bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculating Sediment Compaction for Radiocarbon Dating of Intertidal Sediments
Authors: Bird M I , Fifield L K , Chua S , Goh B
Published: July 2016

This study estimates the maximum and minimum degrees of autocompaction for radiocarbon-dated Holocene mangrove sediments in Singapore, in order to correct apparent sediment accretion rates for the effects of sediment compression due to autocompaction. Relationships developed for a suite of modern (surface) sediment samples between bulk density, particle-size distribution, and organic matter content were used to estimate the initial (uncompacted) bulk density of buried and variably compressed Holocene sediments, based on the grain-size distribution and organic matter content of the sediment. The difference between measured (compacted) and initial (uncompacted) bulk density of each buried sediment interval can be interpreted as the amount of length shortening experienced by each interval since burial. This allows the elevation of samples selected for 14C dating to be corrected for the effects of autocompaction of the underlying sediment sequence, so that accurate estimates of vertical sediment accretion rates can be calculated.

The 3 Holocene mangrove sequences analyzed and dated for this study ranged in age from 2000 to 8500 cal BP. The effects of autocompaction are significant, even in comparatively thin sequences, with subsidence of up to 56 cm calculated for carbon-dated samples presently 2 m above incompressible basement. The vertical sediment accretion rates for these mangrove sequences ranged from 0.99 to 6.84 mm/yr and carbon sequestration rates ranged from 0.9 to 1.7 t/ha/yr, all within the range observed for comparable Holocene and modern mangrove sediments elsewhere.
Survey of the Dispersion of 14C in the Vicinity of the UK Reprocessing Site at Sellafield
Authors: Otlet R L , Walker A J , Fulker M J
Published: July 2016

We have been measuring 14C in natural, biological materials growing in the vicinity of Sellafield, Cumbria as a continuing project with BNFL to understand the dispersion of releases from the site over several seasons. We have measured locally grown foodstuffs for monitoring purposes, individual tree rings to establish a chronology of releases, hawthorn berries for spatial investigations and are now carrying out controlled plot uptake experiments. We have been attempting to validate a current dispersion model (Clarke 1979) over a six-year period, and although we observe general agreement in most years, certain anomalies, which probably relate to topographical features, are leading to more detailed correlation with local meteorological data.
Memory Effects in an AMS System: Catastrophe and Recovery
Authors: Vogel J S , Southon J R , Nelson D E
Published: July 2016

A sample with a 14C concentration estimated to be greater than 30,000 Modern was inadvertently graphitized and measured in an AMS system. No measurable contamination of the cesium sputter ion source was observed. Simple cleaning procedures removed the contamination from the sample preparation system, with the exception of the reaction vessel in which the sample was graphitized. Sample cross-contamination factors were estimated for all of the preparation and measurement procedures.
Dating the Turin Shroud—An Assessment
Authors: Gove H E
Published: July 2016

An assessment is made of the credibility of the radiocarbon dating of the shroud of Turin. The quoted final results produced a calibrated calendar age range of AD 1260–1390 for the linen of the Turin shroud at a 95% confidence level. The measurements were carried out independently in three accelerator mass spectrometry (AMS) laboratories located at the University of Arizona, Tucson, Arizona, USA, Oxford University, Oxford, England, and ETH-Hönggerberg, Zürich, Switzerland with assistance for certification and data analysis provided by the British Museum. The author concludes that, although the procedures followed differed substantially from those recommended at a workshop organized by the Pontifical Academy of Sciences, the results are credible. Although of negligible scientific value, they represent a major public triumph for the AMS method of carbon dating. However, many doubts have been raised, both real and fanciful, concerning the validity of the results and these are discussed. It is suggested that steps should be taken to conserve the shroud and that permission should be given for its examination by experts in medieval art.
Harwell Radiocarbon Measurements VIII
Authors: Walker A J , Williams Nigel , Otlet R L
Published: July 2016

Following Harwell Measurements VI (Walker & Otlet 1988) this is the second of the series of lists of English archaeological dates commissioned for measurement by the Historic Buildings and Monuments Commission for England and Wales within prescribed contractual periods. This list, containing 176 dates, refers to the period, April 1986 to March 1987, and results are reported irrespective of whether the associated projects are completed or ongoing.
Calibrating New Zealand Radiocarbon Dates of Marine Shells
Authors: McFadgen B G , Manning M R
Published: July 2016

Radiocarbon activity of 11 modern marine shell samples from the New Zealand region is enhanced compared with the surface layers of the average world ocean. The measured enhancement, δR, is equivalent to −31 ± 13 years. On this basis, the Institute of Nuclear Sciences will now use a value of −30 years in reporting calibrated ages for marine shell samples.
Applicability of ‘New Technology’ Scintillation Counters (Packard 2000 CA/LL and 2260 XL) for 14C Dating
Authors: Cook G T , Hold A G , Naysmith Philip , Anderson Robert
Published: July 2016

The results of this study indicate that scintillation counters employing burst-counting circuitry are capable of producing accurate age measurements. Replicate analyses confirm the validity of the minimum error of 50-60 years quoted on routine age measurements carried out at this laboratory.
Shell Hash Dating and Mixing Models for Palimpsest Marine Sediments
Authors: Roy Peter S.
Published: July 2016

