1) changes in the earth's dipole magnetic field intensity, which has been decreasing since the first measurements by Gauss (McDonald and Gunst, 1968); 2) solar modulation of the cosmic-ray production, which has been correlated with the sunspot record of Waldmeier (1961), and more recently, to the Aa geomagnetic index by Stuiver and Quay (1980); and 3) the combustion of fossil fuels (Suess, 1955). A relationship between the climatic time series and the14C-derived record of solar change has not yet been demonstrated (Stuiver, 1980).
13CO2 and 14CO2 Measurements on Soil Atmosphere Sampled in the Sub-Surface Unsaturated Zone in the Western Great Plains of the US
Authors: Haas Herbert , Fisher D W , Thorstenson D C , Weeks E P
Published: July 2016

Soil gas samples were obtained from the unsaturated zone at eight sites in the Great Plains. Three of these sites were sampled extensively for gas composition and carbon isotopes. Sampling equipment consisted of a nest of gas probes vertically spaced by roughly 3m at most sites, generally approaching the water table. Water wells, 10cm in diameter, were screened in the topmost layer groundwater. Inverted cattle tanks were used to collect CO2 samples from the soil surface. The major gas components were analyzed with emphasis on CO2, δ 13C, and 14C measurements. The same components were studied in groundwater samples. Higher than atmospheric CO2 concentrations were found in all soil samples. Root respiration and oxidation of organic matter were sources for the additional CO2. When lignite was present in the unsaturated zone, gaseous oxygen reacted almost completely, and CO2 levels rose to 19%. Near the surface, annual cycles in total CO2, δ 13C, and 14C were observed. 14C activities were close to present post-bomb levels at the surface and generally declined with depth. At some sites, oxidation of lignite caused decline of 14C levels to 1 or 2% of their surface value at 8m depth. Without lignite, the 14C activity remained above 50% at all depths. Concentrations of total carbon and its isotopes in ground water remained very stable throughout the study. This implies that geochemical processes in the aquifer vary on time scales longer than the seasonal effects observed in the near-surface unsaturated zone.
Ground-Water Circulation in the Meade Thrust Allochthon Evaluated by Radiocarbon Techniques
Authors: Muller A B , Mayo A L
Published: July 2016

The Meade thrust, in southeastern Idaho, is a major element of the Western Overthrust Belt. The allochthon is of geo-economic importance both as a potential hydrothermal area and as the principal mining area within the Western Phosphate Field. To assist in the development of these two resources, an understanding of the regional ground-water circulation was sought. Geologic and hydrologic data from boreholes in this area are virtually nonexistent. Waterwell development in the area has not occurred because of the abundance of springs and only a few hydrocarbon exploration boreholes have been drilled. Thus, the problem lends itself to evaluation by isotope hydrologic and geochemical methods. Ten springs from within the thrust block and around its periphery were sampled for major ions, 2H/18O, and 14C/13C analysis. Data from these analyses and from field geologic evidence have identified two distinct flow regimes within the Meade thrust allochthon. Shallow flow systems lie above the impermeable Phosphoria Formation, usually within a few hundred meters of the surface. Most of the spring waters from this system are recent and cool. In all cases, they have mean subsurface residence times of less than a few hundred years. The deeper flow systems which lie below the Phosphoria formation are hydraulically isolated from the shallow system. Warm waters from these springs have 14C contents suggesting mean ground-water residence times on the order of 15,000 years. Although these waters could have circulated to as deep as 1900m, 2H/18O results show that high temperatures were never reached. There is no evidence to suggest that water from beneath the Meade thrust has contributed to the circulation in the allochthon.
Studies on Holocene Geochronology of the Coastal Region of Southern Fujian, China
Authors: Chenghui Chen , Baolin Huang , Mingliang Wang
Published: July 2016

