RSS 1.0Radiocarbon, Volume 44 (2002)
ABOUT THIS COLLECTION
Radiocarbon is the main international journal of record for research articles and date lists relevant to 14C and other radioisotopes and techniques used in archaeological, geophysical, oceanographic, and related dating.
This archive provides access to Radiocarbon Volumes 1-54 (1959-2012).
As of 2016, Radiocarbon is published by Cambridge University Press. The journal is published quarterly. Radiocarbon also publishes conference proceedings and monographs on topics related to fields of interest. Visit Cambridge Online for new Radiocarbon content and to submit manuscripts.
ISSN: 0033-8222
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Radiocarbon, Volume 44, Number 1 (2002)Department of Geosciences, The University of Arizona, 2002-01-01
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Radiocarbon, Volume 44, Number 3 (2002)Department of Geosciences, The University of Arizona, 2002-01-01
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Radiocarbon, Volume 44, Number 2 (2002)Department of Geosciences, The University of Arizona, 2002-01-01
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Editorial BoardDepartment of Geosciences, The University of Arizona, 2002-01-01
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Editorial BoardDepartment of Geosciences, The University of Arizona, 2002-01-01
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Editorial BoardDepartment of Geosciences, The University of Arizona, 2002-01-01
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Radiocarbon Dating of Deep-Sea CoralsDeep-sea corals are a promising new archive of paleoclimate. Coupled radiocarbon and U-series dates allow 14C to be used as a tracer of ocean circulation rate in the same manner as it is used in the modern ocean. Diagnetic alteration of coral skeletons on the seafloor requires a thorough cleaning of contaminating phases of carbon. In addition, 10% of the coral must be chemically leached prior to dissolution to remove adsorbed modern CO2. A survey of modern samples from the full Delta-14C gradient in the deep ocean demonstrates that the coralline CaCO3 records the radiocarbon value of the dissolved inorganic carbon.
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Pre-Bomb Radiocarbon Variability Inferred from a Kenyan Coral RecordWe report results from AMS radiocarbon measurements (Delta-14C) in corals recovered off the coast of Kenya. Bimonthly samples which span the pre-bomb era average -51 per mil (+/3.7; n=43), when age and Suess effect are corrected, and over the time of interest (1946-1954) do not exhibit any discernible seasonality. Relative to regional pre-bomb Delta-14C values in the western Indian Ocean, our results indicate 14C enrichment off the coast of Kenya. Furthermore, the absence of a distinct subannual Delta-14C signal suggests that open and coastal upwelling is negligible off the coast of Kenya. Unlike pre-bomb values south of the equator near Seychelles and Madagascar, our pre-bomb value are enriched by more than 10 per mil. The enrichment of pre-bomb Kenyan Delta-14C values relative to sites around Mauritius, northern Madagascar and Seychelles, suggest that the influence of depleted Delta-14C water transported in the SEC is limited to regions south of 3 to 4 degrees S.
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Correcting for Contamination in AMS 14C DatingWhen using accelerator mass spectrometry (AMS) for radiocarbon dating, it is important to correct for carbon contamination that is added to the sample and the standard during chemical processing. We derive an equation for making this correction that generalizes previous work in several ways. We treat the case in which contaminating carbon is added during both the combustion step and graphitization step. Taking this two-stage contamination process into account is particularly important when only a fraction of the CO2 produced in the combustion is graphitized. We also allow for the fact that the 13C fractions of the sample, the standard, and the contaminants may be different.
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WOCE Radiocarbon IV: Pacific Ocean Results; P10, P13N, P14C, P18, P19 & S4PThe World Ocean Circulation Experiment, carried out between 1990 and 1997, provided the most comprehensive oceanic study of radiocarbon to date. Approximately 10,000 samples were collected in the Pacific Ocean by U.S. Investigators for both conventional large volume B counting and small volume accelerator mass spectrometry analysis techniques. Results from six cruises are presented. The data quality is as good or better than previous large-scale surveys. The 14C distribution for the entire WOCE Pacific data set is graphically described using mean vertical profiles and sections, and property-property plots.
