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Radiocarbon, Volume 49 (2007)
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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Recent Submissions
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Validating and Improving Archaeological Phasing at St. Mary Spital, LondonThis paper outlines the radiocarbon program applied to the excavation and skeletal assemblage from the cemetery of the medieval Priory and Hospital of St. Mary Spital in London. Problems encountered in dating medieval cemeteries are outlined. The problems were addressed through the application of Bayesian modeling to validate and refine conventional approaches to constructing phases of archaeological activity. It should be noted that this project was solely funded by the developer of the land; such projects rarely undertake even modest programs of 14C dating. We aim to show how the investment of a proportionally small sum, compared to the overall project costs, may reap significant benefits.
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Using a Soil Chronosequence to Identify Soil Fractions for Understanding and Modeling Soil Carbon Dynamics in New ZealandWe are developing practical methodologies to characterize pool sizes and residence times for fractions of soil organic matter (SOM) using radiocarbon, with a particular focus on SOM in New Zealand pasture soils that responds to global change on decadal timescales. As single mean residence times for the entire SOM pool can be misleading or uninterpretable, we focus on the use of samples collected about 7 and 40 yr after the bomb-14C spike to separate SOM into at least 2 pools. These results from a box model methodology yield sensible estimates of the proportion of passive SOM, and the residence time of the dominant pool with approximately decadal residence times. These results are supported by chemical analysis. Approximately 45-yr residence times of light-fraction SOM in a relatively infertile soil contrast with ~16-yr residence times in a more fertile soil, and correspond to large differences in the proportion of lignin- and polysaccharide-derived SOM in these soils measured using pyrolysis-GC/MS. To achieve greater detail and assess the degree to which active SOM with annual turnover rates may bias results from the simple model, we use density as a means of isolating SOM with different degrees of mineral association. Initial results from grazed pasture soils sampled in 20034 emphasize that isolating non-mineral-associated light fractions can improve understanding, but may be less important than identifying fractions associated with unique mineralogy. In this soil, a fraction with density =2.55 g/mL shows much larger proportions of passive SOM than other fractions.
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Two Decades of Regular Observations of 14CO2 and 13CO2 Content in Atmospheric Carbon Dioxide in Central Europe: Long-Term Changes of Regional Anthropogenic Fossil CO2 EmissionsTime series are presented of radiocarbon and 13C contents in atmospheric carbon dioxide over eastern Europe (southern Poland), covering the periods 19831994 and 20002004. The carbon isotope composition was measured in biweekly composite samples of atmospheric CO2, collected about 20 m above the local ground level. The data for 2 observational sites are presented: i) city of Krakw (50 degrees 04'N, 19 degrees 55'E; 220 m asl; for 1983-1994 and 2000-2004); and ii) Kasprowy Wierch, Tatra Mountains (49 degrees 14'N, 19 degrees 56'E; 1989 m asl; for 2000-2004). The latter site is considered a regional reference station, relatively free of anthropogenic influences. During the period 1983-1994, observations in the Krakw area revealed a gradual decrease of 14C content with a broad minimum around 1991 and a small increase by about 10 in the subsequent years. d13C also changes with time, showing a decreasing trend from approximately 9.6 in 1983, with a slope of 0.02/yr. The observed trends for both isotopes coincide well with a substantial reduction of coal consumption in Poland and partial replacement of coal by natural gas, especially in urban regions. After 2000, the d13C slightly increases, reaching a mean value of 10 in 2004, while delta-14C is below the reference level by ~3.5. Observations at Kasprowy Wierch (regional reference station) also reflect a diminishing input of fossil carbon into the regional atmosphere. The fossil component in atmospheric CO2, calculated with the aid of 14C data available for the 2 study periods, shows a reduction of anthropogenic input by a factor of 2, which is confirmed by annual statistics of coal consumption.
