bluuebunny/crossref_metadata_2025 huggingface dataset:
AMS 14C Measurements of Dissolved Inorganic Carbon in Pore Waters from a Deep-Sea “Cold Seep” Giant Clam Community Off Hatsushima Island, Sagami Bay, Japan
Authors: Masuzawa Toshiyuki , Kitagawa Hiroyuki , Nakatsuka Takeshi , Handa Nobuhiko , Nakamura Toshio
Published: July 2016

We collected pore waters using an in situ pore water-squeezer for a submersible Shinkai 2000 at six depths beneath the sediment surface within a deep-sea “cold seep” giant clam community off Hatsushima Island, Sagami Bay, Japan. A box core sample was also collected ca. 4.5 km east of the community and pore waters were separated. Dissolved inorganic carbon (DIC) was extracted and purified in a vacuum line and 14C concentration was determined with a Tandetron accelerator mass spectrometer at Nagoya University after conversion to graphite targets using a batch Fe-catalytic hydrogen reduction method. ∆14C values decreased with increasing depth to −938‰ at the sulfate concentration minimum. This indicates that methane used for the active reduction of sulfate and formation of hydrogen sulfide, which is used by symbiotic chemoautotrophic bacteria in gills of the giant clams, is almost dead and is likely supplied from the deep. ∆14C values of DIC vary linearly with δ13C values along a mixing line between that in the bottom water and that produced by the oxidation of dead methane. The δ13C value of DIC oxidized from dead methane is estimated to be ca. −45‰.
14C Level At Mt Chiak and Mt Kyeryong in Korea
Authors: Park J H , Kim J C , Cheoun M K , Kim I C , Youn M , Liu Y H , Kim E S
Published: July 2016

We have observed A14C concentrations in the northern hemisphere temperate region in the bomb pulse period, using cross-dated tree ring samples. The tree-ring samples were taken from one 70-year-old and two 50-year-old red pines (Pinus densiflora) on Mt Chiak, Korea and from a 50-year-old red pine (Pinus densiflora) on Mt Kyeryong, Korea. Twenty-two tree-ring samples from four red pines ranging from 1950 to 2000 AD were pretreated to obtain holo-cellulose, combusted to CO2 by an element analyzer (EA) and converted to graphite for δ14C measurement using the accelerator mass spectrometry (AMS) facility at Seoul National University. Our results for δ14C showed good agreement with those measured by other researchers at similar latitudes. The observed steady decrease of δ14C from 1965 to 2000 AD is described by a single exponential function with a lifetime τ = 15.99 ± 0.43 yr. This lifetime is similar to that of the high-latitude region in Europe.
Radiocarbon Dating of Deep-Sea Corals
Authors: Adkins Jess F , Griffin Shelia , Kashgarian Michaele , Cheng Hai , Druffel E R M , Boyle E A , Lawrence Edwards R , Shen Chuan-Chou
Published: July 2016

Deep-sea corals are a promising new archive of paleoclimate. Coupled radiocarbon and U-series dates allow 14C to be used as a tracer of ocean circulation rate in the same manner as it is used in the modern ocean. Diagenetic alteration of coral skeletons on the seafloor requires a thorough cleaning of contaminating phases of carbon. In addition, 10% of the coral must be chemically leached prior to dissolution to remove adsorbed modern CO2. A survey of modern samples from the full δ14C gradient in the deep ocean demonstrates that the coralline CaCO3 records the radiocarbon value of the dissolved inorganic carbon.
Comment on ‘Determination of the Radiocarbon Age of Parchment of the Vinland Map’
Authors: Ludwig K R
Published: July 2016

I wish to point out some statistical errors in the uncertainty calculations for the radiocarbon age of the Vinland Map (Donahue et al. 2002). First, the authors state that the 14C measurements of samples with chemical treatments B, C, D, and E “… result in consistent radiocarbon ages”, and that “… two (of these analyses) are 1.5 sigma, and the others are one sigma or less, from the weighted average.” In fact, the overall scatter of the data show that it is improbable that these data are statistically coherent, largely because analysis J21C lies 2.1 sigma from the weighted mean.
14C Chronology of Late Pleistocene–Holocene Events in the Nizhnee Priamurie (Southeast Russia)
Authors: Bazarova V B , Mokhova L M , Orlova L A , Klimin M A , Gvozdeva I G
Published: July 2016

The Russian Far East is characterized by widespread peat bogs with a sufficiently thick peat accumulation. A series of radiocarbon dates from the studied peat bogs (in Lower Amur) were obtained. Analysis of these dates shows that the total peat formation in this territory began in the Late Pleistocene–Holocene (11830 ± 820, TIG-157; 9975 ± 120, SOAN-4025). The rates of peat accumulation and the humidity index were counted. In addition, the botanical composition and degree of peat decomposition were defined. These data allow to study in more detail climate fluctuation and the 14C chronology of Holocene events in the region studied.
Marine04 Marine Radiocarbon Age Calibration, 0–26 Cal Kyr Bp
Authors: Hughen Konrad A , Baillie Mike G L , Bard Edouard , Warren Beck J , Bertrand Chanda J H , Blackwell Paul G , Buck Caitlin E , Burr George S , Cutler Kirsten B , Damon Paul E , Edwards Richard L , Fairbanks Richard G , Friedrich Michael , Guilderson Thomas P , Kromer Bernd , McCormac Gerry , Manning Sturt , Bronk Ramsey Christopher , Reimer Paula J , Reimer Ron W , Remmele Sabine , Southon John R , Stuiver Minze , Talamo Sahra , Taylor F W , VAN der Plicht Johannes , Weyhenmeyer Constanze E
Published: July 2016