Our studies on 14C chronology and palynology of Holocene sediments in southern Fujian along the western coast of the Taiwan Straits show that the natural environment has undergone three stages of development during the Holocene. From Early Holocene (ca 10,000–8000 yr ago) to Middle Holocene (8000–2500 yr ago) and then to Late Holocene (2500 yr ago), sediments varied from land-sea transitional to marine and then to terrigenous; vegetation altered from mixed forest to evergreen broad-leaf forest and then steppe; climate fluctuated from temperate to hot and then to warm. The sea-level maximum in the post-glacial period occurred at 5000–6000 yr ago, at 5 to 10m elevation. During the subsequent regression, two stable stages of sea-level dated at >3000 and ca 2000 yr ago. The climatic drying and eolian sand deposit began at 700 yr ago. The results agree with our previous studies in southern Liaoning.
Carbon Exchange Between Atmosphere and Oceans in a Latitude-Dependent Advection-Diffusion Model
Authors: Kratz Gerhard , Kohlmaier G H , Siré E O , Fischbach Ursula , Bröhl Horst
Published: July 2016

Marine transport of inorganic and organic carbon is simulated by means of a computer model in which the oceans are divided into a high and low latitude region. Water transport (and with it carbon transport) is reproduced 1) as downwelling of surface waters at low latitudes, and 2) in general, as different depth-dependent turbulent diffusion in both deep-sea regions. The model is calibrated with pre-bomb 14C and validated against perturbations of total carbon, 13C/C- and 14C/C-ratios; it is compatible with carbon release from fossil fuels and from biogenic sources.
International Comparison of Proportional Gas Counters for 14C Activity Measurements
Authors: Mook Willem G
Published: July 2016

In early 1982 we attempted to compile information on 14C counting equipment from all laboratories listed in RADIOCARBON. A gratifying number of laboratories cooperated in communicating their data: more than 65% of those in which proportional counters are in operation. Our compilation covers more than 80% of all gas counters used for 14C dating. Unfortunately, the number of parameters determining counter quality as well as the spread in these factors is so large that their separate influence cannot be established beyond statistical doubt. Nevertheless qualitative and semi-quantitative trends are clearly observed. Laboratories are not identified in the data but the calculations and standardization procedures allow the laboratories to identify their own counter data in the graphs. Each plot does not contain a complete compilation of all counters. This is either because of lack of or internally inconsistent information.
Miniature Signals and Miniature Counters: Accuracy Assurance Via Microprocessors and Multiparameter Control Techniques
Authors: Currie L A , Gerlach R W , Klouda G A , Ruegg F C , Tompkins G B
Published: July 2016

When14C signals approach background levels, the validity of assumptions concerning Poisson counting statistics and measurement system stability becomes crucial in interpreting the resultant low-level counting observations. This has been demonstrated in our previous work on detection limits for non-Poisson error and it is critical in our current studies of carbonaceous pollutants, where the14C signal from just 5 mg C is comparable to that of the background for our miniature gas proportional counters. To assure data quality, our multi-detector system is designed for the on-line monitoring of critical parameters that reflect both the (statistical) nature of the non-Poisson errors and the underlying (physical) causes. It sends >60 bits of information/pulse to a microprocessor which automatically generates, for each counting period, two-dimensional spectra and multiparameter correlation and control charts. To evaluate the validity of long-term counting of 1–10 mg C we use robust (statistical) estimators, optimal counting interval subdivision, and time series analysis of the individual pulses. New opportunities for selective sampling and chemical fractionation which come with the small sample measurement capability have led us to give special attention also to higher control levels, involving e g, isotonic heterogeneity and representative standard materials.
Development and Operation of the Harwell Small Counter Facility for the Measurement of 14C in Very Small Samples
Authors: Otlet R L , Huxtable George , Evans G V , Humphreys D G , Short T D , Conchie S J
Published: July 2016

The Harwell system for measuring milligram size samples using Brookhaven miniature gas counters is fully operative. It comprises 12 counters of different sizes which operate simultaneously within a single NaI crystal (300mm diameter × 300mm long) acting as an anti-coincidence guard counter. Brief details are given of the construction and commissioning of the system, including counter assembly, shield design, electronics, data capture, data analysis, and chemical processing and filling procedures. The performance of the system and an overall view of the fields of application for which the counters have important applications are discussed.
Anthropogenic Changes in Organic Carbon and Trace Metal Input to Lake Washington
Authors: Schell W R , Swanson J R , Currie L A
Published: July 2016

