CoChat
Sign Up
Cited by 3Archaeology and ancient environmental studiesGeology and Paleoclimatology ResearchPleistocene-Era Hominins and Archaeology

Misunderstandings Concerning the Significance of AMS Background 14C Measurements

Open access
Taylor, R E, Southon, John R, Santos, Guaciara M·2018·Radiocarbon
DOI 10.1017/rdc.2018.15
Open this paper in CoChat — free accountOpen PDF

Abstract

We consider one misconception of those who currently reject the general validity of radiocarbon (14 C) age determinations older than, at most, 10,000 BP. There is an allegation that the presence of 14 C reported by accelerator mass spectrometry (AMS) laboratories in their measurements of 14 C infinite age (>100,000 years) organics used to define background levels, support their point of view. This article has been written for a general audience, primarily for those who have questions about the validity of these arguments. However, they may not be familiar with the literature relevant to providing a clear response to the claims of these individuals. We conclude that, in our view, of all of the possible explanations for the reports of the presence of 14 C in these background samples, the least probable explanation has been advanced by those rejecting the validity of the 14 C time scale in excess of, at most, 10,000 BP.

AI snapshot

Written from the paper’s full text.

TL;DR

This review argues that claims rejecting radiocarbon ages older than roughly 10,000 BP misunderstand AMS background measurements. It concludes that ¹⁴C signals in infinite-age samples are most plausibly explained by sample and instrument contamination, not by residual cosmogenic ¹⁴C.

Key findings

The paper identifies 16 possible sources of ¹⁴C signal in AMS measurements of infinite-age samples, dividing them into sample-based sources (12) and instrument-based sources (4), and argues these are more likely than residual cosmogenic ¹⁴C.

  • Table 4 shows that adding about 47 ppm modern carbon or 24 ppm 1963 bomb ¹⁴C to an infinite-age sample would produce an apparent age of ~80,000 BP; ~163 ppm modern or ~82 ppm bomb ¹⁴C would produce ~70,000 BP; ~568 ppm modern or ~284 ppm bomb ¹⁴C would produce ~60,000 BP; and ~1975 ppm modern or ~988 ppm bomb ¹⁴C would produce ~50,000 BP.
  • Figure 6 reports that for 1140 background samples of calcite, wood, and coal, measured ¹⁴C stayed near ~0.2 pMC (~50,000 years) down to about 0.3 mg of synthesized graphite; below that, apparent ages fell to ~30,000 years at ~0.05 mg and ~20,000 years at ~0.01 mg.
  • Table 5 gives examples from two AMS laboratories: at UC Irvine, an unprocessed diamond measured 0.005 ± 0.01 pMC (~80.0 ± 1.1 ka), while unprocessed geologic graphite measured 0.035 ± 0.003 pMC (~64.0 ± 0.07 ka); at the University of Washington, an aluminum target gave ≥90.0 ka and unprocessed geologic graphite gave 69.03 ± 1.7 ka under argon and 63.80 ± 1.1 ka in air.

Methods

This is a review and argument paper aimed at non-specialists, synthesizing known AMS operating principles, sample pretreatment and conversion procedures, and background terminology.

  • It uses illustrative data from two AMS laboratories—the University of Washington and the UC Irvine KCCAMS facility—including previously published results and four measurements newly reported for this paper.
  • The main analysis is conceptual: it categorizes background sources, compares sample-based versus instrument-based contamination, and uses tables and figures to show how trace modern or bomb ¹⁴C and small graphite sample sizes affect apparent ages.

Limitations

The authors state that background sources and magnitudes are unique to each AMS system and can change over time, so their conclusions should not be generalized to all AMS instruments. They also concede that residual cosmogenic ¹⁴C cannot be totally excluded as an explanation, though they consider it the least likely.

