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  • Articles  (8)
  • Cambridge University Press  (8)
  • American Institute of Physics (AIP)
  • Archaeology  (8)
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  • Articles  (8)
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  • Cambridge University Press  (8)
  • American Institute of Physics (AIP)
  • Elsevier  (3)
  • Wiley  (2)
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  • 1
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    Assessing the Effect of Sterilization on the Radiocarbon Signature of Freshwater Dissolved Organic Carbon (2011)
    Cambridge University Press
    Details
    Publication Date: 2011-01-01
    Description: Radiocarbon analysis of freshwater dissolved organic carbon (DOC) involves substantial sample pretreatment, including an initial rotary evaporation stage necessary to concentrate large volumes of freshwater sample. This may lead to a health risk from the exposure to pathogens, and there is the additional concern that the warm conditions during the rotary evaporation stage may provide ideal growing conditions for some pathogens. To remove any pathogen risk in water samples, boiling or autoclaving can be undertaken. However, to date, no studies have been undertaken to investigate whether boiling will alter the 14C signature of dissolved organic carbon. Here, we analyze the effect of sterilization on 9 contrasting river water samples. Comparing filtered, filtered and boiled, and filtered and sterilized dissolved organic matter, we observe that both boiling and autoclaving increases the uncertainty associated with the 14C and 13C of DOC, that the 14C and 13C changes are not unidirectional, and that they are not related to original DOC composition. Neither sterilization method is recommended unless essential, in which instance we recommend a 3σ uncertainty on 14C and that the 13C is not considered representative of the original sample.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 2
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    Coastal Response to Changes in Sea Level Since the Last 4500 BP On the East Coast of Tamil Nadu, India (2002)
    Cambridge University Press
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    Publication Date: 2002-01-01
    Description: Geomorphology, clay mineral composition, and radiocarbon dates from Muttukadu to Marakkanam estuaries and the tidal zone along the east coast of Tamil Nadu, India, have been used to reconstruct coastal evolution between approximately 4500 and 1100 B P. Formation of alternate oyster beds with intervening tidal clay units indicate fluctuation in the sea level may be a consequence of changes in the Mid-Holocene sedimentation pattern and coastal configuration. 14C dates from Muttukadu indicate a rapid relative sea-level rise (RSL) subsequent to 3500 BP and tidal flat sedimentation between 3475 and 3145 BP. Marine conditions along the east coast area returned around 1900 B P. Comparison of dates with other sites, e.g. Muttukadu, Mammallapuram, and Marakkanam, points toward short removal of marine conditions, ample sediment supplies in the tidal zones, and neotectonic activity. Reactivation of the north–south trending fault line occurred not earlier than approximately 1050 B P. Our study indicates that Middle to Late Holocene coastal sedimentation and the chronology of the tidal zone formation have been strongly influenced by local factors. These have provided considerable scope for internal reorganization with changing coastal processes.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 3
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    National Physical Laboratory Radiocarbon Measurements II (1964)
    Cambridge University Press
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    Publication Date: 1964-01-01
    Description: The following list comprises measurements made since those reported in NPL I and is complete to the end of November 1963.Ages are relative to a.d. 1950 and are calculated using a half-life of 5568 yr. The measurements have been corrected for fractionation and referred to 0.950 times the activity of the NBS oxalic acid as a contemporary reference standard. The quoted uncertainty is one standard deviation derived from a proper combination of the parameter variances, viz. those of the standard and background measurements over a rolling twenty-week period, of the sample measurements from at least three independent fillings, of the δC13 measurements and of the de Vries effect (assumed to add an additional uncertainty equivalent to a standard deviation of 80 yr). Any uncertainty in the half-life has been excluded so that relative C14 ages may be correctly compared. Absolute age assessments, however, should be made using the accepted best value for the half-life and the appropriate uncertainty included. If the net sample activity is less than 4 times the standard error of the difference between the sample and background activities, a lower limit to the age is reported equivalent to a sample activity of 4 times the standard error of this difference.The description of each sample is based on information provided by the person submitting the sample to the Laboratory.The work reported forms part of the research programme of the Laboratory and is published by permission of the Director.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
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  • 4
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    National Physical Laboratory Radiocarbon Measurements IV (1966)
    Cambridge University Press
    Details
    Publication Date: 1966-01-01