An example of how man's contaminants are introduced, deposited, and retained in sediments giving a chronological record of events has been developed for Lake Washington, Seattle. Significant amounts of both inorganic and organic compounds in the environment originate from fossil fuel sources, such as power plants and motor vehicles. Many organic compounds are introduced also from contemporary biogenic materials. Through the combined carbon isotope analysis technique (CCIA), we can distinguish between fossil and contemporary carbon sources classes (using14C), as well as sources within each class (using13C). To establish the chronology of the organic carbon pollutant input to the lake sediment, the ages of the layers were determined using210pb dating techniques. Sediment profiles of trace metals and a fallout radionuclide plutonium were also obtained and compared with the carbon isotope profiles. The results show that the total organic carbon (TOC) concentration correspond to 93% modern carbon before 1905. This14C concentration in TOC decreased to ∼60% modern in the 1930's and now is between 95 and 80% modern. The lipid fraction is ca 30% modern and the total aromatic hydrocarbon fraction reached a minimum of 5% modern in 1954. The large decrease in14C of TOC around 1930 is believed to be due to coal dust or fly ash. The trace metal concentration also increased substantially at this time. The pattern observed in the sediment thus reflects the change in the local energy consumption pattern from a predominately coal to an oil-based economy. From the plutonium profile we infer that mixing occurs for 3 or 4 years before the sediment layers are compacted.
Results of Tests and Measurements from the Nsf Regional Accelerator Facility for Radioisotope Dating
Authors: Donahue D J , Zabel T H , Jull A J T , Damon P E , Purser K H
Published: July 2016

Tests of performance of the tandem accelerator mass spectrometer at the NSF Regional Facility at the University of Arizona are discussed. Results of measurements on some tree rings and on some archaeologic samples are presented.
Sample Chemistry for the Oxford High Energy Mass Spectrometer
Authors: Gillespie Richard , Hedges Robert E M
Published: July 2016

Chemical pretreatment procedures for the decontamination, extraction, and isolation of organic materials for 14C dating using the Oxford accelerator system are described. Specific details are given for the isolation and chromatographic purification of amino acids from bone and tooth collagen, of lipids from sediments, and of cellulose and glucose from wood, paper, and textiles. A description is also given of the apparatus used for the routine preparation of 1 to 5mg graphite samples on tantalum wire, for use in the accelerator ion source.

The high energy mass spectrometer (HEMS) approach to 14C dating allows the use of very small samples in the low milligram range. Sample pretreatment and decontamination procedures can be both more vigorous and more selective than those used by conventional dating laboratories. Specific chemical compounds can be isolated from archaeologic or geologic samples; such compounds may be characteristic of particular source materials and, hence, provide more detailed information than is generally possible using bulk organic samples. The Oxford Radiocarbon Unit has concentrated on three sample types that represent the kind of material we expect to work on initially: bone, lake sediment, and wood.
Gliwice Radiocarbon Dates IX
Authors: Pazdur Mieczysław F , Awsiuk Romuald , Bluszcz Andrzej , Pazdur Anna , Walanus Adam , Zastawny Andrzej
Published: July 2016

The following list contains most of the measurements of geologic samples made during 1979 and 1980 using carbon-dioxide-filled proportional counters. Samples with laboratory numbers > 1000 were counted with counter No. 1 (L1), and those with numbers < 1000, with counter No. 3 (L3), described by Mościcki and Zastawny (1977). Actual parameters of both counters were given in our previous date list (R, 1982, v 24, p 172).
University of Lund Radiocarbon Dates XVI
Authors: Håkansson Sören
Published: July 2016

Most of the 14C measurements reported here were made between October 1981 and October 1982. Equipment, measurement, and treatment of samples are as reported previously (R, 1968, v 10, p 36–37; 1976, v 18, p 290; 1980, v 22, p 1045).
Simon Fraser University Radiocarbon Dates II
Authors: Hobson K A , Nelson D E
Published: July 2016