  • Evident from the text: the paper is an interpretive review with illustrative examples from two laboratories rather than a systematic experimental isolation of all 16 listed sources, so it does not quantify each source’s relative contribution.
  • Evident from the text: the argument is written for a general audience and restates background material in more detail than standard research papers, which limits its presentation of new primary evidence.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1017/rdc.2018.15

Cites

39 of 39 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

11 of 19 cited sources checked · 5 supported · 2 flagged · accuracy not yet measured

  • Premisecitation

    If statistical analysis cannot distinguish the mean 14C/12C ratio of an unknown sample from that of an infinite-age background sample at a defined confidence level, an infinite 14C age is calculated for the unknown sample.

    “If it is determined that it is not possible to distinguish, at some defined measure of statistical confidence, the mean 14 C/ 12 C ratio exhibited by the unknown age sample and the mean 14 C/ 12 C ratio of the infinite 14 C age background sample, an infinite 14 C age would be calculated for this unknown age sample.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites Taylor and Bar-Yosef (2014:127-129)

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

    • cites Stuiver and Polach (1977) source

      Section 10, “Reporting of Ages Close to Background” (page not provided), says that when sample activity is not distinguishable from background, that fact should be stated. For low sample activity, it recommends reporting a minimum age as “>x,” not calculating an infinite age. (LLM, conf=0.88)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
  • Premisecitation

    The current generation of AMS instruments used for routine natural-level 14C measurements are, with few exceptions, electrostatic accelerators.

    “Although the first AMS-based 14 C measurements were obtained on a cyclotron particle accelerator (Muller 1977), the current generation of AMS instruments used for routine natural level 14 C measurements, are, with a few exceptions, electrostatic accelerators (Tuniz et al. 1998;Tuniz and Norton 2008).”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites Muller 1977 source

      Muller (1977) is cited for the first clause of the sentence, not for its statement about current electrostatic AMS instruments. In the Radiocarbon Dating section (page unavailable), Muller says cyclotron-based ¹⁴C dating appeared possible but that evaluating its sensitivity awaited further experimental development; the paper does not report the claimed first ¹⁴C measurements. (LLM, conf=0.86)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
    • cites Tuniz et al. 1998

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

    • cites Tuniz and Norton 2008 source
  • Premisecitation

    For samples close to background levels, it was not possible to protect them from traces of atmospheric contamination during periods of exposure to ambient conditions, even for relatively short time intervals.

    “This study determined that for samples close to background levels, it was not possible to protect these samples from traces of atmospheric contamination during the periods when they are exposed to ambient conditions, even for relatively short time intervals.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Paul et al. 2016 source
  • Premisecitation

    At its 1963 maximum, bomb 14C nearly doubled the 14C content of the atmosphere and biosphere.

    “The maximum amount of this artificial 14 C was present in the atmosphere and thus was also contained in living terrestrial organics in 1963 in amounts that resulted in almost doubling the amount of atmospheric and biospheric 14 C (Fairhall and Young 1970;Stuiver and Braziunas 1998).”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites Fairhall and Young 1970 source
    • cites Stuiver and Braziunas 1998 source

      The Introduction discusses atmospheric radiocarbon measured in tree rings, and the Temporal Regional Δ14C Change section discusses regional differences and fossil-fuel effects. Neither states that bomb-produced 14C peaked in 1963 or nearly doubled atmospheric and biospheric 14C; searches for 1963, bomb-produced radiocarbon, and nuclear testing found no passage addressing that claim. (LLM, conf=0.75)

      Experimental — accuracy not yet measured
  • Premisecitation

    The cause of the increasing 14C background values as a function of declining amounts of infinite age material in the synthesized graphite is very similar amounts of micro-contamination added to all synthesized graphite samples during the combustion/acidification and/or graphitization process.