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Tropical South China Sea Surface 14C Record in an Annually-Banded CoralA surface-water 14C record of AD 1948-1999 in the tropical South China Sea (SCS) has been reconstructed from accelerator mass spectrometric radiocarbon measurements of annual bands of a Porites coral collected from Con Dao Island, Vietnam. Results gave the following 14C time series: a steady state of 47.8 +/- 2.8 (mean SD, n = 8) during 1948-1955 (i.e. in the pre-bomb period); a sharp increase during 1956-1966; a gradual increase during 1967-1973; a relatively high maximum value of ~174 in 1973; and a gradual decrease for the following period to ~86 in 1999. This 14C record having a sharp increase and a relatively high peak is similar to the records of subtropical corals (latitudes 21-27) and is distinctly different from the records of equatorial/tropical corals (latitudes 10), although our coral sample was collected from an equatorial/tropical region (8 degrees 39'N, 106 degrees 33'E). This can be explained by the geographic, oceanographic, and climatic setting of our study site. The SCS is a semi-enclosed marginal sea in the far western tropical Pacific and is little influenced by equatorial upwelling or related ocean currents. Our study site is located in the southwestern SCS, where an enormous submerged plain (the Sunda Shelf) spreads out with very shallow waters (mean depth 100 m). Furthermore, in the SCS, the East Asian monsoon (a strong, seasonally reversing wind system) enhances air-sea gas exchange especially in the mainland coastal waters, including our study site. Such semi-enclosed shallow waters with enhanced ventilation were probably very sensitive to the atmospheric nuclear explosions in the late 1950s and early 1960s and caused the sharp increase and high peak in the coral 14C record. Our coral 14C values in the southwestern SCS are significantly higher than the values in the northwestern SCS (Xisha Islands), which seems to suggest that meridional mixing of surface waters is not active in the SCS and that the open-ocean water intruding into the northern SCS (i.e. the Kuroshio intrusion) has only a limited influence on the southern SCS.
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Timescale for Climatic Events of Subboreal/Subatlantic Transition Recorded at the Valakupiai Site, LithuaniaOxbow lake deposits of the Neris River at the Valakupiai site in Vilnius (Lithuania) have been studied by different methods including radiocarbon dating. A timescale was attained for the development of the oxbow lake and climatic events recorded in the sediments. 14C dates obtained for 24 samples cover the range 990-6500 BP (AD 580 to 5600 BC). Medieval human activity was found in the upper part of the sediments. Mollusk fauna found in the basal part of the terrace indicate contact between people living in the Baltic and the Black Sea basins. Mean rates were calculated for erosion of the river and for accumulation during the formation of the first terrace.
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The Freshwater Reservoir and Radiocarbon Dates on Cooking Residues: Old Apparent Ages or a Single Outlier? Comments on Fischer and Heinemeier (2003)Fischer and Heinemeier (2003) present a hypothesis that the freshwater reservoir effect produces old apparent ages for radiocarbon dates run on charred cooking residues in regions where fossil carbon is present in groundwater. The hypothesis is based in part on their analysis of dates on charred cooking residues from 3 inland archaeological sites in Denmark in relation to contextual dates from those sites on other materials. A critical assessment of the dates from these sites suggests that rather than a pattern of old apparent dates, there is a single outlying datenot sufficient evidence on which to build a case for the freshwater reservoir effect.
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The Early Medieval Origin of Perth, ScotlandThe radiocarbon results (and Bayesian modeling) of 15 samples of carbonized food residues removed from the external surface of rim sherds of cooking pots indicate that shellyware pottery first appeared in Perth, Scotland, around cal AD 910-1020 (95% probability) and that it had disappeared by cal AD 1020-1140 (95% probability). Previously, it had been suggested that this pottery could not date to before AD 1150. These data, together with 14C analyses carried out on leather artifacts and a sample of wattle from a ditch lining, also demonstrate that there was occupation in Perth about 100 yr or more prior to the granting of royal burgh status to Perth in the 1120s.
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The Feasibility of Using Melanopsis Shells as Radiocarbon Chronometers, Lake Kinneret, IsraelWe investigated the feasibility of using Melanopsis shells as radiocarbon chronometers of paleolakes and springs in the Jordan Valley, Israel. For this purpose, we analyzed the 14C content of aragonite of living Melanopsis shells from different freshwater bodies of the northern Jordan Valley and Lake Kinneret (Sea of Galilee) and compared them to the contemporaneous water values. The Melanopsis shells are in 14C equilibrium with their habitat waters, allowing to specify a particular reservoir age for various water types. We measured ~750 yr for Lake Kinneret, ~2300 yr for northern Jordan, ~4600 yr for springs in the north Kinneret, and ~7200 yr for streams flowing directly from carbonate aquifers. These results were tested and corroborated by analyzing fossil Melanopsis shells of known age, measured on contemporaneous organic matter. We conclude that Melanopsis shells are reliable 14C chronometers and have the potential to be used as paleohydrological tracers.
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The End of Empire: New Radiocarbon Dates from the Ayacucho Valley, Peru, and Their Implications for the Collapse of the Wari StateThis paper presents a suite of new accelerator mass spectrometry (AMS) radiocarbon measurements from the Ayacucho Valley of Peru and discusses their implications for the timing and nature of the collapse of the Wari Empire. Analysis of these and previously published dates from the region indicate that there is little evidence for state political authority in Ayacucho prior to the end of the 7th century. Dated human remains from the politys eponymous capital indicate that the authority of the states rulers persisted at least as late as the mid-11th century. Dates from rural sites in the Ayacucho Valley suggest continuity of occupation and folk material culture following Waris disintegration. Finally, AMS measurements of bone from 2 large extramural ossuaries represent the first absolute dates associated with Chanca ceramics and suggest that this archaeological/ethnohistoric culture appeared in the valley at about AD 1300.