    Description: The following list comprises measurements made since those reported in NPL III and is complete to the end of November 1965.Ages are relative to A.D. 1950 and are calculated using a half-life of 5568 yr. The measurements, corrected for fractionation (quoted δC13 values are relative to the P.D.B. standard), are referred to 0.950 times the activity of the NBS oxalic acid as contemporary reference standard. The quoted uncertainty is one standard deviation derived from a proper combination of the parameter variances as described in detail in NPL III. These variances are those of the standard and background measurements over a rolling twenty week period, of the sample δC14 and δC13 measurements and of the de Vries effect (assumed to add an additional uncertainty equivalent to a standard deviation of 80 yr). Any uncertainty in the half-life has been excluded so that relative C14 ages may be correctly compared. Absolute age assessments, however, should be made using the accepted best value for the half-life and the appropriate uncertainty then included. If the net sample count rate is less than 4 times the standard error of the difference between the sample and background count rates, a lower limit to the age is reported corresponding to a net sample count rate of 4 times the standard error of this difference.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
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  • 5
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    National Physical Laboratory Radiocarbon Measurements I (1963)
    Cambridge University Press
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    Publication Date: 1963-01-01
    Description: The dating equipment at the National Physical Laboratory was completed by the summer of 1960. A series of calibration and intercomparison measurements was undertaken however, using the NBS oxalic acid reference standard, a modern wood standard (1850 oak tree) and other material before starting routine measurements toward the end of 1961. All results have been obtained using a 4.5 L copper proportional counter filled with CO2 at a constant density corresponding to standard conditions of 22°C and an absolute pressure of 150 cm Hg. The counter is shielded by 8 in. of steel, 6 in. of paraffin wax containing boric oxide, 23 Geiger counters arranged as two independent groups and finally by 1 in. of mercury.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 6
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    IntCal, SHCal, or a Mixed Curve? Choosing a 14C Calibration Curve for Archaeological and Paleoenvironmental Records from Tropical South America (2018)
    Cambridge University Press
    Details
    Publication Date: 2018-03-16
    Description: Because the 14C calibration curves IntCal and SHCal are based on data from temperate latitudes, it remains unclear which curve is more suitable for archaeological and paleoenvironmental records from tropical South America. A review of climate dynamics reveals a significant influx of Northern Hemisphere air masses and moisture over a substantial part of the continent during the South American Summer Monsoon (SASM). Areas affected by the SASM receive unknown amounts of input from both hemispheres, where an argument could be made for either curve. Until localized tree-ring data can resolve this, we suggest using a mixed calibration curve, which accounts for inputs from both hemispheres, as a third calibration option. We present a calibration example from a crucial period of environmental and cultural change in the southern Lake Titicaca. Given our current lack of data on past ∆14C variation in South America, our calibrations and chronologies will likely change in the future. We hope this paper spurs new research into this topic and encourages researchers to make an informed and explicit choice of which curve to use, which is particularly relevant in research on past human–environmental relationships.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
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  • 7
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    National Physical Laboratory Radiocarbon Measurements III (1965)
    Cambridge University Press
    Details
    Publication Date: 1965-01-01
    Description: The following list comprises measurements made since those reported in NPL II and is complete to the end of November 1964.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 8
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    Calculation of Past Dead Carbon Proportion and Variability by the Comparison of AMS 14C and Tims U/TH Ages on Two Holocene Stalagmites (1999)
    Cambridge University Press
    Details
    Publication Date: 1999-01-01
    Description: Twenty-two radiocarbon activity measurements were made by accelerator mass spectrometry (AMS) on 2 Holocene stalagmites from Belgium (Han-stm1b) and from southwest France (Vil-stm1b). Sixteen thermal ionization mass spectrometric (TIMS) U/Th measurements were performed parallel to AMS analyses. The past dead carbon proportion (dcp) due to limestone dissolution and old soil organic matter (SOM) degradation is calculated with U/Th ages, measured calcite 14C activity and atmospheric 14C activity from the dendrochronological calibration curves. Results show that the dcp is different for the 2 stalagmites: between 10,800 and 4780 yr from present dcp=17.5% (σ=2.4; n=10) for Han-stm1b and dcp=9.4% (σ=1.6; n=6) between 3070 and 520 yr for Vil-stm1b. Despite a broad stability of the dcp during the time ranges covered by each sample, a slight dcp increase of about 5.0% is observed in the Han-stm1b sample between 8500 and 5200 yr. This change is synchronous with a calcite δ13C increase, which could be due to variation in limestone dissolution processes possibly linked with a vegetation change. The dcp and δ13C of the 2 studied samples are compared with 5 other modern stalagmites from Europe. Results show that several factors intervene, among them: the vegetation type, and the soil saturation leading to variable dissolution process systems (open/closed). The good correlation (R2=0.98) between the U/Th ages and the calibrated 14C ages corrected with a constant dcp validates the 14C method. However, the dcp error leads to large 14C age errors (i.e. 250–500 yr for the period studied), which is an obstacle for both a high-resolution chronology and the improvement of the 14C calibration curves, at least for the Holocene.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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