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Radiocarbon, Volume 47 (2005)
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 47, Number 1 (2005)Department of Geosciences, The University of Arizona, 2005-01-01
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Use of Three Isotopes to Calibrate Human Bone Radiocarbon Determinations from Kainapirina (SAC), Watom Island, Papua New GuineaIn archaeological dating, the greatest confidence is usually placed upon radiocarbon results of material that can be directly related to a defined archaeological event. Human bone should fulfill this requirement, but bone dates obtained from Pacific sites are often perceived as problematic due to the incorporation of 14C from a range of different reservoirs into the collagen via diet. In this paper, we present new human bone gelatin results for 2 burials from the SAC archaeological site on Watom Island, Papua New Guinea, and investigate the success of calibrating these determinations using dietary corrections obtained from d34S, d15N, and d13C isotopes.
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The Stratigraphic Sequence at Yalâ (Yemen): A Statistical EvaluationThe South Arabian chronology has been problematic for a long time and this is also a true vexata quaestio for the ancient history of South Arabia. Three different chronologies have been suggested for the first literate phase of South Arabian cultures, which may date to the 11th century BC, the late 8th century BC, or the 5th century BC (see de Maigret 1996:157-63; de Maigret and Robin 1989: 276-8; Pirenne 1988; Robin 1997; Figure 1). At the site of Yal, potsherds with incised South Arabian inscriptions have been recovered in a stratum dating at least to the 8th century BC, if not earlier, and offer evidence of the existence of South Arabian culture at that time (de Maigret and Robin 1989:288-9).
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The Neolithic Site of Serra Cicora: Results of the AMS Radiocarbon DatingBone and charcoal samples from the Neolithic site of Serra Cicora in the Salento Peninsula (southern Italy) have been dated by accelerator mass spectrometry (AMS). Measurements appear to support other archaeological evidence and have shown that 2 distinct phases of human occupation of the site can be identified: the first occupation in the Early Neolithic and a second occupation in the Middle-Late Neolithic. The results provide new information and are a fundamental contribution to the definition of the absolute chronology of the Middle-Late Neolithic in this part of Europe.
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Testing the “Dicarb Problem”: A Case Study from North AlaskaAn assumption exists in North Alaskan archaeological literature that radiometric assays produced by the nowdefunct Dicarb Radioisotope Co. (Dicarb) are too young or more recent when compared to those produced by other laboratories. This assumption is statistically tested by comparing radiocarbon assays produced by Dicarb to those produced by Beta Analytic, Inc.; Geochron Laboratories; and the NSF-Arizona AMS Facility. The primary data set consists of radiometric and accelerator mass spectrometry (AMS) assays produced from materials excavated at the Croxton site, Locality J, Tukuto Lake, northern Alaska. Statistical analyses demonstrate that 14C assays produced by Dicarb tend to be "younger" than assays produced by other laboratories on crosscheck samples, with differences ranging between 350 and 1440 yr.
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Simultaneously Measuring 14C and Radon in Benzene Dating SamplesAfter benzene synthesis, radiocarbon dating samples are usually stored for 34 weeks before counting to allow an eventual radon contamination to decay to a negligible level. This paper presents a technique that can minimize, and often eliminate, this delay by using a simple single-phototube liquid scintillation counting system, specifically designed for 14C dating. Radon contamination is assessed by pulses of 214Po (a 222Rn decay product, half-life 0.16 microseconds), identified through pulse-time analysis. For each 214Po pulse, 0.49 beta particle pulses of 214Pb and 214Bi fall in the 14C counting window, and the 214Po pulses are used to correct the 14C count rate. A 14C sample (count rate 11.6 cpm) was measured continuously for 16 days. It was then doped with radon, which increased the first 24-hr count rate in the 14C channel by 3.8 cpm, and the sample was measured for 27 more days. Radon did not measurably affect the 14C-corrected count rate. Counting a sample for 2 min reveals whether it needs storing. If the radon concentration is low, the sample can be measured immediately without degrading accuracy.
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Reservoir Effect of the Southern and Southeastern Brazilian CoastA regional marine reservoir correction (Delta-R) of 33 +/24 14C yr for southern Brazil was obtained from 6 marine shell samples collected in the states of Santa Catarina and Paran. This work also presents a R estimation of 8 +/17 14C yr for the southern and southeastern Brazilian coast from the states of Rio de Janeiro to Santa Catarina, obtained by including 7 ages published in previous works. The high variability of R in modern and Holocene samples from the Brazilian coast is also discussed.