The dating of palimpsest marine sediments using broken shell fragments (shell hash) is considered to be a necessary but unreliable technique because of the mixed age of the fragments. An analysis of geological mixing models and radiocarbon data on shell hash from sandy sediments on the southeast Australian coast and shelf are used to examine the possibility for simulating the depositional processes, and thus, to better understand the age structure of the deposits.
14C Age Corrections in Antarctic Lake Sediments Inferred from Geochemistry
Authors: Zale Rolf
Published: July 2016

Sediment from Lake Boeckella, Antarctic Peninsula, is richer in Ca, Cd, Cu, P, Sr and Zn than that of six other lakes in the area. The elements originate from Adélie penguin (Pygoscelis adeliae) guano on the lake shores. Changing Cu and P concentrations in the lake sediment are used as a proxy for penguin influence on the lake sediment from ca. 5850 bp to present. A 14C dating model suggests that the 14C correction factor in the lake sediments depends on the penguin proxy, the apparent age of the penguin guano and the amount of particulate carbon originating from the carbon-bearing shales in the watershed. Glacial meltwater and dissolved carbonates do not contain enough “old” carbon to contribute significantly to the correction factor. Ages corrected with the 14C dating model agree with the depth vs. age curve based on independently 14C-dated tephra horizons. The reservoir effect has been constant since at least 5800 bp, implying long-term stability of the currents and water masses in the area. The existing chronology for Lake Boeckella has been recalculated. The period of glacial advance, previously thought to have culminated at 5000 bp, is now thought to have culminated at 4700 bp; deglaciation of the area is thought to have occurred at 6300 bp instead of 8680 bp.
Radiocarbon Calibration Curve Variations and Their Implications for the Interpretation of New Zealand Prehistory
Authors: McFadgen B.G. , Knox F. B. , Cole T. R. L.
Published: July 2016

The shape of a distribution of calibrated 14C dates displays spurious peaks and troughs, brought about by changes in the slope of the calibration curve interacting with the spreading effect of the stochastic distribution of counting errors. The distortion results in a positive correlation between the numbers of dates per calendar year and the slopes of the calibration curves, for assemblages of archaeological dates from such widely separated areas as British Columbia, South Australia and New Zealand. The distortion also increases the possibility of date reversals, and increases the overall spread of calibrated 14C dates. After taking into account this systematic distortion and inbuilt age of charcoal and wood samples, we estimate dates for the initial settlement and first appearance of fortifications, and infer a likely trend of population growth for prehistoric New Zealand.
Physical Research Laboratory (Chemistry) Radiocarbon Date List I
Authors: Bhushan Ravi , Chakraborty Supriya , Krishnaswami Seth
Published: July 2016

We present here radiocarbon dates obtained using a liquid scintillation system installed at the Physical Research Laboratory (PRL), which has been in operation for the past three years for14C measurements of oceanographic and geochemical samples from India.
Rudjer Bošković Institute Radiocarbon Measurements XIII
Authors: Obelić Bogomil , Horvatinčić Nada , Srdoč Dušan , Krajcar Bronić Ines , Sliepčević Adela , Grgić Sanja
Published: July 2016

In this list, we present 14C ages of archaeological, geological, hydrogeological, botanical and atmospheric samples measured since our previous list (Srdoč et al. 1992). Chemical pretreatment and counting techniques using a methane-filled proportional counter are essentially the same as reported earlier. Sample descriptions are prepared in collaboration with collectors and submitters.
Radiocarbon AMS Dating of Pollen Concentrated from Eolian Sediments: Implications for Monsoon Climate Change Since the Late Quaternary
Authors: Zhou Weijian , Donahue Douglas , Jull A. J. T.
Published: July 2016

Dating pollen concentrated from eolian sediments provides a new way to establish a chronological framework on the Loess Plateau of China. We show that pollen deposited simultaneously with sediment in a stable environment can provide reliable ages. We suggest that the reliability of pollen dating can be evaluated by comparison with wood cellulose or charcoal ages from the same stratigraphic level. Dating pollen concentrates from the various profiles indicates paleomonsoon precipitation variability at the loess/desert transitional belt from the late Pleistocene to the early Holocene.
Bomb 14C Recorded in Laminated Speleothems: Calculation of Dead Carbon Proportion
Authors: Genty Dominique , Massault Marc
Published: July 2016

We performed radiocarbon measurements using accelerator mass spectrometry (AMS) on 6 stalagmites 3 stalactites and 7 seepage waters from four different caves in Southwest France and Belgium in order to calculate the dead carbon proportion (dcp). All the speleothems studied are modern and annually laminated, which offers the advantage of an accurate chronology, with better than one-year resolution. Coupled with the fact that very little calcite is necessary for an AMS measurement (between 1.5 and 7 yr of calcite deposit), we obtained dead carbon values within an uncertainty limit of ± 1.5%. Results show that the dead carbon proportion varies from 9.2% to 21.9% for calcite deposits and from 3.6% to 21.9% for water. In each sampling site, the dcp is homogeneous. Although the inter-site dcp varies by >11%, its average value of 15.5% ± 4.4 still lies within the uncertainty range of the accepted value of 15% ± 5 (dilution factor of 0.85 ± 0.5). We compare the average dcp of each site with the local geology, vegetation and climate. Given similar geology and temperature the highest dcp values are found under forest cover; dcp difference is up to 9%. However, the Belgian site, which is also under a forest shows a dcp very close to the dcp found under grassland sites of Southwest France, which proves that other unknown factors may play an important role in dissolution processes. Secondary calcite deposition and redissolution in the soil zone or more likely in the fracture system before reaching the cave itself could also explain the inter-site differences. The IAEA isotopic model (Pearson model adapted for open systems) is in good agreement with the measured activities.
University of Granada Radiocarbon Dates VII
Authors: González-Gómez Cecilio , Villafranca-Sánchez Elena
Published: July 2016