New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally ratified to replace the terrestrial and marine components of IntCal98. The new calibration data sets extend an additional 2000 yr, from 0–26 cal kyr BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision, and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically-dated tree-ring samples, converted with a box diffusion model to marine mixed-layer ages, cover the period from 0–10.5 cal kyr BP. Beyond 10.5 cal kyr BP, high-resolution marine data become available from foraminifera in varved sediments and U/Th-dated corals. The marine records are corrected with site-specific 14C reservoir age information to provide a single global marine mixed-layer calibration from 10.5–26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed here. The tree-ring data sets, sources of uncertainty, and regional offsets are presented in detail in a companion paper by Reimer et al. (this issue).
Shcal04 Southern Hemisphere Calibration, 0–11.0 Cal Kyr BP
Authors: McCormac F G , Hogg A G , Blackwell P G , Buck C E , Higham T F G , Reimer P J
Published: July 2016

Recent measurements on dendrochronologically-dated wood from the Southern Hemisphere have shown that there are differences between the structural form of the radiocarbon calibration curves from each hemisphere. Thus, it is desirable, when possible, to use calibration data obtained from secure dendrochronologically-dated wood from the corresponding hemisphere. In this paper, we outline the recent work and point the reader to the internationally recommended data set that should be used for future calibration of Southern Hemisphere14C dates.
Formal Statistical Models for Estimating Radiocarbon Calibration Curves
Authors: Buck C E , Blackwell P G
Published: July 2016

We report on the development and implementation of a model-based statistical method for the estimation of radiocarbon calibration curves using diverse data. The method takes account of uncertainty on both the 14C and calendar scales, coherently integrating data, the calendar age estimates of which arise from different dating methods. It also allows for correlation between observations, if they have particular sources of uncertainty in common. We adopt an approach based on a random walk model, tailoring it to take account of possible calendar age offsets between different data sources by adding a random effect component. The latter allows us to use the same modeling framework for constructing the new calibration curve IntCal04, the comparison curve NotCal04, the Southern Hemisphere curve SHCal04, and the marine calibration curve Marine04.
Radiocarbon Calibration in the Anglo-Saxon Period: Ad 495–725
Authors: McCormac F G , Bayliss A , Baillie M G L , Brown D M
Published: July 2016

Radiocarbon dating has been rarely used for chronological problems relating to the Anglo-Saxon period. The “flatness” of the calibration curve and the resultant wide range in calendrical dates provide little advantage over traditional archaeological dating in this period. Recent advances in Bayesian methodology have, however, created the possibility of refining and checking the established chronologies, based on typology of artifacts, against 14C dates. The calibration process, within such a confined age range, however, relies heavily on the structural accuracy of the calibration curve. We have therefore re-measured, at decadal intervals, a section of the Irish oak chronology for the period AD 495–725. These measurements have been included in IntCal04.
Radiocarbon Calibration and Comparison to 50 Kyr BP with Paired 14C and 230Th Dating of Corals from Vanuatu and Papua New Guinea
Authors: Cutler K B , Gray S C , Burr G S , Edwards R L , Taylor F W , Cabioch G , Beck J W , Cheng H , Moore J
Published: July 2016

We calibrated portions of the radiocarbon time scale with combined 230Th, 231Pa, 14C measurements of corals collected from Espiritu Santo, Vanuatu and the Huon Peninsula, Papua New Guinea. The new data map 14C variations ranging from the current limit of the tree-ring calibration [11,900 calendar years before present (cal BP), Kromer and Spurk 1998, now updated to 12,400 cal B P, see Kromer et al., this issue], to the 14C-dating limit of 50,000 cal BP, with detailed structure between 14 to 16 cal kyr BP and 19 to 24 cal kyr BP. Samples older than 25,000 cal BP were analyzed with high-precision 231Pa dating methods (Pickett et al. 1994; Edwards et al. 1997) as a rigorous second check on the accuracy of the 230Th ages. These are the first coral calibration data to receive this additional check, adding confidence to the age data forming the older portion of the calibration. Our results, in general, show that the offset between calibrated and 14C ages generally increases with age until about 28,000 cal BP, when the recorded 14C age is nearly 6800 yr too young. The gap between ages before this time is less; at 50,000 cal BP, the recorded 14C age is 4600 yr too young. Two major 14C-age plateaus result from a 130 drop in Δ14C between 14–15 cal kyr BP and a 700 drop in Δ14C between 22–25 cal kyr BP. In addition, a large atmospheric Δ14C excursion to values over 1000 occurs at 28 cal kyr BP. Between 20 and 10 cal kyr BP, a component of atmospheric Δ14C anti-correlates with Greenland ice δ18O, indicating that some portion of the variability in atmospheric Δ14C is related to climate change, most likely through climate-related changes in the carbon cycle. Furthermore, the 28-kyr excursion occurs at about the time of significant climate shifts. Taken as a whole, our data indicate that in addition to a terrestrial magnetic field, factors related to climate change have affected the history of atmospheric 14C.
Radiocarbon Results from a 13-Kyr BP Coral from the Huon Peninsula, Papua New Guinea
Authors: Burr G S , Galang Chrystie , Taylor F W , Gallup Christina , Lawrence Edwards R , Cutler Kirsten , Quirk Bill
Published: July 2016

