bluuebunny/crossref_metadata_2025 huggingface dataset:
The Passage of the Bomb Radiocarbon Pulse into the Pacific Ocean
Authors: Jenkins William J , Elder Kathryn L , McNichol Ann P , Reden Karl von
Published: July 2016

We report and compare radiocarbon observations made on 2 meridional oceanographic sections along 150°W in the South Pacific in 1991 and 2005. The distributions reflect the progressive penetration of nuclear weapons-produced 14C into the oceanic thermocline. The changes over the 14 yr between occupations are demonstrably large relative to any possible drift in our analytical standardization. The computed difference field based on the gridded data in the upper 1600 m of the section exhibits a significant decrease over time (approaching 40 to 50‰ in Δ14C) in the upper 200–300 m, consistent with the decadal post-bomb decline in atmospheric 14C levels. A strong positive anomaly (increase with time), centered on the low salinity core of the Antarctic Intermediate Water (AAIW), approaches 50–60‰ in Δ14C, a clear signature of the downstream evolution of the 14C transient in this water mass. We use this observation to estimate the transit time of AAIW from its “source region” in the southeast South Pacific and to compute the effective reservoir age of this water mass. The 2 sections show small but significant changes in the abyssal 14C distributions. Between 1991 and 2005, Δ14C has increased by 9‰ below 2000 m north of 55°S. This change is accompanied overall by a modest increase in salinity and dissolved oxygen, as well as a slight decrease in dissolved silica. Such changes are indicative of greater ventilation. Calculation of “phosphate star” also indicates that this may be due to a shift from the Southern Ocean toward North Atlantic Deep Water as the ventilation source of the abyssal South Pacific.
Decadal Changes of Radiocarbon in the Surface Bay of Bengal: Three Decades After Geosecs and One Decade After WOCE
Authors: Dutta Koushik , Prasad G V Ravi , Ray Dinesh K , Raghav Sanjeev
Published: July 2016

Radiocarbon was measured in the surface seawater dissolved inorganic carbon (DIC) of the Bay of Bengal during November 2006. A meridional transect of the Δ14C in DIC was obtained from measurements in closely spaced samples collected roughly along 88°E. The Δ14C of these samples ranged from 44‰ to 57.7‰ (mean 51.8 ± 1.1‰, n = 12), and 38‰ at one station in the northern Bay of Bengal. The overall pattern of 14C distribution in DIC of surface Bay of Bengal during 2006 was roughly similar to that during the WOCE expedition of 1995. These results indicate a Δ14C decline rate of ∼4‰ per decade since WOCE in the surface Bay of Bengal, which is much smaller compared to a decline rate of ∼25‰ per decade observed in the 2 decades between the GEOSECS and WOCE expeditions, due to the smaller atmosphere-ocean Δ14C gradient.
Pre-Bomb Marine Reservoir Ages in the Western Pacific
Authors: Yoshida Kunio , Hara Tatsuaki , Kunikita Dai , Miyazaki Yumiko , Sasaki Takenori , Yoneda Minoru , Matsuzaki Hiroyuki
Published: July 2016

In this study, molluscan shells housed at the University Museum, the University of Tokyo, provided a new set of region-specific correction values (ΔR) for the western Pacific, in particular for the central part of the main islands in the Japanese Archipelago and the southwest islands of Japan. The values of 40 total samples were calculated from 11 regions. North of the main islands and in the Ryukyu Islands, the mean ΔR values showed comparatively small values, 5–40 14C yr; in the central part of the main islands, these values were 60–90 14C yr.
An Alternate Method of Diluting Dissolved Organic Carbon Seawater Samples for 14C Analysis
Authors: Griffin Sheila , Beaupré Steven R , Druffel Ellen R M
Published: July 2016

We present a time-saving modification to the ultraviolet (UV) oxidation method for analyzing dissolved organic carbon (DOC) concentration, Δ14C, and δ13C measurements in seawater and standard materials. A low background (∼0.2 ± 0.2 μM) was reported for pre-irradiated Milli-Q (MQ) water that was used to dilute samples for DOC 14C analysis (Beaupré et al. 2007). We use MQ water without pre-irradiation (background ∼0.9 ± 0.2 μM) to dilute the sample. This method is suitable for small-volume, high-concentration samples (mass of sample DOC overwhelms mass of MQ water DOC). An acceptable precision of Δ14C measurements (5–9‰) is maintained. This revised method reduces the preparation time for diluted DOC Δ14C samples from 2 days to 1 day.
A Simplified In Situ Cosmogenic 14C Extraction System
Authors: Pigati Jeffrey S , Lifton Nathaniel A , Jull A J Timothy , Quade Jay
Published: July 2016

We describe the design, construction, and testing of a new, simplified in situ radiocarbon extraction system at the University of Arizona. Blank levels for the new system are low ((234 ± 11) x 103 atoms (1 σ; n = 7)) and stable. The precision of a given measurement depends on the concentration of 14C, but is typically <5% for concentrations of 100 x 103 atoms g–1 or more. The new system is relatively small and easy to construct, costs significantly less than the original in situ14C extraction system at Arizona, and lends itself to future automation.
Update on the Performance of the SUERC In Situ Cosmogenic 14C Extraction Line
Authors: Fülöp R H , Naysmith P , Cook G T , Fabel D , Xu S , Bishop P
Published: July 2016

