Radiocarbon Dating of “Old” Charcoal Using a Wet Oxidation, Stepped-Combustion Procedure

May combine two claims.

The Ceylon graphite blank is at least an order of magnitude lower than 0.7% modern carbon, equivalent to 40 ka, and is 2-10 times lower than commonly reported procedural blanks.

“This blank is at least an order of magnitude lower than the 0.7% modern carbon that would be equivalent to an age of 40 ka, and is 2-10 times lower than commonly reported procedural blanks (Kitagawa et al. 1993;Vogel et al. 1987;Gagnon and Jones 1993).”

• cites Kitagawa et al. 1993 sourcePartly supported

  The “14C Background (or Blank) Levels” section (page not provided) reports a procedural background of 0.112 ± 0.057 percent modern carbon, so the paper supplies an example of a blank for comparison. It measures targets made from Yubari Mine coal, not a Ceylon graphite blank, and does not establish either the claimed order-of-magnitude difference from 0.7% or the 2–10-fold comparison. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites Vogel et al. 1987 sourcePartly supported

  The Contamination During Graphitization section reports anthracite backgrounds of 0.59 ± 0.24% modern, reduced to 0.44 ± 0.13% modern, providing a procedural-background comparison. It does not state the citing paper’s blank value, the 2–10-fold comparison, or that 0.7% modern is equivalent to 40 ka. (LLM, conf=0.82)

  Experimental — accuracy not yet measured
• cites Gagnon and Jones 1993 sourcePartly supported

  The Results report procedural blank values of 0.256% modern carbon for carbonate and 0.762% for organic carbon; the Conclusions equate the latter with about 39 ka, close to the cited 0.7% and 40 ka benchmark. The paper does not report a Ceylon graphite blank or establish that it is an order of magnitude below 0.7% modern carbon or 2–10 times below those procedural blanks. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

May combine two claims.

New Kauri standard results range from 0.16 ± 0.06 pMC to 0.25 ± 0.06 pMC (48-51.7 ka), are internally consistent, and are comparable within error to the accepted range for this standard (0.12-0.21 pMC).

“the results for this standard, which range from 0.16 ± 0.06 pMC to 0.25 ± 0.06 pMC (48-51.7 ka), are internally consistent and comparable within error to the accepted range of values for this standard (0.12-0.21 pMC; Hogg et al. 1995).”

• cites Hogg et al. 1995 sourcePartly supported

  The Laboratory Analysis section gives the same 0.12–0.21 pMC range for the new kauri standard, but proposes applying it provisionally until unresolved measurement problems are addressed; it does not call it an accepted range. The cited paper does not report the citing authors’ 0.16–0.25 pMC results, which are presented as their own findings. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

The quote only partly states this claim.

Additional experiments confirm good agreement with accepted values for the international low-14C New Kauri standard (0.16-0.25 pMC).

“Additional experiments confirm good agreement with accepted values for the international low-14C”

May combine two claims.

The pretreatment, combustion, graphitization, and measurement blank for the procedure, based on analysis of a radiocarbon-dead graphite, is 0.5 ± 0.5 μg C (16, n=14), equivalent to 0.04 ± 0.02 pMC or an age of approximately 60 ka for a 1 mg graphite target.

“The pretreatment, combustion, graphitization, and measurement blank for the procedure, based on the analysis of a”

May combine two claims.

Three separate dates on different aliquots of a charcoal sample from Ngarrabullgan Cave (Queensland, Australia) range from 35.2 to 35.5 ka 14C BP, confirming excellent reproducibility.

“They also confirm excellent reproducibility, with 3 separate dates on different aliquots of a charcoal sample from Ngarrabullgan Cave (Queen- sland, Australia) ranging from 35.2 to 35.5 ka 14C BP.”

May combine two claims.

For ABOX-pretreated Ngarrabullgan samples, consistent and reproducible ages can be obtained from the 850 degrees C fraction, and possibly from the 630 degrees C fraction, but not from the 330 degrees C fraction.

“For ABOX-pretreated samples, the results indicate that consistent, reproducible ages can be obtained from the 850 °C fraction, and possibly from the 630 °C fraction, but not from the 330 °C fraction (Figure 6).”

• AssumptionThe authors state this as an assumption: The delta 13C values for ANU sucrose and charcoal are -11 per mil and -25 per mil, respectively, and a fractionation correction of 14 per mil (equivalent to 110 years) applies to each charcoal sample.
• AssumptionThe authors state this as an assumption: The true blank for natural charcoal lies between the average value for the ABOX pretreated 850 degrees C fraction of Black Mountain charcoal and the Ceylon graphite blank (0.07 ± 0.05 pMC).