This paper presents radiocarbon results from a single Goniastrea favulus coral from Papua New Guinea which lived continuously between 13.0 and 13.1 kyr BP. The specimen was collected from a drill core on the Huon Peninsula and has been independently dated with 230Th. A site-specific reservoir correction has been applied to the results, and coral growth bands were used to calibrate individual growth years. Alternating density bands, which are the result of seasonal growth variations, were subsampled to provide 2 integrated 6-month 14C measurements per year. This allows for 20 independent measurements to be averaged for each decadal value of the 14C calibration, making these results the highest resolution data set available for this brief time range. The finestructure of the data set exhibits 14C oscillations with frequencies on the order of 4 to 10 yr, similar to those observed in modern coral 14C records.
Towards a Deeper Understanding of How Carbonate Isotopes (14C, 13C, 18O) Reflect Environmental Changes: A Study with Recent 210Pb-Dated Sediments of the Plitvice Lakes, Croatia
Authors: Horvatinčić Nada , Barešić Jadranka , Babinka Slavica , Obelić Bogomil , Krajcar Bronić Ines , Vreča Polona , Suckow Axel
Published: July 2016

Five short cores (top 40–45 cm of sediment) from 4 lakes of the Plitvice Lakes system (Croatia) were measured for 210Pb, 137Cs, a14C, δ13C, and δ18O in order to study the influence of environmental changes on the sediment system in small and large lakes. Sediment chronology based on the constant flux (CF) 210Pb model was the most reliable. Lake sediments consisted mainly of autochthonous carbonates with higher sedimentation rates in small lakes. Sediments from 2 large lakes, Prošće and Kozjak, showed constant stable isotope profiles for the carbonate fraction and full agreement between the 137Cs and 210Pb chronologies. Sediments from 2 small lakes, Gradinsko and Kaluderovac, showed synchronous increases in 14C and δ13C and disturbed 137Cs records. All lakes showed an increase in a14C in the carbonate sediments above the first occurrence of 137Cs, which was interpreted as a damped (~10 pMC increase in a14C) and decades-delayed consequence of the bomb-induced increase in a14C in atmospheric CO2. For the small lakes, increased δ13C in the last 2 decades and part of the a14C increase is probably due to an increase in primary productivity, which enhanced biologically induced calcite precipitation with concomitant changes in the carbon isotopic composition of carbonate sediments. δ13C values of a near-shore sediment core close to the confluence of one of the tributaries of Lake Kozjak showed that the carbonates in this core are a mixture of autochthonous and eroded allochthonous mineral carbonate. This core had a higher fraction of organic material. The sedimentation rate at this core site was high, but rates could not be quantified by 210Pb, 137Cs, or 14C.
Marine Reservoir Ages in Northern Senegal and Mauritania Coastal Waters
Authors: Ndeye Maurice
Published: July 2016

In order to estimate the modern reservoir age of the seawater (R) and the corresponding local offset from the global marine radiocarbon calibration curve (δR) for coastal sites of Senegal and Mauritania, we analyzed pre-bomb mollusk shells collected between AD 1837 and 1945. In total, 27 shell samples were measured, including 19 from Senegal and 8 from Mauritania. The results for Senegal for the weighted mean of R is 511 ± 50 BP and δR is 176 ± 15 BP; for Mauritania, R is 421 ± 15 BP and δR is 71 ± 13 BP. While these values indicate a significant difference from the global mean value of R for Senegal, the R value for coastal Mauritania is close to the average ocean value R of ~400 yr (Stuiver and Braziunas 1993).
Developments in Radiocarbon Technologies: From the Libby Counter to Compound-Specific AMS Analyses
Authors: Povinec Pavel P , Litherland A E , von Reden Karl F
Published: July 2016

We review developments in radiocarbon measuring techniques from the Libby counter through proportional gas counters and liquid scintillation spectrometers to the more recent developments of accelerator mass spectrometry (AMS), followed by a coupling of gas chromatography with AMS for compound-specific14C analyses. While during the first 60 yr of14C measurements beta counting, specifically gas counting, was the dominant technique, in the future of14C science AMS will be the dominant technology.
Calibration Introduction
Authors: Scott E M , Reimer P J
Published: July 2016

There are 2 fundamental assumptions in radiocarbon dating, which were known early in the method development to be approximations, and which lead directly to the need to calibrate 14C dates:

1.

The rate of formation of 14C in the upper atmosphere has been constant over the entire applied 14C dating timescale (approximately the last 65,000 yr).

2.

The 14C activity of the atmosphere has been in equilibrium with the biosphere and ocean over the applied timescale.
Bayesian Analysis of Radiocarbon Dates
Authors: Bronk Ramsey Christopher
Published: July 2016

If radiocarbon measurements are to be used at all for chronological purposes, we have to use statistical methods for calibration. The most widely used method of calibration can be seen as a simple application of Bayesian statistics, which uses both the information from the new measurement and information from the 14C calibration curve. In most dating applications, however, we have larger numbers of 14C measurements and we wish to relate those to events in the past. Bayesian statistics provides a coherent framework in which such analysis can be performed and is becoming a core element in many 14C dating projects. This article gives an overview of the main model components used in chronological analysis, their mathematical formulation, and examples of how such analyses can be performed using the latest version of the OxCal software (v4). Many such models can be put together, in a modular fashion, from simple elements, with defined constraints and groupings. In other cases, the commonly used “uniform phase” models might not be appropriate, and ramped, exponential, or normal distributions of events might be more useful. When considering analyses of these kinds, it is useful to be able run simulations on synthetic data. Methods for performing such tests are discussed here along with other methods of diagnosing possible problems with statistical models of this kind.
The Long-Term Tupiguarani Occupation in Southeastern Brazil
Authors: Macario K D , Buarque A , Scheel-Ybert R , Anjos R M , Gomes P R S , Beauclair M , Hatté C
Published: July 2016