This list reports measurements made on archaeologic samples by our laboratory from September 1980 to May 1982. Results of measurements made during that period which lack review by submitters will be reported in a subsequent date list. Dates were obtained by liquid scintillation counting of benzene using the laboratory procedure outlined previously (R, 1982, v 24, p 344–351). All dates are expressed in 14C years relative to ad 1950 based on the Libby half-life for 14C of 5568 yr. The laboratory standard continues to be ANU sucrose. Data analysis is now performed with the aid of an RT-11 microcomputer interfaced with our Packard model 3255 LS counter. Dates have been corrected for isotopic fractionation only when the δ13C value is given. No corrections have been made for natural 14C variations. The following descriptions of samples are based on information provided by the submitters.
Tallinn Radiocarbon Dates VII
Authors: Punning J M , Rajamäe R , Joers Kai , Putnik H
Published: July 2016

This list comprises age measurements carried out at the Institute from 1979 to 1981. Anticoincidence variant was applied to attain higher counting efficiency of a 2-channel scintillation device. The introduction of a plastic scintillator as an active guard around the detector in the 2π geometry decreases the influence of high energy cosmic radiation and reduces the background ca 35 to 75% (Rajamäe & Punning, 1980). The application of an active guard with 4π geometry has proved most effective; as a result, the background decreased 85% to 0.65cpm with the volume of scintillation cocktail 5ml. We have improved our methods for decreasing the actual error of the background. The application of a control channel and consideration of barometric effect results in the increase of dating limits of up to 5000–6000 years (Rajamäe, 1981). Samples are calculated using a half-life of 5568 ± 30 years for 14C. Results are reported in years before 1950. δ13C measurements were performed on the mass-spectrometer MI-1201 and are reported with PDB as a reference standard. The reproducibility of results is ±0.2‰.
Vienna Radium Institute Radiocarbon Dates XIII
Authors: Felber Heinz
Published: July 2016

Measurements have continued with the same proportional counter system, pretreatment procedure, methane preparation and measurement, and calculation, as described previously (R, 1970, v 12, p 298–318). Uncertainties quoted are single standard deviations originating from standard, sample, and background counting rates. No13C/12C ratios were measured. Sample descriptions have been prepared in cooperation with submitters.
Zero BP Plus 34: 25 Years of Radiocarbon
Authors: Deevey Edward S
Published: July 2016

Very incautiously, after printing 25 volumes of Radiocarbon, the editors have authorized some personal reminiscence. Like all “Quaternary scientists”—no better collective name is available for our strange profession—I have been engaged in historiography, writing about history, for many years. In 1946, when natural radiocarbon was discovered, my subject, the sedimentary history of lakes, was only one of several kinds of historical record that needed, and soon received, a new reading. At the time, not all custodians of other kinds of record were ready to agree that new readings were conceivable, let alone necessary. The record of their persuasion—some of which has been written by Greg Marlowe (1980) in “W F Libby and the Archaeologists”—is part of the history of historiography. To the bibliography of this dangerously abstract subject I venture to add some minor footnotes. They come, not from historical research like Marlowe's, but from a leaky, selective memory.
British Museum Natural Radiocarbon Measurements XVII
Authors: Burleigh Richard , Ambers Janet , Matthews Keith
Published: July 2016

The following list consists of dates for archaeologic and geologic samples mostly measured from June 1982 to June 1983. The dates were obtained by liquid scintillation counting of benzene using the laboratory procedures outlined in previous lists (see, eg, BM-VIII, R, 1976, v 18, p 16). Dates are expressed in radiocarbon years relative to ad 1950 based on the Libby half-life for 14C of 5570 yr, and are corrected for isotopic fractionation (δ13C values are relative to PDB). No corrections have been made for natural 14C variations. The modern reference standard is NBS oxalic acid (SRM 4990). Errors quoted with dates are based on counting statistics alone and are equivalent to ± 1 standard deviation (± 1σ). Descriptions, comments, and references to publications are based on information supplied by submitters.
US Geological Survey, Denver, Colorado Radiocarbon Dates IV
Authors: Yang I C
Published: July 2016

This list contains the results of measurements of 167 groundwater samples made between September 1979 and December 1982. An additional 175 samples were measured, but these were submitted without detailed information, such as sampling depth, well location, etc; therefore, they were excluded from the following list.
University of Pennsylvania Radiocarbon Dates XXII
Authors: Hurst Barbara J , Lawn Barbara
Published: July 2016

This date list includes most of the archaeologic and geologic samples dated in this laboratory since publication of our last date list (R, 1981, v 23, p 227–240), as well as some samples dated previously which lacked adequate sample information.

