Dating of Coptic textiles performed in the early days of the radiocarbon dating method was revisited. In 1957–1958, Louvre curator and art historian P du Bourguet had 4 Coptic textiles 14C dated by the Saclay laboratory. The results were rejected, not because of the large standard deviation (>100 yr), but because their ages did not support his chronological framework based on typological comparison. Furthermore, textiles with comparable ages were dated several centuries apart. As a result of this investigation, for many decades art historians rejected 14C as a dating tool for Coptic textiles. Re-examination of the old data and new 14C analyses revealed that mistakes were made, both in the reporting as in the interpretation of the data and that the textiles are much older than presumed.

This study investigates the accuracy of the radiocarbon-based calculation of the biogenic carbon fraction for different biogas and biofossil gas mixtures. The focus is on the uncertainty in the 14C reference values for 100% biogenic carbon and on the 13C-based isotope fractionation correction of the measured 14C values. The separately (AMS) measured CO2 and CH4 fractions of 8 different biogas samples showed 14C values between 102‰ and 116% (pMC). The δ13C values of these samples varied between –6‰ and +31‰ for the CO2 fraction and between –28‰ and –62‰ for the CH4 fraction. The uncertainty in calculated biogenic carbon fractions due to uncertainty in the 14C reference values depends on the available information about the origin of the used biogenic materials. It varies between ±0.5% and ±3.5% (absolute) depending on the type of biogas. A method is proposed to minimize this uncertainty for different groups of biogases. The calculated biogenic carbon fraction deviates up to ±2.5% for biofossil gas mixtures, if the applied isotope fractionation correction is based on the δ13C value of the mixed biofossil sample instead of the biogenic δ13C value. Combination of both error sources shows that the uncertainty in the calculated biogenic carbon fraction varies between ±0.7% and ±4.5%, depending on the type of biogas in the sample.

The fractionation correction b is used to correct for the fractionation of 14C by using information from 13C in samples. This value is assumed to have a value of 2, where the 14C/12C ratio is double that of the 13C/12C ratio. While natural and laboratory fractionation are usually not considered separately, this article explores the differential fractionation of 14C and 13C during the process of photosynthesis. Values of δ13Cp can be used to calculate Δ13Cp values, which in turn can be used to calculate Δ14Cp, the discrimination against 14CO2 during photosynthesis. Models can then be built of Δ14Cp/Δ13Cp, an approximation for the natural fractionation ratio. This approximation suggests that for C3 plants the ratio is ∼1.90 and for C4 plants the ratio is more variable. While error introduced by the natural fractionation is small, it is also possibly systematic, as b = 2.0 does not seem physiologically possible following these models of carbon fractionation during photosynthesis. The central aim of this study is to illustrate that b derives not from a natural constant, but rather from a variable natural process.

The determination of the age of tropical trees and palms is of significant importance for ecological studies and designing sustainable forest management plans. Radiocarbon is a powerful tool that can potentially help the determination of ages and growth rates of these plants. However, the application of 14C analyses has one important problem for trees without annual rings and palms: the calibration of 14C measurements with common programs such as CALIBomb or OxCal gives erroneous determinations for wood formed between AD 1954 and 1964. This problem is illustrated here using samples from a tropical tree (Otoba gracilipes) and a tropical palm (Oenocarpus bataua). This study shows how the use of two adjacent samples can help to unambiguously determine the real age of the samples and their mean growth rates. For comparison, long-term growth measurements for both species were used and it was determined that 14C analyses provide accurate determination of growth rates for tropical trees and palms. Furthermore, the application of 14C analyses in palms allows the determination of the rosette stage, rarely quantified in forest inventories and life-history studies.

In forensic sciences, radiocarbon found in modern human nails and hair is evaluated to determine the year of death. However, 14C analyses presented herein of fingernails and hair from the same infant demonstrated 14C values of hair that were lower than would be expected (e.g. depleted relative to the fingernails by at least 10‰). These results prompted a series of 14C measurements on infant hair strands, fingernails, and infant shampoo, which suggested the presence of C contamination due to cosmetic products. To further evaluate these discrepancies, several hair strands and fingernail samples from multiple donors were collected, pretreated by several approaches, and measured using isotopic analysis (δ13C, δ15N, and C/N as well as 14C accelerator mass spectrometry). SEM images of the surface of chemically pretreated hair strands were also taken to inspect the performance of the chemical pretreatments applied. Our 14C and stable isotope results show that modern human hair is likely contaminated with fossil-fuel-derived carbon, which is found in most hair care products. Currently, the various chemical pretreatments available in the literature and presented herein show that it is not possible to completely remove foreign carbon contaminates. Thus, the human 14C and δ13C values between keratinous tissues (fingernails and hair) arc not in agreement. From these observations, it becomes apparent that isotopic interpretations using human hair should be used with extreme caution and additional work is needed for its use in forensic and dietary research.