We discuss some aspects of the chronology of the Tupiguarani occupation in the southeastern Brazilian coast based on the analyses of 3 charcoal samples from the Morro Grande archaeological site (Rio de Janeiro state).14C beta spectroscopy and accelerator mass spectrometry (AMS) techniques were used to determine ages of 2920 ± 70 BP, 2600 ± 160 BP, and 510 ± 160 BP. The occurrence of these ancient dates in southeastern Brazil has important implications for understanding the origin and dispersion of Tupian populations from Amazonia, supporting recent hypotheses that their expansion must have begun well before 2000 BP. On the other hand, the most recent date is a strong indication of a possible reoccupation of the site by the same cultural group around the time. These results show that the Tupiguarani occupation began at least about 3000 yr ago and lasted until its collapse with the European invasion in the 16th century.
Foraminiferous Limestone in 14C Dating of Mortar
Authors: Goslar Tomasz , Nawrocka Danuta , Czernik Justyna
Published: July 2016

Mortar as a mixture of binder and aggregate can be reliably dated with radiocarbon if the applied preparation method allows one to eliminate unburnt carbonate fragments, bearing 14C-depleted carbon and causing overestimation of 14C age. To avoid these problems, separation of specific grain-size fractions of mortar and 14C analysis of the CO2 portions collected in different time intervals of the acid-leaching reaction is usually helpful. In the present paper, we demonstrate that the rate of the leaching reaction of mortars with dense carbonate aggregate differs from that of mortars with crumbled limestone and scattered shells (e.g. of foraminifera). Verification of the obtained 14C dates against historical sources shows that for mortars rich in foraminiferous limestone, a reaction rate-based chemical elimination of “dead carbon” may appear impossible.
Investigating the Interhemispheric 14C Offset in the 1st Millennium AD and Assessment of Laboratory Bias and Calibration Errors
Authors: Hogg Alan , Palmer Jonathan , Boswijk Gretel , Reimer Paula , Brown David
Published: July 2016

Past measurements of the radiocarbon interhemispheric offset have been restricted to relatively young samples because of a lack of older dendrochronologically secure Southern Hemisphere tree-ring chronologies. The Southern Hemisphere calibration data set SHCal04 earlier than AD 950 utilizes a variable interhemispheric offset derived from measured 2nd millennium AD Southern Hemisphere/Northern Hemisphere sample pairs with the assumption of stable Holocene ocean/atmosphere interactions. This study extends the range of measured interhemispheric offset values with 20 decadal New Zealand kauri and Irish oak sample pairs from 3 selected time intervals in the 1st millennium AD and is part of a larger program to obtain high-precision Southern Hemisphere 14C data continuously back to 200 BC. We found an average interhemispheric offset of 35 ± 6 yr, which although consistent with previously published 2nd millennium AD measurements, is lower than the offset of 55–58 yr utilized in SHCal04. We concur with McCormac et al. (2008) that the IntCal04 measurement for AD 775 may indeed be slightly too old but also suggest the McCormac results appear excessively young for the interval AD 755–785. In addition, we raise the issue of laboratory bias and calibration errors, and encourage all laboratories to check their consistency with appropriate calibration curves and invest more effort into improving the accuracy of those curves.
High-Resolution Age Model Based on AMS Radiocarbon Ages for Kettle Lake, North Dakota, USA
Authors: Grimm Eric C
Published: July 2016

A high-resolution age model was developed for Kettle Lake, North Dakota, USA, from a series of 53 accelerator mass spectrometry (AMS) radiocarbon ages calibrated with Bayesian statistical methods, which provide a monotonically increasing series of calibrated ages with depth. Evident in the sediment are several slumps, debris flows, or landslides, which are confirmed by 14C dating. Removal of these facies produces a continuous sedimentary sequence for the past 13,000 yr with exception of one ≃260-yr hiatus associated with a 1.5-m-thick slump deposit. All ages except one are on terrestrial macrofossils and charcoal. A test age on aquatic organic detritus shows a hardwater effect of 600 yr at ≃2000 cal BP. Two ages from the same level on herbaceous charcoal and Chenopodium seeds are statistically the same, which further demonstrates the suitability of charcoal from grassland environments for AMS 14C age control. However, 2 specimens of wood charcoal are too old relative to bracketing ages and glacial geologic history. These ages confirm the sedimentary interpretation of redeposition and provide a caution about the longevity of wood charcoal in the environment and its suitability for age control in lacustrine sediments.
Radiocarbon Anomalies from Old CO2 in the Soil and Canopy Air
Authors: Soter Steven
Published: July 2016

The canopies of forests and cultivated fields can retard the ventilation of CO2 respired from the soil. The plants in dense canopies can then acquire a small fraction of their carbon by recycling some of the respired CO2. Furthermore, some plants can assimilate a small fraction of their carbon by uptake of CO2 in the soil via their roots. In tectonically active areas, the diffuse flux of CO2 from geological sources may be comparable to that from normal soil respiration. In such areas, both the canopy and root uptake effects may allow plants to acquire a measurable fraction of their carbon from geological sources. Because this “old” carbon lacks radiocarbon, its assimilation would increase the apparent 14C ages of the plants. These effects may account for some of the discrepancies between archaeological and 14C dates.
AMS Radiocarbon Dates from Three Shellmounds in the San Francisco Bay Area, California, USA
Authors: Schneider Tsim D
Published: July 2016