This paper includes determinations of archaeological, geological and palaeobotanical samples from Spain and Portugal, measured at the University of Granada Radiocarbon Dating Laboratory, from 1990 to 1991. Pretreatment of charcoal and wood samples is a standard acid-basic procedure using 8% HCl and 2% NaOH at boiling temperature. The collagen of bone samples is obtained by the Longin (1971) method. The method of dating is benzene synthesis and liquid scintillation counting.
KSU Radiocarbon Dates II
Authors: Yamada Osamu
Published: July 2016

This date list mainly reports on samples processed from 1982 to 1991. Each sample is converted to methanol. Radiocarbon is measured in a Teflon™ vial containing a mixture of 40 g of methanol and 50 cc of xylene, 1% Butyl PBD and 0.1% PBBO using low-background scintillation counters Aloka LSC-800, LB-I and LB-III. The background of LB-III is ca. 8 cpm and counting efficiency is ca. 70%. The recent 14C standard used is 95% of NBS oxalic acid; 5568 yr is used as the half-life of 14C.
Paleoenvironment in Dae-Am San High Moor in the Korean Peninsula
Authors: Yoshioka T , Lee J-Y , Takahashi H A , Kang S-J
Published: July 2016

We discuss paleoenvironmental changes at the Dae-Am San high moor, located near the Demilitarized Zone at 38°N. This area has been reported to be the only high moor in the Korean peninsula. The 14C age of the bottom sediment (75–80 cm in depth) at this site is about 1900 BP. Since the radiocarbon ages for the intervals at 50–55 cm and 75–80 cm were almost the same, we conclude that the deep layers (55–80 cm) in the high moor were all part of the original soil. Low organic C and N contents in the deeper layers support this inference. The 50–55-cm layer consists of sandy material with very low organic content, suggesting erosion from the surrounding area. The surface layer (0–5 cm) was measured as 190 BP, and the middle layer (30–35 cm) was 870 BP. The bulk sedimentation rate was estimated to be about 0.4 mm yr−1 for the 0–30-cm interval. The δ13C value of organic carbon in the sediments fluctuated with depth. The δ13C profile of the Dae-Am San high moor may be explained by climatic changes which occurred during the Little Ice Age and Medieval Warm Period.
Distribution of 14C and 13C in Forest Soils of the Dinghushan Biosphere Reserve
Authors: Shen Chengde , Yi Weixi , Sun Yanmin , Xing Changping , Yang Ying , Yuan Chao , Li Zhian , Peng Shaolin , An Zhisheng , Liu Tungsheng
Published: July 2016

We report here first results on the bulk soil organic carbon (SOC), apparent radiocarbon ages and δ13C characteristics of the tropical and subtropical forest soil in Dinghushan Biosphere Reserve (DHSBR). The forest oxisol in Dinghushan has developed during the Holocene. The δ13C variation curves in all three profiles may be divided into two sections. The upper section from 0 to 40 cm has δ13C values varying from −27.4 to −24.1‰, −27.5 to −22.2‰, and −24.4 to −20.1‰. in the Wukesong, Qingyunsi and Kengkou profiles, respectively. The lower section, including the 40–160 cm horizons, has a uniform δ13C. The mean δ13C values of the soil organic carbon could be used not only to discriminate between C3 and C4 plants, but also to distinguish between coniferous and broad-leaf plants.
5.2-5.8 ka BP Paleoenvironment of the Southern Slope of Mount Raizan, Japan
Authors: Okuno Mitsuru , Nagaoka Shinji , Hase Yoshitaka , Mori Yuichi , Konomatsu Masahiko , Takahashi Toshihiko , Nakamura Toshio , Nishida Tamio
Published: July 2016

Accelerator mass spectrometry (AMS) radiocarbon dating and paleoecological analysis of slope deposits at Mt Raizan provided seven 14C dates indicating that landslides occurred in that area at 6.0 to 6.3 cal ka BP and 6.5 cal ka BP. Plant macrofossils, pollen grains, and spores point to a mixed forest at that time, consisting of conifers and broad-leaved trees. On the other hand, insect fossil indicates slightly colder climate than that of the flora. This difference may be attributed to varied sensitivities of each proxy to climatic changes.
The Source of the Yarkon Springs, Israel
Authors: Avisar D , Kronfeld J , Kolton J , Rosenthal E , Weinberger G
Published: July 2016

Radiocarbon and tritium analyses are used to show that the accepted conceptual hydrological model of the Yarkon-Taninim aquifer is untenable. The conventional model would have the groundwater flow in the carbonate Judea Group aquifer from the Beer Sheva region in the south to discharge at the Yarkon springs. Moreover, the conventional model considers the Judea Group aquifer to be a single hydrological entity. However, analysis of the Yarkon springs and surrounding wells demonstrate that it is stratified into upper and lower aquifers.