The Laschamp excursion is a period of reduced geomagnetic field intensity occurring 40.7 ± 1.0 kyr ago. As a consequence, cosmogenic isotope production increased dramatically and its sensitivity to solar activity was enhanced during this period. The latter occurs because a larger fraction of the lower-energy interstellar galactic cosmic-ray particles, normally excluded by the geomagnetic field, is able to reach Earth's atmosphere. This produces a cosmogenic isotope production signal with a significant structure. As high-resolution 10Be profiles from both Antarctica (EDC) and Greenland (NGRIP-GRIP) during this crucial period are now available, one can use them as input into a box carbon cycle model in order to predict atmospheric 14C variations due to the Laschamp excursion. For this purpose, 10Be data are converted into 14C, using production calculations for the 10Be-14C conversion, after correction for the estimated difference of sensitivity between polar and global 10Be deposition. Several scenarios of carbon cycle state are simulated, from preindustrial to glacial conditions. Applying two recent cosmogenic isotope production calculations for the 10Be to 14C conversion, we found that the resulting atmospheric Δ14C variations are very sensitive to which of these two are employed. For example, Δ14C amplitude under glacial conditions varies from 260‰ (EDC) and 320‰ (Greenland) to 430‰ (EDC) and 510‰ (Greenland) depending on the formulation used for 10Be-14C conversion.

Radiocarbon dates on samples susceptible to inbuilt age are common in the chronological record of many archaeological and environmental sites. Indeed, fragments of charcoal and wood are sometimes the only materials sufficiently well preserved for dating. However, where high-precision estimates arc required the extra uncertainty associated with such measurements often renders them unusable. This article tests three Bayesian modeling approaches that are designed to tackle this problem. The findings of our study suggest that successful corrections can be made for the inherent age offsets. The most effective and versatile approach was based on a version of outlier analysis. It is hoped that this method will become more widely employed and enable samples susceptible to inbuilt age to be included in high-precision chronologies.

Four fen peat sequences in northern Finland were dated by the accelerator mass spectrometry (AMS) radiocarbon method in order to study past peatland dynamics and carbon accumulation patterns. Initially, plant macrofossils were used for dating. However, the dates were severely disordered, with marked inversions in all sequences. In one 140-cm peat core, for example, all ages fell within a ∼1000-yr time window. Following these unreliable results, a few bulk peat samples were dated to help assess if any of the plant macrofossil-derived dates were reliable. Bulk dates did not help to solve the problem. This study evaluates the possible sources of error but is unable to single out one clear cause. It is probable that many factors related to the fen environment, such as flooding and root intrusion, may have contributed to the errors. Peat plant macrofossils and bulk peat samples are considered to be reliable dating materials, but the examples given herein highlight the difficulties that can be associated with AMS dating of peat samples.

This article focuses on constructing a high-resolution age-depth model for the Puścizna Mała peat bog located in Orawa-Nowy Targ Basin (S Poland). The chronology was established on the basis of both 210Pb and 14C measurements, and further confirmed by pollen diagrams and the peat bulk composition (density, ash content, and measurements of C, N, S). The 137Cs profile revealed significant downward migration of this radionuclide and was not suitable for geochronological interpretation. The peat profile in southern Poland records almost 2000 yr of paleoecological and geochemical changes. Major historical events linked to anthropogenic and climatic changes are recorded in the investigated proxies, which confirm the reliability of the age-depth model. Specifically, the Roman period, Migration period, Medieval times, as well as the Industrial Revolution are reflected in the palynology and bulk composition of the peat. However, dating results obtained for the core segment between 22–45 cm are problematic when confronted with other analyses. The highest peat accumulation rate of 2 mm yr-1 (AD 1300–1400 according to the age-depth model) is not compatible with the section of the highest peat decomposition revealed by lithological description. Moreover, the onset of a drastic decline of forests reflected in the palynological data and dated to AD 1280–1340 (40 cm) is difficult to explain in the light of historical data. Therefore, the lithology, bulk density, and pollen were used to validate the obtained age-depth model. External forcing factors on the peat formation process may be indicated, including agricultural activity, water-level fluctuations, and natural climatic factors, which paradoxically caused doubling of the obtained peat accumulation rate.