In this paper, we describe improvements to the in situ cosmogenic radiocarbon extraction system at SUERC made since 2004, highlighting the factors that potentially control the reduction of analytical variability. We also present new results on system blanks and of measurements of in situ14C in shielded quartz and a surface quartz sample used at the University of Arizona as an in situ14C standard (PP-4). The SUERC in situ14C extraction system was built in 2001 and is based on a combustion technique following the design of the extraction system at the University of Arizona. Our preliminary results suggest that the continuous running of the extraction system and the monitoring of gas collecting time and of the temperature of the cryogenic traps used in the gas cleaning steps are key to maintaining low and stable system blanks. Our latest average system blank is 2.02 ± 0.23 x 10514C atoms. This is consistent with those recently published by the University of Arizona and ETH in situ14C labs. Measurements of in situ14C concentrations in sample PP-4 yield an average of 3.82 ± 0.23 x 105 atoms g–1 quartz, again consistent with published values.
A Comparison of Cellulose Extraction and ABA Pretreatment Methods for AMS14C Dating of Ancient Wood
Authors: Southon J R , Magana A L
Published: July 2016

We have compared accelerator mass spectrometry (AMS) radiocarbon results on wood samples at or near the limit of14C dating, pretreated with a standard acid-base-acid (ABA) protocol, with those obtained from cellulose prepared from the same samples by several modifications of the Jayme-Wise cellulose extraction method (Green 1963). These tests were carried out to determine the most efficient way to ensure low backgrounds in14C measurements of well-preserved ancient wood samples.
Turnover Rate of Soil Organic Matter and Origin of Soil 14Co2 in Deep Soil from a Subtropical Forest in Dinghushan Biosphere Reserve, South China
Authors: Ding P , Shen C D , Wang N , Yi W X , Ding X F , Fu D P , Liu K X , Zhou L P
Published: July 2016

This paper examines the carbon isotopes (13C, 14C) of soil organic carbon (SOC) and soil CO2 from an evergreen broadleaf forest in southern China during the rainy season. The distribution of SOC δ13C, and SOC content with depth, exhibits a regular decomposition of SOC compartments with different turnover rates. Labile carbon is the main component in the topsoil (0–12 cm) and has a turnover rate between 0.1 and 0.01 yr–1. In the middle section (12–35 cm), SOC was mainly comprised of mediate carbon with turnover rates ranging between 0.01 and 0.025. Below 35 cm depth (underlayer section), the SOC turnover rate is slower than 0.001 yr–1, indicating that passive carbon is the main component of SOC in this section. The total production of humus-derived CO2 is 123.84 g C m–2 yr–1, from which 88% originated in the topsoil. The middle and underlayer sections contribute only 10% and 2% to the total humus-derived CO2 production, respectively. Soil CO2 δ13C varies from –24.7‰ to –24.0‰, showing a slight isotopic depth gradient. Similar to soil CO2 δ13C, Δ14C values, which range from 100.0‰ to 107.2‰, are obviously higher than that of atmospheric CO2 (60–70‰) and SOC in the middle and underlayer section, suggesting that soil CO2 in the profile most likely originates mainly from SOC decomposition in the topsoil. A model of soil CO2 Δ14C indicates that the humus-derived CO2 from the topsoil contributes about 65–78% to soil CO2 in each soil gas sampling layer. In addition, the humus-derived CO2 contributes ∼81% on average to total soil CO2 in the profile, in good agreement with the field observation. The distribution and origin of soil 14CO2 imply that soil CO2 will be an important source of atmospheric 14CO2 well into the future.
A New 14C Data Set of the PY608W-PC Sediment Core from Lake Pumoyum Co (Southeastern Tibetan Plateau) Over the Last 19 kyr
Authors: Watanabe Takahiro , Matsunaka Tetsuya , Nakamura Toshio , Nishimura Mitsugu , Izutsu Yasuhiro , Minami Motoyasu , Nara Fumiko Watanabe , Kakegawa Takeshi , Zhu Liping
Published: July 2016

A new continuous sediment core (PY608W-PC; 3.8 m length) for reconstruction of climatic and environmental changes in the southeastern Tibetan Plateau was taken from the eastern part of Lake Pumoyum Co in August 2006. Sediment layers of the lower part of PY608W-PC (380–300 cm depth) were composed mainly of relatively large plant residues (up to ∼3 cm in length) with an admixture of fine sand and sandy silt. The large plant residues disappeared at ∼300–290 cm depth in core PY608W-PC and were replaced by silt-silty clay. The large plant residues from the lower part of PY608W-PC could be aquatic, because the plant residues were extremely enriched in 13C (up to –3.0‰, −5.6 ± 2.3‰ on average). On the other hand, the plant residue concentrates (PRC fractions) from the upper part of the core (290–0 cm in depth) could be terrestrial C3 plants (δ13C = –21.8 ± 1.7‰ on average). Radiocarbon dating was performed on the large plant residues and PRC fractions from the PY608W-PC sediment core, which represented the chronology from ∼19,000 cal BP to present.
Historic Lime-Mortar 14C Dating of Santa María La Real (Zarautz, Northern Spain): Extraction of Suitable Grain Size for Reliable 14C Dating
Authors: Ortega Luis Angel , Zuluaga Maria Cruz , Alonso-Olazabal Ainhoa , Murelaga Xabier , Insausti Maite , Ibañez-Etxeberria Alex
Published: July 2016