    “The cause of these effects has been demonstrated to be due to the very similar amounts of micro-contamination being added to all synthesized graphite samples during the combustion/acidification and/or graphitization process that we have previously described (Vogel et al. 1987;Kirner et al. 1995;Brown and Southon 1997).”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites Vogel et al. 1987 source
    • cites Kirner et al. 1995 source

      In “Sources and Levels of Contamination” (page not provided), the paper reports that radiocarbon background rises as graphite sample weight falls and describes a model in which a roughly constant amount of contamination is added during combustion and/or graphitization. Its conclusion says the authors’ data are *consistent with* that model, not that they demonstrated it to be the cause in all synthesized graphite samples. The citing sentence overstates the certainty and scope of the finding. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites Brown and Southon 1997 source
  • Classified as probably not a substantial claim. 24
  • May combine two claims. 15

  • Classified as probably not a substantial claim.

    Premisecitation

    Contamination of AMS sample targets by modern carbon is inevitable.

    “contamination on AMS sample targets by modern carbon is inevitable”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Paul et al. 2016 source

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

    Premisereasoning

    Because fossil-fuel burning and bomb 14C have altered contemporary 14C levels, the 0 BP modern level is defined by specially prepared standards rather than by living organics.

    “Primarily because of these two human-caused effects on contemporary 14 C levels,”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Stuiver and Polach (1977) source

      Section 1 (page unavailable) defines the radiocarbon reference value using NBS oxalic acid, and section 3 says AD 1950 is 0 BP and that conventional ages use oxalic acid as a standard. The passages do not say that fossil-fuel burning and bomb-produced 14C are the reasons for using that standard instead of living organics. (LLM, conf=0.84)

      Experimental — accuracy not yet measured

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

    Premisecitation

    The data in Figures 4A and 4B are typical of current measurements from the KCCAMS AMS system at UC Irvine.

    “The data illustrated in these plots are typical of that currently being obtained on the AMS system described in Figure 1 and Table 1 operating at the KCCAMS laboratory at the University of California, Irvine (Southon et al. 2004;Santos et al. 2007).”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites Southon et al. 2004 source
    • cites Santos et al. 2007

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

  • Classified as probably not a substantial claim.

    Study design and conductcitation

    Conventional 14C ages require normalization of 14C/12C ratios using δ13C values to a common δ13C value.

    “Stuiver and Misunderstanding AMS Background 14 C Measurements 731 Polach (1977) and Taylor and Bar-Yosef (2014:26-27;124-127) explicitly define conventional 14 C ages and provide an explanation of how and why 14 C/ 12 C ratios are adjusted using δ 13 C values so that all such 14 C age determinations are normalized to a common δ 13 C value.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites Stuiver and Polach (1977) source
    • cites Taylor and Bar-Yosef (2014:26-27;124-127)

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

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

    Findingcitation

    Figure 6 presents measurements providing direct information about the effects of changing measured 14C ages in 1140 samples of three assumed infinite age materials (calcite, wood, and coal) as a function of the amount of synthetic graphitic carbon produced in the graphitization process used at the UCI KCCAMS laboratory.

    “Figure 6 presents the results of a series of measurements that provides direct information about the effects of a change in measured 14 C ages exhibited in 1140 samples of 3 types of assumed infinite 14 C age materials (calcite, wood, and coal) as a function of the amount of synthetic graphitic carbon produced in the graphitization process used at the UCI AMS (KCCAMS) laboratory”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites Santos et al. 2007

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

    • cites Santos et al. 2010 source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • The authors state this as an assumption: The calcite and coal samples derive from Mesozoic age deposits making them at least 60 million years old, and the wood was collected from a stratigraphic context associated with oxygen isotope stage 5a or 5c indicating an age of at least 80,000 years.

  • May combine two claims.

    Findingreasoning

    For samples of infinite or near-infinite 14C age, cross-talk effects are measurable and contribute to background levels.

    “However, for samples of infinite or near infinite 14 C age, the effects are measureable and contribute to the level of the backgrounds exhibited in such samples.”
    Quote in the paperSubstantial claim

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

    Findingown data

    Table 1 Part A shows varying apparent 14C ages of three compounds from Kauri wood, while Part B shows increasing finite ages depending on pretreatment method.