This paper presents a set of accelerator mass spectrometry (AMS) radiocarbon dates obtained from various archaeological samples collected from 3 shellmounds—CA-MRN-114, CA-MRN-115, and CA-MRN-328—within China Camp State Park, Marin County, California, USA.
A Direct Method to Measure14CO2Lost by Evasion from Surface Waters
Authors: Billett M F , Garnett M H , Hardie S M L
Published: July 2016

Recent methodological advances in the use of zeolite molecular sieves for measuring the isotopic signature of CO2have provided the opportunity to make direct measurements of14CO2 in various field situations. We linked a portable molecular sieve/pump/IRGA system to a floating chamber to demonstrate the potential of the method to quantify the isotopic signature (δ13C and14C) of CO2lost by evasion (outgassing) from surface waters. The system, which was tested on a peatland stream in Scotland, involved 1) an initial period of scrubbing ambient CO2from the chamber, 2) a period of CO2build-up caused by surface water evasion, and 3) a final period of CO2collection by the molecular sieve cartridge. The field test at 2 different sites on the same drainage system suggested that the results were reproducible in terms of δ13C and14C values. These represent the first direct measurements of the isotopic signature of CO2lost by evasion from water surfaces.
Comment On “Diet-Derived Variations in Radiocarbon and Stable Isotopes: A Case Study from Shag River Mouth, New Zealand”
Authors: Athfield Nancy Beavan
Published: July 2016

Higham et al.'s (2005) recent article in Radiocarbon 47(3) concerning diet-induced anomalies on radiocarbon ages for various faunal samples from Shag River Mouth is a well-considered study, building upon methodologies and research questions examining the phenomena of dietary anomalies addressed by Beavan Athfield and coauthors (cf. Beavan-Athfield et al. 1999, 2001a; Beavan-Athfield and Sparks 2001a,b,c). However, exception must be taken with one comment appearing in Higham et al. (2005) that suggests to the reader that there is a problem with the laboratory practice associated with rat bone dates measured at the Rafter Radiocarbon Laboratory of GNS Science, New Zealand.
Enea Radiocarbon Measurements I
Authors: Magnani Giuseppe , Bartolomei Paolo , Torretta Teresa La , Marino Ernesto Claudio , Govoni Claudio
Published: July 2016

This paper includes determinations of archeological and geological samples from different sites in central Italy performed at the Ente per le Nuove Tecnologie l'Energia e l'Ambiente (ENEA) Radiocarbon Laboratory. This laboratory has been in operation since 1985 at the ENEA Bologna Research Center.
Radiocarbon Reservoir Age Variations in the South Peruvian Upwelling During the Holocene
Authors: Fontugne Michel , Carré Matthieu , Bentaleb Ilhem , Julien Michèle , Lavallée Danièle
Published: July 2016

In Quebrada de los Burros in coastal southern Peru (Tacna department), human settlements containing shells and charcoal deposits have been excavated since 1995. The sea surface14C reservoir ages, estimated by calculating the difference of14C age between marine shells and terrestrial organic materials, exhibit high values during the lower and middle Holocene and decrease abruptly after 4000 cal BP. The increase of reservoir age at around 7000–8000 cal BP suggests an enhancement of Peruvian coastal upwelling intensity and changes in ocean circulation at intermediate depth.
Shape Analysis of Cumulative Probability Density Function of Radiocarbon Dates Set in the Study of Climate Change in the Late Glacial and Holocene
Authors: Michczyńska Danuta J , Pazdur Anna
Published: July 2016

We report on a statistical analysis of a large set of radiocarbon dates for reconstruction of paleoclimate. Probability density functions were constructed by summing the probability distributions of individual 14C dates. Our analysis was based on 2 assumptions: 1) The amount of organic matter in sediments depends on paleogeographical conditions; 2) The number of 14C-dated samples is proportional to the amount of organic matter deposited in sediments in the examined time intervals. We quantified how many dates are required to give statistically reliable results. As an example, 785 peat dates from Poland were selected. The dates encompassed the Holocene and Late Glacial period. All dates came from the Gliwice Radiocarbon Laboratory. Results were compared with other paleoenvironmental records. Detailed analysis of the frequency distributions showed that preferential sampling plays an important part in the shape determination. The general rule to take samples from locations where visible changes of sedimentation are apparent (e.g. from the top and the bottom of the peat layer) results in narrow peaks in the probability density function near the limits of the Holocene subdivision.
Sources of Anthropogenic 14C to the North Sea
Authors: Gulliver P , Cook G T , MacKenzie A B , Naysmith P , Anderson R
Published: July 2016