This paper describes a method for effective separation of the pure binder fraction of lime mortars for reliable radiocarbon dating. The methodology allows removal of the detrital carbonate fraction and the unburnt limestone particles, obtaining particles of under 1 μm. The extracted fraction ensured that all carbonate has been generated by slaked lime carbonation. Consequently, the measured carbon corresponds to atmospheric carbon. The proposed method allows to obtain pure datable binder, simplifying considerably the performance of radiometric measurements because dating other grain-size fraction is unnecessary. In order to prove the effectiveness of binder refining, the extraction method has been applied to 5 lime mortars of different archaeological periods from the perimeter walls of Santa María la Real parish church (Zarautz, northern Spain).
Re-Examining Anomalous Early Dates of Settlement in Leeward Hawai'i Island
Authors: Carson Mike T
Published: July 2016

Anomalous dates prior to 1000 yr BP have been reported for near-surface site deposits at Puapua'a in the dry and rocky zone of leeward (west) Hawai'i Island, compared to archipelago-wide earliest cultural layers generally in buried contexts 1000–800 yr BP. Redating and closer examination cannot validate these early dates in cultural association. In the thin sedimentary deposits, preserved cultural materials mostly postdate 600–400 yr BP, but some older materials were incorporated into the layer matrix. The results suggest a much shorter extant chronology of human settlement of this particular zone, whereas earliest sites most likely are preserved in different settings of the Hawaiian Islands.
Reconceiving the Chronology of Inca Imperial Expansion
Authors: Ogburn Dennis E
Published: July 2016

The basic chronology of Inca imperial expansion in Andean South America derives from historical accounts from the Spanish Colonial era, but several issues with this traditional chronology have arisen in recent decades. Advances in radiocarbon dating and calibration now give us some ability to refine or rebuild the chronology, and guidelines for obtaining the most useful dates are discussed. Dates recently obtained from the site of Chamical in the southern highlands of Ecuador are evaluated according to those guidelines, and they suggest Inca expansion to the north began 1 to 2 decades earlier than allowed in the traditional chronology. The chronology of Inca expansion presented in the Spanish chronicles is called into question by these and other dates, and by a reconsideration of the nature of sources of Inca history utilized by Spanish writers. Evidence suggests a primary Inca form of recording provincial conquests resulted in lists that were ordered geographically. However, those records were interpreted by colonial writers as being chronologically ordered, which led to written histories of Inca expansion that are not consistent with the actual historical sequence of events. As a result, the preferred approach to building a chronology of Inca expansion should be based on14C dates, with historical sources used to supplement rather than structure the timeline.
Chronology of Late Pleistocene Humans in Eurasia: Results and Perspectives
Authors: Keates Susan G , Kuzmin Yaroslav V , Burr George S
Published: July 2016

A compilation of direct age determinations for Late Pleistocene human fossils in eastern Europe and Asia is presented in this paper, and current problems with the dating of hominids in these regions are discussed. Only 25 human finds (4 Neanderthals and 21 modern humans) have been directly dated from Pleistocene eastern Europe and Asia. Indirect dating of human remains (using presumably associated organics) often is insecure, especially when information about the exact provenance of human fossils is lacking. Continuation of direct dating of Late Pleistocene humans in Eurasia, primarily with the help of the accelerator mass spectrometry (AMS)14C method, is therefore an urgent task.
Desert Habitation History by14C Dating of Soil Layers in Rural Building Structures (Negev, Israel): Preliminary Results from Horvat Haluqim
Authors: Bruins Hendrik J , van der Plicht Johannes , Haiman Mordechai
Published: July 2016

Traditional archaeological approaches in the central Negev Desert used to employ excavation techniques in post-prehistoric periods in which stratigraphy is based on architecture, while material culture forms the basis for dating assessment and chronology. Such an approach was understandable, as it focused on the most visible remains of past human habitation. However, the detailed habitation record is in the soil rather than in the walls. Moreover, ceramics and stone tools in desert cultures often have limited time resolution in terms of absolute chronology. The rural desert site of Horvat Haluqim in the central Negev yielded 2 habitation periods with the traditional methodology: (1) Roman period, 2nd–3rd centuries CE; (2) Iron Age IIA, 10th century BCE. We have conducted at Horvat Haluqim initial excavations in small building remains that were never excavated before. Our excavation methodology focuses on detailed examination of the archaeological soil in building structures, coupled with accelerator mass spectrometry (AMS) radiocarbon dating for chronology, and micromorphology of undisturbed soil samples to study stratigraphy and soil contents at the microscopic scale. Here, we report preliminary results, concentrating on the14C dates. These suggest a much longer habitation history at the site during the Iron Age. The14C dates obtained so far from these building remains cover Iron Age I, II, III, and the Persian period. The oldest calibrated date (charred C4plants) in a rectangular building structure (L100) is 1129–971 BCE (60.5%, highest relative probability). The youngest calibrated date in a round building structure (L700) is 540–411 BCE (57.9%, highest relative probability). This excavation methodology provides additional “eyes” to look at past human habitation in the Negev Desert, seeing more periods and more detail than was possible with traditional schemes and ceramic dating.
Keeping the Sea Out: Early Medieval Structures at ca' Foscari University, Venice, Italy
Authors: Meadows John , Martinelli Nicoletta , Pignatelli Olivia , Cester Rossella , Fozzati Luigi , Kromer Bernd
Published: July 2016