May combine two claims.

Calculated blanks above 1 microgram came from the first two Ceylon graphites prepared on the combustion line, and calculated blanks for all later analyses were consistently lower.

“It should also be noted that calculated blanks in excess of 1 µg were from the first 2 Ceylon graphites prepared using the combustion line, and calculated blanks for all subsequent analyses have been consistently lower.”

May combine two claims.

ABOX pretreatment alone does not remove all contamination, because the lower temperature fractions of the step-combusted ABOX pretreated sample have younger 14C ages (37.7 and 51.3 ka) than the 850 degrees C fraction (55.9 ka).

“The ABOX pretreatment alone does not remove all contamination, as the lower temperature fractions of the step-combusted ABOX pretreated sample have younger 14C ages ( 37.7 and 51.3 ka) than the 850 °C fraction (55.9 ka).”

May combine two claims.

No ABA-treated Ngarrabullgan sample was analyzed because the untreated and ABOX-treated results indicate that the sample is virtually uncontaminated.

“No ABA-treated sample was ana- lyzed, as the results from the untreated and ABOX-treated samples indicate that the Ngarrabullgan sample is virtually uncontaminated.”

• AssumptionThe authors state this as an assumption: The delta 13C values for ANU sucrose and charcoal are -11 per mil and -25 per mil, respectively, and a fractionation correction of 14 per mil (equivalent to 110 years) applies to each charcoal sample.
• AssumptionThe authors state this as an assumption: The true blank for natural charcoal lies between the average value for the ABOX pretreated 850 degrees C fraction of Black Mountain charcoal and the Ceylon graphite blank (0.07 ± 0.05 pMC).

May combine two claims.

Neither stepped combustion of an unpretreated sample nor ABA pretreatment followed by stepped combustion is sufficient to remove all contaminants.

“Neither the stepped combustion of an unpretreated sample nor an ABA pretreatment with stepped combustion is sufficient to remove all contaminants.”

May combine two claims.

The Ceylon graphite samples spanned graphite weights from 0.1 to 2.2 mg; the corresponding modern carbon varied from about 0.1 to 1.7 micrograms, with an average of approximately 0.5 ± 0.5 micrograms (1 sigma, n = 14, equivalent to about 60 ka for a 1 mg graphite target).

“The samples spanned a range of graphite weights from 0.1 to 2.2 mg, and the corresponding amount of modern carbon that would account for the observed pMC varies between about 0.1 and 1.7 µg, giving an average of approximately 0.5 ± 0.5 µg (16, n=14, equivalent to -60 ka for a 1 mg graphite target).”

May combine two claims.

Ceylon graphite combusted for 1 and 5 hours gave 14C ages of 60.7 and 62.4 ka BP (0.05 and 0.04 pMC, respectively), which are statistically indistinguishable.

“The resulting 14C ages of 60.7 and 62.4 ka BP (0.05 and 0.04 pMC, respectively) are statistically indistinguishable”

May combine two claims.

All 14 Ceylon graphite measurements are consistent with a mean of 0.04 pMC (chi-square nu = 1.2), and the standard deviation of the data set is 0.02 pMC.

“All 14 measurements are consistent with the mean value of 0.04 pMC (x2v =1.2) and the stan- dard deviation of the data set is 0.02 pMC (Figure 3).”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

In the case of untreated graphite, very little CO2 was produced in the 330 °C or 630 °C combustion steps, so the 3 targets were made from 3 combustions at 850 °C.

“In the case of untreated graphite, very little CO2 was produced in the 330 °C or 630 °C combustion steps, so the 3 targets were made from 3 combustions at 850 °C (850 I, II, III; Table 1).”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

The precombustion of the Fe powder does not appear to affect its catalytic action during the conversion of CO2 to graphite.

“The precombustion of the Fe powder does not appear to affect its catalytic action during the conversion of CO2 to graphite.”

May combine two claims.

Combustions are performed at 330 °C, 630 °C and 850 °C, with a graphite target produced from the CO2 evolved during each combustion step, allowing removal of contamination to be monitored and a high degree of confidence to be placed on the final age.

“Combustions are performed at 3 temperatures (330 °C, 630 °C and 850 °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.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

Combustions and graphitizations are performed in a vacuum line insulated from the atmosphere by a second backing vacuum, which eliminates the risk of atmospheric leakage into the line at any stage.