All samples were pretreated with 3N HCl and some, where noted, were given additional pretreatment with 2% NaOH for the removal of possible humic acid contaminants.
Udine Radiocarbon Laboratory Date List II
Authors: Barbina Valerio , Calligaris Franco , Del Fabbro Adriano , Turello Alessandro
Published: July 2016

This list includes the measurements carried out from 1977–1978. Procedures of synthesis of benzene, counting method, and performance figures of results were previously described (R, 1982, v 24, p 214–216; CRAD, 1977; Barbina, Calligaris, & Ciuti, 1979). Samples were pretreated according to generally applied methods, depending on type of material and particular archaeologic and geologic features.
Vienna Radium Institute Radiocarbon Dates XIV
Authors: Felber Heinz
Published: July 2016

Measurements have continued with the same proportional counter system, pretreatment procedure, methane preparation and measurement, and calculation, as described previously (R, 1970, v 12, p 298–318). Uncertainties quoted are single standard deviations. No 13C/12C ratios were measured. Sample descriptions have been prepared in cooperation with submitters.
Rudjer Bošković Institute Radiocarbon Measurements VIII
Authors: Srdoč Dušan , Obelic Bogomil , Horvatinčic Nada , Krajcar Ines , Sliepčevic Adela
Published: July 2016

The following radiocarbon date list contains dates of samples measured since our previous list (R, 1982, v 24, p 352–371). As before, age calculations are based on the Libby half-life (5570 ± 30) yr and reported in years before 1950. The modern standard is 0.95 of the NBS oxalic acid activity. Sample pretreatment, combustion, and counting technique are essentially the same as described in R, 1971, v 13, p 135–140, supplemented by new techniques for groundwater processing (R, 1979, v 21, p 131–137).
Contamination Studies on Mollusk Shell Samples
Authors: Goslar Tomasz , Pazdur Mieczysław F
Published: July 2016

A series of shell samples has been studied to determine the magnitude and mechanisms of carbon exchange between shells and their environment. Laboratory contamination experiments included the storing of shell samples in acid and calcareous environments of different 14C concentrations as well as studies of carbon exchange in the course of thermal recrystallization in solid state in an atomosphere of carbon dioxide. The applicability of differential thermal analysis to studies of the structure and texture of shells is discussed.
Woods Hole Oceanographic Institution Radiocarbon Laboratory: Sample Treatment and Gas Preparation
Authors: Griffin Sheila , Druffel Ellen R M
Published: July 2016

The purpose of this paper is to present the methodology used for sample preparation at the Woods Hole Oceanographic Institution Radiocarbon Laboratory. The WHOI lab is dedicated to oceanographic research supported by the National Science Foundation (OCE81-11954). We began operation in March 1982. The methods used for the production of samples are based on those developed previously (Barker, 1953; Suess, 1954; Noakes, Kim, & Stipp, 1969; Linick, 1975). Subsequent changes and refinements to these methods are described. This paper will present detailed descriptions of how various samples are collected and sectioned, then converted to CO2 and to C2H2, the primary counting gas for most of our samples.
Harwell Radiocarbon Measurements IV
Authors: Walker A J , Otlet R L
Published: July 2016

The dates in this list follow, in approximately chronologic order, those reported in Harwell III (R, 1979, v 21, p 358–383). It is confined to archaeologic samples from the United Kingdom only, most of which originate from “rescue” type operations supported by the Historic Buildings and Monuments Commission for England, (formerly a section of the Dept. of the Environment) and submitted through the Ancient Monuments Laboratory, London.
The Effect of Atmospheric 14C Variations on the 14C Levels in the Jordan River System
Authors: Carmi Israel , Stiller Mariana , Kaufman Aaron
Published: July 2016