Characterized by a dry climate, the arid area of China represents a unique landscape. A proper understanding of the driving mechanisms behind the changes of this ecologically vulnerable landscape requires placing the instrumental records within a geological context. Lakes in this area bear rich information about past climatic and environmental changes presumably regulated by the westerlies at various timescales. The lacustrine records obtained in this area heavily rely on radiocarbon ages, which are usually subject to the temporal and spatial variability of the 14C reservoir effect. Yet, little is known about the 14C reservoir age of lacustrine systems in this area. This study reports an anomalously large 14C reservoir age of about 11,000 ± 2000 yr from a saline lake in NW China by comparing 14C and OSL chronologies. The modeling study suggests that this age offset appears to be an inherent phenomenon in lacustrine systems, which mainly arises from the introduction of pre-aged organic matter from the catchment and the conversion of 14C-depleted dissolved inorganic carbon to organic matter by photosynthesis. Compared to the large age offset induced by the 14C-dcficient exogenous carbon, the reservoir effect due to retention of organic matter in the lake water appears to be inconsequential. The results reveal the pitfall of 14C dating on organic-poor bulk lacustrine sediments in this barren landscape, and thus highlight the need for alternate dating methods to constrain the chronology of lacustrine records.

Radiocarbon accelerator mass spectrometry (AMS) techniques were used to date total organic carbon and plant seeds in the lFs core sequence (36°48′N, 100°08′E) from Qinghai Lake, China. This core was drilled ∼18 m into Qinghai Lake sediments as part of an international cooperative research project, “Scientific Drilling at Qinghai Lake in the Northeastern Tibetan Plateau: High-Resolution Paleoenvironmental Records of Eastern Asia Linked to Global Change,” which began in 2004. Based on the differences in lithology and total organic content (TOC) in core lFs, the core was divided into 3 sections for age-modeling purposes: the upper ∼499 cm lacustrine silty clay to clay; the middle unit of silty clay with silt layers from 499–901 cm; and the lower 901–1861 cm silty clay, loess-like silt, and fine sand layers. Three different approaches are applied to the reservoir age problem. First, a simple linear regression gives an offset of 1342 yr. If the core is divided into three sections, linear regressions can be applied separately for the three segments, which results in an age estimate for the average hardwater effect of ∼135 yr BP for the surface section up to 499 cm. If extrapolated for deeper sections, these results imply a higher reservoir offset for those two sections, which may be as much as 1143 and 2523 yr, but this assumes that there are no discontinuities in the core. A third approach using a wiggle-matching approach gave an offset of 196 yr. This study concludes that the reservoir age of Qinghai Lake is complex, but these new data add to our understanding of the 14C chronology of Qinghai Lake for the last 32 ka.

The chronology of the Neolithic and Bronze Age cultures in Gansu and Qinghai provinces, northwest China, is mainly based on conventional radiocarbon dates from unidentified charcoal, which may be inaccurate in view of the possible “old wood” problem of 14C dating. To discuss the reliability of the chronology of those prehistoric cultures, accelerator mass spectrometry (AMS) dates of short-lived charred seeds were compared to conventional 14C dates of unidentified charcoal from the same flotation samples in 15 Late Neolithic and Bronze Age sites in the area. The results show that 14C dates of unidentified charcoal are obviously older than those of charred seeds in 5 of the 15 flotation samples. This work suggests that the old-wood problem of 14C dating might be related to human subsistence strategies and local vegetation variation during different prehistoric cultural periods in Gansu and Qinghai provinces, which should be discussed before establishing the chronology of Neolithic and Bronze Age cultures in the area.

A review of recently published temporal data from Shuidonggou Locality 1 indicates that a 40–43 cal ka date for the inception of Initial Upper Paleolithic (IUP) blade-oriented technologies in East Asia is warranted. Comparison of the dates from Shuidonggou to other Asian IUP dates in Korea, Siberia, and Mongolia supports this assertion, indicating that the initial appearance of the IUP in East Asia generally corresponds in time to the fluorescence of the IUP in eastern Europe and western Asia. This conclusion preliminarily suggests that either a version of the IUP originated independently in East Asia just prior to 40 cal ka, or more likely, that an early, initial diffusion of the IUP into East Asia occurred ∼41 cal ka, a hypothesis consistent with current estimates for the evolution or arrival of modern humans in the region.

