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Radiocarbon Dating of "Old" Charcoal Using a Wet Oxidation, Stepped-Combustion Procedure
Issue Date
1999-01-01Keywords
combustionwet methods
temperature
oxidation
accelerator mass spectra
graphitization
mass spectra
spectra
Pleistocene
sample preparation
Cenozoic
charcoal
Quaternary
C 14
carbon
dates
isotopes
radioactive isotopes
carbon dioxide
absolute age
Metadata
Show full item recordCitation
Bird, M. I., Ayliffe, L. K., Fifield, L. K., Turney, C. S. M., Cresswell, R. G., Barrows, T. T., & David, B. (1999). Radiocarbon dating of “old” charcoal using a wet oxidation, stepped-combustion procedure. Radiocarbon, 41(2), 127-140.Journal
RadiocarbonAdditional Links
http://radiocarbon.webhost.uits.arizona.edu/Abstract
We present results that validate a new wet oxidation, stepped-combustion procedure for dating "old" charcoal samples. An acid-base-wet oxidation (ABOX) pretreatment procedure has been developed that is used in place of the conventional acid-base-acid (ABA) pretreatment. Combustions and graphitizations are performed in a vacuum line that is insulated from the atmosphere by a second backing vacuum to eliminate the risk of atmospheric leakage into the line at any stage of the procedure. Combustions are performed at 3 temperatures (330 degrees C, 630 degrees C and 850 degrees C) with a graphite target produced from the CO2 evolved during each combustion step. In this way, the removal of any contamination can be monitored, and a high degree of confidence can be placed on the final age. The pretreatment, combustion, graphitization, and measurement blank for the procedure, based on the analysis of a "radiocarbon-dead" graphite, is 0.5 +/0.5 micrograms C (1sigma, n = 14), equivalent to 0.04 +/0.02 pMC or an "age" of approximately 60 ka for a 1 mg graphite target. Analyses of a "radiocarbon-dead" natural charcoal after ABOX pretreatment and stepped combustion suggest that the total blank (including contamination not removed by pretreatment) may be higher than for graphite, ranging up to 0.10 +/0.02 pMC. Additional experiments confirm good agreement with accepted values for the international low14C "New Kauri" standard (0.16-0.25 pMC). They also confirm excellent reproducibility, with 3 separate dates on different aliquots of a charcoal sample from Ngarrabullgan Cave (Queensland, Australia) ranging from 35.2 to 35.5 ka 14C BP. It is also demonstrated that the ABOX pretreatment, in conjunction with the new vacuum line described here, is able to remove contamination not removed by the conventional ABA pretreatment, suggesting that the technique can be used to produce reliable 14C dates on charcoal up to at least 50 ka.Type
Articletext
Language
enISSN
0033-8222ae974a485f413a2113503eed53cd6c53
10.1017/S0033822200019482