    “Table 1, Part A, illustrates the varying apparent 14 C ages of three compounds isolated from this sample, while Part B illustrates the increasing finite ages that are obtained depending on what types of pretreatment methodologies are employed.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The Kauri wood samples in Table 1 are older than 65,000 years.

  • May combine two claims.

    Findingreasoning

    While 14C memory effects have been reduced to extremely low levels in the majority of ion sources, sample crosstalk effects cannot be totally eliminated, and a small number of 14C ions from previous samples can contribute to the 14C signal detected when subsequent samples are measured.

    “While 14 C memory effects have been reduced to extremely low levels in the majority of ion sources, such sample crosstalk effects cannot be totally eliminated and a small numbers of 14 C ions from previous samples can contribute to the 14 C signal detected when subsequent samples are measured.”
    Quote in the paperSubstantial claim

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

    Findingreasoning

    In Figure 4A, the unknown-age sample has about half the 14C counts of the modern reference standard, implying an age of about one 14C half-life.

    “By simple visual inspection of the data plotted in Figure 4A, we note that the number of ions which are primarily 14 C ions detected for the unknown age sample is approximately half of that recorded for the modern reference standard.We would then provisionally conclude that the age of this sample is about one 14 C half-life old.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Within the energy window marked in Figure 4, over 99% of detected ions are mass 14, and over 99% of those mass 14 ions are 14C.

    “More than 99% of the ions detected in the energy window defined by the two vertical dotted lines are mass 14 ions and, of these mass 14 ions, more than 99% are 14 C ions.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Infinite age graphite samples of about 0.05 mg exhibit an apparent age of about 30,000 years, and at about 0.01 mg the apparent ages are about 20,000 years.

    “We see, for example, that infinite age graphite samples of ~0.05 mg (= 50 μg) exhibits an apparent age of ~30,000 years and at ~0.01 mg (= 10 μg) the apparent ages of these 14 C infinite age samples is ~20,000 years.”
    Quote in the paperSubstantial claim

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

    Premisenone given

    Fractionation can be introduced during AMS measurement because of particle accelerator operating characteristics.

    “Fractionation can also be introduced during an AMS-based measurement of a sample due to several aspects of the operating characteristics of a particle accelerator.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Because 14C's half-life is about 5700 years, when natural 14C levels indicate ages of 50,000 years or more, adding only a few tenths of a percent of exogenous modern carbon can add thousands to tens of thousands of years, creating pseudo-finite ages.

    “Given the approximately 5700 year half-life of 14 C, a plot of the 14 C decay curve reveals that when natural 14 C levels are at or below that which would indicate an age 50,000 years or older only a few tenths of a percent addition of exogenous”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisenone given

    After 14N removal, other mass-14 species remain, including carbon-containing molecules like 13CH− and 12CH2− and mass-14 molecules of elements such as lithium.

    “However, even with the elimination of almost all 14 N ions, several other types of mass 14 ions will remain.There will be mass 14 molecules which include carbon atoms, such as 13 CH -and 12 CH 2 -, as well as molecules of other elements, such as lithium, exhibiting mass 14 signatures.”
    Quote in the paperSubstantial claim

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

    Premisereasoning

    Both sample-based and instrument-based background sources have multiple origins that can operate differently depending on sample processing and instrument configuration across AMS laboratories and times.

    “Both of these background types have multiple sources that can be operating in unique ways depending on sample processing protocols and instrument component configurations employed in different AMS laboratories at different times.”
    Quote in the paperNot a substantial claim

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

    Premisenone given

    Most AMS systems routinely measuring 14C use an ion source that produces negative ions by adding electrons.

    “In most AMS systems currently measuring 14 C on a routine basis, the ion source is designed to add electrons which yields negatively charged ions.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given

    Background contributions from the listed factors vary in magnitude among AMS instruments, but the causes of most reported background may be similar across systems.