In 2004, the courtyard of Ca' Foscari University, Venice, was excavated in advance of building work, revealing an unbroken sequence of archaeological deposits. The earliest layers consisted of redeposited natural sediment, packed into wattle structures, a system of land reclamation first described by Cassiodorus in AD 537–8, and now known from several other sites in the city. The ground level was built up and extended several times with successive wattle structures, before the eventual construction of a stone waterfront. We have used Bayesian modeling of dendrochronological, radiocarbon, and stratigraphic dating evidence to obtain a precise chronology for the earliest phases of occupation, and to compare it to the chronology of land reclamation at similar sites elsewhere in Venice.
14C Dating of the Early Natufian at El-Wad Terrace, Mount Carmel, Israel: Methodology and Materials Characterization
Authors: Eckmeier Eileen , Yeshurun Reuven , Weinstein-Evron Mina , Mintz Eugenia , Boaretto Elisabetta
Published: July 2016

The Natufian (15–11.5 kyr BP) sites in the southern Levant are characterized by a lack of macrobotanical remains, including charcoal, and poor preservation of bone collagen. As a result, only about 30 reliable radiocarbon dates are available for building a chronology of the Natufian period. Here, we present new 14C data from the Natufian site of el-Wad terrace that fall in the range of the Early Natufian period. Using Fourier transform infrared (FTIR) analysis, we investigated the environmental factors that influenced the preservation of material for 14C dating of the site, and we tested a modified pretreatment method for poorly preserved charcoal samples. The normal pretreatment protocol for 14C samples (W-ABA) removed more charcoal material than the modified method, which omits the first acid treatment (W-BA). This first acid step seems to enhance the extraction of humic substances during the subsequent base step. We found that the poor preservation of charcoal could be attributed to the presence of calcite, and therefore an alkaline pH of sediments. The most important factor determining bone collagen preservation may have been the hydrological setting, i.e. fluctuating water levels due to oversaturation of the dense sediments after rainfall.
Comparative Decalcification Methods, Radiocarbon Dates, and Stable Isotopes of the VIRI Bones
Authors: Tuross Noreen
Published: July 2016

The Fifth International Radiocarbon Comparison (VIRI) provided a suite of 5 bone samples with consensus ages ranging from 969 to 39,30514C yr BP (Scott et al. 2010). These bones were used herein in a comparison of decalcification methods using either HCl or EDTA to produce collagen, and the results demonstrate age concordance between both preparation methods and the VIRI consensus values. Additional isotopic analyses of the collagen (δ13C, δ15N, and δ18O) illustrate the increasing sensitivity of carbon, nitrogen, and oxygen isotopes in assessing gelatin degradation.
Assessment of Infinite-Age Bones from the Upper Thames Valley, UK, as 14C Background Standards
Authors: Cook G T , Higham T F G , Naysmith P , Brock F , Freeman S P H T , Bayliss A
Published: July 2016

It is becoming increasingly clear that in order to generate accurate radiocarbon dates for bone collagen samples it is important to determine a sample-specific background correction to account for the greater complexity and higher number of steps in the pretreatment chemistry of this material. To provide suitable samples for the14C community, 7 bone samples were obtained from contexts within British gravel quarries, which according to other dating techniques or stratigraphic information, should be of infinite age with respect to14C. The bones were analyzed at the Oxford Radiocarbon Accelerator Unit (ORAU) and the Scottish Universities Environmental Research Centre (SUERC) to determine their suitability. In this paper, we show that 6 of the samples were indistinguishable from background. Both institutions measured finite ages for sample 387 from Oxey Mead that were statistically indistinguishable. Further work is required to establish whether this is because the bone was intrusive and of a younger age than expected or whether it is contaminated either postdepositionally or in the laboratory. We favor the former explanation because (1) the 2 chemistry laboratories use very different pretreatment schemes, (2) collagen yields were high, and (3) the laboratories produced ages that are in good agreement. The 6 “greater than” age samples will be made available to14C laboratories to be used as background standards.
14C Dating of Fire-Damaged Mortars from Medieval Finland
Authors: Lindroos Alf , Regev Lior , Oinonen Markku , Ringbom Åsa , Heinemeier Jan
Published: July 2016

This study focuses on radiocarbon dating of mortars that have withstood city fires and display visible fire damage effects. Some fire-damaged and undamaged original Medieval mortars from the same site have also been tested. The mortars were heated at different temperatures and then analyzed using the same preparation procedures as in 14C dating of mortars to see what kind of changes the heating would introduce to the mineralogy, chemistry, and the carbon and oxygen isotope ratios. We found that decarbonation during heating starts at ∼600 ° and recarbonation starts as soon as the temperature drops. Already after a few days, most of the lost CO2 has been replaced with atmospheric CO2. The renewed carbonates are readily soluble in the acid hydrolysis process and their carbon and oxygen isotopes have a light signature. Fire-damaged historical mortars display the same features. If a long time has elapsed between hardening of the original mortar and the fire, the new carbonates have 14C concentrations that point to the fire event rather than to the building event. In several cases, the fire-damaged mortars have an easily soluble carbonate fraction with a 14C age that could be related to a major fire event, but still most of the soluble carbonate yields a 14C age that seems like a reasonable age for the original construction.
Least-Squares Fitting A Smooth Curve to Radiocarbon Calibration Data
Authors: Knox F. B. , McFadgen B. G.
Published: July 2016