The water in the deeper aquifer is fresher, cooler and younger compared to the water in the overlying aquifer. The deeper aquifer water type is identical in composition to the Ca-Mg-HCO3 Judean Hills recharge water immediately to the east. It is this recharge water that is dominant at the Yarkon Springs. There appears to be no derived appreciable contribution of groundwater from the Beersheva region in the south. Thus the currently accepted hydrologic model is in need of serious revision. The present study introduces new and high quality groundwater resources to be target for exploitation.
Calibration of Lacustrine Sediment Ages Using the Relationship Between 14C Levels in Lake Waters and in the Atmosphere: The Case of Lake Kinneret
Authors: Stiller Mariana , Kaufman Aaron , Carmi Israel , Mintz Genia
Published: July 2016

The source of endogenic organic and inorganic carbon in lacustrine sediments is the dissolved inorganic carbon (DIC) in the lake water. The relation between the radiocarbon levels of DIC in Lake Kinneret and of CO2 in the atmosphere has been investigated. The ratio of the former to the latter was found to be 0.814 ± 0.013. This ratio is used for calibrating the age of the sediment according to the natural fluctuations in the atmospheric levels of 14C that occurred during the past 10,000 years.
Transport of Sellafield-Derived 14C from the Irish Sea through the North Channel
Authors: Gulliver Pauline , Cook Gordon T , MacKenzie Angus B , Naysmith Philip , Anderson Robert
Published: July 2016

Since the early 1950s, the Sellafield nuclear fuel reprocessing plant in Northwest England has released radiocarbon into the Irish Sea in a mainly inorganic form as part of its authorized liquid effluent discharge. In contrast to the trend in which the activities of most radionuclides in the Sellafield liquid effluent have decreased substantially, 14C discharges have increased since 1994–95. This has largely been due to a policy change favoring marine discharges over atmospheric discharges. 14C is radiologically important due to its long half life, mobility in the environment, and propensity for entering the food chain. Current models for radionuclide dispersal in the Irish Sea are based on a reversible equilibrium distribution coefficient (kd), an approach which has been shown to be inadequate for 14C. Development of predictive models for the fate of Sellafield-derived 14C requires a thorough understanding of the biogeochemical fluxes between different carbon reservoirs and the processes controlling the net flux of 14C out of the Irish Sea, through the North Channel. In this study, both an empirical and a halving time approach indicate that close to 100% of the 14C that is discharged from Sellafield is dispersed beyond the Irish Sea on a time-scale of months in the form of DIC, with little transfer to the PIC, POC, and DOC fractions, indicating that the “dilute and disperse” mechanism is operating satisfactorily. This is consistent with previous research that indicated little transfer of 14C to Irish Sea sediments. While significant 14C enhancements have been observed in the biota of the Irish Sea, this observation is not necessarily in conflict with either of the above as the total biomass has to be taken into account in any calculations of 14C retention within the Irish Sea.
Radiocarbon Dating of the Human Occupation of Australia Prior to 40 ka BP—Successes and Pitfalls
Authors: Fifield L K , Bird M I , Turney C S M , Hausladen P A , Santos G M , di Tada M L
Published: July 2016

Charcoal samples from ancient human occupation sites in Australia have been subjected to a rigorous pretreatment and stepped combustion regime in order to explore the possibility that these sites may be older than previous radiocarbon dating had suggested. In one case, the Devil's Lair site in southwest Australia, the methodology has clearly removed vestiges of contamination by more modern carbon and has led to a revised radiocarbon chronology that provides evidence for human occupation of southwest Australia by at least 44 ka BP and probably by 46–47 ka BP. In contrast, charcoal from the Nauwalabila site has been so severely altered that insufficient of the original carbon remains for reliable 14C dating. Finally, where the charcoal is well preserved, such as at the Carpenter's Gap site, the new results provide reassurance that earlier 14C results of ∼40 ka BP are indeed true ages and are not simply at the limit of the 14C technique.
Performance Evaluation of the New AMS System at Accium BioSciences
Authors: Zoppi Ugo , Crye James , Song Qi , Arjomand Ali
Published: July 2016

A new compact accelerator mass spectrometry (AMS) system dedicated to the measurement of radiocarbon has been commissioned at the Accium BioSciences headquarters in Seattle. The entire facility (including ancillary laboratories for the preparation of graphite targets) has been designed to handle samples with a wide range of 14C concentrations. In this paper, we discuss the technical details of the new facility and present performance test results demonstrating state-of-the-art capabilities. In particular, modern samples can be readily measured with 0.3% precision and accuracy, machine background levels are consistently in the low 10-16 (14C/12C), and chemical background is approximately equivalent to a fraction of modern of 0.004. In addition, when 100-times-modern samples were processed, no increase in background was observed, either during sample processing or during AMS measurement. This corresponds to a dynamic range for 14C analysis of 6 orders of magnitude.
Quality Assurance of Ultrafiltered Bone Dating
Authors: Brock Fiona , Ramsey Christopher Bronk , Higham Thomas
Published: July 2016

Ultrafiltration of bone collagen provides a method of purification that can be very effective in reducing environmental contamination from soil-derived amino acids as well as removing degraded collagen or other short-chain proteins. The Oxford Radiocarbon Accelerator Unit (ORAU) first implemented ultrafiltration in the pretreatment of bone material for accelerator mass spectrometry (AMS) radiocarbon dating in 2000. However, the filters themselves contain carbonaceous material, and thus stringent quality control is required to demonstrate that this does not affect the accuracy of the dating. Here, we present quality assurance data from the bone pretreatment and dating program at ORAU, including dates on known-age and background-age bones over a range of sample sizes, and measurements of residual carbon contamination present in the filters after cleaning.
How Clean is Ultrafiltration Cleaning of Bone Collagen?
Authors: Hüls Matthias C , Grootes Pieter M , Nadeau Marie-Josée
Published: July 2016