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Reconstruction of the 14C Production Rate from Measured Relative AbundanceA new method is presented for the reconstruction of the radiocarbon production rate from the measured relative abundance of ∆14C. 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.
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Reconstruction of Past CO2 Concentration at a Natural CO2 Vent Site Using Radiocarbon Dating of Tree RingsTotal CO2 exposure levels in a naturally enriched site (Lajatico, Italy) were reconstructed using radiocarbon analysis by accelerator mass spectrometry combined with dendrochronological analysis on wood cores extracted from trees grown in the fossil CO2 source proximity. Over 3 decades (1964-1998), the data show a mean CO2 concentration in the atmosphere of 650 ppm, about twice the current concentration in atmosphere, with a maximum around 1980.
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Radiocarbon UpdatesDepartment of Geosciences, The University of Arizona, 2005-01-01New Laboratories, Upcoming Conferences
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Radiocarbon UpdatesDepartment of Geosciences, The University of Arizona, 2005-01-01Rodger Sparks Retires, VIRI Results Needed, Upcoming Conferences
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Re-Dating Mid-Holocene Betelnut (Areca Catechu L.) and Other Plant Use at Dongan, Papua New GuineaDirect accelerator mass spectrometry (AMS) dating of anaerobically preserved plant remains from the Dongan site in New Guinea, combined with assessment of preservation condition, confirms earlier doubts about the antiquity of betelnut (Areca catechu L.) found at the site. A possible sago leaf fragment is also identified as a modern contaminant. The midHolocene age of other fruit and nut remains is verified using these methods. The utility of AMS dating in combination with detailed archaeobotanical assessment is demonstrated, thus improving chronometric hygiene and with it knowledge of past plant use in Oceania.
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Radiocarbon, Soil, and Artifact Chronologies for an Early Southern Oregon Coastal SiteRadiocarbon dates together with geoarchaeological, soil, and lithic analyses are presented to describe archaeological site 35-CS-9 in Bandon Ocean Wayside State Park, Oregon, northwestern USA. One of the few Oregon middleHolocene coastal sites that includes sediments and artifacts dating to the early Holocene and possibly to the late Pleistocene, it was recorded in 1951 and surface surveyed by archaeologists in 1975, 1986, and 1991, but its depth and antiquity were not tested. In February 2002, we studied the sites stratigraphy and sediments and described 8 strata from the aeolian surface to bedrock at 350 cm depth. Soil samples taken from a cut bank for texture classification, particle size analysis, pH, carbon content, and chemical analysis suggested that the site represented a complete history of Holocene deposits. Excavation of 2 test units in August 2002 uncovered substantial lithic and charcoal remains that confirm a protracted middle-Holocene occupation and suggest that human occupation began in the early Holocene. Charcoal recovered at 235-245 cm dated to 11,000 14C BP, and the deepest lithic artifact was recovered in a level at 215-225 cm. Whether the human occupation was continuous throughout the Holocene, and whether it began in the early Holocene or in the late Pleistocene, can only be determined with further excavations.
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Reassessing Human Settlement on the South Coast of San Miguel Island, California: The Use of 14C Dating as a Reconnaissance ToolCalifornias San Miguel Island contains over 600 archaeological sites, some occupied as early as 12,000 yr ago and most located along the islands north coast. Archaeologists have long believed the south coast to have been marginal or largely uninhabited. Burial of some landforms by sand dunes deposited after historical overgrazing, the lack of systematic survey, and a dearth of radiocarbon dating have also contributed to an underestimation of the intensity of human land use along the south coast of San Miguel Island. Our recent reconnaissance and dating of shell middens on the islands south coast indicate more intensive occupation than previously thought, with numerous south coast sites spanning at least the past 9000 yr, and demonstrate the utility of combining systematic archaeological reconnaissance and radiometrics in reconstructions of human settlement and historical ecology in coastal environments.