    “combination contribute their background signals in AMS systems will be expressed in different levels in different instruments, although it would appear that the causes of the largest percentage of backgrounds which are reported may be very similar.”
    Quote in the paperNot a substantial claim

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

    Premisenone given

    The remaining four potential causes of pseudo-cosmogenetic 14C signals in AMS systems listed in Table 2 when measuring infinite age samples are instrument-based.

    “The remaining four potential causes of pseudo-cosmogenetic 14 C signals in AMS systems listed in Table 2 when measuring infinite age samples are instrumentbased.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationreasoning

    Data from electrostatic AMS instruments have been most often cited and misunderstood by current critics.

    “It is data from these types of AMS instruments which have been most often cited and misunderstood by current critics.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisereasoning

    Cross talk in AMS ion sources occurs when carbon from one sample is transferred to another sample or to ion-source surfaces during measurement.

    “A design feature of most ion sources contributes to the possibility of what is informally termed”
    Quote in the paperSubstantial claim

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

    Premisereasoning

    AMS background sources can be grouped into sample-based and instrument-based categories.

    “Reflecting the two categories already identified in a previous section, the potential sources of AMS system backgrounds have been divided into two types: sample based and instrument based.”
    Quote in the paperNot a substantial claim

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

    Interpretationnone given

    Not all listed contamination sources make equal contributions to the size of measured 14C backgrounds across AMS systems.

    “Also, we should emphasize that we do not suggest that each potential source of contamination listed in Table 3 contributes equally to the magnitude of the measured 14 C backgrounds in different AMS systems.That certainly would not be correct.”
    Quote in the paperNot a substantial claim

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

    Premisenone given

    The first potential source of machine background listed in Table 2 results from an instrument anomaly in which mass 14 ions are produced at some point within the beam line itself.

    “The first potential source of machine background listed in Table 2 results from an instrument anomaly in which mass 14 ions are produced at some point within the beam line itself.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    Nitrogen either does not form a negative ion or any negative 14N ion has a lifetime much shorter than the few-microsecond transit time from ion source to detector.

    “That circumstance is that nitrogen either does not form a negative ion or, if a negative 14 N ion is actually formed, it has a lifetime much shorter than the few microseconds (where 1 microsecond = 1/10,000 of a second) transit time of particles traveling from the exit point of an ion source to a detector at the opposite end of the beam line of the spectrometer [Figure 1, Component E(2)].”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Design changes and high vacuums maintained in the ion source significantly reduce the probability that 14C ions from a sample undergoing measurement will be contaminated by 14C ions produced by a previously ionized sample, but do not totally eliminate it.

    “Design changes and the high vacuums maintained in the ion source significantly reduces the probability that 14 C ions from a sample undergoing measurement will be contaminated by 14 C ions which had been produced by a previously ionized sample.However, it will not totally eliminate them.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisereasoning

    In most AMS systems, a gas or foil stripper strips electrons from negative ions, changing them to positive ions and breaking molecules apart, which almost completely removes mass-14 molecular interferences.

    “These mass 14 molecular species are almost entirely eliminated because of a major design feature in most AMS systems.”
    • Also stated in: § Misunderstanding AMS Background 14 C Measurements 737 · plain
      “The important effect of this”
    Quote in the paperSubstantial claim

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

    Premisenone given

    AMS 14C backgrounds have two major sources: sample-based and instrument-based.

    “There are two major sources of 14 C backgrounds registered in AMS systems: sample based and instrument based.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    The specific sources and magnitudes of 14C backgrounds are unique to each AMS system and may change over time in the same instrument.

    “The specific sources and magnitudes of 14 C backgrounds are unique to each AMS system and may change over time in the same instrument.”
    Quote in the paperSubstantial claim

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

    Premisereasoning

    Bomb 14C mainly refers to artificial 14C from atmospheric thermonuclear weapons tests by the United States and Soviet Union before the 1963 Partial Test Ban Treaty.