As part of our bone dating development, we have tested the ultrafiltration of bone gelatin using 2 different filters—Vivaspin 20™ (VS20), a polyethersulfone, and Vivaspin 15R™ (VS15R), a cellulose, both with a 30,000 molecular weight cutoff—and bone collagen from dated samples ranging in age from 1.5 to >50 kyr BP. A direct accelerator mass spectrometry (AMS) measurement yielded radiocarbon concentrations of ∼0.5 pMC (∼42 kyr) for the polyethersulfone, ∼14.4–17.5 pMC (∼15.6–14 kyr) for the cellulose, and ∼107.4 pMC for the glycerin. The filters were cleaned before use similar to the Oxford protocol (Bronk Ramsey et al. 2004), and a series of freeze-dried archaeological bone gelatin samples and a modern pig-skin gelatin were passed through VS20 and VS15R filters (Vivascience™). We recovered both the eluent (<30-kD fraction) and the liquid that stayed above the filter (>30 kD) in order to obtain a carbon mass and isotope balance. While the >30-kD collagen fraction that is usually selected for AMS analysis does not appear to be significantly contaminated, measurements show significant age differences between the eluent <30 kD and the unfiltered bone collagen, indicating that, despite cleaning, both glycerin and filter still give off contaminants in the eluent. Ultrafiltration with young collagen from pig skin generally confirms these results for the <30-kD fraction but also shows the possibility of small contaminations in the >30-kD fraction. Until a contamination with filter carbon of the >30-kD collagen fraction can be excluded, we would recommend caution in the use of ultrafiltration for cleaning bone collagen with VS20 or VS15R ultrafilters.
Integrating Continuous-Flow Mass Spectrometry and Automatic CO2 Collection for AMS
Authors: Olsen Jesper , Heinemeier Jan , Bahner Klaus , Graney Barry , Phillips Andy
Published: July 2016

Accelerator mass spectrometry (AMS) radiocarbon measurements of organic samples require combustion to obtain CO2 for graphitization. Furthermore, determination of δ13C values is required in order to correct the 14C age due to carbon isotope fractionation effects. δ13C analysis is commonly carried out by stable isotope mass spectrometry because most applications demand high-precision δ13C values in addition to the requirements of 14C dating. A simplifying step is therefore to combine the combustion for stable isotope analysis with cryogenic trapping of CO2 for AMS graphite targets. Presented here is a simple CO2 trapping device based on a modified Gilson 220XL sampling (manifold) robot coupled to the inlet manifold system of a GV Instruments IsoPrime stable isotope mass spectrometer. The system is capable of batch combustion and analysis of up to 40 samples and is under full computer control by the mass spectrometer software. All trapping parameters such as flush time prior to trapping and total trap time are adjustable through the standard software user interface. A low 14C activity of background materials and high precision and accuracy of stable isotope analysis of carbon and nitrogen are demonstrated.
The Effect of N2O, Catalyst, and Means of Water Vapor Removal on the Graphitization of Small CO2Samples
Authors: Smith A M , Petrenko Vasilii V , Hua Quan , Southon John , Brailsford Gordon
Published: July 2016

The effect of nitrous oxide (N2O) upon the graphitization of small (∼40 μg of carbon) CO2samples at the ANSTO and University of California, Irvine, radiocarbon laboratories was investigated. Both laboratories produce graphite samples by reduction of CO2over a heated iron catalyst in the presence of an excess of H2. Although there are significant differences between the methods employed at each laboratory, it was found that N2O has no effect upon the reaction at levels of up to 9.3% by volume of CO2. Further, it was systematically determined that more effective water vapor trapping resulted in faster reaction rates. Using larger amounts of the Fe catalyst generally resulted in higher yields or reaction rates (but not both). The effects of changing the type of Fe catalyst on the final yield and reaction rate were less clear.
Background Components of a Liquid Scintillation Counter in the 14C Window
Authors: Jonsson G , Theodórsson P
Published: July 2016

We present a broad and detailed study of the background components of a liquid scintillation (LS) detector, using a simple laboratory-built system, ICELS. It was specifically designed for radiocarbon dating and is compact and easily transportable (total weight 35 kg). Its flexible LS detector unit has a dome-shaped vial with 3 mL benzene to which 45 mg butyl-PBD is added. The vial sits on the top of a vertical 28-mm-diameter phototube. The gamma radiation, to which the benzene is exposed under varying conditions, was measured by replacing the vial with a 38-mm-diameter Nal crystal. The pulse-height spectra of the 14C LS background and the Nal gamma background were measured in a surface laboratory and in a deep underground counting room with: 1) a lead shield of varying thickness; 2) lead of normal and low 210Pb concentration; 3) phototubes of 2 different types; and 4) varying benzene volume. The beta emission from the face of the tubes was measured with a low-level Geiger counter.
Measurement of Biocarbon in Flue Gases Using 14C
Authors: Hämäläinen K M , Jungner H , Antson O , Räsänen J , Tormonen K , Roine J
Published: July 2016