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The Catacomb Cultures of the North-West Caspian Steppe: 14C Chronology, Reservoir Effect, and PaleodietFor the Bronze Age Catacomb cultures of the North-West Caspian steppe area in Russia, there is a conflict between the traditional relative archaeological chronology and the chronology based on radiocarbon dates. We show that this conflict can be explained largely by the fact that most dates have been obtained on human bone material and are subject to 14C reservoir effects. This was demonstrated by comparing paired 14C dates derived from human and terrestrial herbivore bone collagen. In addition, values of stable isotope ratios (d13C and d15N) and analysis of food remains from vessels and the stomach contents of buried individuals indicate that a large part of the diet of these cultures consisted of fish and mollusks, and we conclude that this is the source of the reservoir effect.
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Subject indexDepartment of Geosciences, The University of Arizona, 2007-01-01
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Spatial Variability of Bomb 14C in an Upland Peat BogAs part of a study investigating the carbon balance of a blanket bog, we made an assessment of the spatial variation of radiocarbon concentrations in the surface layers of a small area of peatland in the north of England. The peat depth at which bomb-14C content was the highest varied considerably between cores sampled from across the site. At several sampling locations, 14C levels >100% Modern were confined to the surface 8 cm, whereas bomb 14C was evident at 1 site, located only meters away, to a depth of at least 1216 cm. Using the layer where 14C levels first exceeded 100% Modern as a chronological reference layer, we estimated the carbon accumulation rate over the last 50 yr for the surface peat at each site (range ~20 to ~125 mu-g C m2 yr1). Our results show that although carbon accumulation over the last 50 yr was similar across the site, variation in the depth to which bomb 14C was evident implied considerable variation in the vertical peat growth rate.
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Seoul National University Accelerator Mass Spectrometry (SNU-AMS) Radiocarbon Date List IVThe accelerator mass spectrometry (AMS) facility at Seoul National University (SNU-AMS) was accepted in December 1998 and results reported first at the Vienna AMS conference in October 1999 and at the 17th Radiocarbon Conference in Israel, June 2000. At the Vienna conference, we reported our accelerator system and sample preparation systems (Kim et al. 2000). Recent developments of the AMS facility have been regularly reported at AMS conferences (Kim et al. 2001, 2004, 2007). Meanwhile, about 1000 unknown archaeological, geological, and environmental samples have been measured every year. In this report, the archaeological and geological data carried out in 2002 are presented in terms of years BP (before present, AD 1950), following the SNU-AMS date lists I and II published in Radiocarbon (Kim et al. 2006a,b).
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Seasonal Variation in Sources of Dissolved Organic Carbon in a Lacustrine Environment Revealed by Paired Isotopic Measurements (Δ14C and δ13C)To investigate the sources and cycling of dissolved organic carbon (DOC) in a lacustrine environment, isotopic measurements of 14C and 13C in DOC were carried out for Lake Kasumigaurawhich is famous as a very eutrophic and shallow (mean depth 4.0 m) lake in central Japanand its tributary rivers. Lake and river samples were collected in the spring and autumn (May and September) of 2003. The ∆14C measurements of DOC were performed using the accelerator mass spectrometer at the National Institute for Environmental Studies (NIES-TERRA), Japan. In September, the 14C values of DOC were light (around -200) and did not differ significantly between lake and river water samples, indicating that DOC in Lake Kasumigaura and its tributary rivers yields older 14C ages than the age expected from the lake-water residence time (average 200 days). This result suggests that terrestrial sources are important contributors to DOC in Lake Kasumigaura. Nevertheless, 13C values indicated that during spring, DOC in the lake is mainly autochthonous. Thus, sources and cycling of DOC in Lake Kasumigaura may vary seasonally.
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Seoul National University Accelerator Mass Spectrometry (SNU-AMS) Radiocarbon Date List IIIThe accelerator mass spectrometry (AMS) facility at Seoul National University (SNU-AMS) was accepted in December 1998 and results reported first at the Vienna AMS conference in October 1999 and at the 17th Radiocarbon Conference in Israel, June 2000. At the Vienna conference, we reported our accelerator system and sample preparation systems (Kim et al. 2000). Recent developments of the AMS facility have been regularly reported at AMS conferences (Kim et al. 2001, 2004, 2007). Meanwhile, about 1000 unknown archaeological, geological, and environmental samples have been measured every year. In this report, the archaeological and geological data carried out in 2001 are presented in terms of years BP (before present, AD 1950), following the SNU-AMS date lists I and II published in Radiocarbon (Kim et al. 2006a,b).