We Fourier transformed and filtered calibration curve data to compensate for the averaging effect of radiocarbon-dating sets of adjacent tree rings. A Wiener Filter was also applied to minimize the effects of the counting errors of the dates on the resulting calibration curve and to produce a least-squares curve through the data. The method is illustrated using a short 14C-dated tree-ring sequence from New Zealand to produce a calibration curve at yearly intervals for New Zealand matai (Prumnopitys taxifolia). The resulting curve has a nominal standard error of 10 ± 3 yr, which is ca. half the average standard error of the original raw data.
New Bomb Pulse Radiocarbon Records from Annual Tree Rings in the Northern Hemisphere Temperate Region
Authors: Quarta G , D'Elia M , Valzano D , Calcagnile L
Published: July 2016

The “bomb” radiocarbon spike induced by atmospheric nuclear detonations has been reconstructed at a latitude of 40°N by measuring the 14C content in annual rings of a living pine (Pinus pinea) at the Accelerator Mass Spectrometry facility of the University of Lecce. We report how the samples were taken, selected, prepared for analysis, and measured. The results are in good agreement with other data sets available for the Northern Hemisphere temperate regions, showing that a curve for the calibration of 14C dates, valid for the whole Northern Hemisphere, can be established for the second half of the 20th century.
Reconstruction of the 14C Production Rate from Measured Relative Abundance
Authors: Usoskin Ilya G , Kromer Bernd
Published: July 2016

A new method is presented for the reconstruction of the radiocarbon production rate from the measured relative abundance of Δ14C. The method treats the carbon cycle as a linear Fourier filter and thus allows for the correct and unambiguous inversion of the carbon cycle. The 14C production rate, as reconstructed by the Fourier filter method, agrees with the results obtained by the traditional iteration method. Since the 2 methods use completely different approaches, this verifies the validity of the reconstruction. The composite series is presented, based on both methods and their systematic uncertainties.
The Impact of Radiocarbon Dating on Old World Archaeology: Past Achievements and Future Expectations
Authors: Bar-Yosef O
Published: July 2016

Half a century since radiocarbon was first used in the archaeology of the Old World, it seems that the expectations of W F Libby may be becoming a reality. In 1952 (Libby 1952:97), he wrote:

Archaeologists, geologists and palynologists are continually searching for the means to improve methods of counting time. The … relative chronologies lack precision and direct correlation with the calendar, except when they may be checked with, … for example, the calendar based on tree-ring counts.
Radiocarbon Dating the Last Glacial-Interglacial Transition (Ca. 14–914C Ka Bp) in Terrestrial and Marine Records: The Need for New Quality Assurance Protocols
Authors: Lowe J John , Walker Michael J C
Published: July 2016

The publication during the 1990s of Greenland ice-core records spanning the transition from the Last Cold Stage to the present interglacial (ca. 14–914C ka BP) presented new challenges to scientists working on marine and terrestrial sequences from this important time interval. In particular, there is now an overriding imperative to increase the levels of precision by which events during this period can be dated and correlated. We review some of the problems commonly encountered when using radiocarbon dating for these purposes, and consider some of the new approaches that will be required if this dating method is to provide a basis for a high precision chronology for the last glacial-interglacial transition.
Radiocarbon – A Unique Tracer of Global Carbon Cycle Dynamics
Authors: Levin Ingeborg , Hesshaimer Vago
Published: July 2016

Climate on Earth strongly depends on the radiative balance of its atmosphere, and thus, on the abundance of the radiatively active greenhouse gases. Largely due to human activities since the Industrial Revolution, the atmospheric burden of many greenhouse gases has increased dramatically. Direct measurements during the last decades and analysis of ancient air trapped in ice from polar regions allow the quantification of the change in these trace gas concentrations in the atmosphere. From a presumably “undisturbed” preindustrial situation several hundred years ago until today, the CO2 mixing ratio increased by almost 30% (Figure 1a) (Neftel et al. 1985; Conway et al. 1994; Etheridge et al. 1996). In the last decades this increase has been nearly exponential, leading to a global mean CO2 mixing ratio of almost 370 ppm at the turn of the millennium (Keeling and Whorf 1999).
Some Comments on Accelerator Mass Spectrometry
Authors: Gove Harry E
Published: July 2016

This paper discusses some aspects of the development of accelerator mass spectrometry (AMS), the international conferences that have been held, and the books that have been written on the subject. It also mentions some details of the technique and its strengths. Some of the interesting measurements that have been made recently are covered, and finally, it presents some thoughts on future developments.
What Future for Radiocarbon?
Authors: Scott E M , Harkness D D
Published: July 2016

In this short article, we summarize some milestones in the 50-yr-long development of natural 14C measurement. In the light of this appraisal we presume to hazard some personal opinions and forecasts as to where best opportunities might lie for future gains from the continued investment in applied 14C science. The technique and the journal are one and the same in this regard.
Radiocarbon Releases At the Krško Nuclear Power Plant
Authors: Vokal Barbara , Kobal Ivan
Published: July 2016

Since 1991, radiocarbon analyses of exhaust air have been part of the regular radioactivity monitoring program at the Krško Nuclear Power Plant (NPP), a Westinghouse 632 MWe pressurized water reactor (PWR). Activity of CO2 and hydrocarbons has been identified; the former contributes ca. 43%. A normalized release of total 14C of 0.219 TBqGWe−1a−1 was obtained. Indoor air 14C concentrations in selected rooms inside the plant have generally been <5 Bq m−3, although rare peaks of >1000 Bq m−3 may be reached. Tree rings have shown slight enhanced 14C activity due to the operation of the plant.
Comparison of Radiocarbon Ages from Different Organic Fractions in Tropical Peat Cores: Insights from Kalimantan, Indonesia
Authors: Wüst Raphael A J , Jacobsen Geraldine E , von der Gaast Haitse , Smith Andrew M
Published: July 2016