A preliminary investigation of the biocarbon fraction in carbon dioxide emissions of power plants using both fossil- and biobased fuels is presented. Calculation of the biocarbon fraction is based on radiocarbon content measured in power plant flue gases. Samples were collected directly from the chimneys into plastic sampling bags. The 14C content in CO2 was measured by accelerator mass spectrometry (AMS). Flue gases from power plants that use natural gas, coal, wood chips, bark, plywood residue, sludge from the pulp factory, peat, and recovered fuel were measured. Among the selected plants, there was one that used only fossil fuel and one that used only biofuel; the other investigated plants burned mixtures of fuels. The results show that 14C measurement provides the possibility to determine the ratio of bio and fossil fuel burned in power plants.
A Bayesian Framework for Age Modeling of Radiocarbon-Dated Peat Deposits: Case Studies from the Netherlands
Authors: Blaauw Maarten , Bakker Ronald , Christen J Andres , Hall Valerie A , van der Plicht Johannes
Published: July 2016

Recently, Bayesian statistical software has been developed for age-depth modeling (“wiggle-match dating”) of sequences of densely spaced radiocarbon dates from peat cores. The method is described in non-statistical terms, and is compared with an alternative method of chronological ordering of 14C dates. Case studies include the dating of the start of agriculture in the northeastern part of the Netherlands, and of a possible Hekla-3 tephra layer in the same country. We discuss future enhancements in Bayesian age modeling.
An Information-Efficient Bayesian Model for AMS Data Analysis
Authors: Palonen V , Tikkanen P
Published: July 2016

A Bayesian model for accelerator mass spectrometry (AMS) data analysis is presented. Instrumental drift is modeled with a continuous autoregressive (CAR) process, and measurement uncertainties are taken to be Gaussian. All samples have a parameter describing their true value. The model adapts itself to different instrumental parameters based on the data, and yields the most probable true values for the unknown samples. The model is able to use the information in the measurements more efficiently. First, all measurements tell something about the overall instrument performance and possible drift. The overall machine uncertainty can be used to obtain realistic uncertainties even when the number of measurements per sample is small. Second, even the measurements of the unknown samples can be used to estimate the variations in the standard level, provided that the samples have been measured more than once. Third, the uncertainty of the standard level is known to be smaller nearer a standard. Fourth, even though individual measurements follow a Gaussian distribution, the end result may not.

For simulated data, the new Bayesian method gives more accurate results and more realistic uncertainties than the conventional mean-based (MB) method. In some cases, the latter gives unrealistically small uncertainties. This can be due to the non-Gaussian nature of the final result, which results from combining few samples from a Gaussian distribution without knowing the underlying variance and from the normalization with an uncertain standard level. In addition, in some cases the standard error of the mean does not represent well the true error due to correlations within the measurements resulting from, for example, a changing trend. While the conventional method fails in these cases, the CAR model gives representative uncertainties.
Is it Possible to Find a Good Point Estimate of a Calibrated Radiocarbon Date?
Authors: Michczyński Adam
Published: July 2016

The result from probabilistic calibration of a radiocarbon date is given in the form of a probability density function. Consequently, reporting a 68% or 95% confidence interval has became a commonly accepted practice. However, many users of 14C dates still try to present the results of calibration as a single point. This manner of presentation is often applied during the construction of age-depth models due to its convenience and simplicity. In this paper, the author tests whether it is possible to find a good point estimate of a calibrated 14C date. The idea of the tests is to compare, using computer simulation, the true value of the calendar age with the age calculated based on the probabilistic calibration of the 14C date and the method of finding the point estimate. The test is carried out for the following point estimates: mode, median, average, the central point of the confidence intervals, and the local mode inside the confidence intervals. The results show that none of these may be considered as a good estimate.
Radiocarbon Dating of the Temple of the Monkey—The Next Step Towards a Comprehensive Absolute Chronology of Pachacamac, Peru
Authors: Michczyński Adam , Eeckhout Peter , Pazdur Anna , Pawlyta Jacek
Published: July 2016

The ongoing Ychsma Project aims to shed light on the chronology and function of the late Prehispanic period at the well-known archaeological site of Pachacamac, Peru, through extensive archaeological research. The Temple of the Monkey is a special building that has been cleared, mapped, and excavated within the general framework of the study of “pyramids with ramps,” the most common form of monumental architecture at the site. Through the application of radiocarbon measurements, it can be shown that the temple has been used for around 150 yr and therefore is quite different from other pyramids with ramps previously studied (see Michczyński et al. 2003). Details of the temple, 14C sample selection, and methodology, as well as results, are discussed in this paper. The research has allowed us to make significant advances in the current understanding of pyramids with ramps and the function of the site of Pachacamac as a whole.
Seasonal Variation in Sources of Dissolved Organic Carbon in a Lacustrine Environment Revealed by Paired Isotopic Measurements (Δ14C and δ13C)
Authors: Nara Fumiko , Imai Akio , Yoneda Minoru , Matsushige Kazuo , Komatsu Kazuhiro , Nagai Takashi , Shibata Yasuyuki , Watanabe Takahiro
Published: July 2016