“Combustions and graphitizations are performed in a vacuum line that is insu- lated from the atmosphere by a second backing vacuum to eliminate the risk of atmospheric leakage into the line at any stage of the procedure.”

May combine two claims.

The proportion of OREC left after oxidation for 72 h depends on the nature of the charcoal and can range widely from 20 to 80%.

“The proportion of OREC left after oxidation for 72 h depends on the nature of the charcoal and can range widely from 20 to 80%.”

• cites Bird and Grocke (1997) sourceNot checked — no full text of the source

May combine two claims.

The Black Mountain charcoal represents a worst case because it is overlain by a vegetated soil profile and has been exposed to infiltrating waters and their organic compounds since sediment deposition and subsequent pedogenesis.

“This sample represents a worst case in that it is overlain by a vegetated soil profile and has been exposed to infiltrating waters and the organic compounds carried by those waters since deposition of the sediments and subsequent pedogenesis.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

A substantial body of dates have been published for the Ngarrabullgan Cave unit, with 19 14C determinations spanning 28.8-34.6 14C ka BP.

“A substantial body of dates have been published for this unit, with 19 14C determinations spanning 28.8-34.614Cka BP (David et al. 1997).”

• cites David et al. 1997 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

An additional step in the graphitization procedure is preoxidation of approximately 0.5 to 1.0 mg iron powder to remove carbonaceous contaminants present in the Fe powder or introduced during sample loading.

“An additional step used in our procedure is a preoxidation of approximately 0.5 to 1.0 mg iron pow- der (Merck; 10 µm) to remove carbonaceous contaminants present in the Fe powder, or introduced during the sample loading procedure.”

Classified as probably not a substantial claim.

Luminescence techniques suggested that humans may have arrived in Australia at 54-60 ka BP (the long chronology).

“whereas the advent of luminescence techniques in the 1980s suggested that humans may have arrived at 54-60 ka BP (the”

• cites Roberts et al. 1994 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Charcoal from Ngarrabullgan Cave has been substantially protected from interaction with infiltrating waters.

“which has been substantially protected from interaction with infiltrating waters (discussed below).”

May combine two claims.

Stepped combustion removes contaminants present in the copper oxide and/or introduced during sample loading, and also removes contamination from samples that ABOX pretreatment did not remove.

“The stepped combustion removes contaminants present in the copper oxide and/or introduced during sample loading, and also removes contamination from samples not removed by the ABOX pretreatment.”

Probably not a substantial claim: may not pass S2 (checkable), S4 (based).

For a 14C date to be considered reliable, the removal of all contamination must be verifiable.

“and the removal of all contamination must be verifiable.”

May combine two claims.

Although total combustion can produce reliable ages on charcoal, the effective limit of the 14C technique will be considerably younger for samples analyzed by total combustion.

“It therefore seems that although total combustion can produce reliable ages on charcoal, the effective limit of the 14C technique will be considerably younger for samples that are analyzed by total combustion.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The few 14C atoms observed may already have been present in the Ceylon graphite itself or may have been added during target pressing.

“suggesting that the few '4C atoms observed may already be present in the Ceylon graphite itself or were possibly added during target pressing.”

May combine two claims.

Detecting sample contamination and verifying the reliability of the ages produced also become more difficult as the age of the sample increases.

“Detecting sample contamination and verifying the reliability of the ages produced also become more difficult as the age of the sample increases.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Other procedures used in this study, including preoxidation of iron powder, molecular sieves, storage in vacuo, and a vacuum-backed extraction line, may also contribute to overall blank reduction, but more importantly guard against random contamination of individual samples.

“The other procedures used in this study, including preoxidation of the iron powder, use of molecular sieves, storage of samples in vacuo and the use of a vacuum-backed extraction line, may also con- tribute to overall blank reduction, but more importantly, guard against random contamination of individual samples.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The completeness of the graphitization for the 850 °C fraction can be checked by measuring the total pressure and CO2 pressure at the end of the reaction period.

“The completeness of the graphitization for the 850 °C (C) fraction can then be checked by measuring the total pressure, and CO2 pressure at the end of the reaction period.”

Probably not a substantial claim: may not pass S4 (based). May combine two claims.

The so-called radiocarbon barrier and the difficulty of ensuring that ages are reliable at <1% modern carbon levels has limited research in many disciplines.

“The so-called”

Probably not a substantial claim: may not pass S4 (based).

Significant contamination of samples from atmospheric leakage into the extraction line can potentially occur during combustion of the sample to CO2 or during graphitization.