The Sellafield nuclear fuel reprocessing plant on the northwest coast of England is the largest source of anthropogenic radiocarbon to the UK coastal environment. In a mid-1990s study of 14C distribution around the UK coast, the pattern of dilution with increasing distance from Sellafield appeared to be perturbed by anomalously high 14C activities in marine biota in the coastal environment of northeast England. This present study was undertaken during 1998 and 1999 to determine whether this 14C enhancement was due to Sellafield or the nuclear power plants on the east coast. Seawater, seaweed (Fucus sp.), and mussel (Mytilus edulis) samples that were collected from the vicinity of the Torness and Hartlepool advanced gas-cooled reactor (AGR) nuclear power stations were all enhanced above the contemporary regional background activity derived from natural production and atmospheric nuclear weapons testing. We used previously published dilution factors and transfer times for 99Tc between Sellafield and various points on the UK coast to determine likely Sellafield-derived 14C contributions to the activities at the nuclear power plant sites. The results suggest that the activities observed at Torness, which are only marginally enhanced above the natural background activity, are possibly due to discharges from Sellafield; however, the significant 14C enhancements at Hartlepool are not Sellafield-derived. Furthermore, since both reactors have the same fundamental design, the low activities at the Torness AGR imply that the activities at Hartlepool are not from the AGR, suggesting that there is an input of 14C to the marine environment in the vicinity of Hartlepool which is probably non-nuclear-power related. However, there is no other authorized site in the area that could account for the observed 14C enrichments; therefore, further research is required to ascertain the source of this 14C.
Stepped-Combustion 14C Dating of Bomb Carbon in Lake Sediment
Authors: McGeehin J , Burr G S , Hodgins G , Bennett S J , Robbins J A , Morehead N , Markewich H
Published: July 2016

In this study, we applied a stepped-combustion approach to dating post-bomb lake sediment from north-central Mississippi. Samples were combusted at a low temperature (400 °) and then at 900 °. The CO2 was collected separately for both combustions and analyzed. The goal of this work was to develop a methodology to improve the accuracy of 14C dating of sediment by combusting at a lower temperature and reducing the amount of reworked carbon bound to clay minerals in the sample material. The 14C fraction modern results for the low and high temperature fractions of these sediments were compared with well-defined 137Cs determinations made on sediment taken from the same cores. Comparison of “bomb curves” for 14C and 137Cs indicate that low temperature combustion of sediment improved the accuracy of 14C dating of the sediment. However, fraction modern results for the low temperature fractions were depressed compared to atmospheric values for the same time frame, possibly the result of carbon mixing and the low sedimentation rate in the lake system.
Radiocarbon Concentration in the Atmosphere and Modern Tree Rings in the K0052Aków Area, Southern Poland
Authors: Rakowski Andrzej , Kuc Tadeusz , Nakamura Toshio , Pazdur Anna
Published: July 2016

New results of radiocarbon concentration in tree rings from the Kraków region covering a growth period of 20 yr have been analyzed, and the relationship between them and 14C concentrations in the atmospheric CO2 are described. This enabled assessment of the uptake period for pine trees at the regional climatic conditions. Both sets of data show lower 14C concentrations than reported for “clean air” at the reference station, indicating a remarkable input of “dead” CO2 of fossil fuel origin. Using data of carbon dioxide and 14C concentrations from Schauinsland, summer values of the fossil component (Cf) in carbon dioxide were calculated for the Kraków area. Fitting exponential and linear functions to experimental data, the exchange time was calculated, and expected future 14C concentration in the atmosphere was estimated.
Radiocarbon in Annual Tree Rings from Thailand During the Pre-Bomb Period, Ad 1938–1954
Authors: Hua Quan , Barbetti Mike , Zoppi Ugo
Published: July 2016

Annual tree rings from Thailand were analyzed by radiocarbon AMS for AD 1938–1954. The results showed no significant depletion in atmospheric 14C over Thailand during the pre-bomb period, even though the air mass to Thailand during the growing season of tree rings is transported over a potentially significant source of oceanic 14C-depleted CO2, out-gassing in the northern Indian Ocean. When compared with Washington and Chile for different periods from the 17th century to AD 1954, Thailand appears to have the characteristics of Southern Hemisphere 14C. This supports our previous finding that Thailand was strongly influenced by the entrainment of Southern Hemisphere air parcels in the southwest Asian monsoon (Hua et al. 2004). For Thailand, this effect is much stronger than the reduction of atmospheric 14C in association with CO2 out-gassing in the northern Indian Ocean.
Anu Radiocarbon Date List IV
Authors: Polach H. A. , Lovering J. F. , Bowler J. M.
Published: July 2016

The present date list describes the first stage of a co-operative study on the validity of dating secondary soil carbonates in arid and semi-arid environments of Australia. Because of the complex nature of the physical and chemical variables in a soil environment, many additional samples are being dated from stratigraphically controlled sites before final evaluation of carbonate reliability is possible.
Radiocarbon Dates of the Institute of Archaeology II
Authors: Dolukhanov P. M. , Romanova Ye. N. , Semyontsov A. A.
Published: July 2016

The present list covers samples measured between 1963 and July, 1967. Three previous lists have been published in Leningrad I (Sovetskaya arkheologiya, 1961, p. 3); Leningrad II (The Absolute Geochronology of the Quaternary Period, 1963); and Leningrad III (New Methods in Archaeological Investigations, 1963, p. 9–56). The samples measured include charcoal from cultural layers and hearths, wood from barrows [kurgans] and cemeteries, wooden tools from peat deposits, and mounds, as well as peat and animal tissue.
Belfast Radiocarbon Dates I
Authors: Smith A. G. , Pearson G. W. , Pilcher J. R.
Published: July 2016

The dating equipment in the Queen's University Palaeoecology Laboratory was installed to provide data for research projects, initially dealing with the development of agriculture, in the departments of Botany and Archaeology.
Belfast Radiocarbon Dates II
Authors: Smith A. G. , Pearson G. W. , Pilcher J. R.
Published: July 2016