    “The term”
    Quote in the paperNot a substantial claim

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

    Premisenone given

    Machine backgrounds result from pulses recorded in the AMS detector electronic circuitry that ordinarily indicate a 14C ion not derived from an infinite age carbon sample converted to CO2, synthesized to graphitic carbon, pressed into a sample holder, and placed in the ion source.

    “These types of backgrounds are the result of pulses recorded in the AMS system detector electronic circuitry which ordinarily indicates the presence of a 14 C ion which has not been derived from the presence of 14 C derived from an infinite age carbon sample converted to CO 2 , synthesized to graphic carbon, pressed into a sample holder which is then placed the ion source of an AMS instrument.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    A negative ion source removes nearly all 14N from the outgoing particle beam, though a small amount remains.

    “Thus when a negative ion source is employed in an AMS system, the result is that 14 N is almost completely (but not entirely) eliminated from the beam of particles exiting the ion source.”
    Quote in the paperSubstantial claim

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

    Interpretationreasoning

    The critics' lack of knowledge leads them to make erroneous statements about AMS-based 14C measurements on infinite-age samples.

    “Specifically, there are four areas where this lack of knowledge has led to erroneous statements when they comment on AMS-based 14 C measurements on various types of infinite age samples.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Infinite-age samples have not been contaminated by younger organics.

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

    Interpretationnone given

    The cause of the confusion of those who dispute the validity of pre-Holocene 14C age determinations is their lack of knowledge of the operating characteristics of AMS technology as applied to measurement of natural 14C concentrations.

    “We have suggested that the cause of the confusion of these individuals is their lack of knowledge of the operating characteristics of the technology used in AMS systems as applied to the measurement of natural 14 C concentrations.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: The typical ages of the organic samples used for these measurements are assumed, based on paleontological and/or geological criteria, to be greatly in excess of 100,000 years, and most of these samples, such as natural diamonds, are much older than several hundred million years.

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

    Interpretationreasoning

    It would not be appropriate to generalize for all currently routinely operating AMS instruments because different AMS systems use somewhat different sample preparation protocols and instrumental configurations.

    “Since different AMS systems make 14 C measurements using somewhat different sample preparation protocols and instrumental configurations, we submit that it would not be appropriate to generalize for all currently routinely operating AMS instruments.”
    Quote in the paperNot a substantial claim

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

    Premisenone given

    The majority of AMS systems convert CO2 produced from sample combustions or acidifications into a form of synthesized graphitic carbon.

    “We have previously noted that the majority of AMS systems convert CO 2 produced from sample combustions or acidifications into a form of synthesized graphitic carbon.”
    Quote in the paperNot a substantial claim

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

    Interpretationnone given

    An interpretation that these measurements indicate the presence of actual residual cosmogenic 14C cannot be totally excluded.

    “Obviously, an interpretation that these measurements indicate the presence of actual residual cosmogenic 14 C cannot be totally excluded.”
    Quote in the paperNot a substantial claim
36 of 36

  • The authors state this as an assumption.

    Infinite-age samples have not been contaminated by younger organics.

    “In making this statement, we assume, of course, that any infinite age sample has not been contaminated by younger organics.”

  • The authors state this as an assumption.

    The Kauri wood samples in Table 1 are older than 65,000 years.

    “The Kauri wood samples in Table 1 are assumed to be 14 C”

  • The paper relies on this without support.

    Even after efforts to make copper oxide and silver carbon-free, small amounts of foreign carbon remain in these reagents.

    “Even though there is much focus on obtaining and processing materials such as copper oxide and silver used in the conversion of a sample into CO 2 to be carbon free, minute traces of exogenous carbon inevitably remain in these reactants.”

  • The paper relies on this without support.

    The main parts of the KCCAMS AMS system are broadly typical of compact AMS systems.

    “The major components it incorporates are generally representative of those which are included in what is typically referred to as a”

  • The authors state this as an assumption.