Various organic fractions of an Indonesian tropical peat deposit were dated using radiocarbon accelerator mass spectrometry (AMS). Four different depth layers, deposited during the last 28,000 14C yr, were analyzed and the data compared to bulk sample analyses. The pollen extracts consistently produced the oldest dates. The bulk samples (<250 μm and <100 μm) often yielded the youngest dates. The age difference between the individual fractions depended on the layer depth and hence the true age of the sampled peats. The age discrepancy was highest (∼16,000 14C yr) in the oldest peat material. We interpret this to be a consequence of the input of organic matter over a long period of time, with peat oxidation and/or no peat accumulation during the last glacial maximum (LGM). The age discrepancies were smaller (between 10 and 900 14C yr) for the Holocene peat samples. It was concluded that the pollen extract fraction might be the most reliable fraction for dating tropical peat deposits that are covered by deeply rooting vegetation.
New Marine ΔR Values for the South Pacific Subtropical Gyre Region
Authors: Petchey Fiona , Anderson Atholl , Zondervan Albert , Ulm Sean , Hogg Alan
Published: July 2016

This paper presents 31 new ΔR results of known-age, pre-AD 1950 shells from the South Pacific subtropical gyre region, spanning from the Tuamotu Archipelago in the east to New Caledonia in the west. This doubles the number of available ΔR values for the Oceania region. These values indicate that the regional offset (ΔR) from the modeled radiocarbon marine age has remained relatively constant over the last 100 yr prior to 1950. Variation from the norm can be attributed to various influences including localized upwelling around islands, the presence of a hardwater effect, direct ingestion of old carbon by the live shellfish, or enhanced exchange with atmospheric CO2 as a consequence of photosynthetic activity or increased aeration.
Very Long-Lived Mollusks Confirm 17th Century AD Tephra-Based Radiocarbon Reservoir Ages for North Icelandic Shelf Waters
Authors: Wanamaker Alan D , Heinemeier Jan , Scourse James D , Richardson Christopher A , Butler Paul G , Eiríksson Jón , Knudsen Karen Luise
Published: July 2016

Marine sediment records from the north Icelandic shelf, which rely on tephrochronological age models, reveal an average ΔR (regional deviation from the modeled global surface ocean reservoir age) of approximately 150 yr for the last millennium. These tephra-based age models have not hitherto been independently verified. Here, we provide data that corroborate ΔR values derived from these sediment archives. We sampled the youngest portion (ontogenetic age) of a bivalve shell, Arctica islandica (L.), for radiocarbon analysis, which was collected alive in 2006 from the north Icelandic shelf in ∼80 m water depth. Annual band counting from the sectioned shell revealed that this clam lived for more than 405 yr, making it the longest-lived mollusk and possibly the oldest non-colonial animal yet documented. The 14C age derived from the umbo region of the shell is 951 ± 27 yr BR Assuming that the bivalve settled onto the seabed at AD 1600, the corresponding local value of ΔR is found to be 237 ± 35 yr by comparison of the 14C age with the Marine04 calibration curve (Hughen et al. 2004) at this time. Furthermore, we cross-matched a 287-yr-old, dead-collected, A. islandica shell from AD 1601 to 1656 from the same site with the live-caught individual. 14C analysis from the ventral margin of this shell revealed a ΔR of 186 ± 50 yr at AD 1650. These values compare favorably with each other and with the tephra-based ΔR values during this period, illustrating that 14C from A. islandica can effectively record 14C reservoir changes in the shelf seas.
Systematic Bias of Radiocarbon Method
Authors: Walanus Adam
Published: July 2016

Systematic bias of dates can became statistically significant regarding the growing global number of dates connected with the calibration curve plateau. For example, samples of true age in the span 800–700 BC are dated to be roughly 100 younger, on average. The curve of expected bias for a given age is presented. To avoid such a bias, the Bayesian paradigm probably must be modified in some way.
Absolute Radiocarbon Chronology in the Formative Pottery Production Center of Santa Lucía, Cochabamba, Bolivia
Authors: Gabelmann Olga U , Michczyński Adam , Pazdur Anna , Pawlyta Jacek
Published: July 2016

Santa Lucía is a pottery production site dating to the Formative period (about 1600 BC to AD 200). It is located in the Cochabamba valleys of the eastern Bolivian Andes. The settlement consists of a residential area and a separate workshop area. A peripheral sector of ash mounds was used as refuse sites and burial grounds. The excavations yielded a total of 16 radiocarbon samples from all 3 sectors, which were dated at the Gliwice Radiocarbon Laboratory (Gliwice, Poland). The results from the deepest trench in the workshop sector (Trench 5) provide information for the stratigraphic sequence and help to define spatial and socioeconomic changes at around 600–500 BC with the beginning of the Late Formative or Santa Lucía III phase. The 14C dates from Santa Lucía, therefore, contribute to a better definition of the existing regional Formative period phases and finally to a better understanding of the processes during the Formative period in the south-central Andes.
Temporal Change of Radiocarbon Reservoir Effect in Sugan Lake, Northwest China during the Late Holocene
Authors: Zhou Ai-feng , Chen Fa-hu , Wang Zong-li , Yang Mei-lin , Qiang Ming-rui , Zhang Jia-wu
Published: July 2016