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Seasonal Variations in Peruvian Marine Reservoir Age from Pre-Bomb Argopecten purpuratus Shell CarbonateMarine upwelling along coastal Peru can be intense and variable, making radiocarbon dating marine and coastal systems complex. Historical and proxy records of upwelling along coastal Peru are few, and long-lived species such as corals do not grow in the cold coastal waters. Mollusk shell carbonate, however, can record both the magnitude of the local marine reservoir correction, Delta-R, and of seasonal oscillations in the ventilation age of coastal waters. If large, these seasonal oscillations would complicate radiocarbon dating of marine organisms. To examine this possibility, we sampled for d13C, delta-18O, and 14C content a set of pre-bomb Argopecten purpuratus shells collected from coastal Peru during 1908 and 1926. Intrashell variations of up to 216 14C yr were noted, but these were not consistently correlated with seasonal changes in delta-18O or d13C. Only an 11 yr difference was observed in the weighted average Delta-R of Callao Bay shells collected during normal (1908) and El Nio (1926) years. Despite the intrashell 14C variation noted, weighted average Delta-R values from all 3 sample sites and from normal and El Nio years all overlap at 1 sigmaWe report Delta-R values of 183 +/- 18 and 194 +/- 23 yr from Callao Bay (124'S), 165 +/- 24 yr from Salaverry (8 degrees 14'S), and 189 +/- 23 yr from Sechura Bay (5degrees 45'S).
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Results of Radiocarbon Analysis of Upper Weichselian Loess Sequences from HungaryApproximately 10% of Hungary is covered by dust sequences of the Quaternary period. Samples have been taken from more than 50 outcrops and boreholes during fieldwork in the past 20 yr. Some 81 bulk samples taken from 27 profiles of the Hungarian loess regions have been analyzed for radiocarbon. Based on the 14C results, loess layers that accumulated between 33,000 and 12,000 BP were selected for further investigation. The sedimentation rates of the 27 loess profiles suggest periods of slow and quick dust accumulation in the Carpathian Basin during the Upper Weichselian period. It seems to us that some soil development and intense weathering periods interrupted the loess development during the Upper Weichselian in Hungary. According to the 14C dates, the estimated average rate of sedimentation was 0.31 mm/yr in both the northern and southern parts of the Carpathian Basin between 33,000 and 12,000 BP.
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Reservoir Effect of Coastal Waters off Western and Northwestern GaliciaDifferences in the radiocarbon ages of closely associated marine mollusk shells and terrestrial material (charred wood or bones) from several Galician archaeological contexts are significant from the Iron Age to Medieval times. Delta-R values show high variability, ranging from 280 +/- 70 to 270 +/- 40 14C yr. The set of Delta-R values also presents a strong positive peak (Delta-R = 270 +/- 40 14C yr) at 860 +/- 90 BP, which matches another peak found for western Portuguese coastal waters. The data obtained, namely the negative or close to zero R values, suggest that the reduced offset between atmospheric and surface water 14C content is due to the existence of a strong stratification of the water column and environmental factors in the Galician rías during the Iron Age and the Medieval period.
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Reservoirs and Radiocarbon: 14C Dating Problems in Mýatnssveit, Northern IcelandThis paper examines 2 potential sources of the radiocarbon offset between human and terrestrial mammal (horse) bones recovered from Norse (~AD 870-1000) pagan graves in Mývatnssveit, north Iceland. These are the marine and freshwater 14C reservoir effects that may be incorporated into human bones from dietary sources. The size of the marine 14C reservoir effect (MRE) during the Norse period was investigated by measurement of multiple paired samples (terrestrial mammal and marine mollusk shell) at 2 archaeological sites in Mývatnssveit and 1 site on the north Icelandic coast. These produced 3 new Delta-R values for the north coast of Iceland, indicating a Delta-R of 106 +/- 10 14C yr at AD 868-985, and of 144 +/- 28 14C yr at AD 1280-1400. These values are statistically comparable and give an overall weighted mean R of 111 +/- 10 14C yr. The freshwater reservoir effect was similarly quantified using freshwater fish bones from a site in Mývatnssveit. These show an offset of between 1285 and 1830 14C yr, where the fish are depleted in 14C relative to the terrestrial mammals. This is attributed to the input of geothermally derived CO2 into the groundwater and subsequently into Lake Mývatn. We conclude the following: i) some of the Norse inhabitants of Mývatnssveit incorporated non-terrestrial resources into their diet that may be identified from the stable isotope composition of their bone collagen; ii) the MRE off the north Icelandic coast during the Norse period fits a spatial gradient of wider North Atlantic MRE values with increasing values to the northwest; and iii) it is important to consider the effect that geothermal activity could have on the 14C activity of samples influenced by groundwater at Icelandic archaeological sites.