“Significant contamination of samples from atmospheric leakage into the extraction line can poten- tially occur during the combustion of the sample to C02, or during graphitization.”

Classified as probably not a substantial claim.

Early 14C determinations suggested that humans first arrived in Australia about 40 ka BP (the short chronology).

“Early 14C determinations suggested that humans first arrived about 40 ka BP (the”

• cites Allen and Holdaway 1995 sourceNot checked — no full text of the source
• cites O'Connell and Allen 1998Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

A graphite target is generally made from the CO2 produced during each combustion step (330 °C, 630 °C, and 850 °C), so that contaminants remaining after pretreatment are expected to be combusted in the 330 °C step and the reliability of the 14C age can be assessed by the coherence of results from the 630 °C and 850 °C steps.

“A graphite target is generally made from the CO2 produced during each combustion step (i.e., 330 °C, 630 °C, and 850 °C).In this way it is expected that any contaminants remaining after the sample pretreatment will be combusted in the 330 °C step, and that the reliability of the 14C age can be assessed by the coherence of the results from the 630 °C and 850 °C steps.”

• AssumptionRests on an assumption: Oxidation removes less resistant phases first, working progressively from the outside to the interior of the particles.

Probably not a substantial claim: may not pass S3 (load-bearing).

The 14C-dead charcoal from the Coulter Pedoderm is likely to be at least of last interglacial age.

“The unit is thought to have undergone pedogenesis during a period of climatic stability similar to the present, and is likely to be at least of last interglacial age.”

Classified as probably not a substantial claim. May combine two claims.

Many laboratories will only quote 14C ages to about 40 ka BP, with ages greater than this generally considered infinite or indistinguishable from procedural blanks.

“In practice this means that many laboratories will only quote 14C ages to about 40 ka BP (thousands of '4C years Before Present), with ages greater than this generally considered to be”

Classified as probably not a substantial claim. May combine two claims.

All pretreatment steps are carried out in either a laminar flow cabinet, a HEPA-filtered clean lab, or capped vials, with all vessels and implements precleaned by combustion or by washing with hot dichromate/sulfuric acid solution.

“All pretreatment steps are carried out in either a laminated flow cabinet, a HEPA-filtered clean lab, or capped vials, with all vessels and implements precleaned either by combustion overnight at 550 °C (Pyrex®) or 850 °C (quartz), or by washing with a hot solution of O.1 M K2Cr2O7 in a 2M solution of H2SO4.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

In the AB-treated samples, there is a suggestion that ages become younger for the 850 degrees C fraction, possibly owing to formation of Na2CO3, which has a decarbonation temperature of 851 degrees C.

“However, in the case of the AB-treated samples, there is a suggestion that the ages become younger for the 850 °C fraction, possibly owing to formation of Na2CO3, which has a decarbonation temperature of 851 °C.”

• AssumptionThe authors state this as an assumption: The delta 13C values for ANU sucrose and charcoal are -11 per mil and -25 per mil, respectively, and a fractionation correction of 14 per mil (equivalent to 110 years) applies to each charcoal sample.
• AssumptionThe authors state this as an assumption: The true blank for natural charcoal lies between the average value for the ABOX pretreated 850 degrees C fraction of Black Mountain charcoal and the Ceylon graphite blank (0.07 ± 0.05 pMC).

Classified as probably not a substantial claim.

The production of reliable 14C dates on old archaeological charcoal samples can assist in resolving the discrepancy between the short and long chronologies.

“The production of reliable 14C dates on old archaeological charcoal samples can assist in this respect.”

Probably not a substantial claim: may not pass S2 (checkable).

Resolution of the discrepancy between the short and long chronologies is important for a refined understanding of early human migration and colonization of Australia and the ecological effects accompanying human colonization.

“Resolution of this discrepancy is important for a refined understanding of early human migration and colonization of the continent as well as of the ecological effects accompanying human colonization.”

May combine two claims.

The buried paleosol has been subject to infiltrating waters carrying organic compounds from the vegetated surface, and interactions between the charcoal and groundwater are evidenced by fine gypsum crystals deposited on the surface of some fragments.

“The buried paleosol has been subject to infiltrating waters carrying organic compounds from the vegetated surface.Interactions between the charcoal and groundwater are evidenced by fine gypsum crystals deposited on the surface of some fragments.”

Probably not a substantial claim: may not pass S4 (based).

For a 14C date to be considered reliable, the ages must be reproducible within the stated error bounds.

“In addition, the ages must be reproducible within the stated error bounds”