13C and 14C were measured in the upper Jordan River, in its tributaries which issue from the Mount Hermon aquifer, and in the local atmospheric CO2 to evaluate the degree to which changes in the atmospheric 14C levels influence the 14C levels in the aquifer and in the Jordan River. The exchange fraction of CO2 between the river and the atmosphere was calculated for fall 1983 with the two carbon isotopes and it is shown that the value obtained with 14C (0.364) is the more reliable. The ratio of 14C in the Jordan River to that in the atmosphere in 1972 is similar to that in 1983, 0.66 and 0.67, respectively. This implies an approximately constant ratio (0.44) between the 14C level in the Mount Hermon aquifer base-flow and the 14C level in the atmospheric CO2. This information can be combined with the known historical fluctuations in the 14C levels of the atmosphere to calculate the 14C fluctuations in the discharge of the Jordan River into Lake Kinneret, backwards in time.
Secular Variations of Cosmogenic 14C on Earth: Their Discovery and Interpretation
Authors: Suess Hans E
Published: July 2016

Measurement of 14C in samples of wood of precisely known age have shown that the cosmogenic 14C content of the CO2 in the atmosphere has not remained constant during the period of time covered by radiocarbon dating. As the terrestrial atmosphere mixes with a time constant of less than 3 years, these variations must be essentially independent of geographic location. The 14C in atmospheric CO2 must be a quantity that, at a given time, pertains to the terrestrial atmosphere as a whole. Not only is its knowledge necessary for deriving accurate radiocarbon dates, but it is also valuable in connection with many geophysical and astrophysical problems. Unfortunately, progress in our knowledge of 14C variations in the terrestrial atmosphere has been delayed by hidden experimental errors in results obtained by many laboratories. By rigorous statistical analysis of the La Jolla results, it is now possible to show that the 14C variations are not simple random fluctuations but show distinct regularities. Similar patterns of variations have been found in the growth rate of trees during the last 5000 years. Measurements of radiogenic 10Be currently being done by European workers promise to conclusively elucidate the 14C findings.
Ice-Core Dating of the Pleistocene/Holocene Boundary Applied to a Calibration of the14C Time Scale
Authors: Hammer Claus U , Clausen Henrik B , Tauber Henrik
Published: July 2016

Seasonal variations in18O content, in acidity, and in dust content have been used to count annual layers in the Dye 3 deep ice core back to the Late Glacial. In this way the Pleistocene/Holocene boundary has been absolutely dated to 8770 BC with an estimated error limit of ± 150 years. If compared to the conventional14C age of the same boundary a value of Δ14C = 53 ± 13‰ is obtained. This Δ14C value suggests that14C levels during the Late Glacial were not substantially higher than during the Postglacial.
Radiocarbon Dating of Sediments
Authors: Fowler Alison J , Gillespie Richard , Hedges Robert E M
Published: July 2016

In14C dating of sediment, the date of deposition is associated with its C age. Most sediments are complex mixtures containing little organic material frequently derived from several sources. The most conspicuous sources of error result from 1) the incorporation of “fossil” carbon (eg, graphite, lignite, etc) into a more recent sediment. This is particularly important in low carbon sediments (Olsson, 1972); 2) the incorporation of older, ‘reworked’ sedimentary material, eg, from terrigenous sources into a lacustrine environment (Schoute, Mook & Streuerman, 1983); 3) the dating of mainly autochthonous material which has metabolized carbon from dissolved bicarbonate carbonates originating from dissolution of fossil.

To provide more information for the14C ages of components of a sediment, we have used the small sample capability (ie, > = 1 mg carbon) of the Oxford Radiocarbon Accelerator to date specific fractions. Within the limitations of the ‘conventional’ method, different fractions insoilshave been the subject of two investigations (Scharpenseel, 1979; Sheppard, Syed & Mehringer, 1979). In general the results show that a measurement on undifferentiated sediment may lead to serious errors in the14C date, that specific fractions do not guarantee a better date for deposition, but nearly always provide valuable information on the particular history of the individual sediment in relation to its specific context. It is usually possible to estimate the occurrence of the first two sources of error listed above, but more difficult to quantify the extent of terrestrial input and “hard water” error.
Studies of Non-Marine Mollusks for the Selection of Shell Samples for Radiocarbon Dating
Authors: Yates Timothy
Published: July 2016