To investigate the sources and cycling of dissolved organic carbon (DOC) in a lacustrine environment, isotopic measurements of 14C and 13C in DOC were carried out for Lake Kasumigaura—which is famous as a very eutrophic and shallow (mean depth 4.0 m) lake in central Japan—and its tributary rivers. Lake and river samples were collected in the spring and autumn (May and September) of 2003. The Δ14C measurements of DOC were performed using the accelerator mass spectrometer at the National Institute for Environmental Studies (NIES-TERRA), Japan. In September, the 14C values of DOC were light (around −200%) and did not differ significantly between lake and river water samples, indicating that DOC in Lake Kasumigaura and its tributary rivers yields older 14C ages than the age expected from the lake-water residence time (average 200 days). This result suggests that terrestrial sources are important contributors to DOC in Lake Kasumigaura. Nevertheless, δ13C values indicated that during spring, DOC in the lake is mainly autochthonous. Thus, sources and cycling of DOC in Lake Kasumigaura may vary seasonally.
Two Decades of Regular Observations of 14CO2 and 13CO2 Content in Atmospheric Carbon Dioxide in Central Europe: Long-Term Changes of Regional Anthropogenic Fossil CO2 Emissions
Authors: Kuc T , Rozanski K , Zimnoch M , Necki J , Chmura L , Jelen D
Published: July 2016

Time series are presented of radiocarbon and 13C contents in atmospheric carbon dioxide over eastern Europe (southern Poland), covering the periods 1983–1994 and 2000–2004. The carbon isotope composition was measured in biweekly composite samples of atmospheric CO2, collected about 20 m above the local ground level. The data for 2 observational sites are presented: i) city of Kraków (50°04′N, 19°55′E; 220 m asl; for 1983–1994 and 2000–2004); and ii) Kasprowy Wierch, Tatra Mountains (49°14′N, 19°56′E; 1989 m asl; for 2000–2004). The latter site is considered a regional reference station, relatively free of anthropogenic influences. During the period 1983–1994, observations in the Kraków area revealed a gradual decrease of 14C content with a broad minimum around 1991 and a small increase by about 10% in the subsequent years. δ13C also changes with time, showing a decreasing trend from approximately −9.6% in 1983, with a slope of −0.02%/yr. The observed trends for both isotopes coincide well with a substantial reduction of coal consumption in Poland and partial replacement of coal by natural gas, especially in urban regions. After 2000, the δ13C slightly increases, reaching a mean value of −10% in 2004, while Δ14C is below the reference level by ∼3.5%. Observations at Kasprowy Wierch (regional reference station) also reflect a diminishing input of fossil carbon into the regional atmosphere. The fossil component in atmospheric CO2, calculated with the aid of 14C data available for the 2 study periods, shows a reduction of anthropogenic input by a factor of 2, which is confirmed by annual statistics of coal consumption.
Holocene Lacustrine Carbonate Formation; Old Ideas in the Light of New Radiocarbon Data from a Single Site in Central Hungary
Authors: Jenei M , Gulyás S , Sümegi P , Molnár M
Published: July 2016

Lacustrine carbonate deposition in Hungary has been traditionally interpreted as the outcome of the dry, hot climate prevailing between 7500 and 5000 14C yr BP (hereafter BP) (∼6400 and 3800 BC), triggering the partial desiccation of minor ponds and lakes. A comparative analysis of 5 14C results from the site of Csólyospálos, central Hungary, with those of other Hungarian lacustrine carbonates yielded stunning new results. According to these new dates, carbonate deposition must have initiated much earlier, possibly around 10,000–11,000 BP (9500–11,000 BC) in the Carpathian Basin. Furthermore, the formation of lacustrine carbonates must have come to an end at very different times in different parts of the basin, contrasting previous views on the uniform and synchronous cessation of lacustrine carbonate formation in Hungary. According to the newest results presented here, carbonate deposition in the southern and southeastern parts of the basin ceased around 6000 BP (∼4900 BC). Meanwhile, in the central parts, deposition continued as long as the terminal Bronze Age (∼1300 BC).
Monitoring of Atmospheric Excess 14C Around Paks Nuclear Power Plant, Hungary
Authors: Molnár M , Bujtás T , Svingor é , Futó I , Světlík I
Published: July 2016

The activity of radiocarbon in 14CO2 and 14CnHm chemical forms is measured in the vicinity of Paks nuclear power plant (NPP), Hungary, by sampling environmental air. Four differential sampling units at different sites collected samples less than 2 km away from the 100-m-high stacks of Paks NPP, and for reference a sampler was operated at a station ∼30 km away from Paks NPP. We present the results of continuous observations at the 5 stations covering the time span from 2000 to 2005. The samples have been analyzed by a proportional counting technique. During a cleaning tank incident at unit 2 of Paks NPP in April 2003, a significant release of radioactive isotopes took place from the damaged fuel assemblies, and gaseous products escaped through the chimney. We evaluate the possible short- and long-term impact of this incident on the 14C content of the atmosphere in the surroundings of Paks NPP. Comparing our 14CO2 measurements with data sets from Jungfraujoch and Schauinsland, as well as from Košetice (Czech Republic), we demonstrate that the incident had no definite influence on the 14C content of the atmosphere.
Spatial Variability of Bomb 14C in an Upland Peat Bog
Authors: Hardie S M L , Garnett M H , Fallick A E , Rowland A P , Ostle N J
Published: July 2016

