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  • 1
    Electronic Resource
    Electronic Resource
    Radiocarbon redating of contaminated samples from a tropical volcano: the Mansion ‘Series’ of St Kitts, West Indies (1994)
    Springer
    Bulletin of volcanology 56 (1994), S. 326-334 
    Details
    ISSN: 1432-0819
    Keywords: Lesser Antilles ; St Kitts ; Mt Liamuiga radiocarbon dating ; charcoal contamination stratigraphy ; pyroclastic deposits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Heavy rainfall and dense vegetation on tropical volcanoes produce abundant carbonized wood in pyroclastic deposits, in addition to easy contamination of this wood by root systems and soluble humic material. Because the physical nature of the charcoal varies, some samples are more prone to contamination. Two independent studies of the same volcano, Mt Liamuiga on St Kitts in the Lesser Antilles, sometimes using samples from the same carbonized tree, yielded a systematic difference in radiocarbon ages. An exchange of samples and a re-investigation of three physically distinct types of charcoal yielded the following results. Rare, hard, dense charcoal, lacking contamination, which had yielded a spurious age of 2860 years bp, was redated at 1845±58 years bp. Common soft, friable charcoal with good cellular structure proved to be susceptible to contamination. A field decontamination technique utilized by one group seems significant as it yields older ages than when only routine laboratory pre-treatment was used, indicating that the latter technique only partly removes the dried and hard residue produced by the decomposition of modern plant rootlets. A previous date of 24870 years bp obtained from powdery charcoal in a horizon beneath the Mansion ‘Series’ contradicted ages older than 41000 years bp from common friable charcoal in the lower Mansion ‘Series’. The soft powdery charcoal was re-investigated using a sample collected a few centimeters from the original, although field decontamination of this sample was not possible, more extensive laboratory treatment yielded an age of ca. 43000 years bp, again proving that routine laboratory pretreatments are inadequate. A revised geochronology for the Mansion ‘Series’ is described and a cautionary discussion is presented for the benefit of investigators using radiocarbon ages to date volcanic deposits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326459
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  • 2
    Electronic Resource
    Electronic Resource
    Carbon-14 in the Biosphere and Humans (1969)
    [s.l.] : Nature Publishing Group
    Nature 223 (1969), S. 1216-1218 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Many methods have been used to calculate the quantity of carbon-14 reaching human bodies from the environment as a result of nuclear fission and fusion. Comparisons with measurements of carbon-14 in blood samples show that these calculations can be wrong, particularly during the first ten years ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/2231216a0
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  • 3
    Electronic Resource
    Electronic Resource
    Radionuclide dating of the recent sediments of Blelham Tarn (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 6 (1976), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Lake sediments of the last 1000 years provide a unique record of environmental changes. Methods of dating this record are reviewed and discussed. Sediments of the last 20 years, which are of particular biological significance because of their record of man-made changes in lakes (including enrichment and pollution) have been dated successfully by the distribution within them of the fallout product 137Cs, present in the atmosphere since 1954 and reaching a peak of supply in 1963. The structured pattern shown by the curve for 137Cs concentration in most sediments investigated indicates that faunal mixing of the surface muds does not destroy the vertical stratification of the sediment profile.Sediments up to 120 years old have been dated by a lead isotope technique, and the results of this proved consistent with both 137Cs dating and with palaeomagnetic dating where this was possible.Theoretical considerations of the application of radiocarbon dating to organic material of 18th and 19th century date are reviewed.Results of application of these radionuclide techniques to the sediments of a small lake, Blelham Tarn, near Windermere, are presented. Evidence from 137Cs and 210Pb dating of profiles from several different positions within the lake shows that the depth of the annual increment to the sediments varies by a factor of × 2 from place to place. The concentration within the sediment of chemical and biological variables shows no significant variation from one position to another; therefore calculated values for amounts of each variable included within unit area of the annual increment depend primarily on the thickness of this at the site chosen, and so cannot be directly related to the rates of supply of, for example, pollen grains or total organic matter, and so to rates of productivity.Results from nine 14C dates on material 400–1000 years old, when correlated with analyses for pollen and sediment composition, demonstrate the profound effects of agricultural practices in the catchment (assumed to be deforestation and ploughing) in disturbing the orderly transfer to lake sediments of material eroded from the catchment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1976.tb01617.x
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of soil processes on carbon isotope distribution and turnover in the British uplands (1999)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 50 (1999), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Understanding the natural variation of carbon within the soil, and between soil types, is crucial to improve predictive models of carbon cycling in high and mid-latitude ecosystems in response to global warming. We measured the carbon isotope distributions (12C, 13C and 14C) in soil organic matter (SOM) from Podzols, Brown Podzolic soils and Stagnohumic Gleysols from the British uplands, which were then compared with the total amounts and turnover of carbon in these soils. We did so by sampling at 2-cm intervals down six profiles of each soil type. The average amount of carbon stored in the top 28 cm of the Stagnohumic Gleysols is twice that of the other two soils. The 13C content and 14C age show a general increase with depth in all soils, and there is also a significant correlation between isotopic variation and the main pedogenic features. The latter suggests that soil-forming processes are significant in determining the carbon isotope signatures retained in SOM. Organic matter formed since 1960 is not found below 5 cm in any of the soils. Evidently organic detritus in the surface layers (LF and Oh) is rapidly mineralized. This accords with our modelled net annual C fluxes which show that more than 80% of the CO2 emanating from these soils is derived from the top 5 cm of each profile. Although these soils contain much carbon, they do not appear to assimilate and retain SOM rapidly. The mean residence time of most of their carbon is in the 2–50 years range, so the soils are fairly ineffective sinks for excess CO2 in the atmosphere. Under the predicted future ‘greenhouse’ climate, likely to favour more rapid microbial decomposition of organic materials, these soils are a potential source of CO2 and are therefore likely to accelerate global warming.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.1999.00222.x