14C dating of shells from terrestrial and freshwater mollusks is prone to distortion by post-depositional diagenesis as well as incorporation of material depleted in14C while the mollusk was alive. Three types of diagenetic change can result: etching, the development of surface crusts, and replacement of aragonite by calcite. Inspection under the light microscope, x-ray diffraction, and scanning electron microscope make it possible to assess the relative importance of the changes. When they are confined to the surface, mechanical cleaning combined with judicious leaching can reduce them to <1% of the total sample. The corresponding errors, which can now be specified, are often no greater than those associated with the statistics of counting.
Increase of 14C Activity of Dissolved Inorganic Carbon Along a River Course
Authors: Srdoč Dušan , Krajcar-Bronić Ines , Horvatinčić Nada , Obelić Bogomil
Published: July 2016

Results of measurements for 3 years (1981–1983) of 14C activity of dissolved inorganic carbon (DIG) in water samples from the Korana River, as well as that of recent tufa and aquatic plants, showed that 14C concentration increases from karst spring to the estuary. A model describing the increase of 14C activity was developed assuming that the increase is due to the exchange of the dissolved CO2 in stream water with atmospheric CO2 and to dissolution of CO2 from the decay of organic material and root respiration. It is possible to distinguish these two contributions by measuring the δ13C values of DIC in water. As expected, our data show that the exchange process between atmospheric CO2 and DIC dominates at rapids and waterfalls, while biologic contribution is much higher in lakes and along the lowland flow of the Korana River. Agreement between the calculated and the measured activities supports the proposed mechanisms of chemical and isotopic exchanges in stream waters.
Detection of Bias in the Background of Vials Used for Radiocarbon Dating
Authors: Ambers Janet , Leese Morven , Bowman Sheridan
Published: July 2016

Inter-vial variation in background of the glass vials used in liquid scintillation counting can introduce appreciable errors into 14C measurements. Our aim was to measure the background in each of 50 glass vials, under the same conditions as far as possible, in order to find a self-consistent set for use in 14C dating. The criteria, statistical tests, and possible errors introduced by not making such checks are discussed.
The Development of Practical Systems for 14C Measurement in Small Samples Using Miniature Counters
Authors: Otlet R L , Huxtable George , Sanderson D C W
Published: July 2016

Miniature gas counters have been in use since the early 1960s for the measurement of 14C but were for a long time seen as suitable for providing approximate indications of activity rather than measurements for more precise dates. In recent years the need for better measurements of small samples has posed a continuing challenge for the 14C laboratories. This paper examines how the challenge has been met across the world using conventional beta decay counting techniques and proportional gas counters of 50ml volume or less. A survey is made of the rise of these techniques and attention paid to the solution through modern technology of earlier problems. Some practical systems, now in routine use, are described and consideration is given to the future for miniature counter measurements. Such systems have several attractive features that will guarantee their usefulness in 14C measurements for the future.
The AMS Dating of Separate Fractions in Archaeology
Authors: Batten R J , Gillespie Richard , Gowlett J A J , Hedges Rem
Published: July 2016

The usefulness of radiocarbon dates in archaeology greatly depends on both the stratigraphic relationship of the sample submitted and on the origin and homogeneity of the measured carbon. For very small samples, stratigraphic relationships can raise additional problems of movement. In chemically well-characterized materials, the best example being collagen, the carbon source can be reasonably well purified. Many samples, however, survive as a complex mixture of high molecular weight polyphenolic materials, with properties between charcoals, humic acids, and lignins. Charred bone, eg, which rarely contains useful quantities of amino acids, and charred seeds, as well as ‘charcoal,’ frequently come into this category. For such samples, the likelihood of contamination by percolating soil humics is high. It is often possible to extract chemically different fractions and to compare the dates obtained. A less exact comparison can also be made for different samples from the same context. The results suggest that ‘humic’ acid dates can be reliable in a surprisingly frequent number of situations, and that where direct comparison is possible, the reliability can be individually assessed.
Origins of Carbon in Potsherds
Authors: Gabasio Martine , Evin Jacques , Arnal Gaston Bernard , Andrieux Philippe
Published: July 2016