The dating equipment in the Palaeoecology Laboratory has remained essentially as described in Belfast I (this volume). Rewiring of the counter has increased the detection efficiency slightly. Background count corrected to 1606 mb is now 11.0 counts/min and the net count rate for 95% of the NBS oxalic acid standard is 56.0 counts/min. All charcoal samples have been pretreated in accordance with the schedule given in Belfast I.
Trondheim Natural Radiocarbon Measurements III
Authors: Nydal Reidar
Published: July 2016

This date list covers most of the datings done during the period January 1960 to December 1961.
La Jolla Natural Radiocarbon Measurements IV
Authors: Hubbs Carl L. , Bien George S. , Suess Hans E.
Published: July 2016

During 1963 and 1964 the La Jolla Radiocarbon Laboratory continued to follow essentially the same techniques as in previous years. The three counters described in La Jolla III have continued to yield measurements in virtually complete agreement. As before, we add, except for the measurements of apparent age on organisms collected alive (see below), ca. 100 yr to the one-sigma statistical counting error. Dates are still computed on the basis of the half-life estimate of 5570 yr.
Ohio Wesleyan University Natural Radiocarbon Measurements II
Authors: Ogden J. Gordon , Hay Ruth J.
Published: July 2016

The following is a list of dates obtained since the compilation of our first list in November, 1963. Equipment and operating procedures are the same with the exception that a gas chromatograph has been added to confirm the purity of the methane samples used for dating.
“Quickie” 14C Dates
Authors: Michael Henry N , Ralph Elizabeth K
Published: July 2016

The extension of the bristlecone pine chronology, which is, thus far, the only complete tree-ring-dated series that extends beyond 6000 bc and which is used for the calibration of radiocarbon dates, has been going on over the past 22 years, that is, ever since Schulman (1956; 1958) established the extremely old ages of the bristlecone pine. The few people in this world who search for very old wood samples to extend a dendrochronology may appreciate a method of establishing quickly the approximate ages of the samples.
Teledyne Isotopes Radiocarbon Measurements XII
Authors: Buckley James , Valdes-Pages Cynthia
Published: July 2016

This date list reports samples completed before 1979. Methods, equipment, and techniques were reported previously (R, 1968, v 10, p 246; R, 1970, v 12, p 87). Age calculations are based on the conventional 14C half-life of 5568 years. The working laboratory standard is 95% of the NBS oxalic acid standard (SRM 4990). Results are reported in years before 1950 and the standard deviation is based on counting statistics of sample, background, and modern standard. Corrections for δ13C are not included.
Carbonate14C Background: Does It Have Multiple Personalities?
Authors: Nadeau Marie-Josée , Grootes Pieter M , Voelker Antje , Bruhn Frank , Duhr Alexander , Oriwall Angelika
Published: July 2016

Measurements of the radiocarbon concentration of several carbonate background materials, either mineral (IAEA C1 Carrara marble and Icelandic double spar) or biogenic (foraminifera and molluscs), show that the apparent ages of diverse materials can be quite different. Using 0.07 pMC obtained from mineral samples as a processing blank, the results from foraminifera and mollusc background samples, varying from 0.12 to 0.58 pMC (54.0-41.4 ka), show a species-specific contamination that reproduces over several individual shells and foraminifera from several sediment cores. Different cleaning attempts have proven ineffective, and even stronger measures such as progressive hydrolization or leaching of the samples prior to routine preparation, did not give any indication of the source of the contamination. In light of these results, the use of mineral background material in the evaluation of the age of older unknown samples of biogenic carbonate (>30 ka) proves inadequate. The use of background samples of the same species and provenance as the unknown samples is essential, and if such material is unavailable, generic biogenic samples such as mixed foraminifera samples should be used. The description of our new modular carbonate sample preparation system is also introduced.
Dating of Cremated Bones
Authors: Lanting J N , Aerts-Bijma A T , van der Plicht J
Published: July 2016

When dating unburnt bone, bone collagen, the organic fraction of the bone, is used. Collagen does not survive the heat of the cremation pyre, so dating of cremated bone has been considered impossible. Structural carbonate in the mineral fraction of the bone, however, survives the cremation process. We developed a method of dating cremated bone by accelerator mass spectrometry (AMS), using this carbonate fraction. Here we present results for a variety of prehistoric sites and ages, showing a remarkable success rate for this method.
Stepped-Combustion 14C Dating of Sediment: A Comparison with Established Techniques
Authors: McGeehin J , Burr G S , Jull A J T , Reines D , Gosse J , Davis P T , Muhs D , Southon J R
Published: July 2016

Radiocarbon dating of bulk sediment has long been used as a method of last resort when reliable wood, charcoal, or plant macrofossils are not available for analysis. Accurate dating of sediment is complicated by the presence of multiple organic carbon fractions, each with a potentially different 14C activity. Additionally, the presence of carbon bound by clay minerals can significantly reduce the accuracy of a sediment age determination, with the oldest 14C ages seen in samples with the highest clay content (Scharpenseel and Becker-Heidmann 1992).
Near East Chronology: Towards an Integrated 14C Time Foundation
Authors: Bruins Hendrik J
Published: July 2016