Many lacustrine chronology records suffer from radiocarbon reservoir effects. A continuous, accurate varve chronology, in conjunction with accelerator mass spectrometry (AMS)14C dating, was used to determine the age of lacustrine sediment and to quantify the past14C reservoir effect in Sugan Lake (China). Reservoir age varied from 4340 to 2590 yr due to14C-depleted water in the late Holocene. However, during the Little Ice Age (LIA),14C reservoir age was relatively stable. According to this study,14C reservoir age in the late Holocene may be driven by hydrological and climatic changes of this period. Therefore, special caution should be paid to the correction of the14C reservoir effect by a unique14C reservoir age in paleoclimatic and paleolimnological study of northwest China.
Can We Get a Good Radiocarbon Age from “Bad Bone”? Determining the Reliability of Radiocarbon Age from Bioapatite
Authors: Cherkinsky Alexander
Published: July 2016

The study of the radiocarbon age of bone bioapatite was initiated by necessity to date archaeological artifacts, which often contain little or no collagen as a result of poor preservation. Contamination of the organic fraction in the process of the burial or during museum preservation treatment generally prohibits the use of the collagen fraction for dating. Our investigation has shown that the pretreatment of bone with diluted acetic acid following a proscribed technique allows the separation of the bioapatite fraction from diagenetic carbonates. We have successfully used this technique to prepare and date samples of bone and of tooth enamel and dentin, with varying degrees of preservation condition, and from time intervals ranging from a few hundred 14C yr to greater than 40,000 14C yr.
Radiocarbon Dates and the Earliest Colonization of East Polynesia: More than a Case Study
Authors: Della Casa Philippe
Published: July 2016

Over the last 30 yr, there has been an ongoing debate on the dates and modes of the earliest colonization of East Polynesia, namely the Cook Islands, the 5 archipelagos of French Polynesia, the Hawai'i Islands, Easter Island, and New Zealand. At least 3 alternative models were proposed by Sinoto, Anderson, Kirch, and Conte, but interestingly all these models basically relied on the same set of roughly 200 radiocarbon dates on various organic materials from archaeological excavations as far back as the 1950s. Some of the models differed by 500–1000 yr—for a proposed initial colonization around the turn of the BC/AD eras, if not considerably later. By comparing the different approaches to this chronological issue, it becomes evident that almost all known problems in dealing with 14C dates from archaeological excavations are involved: stratigraphy and exact location of samples, sample material and quality, inbuilt ages and reservoir effects, lab errors in ancient dates, etc. More recently, research into landscape and vegetation history has produced alternative14C dating for early human impact, adding to the confusion about the initial stages of island colonization, while archaeological14C dates, becoming increasingly “young” as compared to former investigations, now advocate a rapid and late (post-AD 900) colonization of the archipelagos. As it appears, the Polynesian case is more than just another case study, it's a lesson on14C-based archaeological chronology. The present paper does not pretend to solve the problems of early Polynesian colonization, but intends to contribute to the debate on how14C specialists and archaeologists might cooperate in the future.
Contradictions in the Relative Chronology: Archaeological and Radiocarbon Dating
Authors: Stöckli Werner E
Published: July 2016

When comparing dendrodates and radiocarbon dates, I advocate using the mean value for archaeologically defined data series, as in the usual case, the correct dating is always more precise than the calibrated areas. However, in the extreme gradient of the calibration curve, we must consider the errors. Based on the Corded Ware from the Tauber basin, I put forward a first example in which a contradiction between the archaeological and 14C dating occurs. If one cleanly separates the older measurements from Köln and the younger ones from Heidelberg, the contradiction towards the archaeological dating is canceled out when only the younger Heidelberg dates are taken into account. Regarding the Early Bronze Age, I shall first deal with the cemetery at Singen and will show, using the typology and the horizontal distribution of the graves, how outliers can be identified, thus narrowing the range for dating of the cemetery. The comparison of 2 archaeologically contemporaneous cemeteries in the Neckar basin (Rottenburg and Gäufelden) again results in contradictions between the archaeological and 14C dating. In this case, the contradictions cannot be solved without any new dating measurements. It is recommended that these should be carried out by at least 2 laboratories. Finally, some recommendations are given to archaeologists. In my opinion, 14C dates that are archaeologically unsuitable should be used to check the findings and the archaeological-typological classification. The contradictions should be reported immediately to the 14C laboratory, so that any possible experimental errors can be identified.
Chronology and Bell Beaker Common Ware
Authors: Piguet Martine , Besse Marie
Published: July 2016

The Bell Beaker is a culture of the Final Neolithic, which spread across Europe between 2900 and 1800 BC. Since its origin is still widely discussed, we have been focusing our analysis on the transition from the Final Neolithic pre-Bell Beaker to the Bell Beaker. We thus seek to evaluate the importance of Neolithic influence in the establishment of the Bell Beaker by studying the common ware pottery and its chronology. Among the 26 main types of common ware defined by Marie Besse (2003), we selected the most relevant ones in order to determine—on the basis of their absolute dating–their appearance either in the Bell Beaker period or in the pre-Bell Beaker groups.
New Radiocarbon Dates for the Early Neolithic of the Western Mediterranean
Authors: van Willigen Samuel , Hajdas Irka , Bonani Georges
Published: July 2016