The general reliability of 14C dating in archaeology induced us to try to extend the method to other datable materials that may be uncovered, even those which have till now been neglected or considered unreliable. Improvements in AMS techniques will also help us date very small samples or those with low carbon content. For these reasons we have undertaken a systematic study of the application of 14C dating to potsherds which are usually abundant in prehistoric sites and often more representative of human activity than other materials such as charcoal (Evin, 1983).
Establishment of a Working Data Base for the International Exchange of 14C Data Using Universal Transfer Formats
Authors: Wilcock J D , Otlet R L , Walker A J , Charlesworth S A , Drodge J
Published: July 2016

A high-level record structure for the international communication of 14C data bases is proposed. The record structure is based on the high-level communication format first proposed by the authors at the 23rd International Symposium on Archaeometry, Naples, 1983 and does not require the abandonment of existing systems. A description is given of an implementation of the high-level system at Harwell, with examples of retrieval in an international format (the Radiocarbon date list format) and a keyword-organized local format.
Carbon-Isotope Fractionation During Dry Combustion of Oxalic Acid
Authors: Lowdon J. A.
Published: July 2016

Grey et al. (1969) have discussed the problems that arise when using the wet oxidation method for the preparation of CO2 from oxalic acid and suggest that, although offering an effective substitute, the dry combustion method also has problems.
Groningen Radiocarbon Dates IX
Authors: Vogel J. C.
Published: July 2016

This list contains mainly radiocarbon dates for Africa. Some results for samples from the ocean floor and from islands in the Atlantic and Indian oceans, as well as a few series of geophysical samples have also been included. The results are grouped into three categories: geologic, archaeologic, and geophysical, and arranged according to the country of provenance, passing roughly from N to S. Descriptions and comments are based on information supplied by the collectors and submitters and on the publications cited. In several cases insufficient information was available, but since it is improbable that it will be forthcoming, the dates have been included.
Geological Survey of Canada Radiocarbon Dates X
Authors: Lowdon J. A. , Wilmeth R. , Blake W.
Published: July 2016

The laboratory routinely operates two proportional counters; one 2-L (Dyck and Fyles, 1962) and one 5-L (Dyck et al., 1965). CO2 is used as the counting gas. The 2-L counter is operated mainly at 2 atm. and the 5-L counter mainly at 1 atm. On occasion the 2-L counter is operated at 1 atm. and the 5-L counter at 4 atm. No changes have been made in the CO2 preparation and purification techniques described in previous GSC dating lists (Lowdon et al., 1969; Lowdon and Blake, 1970).
University of Kiel Radiocarbon Measurements V
Authors: Willkomm H. , Erlenkeuser H.
Published: July 2016

Measurements reported in this paper were obtained with the 4.5 L and 3 L CO2 counters, details of which were given earlier (Radiocarbon, v. 11, p. 423). The automatic data recording system built in 1968 (Hänsel, 1968) is now operating for both counting apparatus. For each one the counts of the guard counters ring (A counts), the total counts of the C14 counter (B counts), the coincidences of central and guard ring counter (AB counts), and the anticoincidences (ĀB counts) are tape punched every 100th minute. By an ALGOL program, all counts are checked first for large disturbances. Secondly, equation B = AB + ĀB must hold (as an integral check for proper operation of logical circuitry and the data recording system) and finally statistical compatibility is examined before age and other data for the actual counting apparatus are computed. This detailed check of counting rates by computer has proved to be very efficient to yield reliable long-term measurements.
Birmingham University Radiocarbon Dates V
Authors: Shotton F. W. , Williams R. E. G.
Published: July 2016

The following list comprises results obtained during 1970 from both the 1 L and 6 L counters. Results are not corrected for C13fractionation. Errors quoted refer only to the standard deviation calculated from a statistical analysis of sample and background count rates and the Libby half-life of 5570 ± 30 yr. Pretreatment has been continued as described previously (R., 1969, v. 11, p. 263). In cases where sample size was insufficient for full pretreatment, details of the necessary deviations accompany the result.