    The calcite and coal samples derive from Mesozoic age deposits making them at least 60 million years old, and the wood was collected from a stratigraphic context associated with oxygen isotope stage 5a or 5c indicating an age of at least 80,000 years.

    “It is assumed that the calcite and coal samples derive from Mesozoic age deposits making these samples at least 60 million years old while the wood was collected from a stratigraphic context associated with oxygen isotope stage 5a or 5c indicating an age of at least 80,000 years.”

  • The authors state this as an assumption.

    The typical ages of the organic samples used for these measurements are assumed, based on paleontological and/or geological criteria, to be greatly in excess of 100,000 years, and most of these samples, such as natural diamonds, are much older than several hundred million years.

    “The typical ages of the organic samples used for these measurements are assumed, based on well-documented paleontological and/or geological criteria, to be greatly in excess of 100,000 years and most of these samples, such as natural diamonds, are much older than several hundred million years.”

  • The authors state this as an assumption.

    Infinite age samples are assumed to contain no 14C.

    “in a sample of infinite age which is assumed to contain no 14 C”
7 of 7

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Background-source list is assigned the wrong table number

    Minor

    The statement points to Table 2 for the potential background sources, but the list of those sources is labeled Table 3.

  • Microgram quantity is labeled with a length unit

    Minor

    The parenthetical unit for 300 micrograms is printed as μm, whereas the paper elsewhere uses μg for micrograms.

  • Kauri sample location differs between text and table

    Minor

    The text places the Kauri wood samples in New Zealand, while Table 1 identifies them as coming from New South Wales, Australia.

  • Figure 1 points to the wrong component table

    Minor

    The Figure 1 caption directs readers to Table 1 for components A through E, but the component list is labeled Table 2; Table 1 contains Kauri wood measurements.

4 of 4

Cites

Flagged first, then by citations

Research works printed but not linked: 3

  1. Santos GM . 2011. The good and the bad of small-scale 14C-AMS sample preparation and analysis. Paper presented at the International Workshop on Small Scale Radiocarbon Analysis, 13–16 September 2011, Laboratory of Ion Beam Physics, ETH Zürich, Switzerland. Available at http://www.ams.ethz.ch/workshop.
  2. Freeman S . 2017. Positive-ion mass spectrometry progress. Paper presented at the 14th International Conference on Accelerator Mass Spectrometry, Ottawa, Canada, August 12–20, 2017.
  3. Paul M . 2017. Positive-ion mass spectrometry progress. Paper presented at the 14th International Conference on Accelerator Mass Spectrometry, Ottawa, Canada, August 12–20, 2017.

Cited by

Sorted by citations

Related

Authors
Taylor, R. E., Southon, J. R., & Santos, G. M.
Affiliations
  • University of California, Riverside (US)
  • University of California, Irvine (US)
Corresponding author
Taylor, R E
ORCID
Venue
Radiocarbon
Publisher
Cambridge University Press (CUP)
Published
2018-05-30
Volume
60
Issue
3
Pages
727-749
ISSN
  • 0033-8222 (ISSN-L)
  • 1945-5755
DOI
10.1017/rdc.2018.15
OpenAlex
W2807579313
Cited by
3
References
35
Citations by year
2025: 1 · 2022: 1 · 2021: 1
FWCI
0.32
Type
journal article
Language
en
Open access
Licence
www.cambridge.org/core/terms (unspecified)
Locations
  • Radiocarbon (publishedVersion)
  • eScholarship (California Digital Library) (submittedVersion)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Archaeology and ancient environmental studies
  • Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Geology and Paleoclimatology Research
  • Social Sciences › Anthropology › Pleistocene-Era Hominins and Archaeology
Keywords
accelerator mass spectrometry, radiocarbon dating, radiocarbon contamination, radiocarbon calibration

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read under definition version 3 (extract-v3) on 2026-09-27.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-09-27.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review