Chronology is the backbone of all history, as the flow of time is identical in scholarly and scientific fields, even in the Near East. Radiocarbon dating can provide an essential and unifying chronological basis across disciplines, despite precision limitations. This issue presents exciting new 14C developments in archaeological and environmental contexts, ranging from Proto-Neolithic cultures to historic earthquakes along the Dead Sea. Dark periods devoid of settlement in the deserts of the southern Levant seem to disappear with 14C dating. Significant new findings collectively indicate the need for major chronological revisions in the 4th and 3rd millennia BCE in Egypt and the Levant. The implications for the 2nd millennium BCE are not yet established, but the use of 14C dating in the Iron Age is finally beginning to focus on current controversies. The chronological way forward for Dynastic Egypt and the Levantine Bronze and Iron Ages is a multi-disciplinary approach based on detailed high-quality 14C series as a unifying time foundation to anchor archaeological, textual, and astronomical data.
How to Convert Biological Carbon Into Graphite for AMS
Authors: Getachew Girma , Kim Seung-Hyun , Burri Betty J , Kelly Peter B , Haack Kurt W , Ognibene Ted J , Buchholz Bruce A , Vogel John S , Modrow Jonathan , Clifford Andrew J
Published: July 2016

Isotope tracer studies, particularly radiocarbon measurements, play a key role in biological, nutritional, and environmental research. Accelerator mass spectrometry (AMS) is now the most sensitive detection method for14C, but AMS is not widely used in kinetic studies of humans. Part of the reason is the expense, but costs would decrease if AMS were used more widely. One component in the cost is sample preparation for AMS. Biological and environmental samples are commonly reduced to graphite before they are analyzed by AMS. Improvements and mechanization of this multistep procedure is slowed by a lack of organized educational materials for AMS sample preparation that would allow new investigators to work with the technique without a substantial outlay of time and effort. We present a detailed sample preparation protocol for graphitizing biological samples for AMS and include examples of nutrition studies that have used this procedure.
Verification of an Archaic Age Occupation on Barbados, Southern Lesser Antilles
Authors: Fitzpatrick Scott M
Published: July 2016

The Caribbean Archaic Age (about 3000–500 BC) is thought to represent the earliest migration of humans from South America into the Lesser Antilles. However, there is a conspicuous absence of these early sites on islands south of the Guadeloupe Passage. To date, only a single radiocarbon date derived from a Queen conch (Strombus[Eustrombus]gigas) shell at the Heywoods site on Barbados was indicative of an Archaic occupation in the southern Antilles apart from a scattering of poorly reported (and mostly undated) sites. Given a number of issues associated with reliance on a single date to establish a cultural horizon, along with other problems derived from possible carbonate cement contamination and dating marine shells of a longer-lived species such as Queen conch, 2 additional samples were taken from the same unit and context at Heywoods to confirm whether the site is truly representative of an occupation during the Archaic Age. Results from a Queen conch shell adze in Context 7 dated to 2530–2200 BC (2 σ) and overlaps with the only other Archaic date from the site dating to 2320–1750 cal BC, while a juvenile specimen of the same species from Context 8 at 3280–2940 BC (2 σ) indicates that Barbados may have been settled even earlier. This suggests that Heywoods may be the oldest site between Trinidad and Puerto Rico. While further confirmation is required, these new dates have implications for understanding the nature of migratory ventures in the Caribbean, such as whether the “Southward Route” hypothesis—which postulates that earlier migration events from South America during the Ceramic Age (beginning ∼500 BC) initially bypassed the southern Lesser Antilles—also applies to the Archaic, and if other phenomena such as active volcanism may have played a role in structuring settlement patterns. Questions also remain as to why Heywoods does not exhibit the typical lithic Archaic tool kit.
Using a Silica Substrate to Monitor the Effectiveness of Radiocarbon Pretreatment
Authors: Dee M W , Brock F , Bowles A D , Ramsey C Bronk
Published: July 2016

The objective of radiocarbon pretreatment is to eliminate any contaminant carbon from the sample material. Solvent washes and acid-base-acid (ABA) procedures are widely used for this purpose. However, quantitatively analyzing their effectiveness is surprisingly problematic, as it often requires large numbers of 14C measurements or high-precision compositional analysis. The technique presented here involves monitoring the impact of different forms of contamination by measuring their adherence to a non-carbonaceous substrate called Chromosorb®. Firstly, the substrate was used in place of a 14C sample in order to monitor the accrual of carbon contamination during a standard solvent wash and ABA pretreatment. This produced a contamination profile against which modifications to the pretreatment procedure could be compared. Secondly, stocks were prepared of Chromosorb that had been infused with environmental contaminants and with common glues, adhesives, and preservatives. By monitoring the elimination of carbon from these stocks, the effectiveness of different pretreatment procedures could be evaluated and the most problematic of the contaminants for 14C dating could be identified.
Magnesium Perchlorate as an Alternative Water Trap in AMS Graphite Sample Preparation: A Report On Sample Preparation at Kccams at the University of California, Irvine
Authors: Santos G M , Southon J R , Druffel-Rodriguez K C , Griffin S , Mazon M
Published: July 2016

We present a brief discussion of sample preparation procedures at the Keck Carbon Cycle Accelerator Mass Spectrometer (KCCAMS), University of California, Irvine, and a systematic investigation of the use of Mg(ClO4)2 as an absorptive water trap, replacing the standard dry ice/ethanol cold finger in graphite sample preparation. We compare high-precision AMS measurement results from oxalic acid I and USGS coal samples using Mg(ClO4)2 under different conditions. The results obtained were also compared with those achieved using the conventional water removal technique. Final results demonstrate that the use of Mg(ClO4)2 as an alternative water trap seems very convenient and reliable, provided the Mg(ClO4)2 is replaced frequently.