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Radiocarbon UpdatesDepartment of Geosciences, The University of Arizona, 2005-01-01Software Updates, Upcoming Conferences
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Radiocarbon LaboratoriesDepartment of Geosciences, The University of Arizona, 2005-01-01This is Radiocarbons annual list of active radiocarbon laboratories and personnel known to us. Conventional beta-counting facilities are listed in Part I, and accelerator mass spectrometry (AMS) facilities in Part II. Laboratory code designations, used to identify published dates, are given to the left of the listing.
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Radiocarbon Dating of Modern Peat Profiles: Pre- and Post-Bomb 14C Variations in the Construction of Age-Depth ModelsWe present studies of 9 modern (up to 400-yr-old) peat sections from Slovenia, Switzerland, Austria, Italy, and Finland. Precise radiocarbon dating of modern samples is possible due to the large bomb peak of atmospheric 14C concentration in 1963 and the following rapid decline in the 14C level. All the analyzed 14C profiles appeared concordant with the shape of the bomb peak of atmospheric 14C concentration, integrated over some time interval with a length specific to the peat section. In the peat layers covered by the bomb peak, calendar ages of individual peat samples could be determined almost immediately, with an accuracy of 2-3 yr. In the pre-bomb sections, the calendar ages of individual dated samples are determined in the form of multi-modal probability distributions of about 300 yr wide (about AD 1650-1950). However, simultaneous use of the post-bomb and pre-bomb 14C dates, and lithological information, enabled the rejection of most modes of probability distributions in the pre-bomb section. In effect, precise age-depth models of the post-bomb sections have been extended back in time, into the "wiggly" part of the 14C calibration curve. Our study has demonstrated that where annual resolution is concerned, tissues of Sphagnum are the only representative material for 14C dating, although even samples of pure Sphagnum collected from a very thin slice of the peat section contain tissues grown in different years, so they integrate the atmospheric 14C signal over a period of time. This time period (0.5-8 yr, depending on the site) seems to correlate with the peat accumulation rate, but it also depends on how the sampled peat sections were handled. When constructing age-depth models, for some peat sections we used the strategy of multi-stage 14C dating. This led to a drastic reduction in the uncertainty of the age-depth models, by dating only a few additional samples in the profile. Our study is the first in which peat sections from the late pre-bomb time (AD 1900-1960) have been precisely dated at a high temporal resolution. In this time interval, 14C ages of all the samples dated were younger than those derived from the atmospheric ccalibration curve, apparently due to the effect of integration. Evidently, the determination of calendar ages based on 14C dating of single peat examples from that interval may be affected by a serious error if the possibility of integration is ignored.
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Radiocarbon Dating of Alkenones from Marine Sediments: III. Influence of Solvent Extraction Procedures on 14C Measurements of ForaminiferaAs a result of the growing use of multiple geochemical proxies to reconstruct ocean and climate changes in the past, there is an increasing need to establish temporal relationships between proxies derived from the same marine sediment record and ideally from the same core sections. Coupled proxy records of surface ocean properties, such as those based on lipid biomarkers (e.g. Alkenone-derived sea surface temperature) and planktonic foraminiferal carbonate (oxygen isotopes), are a key example. Here, we assess whether 2 different solvent extraction procedures used for isolation of molecular biomarkers influence the radiocarbon contents of planktonic foraminiferal carbonate recovered from the corresponding residues of Bermuda Rise and Cariaco Basin sediments. Although minor ∆14C differences were observed between solvent-extracted and unextracted samples, no substantial or systematic offsets were evident. Overall, these data suggest that, in a practical sense, foraminiferal shells from a solvent-extracted residue can be reliably used for 14C dating to determine the age of sediment deposition and to examine age relationships with other sedimentary constituents (e.g. Alkenones).
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Radiocarbon Dating of Alkenones from Marine Sediments: II. Assessment of Carbon Process BlanksWe evaluate potential process blanks associated with radiocarbon measurement of microgram to milligram quantities of alkenones at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility. Two strategies to constrain the contribution of blanks to alkenone 14C dates were followed: 1) dating of samples of known age and 2) multiple measurements of identical samples. We show that the potential contamination associated with the procedure does not lead to a systematic bias of the results of alkenone dating to either younger or older ages. Our results indicate that alkenones record ∆14C of ambient DIC with an accuracy of approximately 10. A conservative estimate of measurement precision is 17ppm for modern samples. Alkenone 14C ages are expected to be reliable within 500 yr for samples younger than 10,500 14C yr.