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  • 5
    Electronic Resource
    Electronic Resource
    Accumulation rates of hydrothermal metalliferous sediments in the Lau Basin, S. W. Pacific (1986)
    Springer
    Geo-marine letters 6 (1986), S. 51-56 
    Details
    ISSN: 1432-1157
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Five cores were recovered on a traverse in the Lau Basin at 18°30′S crossing a supposed active spreading center. The sediments were subjected to selective chemical leaching for Mn, Fe, Cu, Zn, and As. Accumulation rates were determined using14C. These rates increase from west to east, reflecting the influence of volcaniclastic inputs from the Tonga- Kermadec Ridge. All elements display highest non-detrital accumulation rates closest to the supposed spreading center, suggesting a hydrothermal input to the sediments there. Variable hydrothermal inputs also influence the other cores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02311696
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  • 6
    Electronic Resource
    Electronic Resource
    Carbon dating (1989)
    [s.l.] : Nature Publishing Group
    Nature 342 (1989), S. 730-730 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR-With respect to your News item on radiocarbon laboratories (Nature 341, 267; 1989), we wish to correct some factual inaccuracies and to emphasize that the recent carbon-14 workshop marked a sig-nificant step forward by the international dating community towards improving and refining an ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/342730c0
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  • 7
    Electronic Resource
    Electronic Resource
    Further Investigations of the Transfer of Bomb 14 C to Man (1972)
    [s.l.] : Nature Publishing Group
    Nature 240 (1972), S. 302-303 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Two factors have been considered as the major contributors to the general damping effect noted for human 14C concentrations compared with atmospheric 14C variations: first, the selective composition of the human diet and, second, the finite residence time for carbon in human tissues. Our study has ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/240302a0
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  • 8
    Electronic Resource
    Electronic Resource
    A recently extinct palm from Easter Island (1984)
    [s.l.] : Nature Publishing Group
    Nature 312 (1984), S. 750-752 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The pollen record2 shows that palms have existed on Easter Island since at least 37,000 BP, but declined to extinction within the past 1,000 years. The fossil pollen (Fig. la)is of themonocol-pate typewith a rough surface, which is common to many palm genera including Cocos4 and Pritchardia5, both ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/312750a0
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  • 9
    Electronic Resource
    Electronic Resource
    Radiocarbon redating of contaminated samples from a tropical volcano: the Mansion 'Series' of St Kitts, West Indies (1994)
    Springer
    Bulletin of volcanology 56 (1994), S. 326-334 
    Details
    ISSN: 1432-0819
    Keywords: Key wordsLesser Antilles ; St Kitts ; Mt Liamuiga ; radiocarbon dating ; charcoal contamination ; stratigraphy ; pyroclastic deposits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Heavy rainfall and dense vegetation on tropical volcanoes produce abundant carbonized wood in pyroclastic deposits, in addition to easy contamination of this wood by root systems and soluble humic material. Because the physical nature of the charcoal varies, some samples are more prone to contamination. Two independent studies of the same volcano, Mt Liamuiga on St Kitts in the Lesser Antilles, sometimes using samples from the same carbonized tree, yielded a systematic difference in radiocarbon ages. An exchange of samples and a re-investigation of three physically distinct types of charcoal yielded the following results. Rare, hard, dense charcoal, lacking contamination, which had yielded a spurious age of 2860 years bp, was redated at 1845±58 years bp. Common soft, friable charcoal with good cellular structure proved to be susceptible to contamination. A field decontamination technique utilized by one group seems significant as it yields older ages than when only routine laboratory pre-treatment was used, indicating that the latter technique only partly removes the dried and hard residue produced by the decomposition of modern plant rootlets. A previous date of 24 870 years bp obtained from powdery charcoal in a horizon beneath the Mansion 'Series' contradicted ages older than 41 000 years bp from common friable charcoal in the lower Mansion 'Series'. The soft powdery charcoal was re-investigated using a sample collected a few centimeters from the original, although field decontamination of this sample was not possible, more extensive laboratory treatment yielded an age of ca. 43 000 years bp, again proving that routine laboratory pre-treatments are inadequate. A revised geochronology for the Mansion 'Series' is described and a cautionary discussion is presented for the benefit of investigators using radiocarbon ages to date volcanic deposits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326459
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  • 10
    Electronic Resource
    Electronic Resource
    The influence of fertilizer nitrogen and season on the carbon-13 abundance of wheat straw (1995)
    Springer
    Plant and soil 171 (1995), S. 365-367 
    Details
    ISSN: 1573-5036
    Keywords: carbon-13 ; carbon isotope fractionation ; nitrogen fertilization ; winter wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Carbon-13 abundance, expressed as δ13C in ‰, was measured in wheat straw grown between 1984 and 1989 on the Broadbalk Continuous Wheat Experiment at Rothamsted. In all six years, straw grown without fertilizer N contained less carbon-13 (i.e.δ13C was more negative) than straw grown with fertilizer, although the magnitude of this difference varied with year. In a dry year, when dry matter response to fertilizer N was relatively small, there was a large difference between the δ13C of straw grown with and without N. Conversely, in a wet year, when there was a marked response to N, there was little difference in the isotopic composition of N-fertilized and unfertilized straw. Over the six years, the difference between the δ13C value of straw grown with and without nitrogen (D 13C, in ‰) was related to drought, measured as the calculated soil water deficit on 15 July (Wj, in mm), by the equation D 13C=−0.299+0.01034 Wj (r=0.87). H Lambers Section editor
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010293
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