In order to test the accuracy of accelerator mass spectrometry (AMS) radiocarbon dating of pollen, 8 samples of pollen concentrates and 4 bulk organic samples were collected and analyzed from trench T1041 at the Tianluoshan site, Yuyao city, Zhejiang Province. This site was chosen because a reliable chronology had been previously established there based on radiocarbon dates of plant materials. The pollen concentrate samples were measured using AMS 14C and the 4 bulk organic samples were measured by liquid scintillation counting (LSC). The pollen concentrates and bulk organic samples yield ages that are a few hundred years to thousands of years older than those from plant materials, respectively. Contributions from reworked sediments can explain the older ages for the pollen concentrates and sediment organic dates. This study suggests that caution must be exercised when discussing millennial- or centennial-scale climate events based on chronologies that are controlled by age determinations of pollen concentrates.

This article compares radiocarbon dates and the stratigraphic matrix obtained from excavations at the Piedras Blancas archaeological site, Ambato Valley, NW Argentina. Analysis revealed inconsistencies between 14C dates and certain events that can be clearly identified in the stratigraphy of the site. This fact led first to recognize the importance of a detailed stratigraphic record to allow a point of control and comparison. Secondly, this article discusses for the present case, (a) the consistency shown by the dating performed on bone materials in relation to the stratigraphic matrix and (b) the inconsistencies identified in relation to the dating performed on charred plant material, although this type of material was chosen for collection and dating using all appropriate caution to prevent dating bias. Finally, the possibility is considered that the dated plant materials could be affected by the high microcharcoal concentrations observed in the valley's sediments as the result of fire regimes with a high frequency, which seem to have existed since at least about 4000 BP.

In the last decade, the myth of the pristine tropical forest has been seriously challenged. In central Africa, there is a growing body of evidence for past human settlements along the Atlantic forests, but very little information is available about human activities further inland. Therefore, this study aimed at determining the temporal and spatial patterns of human activities in an archaeologically unexplored area of 110,000 km2 located in the northern Congo Basin and currently covered by dense forest. Fieldwork involving archaeology as well as archaeobotany was undertaken in 36 sites located in southeastern Cameroon and in the northern Republic of Congo. Evidence of past human activities through either artifacts or charred botanical remains was observed in all excavated test pits across the study area. The set of 43 radiocarbon dates extending from 15,000 BP to the present time showed a bimodal distribution in the Late Holocene, which was interpreted as two phases of human expansion with an intermediate phase of depopulation. The 2300–1300 BP phase is correlated with the migrations of supposed farming populations from northwestern Cameroon. Between 1300 and 670 BP, less material could be dated. This is in agreement with the population collapse already reported for central Africa. Following this, the 670–20 BP phase corresponds to a new period of human expansion known as the Late Iron Age. These results bring new and extensive evidence of human activities in the northern Congo Basin and support the established chronology for human history in central Africa.

Megiddo (Israel) is a key site for the study of the stratigraphy, chronology, and history of the Bronze and Iron ages in the Levant. The article presents a Bayesian chronological model for seven ceramic typology phases and 10 stratigraphic horizons at this site, covering the Late Bronze and much of the Iron Age. The model is based on 78 samples, which provided 190 determinations—the most thorough set of radiocarbon determinations known so far in a single site in the Levant. This set of data provides a reliable skeleton for the discussion of cultural processes and historical events in the region and beyond, including the periods of the Egyptian Empire in Canaan and the Northern Kingdom of Israel.

This article presents accelerator mass spectrometry (AMS) radiocarbon dates of organic inclusions of cement materials from the House XVII-XVIII Complex located in the Umm el-Jimal archaeological site, east Jordan, aiming at refining the unclear chronology of the house. Fine straws and small fragments of charcoal uncovered from preserved architectural lime mortars and plasters were dated without carrying out extensive excavations. The results indicate that the house most probably was initially plastered or built during the middle of the Byzantine period. The results agree with the historical and archaeological data indicating that Umm el-Jimal flourished during this period; therefore, it is probable that the house was established during this time to meet the housing demand for the increased number of its population.