RSS 1.0Radiocarbon, Volume 42 (2000)
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 42, Number 3 (2000)Department of Geosciences, The University of Arizona, 2000-01-01
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Radiocarbon, Volume 42, Number 2 (2000)Department of Geosciences, The University of Arizona, 2000-01-01
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Radiocarbon, Volume 42, Number 1 (2000)Department of Geosciences, The University of Arizona, 2000-01-01
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Editorial BoardDepartment of Geosciences, The University of Arizona, 2000-01-01
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A Tribute to Renee Kra: Radiocarbon Managing Editor for Thirty YearsDepartment of Geosciences, The University of Arizona, 2000-01-01
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Radiocarbon in the OceanIn addition to dating, radiocarbon has heen widely used as a tracer in the study of the global carbon cycle. And particularly the exchange of CO2 between the atmosphere and the ocean. The anthropogenic input of 14C from nuclear weapons tests in the atmosphere stimulated this research. Developing from frequent measurements made in the atmosphere and ocean's surface, the measuremens later became more focused towards understanding the circulation in the deep ocean. From a few attempts at the end of 1950 to measure the 14C increase in the ocean surface (Rafter and Fergusson 1957), the measurement program developed to include such programs as GEOSECS, TTO, JGOFS, SAVE, and WOCE, which obtain comprehensive ocean data, including 14C for the study of ocean circulation. Only in the ocean surface has it been possible to obtain timeseries of 14C measurements as in the atmosphere. For the deep ocean, repeat measurements arc generally several years apart. This sampling frequency is probably sufficient for the majority of the deep ocean. With its long time scale of change.
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What Future for Radiocarbon?n 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.
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The Use of Bayesian Statistics for 14C Dates of Chronologically Ordered Samples: A Critical AnalysisBayesian mathematics provides a tool for combining radiocarbon dating results on findings from an archaeological context with independent archaeological information such as the chronological order, which may be inferred from stratigraphy. The goal is to arrive at both a more precise and a more accurate date. However, by means of simulated measurements we will show that specific assumptions about prior probabilities—implemented in calibration programs and not evident to the user—may create artifacts. This may result in dates with higher precision but lower accuracy, and which are no longer in agreement with the true ages of the findings.
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The Radiocarbon Content of Individual Lignin-Derived Phenols: Technique and Initial ResultsWe present a method for the isolation of phenolic compounds derived from lignin for radiocarbon analysis.These phenols are generated by chemical oxidation of polymeric materials and derivatized for separation and recovery by pre-parative capillary gas chromatography (PCGC). This technique yields tens of micrograms of pure, stable compounds that canbe converted to graphite and analyzed by accelerator mass spectrometry (AMS). Analysis of model flavor compounds anddated woods indicates that, in most cases, the radiocarbon (14C) contents of the individual compounds, corrected for the con-tribution of the derivative, agree with that of the bulk material to within 20‰.
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The Contribution of Radiocarbon Dating to New World ArchaeologyWhen introduced almost five decades ago, radiocarbon (14C) dating provided New World archaeologists with a common chronometric scale that transcended the countless site-specific and regional schemes that had been developed by four generations of field researchers employing a wide array of criteria for distinguishing relative chronological phases. A topic of long standing interest in New World studies where 14C values have played an especially critical role is the temporal framework for the initial peopling of the New World. Other important issues where 14C results have been of particular importance include the origins and development of New World agriculture and the determination of the relationship between the western and Mayan calendars. It has been suggested that the great success of 14C was an important factor in redirecting the focus of American archaeological scholarship in the 1960s from chronology building to theory building, led to a noticeable improvement in US archaeological field methods, and provided a major catalyst that moved American archaeologists increasingly to direct attention to analytical and statistical approaches in the manipulation and evaluation of archaeological data.
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Subfossil Tree Deposits in the Middle Durance (Southern Alps, France): Environmental Changes from Alleröd to AtlanticThe purpose of this paper is to analyze the numerous holocene subfossil trees (Pinus silvestris) buried in alluvial deposits in the Southern French Alps. These trees lived between the Allerod and Subboreal periods, according to 14C dates. Our dendochronological studies explain the trees' sudden death as due to morphological crisis brought on by climatic oscillations. Tree-ring series could be used to identify the variability of early Holocene atmospheric 14C levels.
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Some Comments on Accelerator Mass SpectrometryThis 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.
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Southwest Subtropical Pacific Surface Water Radiocarbon in a High-Resolution Coral RecordWe have generated a high-resolution coral D14C record from the southwest subtropical Pacific spanning the last 50 yr. Prebomb (1950-1956) Delta-14C values average -52‰. Values begin to increase in 1957, reaching a maximum in the early 1970s, about 10 yr after the atmospheric peak. There is a consistent 10-15‰ seasonal cycle whose relationship with vertical mixing evolves as a consequence of the penetration of the bomb transient into subsurface waters. Comparison of this record with that simulated in an ocean general circulation model highlights the difficulty in modeling vertical exchange processes.
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Redating Iztapan and Valsequillo, MexicoRecent radiocarbon dating of tephra sequences and biostratigraphic analysis in the Valley of Mexico and the Valley of Puebla, respectively, reveal that the FAD (first appearance date) for lanceolate Lerma/El Jobo points at Iztapan and Hueyatlaco archeological sites at about 14-16,000 BP predates the Clovis culture FAD. A lack of interdisciplinary communication is responsible for the neglect of these sites for three decades.
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Radiocarbon UpdatesDepartment of Geosciences, The University of Arizona, 2000-01-01
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Radiocarbon UpdatesDepartment of Geosciences, The University of Arizona, 2000-01-01
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Radiocarbon Levels in the Iceland Sea from 25-53 kyr and Their Link to the Earth's Magnetic Field IntensityBy correlating the climate records and radiocarbon ages of the planktonic foraminifera N. Pachyderma(s) of deep-sea core PS2644 from the Iceland Sea with the annual-layer chronology of the GISP2 ice core, we obtained 80 marine 14C calibration points for the interval 11.4-53.3 ka cal BP. Between 27 and 54 ka cal BP the continuous record of 14C/cal age differences reveals three intervals of highly increased 14C concentrations coincident with low values of paleomagnetic field intensity, two of which are attributed to the geomagnetic Mono Lake and Laschamp excursions (33.5-34.5 ka cal BP with maximum 550 per mil marine Delta-14C, and 40.3-41.7 ka cal BP with maximum 1215 per mil marine Delta-14C, respectively). A third maximum (marine Delta-14C: 755 per mil) is observed around 38 ka cal BP and attributed to the geomagnetic intensity minimum following the Laschamp excursion. During all three events the Delta-14C values increase rapidly with maximum values occurring at the end of the respective geomagnetic intensity minimum. During the Mono Lake Event, however, our Delta-14C values seem to underestimate the atmospheric level, if compared to the 36Cl flux measured in the GRIP ice core (Wagner et al. 2000) and other records. As this excursion coincides with a meltwater event in core PS2644, the underestimation is probably caused by an increased planktonic reservoir age. The same effect also occurs from 38.5 to 40 ka cal BP when the meltwater lid of Heinrich Event 4 affected the planktonic record.