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Why Early-Historical Radiocarbon Dates Downwind from the Mediterranean are Too EarlySeveral authors have claimed that radiocarbon dates in the Ancient Near East are too early. Herein, a hypothesis that might explain this is presented. Marine degassing of "old" carbon (i.e. 14C-deficient C), induced by upwelling of old subsurface water, has been observed, n modern times, to cause century-scale 14C ages in the surface atmosphere. A review of the Mediterranean Sea post-ice-age circulation concludes that the subsurface waters became very old, primarily due to millennia-long stagnation. It is hypothesized that as the stagnation ended, subsurface waters were brought towards the surface, where they degassed old carbon. Additionally, Anatolian dendrochronology is shown to not contradict the hypothesis.
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The Use of Raman Spectroscopy to Monitor the Removal of Humic Substances from Charcoal: Quality Control for 14C Dating of CharcoalOne of the largest sources of uncertainty in radiocarbon dating stems from the sample pretreatment procedures used to minimize contamination. A major source of carbon contamination in charcoal from archaeological sites is humic substances carried by groundwater. Here we present a method, independent of 14C dating itself, to evaluate the effectiveness of the cleaning procedure of charcoal. Raman spectra of mixtures of humic substances (HS) and laboratory prepared charcoal indicate that Raman spectroscopy can be used as a semi-quantitative measure of the amount of humic substances associated with archaeological charcoal. Raman spectral analysis of archaeological charcoal samples subjected to different cleaning regimes supports this contention. Such measurements can provide quality control for charcoal preparation procedures and may assist in the interpretation of carbon-dating results.
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The Radiocarbon Dating and Authentication of Iron ArtifactsThe continuing improvements in accelerator mass spectrometry (AMS) dating technology mean that it is possible to work on ever smaller samples, which in turn, make an ever wider range of sample potentially available for dating. This paper discusses some of the difficulties arising with the interpretation of AMS dates obtained from carbon in iron. The overriding problem is that the carbon, now in chemical combination with the iron, could have come from a variety of sources with very different origins. These are now potentially an irresolvable mixture in the iron. For iron made over the last millennium, there are the additional problems associated with the use of both fossil fuel and biomass fuel in different stages of the iron making, leading to great confusion, especially with authenticity studies.
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The Antiquity of the Prehistoric Settlement of the Central-South Brazilian CoastWe discus here the prehistoric settlement of the central-south Brazilian coast, and, more specifically, 1 old radiocarbon date obtained for a coastal shellmound, as well as its implications concerning the chronology attributed to the settlement process. The accelerator mass spectrometry (AMS) technique was used to determine the 14C age of charcoal from a shellmound on the southern coast of Rio de Janeiro. The resulting age was 7860 +/80 BP, an unexpected result that reinforces 2 similar previously obtained dates for the same region. Brazilian archaeologists, however, have questioned those 2 dates, because they would predate by some 2000 yr the antiquity consensually accepted for the settlement of the central-south Brazilian littoral.
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The Antiquity of Pearl Shell (Pinctada sp.) Burial Artifacts in Palau, Western MicronesiaPearl shell was an important and highly valued resource for producing tools and ornaments in Oceania. One pearl shell artifact type that is quite rare in Micronesia, however, is the crescent-shaped scraper/grater. These artifacts have recently been found in 2 burial caves in Palau, Western Caroline Islands, suggesting they may have played important social and symbolic roles in society. The first direct accelerator mass spectrometry (AMS) dating of this tool type, found in association with in-situ female burial at the Chelechol ra Orrak site, provides a date of AD 150-270, while associated dates range from 770 BC-AD 180. These dates help contextualize human burials and associated artifacts from one of the earliest and most diverse burial sites in Austronesia.