Understanding of processes that determined the expansion of farming and animal husbandry in south-western Europe is hampered by poor chronologies of the early Neolithic in this region. This paper presents new radiocarbon dates, which are used to construct such a chronological frame for a regional group of the most important culture of the early Neolithic in the western Mediterranean: the Cardial culture.
Radiocarbon Chronology with Marine Reservoir Correction for the Ritidian Archaeological Site, Northern Guam
Authors: Carson Mike T
Published: July 2016

Archaeological investigations at the Ritidian site in Guam provide a series of radiocarbon dates spanning the potential range of human presence in the region. Paired marine and terrestrial samples offer a basis for ΔR calculation, as well as evaluation of the utility of different types of marine samples for 14C dating of archaeological contexts. The results indicate an early period of temporary fishing camp activity in the context of higher sea level and little or no stable beach, followed by larger-scale residential activity in the context of lower sea level and an extensive stable beach landform.
On-line Radiocarbon Measurements of Small Samples Using Elemental Analyzer and MICADAS Gas Ion Source
Authors: Ruff M , Fahrni S , Gäggeler H W , Hajdas I , Suter M , Synal H-A , Szidat S , Wacker L
Published: July 2016

An on-line measurement system was installed at the MICADAS in Zurich, using an elemental analyzer (EA) as a combustion unit to enable direct radiocarbon measurement of samples containing carbon in the range of 5–100 μg possible with minimum effort. The samples are combusted in small capsules and the gaseous combustion products are separated by the EA. The carbon dioxide leaving the EA in a high helium flow is concentrated on a small external trap containing X13 zeolite adsorber material. This new concept, avoiding a cryogenic trapping for the enrichment step, allows the construction of a very compact system able to work even with the smallest samples. Concentrated on the external trap, the carbon dioxide is flushed into the gas-tight syringe of our gas inlet system using a low helium stream. The gas mixture is measured with the MICADAS gas ion source. Several different sample capsules were analyzed to minimize the major blank contribution coming from the sample vessel. The best results were achieved with 25-μL tin capsules, which contained only 0.34 ± 0.13 μg carbon at 65 pMC. This work describes the development of the on-line system and the protocol for measurement runs. Results are presented for on-line measurements of reference materials and a comparison is performed with typical dating samples measured previously as graphite targets. Finally, relevance and limitations of on-line measurements are discussed.
Examining the Inherent Variability in ΔR: New Methods of Presenting ΔR Values and Implications for MRE Studies
Authors: Russell N , Cook G T , Ascough P L , Scott E M , Dugmore A J
Published: July 2016

Currently, there is significant ongoing research into the temporal and spatial variability of marine radiocarbon reservoir effects (MREs) through quantification of ΔR values. In turn, MRE studies often use large changes in ΔR values as proxies for changes in ocean circulation. ΔR values are published in a variety of formats with variations in how the errors on these values are calculated, making it difficult to identify trends or to compare values, unless the method of calculating the ΔR is explicitly described or all of the data are made available in the publication. This paper demonstrates the large range in ΔR values (+34 to −122) that can be obtained from a single, secure archaeological context when using the multiple paired sample approach, despite the fact that the terrestrial entities were of statistically indistinguishable 14C ages, as were the marine samples. This demonstrates the inherent variability in the ΔR calculations themselves and we propose that, together with calculation of mean ΔR, the distribution of ΔR values should be displayed, e.g. as histograms in order to illustrate the full data range. This spread is only apparent when employing a multiple paired sample approach as the uncertainty derived on a single pair of samples, taking account only of the errors on the individual 14C ages, will never truly represent the overall variability in ΔR that results from the intrinsic variability in the population of 14C ages in samples that might have been used. Consequently, ΔR values and the associated uncertainty calculated from single pairs should be treated with some caution. We propose that, where possible, when using paired archaeological samples, that a multiple paired approach should be employed as it will test the context security of the material used in the ΔR calculations. When summarizing the values by the weighted average, we also propose that the standard error for predicted values should be employed as this will fully encompass the uncertainty of a future ΔR calculation, using different samples for a similar time and location. Finally, we encourage future publishing of ΔR values using the histogram format, making all of the data available. This will help ensure that ΔR values are comparable across the literature and should provide a framework for standardization of publication methods.
Balanced-Energy Counting Window for Stable Liquid Scintillation Radiocarbon Dating
Authors: Theodórsson Pall
Published: July 2016

This paper describes an optimal radiocarbon counting window for liquid scintillation (LS) 14C dating that secures for unquenched as well as for heavily quenched dating samples maximal stability of 14C counting efficiency and theoretically minimal quench correction. In high-precision dating, a balanced counting window with fixed channel limits is frequently used, where about 3% of the highest part of the 14C spectrum is sacrificed for high 14C counting stability. The stability is, however, diminished for quenched samples. Therefore, this window is here replaced by a balanced fixed-energy 14C counting window where the channel limits depend on the quench level. The LS system used must have a linear amplifier and a multichannel analyzer. All samples are measured at a fixed high voltage. For energy calibration and determination of the quench level, the channel number of the middle of the 59.5-keV peak from an external 241Am gamma source is determined before and after measuring each sample. This counting mode is valuable in high-precision dating. It could be widely applied if adapted to systems with a logarithmic amplifier, generally used in LS dating.