As part of a study investigating the carbon balance of a blanket bog, we made an assessment of the spatial variation of radiocarbon concentrations in the surface layers of a small area of peatland in the north of England. The peat depth at which bomb-14C content was the highest varied considerably between cores sampled from across the site. At several sampling locations, 14C levels >100% Modern were confined to the surface 8 cm, whereas bomb 14C was evident at 1 site, located only meters away, to a depth of at least 12–16 cm. Using the layer where 14C levels first exceeded 100% Modern as a chronological reference layer, we estimated the carbon accumulation rate over the last 50 yr for the surface peat at each site (range ∼20 to ∼125 g C m2 yr-1). Our results show that although carbon accumulation over the last 50 yr was similar across the site, variation in the depth to which bomb 14C was evident implied considerable variation in the vertical peat growth rate.
Evaluation of Soil14C Data for Estimating Inert Organic Matter in the Rothc Model
Authors: Rethemeyer Janet , Grootes Pieter M , Brodowski Sonja , Ludwig Bernard
Published: July 2016

Changes in soil organic carbon stocks were simulated with the Rothamsted carbon (RothC) model. We evaluated the calculation of a major input variable, the amount of inert organic matter (IOM), using measurable data. Three different approaches for quantifying IOM were applied to soils with mainly recent organic matter and with carbon contribution from fossil fuels: 1) IOM estimation via total soil organic carbon (SOC); 2) through bulk soil radiocarbon and a mass balance; and 3) by quantifying the portion of black carbon via a specific marker. The results were highly variable in the soil containing lignite-derived carbon and ranged from 8% to 52% inert carbon of total SOC, while nearly similar amounts of 5% to 8% were determined in the soil with mainly recent organic matter. We simulated carbon dynamics in both soils using the 3 approaches for quantifying IOM in combination with carbon inputs derived from measured crop yields. In the soil with recent organic matter, all approaches gave a nearly similar good agreement between measured and modeled data, while in the soil with a fossil carbon admixture, only the14C approach was successful in matching the measured data. Although14C was useful for initializing RothC, care should be taken when interpreting SOC dynamics in soils containing carbon from fossil fuels, since these reflect the contribution from both natural and anthropogenic carbon sources.
Chronology of Holocene Climate and Vegetation Changes and their Connection to Cultural Dynamics in Southern Siberia
Authors: Dirksen V G , van Geel B , Koulkova M A , Zaitseva G I , Sementsov A A , Scott E M , Cook G T , van der Plicht J , Lebedeva L M , Bourova N D , Bokovenko N A
Published: July 2016

Two sediment sequences from Big Kyzykul Lake and the Shushenskoe paleolake in the Minusinsk depression, Southern Siberia, were studied by pollen, microfossil, and geochemical analyses, as well as radiocarbon dating. The records indicate the persistence of an arid period between ∼11.7–7.6 cal kyr BP, increased effective moisture since ∼7.6 cal kyr BP, 2 humid impulses at ∼5.1 and 2.8 cal kyr BP separated by a dry interval, and the return to generally drier conditions after ∼1.5 cal kyr BP. This is contrary to the findings noted for the Eurasian temperate zone, but agrees with proxy data reported for arid and semi-arid zones of Central Asia. Reconstructed changes in climate and environment are in good agreement with archaeological data. Almost no evidence of the Mesolithic-Neolithic cultures has been reported for the depression, which is consistent with a dry early and mid-Holocene. Effective moisture started to rise from ∼7.6 cal kyr BP, followed by the beginning of human occupation at ∼6 cal kyr BP. Two maxima of humidity are recorded in the late Holocene, corresponding to the arrival of trees in the depression. No gap was to be found from the Early Bronze to the Iron ages cultures at this time, with the exception of a dry interval at ∼3.6–3.3 cal kyr BP, when the Minusinsk depression was sparsely occupied. The data obtained suggest a close relationship between climate change and cultural dynamics in the steppe zone of Southern Siberia.
Further Radiocarbon Dates from the Catacombs of St. Callixtus in Rome
Authors: Rutgers Leonard V , van der Borg Klaas , de Jong Arie F M , van der Linde Constance , Prins Jelle
Published: July 2016

This paper reports a further chronological assessment of the Christian catacombs of Rome by radiocarbon-dated organic materials in the so-called Liberian region of the catacombs of St. Callixtus on the Appian Way. 14C dates of various types of organic material are discussed and related to ages derived from numismatic evidence and epigraphic remains. The results show that this area of the catacombs of St. Callixtus is older than assumed by previous scholarship. We therefore conclude that the appellation “Liberian region” is a misnomer.
Modeling the Radiocarbon Reservoir Effect in Lacustrine Systems
Authors: Yu Shi-Yong , Shen Ji , Colman Steven M
Published: July 2016

The modern water (both pre- and post-atmospheric nuclear testing) of most lakes has an anomalously old apparent radiocarbon age due to what is commonly referred to as the “reservoir effect.” In contrast to marine settings, this14C-offset phenomenon is primarily caused by pre-aged carbon discharged to lakes by rivers and/or groundwater. In this paper, a 2-component box model based on the principle of14C mass balance in lake water and in the early diagenesis zone was formulated to address the relative importance of terrestrial inputs, autochthonous production, and biogeochemical processes in the14C reservoir of a lacustrine system. The model was tested using observed data from Lake Qinghai, the largest inland water body in China. Our inverse modeling using Markov chain Monte Carlo (MCMC) techniques yields best estimates of the δ14C of DIC in river (∼118% modern) and groundwater (∼76% modern), as well as the δ14C of DOC in river water (∼70% modern) during the post-bomb era. Assuming that these parameters remain constant over time, our modeling indicates that both the DIC and DOC pool of this lake have reservoir ages of about 1500 yr for the pre-bomb era, generally consistent with estimates obtained by extrapolation of the age-depth models of 2 sediment cores to the sediment surface.